Agricultural and Food Science 324 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Vol. 15 (2006): 324–339. © Agricultural and Food Science Manuscript received March 2006 Performance, carcass quality, and gastric   alterations in fattening pigs fed additives   containing formic acid either coated with sorbate   or mixed with lactic acid Kirsi Partanen, Maija Karhapää, and Hilkka Siljander-Rasi MTT Agrifood Research Finland, Animal Production Research, Pork and Poultry Production, Tervamäentie 179, FI-05840 Hyvinkää, Finland, e-mail: kirsi.partanen@mtt.fi Erkki Virtanen� Kemira GrowHow Ltd, Mechelininkatu 1a, PO Box 900, FI-00181 Helsinki, Finland Bernt Nilsson Kemira GrowHow Ltd, Industrigatan 70, PO Box 902, SE-251 09 Helsingborg, Sweden, e-mail: bernt.nilsson@kemira-growhow.com The growth-promoting effects of two dietary acidifiers based on formic acid were studied with 320 fatten- ing pigs from ca 2� kg to ca �05 kg of body weight. The sorbate-coated formic acid contained formic acid and ammonium formate which were absorbed in diatomaceous earth and coated with potassium sorbate. The investigated liquid blend contained formic and lactic acids as the major components. These acidifiers were added to grower and finisher diets at levels of 3, 6, and �2 g kg-� of feed. The grower and finisher diets in the negative control treatment contained no growth promoters, but the grower diet in the positive control treatment was supplemented with avilamycin (40 mg kg-�). The investigated acidifiers did not influence the performance of growing pigs (P > 0.05). In finishing pigs, all additions of the sorbate-coated formic acid improved daily weight gain compared to the negative control (P < 0.05), whereas the feed conversion ratio was improved by additions of 3 and �2 g kg-� of the acidifier. During the total fattening period, 6 and �2 g kg-� of the sorbate-coated formic acid improved daily weight gain compared to the situation in the negative control (P < 0.05), and �2 g kg-� improved the feed conversion ratio (P < 0.05). The addition of 3 g kg-� of the blend of formic and lactic acids improved the daily weight gain of the finishing pigs and during the total fattening period, whereas the feed conversion ratio was improved by all the addition levels (P < 0.05). The growth promoting effect of the two acidifiers did not differ significantly, and no significant linear or quad- ratic trends were found in the pigs’ performance results between the addition levels from 3 to �2 g kg-�. The � Deceased.. 325 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Vol. 15 (2006): 324–339. Introduction Dietary formic acid additions have been shown to enhance the growth performance and/or feed con- version ratio of fattening pigs (Baustad �993, Par- tanen et al. 2002). In those studies, dietary formic acid additions ranged from 5 to �2 g kg-� of feed. Partanen et al. (2002) found that the growth-pro- moting effect of formic acid was improved when it was mixed with a small amount of potassium sorb- ate. In that study, grower and finisher diets con- tained 0.4 g kg-� of potassium sorbate and 8 g kg-� of formic acid. Although potassium sorbate is highly soluble in water (Sofos and Busta �993), its solubility in formic acid is poor. Homogenous so- lutions of formic acid and potassium sorbate are difficult to achieve, because milky precipitation occurs already when potassium sorbate constitutes less than 5% of a mixture with formic acid. The problem of sorbate precipitation in formic acid could be overcome by absorbing formic acid first into a solid carrier such as diatomaceous earth and then coating it with potassium sorbate. When po- tassium sorbate solution is sprayed onto carrier containing formic acid, the sorbate is converted to sorbic acid forming a coating resistant to water and acidic environments (Swedish patent 040�672-�, Kemira GrowHow Ltd, Sweden). Formic acid is corrosive and has a strong pun- gent odour, which makes it difficult to handle in feed mills. However, the corrosiveness and evapo- ration of formic acid have been reduced effectively by ammoniation of water-free formic acid or by absorbing formic acid into diatomaceous earth or by coating carrier-absorbed formic acid with sorb- carcass quality of the pigs was not influenced by the acidifiers (P > 0.05). The frequency of severe gastric alterations tended to be smaller when the diets contained �2 g kg-� of the sorbate-coated formic acid (P = 0.07), but the results of the other acidifier treatments did not differ significantly from those in the negative control. In conclusion, both the sorbate-coated formic acid and the blend of formic and lactic acids have a growth-promoting effect in fattening pigs already in small dosages, but they do not influence carcass qual- ity or cause gastric alterations. Key words: fattening pigs, organic acids, performance, carcass quality, gastric ulcers ate (Virtanen et al. 2004). These make the handling of formic acid and its addition to feed easier and safer than the use of regular liquid formic acid. Ab- sorbing formic acid into diatomaceous earth and coating it with sorbate has also enhanced the anti- microbial effect of formic acid against E. coli and Salmonella (Virtanen et al. 2004). So far, the growth-promoting effect of an acidifier, in which formic acid is absorbed in diatomaceous earth and coated with sorbate, has not been investigated with fattening pigs. Dietary lactic acid additions have enhanced the growth performance of growing pigs (Jongbloed et al. 2000) and weaned piglets (Roth et al. �993, Maribo �999), but some studies have not been able to show significant performance improvement (Maribo et al. 2000a). Dietary lactic acid additions that have been able to enhance the growth perform- ance of weaned piglets and growing pigs have usu- ally been over �0 g kg-� of feed, whereas generally less than �0 g kg-� of formic acid is needed. The additions of combinations of lactic and formic acid, both at levels of 5 or 7 g kg-� of feed have enhanced the performance of weaned piglets (Mar- ibo et al. 2000b, Jørgensen and Boes 2004). Blends of formic acid and lactic acid (�:� and 2:�) have also been reported to reduce the number of colif- orms in the small intestine of piglets more effec- tively than plain formic acid (Franco et al. 2005). However, the growth-promoting effect of blends of formic acid and lactic acid has not been investi- gated with fattening pigs. Dietary formate additions have enhanced the performance of pigs from weaning to slaughter when both piglet and fattening pig diets have been supplemented with formate (Kirchgessner et al. 326 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Partanen, K. et al. Growth-promoting effects of two dietary acidifiers �997). Limiting dietary formate additions to the piglet period did not improve the performance of pigs from weaning to slaughter. However, the per- formance improvement produced by adding formate only to fattening diets equalled that produced by adding it to both piglet and fattening pig diets. Ac- cording to Lindermayer and Propstmeier (�994), the advantage of dietary organic acid and in-feed antibiotic additions during the growing period is lost if these additives are removed from the finisher feed. The amount of feed consumed by fattening pigs from ca 25 kg to slaughter is large, generally over 220 kg per pig, and the majority of feed is con- sumed during the finishing period. To keep the cost of dietary organic acid additions at a reasonable level, it is necessary to find the minimum addition level at which the additive is effective during the whole fattening period. However, the growth-pro- moting effect of small dietary organic acid additions has scarcely been investigated in fattening pigs. The aim of this experiment was to study the growth-promoting effect of two formic-acid-based acidifiers, when they were added to the diets of growing and finishing pigs at levels of 3, 6, and �2 g kg-� of feed. The sorbate-coated formic acid con- sisted of formic acid and ammonium formate that were absorbed in a diatomaceous earth carrier and coated with potassium sorbate. This product con- tained ca 50% diatomaceous earth. The investi- gated liquid blend contained formic and lactic ac- ids as the major components. The acidifier-supple- mented diets were compared to both negative and positive control treatments, in which the grower and finisher diets contained no growth promoters or the grower diet was supplemented with avil- amycin, respectively. The effects of dietary acidi- fiers on the carcass quality of pigs and the presence of gastric alterations were also studied. Material and methods The experimental protocol was evaluated and ap- proved by the Animal Care and Use Committee of MTT Agrifood Research Finland. Experimental procedures A total of 320 growing-finishing pigs (�05 Finnish Landrace, ��4 Yorkshire, and �0� crosses of these breeds) with an average initial body weight of 2�.4 kg (SD �.9) were used in the experiment. The pigs originated from the swine herd of MTT Agrifood Research Finland. Two gilts and two barrows were randomly allotted to pens of �.7 m × 2.5 m, and the pens were randomly allotted to eight dietary treat- ments, �0 pens per treatment. To create low-hy- giene growing conditions, faeces were removed from the pens only every second day. Manure was removed from the solid, concrete floor dunging ar- eas daily by means of scrapers, which allowed di- arrhoea to spread between the pens. Wood shav- ings were used as bedding material during the growing period only. Two acidifiers based on formic acid were used. The sorbate-coated acidifier (BOLIFOR® Grower/ Finisher FA2300S, Kemira GrowHow Ltd, Swe- den) consisted of formic acid and ammonium for- mate that were absorbed into a diatomaceous earth and coated with potassium sorbate. The ratio of sorbic to formic acid was 5.2:�00, calculated as �00% acids. The investigated liquid blend (an ex- perimental formula by Kemira GrowHow Ltd, Sweden) contained formic and lactic acids as the major components in a ratio of 28:�00, calculated as �00% acids (in this paper it was named as the blend of formic and lactic acids). Both acidifiers were added to grower and finisher diets at levels of 3, 6, and �2 g kg-� of feed. The basal grower and finisher diets without any growth promoters were used as a negative control treatment. In the positive control treatment, the grower diet was supplement- ed with avilamycin (40 mg kg-�; Maxus G®, Elan- co, Germany), whereas the finisher diet contained no growth promoters. The experimental diets were based on barley, oats, and soybean meal, which were supplemented with pure amino acids, minerals, and vitamins (Ta- ble �). The grower and finisher diets were formu- lated to meet the nutrient requirements of growing and finishing pigs according to Tuori et al. (�996). The grower and finisher diets contained 8.6 and 8.7 MJ of net energy (NE) calculated according to 327 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Vol. 15 (2006): 324–339. Schiemann et al. (�972), 8.5 and 7.� g of apparent ileal digestible lysine, 5.0 and 4.5 g of apparent ileal digestible methionine and cystine, 5.� and 4.2 g of apparent ileal digestible threonine, 7.5 and 7.0 g of calcium, and 6 and 5.5 g of phosphorus per feed unit (feed unit = 9.3 MJ NE), respectively. Di- ets were pelleted at ca 60°C into 4-mm pellets (Amandus Kahl Nache, Germany). The pigs were fed according to a restricted, age-based feeding scale; growing pigs received ��.2–20.5 MJ NE per day for the first six weeks of the experiment and finishing pigs 22.3–29.8 MJ NE per day from week seven until slaughter. The daily feed allowance was given in two portions at 0700 and �500. Feed Table �. Ingredients of grower and finisher diets supplemented with avilamycin or increasing levels of a sorbate-coated formic acid or a blend of formic and lactic acids. Control Avila- mycin Sorbate-coated formic acid Formic and lactic acid blend Acidifier addition, g kg-� of feed 3 6 �2 3 6 �2 Grower diets Barley 59.63 59.6� 59.33 59.03 58.43 59.33 59.03 58.43 Oats 20.00 20.00 20.00 20.00 20.00 20.00 20.00 20.00 Soybean meal �7.64 �7.64 �7.64 �7.64 �7.64 �7.64 �7.64 �7.64 Limestone 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 Monocalcium phosphate 0.57 0.57 0.57 0.57 0.57 0.57 0.57 0.57 Maxus G®a – 0.02 – – – – – – BOLIFOR® Grower/Finisher FA2300Sb – – 0.30 0.60 �.20 – – – Blend of formic and lactic acidsc – – – – – 0.30 0.60 �.20 Mineral-vitamin premixd �.30 �.30 �.30 �.30 �.30 �.30 �.30 �.30 L-Lysine HCl 0.�2 0.�2 0.�2 0.�2 0.�2 0.�2 0.�2 0.�2 L-Threonine 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 Finisher diets Barley 64.86 64.86 64.56 64.26 63.66 64.56 64.26 63.66 Oats 20.00 20.00 20.00 20.00 20.00 20.00 20.00 20.00 Soybean meal �2.60 �2.60 �2.60 �2.60 �2.60 �2.60 �2.60 �2.60 Limestone 0.69 0.69 0.69 0.69 0.69 0.69 0.69 0.69 Monocalcium phosphate 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 BOLIFOR® Grower/Finisher FA2300Sb – – 0.30 0.60 �.20 – – – Blend of formic and lactic acidsc – – – – – 0.30 0.60 �.20 Mineral-vitamin premixd �.30 �.30 �.30 �.30 �.30 �.30 �.30 �.30 L-Lysine HCl 0.�0 0.�0 0.�0 0.�0 0.�0 0.�0 0.�0 0.�0 L-Threonine 0.�2 0.�2 0.�2 0.�2 0.�2 0.�2 0.�2 0.�2 a Maxus G® provided 40 mg of avilamycin per kg of feed. b BOLIFOR® Grower/Finisher FA2300S contained formic acid and ammonium formate in a diatomaceous earth carrier and with a sorbate coating, and the ratio of sorbic to formic acid was 5.2:�00, calculated as �00% acids. c The blend of formic and lactic acids contained formic and lactic acids as the major components in a ratio of 28:�00 calculated as �00% acids. d Per kilogram of feed, the premix contained Ca, 2.3 g; P, 0.8 g; Mg, 0.5 g; NaCl, 3.3 g, Fe, �03 mg; Cu, 22 mg; Zn, 9� mg; Mn, 23 mg; Se, 0.28 mg; I, 0.28 mg; vitamin A, 5�70 IU; vitamin D3, 5�7 IU; vitamin E, 50 mg; thiamin, 2 mg; ribo- flavin, 5 mg; pyridoxine, 3 mg; vitamin B�2 20 µg; biotin, 0.2 mg; pantothenic acid, �4 mg; niacin, 20 mg; folic acid, 2 mg; and vitamin K, 2 mg. 328 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Partanen, K. et al. Growth-promoting effects of two dietary acidifiers refusals were not measured, but the daily allow- ance was temporarily decreased if pigs did not fin- ish their rations. Water was available ad libitum from drinking nipples, which were located in the dunging area. For the first four weeks of the experiment, the pens were checked daily for the presence of diar- rhoea. The consistency of faeces was scored as fol- lows: 0 = normal, solid faeces, � = soft faeces, 2 = moderate diarrhoea (soupy faeces), and 3 = severe diarrhoea (watery faeces). The diarrhoea index was calculated as a sum of the daily diarrhoea scores during the observation period. The pigs were weighed 0, 3, 6, and 9 weeks from the beginning of the experiment and then weekly until they reached the weight of �03 kg and were slaughtered at a commercial slaughterhouse. Carcass lean percentage, fat thickness, and meat colour measurements were taken from hot carcass- es with a Hennessy Grading Probe GP4 (Hennessy Grading Systems Ltd, Auckland, New Zealand). The measurements were taken in two locations: the first one after the last rib, 8 cm from the mid- line, and the second one between the �2th and �3th rib, 6 cm from the midline. The stomachs of 206 randomly selected pigs were collected at slaughter to investigate the pres- ence of gastric alterations. At the abattoir, the stomachs were opened, emptied, rinsed, and chilled to a temperature close to 0°C. The stomachs were transported to the laboratory, and they were visu- ally evaluated on the day after the slaughter for abnormalities in the pars oesophageal region using the scoring scale adopted from Hautala and Rau- tiainen (�99�) and described in Table 2. The pres- ence of different types of alterations (keratinisa- tion, streaky grooves or tiny erosions, erosion down to muscular part, scarring, and stenosis) seen in the first-, second-, and third-grade lesions were recorded too. The second- and third-grade lesions and stenosis of the oesophageal opening were con- sidered to cause discomfort and influence the wel- fare of the pig (Hautala and Rautiainen �99�). Chemical analyses The experimental feeds were prepared in �000-kg batches, and each batch was sampled and analysed for pH. The pH was measured from a feed-water mixture (50 g feed per �00 ml water) which had been stirred with a whirl mixer for 20 sec and kept at room temperature for �5 min and then remixed. During the experiment, the feeds were sampled Table 2. Scoring scale for the evaluation of gastric lesions in the pars oesophageal region of the pigs’ stomach (Hautala and Rautiainen �99�). Score Description Influences the welfare of the pig 0 A well demarcated white, yellow, or grey squamous epithelium over the pars oesophageal area. The surface undulates slightly. No � Hyperkeratinisation (roughness and flaky scales) in the oesophageal region of the stomach that is usually discoloured yellow (bile staining) and/or pitted (seen as streaky grooves or dark spotty holes) or minutely eroded and/or covered with mature scarring without stenosis of the oesophageal opening. No 2 Ulceration, i.e. erosion down to the muscular part of the mucosa for less than 50% of the pars oesophageal area. Yes 3 Ulceration for 50% or more of the pars oesophageal area and/or haemorrhagic ulceration and/or occurrence of a perforated ulcer and/or the wall of the stomach has clearly thickened and there is an inflammation of the serosa around the lesion. Yes Stenosis Scarring has narrowed the opening of the oesophagus. The stenosis feels like a rigid ring when one or two fingers are pushed into the opening of the oesophagus. Yes 329 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Vol. 15 (2006): 324–339. once a month and analysed for dry matter by dry- ing at �03°C for �6 h. At the end of the experiment, the sub-samples of each �000-kg feed batch were pooled and analysed for ash, nitrogen, amino ac- ids, and buffering capacity. Ash was determined according to the method 942.05 of the Association of Official Analytical Chemists (�990). Nitrogen was determined according to the Dumas method using a Leco N analyser, and crude protein content was calculated as 6.25 × N. Amino acids were ana- lysed according to the official EU method (EC �998). Buffering capacity at a pH of 3.0 and 4.0 was determined according to Prohászka and Baron (�980). Statistical analyses The pigs were group-fed in pens of four animals, and therefore the pen was considered as the ex- perimental unit. The performance data were ana- lysed with the MIXED procedure of SAS (SAS® for Windows, version 8.2) using the following model (Snedecor and Cochran �989): Yij = µ + ti + εij, where ti is the fixed effect of treatment i (i = �,…8), and εij is the normally distributed error with mean 0 and variance σ2. Organic acid treatments were compared to the negative and positive control treatments by the Dunnett test. The two acidifiers were compared to each other by contrasting the levels 3–�2 g kg-� of the sorbate-coated formic acid with the levels 3–�2 g kg-� of the blend of formic and lactic acids. The effect of dietary acidifier lev- el (3, 6, and �2 g kg-� feed) was investigated sepa- rately for both acidifiers by using orthogonal poly- nomials (linear and quadratic effect). Residuals were checked for normality. Frequencies of gastric alterations caused by erosion of the pars oesopha- geal area (erosion down to muscular part, scarring, and stenosis) and severe gastric lesions (grades 2 and 3) believed to cause discomfort to the pigs were analysed with the CATMOD procedure of SAS to determine the effect of treatment. The ad- ditive treatments were compared to the negative control treatment using the CONTRAST state- ment. Results and discussion Diet composition The analysed chemical composition of grower and finisher diets is presented in Table 3. The analysed crude protein contents were similar among the grower and finisher diets, but there were slight dif- ferences in the analysed amino acid contents. Be- cause the experimental feeds were manufactured in �000-kg batches as the experiment proceeded, the differences in the analysed amino acid contents probably reflect variations in the amino acid con- tents of the major feed ingredients, cereals and soybean meal. Sorbate-coated formic acid addi- tions of 3–�2 g kg-� of feed reduced the pH of the grower feed by 0.20–0.56 pH units and that of the finisher feed by 0.23–0.67 pH units. Additions of formic and lactic acid blend reduced the dietary pH slightly more: by 0.34–0.90 pH units in the grower feed and by 0.4�–�.05 pH units in the fin- isher diet. The finding that the blend of formic and lactic acids had a greater effect on dietary pH than the sorbate-coated formic acid was expected, as the latter contained ca 50% carrier, and it was cal- culated to provide only �.3, 2.6, and 5.2 g of �00% formic acid per kg of feed. Sorbic acid additions were very small – 0.07, 0.�4, and 0.29 g kg-� of feed – and sorbic acid has generally little influence on dietary pH (Kirchgessner et al. �995). The blend of formic and lactic acids provided 2.6, 5.2, and �0.4 g �00-% acid per kg of feed, and the ratio of lactic to formic acid was 28:�00. The grower feed contained more soybean meal and mineral supplements and less barley than the finisher feed. Both protein and mineral sources have a higher ability to resist pH change through acid addition than cereals do (Giger-Reverdin et al. 2002), which explains the observed smaller reduction in dietary pH in the grower than in the finisher feeds supple- mented with acidifiers. Dietary acidifiers did not 330 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Partanen, K. et al. Growth-promoting effects of two dietary acidifiers Table 3. Analysed nutrient composition of grower and finisher diets supplemented with avilamycin or increasing levels of a sorbate-coated formic acid or a blend of formic and lactic acids. Control Avilamycin Sorbate-coated formic acid Formic and lactic acid blend Acidifier addition, g kg-� of feed 3 6 �2 3 6 �2 Grower diets Dry matter, % 87.7 87.7 87.6 87.8 87.9 88.� 88.9 87.8 Ash, g kg-� dry matter 59 60 62 6� 63 60 57 57 Crude protein, g kg-� dry matter �89 �93 �93 �90 �89 �93 �93 �95 Amino acids, g kg-� dry matter Lysine �0.0 �0.3 �0.9 �0.0 �0.� �0.5 9.5 �0.4 Methionine 2.8 3.0 3.0 2.8 2.7 2.8 2.5 2.8 Cystine 3.4 3.7 3.8 3.3 3.5 3.3 3.0 3.6 Threonine 6.9 7.5 7.7 7.3 6.9 7.� 6.6 6.8 pH 5.6� 5.60 5.4� 5.35 5.05 5.27 5.09 4.7� Buffering capacity, meq kg-� dry matter pH 4 5�6 547 57� 50� 562 520 489 444 pH 3 657 66� 73� 676 75� 690 67� 684 Finisher diets Dry matter, % 88.2 88.2 88.0 88.� 88.0 88.� 88.0 87.7 Ash, g kg-� dry matter 57 57 59 60 62 58 58 57 Crude protein, g kg-� dry matter �73 �73 �74 �75 �74 �77 �76 �76 Amino acids, g kg-� dry matter Lysine 9.2 9.2 9.0 8.8 8.6 9.2 9.4 8.5 Methionine 2.8 2.8 2.8 2.6 2.7 2.8 2.6 2.7 Cystine 3.5 3.5 3.7 3.5 3.6 3.5 3.5 3.7 Threonine 6.2 6.2 6.7 6.4 6.2 6.9 6.8 6.5 pH 5.72 5.72 5.49 5.3� 5.05 5.27 5.09 4.7� Buffering capacity, meq kg-� dry matter pH 4 524 524 557 620 423 477 409 394 pH 3 655 655 680 745 593 626 584 6�6 have any profound or consistent effect on the die- tary buffering capacity of the grower and finisher feeds, which is in accordance with our previous results (Partanen et al. 2002). Health of pigs In general, the health status of the pigs was good, and they completed the trial successfully, except for seven pigs which were removed from the ex- periment. Three pigs died suddenly (one pig each in the negative control treatment and treatments with sorbate-coated formic acid and the blend of formic and lactic acids) during the trial, one pig was removed from the trial because of an infection on the head (in the negative control treatment), and three pigs were removed from the trial because of lameness (one pig in the positive control treatment and two in the treatments with sorbate-coated for- mic acid). The average removal rate was 2.2%. In the negative control treatment, two pigs in the same pen were medicated because their tails had been bitten. 331 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Vol. 15 (2006): 324–339. In general, the presence of diarrhoea was low during the first four weeks of the experiment (Ta- ble 4). No cases of severe diarrhoea (score 3) were observed, whereas moderate diarrhoea (score 2) was seen in �� pens for �–2 days. Soft faeces (score �) were recorded more often but only occa- sionally and not for longer than four consecutive days. The number of diarrhoea days and the diar- rhoea index per pen were low, and they were not influenced by dietary additions of sorbate-coated formic acid (P > 0.05). The additions of the blend of formic and lactic acids linearly decreased (P < 0.05) the number of diarrhoea days and the diar- rhoea index, but none of the treatments with differ- ent levels of this blend differed significantly from the control treatment (P > 0.05). The pigs of this study came from one herd, and they were moved only a short distance from the weaner to the fatten- ing units. The purpose of starting the experiment at a body weight of ca 20 kg and reducing the clean- ing frequency of the pens was to increase the risk of diarrhoea in this study. Despite these actions, the frequency of diarrhoea was low. In other or- ganic acid studies with fattening pigs, no or little diarrhoea has been observed too (Baustad �993, Øverland et al. 2000). Transportation and mixing of piglets from different environmental back- grounds generally increase the incidence of diar- rhoea in growing pigs and reduce growth perform- ance (Biehl et al. �985). In the study of Partanen et al. (2002), pigs from ten different farms were transported and mixed for fattening, and the inci- dence of diarrhoea was greater than in this study. Partanen et al. (2002) observed that additions of formic acid and additions of formic acid and sorb- ate both effectively reduced the incidence of diar- rhoea in pigs fed a diet of barley and soybean meal but not in pigs fed a high-fibre diet. In pigs fed a high-fibre diet, the frequency of diarrhoea was generally low. Growth performance and feed utilisation The pigs consumed their feed readily; feed refus- als were only occasionally found. During the 40- day growing period, the additions of the sorbate- coated formic acid did not have any significant influence on the weight gain or feed conversion ratio of the pigs (P > 0.05), but the daily weight gain was numerically the lowest in the control treatment and up to 60 g d-� higher in the treatment with 6 kg-� of the sorbate-coated formic acid (Ta- ble 5). In finishing pigs, however, all addition lev- els resulted in higher daily weight gain (P < 0.05), and the addition levels of 3 and �2 g kg-� improved Table 4. The incidence of diarrhoea in growing pigs fed diets supplemented with avilamycin or increasing levels of a sorbate-coated formic acid or a blend of formic and lactic acids. Control Avilamycin Sorbate-coated formic acid Formic and lactic acid blend Acidifier addition, g kg-� of feed 3 6 �2 3 6 �2 SEM Frequencies of pens with a Normal faeces 0.5 0.6 0.4 0.6 0.5 0.3 0.2 0.5 Soft faeces 0.4 0.4 0.5 0.2 0.3 0.6 0.6 0.3 Moderate diarrhoea 0.� 0.0 0.� 0.2 0.2 0.� 0.2 0.2 Diarrhoea daysc �.� �.3 2.� �.4 �.4 2.7 3.� 0.5 0.74 Diarrhoea indexb, c �.3 �.3 2.3 �.6 �.6 2.9 3.5 0.7 0.86 a In pens with normal faeces, all the daily faecal scores were 0 during the whole observation period. In pens with soft faeces, daily faecal scores ranged from 0 to �, and scores in pens with moderate faeces ranged from 0 to 2. b Diarrhoea index = a sum of daily diarrhoea scores during the first 26 days of the experiment. c The effect of the addition level of the acidifier containing formic acid and lactic acid was linear (P < 0.05). 332 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Partanen, K. et al. Growth-promoting effects of two dietary acidifiers Table 5. Growth performance and feed utilisation of growing-finishing pigs fed diets supplemented with avilamycin or increasing levels of a sorbate-coated formic acid or a blend of formic and lactic acids. Control Avila- mycin Sorbate-coated formic acid Formic and lactic acid blend Acidifier addition, g kg-� of feed 3 6 �2 3 6 �2 SEM Pens �0 �0 �0 �0 �0 �0 �0 �0 Pigs 38 39 39 39 39 39 40 40 Weight, kg Initial 2�.3 2�.4 2�.4 2�.8 20.9 2�.3 2�.2 2�.8 0.53 End of grower period 5�.6 53.8 52.6 54.5 5�.3 53.2 52.9 54.� �.24 Final �04.6 �05.8 �05.0 �05.0 �05.6 �05.4 �05.3 �04.7 0.6� Days in trial 96.5 93.4 92.6 90.3§ 92.8 9�.2§ 93.2 9�.�§ �.87 Weight gain, g d-� Grower period 758 8�0 78� 8�8 76� 799 793 808 25.4 Finisher period 957 987 �0�9§ �0�7§ �043§ �03�§ �005 �008 2�.0 Total fattening 872 9�� 9�5 928§ 92�§ 928§ 9�2 9�9 �7.� Feed consumption, kg of dry matter day-� Grower period �.52 �.56 �.56 �.60 �.5� �.57 �.55 �.58 0.03� Finisher period 2.6� 2.72 2.66 2.74 2.6� 2.69 2.65 2.65 0.042 Total fattening 2.�6 2.22 2.�8 2.23 2.�3 2.20 2.�7 2.�7 0.028 Feed consumption, kg of dry matter pig-� Grower period 60.7 62.3 62.4 63.8 60.3 62.6 6�.8 63.� �.23 Finisher period �48.8 �45.� �39.8 �37.8 �37.7 �37.5 �39.5 �34.6§ 4.02 Total fattening 209.5 207.4 202.2 20�.6 �98.0§ 200.2 20�.4 �97.7§ 3.56 Feed conversion ratio, kg of dry matter per kg of gain Grower period 2.0� �.93 2.0� �.96 �.99 �.96 �.96 �.96 0.037 Finisher period 2.82 2.79 2.66§ 2.73 2.53§¶ 2.63§¶ 2.67§ 2.67§ 0.050 Total fattening 2.5� 2.46 2.42 2.42 2.34§¶ 2.38§ 2.40§ 2.39§ 0.037 § Significantly different from the control treatment according to the Dunnett test (P < 0.05). ¶ Significantly different from the avilamycin treatment according to the Dunnett test (P < 0.05). the feed conversion ratio compared to the value in the negative control (P < 0.05). During the total fattening, the addition levels of 6 and �2 g kg-� improved the daily weight gain compared to value in the negative control (P < 0.05), and the highest addition level reduced the total amount of feed consumed per pig and improved the feed conver- sion ratio compared to the negative control’s val- ues (P < 0.05). However, there were no significant differences in the daily feed consumption. The feed conversion ratio was better than in the posi- tive control treatment (P < 0.05). These pigs reached the targeted end weight of ��0 kg sooner than those of the negative control (P < 0.05) when the diets were supplemented with 6 g kg-� of the sorbate-coated formic acid. The addition levels of 6 and �2 g kg-� of the sorbate-coated formic acid increased carcass gain compared to the negative control’s value (P < 0.05) and the amount of dry matter consumed per kg of carcass gain was lower when the highest addition level was used. Carcass gain was calculated by calculating 26.�% of slaughter loss for a 2�-kg pig. No clear linear or quadratic trend in the performance results of the pigs was seen among the acidifier levels of 3 to �2 g kg-� (P > 0.05). 333 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Vol. 15 (2006): 324–339. In the study of Sigfridson and Göransson (2003) with fattening pigs weighing 27–��5 kg, the same sorbate-coated formic acid as in this study was used at levels of 3 and 6 g kg-� of feed. Contrary to our findings, they reported that 3 and 6 g kg-� of sorbate-coated formic acid enhanced the weight gain of growing pigs, but only the addition of 3 g kg-� improved the feed conversion ratio com- pared to the negative control treatment’s value. However, the weight gain and feed conversion ra- tio of finishing pigs were not affected by dietary acid additions in that experiment. During total fat- tening, only the addition of 3 g kg-� resulted in im- provements in weight gain and feed conversion ratio compared to the control’s values. In that study, pigs were fed the same feed based on wheat, barley, soybean meal, and rapeseed meal through- out both the growing and finishing periods, and this feed had lower amino acid contents than the diets of this study. In the study of Maribo et al. (2004) with piglets aged 4–�0 weeks, an acidifier containing formic, phosphoric, lactic and citric ac- ids, and sodium formate in a diatomaceous earth carrier did not have any significant effect on the growth performance of weaned piglets at dietary addition levels of 3–9 g kg-� of feed. However, add- ing 6 g kg-� of feed of an acidifier containing for- mic, phosphoric and citric acids and ammonium and sodium formate in a diatomaceous earth car- rier and with a sorbate coating improved weight gain from 535 to 570 g d-� and slightly decreased the feed conversion ratio. Because the sorbate-coated formic acid con- tained ca 50% diatomaceous earth, the effective acid additions were small. It is unclear why such small acid additions were effective growth promot- ers in fattening pigs. Diatomaceous earth consists of fossilised skeletons of diatoms and other algae and has porous particles with a high capacity to absorb liquids. It also has toxin binding properties (Korunic �998). Dietary diatomaceous earth addi- tions have increased faecal dry matter content and decreased nitrogen excretion in the faeces and urine of weaned piglets (Bolduan et al. �99�). It is not known in what part of the digestive tract, how fast, and to what extent formic acid is released from the diatomaceous earth. According to Vir- tanen et al. (2004), the use of diatomaceous earth enhances the antimicrobial effect of formic acid, which could explain the growth-promoting effect of small dietary levels of a sorbate-coated formic acid. The sorbate coating may also have played a role in enhancing the growth-promoting effect of the carrier-absorbed formic acid. A sorbate-coated acidifier has enhanced the growth performance of weaned piglets at a dietary level of 6 g kg-� of feed, whereas the same amount of a similar acidifier without a sorbate coating has not (Maribo et al. 2004). Dietary sorbic acid additions have been re- ported to result in substantial growth-promoting effects in weaned piglets (Kirchgessner et al. �995, Roth and Raczek 2003). Sorbates are known to have an antimicrobial effect in relatively small dosages when the pH is lowered by other acids (Sofos and Busta �993). This could explain the synergistic growth-promoting effect of small sorb- ate additions in combination with formic acid (Partanen et al. 2002). The pKa value of sorbic acid is 4.76, and it displays inhibitory activity pri- marily against yeasts and moulds; the activity against bacteria is not as comprehensive and ap- pears to be selective (Sofos and Busta �993, Mat- suda et al. �994). Sorbates have the advantage of being effective at pH values as high as 6.5–7.0, whereas most other organic acids require a lower pH to be effective (Sofos and Busta �993, Matsuda et al. �994). The blend of formic and lactic acids did not influence the weight gain or feed conversion ratio of growing pigs (P > 0.05). In the finishing period and during total fattening, only the smallest addi- tion level resulted in a higher daily weight gain than in the negative control treatment (P < 0.05). However, all the addition levels resulted in better feed conversion ratios than in the negative control treatment (P < 0.05). The addition levels of 3 and �2 g kg-� increased carcass gain (P < 0.05), and all addition levels decreased (P < 0.05) the amount of dry matter consumed per kg of carcass gain com- pared to the negative control’s values. No clear lin- ear or quadratic trend in the performance results of pigs was seen among the acidifier levels of 3 to �2 g kg-� (P > 0.05). Blends containing formic acid 334 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Partanen, K. et al. Growth-promoting effects of two dietary acidifiers and lactic acid have not been studied in fattening pigs. In 4- to �0-wk-old weaned piglets, dietary additions of 7 g kg-� of both formic and lactic acid improved weight gain by �0% (Maribo et al. 2000b). A smaller addition of 5 g kg-� of both for- mic and lactic acid enhanced weight gain by 4% in piglets weighing 9–32 kg (Jørgensen and Boes 2004). There were no significant differences between the studied formic-acid-based acidifiers in the per- formance results and carcass quality of fattening pigs. However, both studied acidifiers enhanced the performance of finishing pigs but not that of growing pigs. This is in accordance with our previ- ous results (Partanen et al. 2002). Contrary results have been reported in several studies (Kirchgessner et al. �997, Siljander-Rasi et al. �998, Øverland et al. 2000, Sigfridson and Göransson 2003), in which growing pigs have benefited from dietary acidification whereas finishing pigs have not. In this study, the variation in the growth rate of pigs was larger among the growing than the finishing pigs (coefficients of variation were �5.6 and �2.5%, respectively). This larger variation could be one reason for the lack of a significant acid effect dur- ing the growing period, for the average growth rates of growing pigs fed acidifier-supplemented diets were up to 8% greater than in the negative control treatment. Several modes of action of dietary organic acid additions have been proposed (Partanen and Mroz �999). It seems that they influence the microflora of pigs, which reduces nutrient loss to bacteria and yeast (Jensen �998, Maribo et al. 2000a, b). Jensen (�998) has calculated that the amount of energy saved for the animals by the reduced microbial fer- mentation almost equals the improved feed to gain ratio. Several studies have shown that dietary or- ganic acid additions improve the apparent ileal di- gestibility of essential amino acids in fattening pigs (Partanen and Mroz �999), and dietary formic acid additions have been shown to improve the di- gestibility of fat too (Partanen et al. 200�). Im- proved apparent amino acid digestibility results from the reduced flow of bacterial nitrogen in the ileum (Partanen et al. 200�), which supports the hypothesis of reducing nutrient loss to microbes. There were, however, some differences in the ana- lysed total amino acid contents of the experimental feeds, which may have had some influence on the growth performance and feed utilisation of the pigs (Ferguson et al. 200�). Because the thickness of fat and the carcass lean percentage were similar among the experimental treatments, it is relevant to assume that the differences in the apparent ileal amino acid supply between the experimental treat- ments were however fairly small. The use of avilamycin in the grower diet did not enhance the performance of the pigs during the growing period or the whole fattening period when compared to the negative control (P > 0.05). In general, avilamycin and other antibiotic growth promoters have enhanced the performance of growing pigs. However, the use of antibiotic growth promoters only in grower feed has not re- sulted in improved performance results during the whole fattening period (Lindermayer and Propst- meier �994, Siljander-Rasi et al. �998, Partanen et al. 2002). The growth performance and feed con- version ratios of growing pigs fed diets supple- mented with organic acids did not differ from those fed grower feed with avilamycin (P > 0.05). Dur- ing the total fattening period, only the largest addi- tion of sorbate-coated formic acid resulted in bet- ter feed conversion than in the positive control treatment (P < 0.05). Carcass quality Neither the sorbate-coated formic acid nor the for- mic and lactic acid blend had any significant influ- ence on carcass leanness, fat thickness, or meat colour measurement compared to the values in the negative and positive control treatments (Table 6). This is in accordance with previous studies (Sil- jander-Rasi et al. �998, Partanen et al. 2002, Sig- fridson and Göransson 2003). According to the review of Royer and Granier (2004), dietary or- ganic acid additions do not influence the carcass quality of fattening pigs when the dietary protein supply is adequate. So far, only Øverland et al. (2000) have reported increased carcass leanness with formate-supplemented diets. 335 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Vol. 15 (2006): 324–339. Table 6. Carcass quality of growing-finishing pigs fed diets supplemented with avilamycin or increasing levels of a sorbate-coated formic acid or a blend of formic and lactic acids. Control Avila- mycin Sorbate-coated formic acid Formic and lactic acid blend Acidifier addition, g kg-� of feed 3 6 �2 3 6 �2 SEM Carcass weight, kg 77.8 78.5 78.0 77.3 78.6 78.0 78.3 78.3 0.54 Slaughter loss, % 25.7 25.8 25.8 26.3 25.6 26.0 25.7 25.3 0.32 Carcass gain, g d-� 645 675 679 682§ 686§ 687§ 678 689§ �2.6 Kg dry matter per kg of carcass gain 3.7� 3.64 3.58 3.64 3.43§¶ 3.53§ 3.53§ 3.5�§ 0.056 Carcass lean, % 58.4 58.4 57.8 58.3 58.2 58.2 58.2 58.7 0.37 Fat thickness, mma S� �2.� �2.3 �2.6 �2.� �2.2 �2.5 �2.2 �2.2 0.33 S2 �2.9 �3.� �3.7 �2.9 �3.� �3.� �3.2 �3.0 0.43 Meat coloura,b PSE� 36.9 36.5 38.0 37.4 36.6 37.4 36.3 35.9 0.84 PSE2 37.2 36.7 38.0 36.� 36.4 36.9 36.7 36.� 0.69 a The measurements were taken with a Hennessy GP4 grading probe, S� and PSE� after the last rib, 8 cm from the midline, and S2 and PSE2 between the �2th and �3th rib, 6 cm from the midline. b Meat colour is normal when the colour values are ≤ 58, whereas values above 58 indicate pale, soft and exudative (PSE) meat. § Significantly different from the control treatment according to the Dunnett test (P < 0.05). ¶ Significantly different from the avilamycin treatment according to the Dunnett test (P < 0.05). Stomach alterations  The observed gastric lesions found in the pars oesophageal region of the stomach are presented in Table 7. Stomachs were collected from the slaugh- terhouse when a large number of pigs (at least ten) were slaughtered at the same time. Therefore, the number of pigs per treatment varied somewhat. From the 206 investigated stomachs, �09 were from gilts and 97 from barrows. The frequency of stomachs that had a normal pars oesophageal re- gion was 39 and 25% in the negative and positive control treatments, and it ranged from �9 to 35% in the acidifier treatments. The frequency of second- and third-grade lesions, which were considered to be associated with a sensation of pain and to have an effect on the welfare of the pig (Hautala and Rautiainen �99�), tended (P = 0.07) to be smaller in the treatment with �2 g kg-� of the sorbate- coated formic acid than in the control. No other additive treatment differed from the negative con- trol (P > 0.05). So far, previous studies have not found any increase in the frequency of gastric ul- cers in fattening pigs fed diets supplemented with organic acid (Øverland et al. 2000, Partanen et al. 2002, Royer and Granier 2004, Canibe et al. 2005). In pigs, ulcers generally develop in the par oesophageal area of the stomach, whereas ulcers of the glandular area are rare (Doster 2000). Changes seen in the pars oesophageal region vary greatly. In the early stages, the pars oesophageal area becomes keratinised and roughened (Hautala and Rautiainen �99�). When the alteration advanc- es, the surface becomes gradually eroded until an ulcer develops (Doster 2000). In this study, kerat- inisation was seen in 46–64% of the stomachs in different dietary treatments. In several stomachs with second- or third-grade lesions, keratinisation was seen on the edges of the pars oesophageal area. When an ulcer heals, it leads to scarring or, in the worst cases, to strictures. The stenosis of the oesophageal opening feels like a rigid ring, and the opening can become so small that pigs often vomit after eating. Both scars and stenosis were found in 336 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Partanen, K. et al. Growth-promoting effects of two dietary acidifiers the pigs of this study, which means that eroded and/or ulcerated pars oesophagi had healed. The frequency of alterations that were caused by ero- sion of the pars oesophageal region down to the muscular layer in some stage of the pigs’ life as indicated by scarring or stenosis did not differ be- tween dietary treatments (P > 0.05). At present, the cause of gastric ulcers is un- known. Fine grinding of cereals, particularly of wheat, and pelleting have been shown to be associ- ated with the development of gastric ulcers (Regi- na et al. �999, Robertson et al. 2002). The main factor causing ulceration is the mixing of proximal and distal stomach contents, resulting in more fluid and acidic digesta in the proximal stomach (Regina et al. �999, Doster 2000, Royer and Granier 2004). According to Regina et al. (�999), the amounts of lactic and acetic acids in the stomach contents in- crease when pigs are fed coarsely instead of finely ground feed, and it is unlikely that organic acids cause ulcers. However, the increased amount of ammonia in the stomach may play a role in ulcer development (Regina et al. �999). Dietary formic acid additions have been reported to decrease am- monia concentration in the stomach contents of pigs (Roth et al. �992). In pigs, the role of stress and microbes in the development of gastric ulcers are still unclear (Eisemann and Argenzio �999, Doster 2000). In this study, most of the pigs with severe stomach alterations had some health issues which could have caused stress to them, i.e. ill- ness, leg problems, or tail biting. In addition, 6 of the 25 pigs with severe lesions originated from three litters. There is some evidence that ulcers can develop already in weaned piglets (Doster 2000), which could explain the finding that several pigs Table 7. The presence of alterations in the pars oesophageal region of the stomach in growing-finishing pigs fed diets supplemented with avilamycin or increasing levels of a sorbate-coated formic acid or a blend of formic and lactic acids. Control Avila- mycin Sorbate-coated formic acid Formic and lactic acid blend Acidifier addition, g kg-� of feed 3 6 �2 3 6 �2 Total number of investigated stomachs 23 28 27 22 30 28 22 26 Frequencies of alterations Keratinised 0.52 0.46 0.56 0.64 0.60 0.64 0.59 0.58 Streaky grooves or tiny erosions 0.48 0.39 0.59 0.45 0.47 0.54 0.4� 0.35 Erosion down to the muscular layer 0.22 0.07 0.�5 0.09 0.03 0.�4 0.00 0.04 Scarring 0.00 0.�� 0.�9 0.�4 0.�0 0.00 0.09 0.�2 Stenosis of the oesophageal opening 0.00 0.07 0.�5 0.05 0.03 0.00 0.09 0.�� Eroded, scarred or stenosis 0.22 0.�8 0.22 0.�8 0.�3 0.�4 0.09 0.�5 Frequencies of gastric lesion scores Grade 0 0.39 0.25 0.�9 0.27 0.33 0.29 0.32 0.35 Grade � 0.39 0.64 0.59 0.64 0.63 0.6� 0.59 0.54 Grade 2 0.�7 0.�� 0.22 0.05 0.03 0.�� 0.09 0.08 Grade 3 0.04 0.00 0.00 0.05 0.00 0.00 0.00 0.04 Frequency of alterations that influence the welfare of the pigsa 0.22 0.�� 0.22 0.09 0.03¶ 0.�� 0.09 0.�2 a Grade 2 and 3 alterations (eroded or ulcerated) and stenosis of the oesophageal opening. ¶ A tendency for a difference to the control treatment (P = 0.07). 337 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Vol. 15 (2006): 324–339. with severe gastric alterations came from the same litters. 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Available on the Internet: http://www.afma.co.za/AFMA_Template/feed- paper16.html 339 A G R I C U L T U R A L   A N D   F O O D   S C I E N C E Vol. 15 (2006): 324–339. Tutkimuksen tarkoituksena oli selvittää kahden muura- haishappopohjaisen happovalmisteen tehoa pieninä pi- toisuuksina lihasikojen kasvun edistäjänä. Sorbaatilla päällystetty muurahaishappo sisälsi piimaahan imeytet- tyä muurahaishappoa ja ammoniumformiaattia, joka oli päällystetty kaliumsorbaatilla. Tässä kiinteässä happo- valmisteessa oli noin 50 % piimaata, ja sorbiini- ja muu- rahaishapon suhde oli siinä 5,2:�00 �00-prosenttisina happoina. Muurahais-maitohapposeos sisälsi pääasiassa muurahais- ja maitohappoa, ja tässä nestemäisessä hap- povalmisteessa maito- ja muurahaishapon suhde oli 28:�00 �00-prosenttisina happoina. Tutkimuksessa oli 320 lihasikaa, jotka kasvatettiin noin 2� kg painosta noin �05 kg painoon. Molempia happovalmisteita lisättiin li- hasikojen alku- ja loppukasvatusrehuihin 3, 6 tai �2 g/kg. Negatiivisena kontrollina oli lisäaineeton ruokinta ja positiivisena kontrollina ruokinta, jossa alkukasvatus- rehuun lisättiin avilamysiini-antibioottia 40 mg/kg. Kumpikaan happovalmiste ja avilamysiini eivät vai- kuttaneet merkitsevästi sikojen kasvuun, eikä rehu- hyötysuhteeseen alkukasvatuksen aikana. Loppukasva- tuksessa sikojen kasvu parani, kun sorbaatilla päällystet- SELOSTUS Sorbaatilla päällystetyn muurahaishapon ja muurahais-maitohapposeoksen vaikutukset  lihasikojen tuotantotuloksiin, ruhon laatuun ja mahalaukun muutoksiin Kirsi Partanen, Maija Karhapää, Hilkka Siljander-Rasi, Erkki Virtanen ja Bernt Nilsson Maa- ja elintarviketalouden tutkimuskeskus ja Kemira GrowHow Oy tyä muurahaishappoa lisättiin rehuun 3–�2 g kg-�. Rehu- hyötysuhde parani, kun tätä valmistetta lisättiin 3 tai �2 g kg-�. Koko kasvatusajan kasvu oli kahdella suurimmal- la lisäystasolla parempi kuin negatiivisessa kontrolliryh- mässä, ja suurin lisäys paransi rehuhyötysuhdetta. Pie- nin muurahais-maitohapposeoksen lisäys paransi siko- jen kasvua loppukasvatuksessa ja koko kokeen aikana, ja kaikki lisäystasot paransivat rehuhyötysuhdetta nega- tiiviseen kontrolliryhmään verrattuna. Happovalmisteet eivät vaikuttaneet ruhojen teuraslaatuun. Negatiiviseen kontrolliryhmään verrattuna vakavia mahahaavaan viit- taavia muutoksia havaittiin hieman vähemmän, kun re- huun lisättiin �2 g kg-� sorbaatilla päällystettyä muura- haishappoa. Muissa happolisäysryhmissä havaittujen mahalaukun muutosten määrä ei eronnut negatiivisesta kontrolliryhmästä. Tulosten perusteella kiinteä, kantaja- aineeseen imeytetty ja sorbaatilla päällystetty muura- haishappo ja muurahais-maitohapposeos edistävät liha- sikojen kasvua ja parantavat rehuhyötysuhdetta jo pieni- nä lisäysmäärinä, mutta nämä happovalmisteet eivät vaikuta ruhon teuraslaatuun, eivätkä aiheuta mahahaa- vaan johtavia muutoksia sian mahalaukussa. Performance, carcass quality, and gastricalterations in fattening pigs fed additivescontaining formic acid either coated with sorbateor mixed with lactic acid Introduction Material and methods Results and discussion Conclusions References SELOSTUS