Agricultural and Food Science in Finland 523 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 I N F I N L A N D Vol. 7 (1998): 523–533. © Agricultural and Food Science in Finland Manuscript received July 1998 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 I N F I N L A N D Vol. 7 (1998): 523–533. Effect of anionic salts in concentrate mixture and calcium intake on some blood and urine minerals, acid-base balance and feed intake of dry pregnant cows on grass silage based feeding Susanna Tauriainen Department of Animal Science, PO Box 28, FIN-00014 University of Helsinki, Finland, e-mail: susanna.tauriainen@seamk.fi Satu Sankari and Satu Pyörälä University of Helsinki, Department of Clinical Veterinary Sciences, Hämeentie 57, PO Box 6, FIN-00581 Helsinki, Finland Liisa Syrjälä-Qvist Department of Animal Science, PO Box 28, FIN-00014 University of Helsinki, Finland Twelve Ayrshire and eight Friesian cows were randomly assigned to one of four prepartum diets in a 2 x 2 factorially designed experiment to determine the effect of anionic diet and calcium (Ca) intake on Ca metabolism, acid-base status and feed intake of grass silage based diets during the dry period. Four diets provided either 34 g or 74 g total dietary Ca/day, and were either anionic or cationic. Dietary cation-anion balance (DCAB), calculated as milliequivalents [(Na+ + K+) – (Cl- + S2-)], was –247 mEq/kg dry matter (DM) in the low DCAB group and +34 mEq/kg DM in the high DCAB group. DCAB was formulated using NH 4 Cl, (NH 4 ) 2 SO 4 and MgCl 2 as anionic salts. Cows received grass silage (5.2 kg DM), hay (0.9 kg DM) and concentrate mixture (1.6 kg DM) until calving. Blood and urine samples were collected 4, 3, 2 and 1 week before the expected calving date, at calving, the day after calving and 1 week following calving. The results indicate that the reduction of cation-anion balance induced mild metabolic acidosis and increased the ability of the cow to maintain blood Ca concentration. However, DCAB should be higher since urinary pH decreased markedly (< 6) and so remarkable changes in some blood electrolyte concentrations were noticed. Keywords: calcium, cows, ion balance, minerals, parturient paresis Introduction When prepartum dairy cows are fed rations with a low dietary cation anion balance (DCAB), a decrease in the incidence of milk fever has been observed in comparison with a high DCAB (Block 1984, Leclerc & Block 1989). Cows fed anionic salts tend to have higher plasma calci- um (Ca) concentrations than cows fed without anionic salts (Oetzel et al. 1988, Goff et al. 1991). Furthermore, it has been shown that mild mailto:susanna.tauriainen@seamk.fi 524 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 I N F I N L A N D Tauriainen, S. et al. Effect of anionic salts on dry cows I metabolic acidosis increases ionised Ca [Ca2+] in the blood (Bushinsky et al. 1985). The favour- able response of low DCAB diets is most likely to occur when cows have a positive Ca balance approaching parturition (Lomba et al. 1978). The Agricultural and Food Research Coun- cil (AFRC) (1991) recommends 23 g Ca/day for dairy cows during the dry period. Dutch experi- ments (Breukink 1993) demonstrated that Ca intake should be limited to 25 g Ca/day for dry pregnant dairy cows. However, in countries like Finland where dairy cows are fed silage ad libi- tum, such a low dietary Ca level is difficult to achieve, particularly when the Ca content of the grass silage can be as high as 7 g Ca/kg dry mat- ter (DM). Consequently, the daily Ca intake can vary between 50–90 g/d exceeding the Finnish feeding standard for dairy cows during the dry period (40 g Ca/d) (Tuori et al. 1995). There- fore, reducing the cation-anion balance could be a suitable method to prevent milk fever when the ration is naturally high in Ca. Our main objective was to evaluate the ef- fects of two different DCAB diets combined with a normal or high Ca content on the acid-base sta- tus and Ca metabolism as well as on some blood and urine minerals of pregnant cows during the dry period. This study was also used to develop a suitable anionic concentrate mixture for grass silage based diets of Finnish dry cows. Material and methods Experimental design and treatments Twelve Ayrshire and eight Friesian cows (age 47±14 months) with one or more lactations and no history of parturient paresis from previous lactations were selected from the University of Helsinki research farm. Cows weighed 652±63 kg at the beginning of the trial and were ran- domly assigned to one of four dietary treatment groups with 5 cows per diet. Cows received grass silage (5.2 kg DM/d), hay (0.9 kg DM/d) and experimental concentrate mixture (1.6 kg DM/ d). In addition, experimental cows were given vitamin and selenium supplements once a week as follows: vitamin A 200 000 IU/cow/week, vi- tamin D 40 000 IU/cow/week, vitamin E 400 mg/ cow/wk and selenium 2 mg/cow/week. The ex- perimental feeding period started 4 weeks be- fore the expected calving date and ended at par- turition. Immediately after parturition, cows en- tered the normal nutrition and management pro- gram applied at the University of Helsinki re- search farm. Experimental diets were arranged 2 x 2 fac- torially as follows: Diet 1, high DCAB, normal Ca (0.46%, 35 g/d); Diet 2, high DCAB, high Ca (0.94%, 74 g/d); Diet 3, low DCAB, normal Ca (0.47%, 33 g/d); and Diet 4, low DCAB, high Ca (0.96%, 74 g/d). Cows were divided into two blocks according to breed. Within each block cows were randomly assigned to one of four treatments in groups of four animals according to expected calving date. The low DCAB diet contained added chlorine (Cl) and sulphur (S), supplied primarily by adding chlorides of am- monium and magnesium and ammonium sul- phate. A mixture of different salts was used to avoid potential toxicity of using only one acidi- fying salt. Anionic salts were included in the concentrate mixture which was pelleted. The composition of the experimental diets and the concentrate mixtures are shown in Table 1. Us- ing the formula (Na+ + K+) – (S2- + Cl-) mEq/kg DM the high DCAB diet contained +34 mEq/kg DM, and the low DCAB diet contained –247 mEq/kg DM. Sulphur was included to avoid an excessive Cl- content. In addition, Tucker et al. (1991) have demonstrated that the effect of S2- on systemic acid-base status in lactating cows is similar to that of Cl. The high Ca level was achieved by adding 100 g/d calcium carbonate to the ration. Dietary energy content expressed as feed units (1 FU = 1 kg barley containing 11.7 MJ metabolizable energy according to MAFF 1975) was formulated to meet a moderate feed intake (i.e. 1.2 times maintenance) as recom- mended by van de Braak et al. (1986). Chemical analysis of the experimental diets is shown in Table 2. 525 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 I N F I N L A N D Vol. 7 (1998): 523–533. Table 1. Ingredient composition of the concentrate mixture and experimental diets1. Concentrate mixture High DCAB2) Low DCAB Ingredient, % Molasses 12.62 11.11 Wheat 22.33 22.22 Barley 12.62 11.11 Wheat bran 7.77 5.56 Beet pulp 17.48 16.67 Pelleted hay meal 17.48 16.67 NH 4 Cl 1.94 5.56 MgCl 2 3.88 4.44 (NH 4 ) 2 SO 4 – 3.33 NaH 2 PO 4 3.88 3.33 Diet Normal Ca High Ca Normal Ca High Ca Ingredient, % Grass silage 67.80 67.01 69.43 67.32 Hay 11.70 11.34 12.54 11.67 Concentrate mixture 20.50 20.51 18.03 19.84 CaCO 3 1.14 1.17 1) Dry matter basis. 2) Dietary cation-anion balance. Table 2. Dry matter intake, energy content, chemical composition1) and dietary cation-anion differences of experimental diets. High DCAB2) Low DCAB Normal Ca High Ca Normal Ca High Ca DMI3), kg/d 7.61 7.85 7.10 7.71 ME4), MJ/kg DM 10.90 10.77 10.72 10.60 Crude protein, % 14.90 14.73 16.50 16.53 Crude fiber, % 25.06 24.71 25.58 24.90 ADF5), % 28.30 24.81 25.69 25.96 NDF6), % 46.93 46.27 47.74 46.45 Ca,% 0.46 0.94 0.47 0.96 P, % 0.51 0.51 0.49 0.50 Mg, % 0.31 0.32 0.34 0.38 K, % 2.53 2.50 2.45 2.39 Na, % 0.26 0.26 0.20 0.21 Cl, % 2.05 2.03 2.51 2.60 S, % 0.24 0.23 0.37 0.38 DCAB7), mEq/kg DM +35 +33 –225 –268 1) Expressed on a dry matter basis. 2) Dietary cation-anion balance. 3) Dry matter intake. 4) Metabolizable energy calculated according to MAFF (1975). 5) Acid detergent fibre. 6) Neutral detergent fibre. 7) Dietary cation-anion balance calculated as milliequivalents (Na+ + K+) – (Cl- + S2-) per kg dry matter. 526 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 I N F I N L A N D Tauriainen, S. et al. Effect of anionic salts on dry cows I Cows were housed and fed in individual tie stalls with free access to drinking water. Grass silage was offered twice daily (0530 and 1400 h) and hay and concentrate once daily (1430 h). Concentrate remaining at 4–6 h postfeeding was removed and then manually mixed with silage. If feed was left until the next feeding, the amount refused was weighed and dry matter content was measured. Samples of grass silage, hay and con- centrate taken weekly at the time of feeding were pooled; grass silage was combined into monthly samples and hay combined into bales and fro- zen. Grass silage DM was determined weekly by drying at 100°C for 24 h. Cows were weighed and body condition was scored at the beginning of the experiment, two weeks later and after calving. Body condition was scored on a scale of 1 to 5, where 1 repre- sented extremely thin and 5 extremely obese animals (Windman et al. 1982). Sample collection Blood samples were collected from the jugular vein of each cow before afternoon feeding, on 4, 3, 2, and 1 weeks prepartum, on the day of calving, and at 1 d and 7 d postpartum. Samples were placed on crushed ice immediately after s a m p l i n g . O n e s a m p l e w a s t a k e n i n t o a heparinized vacuum tube for measurements of acid-base status. After immediate determination of gases and haemoglobin of whole blood, the remainder was centrifuged twice (3000 g for 5 min) and the plasma was stored frozen for sub- sequent measurement of Na, K, Cl, Ca, P and Mg. Another heparinized sample was taken into a vacuum tube for the determination of blood ionised Ca concentration within 24 hours of col- lection. For parathyroid hormone (PTH) blood samples were collected into a EDTA-tube, cen- trifuged twice and stored at –20°C prior to anal- ysis. Urine samples were taken before afternoon feeding on 4, 3, 2, and 1 weeks prepartum, on the day of calving, and 1 d and 7 d postpartum. Samples were obtained by vulval stimulation and stored frozen for pH, creatinine, hydroxy (OH) proline, Ca, Mg, K and Na analysis. Laboratory analysis Blood pH, partial pressure of CO 2 (pCO 2 ) and acid-base excess were measured using a blood gas analyser (ABL1 Acid-base laboratory, Ra- diometer A/S, Copenhagen). Measurements of pH and pCO 2 were corrected to correspond to measured body temperature and haemoglobin according to the manufacturer’s instructions. The corrected pH and pCO 2 values were used to cal- culate the actual bicarbonate (aHCO 3 ) and stand- ard base excess (SBE) values. Haemoglobin was determined by the cyanmethaemoglobin meth- od. Plasma PTH concentration was determined using an immunoradiometric assay (INTACT PTH Parathyroid Hormone Kit, Nichols Institute Diagnostics, USA). Plasma and urinary Ca and Mg were deter- mined by an atomic absorption spectrophotom- eter (Model 2380, Perkin Elmer Corp., Norwalk, Conn., USA) and creatinine by an automated kinetic alkaline picrate method (Fabiny & Er- tigshausen 1971). Plasma inorganic phosphorus was determined by the colorimetric method of Daly & Ertigshausen (1972). Concentrations of Na+, K+ and Cl- in plasma and blood ionised Ca were assessed by using ion-specific electrodes (KONE Microlyte 3 + 2, KONE Corp., Espoo, Finland). Urinary Na+ and K+ were analysed by a flame photometer (Corning 480, Ciba Corning Diag- nostics Limited, Halstead, Essex CO9 2DX, Eng- land). Urinary pH was measured by a pH meter (Radiometer Copenhagen, PHM 83 Autocal pH meter). Fractional excretion (FE x ) of electrolytes (x) was calculated using the following formula: FE x , % = x u × creatinine p /x p × creatinine u × 100, where u refers to urinary electrolyte concentra- tion, and p to the corresponding concentration in plasma. Concentration of OH-proline in urine was measured to estimate bone Ca mobilisation (Black & Capen 1971) according to Prockop & Udenfriend (1960). 527 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 I N F I N L A N D Vol. 7 (1998): 523–533. Feeds were analysed according to standard procedures (Association of Official Analytical Chemists, AOAC 1984). NDF (neutral detergent fiber) and ADF (acid detergent fiber) were de- termined according to Goering and Van Soest (1970). Feed DM was determined by drying at 100°C for 24 h. Samples for analysis were dried under vacuum at 50°C for one to two days and ground through a 1 mm screen. Ground samples were ashed at 560°C for 4 h. After dissolving the ash in 2.5 N HCl, Ca, Mg, Na and K were determined using an atomic absorption spectro- photometer (model 5100 PC, Perkin-Elmer). P was determined colorimetrically by the vanado- molybdate procedure of Tayssky & Shorr (1953). Dietary Cl was determined by the titrimetrical method of Mohr (Welcher 1963) and sulphur using a magnesium nitrate method in a commer- cial laboratory (Viljavuuspalvelu, Mikkeli, Fin- land). In vitro digestibility was measured in all roughage samples (Tilley & Terry 1963). All measurements were performed in duplicate. En- ergy content of concentrates as feed units was calculated according to published chemical com- position and digestibility coefficients (Tuori et al. 1995). Statistical analysis The data were analysed in two parts: 1. prepar- tum; from 4 weeks to 1 week before the expect- ed calving date. 2. peripartum; from 1 week be- fore expected calving to 1 week after calving. Plasma and urinary data were analysed by a re- peated measures analysis of variance within the SAS (1985) general linear model procedure for a complete block design including the effects of breed, dietary Ca level, DCAB and their inter- actions in the model. Since there was no inter- action between treatments and breed, this term was excluded from the model. Because prelimi- nary analysis of raw data indicated a heteroge- nous of variation for OH-prolin, Ca FE% and Mg FE%, these variables were logarithmically transformed to achieve a more homogeneous variance. A one-way analysis of variance of the four treatment groups was performed for data collected at 4 weeks before the expected calv- ing date to assess initial differences in experi- mental groups. Results Cows were fed a fixed ration throughout the ex- periment. Feed intake was slightly lower in the low DCAB group than in the high DCAB group due to the unpalatable anionic concentrate mix- ture. The low DCAB group left on average 0.34 kg DM/d of the daily total DM intake in com- parison with 0.06 kg DM/d in the high DCAB group. The body condition of all cows at partu- rition was satisfactory (3.1), indicating that the low feeding level during the dry period had no visible adverse effects. There were no differences (P>0.05) in blood or urinary analyte concentrations between the groups at the beginning of the trial, and there- fore pre-treatment values were not used as cov- ariates. A lowered cation-anion balance resulted in higher blood Ca ion concentrations both pre- partum (P<0.001) and peripartum (P<0.05, Ta- ble 3). Daily Ca intake did not affect any of the blood parameters measured. None of the cows showed clinical signs of milk fever around par- turition. A subclinical hypocalcaemia (Ca2+ < 1,00 mmol/l, Radostits et al. 1994) occurred in two cows in the high DCAB group. Concentra- tions of total Ca, inorganic P and Mg in plasma were unaffected either by Ca intake or DCAB during the trial, but Ayrshire cows had a higher prepartum plasma inorganic P concentration (P<0.001). Total Ca, inorganic P and Mg in plas- ma varied within the reference range (Radostits et al. 1994). Plasma K, Na and Cl concentrations were unaffected peripartum, but all of these pa- rameters were higher prepartum in cows fed the low DCAB diets (K, P<0.05; Na, P<0.05; Cl, P<0.01,Table 3). Plasma PTH concentration did not differ (P>0.10) between treatment groups. Blood pH, HCO 3 - and base excess were in- fluenced (P<0.05) by DCAB and the breed pre- 528 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 I N F I N L A N D Tauriainen, S. et al. Effect of anionic salts on dry cows I Table 3. Effect of dietary cation-anion balance (DCAB) and Ca intake on mean plasma mineral concentrations and urinary Ca excretion. Time from parturition Significance4) Factor –4 wk –3 wk –2 wk –1 wk 0 +1 d +1 wk Prepartum Peripartum Calcium2+ High DCAB 1.21 1.18 1.18 1.21 1.09 1.13 1.20 mmol/l Low DCAB 1.25 1.25 1.24 1.23 1.17 1.18 1.23 sem1) 0.012 0.012 0.009 0.014 0.030 0.018 0.017 Normal Ca 1.22 1.20 1.22 1.22 1.17 1.16 1.23 High Ca 1.23 1.23 1.21 1.22 1.10 1.14 1.20 sem 0.012 0.012 0.009 0.014 0.030 0.018 0.017 DCAB3) *** DCAB * Potassium High DCAB 4.43 4.48 4.42 4.39 4.35 4.18 3.98 mmol/l Low DCAB 4.48 4.70 4.66 4.53 4.28 4.24 4.18 sem 0.086 0.091 0.063 0.096 0.107 0.087 0.123 Normal Ca 4.42 4.60 4.43 4.40 4.31 4.14 4.15 High Ca 4.49 4.58 4.65 4.52 4.32 4.28 4.01 sem 0.086 0.091 0.063 0.096 0.107 0.087 0.123 DCAB * Chloride High DCAB 103.5 104.0 104.5 104.6 106.3 106.8 102.4 mmol/l Low DCAB 104.3 106.6 111.4 108.2 106.7 106.2 102.8 sem 0.43 0.83 2.35 0.91 1.03 0.42 0.34 Normal Ca 103.8 105.6 106.2 106.6 107.0 107.0 102.8 High Ca 104.0 105.0 109.7 106.2 106.0 106.0 102.4 sem 0.43 0.83 2.35 0.91 1.03 0.42 0.34 DCAB ** Sodium High DCAB 138.7 138.3 138.7 140.0 140.2 141.5 138.3 mmol/l Low DCAB 138.4 139.9 140.7 142.0 140.7 140.6 137.9 sem 0.303 0.537 0.454 0.543 1.033 0.645 0.462 Normal Ca 138.4 138.8 139.5 141.1 140.6 141.9 137.9 High Ca 138.7 139.4 139.9 140.9 140.3 141.1 138.3 sem 0.303 0.537 0.454 0.543 1.033 0.645 0.462 DCAB * Ca/creat.2)5) High DCAB 0.32 0.31 0.37 0.36 0.13 0.08 0.79 Low DCAB 1.00 2.26 1.65 1.54 0.52 0.22 0.74 sem 0.309 0.452 0.115 0.142 0.087 0.057 0.201 Normal Ca 0.63 0.84 0.90 0.74 0.23 0.15 0.73 High Ca 0.68 1.73 1.12 1.14 0.43 0.15 0.80 sem 0.309 0.452 0.115 0.142 0.087 0.057 0.201 DCAB *** DCAB ** Ca FE%5) High DCAB 1.68 1.89 2.43 2.13 1.04 0.58 4.00 Low DCAB 5.46 12.66 10.51 9.72 3.20 1.41 3.73 sem 1.557 2.352 0.813 0.687 0.500 0.378 1.086 Normal Ca 3.76 5.23 5.93 5.09 1.66 1.04 3.64 High Ca 3.38 9.32 7.01 6.75 2.58 0.95 4.09 sem 1.557 2.352 0.813 0.687 0.500 0.378 1.086 DCAB *** DCAB ** 1) sem = standard error of means 2) Ca/creatinine, mmol/mmol 3) DCAB = high DCAB vs low DCAB 4) P < 0.05 *, P < 0.01 **, P < 0.001 *** 5) These peripartum means were based on nine rather than ten observations and the sem given should be multiplied by 1.061 when making comparisons with other values. 529 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 I N F I N L A N D Vol. 7 (1998): 523–533. partum. Five cows from the low DCAB group experienced metabolic acidosis (Radostits et al. 1994) after one week from the start of the ex- periment. However, they could compensate for it within a week (Table 4). Urinary calcium excretion was markedly higher (P<0.001, Table 3) and urinary pH sig- nificantly lower (P<0.001) in cows fed the low DCAB diet than for cows fed the high DCAB diet (Table 4). Neither urinary excretion of Mg, K and Na, nor urine FE% of Mg, K and Na were significantly influenced by treatments. Urinary OH-proline/creatinine excretion tended to in- crease with increasing Ca prepartum (–3 wk: 0.018 vs. 0.032) but otherwise they were unaf- fected by treatments. Discussion The results of this trial demonstrated that the low DCAB diet had a beneficial influence on Ca metabolism during the periparturient period. This result agrees with previous reports of the effect of dietary Cl- and SO 4 2- anions on hypocalcae- mia in cows at parturition (Abu Damir et al. 1994, Phillippo et al. 1994). Feeding the high or normal Ca ration had no significant effect on the concentrations of selected elements in plasma. This observation is in agreement with the results of the studies by Schonewille et al. (1994). On the other hand Goff and Horst (1997) demon- strated in a recent study that K was more impor- tant risk factor for milk fever than dietary Ca. The DCAB in experimental groups was low- er than expected due to higher contents of S and Cl in silage and hay during the trial than found in the preliminary analysis. Our experiment showed that cows can tolerate moderately low DCAB without any detrimental effects. How- ever, the proportion of anions can also be low- er and anion feeding period shorter than in the current study to demonstrate the beneficial ef- fect on dairy cow Ca metabolism (Oetzel et al. 1988). The pH of blood was reduced (P<0.05) and acid-base status was changed in cows fed the low Table 4. Effect of dietary cation-anion balance (DCAB) and Ca intake on mean blood and urinary pH. Time from parturition Significance4) Factor –4 wk –3 wk –2 wk –1 wk 0 +1 d +1 wk Prepartum Peripartum Blood pH High DCAB 7.36 7.36 7.38 7.38 7.36 7.37 7.38 Low DCAB 7.36 7.28 7.35 7.36 7.36 7.38 7.38 sem1) 0.010 0.015 0.015 0.014 0.009 0.008 0.009 Normal Ca 7.36 7.34 7.37 7.36 7.36 7.38 7.39 High Ca 7.36 7.30 7.36 7.36 7.36 7.37 7.37 sem 0.010 0.015 0.015 0.014 0.009 0.008 0.009 DCAB2) * pH in urine3) High DCAB 8.44 8.40 7.98 8.07 8.14 8.40 7.91 Low DCAB 8.40 6.00 5.90 6.09 6.77 7.72 7.66 sem 0.049 0.188 0.254 0.286 0.220 0.232 0.221 Normal Ca 8.42 7.35 6.92 7.08 7.58 8.07 7.68 High Ca 8.42 7.06 6.96 7.08 7.34 8.05 7.90 sem 0.049 0.188 0.254 0.286 0.220 0.232 0.221 DCAB *** DCAB*** 1) sem = standard error of mean. 2) DCAB = cationic vs. anionic. 3) These peripartum means were based on nine rather than ten observations and the sem given should be multiplied by 1.061 when making comparisons with other values. 4) P < 0.05 *, P < 0.01 **, P < 0.001 *** 530 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 I N F I N L A N D Tauriainen, S. et al. Effect of anionic salts on dry cows I DCAB group. According to Phillippo et al. (1994) this is possibly a result of absorption of Cl-, because plasma Cl- levels were increased before parturition. The low DCAB diet increased blood ionised Ca (P<0.001). This observation has also been noted by many other authors (Oetzel et al. 1988, Oetzel et al. 1991, Abu Damir et al. 1994). Probably the result is due to mild meta- bolic acidosis as Bushinsky et al. (1985) showed with rats. The intracellular movement of hydro- gen in exchange for K helps to prevent an ex- cessive increase in extracellular fluid hydrogen concentration in the acid load. This can result in hyperkalemia. In our study it was noticed that in two out of ten cows in the low DCAB group the blood concentration was raised to over 5.0 mmol/ l after one week of feeding the experimental diet. Thus, the DCAB was too low. Considerable changes in blood electrolyte concentrations have been noticed even when the DCAB has not been as low as in the current trial (Fredeen et al. 1988). Actual HCO 3 - tended to be lower and blood pH was (P<0.05) lower for Ayrshire than Frie- sian cows prepartum. However, urinary pH was higher for Ayrshires than for Friesians. Ayrshire cows consumed more DM in relation to their body weight; this may be attributed to the high- er metabolic acid production by Ayrshire cows. Another explanation could be that Friesian cows have a better ability to conserve aHCO 3 - ions by reabsorption in the kidney, which affects acid- base balance. Plasma inorganic P was not affected by diet. This is in agreement with the results of other studies (Oetzel et al. 1988, Gaynor et al. 1989, Tucker et al. 1992). In the present study, with a dietary Mg content of 3.4 g/kg DM, there were no differences in plasma Mg concentration be- tween treatments. Oetzel et al. (1988) reported that feeding a low DCAB increased plasma Mg immediately prepartum when the feed Mg level was 2.2 g Mg/kg DM. Our assumption is that the higher level of Mg in the current experiment prevented the changes in plasma. Under normal conditions, renal antagonism between Ca and Mg may account for increased plasma Mg associat- ed with decreased plasma total Ca (Halse 1984). In this experiment urinary Mg excretion tended to increase with a low DCAB. Similar effects were observed by Gaynor et al. (1989) and Oet- zel et al. (1988). In general, the bovine kidney is highly effi- cient in conserving Ca. In our study, about 98% of Ca filtered by the kidney was reabsorbed in the high DCAB group prepartum. Cows in the low DCAB diet excreted 5 to 8 times more Ca in urine than cows fed the high DCAB diet. In ad- dition, about 11% of filtered Ca was excreted by cows fed the low DCAB diet compared with less than 3% for the high DCAB diet. These findings are in agreement with many other studies (Gaynor et al. 1989, Oetzel et al. 1991, Wang & Beede 1992, Mosel van et al. 1993). The level of Ca intake did not influence the amount of Ca excreted in the urine. Stacy & Wilson (1970) reported that the renal tubules are sensitive to acid-base status and that they respond to a low- ering of blood pH by decreasing tubular reab- sorption of filtered calcium. Thus, renal Ca ex- cretion appears to depend on DCAB rather than Ca intake. However, acidification in the low DCAB group was excessive since urinary pH decreased to below six when feeding was con- tinued for two weeks. According to Jardon (1995) urinary pH should be 6–7 to ensure the effect but avoiding excessive acidification. In the current study the measured amount of OH-proline in the urine was assumed to origi- nate from bone matrix. The low DCAB diet did not affect the ratio of urinary OH-proline to cre- atinine excretion although a minor increase was noticed after one week from the start of the tri- al. In experiments where OH-proline excretion has been reported (Gaynor et el. 1989, Goff et al. 1991), sample collection had been carried out more frequently and closer to parturition and may explain discrepancies with the current data. Concentration of plasma PTH was not affect- ed by the treatments although plasma Ca2+ con- centration was higher in the low DCAB group. This observation is in agreenment with earlier studies (Abu Damir et al. 1994, Goff et al. 1991, Phillippo et al. 1994) and implies that groups (low vs. high DCAB) have a difference in sensi- tivity to PTH as Goff et al. (1991) demonstrat- ed. 531 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 I N F I N L A N D Vol. 7 (1998): 523–533. Current results indicate that the anionic salt can maintain blood Ca2+ level during puerper- ium at different Ca intakes and may therefore decrease the risk of parturient paresis on grass silage based diets. However, clinical deficien- cies could have been shown even more clearly if cows had been older. Because of a lack of fa- cilities animal material was rather young. Dairy farmers could also successfully use salts of Cl- and SO 4 2- in the feed to control hypocalcemia when the Ca content of grass silage or hay is moderately high. Furthermore the additives must be carefully formulated to achieve sufficient ef- fects but avoid excessive acidification. The DCAB should probably be higher than in this experiment (–247 mEq/kg DM). In this trial the experimental diet was not palatable enough. It is necessary to develop more palatable concen- trate mixtures in order to feed an anion-contain- ing supplement separately from grass silage. Acknowledgements. The authors thank Mr. Juha Suomi and Mr. Jari Miettinen for their diligent care of experimental cows. These studies would not have been possible without the expert technical assistance of Mrs. Anne Hannikainen and Mr. Seppo Pirttikoski. References Abu Damir, H., Phillippo M., Thorp, B. H., Milne, J. S., Dick, L. & Nevison, I. M. 1994. Effects of dietary acid- ity on calcium balance and mobilisation, bone mor- phology and 1,25 dihydroxyvitamin D in prepartal dairy cows. Research in Veterinary Science 56: 310– 318. Agricultural and Food Research Council (AFRC) 1991. Technical Committee on Responses to Nutrients, Report No 6. A Reappraisal of the calcium and phos- phorus requirements of sheep and cattle. Nutrition abstracts and reviews, Series B, Livestock Feeds and Feeding. Vol. 61. p. 573–612. AOAC 1984. Official methods of analysis. Association of Official Analytical Chemists, Inc. Arlington. Virginia. 1141 p. Black, H. E. & Capen, C. C. 1971. Urinary and plasma hydroxyproline during pregnancy, parturition and lac- tation in cows with parturient hypocalcemia. Metab- olism 20: 337–344. Block, E. 1984. Manipulating dietary anions and cations for prepartum dairy cows to reduce incidence of milk fever. Journal of Dairy Science 67: 2939–2948. Braak, A. E. van de, Klooster, A. Th van’t & Malestein A. 1986. Influence of prepartum calcium intake on cal- cium mobilisation rate around parturition in dairy cows fed at a high prepartum feeding level. Veterinary Quarterly 8: 24–37. Breukink, H. J. 1993. Dutch experiments related to milk fever prevention. Acta Veterinaria Scandinavica Sup- plementum 89: 125–128. Bushinsky, D. A., Riera, G. S., Favus, M. J. & Coe, F. L. 1985. Response of serum 1,25(OH) 2 D 3 to variation of ionised calcium during chronic acidosis. American Journal of Physiology 249 (Renal Fluid Electrolyte Physiology 18): F361–F365. Daly, J. A. & Ertigshausen, G. 1972. Direct method for determining inorganic phosphate in serum with the “CentriChem”. Clinical Chemistry 18: 263–265. Fabiny, D. L. & Ertigshausen, G. 1971. Automated reac- tion rate method for determination of serum creati- nine with Centrifichem. Clinical Chemistry 17: 696– 700. Fredeen, A. H., DePeters, E. J. & Baldwin, R. L. 1988. Characterisation of acid-base disturbances and the effects on calcium and phosphorus balances of die- tary fixed ions in pregnant or lactating does. Journal of Animal Science 66: 159–173. Gaynor, P. J., Mueller, F. J., Miller, J. K., Ramsey, N., Goff, J. P. & Horst, R. L. 1989. Parturient hypocal- cemia in Jersey cows fed alfalfa haylage-based di- ets with different cation to anion rations. Journal of Dairy Science 72: 2525–2531. Goering, H. K. & Van Soest, P. J. 1970. Forage fibre anal- ysis. U. S. D. A. Agricultural Handbook 379. Wash- ington. p. 20. Goff, J. P., Horst, R. L., Mueller, F. J., Miller, J. K., Kiess, G. A. & Dowlen, H. H. 1991. Addition of chloride to a prepartal diet high in cations increases 1,25-dihydrox- yvitamin D response to hypocalcemia preventing milk fever. Journal of Dairy Science 74: 3863–3871. – & Horst, R. L. 1997. Effects of the addition of potas- sium and sodium, but not calcium, to prepartum ra- tions on milk fever in dairy cows. Journal of Dairy Science 80: 176–186. Halse, K. 1984. Calcium effects on renal conservation of magnesium in cows. Acta Veterinaria Scandinavica 25: 213–227. Jardon, P. W. 1995. Using urine pH to monitor anionic salt programs. Compendium on Continuing Educa- tion for the Practicing Veterinarian Food Animal 17: 860–862. Leclerc, H. & Block E. 1989. Effects of reducing dietary cation-anion balance for prepartum dairy cows with specific reference to hypocalcemic parturient pare- sis. Canadian Journal of Animal Science 69: 411– 423. Lomba, F., Chauvaux, G., Teller, E., Lengels, L. & Bien- fet, V. 1978. Calcium digestibility in cows as influ- 532 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 I N F I N L A N D Tauriainen, S. et al. Effect of anionic salts on dry cows I enced by the excess of alkaline ions over stable acid ions in their diets. British Journal of Nutrition 39: 425– 429. MAFF 1975. Energy allowances and feeding systems for ruminants. Ministry of Agriculture, Fisheries and Food. London, HMSO. Technical Bulletin 33. 79 p. Mosel, M. van, Klooster, A. Th. van’t, Mosel, F. van & Kuilen, J van der. 1993. Effects of reducing dietary (Na+ + K+)–(Cl- + SO 4 -) on the rate of calcium mobili- sation by dairy cows at parturition. Research in Vet- erinary Science 54: 1–9. Oetzel, G. R., Fettman, M. J., Hamar, D. W. & Olson, J. D. 1991. Screening of anionic salts for palatability, effects on acid-base status and urinary calcium ex- cretion in dairy cows. Journal of Dairy Science 74: 965–971. –, Olson, J. D., Curtis C. R. & Fettman, M. J. 1988. Am- monium chloride and ammonium sulphate for pre- vention of parturient paresis in dairy cows. Journal of Dairy Science 71: 3302–3309. Phillippo, M., Reid, G. W. & Nevison, I. M. 1994. Parturi- ent hypocalcaemia in dairy cows, Effects of dietary acidity on plasma minerals and calciotrophic hor- mones. Research in Veterinary Science 56: 303–309. Prockop, D. J. & Udenfriend, S. 1960. A specific method for the analysis of hydroxyproline in ttissues and urine. Analytical Biochemistry 1: 228–239. Radostits, O. M., Blood, D. C. & Gay, C. G. 1994. Veteri- an Medicine. 8th ed. Bailliere Tindal. London. p. 1315, 1319, 1727. SAS 1985. SAS User’s Guide, Statistics. 5th ed. SAS Institute Inc. Cary, NC USA. 956 p. Schonewille, J. Th., Klooster, A. Th. van’t & Beynen, A. C. 1994. The addition of extra calcium to chloride- rich ration does not affect the absolute amount of calcium absorbed by non-pregnant, dry cows. Jour- nal of Animal Physiology and Animal Nutrition 72: 272–280. Stacy, B. D. & Wilson, B. W. 1970. Acidosis and hyper- calciuria: renal mechanisms affecting calcium, mag- nesium and sodium excretion in the sheep. Journal of Physiology 210: 549–564. Tayssky, H. H. & Shorr, E. 1953. A microcolorimetric method for the determination of inorganic phospho- rus. Journal of Biology Chemistry 202: 675–685. Tilley, J. & Terry, R. 1963. A two-stage technique for in vitro digestion of forage crops. Journal of British Grassland Society 18: 104–111. Tucker, W. B., Hogue, J. F., Adams, G.D., Aslam, M., Shin, I.S. & Morgan, G. 1992. Influence of dietary cation- anion balance during the dry period on the occur- rence of parturient paresis in cows fed excess calci- um. Journal of Animal Science 70: 1238–1250. –, Hogue, J. F., Waterman, D. F., Swenson, T. S., Xin, Z., Hemken, R. W., Jackson, J. A., Adams, G. D., & Spicer, L. J. 1991. Role of sulfur and chloride in the dietary cation-anion balance equation for lactating dairy cattle. Journal of Animal Science 69: 1205– 1213. Tuori, M., Kaustell, K., Valaja, J., Aimonen, E., Saari- salo, E. & Huhtanen, P. 1995. Rehutaulukot ja ruokin- tasuositukset. Helsinki. 99 p. Wang, C. & Beede, D. K. 1992. Effects of ammonium chloride and sulphate on acid–base status and cal- cium metabolism of dry Jersey cows. Journal of Dairy Science 75: 820–828. Welcher, F. J. (ed). 1963. Standard methods of chemical analysis. 6th ed. D.Van Nostrand company, Inc. (Can- ada), Ltd. USA. p. 254–256. Windman, E. E., Jones, G. M., Wagner, P. E., Boman, R. L., Troutt, H. F. Jr & Lesch, T. N. 1982. A dairy cow body condition scoring system and its relationship to selected production characteristics. Journal of Dairy Science 65: 495–501. 533 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 I N F I N L A N D Vol. 7 (1998): 523–533. SELOSTUS Kationi-anionitasapaino ja kalsiumin saanti ummessaolevien lypsylehmien säilörehuruokinnassa Susanna Tauriainen, Satu Sankari, Satu Pyörälä ja Liisa Syrjälä-Qvist Helsingin yliopisto Kokeessa selvitettiin kationi-anionitasapainon ja kal- siumin saannin vaikutusta ummessaolevien lehmien tiettyihin verestä ja virtsasta mitattuihin kivennäisar- voihin sekä happo-emästasapainoon säilörehuvaltai- sella ruokinnalla. Tarkoituksena oli testata, voidaan- ko anionisten suolojen lisäämisellä ennen poikimis- ta vaikuttaa poikimisen aikaiseen kalsiumaineenvaih- duntaan. Lisäksi tutkittiin, onko kalsiumin saannilla vaikutusta anionisten suolojen tehoon. Kationi-anio- nitasapaino laskettiin [(Na+ + K+) – (Cl- + S2-)] mEq/ kg kuiva-ainetta (ka). Se oli joko –273 tai +34 mEq/ kg ka. Kalsiumin saanti oli joko 34 g tai 74 g kal- siumia päivässä. Suoloina käytettiin magnesiumklo- ridia, ammoniumkloridia ja -sulfaattia. Lehmät sai- vat säilörehua (5.2 kg ka), heinää (0.9 kg ka) ja täys- rehua (1.4 kg ka) neljä viikkoa ennen odotettua poi- kimista poikimispäivään saakka. Veri- ja virtsanäyt- teitä otettiin 4, 3, 2 ja 1 viikkoa ennen odotettua poi- kimista sekä poikimispäivänä, 1 vrk ja 1 viikko poi- kimisen jälkeen. Lehmien, joiden kationi-anionitasa- paino oli säädetty negatiiviseksi, veren ionisoitunut kalsium säilyi poikimisen aikaan vakaana verrattuna lehmiin, joiden kationi-anionitasapaino oli positiivi- nen. Kationi-anionitasapaino –247 mEq/kg ka osoit- tautui kuitenkin liian negatiiviseksi, koska se aihe- utti muutoksia lehmien veren happo-emäsarvoihin sekä alensi liikaa virtsan pH-arvoa (<6). Lisäksi koe- rehun maittavuus oli huono. Kalsiumin saannilla ei ollut vaikutusta mitattuihin parametreihin. 534 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 I N F I N L A N D Tauriainen, S. et al. Effect of anionic salts on dry cows I Title Introduction Material and methods Results Discussion References SELOSTUS