The effect of drying and partial neutralization of grass silage on voluntary intake by sheep Riitta Sormunen-Cristian Sormunen-Cristian, R. 1992. The effect of drying and partial neutralization of grass silage on voluntary intake by sheep. Agric. Sei. Finl. 1: 189-194. (Agric. Res. Centre of Finland, Inst. Anim. Prod., SF-31600 Jokioinen, Finland.) The experiment was carried out to provide information on the effect of drying and par- tial neutralization of direct cut grass silages on voluntary intake by sheep. It was designed as a 4 x 4 latin square comparison of four dietary treatments with four cas- trated Finnish Landrace rams. The DM content of the dried silage was 81.6 %. There were two levels of neutralization in the experiment: either 8 or 16 g ofsodium bicarbo- nate (NaHCO,) was mixed with the silages. The lower level ofneutralization raised the silage pH from 3.95 to 4.36 and the higher level took it up to 5.57. Both the drying of silage and the addition of 16 gofNaHC03 produced a significant (P<0.05) increase in the DM intake by sheep. The average daily intake for animals on dried silage was 71.4 g DM/kgW0-75 , on the 16 g neutralization level 62.7 g DM/kgW 075 , on the 8 g neutral- ization level 53.4 g DM/kgW0 75 and on untreated silage 52.4 g DM/kgW0 75. The sheep offered dried silage gained a significantly (P<0.05) larger amount of protein and energy than those on the other silagediets. The animals offered dried silage consumed 2,4 kg of water/DM kg daily and those offered untreated silage 0.7 kg. Key words: sodium bicarbonate, drying, silage intake, sheep Introduction Grass silage is - in addition to hay - an important roughage for sheep during the indoor feeding period. Since the feed unit price of silage is lower than thatofhay (Helander 1991), the utilizationof silage should be increased in order to reduce feed- ing costs in meat production. Silage is acceptable for feeding of pregnant and lactating ewes (Apo- lant and Chestnutt 1985), whereas weaned lambs at the age of 2-5 months have been found to grow better when fed on hay rather than on silage made from the same sward (Sormunen-Cristian 1984).Lambs fed ad libitum with only grass silage have even been found to lose weight (Saue 1968). Insufficient voluntary intake of silage by sheep is known to limit their growth rate as compared with hay. Some of the primary factors considered to reduce the voluntary intake of ensiled forages include, e.g., high moisture content (Wilkins et al. 1971), low silage pH (Shaver et al. 1985) as well as high contents of shortchain fatty acids (Wilkins et al. 1971) and lactid acid (McLeod et al. 1970). However, the low dry matter (DM) content of the forage has not always reduced the feed intake (Bull and Tampein 1974). The dry matter intake of silage has been found to increase along with an increase in its dry matter content (Merchen et al. 1986). The effect of DM content on the voluntary intake of silage has pri- 189 Agric. Sei. Finl. 1 (1992) https://www.c-info.fi/info/?token=tIp-oi6IQlQ0GRB-.Ma6qNd9fiz2DGQiNeJZb3Q.cfJeI4lsFbJwnHizmAnMcvzxVsGmsBYjqJRcyXeFlQLG7D1_FB6Onmdtj4KJJ7jHO_8OBirlZG_eHtVgYqFCxHN1jsCeep-3Bid6XUiwtxXHqBmSWuXADunQdkJ6RMdRErLvC3lS2PZDQ5J47wZD7qX3qtwQM2efSd4eZBk7DCgAuWYh_KhF_EHhzeKZ_ozv8m2fisO0QeXrtYt-1OOxQgD3IrGiLc1FpGnoipPio153N7hpCkgxTKYiPmXiSwQlDyU51LkavCXviKt2q7Sq marily been studied withprewilted silages. On the other hand, the effect of silage drying on payabil- ity has not been studied much. Sodium bicarbonate has been used as an additive in silage-based diets to offset the deleterious nutri- tional effects of low ruminal pH. Partial neutraliz- ation of silage acidity with sodium bicarbonate has been found to increase feed intake in many studies (Erdman et al. 1980, Kilmer et al. 1980, Shavier et al. 1985). However, sodium bicarbonate has not improved feed intake under all conditions. Findings have differed depending on animal species and on the way sodium bicarbonate was added and on the amounts added (Parhan and Thomas 1978). The objective of this study was to compare the volun- tary intake by sheep fed direct cut, dried silage and silage treated with sodium bicarbonate. Material and methods Four castrated rams of Finnish Landrace breed, aged 6.0 years (S.D. 0.02) with an average initial weight of 93.2 kg (S.D. 4.22) were allocated into four groups fed either direct cut silage (silage 1), dried silage (silage 2), and fresh silage neutralized with sodium bicarbonate (NaCH0 3 ) at a level of 8 g (silage 3) or 16 g (silage 4) per kg, respectively. The silages were offered ad libitum at 15 % refusal levels. Feed and water intakes were recorded daily throughout the experiment period of 12 weeks. The silages had been made simultaneously before mid June from similar herbage containing timothy (49 %) and meadow fescue (43 %). AIV II containing 80 % formic acid and 2 % phosphoric acid was used as an additive (5 1/t). Silage 2 was packed into gunny-sacks of 10 kg each, and artificially dried in a warm air dryer at 20-30°C for 48 hours before feeding. The purpose of drying the silage was to find out how much the feed intake increases when the dry matter content of silage is equal to that of hay. Sodium bicarbonate was mixed with silages 3 and 4 manually immediately prior to feeding. The samples of silages were analyzed for dry matter (Huida et al. 1986), pH, total and water soluble nitrogen by the Kjeldahl method, ammo- nium nitrogen (McCullough 1967), lactic acid (Barker and Summerson 1941), volatile fatty acid by gas chromatography (Huida 1973) as well as for water-soluble carbohydrates (WSC) (Somogyi 1945) and ethanol (Huida 1982). In vivo digesti- bility of untreated silage was determined by the total collection method with the wethers. It was assumed that digestibility did not differ signifi- cantly between the treatments (Hawkins et al. 1970,Parhan and Thomas 1978,Phillip 1983). The experiment was designed as a 4 x 4 latin square comparison. The results were subjected to an analysis of variance. The differences between the treatments were tested using Tukey's test (Steel and Torrie 1969). Results and discussion The chemical composition and feed value of the silages are shown in Table 1. In the experiment, the DM content of dried silage was about 81.6 % com- pared to 21-22 % in fresh and neutralized forages. The silages were made at an early stage of grass growth and thus had a very low crude fibre content, only 22-24 % of DM, and a high crude protein con- tent (N x 6.25), 21-24 % of DM on an average. The protein content of the dried silage was significantly (P<0.05) higher than that of the other forages. As expected, forage organic matter (OM) content was at its lowest in the neutralized silages. Ash content was increased significantly (P<0.05) by the higher level of sodiumbicarbonate addition. The quality ofeach silage was deemed to be good (Breirem and Home 1970). The extent of fermen- tation is indicatedby the low silage pH of 3.95, The neutralizationof silage 3 with 8 g sodiumbicarbon- ate raised the pH to 4.36 and neutralization with 16 g to 5.57 (P<0.05). Because the sodium bicarbonate was added to the silages just before feeding, the silage fermentation was not altered. Ammonium nitrogen accounted for 3.6-4.7 % of the total nitro- gen. No butyric acids were encountered in the fora- ges. The dried silage contained significantly (P<0.05) less acetic acid than the other silages. Drying reduced the volatile fatty acids in the silage 190 Agric. Sei. Finl. 1 (1992) Table I . Average chemical composition and feed value ofsilages during the feeding experiment. Silages Untreated Dried Treated with NaHCO, B_g 16g Dry matter (%) 21.28s 81.58b 21.51" 22.11 s Composition (% of DM) -Ash 6.63' 6.68a 7.72" 10.38" -Org. matter 93.37" 93.32" 92.28" 89.62b - Crude protein 21.72* 23.95b 21.14* 20.75* -Crude fat 7.35" 6.29bc 6.86»b 6.19 c -Crude fibre 24.25 22.49 23.65 22.99 Nil 40.06 40.59 40.63 39.69 pH 3.95' 4.19» 4.36" 5.57" Composition (% of DM) -Acetic acid 1.47' 0.63 b 1.70* 1.71* -Lactic acid 6.90 3.99 7.30 7.14 -WSC 7.47"b 9.94" 6.85* 6.14* -Ammonium-N 0.15 0.14 0.15 0.15 -Soluble-N 2.06' 2.19* 2.03' 1.91» -Total-N 3.48" 3.82* 3.61" 3.31' -Ethanol 1.38 0 0.62 1.52 In total-N, %: -Ammonium-N 4.26 3.57 4.14 4.66 -Soluble-N 59.08 57.23 56.77 57.51 Feed value: -kgfeed/FFU* 5.76' 1.50" 5.72* 5.73* -kgDM/FFU* 1.21' 1.22* 1.23" 1.26b -gDCP/kgDM 162* 180b 158' 155' -ME, MJ/kgDM 11.68' 11.60* 11.54" 11.21" Means with different supercripts are significantly different (P<0.05). • FFU =NKf> MJ/6.91 MJ by 60 % approximately. The average amount of lactic acid in the dried silage was 4.0 % of the DM, whereas the figures were 6.9, 7.3 and 7.1 % for the untreated and neutralized silages, respectively. However, the differences between the silages were not statistically significant (P>0.05). The lactic acid content of the dried silage was almost the same before and after drying. There were distinct differences in the voluntary intakes of the different silages (Table 2). Both the drying of silage and its partial neutralization with sodium bicarbonate increased the DM intake by the sheep. The most favoured was dried silage with an average DM intake of 2.29kg (71.4 g DM/kgW0 75) per day during a period of 12 weeks. The sheep had the lowest appetite for fresh, untreated silage, the average daily intake being only 1.65 kg (52.4 g DM/kgW 0 75 ). Adding 16 gof NaHC03 increased the intake more than the addition of 8 g of NaHCO,. At the lower level of neutralization, the average DM intake was 1.70 kg (53.4 g DM/ kgW 0 75 ) and at the higher level 1.98 kg (62.7 g DM/kgW075 ). The DM intakes in the different silage groups differed significantly (P<0.05), with the exception of silages 1 (untreated) and 3 (8 g NaHCOj). In the study by Phillip (1983), the voluntary intake of dry matter and organic matter was enhanced by the addition of sodium bicarbo- nate, but the effect was not statistically significant (P>0.10). When silage pH increased from 3.95 to 5.57 with 16g NaHC03 , the organic matter intake increased by 0.23 kg/day. The organic matter 191 Agric. Sei. Finl. 1 (1992) Table 2. The effect of drying and partial neutralization on the intake of silage and water (animal/day). Silages Untreated Dried Low level High level NaHC0 3 NaHC0 3 DM intake, g 1686c 2309a 1720c 2004 b -Silage 1654c 2286a 1697= 1984" -Salt 25 20 20 15 - Minerals 7 3 3 5 OM intake, g 1542d 2134a 1565cd 1776bc DOM intake, g 1214d 1658" 1235cd 1401"* CP intake, g 362 b 548» 360" 41 lb DCP intake, g 272 b 411» 270" 308" NE, FFU* 1.36b 1.87" 1.38" 1.57b ME, MJ 19.29b 26.52 a 19.58" 22.21 b Water intake, g 1158b 5552a 2035 b 2226" Water intake, g/DM kg 676 c 2405a 1214" 1129b Means with different supercripts are significantly different (P<0.05). * FFU=NKf, MJ/6.91 MJ intake on dried silage was significantly (P<0.05) higher than that on the other diets. Drying of silage increased the DM intake by 37 %. This finding differs from theresults of the study conducted by Bull and Tamplin (1974), according to which the drying of maize silage either decreas- ed the consumption or had no effect on the appetite. On the other hand, the DM intake of prewilted silage (80.0 % DM) by sheep has been found to be nearly 29 % higher than their intake of fresh silage (22.5 % DM) (Hawkins et al. 1970). Wilkins et al. (1971) have found that the nitrogen content of silage correlates positively and acetic acid content negatively with intake. It was assumed also in this study that the high protein and low acetic acid con- tent of the dried silage would have a positive effect on the dry matter intake. The partial neutralization of silage acidity with sodium bicarbonate has increased intake according to many reports (McLeod et al., Erdman et al. 1980,Phillip 1983, Shaver et al. 1985), but there are exceptions (Lancester and Wilson 1975, Parhan and Thomas 1978). In this study, the hig- her addition of NaCHO, increased the DM intake by 20 % and the lower by 4 %. The average res- ponse to raising the silage pH above 5 has been an increase of intake by 14.9 % with sheep (Parhan and Thomas 1978, Lancaster and Wilson 1975, McLeod et al. 1970). When sodium bicarbonate was infused straight into the rumen, its effect was found to be greater than when it was fed with silage (Parhan and Thomas 1978). Since NaHC03 has also improved the hay DM intake (Orth and Kaufmann 1966), its effect has not always been linked with silage acidity. Intake of organic matter was about 15 % higher for the animals receiving silage neutralized with 16 g bicarbonate than for those receiving the control treatment. The differences were not, however, sta- tistically significant (P>0.05). Parhan and Thomas (1978) found that bicarbonate addition to the feed increased the sheep's OM intake by about 5 %. Individual differences in DM intake by the ani- mals were pronounced. Differences in the intakes of the same silage variedbetween 0.15-0.50 kg, the largest differences being with untreated silage and 192 Agric. Sei. Finl. 1(1992) the smallest with the 16g neutralization level. An animal consuming an average of 68 g DM/kgW075 daily gained 236 gper day during the period of 12 weeks, while the average weight gain of the others was 167 g per day. The animals fed on dried silage gained signifi- cantly more (P<0.05)protein and energy than those on the other silage diets. Through the mere addition of NaHC0 3 , the animals acquired an average amount of 17 g and 39 gof sodiumper day. Sodium was also obtained from the silages themselves, minerals and salt. The effect of NaHC03 on salt and mineral intakes was small. The amount of sodium gained from neutralized silages surpassed manifold the sodium requirement of sheep. The need for sodium according to the nu- trient requirement varies depending on the pro- duction stage of the animal from 1 to 4 grams daily (NRC 1985). Despite the great excess of sodium, no health problems were encountered with the sheep. However, when applying these findings to the feeding of growing lambs, attention should be paid to the fact that the wethers were held on each of these silage diets for three weeks only. The treatments were associated with a marked increase in water intake (Table 2). The sheep offer- ed dried silage consumed almost five times more water than those on untreated diets, 5.5 kg per day on an average. At its highest, the water consump- tion was 10.0 kg per day. Water intake on dried silage was significantly (P<0.05) higher than on the other diets. Water intake has been found to have a strong positive correlation with dry matter intake (Hadjipanayiotou 1981). Neutralization increased the average water intake by 1 kilo. The lower level of neutralization in- creased water intake by 76 % and the higher by 92 %. The bigger water intake reflects the higher Na content in the neutralized diets. On diets supple- mented with 4 % NaHCO, water consumption has been found to increase by 16-25 % (Hadjipanayio- tou 1981). Drying increased water intake/DM kg significantly (P<0.05). The dried silage and silage neutralized with sodium bicarbonate proved to be acceptable to the animals. The addition of sodium bicarbonate to the feed appeared to be advantageous when the diet contained a high proportion ofacid silage. References Apolant, S.M. & Chestnut?, M.B. 1985. The effect of mechanical treatment ofsilage on intake and production of sheep. Anim. Prod. 40: 287-296. Barker, S.B. & Summerson, W.H. 1941. The colorimetric determination of lactic acid in biological material. J. Biol. Chem. 138: 535-553. Breirem, K. & Home, T. 1970. Förmidler og fbrkonserve- ring. Buskap og Avdrätt A/S, Gjovik. 459 p. Bull, L.S. & Tamplin, C.B. 1974. Effect of moisture on intake in sheep. J. Anim. Sci. 39; 234 (Abstr.). Erdman, R.A., Borrs, R.L., Hemken, R.W, & Bull, L.S. 1980.Effect of dietary sodium bicarbonate and magne- sium oxide on production and physiology in early lacta- tion. J. Dairy Sci. 63: 923-930. Parhan, S.M. A. & Thomas, P C. 1978.The effect ofpartial neutralization of formic acid silage with sodiumbicarbo- nate on their voluntary intake by cattle and sheep. J. Bri- tish Grssl. Soc. 33: 151-158. Hadjipanayiotou, M. 1982. Effect of sodium bicarbonate and ofroughage on milk yield and milk composition of goats and on rumen fermentation ofsheep. J. Dairy Sci. 19: 59-64. Hawkins, D.R., Henderson, H.E. & Purser, D.B. 1970. Effect of dry matter levels ofalfalfa silage on intake and metabolism in the ruminant. J. Anim. Sci. 31: 617-625. Helander, J. 1991. HILA:n, T-tarkkailun ja MATU:n tulok- sia. Maaseutukeskusten liitto. Helsinki. Mimeogr. 23 p. Huida, L. 1973. 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Manuscript received February 1992 Riitta Sormunen-Cristian Agricultural Research Centre of Finland Institute of Animal Production SF-31600 Jokioinen, Finland SELOSTUS Kuivauksen ja neutraloinnin vaikutus säilörehun maittavuuteen lampailla Riitta Sormunen-Cristian Maatalouden tutkimuskeskus Tutkimuksessa selvitettiin säilörehun neutraloinnin ja kui- vauksen vaikutusta säilörehun syöntiin lampailla. Tutkimus tehtiin neljällä kastroidulla pässillä 4x4 latinalaisen neliön mukaan. Kuivatun säilörehun kuiva-ainepitoisuus oli 81,6 %. Neutralointitasoja oli kaksi. Säilörehuun lisättiin joko 8 g tai 16 g natriumbikarbonaattia (NaHC0 3 ) rehukiloa kohti. Alempi neutralointitaso nosti säilörehun pH:n 3,95:5tä 4,36:een ja korkeampi taso 5,57:ään. Sekä säilörehun kui- vaaminen että 16 gramman NaHCG 3 -määrä lisäsivät merkit- sevästi (P<0,05) kuiva-aineen syöntiä lampailla. Keskimää- räinen syönti kuivatulla säilörehulla oli71,4 g ka/kgW0 75 , 16 gramman neutralointitasolla 62,7 g ka/ kgW°”, 8 gramman neutralointitasolla 53,4 g ka/kgW075 ja käsittelemättömällä säilörehulla 52,4 g ka/ kgW°-75 . Kuivatulla säilörehulla lam- paat saivat merkitsevästi (P<0,05) enemmän sekä valkuaista että energiaa kuin muilla rehuilla. Syötyä rehun kuiva-aine- kiloa kohti keskimääräinen vedenjuonti oli kuivalla rehulla 2,4 kg jakäsittelemättömällä rehulla 0,7 kg. 194 Agric. Sei. Fint. 1 (1992)