Effect of including barley or molassed sugar beet feed in grass silage diets on their digestion by cattle and sheep

The objective of the experiment was to compare the digestion of barley, a starch-based feedingstuff, with molassed sugar beet feed (SBF), a high-fibre, sugar-containing feedingstuff, when fed to cattle and sheep receiving silage. There were between-species differences in rumen measurements. Sheep had higher mean daily rumen ammonia-N concentrations; the molar proportions (mmol mol^?1 total rumen volatile fatty acids) of propionic acid were higher and those of n-butyric acid lower in sheep than in cattle. The feeding of barley was associated with increased rumen populations of protozoa and increased rumen ammonia-N concentrations compared with the feeding of SBF. There were no significant differences between the diets fed in whole tract or rumen digestion of organic matter or nitrogen. However, feeding SBF tended to increase the quantities of non-ammonia-N and microbial N entering the small intestine daily: feeding barley did not improve N flow to the small intestine.     

Assessment of rumen processes by selected-ion-flow-tube mass spectrometric analysis of rumen gases.

This work investigated the potential to use measurement of the concentration of certain gases in the rumen headspace to gain information about rumen processes and as a potential diagnostic tool. We used new equipment (selected-ion-flow-tube mass spectrometer) that allows rapid and precise analysis of many of the gases present in a sample. Samples of rumen headspace gas and corresponding samples of rumen liquor were taken from three lactating cows, prepared with rumen fistulae, at intervals after receiving their morning feed allocation (grass silage and concentrates). Hydrogen sulfide, methyl sulfide, and dimethyl sulfide, were the predominant gases that were measured in the rumen headspace by this technique. The concentrations of these sulfur compounds declined over the interval after feeding, mirroring ammonia concentrations measured in rumen liquor, reflecting their common dependence on the fermentation of sulfur amino acids. Ammonia concentrations in rumen headspace gas varied in the opposite direction to the concentration of ammonia in rumen liquor and likely depend more on the pH of rumen liquor. Consideration of the pKa of ammonia suggests that ammonia concentrations in rumen gas will be very low below pH 6, representing a useful diagnostic for subacute ruminal acidosis. Low concentrations of volatile fatty acids were detected in rumen gas. The molar proportions of volatile fatty acids were similar in gas and liquor samples, with rumen gas containing slightly less acetic acid and disproportionately more valeric and caproic acids.     

Ionic milieu of bovine and ovine rumen as affected by diet

Postprandial changes in osmolality, mineral, and volatile fatty acid concentrations in rumen fluid were examined in three cattle fed six widely differing diets. Mineral concentrations varied with diet and postprandial time. However, net changes in postprandial mineral concentrations did not contribute significantly to changes in osmotic pressure. There was an effect of diet and time after feeding on concentrations of volatile fatty acids. Postprandial changes in osmotic pressure were primarily due to changes in concentrations of volatile fatty acids. Magnesium oxide and sodium bicarbonate were fed to sheep to increase the osmotic pressure in rumen fluid. The salt supplement decreased acetate, propionate, heat, and methane production. However, rumen water flux was unaffected by the salt supplementation. Diets which produce hypertonic rumen fluid due to high mineral and/or concentrations of volatile fatty acids may reduce fermentation in rumen.     

Rumen volatile fatty acids and milk composition from cows fed hay, haylage, or urea-treated corn silage.

Alfalfa-brome hay, haylage, .5% urea-treated corn silage, or .5% urea plus 1% dried whey-treated corn silage was fed as the only forage to one of four groups of 10 lactating cows per group for a lactation trial of 10 wk. Rumen samples were collected via stomach tube 3 to 4 h after the morning feeding. The pH of the rumen samples from cows fed hay was higher than for cows fed haylage, urea-treated corn silage, and urea-whey corn silage, 6.69 versus 6.36, 6.40, and 6.50. Total volatile fatty acids and propionate were highest from cows fed urea-whey corn silage and were higher on all three fermented forages than cows fed hay. Acetate/propionate ratio was highest from cows fed hay and lowest from cows fed corn silages. Butyrate was highest from cows fed haylage or hay. Milk protein composition was not affected by ration although nonprotein nitrogen of milk was highest from cows fed the urea-treated corn silages. Oleic acid and total unsaturated fatty acids were lowest in milk fat from cows fed hay while palmitic acid was highest from cows fed hay and haylage. These results suggest that type of forage fed may cause small changes in rumen fermentation and in milk composition. The importance of these changes is unknown but may affect properties of dairy products produced from this milk.     

Metabolism of liquid whey fed to sheep.

Digestion was studied with three groups of four sheep each fed alfalfa hay. Treatments were whey only, whey plus water, and water only. Digestibilities of dry matter for the three rations were 71.3, 69.7, and 62.9%. Digestibilities of whey solids calculated by difference was 86.9% for whey only and 81.6% for whey plus water. Twelve sheep were in three trials to determine the intake of whey, water, and hay consumption. They were assigned to whey only, whey plus water, and water only. Hay, whey, and water consumption was 1.89, 8.73, and 0; 1.88, 7.62, and 1.21; and 2.05, 0, and 6.07 kg per animal daily. Three mature fistulated wether sheep were fed 6 liters of liquid whey daily. Three mature fistulated wether sheep uere fed 6 liters of liquid whey daily, and three similar sheep were fed water only. Rumen liquor samples were taken for analysis of volatile fatty acids at 0, 3, and 6 h after whey feeding on each of three alternate days. Alfalfa hay (1.2 kg/animal daily) was fed after the 6-h sampling. Molar percentage of acetic and valeric acids were lower and for butyric acid was higher for sheep fed whey. Propionic acid, acetate:propionate ratio, and total concentration were not affected significantly by whey feeding. Acetic acid decreased from 0 to 3 h, then partly returned to the prefeeding level at 6 h. The reverse was true for butyric acid. Valeric acid and total concentration of volatile fatty acids decreased from 0 to 6 h. Effects of day were unexplained.     

Studies of the effects on the fermentation pattern in the rumen of the addition of various sources and levels of the lower volatile fatty acids

The short term effects on rumen fermentation of the direct addition to the rumen of 1·5 M and 3 M of acetate, propionate and butyrate, given as the Ca²⁺, Na⁺, and NH⁺₄ salts and as the free acid were measured in a mature cow. Longer term effects of the oral addition of I·5 M of calcium and ammonium acetates were also measured in growing heifers. For all volatile fatty acids (VFA) each rate of addition consistently increased the level of VFA in rumen liquor, but these fell gradually over about 4 h. Total volatile fatty acids (TVFA) were lower when free acids were given than when their salts were used. There was little effect on rumen pH. Calcium acetate was unpalatable when offered orally, and it tended to depress TVFA levels. Mean effects of acetate salts given orally on molar percentage of acetate in rumen liquor were smaller than those found by direct addition.     

Influence of prilled fat and calcium salt of palm oil fatty acids on ruminal fermentation and nutrient digestibility

Four rumen cannulated Holstein cows were used in a Latin square design to examine the effect of supplemental calcium salt of palm oil fatty acids (.68 kg/d) or prilled fat (.68 or .91 kg/d) on DM intake, rumen fermentation, and nutrient digestibility. Basal diet contained 45% concentrate, 27.5% alfalfa silage, and 27.5% corn silage (DM basis), and treatments were balanced for calcium. Dry matter intake was similar among treatments. Ruminal pH, total VFA, and molar percentage acetate and propionate were not affected by fat supplementation. Feeding prilled fat decreased slightly ruminal molar percentage butyrate. Forage DM and neutral detergent fiber disappearance from ruminally suspended dacron bags did not differ due to treatment. For unknown reasons, total tract apparent digestibility of DM and NDF was lower when cows received the low amount but not the high amount of prilled fat. Milk yield and fat percentage were not significantly affected by treatment. Milk protein was maintained during prilled fat supplementation but decreased .13% during calcium salt of palm oil fatty acid supplementation. Both fat supplements appeared inert in the rumen and did not markedly affect nutrient digestion when supplemented at 3.5% or less of the total ration DM.     

柠条对滩羊肉品质、胃肠道挥发性脂肪酸及其菌群的影响

为探索日粮中添加柠条影响瘤胃、结肠内微生物生成的挥发性脂肪酸水平,进而调节滩羊肉品质、脂肪组织中主要脂肪酸含量的作用,本研究选取12只四月龄滩羊母羔随机分为两组,NC组饲喂30%精料及70%苜蓿颗粒,CK组为10%柠条替代等量苜蓿。预饲期10 d,正试期60 d。饲喂期结束屠宰时取其背最长肌、股四头肌、皮下脂肪,瘤胃、结肠内容物,利用16S rRNA测序技术、气相色谱-质谱联用技术等对滩羊瘤胃、结肠内菌群、脂肪组织的脂肪酸含量及肌肉理化特性进行测定。结果表明,饲喂柠条可导致滩羊股四头肌的压榨损失有提高的趋势,系水力和熟肉率有所下降;但饱和脂肪酸有降低的趋势,不饱和脂肪酸有提高的趋势;皮下脂肪中的软脂酸含量显著降低(P<0.05);瘤胃内丁酸和结肠内乙酸的浓度显著降低(P<0.05),结肠内异丁酸和异戊酸等支链脂肪酸水平极显著提高(P<0.01)。斯皮尔曼相关性分析显示,瘤胃内5-7N15菌属和YRC22菌属均与丁酸含量趋向正相关,而结肠内密螺旋体属与乙酸含量趋向正相关,但与异丁酸含量趋向负相关(0.05相似文献   

Effects of replacing maize silage with lucerne silage and lucerne silage chop length on rumen function and milk fatty acid composition

The objective of this study was to investigate whether higher lucerne (Medicago sativa; alfalfa) silage inclusion rate and longer lucerne chop length improves rumen function through increased provision of physically effective fiber, when included in a maize and lucerne silage-based total mixed ration. Diets were formulated to contain a 50:50 forage:concentrate ratio [dry matter (DM) basis] and be isonitrogenous and contain equal levels of neutral detergent fiber (320 g/kg). The forage portion of the offered diets was composed of maize and lucerne silage DM in proportions (wt/wt) of either 25:75 (high lucerne; HL) or 75:25 (low lucerne; LL). Second-cut lucerne was harvested and conserved as silage at either a long (L) or a short (S) chop length (geometric mean particle lengths of 9.0 and 14.3 mm, respectively). These variables were combined in a 2 × 2 factorial arrangement to give 4 treatments (HLL, HLS, LLL, LLS), which were fed in a 4 × 4 Latin square design study to 4 rumen-cannulated, multiparous, Holstein dairy cows in mid lactation. Effects on DM intake, chewing behavior, rumen volatile fatty acid concentration, rumen pH, rumen and fecal particle size, milk production, and milk fatty acid profile were measured. Longer chop length increased rumination times per kilogram of DM intake (+2.8 min/kg) relative to the S chop length, with HLL diets resulting in the most rumination chews. Rumen concentrations of total volatile fatty acids, acetate, and n-valerate were higher for the HLS diet than the other 3 diets, whereas rumen propionate concentration was lowest for the HLL diet. Physically effective fiber (particles >4 mm) percentage in the rumen mat was increased when L chop length was fed regardless of lucerne inclusion rate. No effect of treatment was observed for milk yield, although milk protein concentration was increased by L for the LL diet (+1.6 g/kg) and decreased by L for the HLL diet (?1.4 g/kg). Milk fat concentrations of total cis-18:1 (+3.7 g/100 g of fatty acids) and 18:3 n-3 (+0.2 g/100 g of fatty acids) were greater with HL. In conclusion, longer lucerne silage chop length increased time spent ruminating per kilogram of DM intake, but had no effect on rumen pH in the present study. Increasing dietary lucerne inclusion rate had no effects on rumination activity or rumen pH, but decreased the ratio of n-6:n-3 polyunsaturated fatty acid concentrations in milk fat.     

Effects of intraruminal infusions of mineral salts on volatile fatty acid production in steers fed high-grain and high-roughage diets

Four rumen fistulated Holstein steers were used to assess the effects of intraruminal salt infusions on various rumen characteristics including volatile fatty acid production rates. In the first experiment, the basal diet consisted of 75% concentrate and 25% corn silage (high-grain diet). The experimental design was a 4 X 4 Latin square in which the four treatments were: 1) intraruminal infusion of 8 liters of water (control) or 8 liters of water plus 2) 288 g sodium bicarbonate, 3) 200 g sodium chloride, or 4) 600 g sodium chloride. In the second experiment, procedures were the same except the basal diet consisted of 64% alfalfa hay and 18% each of corn silage and concentrate (high-roughage diet). When the high-grain basal diet was fed, intraruminal infusions of mineral salts increased dilution rate of rumen fluid. Total fluid flow from the rumen also was increased by salt infusions with sodium bicarbonate and the most sodium chloride from (600 g/day) exerting greatest effects for both dietary regimens. Salt infusions reduced the molar percentage of rumen propionate and increased the molar percentage of acetate when the high-grain diet was fed. These same treatments were without effect on molar percentages of rumen acids when the high-roughage diet was fed. The change in the molar percentages of acetate and propionate on the high-grain ration was solely from reduction in propionate production. The lower production of propionate, from salt infusions, may have occurred because of the washout of readily fermentable materials. Dry matter disappearance from feeds placed in dacron bags and suspended in the rumen was unaffected by infusion of mineral salts.     

Effects of calcium salts differing in fatty acid composition on duodenal and milk fatty acid profiles in dairy cows

Ruminal biohydrogenation of fatty acids (FA) was studied in vivo in relation with the fermentation pattern in the rumen and milk secretion. Calcium salts (Ca salts) of palm oil (diet 1) or rapeseed oil (diet 2) were given to dairy cows (about 650 g day^?1) in a diet based on maize silage. Significant variation in propionate concentration was observed among diets. Rumen pH and total volatile fatty acids (VFA) did not change. Duodenal FA pattern was analysed throughout the day. With diets 1 and 2, linoleic acid was to a large extent biohydrogenated: calculations of ruminal biohydrogenation were equal to 63.6 and 74.0% for diets 1 and 2, respectively. No difference between diets was observed in milk production, fat and protein percentages. The percentages of stearic and octadecenoic FA in milk were higher and the percentage of palmitic acid was lower with Ca salts of rapeseed oil FA than with Ca salts of palm oil FA.     

Changes in ruminal bacterial community composition following feeding of alfalfa ensiled with a lactic acid bacterial inoculant

Some silage inoculants help to improve silage quality and promote an increase in milk production, possibly through altering the rumen microflora. We hypothesized that rumen bacterial community composition (BCC) would be different in cows fed alfalfa ensiled with the inoculant Lactobacillus plantarum MTD/1 (LP) compared with those fed alfalfa ensiled without the inoculant (Ctrl). Eight ruminally cannulated Holstein cows were allotted to 2 diets (Ctrl or LP) in a double crossover design with four 28-d periods. Diets were formulated to contain (% dry matter basis) 28.0% neutral detergent fiber and 16.2% crude protein, and contained alfalfa silage, 50.9; corn silage, 20.6; high-moisture shelled corn, 21.4; soy hulls, 4.7; plus minerals and vitamins, 2.4. Ruminal digesta were collected just before feeding on 3 consecutive days near the end of each period, and were separated into solid and liquid phases. Microbial DNA was extracted from each phase, amplified by PCR using domain-level bacterial primers, and subjected to automated ribosomal intergenic spacer analysis. The pH was 4.56 and 4.86 and the lactate-to-acetate ratio 9.8 and 4.4, respectively, for the treated and untreated alfalfa silages. Dry matter intakes and milk production data were not influenced by diets but showed a cow effect. Total volatile fatty acids (mM) tended to be greater for LP compared with Ctrl. Individual volatile fatty acids were not influenced by diets but showed a significant cow effect. Ruminal acetate (mol/100 mol) and acetate-to-propionate ratio were lower and propionate (mol/100 mol) greater for the 2 milk fat-depressed (MFD; <3.2% fat content) cows compared with the other 6 cows. Correspondence analysis of the 265 peaks in the automated ribosomal intergenic spacer analysis profile across the 188 samples revealed that the first 2 components contributed 7.1 and 3.8% to the total variation in the profile. The ordination points representing the liquid and solid phases clustered separately, indicating that these phases differed in BCC. The analysis of similarity data showed differences between Ctrl and LP. The lactic acid bacterial counts (log(10) cfu/g of wet silage) were 3.94 and 4.53 for the untreated and treated silage, respectively, at ensiling. The relative population size (RPS) of L. plantarum, determined by real-time PCR of 16S rRNA gene copies, was greater in LP compared with Ctrl. The ordination points corresponding to certain individual cows clustered separately, and the most distinctive bacterial communities were those associated with MFD cows. The RPS of Megasphaera elsdenii was greater in 1 of the 2 MFD cows, although mean RPS of M. elsdenii did not differ between the treatments. In addition to the differences in rumen BCC between LP and Ctrl, MFD cows also displayed differences in BCC compared with cows with normal milk fat yield.     

Effects of intraruminal and intra-abomasal additions of cod-liver oil on milk fat production in the cow.

Four Holstein cows were used in a modified switchback design to show the effect on milk-fat synthesis of (1) control diet, (2) 29.23, 3.92, 6.48, 30.65, 3.44 control diet plus 255 g/day of cod-liver oil in rumen, and (3) control diet plus 225 g/day of cod-liver oil in abomasum. Mean milk yield (kg/day), fat production (kg/day), and milk-fat percentage were (1) 21.87, .79, 3.63; (2) 22.99, .70, 3.05; and (3) 23.02, .75, 3.28. Compared to the post-treatment control period, only one cow decreased in milk-fat percentage on 3 while all cows decreased in milk-fat percentage on 2. Proportions of carbons 16:0, 16:1, 18:0, 18:1, 18:2, and trans-monoene fatty acids of the milk fat were (1) 30.31, 3.24, 10.15, 30.48, 2.59, 7.91; (2) 26.37; and (3) 26.30, 3.72, 10.56, 30.10, 2.96, 9.84. Proportions of rumen volatile fatty acids were not significantly affected by treatment. Proportions of carbons 16:0, 18:0, 18:1, 18:2, and 18:3 fatty acids in the rumen ingesta were (1) 17.28, 47.92, 21.71, 10.59, 2.46; (2) 19.55, 25.90, 37.21, 11.97, 5.39; and (3) 16.90, 50.80, 19.66, 9.11, and 3.23. Fatty acid composition of blood-serum phospholipids were affected by treatment.     

Stabilisation of protein and oil in fish silage for use as a ruminant feed supplement

Fish silage was prepared from 96.5% offal obtained from Atlantic cod fillet processing and 3.5% (by wt) formic acid. The fish silage became an homogeneous liquid of low viscosity in 36–58 h at 20°C; however, the oil and protein components continued to be hydrolysed for several months. Addition of formaldehyde to fish silage (0.25 or 0.39% by wt) after liquefaction was complete, served to prevent continued protein hydrolysis and oxidative rancidity of the oil. It also decreased the development of ‘off-odours’, and the formation of total volatile bases. Fish silage was readily absorbed by hay at a ratio of 1.5 parts silage to 1.0 parts hay by weight; the product is referred to as ‘haylage’. Voluntary intake by wethers of ‘haylage’ prepared from de-oiled, formaldehyde-treated fish silage was better than for ‘haylage’ prepared from untreated fish silage. The crude protein content of ‘haylage’ rations was more than satisfactory for fattening lambs, although the energy content of ‘haylage’ rations may be a limiting factor. Retention of fish oil in the silage to increase the energy content of rations was unsuccessful because voluntary feed intake was depressed. The addition of formaldehyde to fish silage is advantageous when the product is to be fed to ruminant livestock since protein and lipid degradation in the feed, and also possibly in the rumen, are minimised and voluntary intake of ‘haylage’ by sheep is increased.     

苏尼特羊羊尾油的理化性质测定与分提后脂肪酸组成分析

为提高羊尾巴的利用价值,运用真空抽提法从苏尼特羊羊尾巴中提取羊尾油,并对其进行理化性质的测定。另外,将羊尾油进行干法分提,分为固脂、液油两部分,采用气相色谱-质谱法对原油、固脂与液油脂肪酸组成进行分析。结果表明：苏尼特羊尾油的水分及挥发物含量为8.63%,酸值(KOH)为0.67 mg/g,皂化值(KOH)为180.1 mg/g,碘值(I)为45.48 g/100 g; 3种油样都检测出16种脂肪酸,主要含有棕榈酸、油酸和硬脂酸,液油的不饱和脂肪酸含量较原油和固脂的高。     

Rumen ciliate protozoa: effects on digestion in the stomach of sheep

Six wethers, each fitted with a rumen cannula and duodenal reentrant cannula, were used to study effects of ciliate protozoa on rumen digestion and metabolism. A corn: corn silage (1:1) diet was fed for two periods. During the first period, defaunation was attempted with nonyl phenol ethylene oxide. Defaunation was complete in three sheep and partial in the other three sheep in which a reduced population of a small Entodinium sp. was observed. During the second period the sheep were inoculated with ciliate protozoa, which established a large population in all animals. Apparent digestion in the stomach of organic matter and starch was higher when a large protozoal population was present. Amino acid flow through the duodenum was greater in defaunated animals. A large population of ciliates was associated with increases in both rumen ammonia and plasma urea but had a stabilizing effect on ruminal pH. Volatile fatty acids were higher in the defaunation period, but there were only small differences of molar proportions of the acids between the two periods. Effects of ciliate protozoa are related to animal performance.     

Effect of supplemental tallow on performance of dairy cows fed diets with different corn silage:alfalfa silage ratios

A study was conducted to investigate the response to supplemental tallow of lactating cows fed basal diets with different alfalfa silage:corn silage ratios. We postulated that supplemental tallow will have decreasing negative effects on rumen fermentation, dry matter intake (DMI), and milk fat percentage as the dietary ratio of alfalfa silage:corn silage is increased. Eighteen Holstein cows averaging 134 +/- 14 d in milk were used in a replicated 6 x 6 Latin square design with 21-d periods. Treatments were arranged as a 2 x 3 factorial with 0 or 2% tallow (DM basis) and three forage treatments: 1) 50% of diet DM as corn silage, 2) 37.5% corn silage and 12.5% alfalfa silage, and 3) 25% corn silage and 25% alfalfa silage. Cows were allowed ad libitum consumption of a total mixed ration. Diets were formulated to contain 18% crude protein and 32% neutral detergent fiber. No fat x forage treatment interactions were observed. Fat supplemented cows had lower DMI and produced more milk with less milk fat content relative to non-supplemented cows. Concentration of trans-octadecenoic acids was higher in milk fat of tallow-supplemented cows. Tallow supplementation had no effect on ruminal pH and acetate:propionate ratio, but tended to decrease total volatile fatty acid (VFA) concentration in the rumen. Increasing the proportion of alfalfa silage increased DMI, milk fat percentage, and milk fat yield regardless of the fat content of the diet. Total VFA concentration and acetate:propionate ratio in the rumen were increased in response to higher levels of alfalfa in the diets. These results suggest that replacing corn silage with alfalfa silage did not alleviate the negative response of dairy cows to tallow supplementation at 2% of diet DM.     

Effects of barley silage chop length on productivity and rumen conditions of lactating dairy cows fed a total mixed ration

Barley silage, cut at the early dough stage, was chopped long (19 mm) or short (10 mm), ensiled, and incorporated into total mixed rations (TMR). The TMR contained (dry matter [DM] basis) either 58.0 or 41.4% concentrate and either short- or long-chopped barley silage. Reducing chop length of barley silage decreased the proportion (asis basis) of TMR particles retained by the 8- and 19-mm screens of the Penn State Particle Separator (PSPS) from 66.9 to 52.7% in the high concentrate TMR and from 74.8 to 60.9% in the low concentrate TMR. Chop length reduction decreased dietary physically effective fiber, calculated as the NDF retained by the 8- and 19-mm screens of the PSPS, from 29.2 to 25.2% DM in the high concentrate TMR and from 34.9 to 30.6% DM in the low concentrate TMR. Reduction in chop length did not affect rumen pH, total rumen volatile fatty acids, milk yield, and milk composition, but increased DM intake from 19.4 to 20.1 kg/d at the high level of concentrate and from 16.9 to 17.7 kg/d at the low level of concentrate and increased rumen propionate. Increasing the concentrate inclusion rate reduced rumen pH from 6.52 to 6.35, did not affect total volatile fatty acids, reduced the acetate-to-propionate ratio from 3.1 to 2.7, increased milk yield from 28.7 to 31.3 kg/d, reduced milk fat content from 3.48 to 2.94%, and increased milk protein content from 3.11 to 3.27% across chop lengths.     

Effect of arachis oil on the conservation of heavily wilted herbage ensiled in plastic containers. I. Effect on silage fermentation quality, nutritive value, nutrient losses and intake by sheep

Arachis oil was added to heavily wilted herbage of approximately 40% dry matter, before ensiling in polyethylene containers. The oil was added at a mean level of 4·16% of the total dry matter ensiled. The mean dry matter loss from the two control and the two oil-treated silages teas approximately 13%. There was a lower loss as inedible waste in the oil-treated silages and mould growth appeared to be inhibited by the oil. There was a lower percentage of butyric acid and propioiuc acid in the oil-treated silages than in the control silages, this effect being statistically significant. Ensiling resulted in a greater fall in digestibility of the control material than in the oil-treated material. The oil-treated silages had higher metabolisable energy contents than the control silages but the dry matter intakes of both silages by sheep were low.     

Interaction of molasses and monensin in alfalfa hay- or corn silage-based diets on rumen fermentation, total tract digestibility, and milk production by Holstein cows

Sugar supplementation can stimulate rumen microbial growth and possibly fiber digestibility; however, excess ruminal carbohydrate availability relative to rumen-degradable protein (RDP) can promote energy spilling by microbes, decrease rumen pH, or depress fiber digestibility. Both RDP supply and rumen pH might be altered by forage source and monensin. Therefore, the objective of this study was to evaluate interactions of a sugar source (molasses) with monensin and 2 forage sources on rumen fermentation, total tract digestibility, and production and fatty acid composition of milk. Seven ruminally cannulated lactating Holstein cows were used in a 5 × 7 incomplete Latin square design with five 28-d periods. Four corn silage diets consisted of 1) control (C), 2) 2.6% molasses (M), 3) 2.6% molasses plus 0.45% urea (MU), or 4) 2.6% molasses plus 0.45% urea plus monensin sodium (Rumensin, at the intermediate dosage from the label, 16 g/909 kg of dry matter; MUR). Three chopped alfalfa hay diets consisted of 1) control (C), 2) 2.6% molasses (M), or 3) 2.6% molasses plus Rumensin (MR). Urea was added to corn silage diets to provide RDP comparable to alfalfa hay diets with no urea. Corn silage C and M diets were balanced to have 16.2% crude protein; and the remaining diets, 17.2% crude protein. Dry matter intake was not affected by treatment, but there was a trend for lower milk production in alfalfa hay diets compared with corn silage diets. Despite increased total volatile fatty acid and acetate concentrations in the rumen, total tract organic matter digestibility was lower for alfalfa hay-fed cows. Rumensin did not affect volatile fatty acid concentrations but decreased milk fat from 3.22 to 2.72% in corn silage diets but less in alfalfa hay diets. Medium-chain milk fatty acids (% of total fat) were lower for alfalfa hay compared with corn silage diets, and short-chain milk fatty acids tended to decrease when Rumensin was added. In whole rumen contents, concentrations of trans-10, cis-12 C_18:2 were increased when cows were fed corn silage diets. Rumensin had no effect on conjugated linoleic acid isomers in either milk or rumen contents but tended to increase the concentration of trans-10 C_18:1 in rumen samples. Molasses with urea increased ruminal NH₃-N and milk urea N when cows were fed corn silage diets (6.8 vs. 11.3 and 7.6 vs. 12.0 mg/dL for M vs. MU, respectively). Based on ruminal fermentation characteristics and fatty acid isomers in milk, molasses did not appear to promote ruminal acidosis or milk fat depression. However, combinations of Rumensin with corn silage-based diets already containing molasses and with a relatively high nonfiber carbohydrate:forage neutral detergent fiber ratio influenced biohydrogenation characteristics that are indicators of increased risk for milk fat depression.