Effect of cultivars on in vitro and ruminal degradation of the nitrogen fraction in birdsfoot trefoil silage

Experiments were carried out to determine the effects of tannin content on N fractions and DM digestibility of birdsfoot trefoil harvested at 20% bloom stage. Five trefoil cultivars, harvested in both June and August, were used: Upstar, Mirabel, Empire, Leo, and Bt-8861. Forage was ensiled in 1.3-kg laboratory silos for 60 d with 4 silos per cultivar and harvest. Concentrations of DM and tannin in forage were determined prior to ensiling, and N fractions, DM digestibility, and pH in silage were also determined. Tannin concentration and protein N content of silage were lower in Empire than in the other cultivars. Ruminal degradability of DM and CP of Empire (low tannin) and Upstar (high tannin) birdsfoot trefoil were estimated with two fistulated cows using nylon bags that were incubated < or = 96 h. The DM-soluble fraction of Empire was significantly lower than that of Upstar for the first harvest only. This difference was partly due to the high proportions of dry shoots. The CP-soluble fraction of Empire was higher than that of Upstar, but the percentage of CP that was potentially degradable in the rumen was lower for Empire. This difference could result in different CP availability over time even for similar effective degradability of CP. Tannin had no additional effect on total CP degradability in the rumen.

Effect of feeding fermented, ammoniated, condensed whey permeate on intake, digestibility, rumen fermentation, and acid-base balance in sheep

Nine DLS rumen-cannulated wethers (69 kg avg BW) were used to study the effects of dietary supplementation with two types of fermented, ammoniated, condensed whey permeate on performance, rumen physiology and acid-base status in sheep fed high-grain diets. Sheep were fed three isonitrogenous (16% CP) diets according to a triple 3 × 3 Latin square design, with three 21-d periods each. One whey permeate contained ammonium lactate (AL) while the other contained ammonium propionate (AP). Urea was used as a source of NPN in the control diet (C). Diets, offered ad libitum, contained 78% barley and 18% dehydrated alfalfa meal. Dry matter and digestible energy intakes were about 15% higher for diets AL and AP than for diet C (P < 0.05). Dry matter digestibility was not affected by the treatments, whereas organic matter and energy digestibilities tended to be higher for diet AP than for diet AL (P < 0.07). Rumen fermentation was not affected by the treatments. Over a 4-h post-feeding period, sheep fed diet C had higher plasma concentrations of lactate (P < 0.06) and acetate (P < 0.04) but lower levels of plasma propionate (P < 0.06) than sheep fed the AL and AP diets. Plasma propionate 2 h after feeding was higher in sheep fed the AL diet versus the AP diet (P < 0.01). Sheep blood was mildly alkalotic despite the fact that sheep were fed a high-grain diet. The two types of fermented, ammoniated and condensed whey permeate were found to be good sources of NPN. Key words: Whey, rumen fermentation, acid-base balance, sheep

Ruminal fermentation and digestion in lactating cows fed grass silage with protein and energy supplements

Four multiparous Holstein cows were used in a 4 x 5 incomplete Latin square design to study the effects of different dietary sources of energy and protein on digestion, ruminal fermentation, and degradability in cows fed high moisture grass silage. The five treatments were an all silage diet (control); silage and concentrate containing soybean meal fed with corn, beet pulp, or a mixture (50:50 on a DM basis) of oats and barley; and fish meal fed with beet pulp. Concentrates were fed between .70 and .76% of BW to give similar CP and NEL intakes. Total DMI and milk production were lower for unsupplemented than for supplemented cows, but digestion and ruminal fermentation did not differ. Digestibility of fiber and concentration of total VFA were higher for cows fed corn than for those fed the mixture of oats and barley, but starch source had no effect on total DMI or milk production and composition. Energy source had no effect on total DMI or milk production and composition. Digestibility of DM and NDF was higher, and ruminal concentration of NH3 N and degradability of silage N tended to be lower, for cows fed beet pulp than for those fed starch, suggesting an improvement in the microbial protein synthesis in the rumen when beet pulp was fed instead of starch.

Milk production and intake of lactating cows fed grass silage with protein and energy supplements

Primiparous (n = 8) and multiparous (n = 24) Holstein cows averaging 591 kg of BW (SE = 12) were allotted at 2 wk postpartum to eight blocks of 4 cows each on the basis of calving date and parity. Cows were fed timothy silage for ad libitum intake. The experiment was carried out between wk 4 and 15 of lactation. Cows within each block were assigned randomly to a concentrate containing soybean meal fed with corn, beet pulp, or a mixture of oats and barley (50: 50 on a DM basis) or fish meal fed with beet pulp. Concentrates were fed at about .8% of BW. The four treatments were designed to give similar CP and NEL intakes from the concentrate. Starch degradability and energy source (non-structural vs. structural carbohydrates) had no effect on total DMI of cows supplemented with soybean meal. Total DMI was similar for cows fed beet pulp with soybean meal or fish meal. Production of 4% FCM was on average 3.5 kg/d higher for cows fed beet pulp than starch. All cows gained BW. In low concentrate diets, beet pulp compared with starch improved N utilization of high moisture timothy silage by increasing production of 4% FCM without affecting total DMI; however, protein degradability does not seem to be important in low concentrate diets.

Digestion characteristics of beef steers fed silage and different levels of energy with or without protein supplementation

Six large-framed crossbred steers averaging 262 kg were used in a 6 x 7 incomplete Latin square design to study the effect of feeding a source of readily available energy (molasses) in combination with highly degradable protein (canola meal) on ruminal characteristics, digestibility, and in situ disappearance of DM and N. The seven dietary treatments were offered for ad libitum consumption and consisted of 1) timothy silage alone or mixed (on a DM basis) with 2) 7.5% molasses, 3) 15% molasses, 4) 7.5% canola meal, 5) 5.5% canola meal and 7.5% molasses, 6) 3.6% canola meal and 15% molasses, or 7) 15% canola meal. The total N content of supplements containing 7.5% canola meal, 5.5% canola meal and 7.5% molasses, and 3.6% canola meal and 15% molasses was similar. Molasses supplementation decreased (P < .05) ruminal ammonia N concentration and digestibility of energy and fiber. Canola meal supplementation increased (P < .05) N and energy digestibility but decreased ADF digestibility compared with feeding unsupplemented timothy silage. Feeding 15% compared with 7.5% canola meal increased (P = .05) DM digestibility and tended (P = .07) to increase energy digestibility. Combining 7.5% molasses and 5.5% canola meal did not improve DM digestibility, but adding 15% molasses decreased (P < .05) energy and fiber digestibility of the diet, which may explain lower ADG obtained for beef steers fed such levels of molasses in other research.

Growth and carcass characteristics of beef steers fed silage and different levels of energy with or without protein supplementation

Fifty-six large-framed crossbred steers averaging 227 kg were used in an experiment including a growing period (24 wk) and a finishing period ending when the steers had approximately 4 to 10 mm of fat thickness (Canadian grade A1). Steers were individually fed and assigned to a completely randomized design with seven treatments for the growing period. From the end of the growing period until slaughter, all steers received the same basal diet. Half of the steers from each treatment used in the growing period received a supplement containing protein and the other half a supplement containing protein and fat. Treatments during the growing phase consisted of 1) timothy silage alone or mixed (on a DM basis) with 2) 7.5% molasses, 3) 15% molasses, 4) 7.5% canola meal, 5) 5.5% canola meal and 7.5% molasses, 6) 3.6% canola meal and 15% molasses, or 7) 15% canola meal. The total N intake from supplements 2, 5, or 6 was similar. Compared with silage fed alone, canola meal supplementation increased (P < .05) ADG, whereas molasses had no effect. Combining molasses and canola meal did not improve ADG compared with feeding only canola meal on an isonitrogenous basis. Canola meal supplementation compared with feeding only silage during the growing phase reduced (P < .05) days on feed, and molasses tended (P = .059) to reduce it. Carcass data were generally similar among treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Intake, digestibility, and ruminal degradability of shredded hay

Thirty-two Outaouais intact male lambs averaging 39.1 kg were assigned randomly to a 2 x 2 factorial arrangement of treatments consisting of two forages and two methods of harvesting to determine intake and digestibility. The four treatments fed during the experiment consisted of alfalfa and timothy hays harvested with either a prototype mat maker or a conventional mower conditioner. Hays were fed for ad libitum intake for the entire experiment, and data on digestibility and intake were collected for 9 d after a 21-d adaptation. Ruminal degradability of DM, N, and ADF of hays was estimated with two fistulated cows using nylon bags incubated up to 96 h. Harvesting with the prototype mat maker compared with the conventional mower generally increased intake and digestibility of alfalfa and timothy hays. Ruminal degradability of DM and the potentially degradable fraction of DM and ADF was higher when hay was harvested with the prototype mat maker than with the conventional mower. The increased digestibility of hay harvested with the prototype mat maker could be explained by the increased digestibility in the rumen because harvesting with the prototype mat maker increased the potentially degradable fraction of DM and ADF. These results suggest that the digestible energy content of hay was increased by shredding.

Growth and carcass quality of prolific crossbred lambs fed silage with fish meal or different amounts of concentrate

Sixty Romanov x Dorset (RVDP) and sixty Romanov x Suffolk (RVSU) male lambs were used in a 2 x 5 factorial arrangement of treatments including two breed crosses and five diets to determine the effect of breed crosses on performance and to compare growth and carcass characteristics of lambs. Diets consisted of an all-silage diet, silage supplemented with 100 g of fish meal.animal-1.d-1, or silage supplemented daily with concentrate at either 200 g or 400 g per animal, or ad libitum intake. Lambs were fed from an initial weight of 23 kg to a slaughter weight of 45 kg. There was no interaction (P > .10) between diet and breed for any parameter measured. Silage DMI was decreased (P < .05) by supplementation, but total DMI was similar among diets. The ADG was increased by fish meal and concentrate supplementation, with higher (P < .05) ADG observed with ad libitum access to concentrate. Lambs that had ad libitum access to concentrate had an improved gain:feed and required less time to reach market weight but had more carcass fat than lambs fed other diets. Lambs fed only silage had a higher percentage of carcass with poorer muscling than others. The highest percentage of carcasses with excellent to good muscling, normal fat covering, and grades A1 and A2 was obtained with fish meal supplementation. Lambs from the RVSU-crossbreed had better ADG than RVDP lambs but carcass quality of RVDP lambs was better than that of RVSU lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo and in vitro gastric emptying of milk replacers containing soybean proteins

Gastric digestion of three milk replacers for which protein was provided either exclusively by milk powder or partially (50%) by heated soybean flour or soybean protein concentrate was studied in vivo and in vitro. In vivo gastric emptying of protein fractions of the diets was measured in six preruminant calves fitted with reentrant duodenal cannulas and used in a double 3 x 3 Latin square design. In vitro gastric emptying was studied after hydrochloric acid and rennet digestion in an artificial stomach. In vivo and in vitro flow rates of 12% TCA-insoluble N and total N were higher for the soybean diets than for the milk protein diet, indicating that the incorporation of soybean protein prevented casein from clotting. Because of this faster gastric emptying, proteolysis in the stomach was reduced. However, gastric emptying of NPN (12% TCA-soluble N) was significantly decreased only in vitro. No difference existed between the two milk replacers containing either soybean flour or soybean protein concentrate. In vivo and in vitro results were correlated, suggesting that the in vitro method could be used to predict gastric digestion of protein fractions in vivo.

Milk yield, intake, and blood traits of lactating cows fed grass silage conserved under different harvesting methods

Thirty-two Holstein cows (8 primiparous) were assigned to negative control or to one of three treatments to assess three forage harvesting and conservation techniques. Forage was harvested as low moisture silage by either a cylinder-type forage harvester, a self-loading forage harvester, or a round baler. Treatment diets were fed from wk 4 to 15 of lactation and consisted of silages harvested by the respective methods supplemented with concentrate at 1.1% of BW. Unsupplemented silage harvested by a cylinder-type forage harvester was used as a control. Daily DMI was higher for cows fed supplemented heap silage cut with either a cylinder-type forage harvester (23.7 kg) or a self-loading forage harvester (22.6 kg) than for cows fed the control (20.0 kg) or supplemented round bale silage (20.1 kg). Milk yield was highest for cows fed supplemented heap silage cut with a cylinder-type forage harvester (26.6 kg/d) and lower for those fed supplemented heap silage cut with a self-loading forage harvester (22.7 kg/d) or the control (20.8 kg/d). Milk composition and digestibilities of DM, N, ADF, and energy were similar among treatments. Postfeeding NEFA concentration decreased more for control cows than for those fed supplemented silage, which was related to greater BW loss. The high milk yield for cows fed supplemented heap silage cut with a cylinder-type forage harvester could be related to a high DMI and low BW gain.

Performance of growing steers fed either hay or silage supplemented with canola or fish meal

One hundred and eighty-six crossbred steers (194.4 ± 1.5 kg) were used to determine the effect of protein supplementation of medium-quality grass hay or silage on performance during wintering and compensatory growth during the grazing period. All steers received the hay or the silage ad libitum during the 182-d wintering period. They were also fed fixed quantities of one of three supplements: C, a control with no supplemental protein; CM, a canola meal; and FM, a fish meal containing supplements. Daily amounts of supplementation were fixed to supply to each steer the same amount of barley (85 g 100 kg−1 BW), of dry molasses (15 g 100 kg−1 BW) and of minerals, vitamins and Bovatec (10 g 100 kg−1 BW). The protein supplements CM and FM supplied the equivalent of 95 g of crude protein daily 100 kg−1 BW compared with 15 g 100 kg−1 BW for the control. Expressed as g kg−0.75, forage DM intake was 13.3% higher when fed as hay than as silage (P < 0.0001). Protein supplementation increased forage DM intake when fed as hay (P < 0.02) but not when fed as silage. Average daily gains (ADG) tended to be 5.8% higher for steers fed hay than for those fed silage (P = 0.06). Protein supplementation markedly improved ADG (P < 0.0001). When hay was fed, no differences were found in ADG between CM and FM supplementation; however, FM supplementation produced higher ADG than CM when silage was fed (P < 0.001). Feed efficiency was not affected by the type of forage fed, but it was higher for steers receiving protein supplementation (P < 0.001), the effect being more evident when the forage was fed as silage (P < 0.001) than when fed as hay (P = 0.07). Compensatory gains were obtained when the steers were taken out to pasture in early spring; steers fed silage, which obtained smaller ADG during wintering, showed higher ADG in pasture (P < 0.01). After 62 d grazing, the effect of protein supplementation during winter on body weight had almost disappeared. Key words: Protein supplementation, forages, cattle, growth

Feed utilization of beef steers fed grass as hay or silage with or without nitrogen supplementation

Six Hereford steers averaging 256 kg were used in a 2 x 3 factorial arrangement within a 6 x 6 Latin square design to study the effect of forage conservation (silage vs hay) and N supplementation (0, 200 g of fish meal plus 43 g of urea, or 400 g of fish meal) on ruminal characteristics, digestibility, blood urea, and in situ degradability of DM, N, and ADF. Dry matter intake of forage and total DMI did not differ among treatments (P greater than .05) and averaged 5.3 and 5.5 kg, respectively. Steers fed silage had greater (P less than .05) pH and concentrations of ammonia N, isobutyrate, isovalerate, and valerate in the rumen than in the rumen of those fed hay. Nitrogen supplementation increased (P less than .05) concentrations of total VFA and valerate in the rumen. Digestibility of N and ADF was greater (P less than .05) for silage than for hay, and N supplementation increased digestibility of N. Plasma urea concentrations were greater (P less than .05) for steers fed silage than for those fed hay. These data suggest that feed utilization is better with silage than with hay and is increased by N supplementation.

In situ degradability of fresh grass and grass conserved under different harvesting methods

The effects of forage conservation and harvesting method on DM and CP degradability of grass cut at the boot stage were determined using nylon bags incubated in the rumen of two fistulated lactating cows. Samples of fresh grass, wilted grass prior to and after ensiling in a stack silo and cut with either a cylinder-type forage harvester (11.3 mm of length cut) or a self-loading wagon (42.4 mm of length cut), wilted grass prior to and after ensiling in large round bales, and grass hay were obtained from the same field and used for determination of DM and CP degradability. The DM-soluble fraction of fresh grass was significantly lower than that of wilted grass and silage, but it was higher than that of hay. In general, the potentially degradable fraction of all treatments was related inversely to the readily soluble fraction in water. The effective degradability of DM of fresh grass was similar to that of hay but was lower than that of wilted grass and silage. The effective degradability of DM of silage was higher than that of wilted grass and hay. The disappearance rate of CP of fresh grass was similar to that of wilted grass, hay, and silage. Silage had a lower disappearance rate of CP than wilted grass. The effective degradability of CP was similar for fresh and wilted grasses. Protein degradability was greater for silages than for fresh and wilted grasses. Protein degradability of hay was similar to that of fresh grass and wilted grass.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo and in vitro gastric emptying of protein fractions of milk replacers containing whey proteins

In vivo and in vitro gastric emptying of protein fractions of three milk replacers containing either milk protein (control), a mixture (50:50 on a CP basis) of milk protein and native whey protein concentrate, or a mixture (50:50 on a CP basis) of milk protein and heated whey protein concentrate was studied. In vivo gastric emptying was measured in three preruminant calves fitted with reentrant duodenal cannulas and used in a 3 x 3 Latin square design. In vitro gastric emptying was determined after enzymatic digestion in an artificial stomach. In vivo and in vitro flow rates of protein N (12% TCA-insoluble N) and total N were higher for milk replacers containing whey proteins than for control. Gastric emptying of NPN (12% TCA-soluble N) was slightly higher for diets containing whey proteins than for that containing milk proteins. Gastric emptying of all protein fractions was similar for the two milk replacers containing whey proteins. In vivo and in vitro results were significantly correlated, suggesting that the in vitro method reproduced conditions for proteolysis and could be used to predict gastric digestion of protein fractions.

Digestibility and performance of dairy bulls fed corn and grass silages with various sequences and levels of barley

Sixty Canadian Holstein male calves (mean weight 261 kg), previously fed all-concentrate diets, were allocated to one of six different sequences of barley supplementation. Rolled barley was provided in the diet at three levels (0, 17 and 34% on a DM basis) with either grass or corn silages, and fed as a total mixed ration for 91, 77 and 70 d during periods 1,2, and 3, respectively, to ensure consumption of 330 kg of barley per animal for the entire experiment. Barley supplementation in the last period improved average daily gain over the whole experiment by 0.223 kg d−1 (P = 0.0154), and feed efficiency by 55% (P = 0.0062) compared to inclusion of barley in the silage mixtures during the first period. Feed efficiency improved with concentrate supplementation of both silages (P ≤ 0.0001), but the improvement with grass silage was greater than with corn silage (P = 0.0041). Dry matter and energy digestibilities were not affected by feed sequences (P = 0.1025, P = 0.0833, respectively), but they were higher for mixed diets than for pure silage (P = 0.0186, P = 0.0218, respectively). Dry matter intake was 0.81 kg d−1 higher (P ≤ 0.0001) when concentrate was added to the diet. These results suggest that energy feeds such as barley are more efficiently used in the last part of growth. This experiment demonstrates the feasibility of switching grain-fed calves to roughage diets. Key words: Barley, dairy bulls, energy distribution, corn silage, grass silage

Source and feeding level of nitrogen on growth and carcass characteristics of beef steers fed grass as hay or silage

Sixty medium-framed Hereford steers averaging 243 kg were used in an experiment including a growing period (28 wk) and a finishing period ending when the animals had approximately 4 to 10 mm of fat thickness (Canadian grade A1). Steers were assigned randomly to a 2 x 3 factorial arrangement of treatments for 28 wk (growing period). From the end of the growing period until slaughter, all steers received the same diet to study the residual effect of treatments fed during growth. Treatments during the growing phase consisted of two types of forage conservation (silage or hay) and three levels of protein supplement (0, 200 g of fish meal plus 43 g of urea, or 400 g of fish meal). There was an interaction (P less than .05) between forage conservation and protein supplementation for BW gain during the growing phase; the greatest gain was by steers fed silage and 400 g of fish meal (.87 kg/d). There was no difference in BW gain among animals fed the hay diets, which averaged .75 kg/d. Body weight gain during the finishing phase, and for the overall experiment, was affected only by forage conservation; greater gains were made by steers fed silage during the growth phase. Protein supplementation did not affect performance in either the finishing phase or overall. Carcass composition did not differ among treatments, and time spent on the finishing phase tended to be less (P less than .08) for steers fed silage plus 400 g of fish meal during the growth phase.

Duodenal flow of nitrogen following protozoal inoculation of fauna-free sheep fed a diet supplemented with casein or soybean meal

Fauna-free sheep, equipped with a rumen cannula and a duodenal re-entrant cannula, were fed a corn silage diet supplemented with casein (CA diet) or soybean meal (SBM diet). Eighteen days later the sheep were inoculated via the rumen cannula with a mixed population of ciliate protozoa. Rumen fluid and duodenal digesta were sampled for 4 d before the inoculation and for 13 d following the inoculation. A stable protozoal population was established within 8 d. Protozoa increased (P < 0.05) the digestion of organic matter in the stomach of sheep fed both the CA and the SBM diet, but the effects of supplemental protein and protein × protozoa interaction were not significant (P > 0.05). The stomach digestion of acid detergent fibre was not affected (P > 0.05) by protozoa or by the source of supplementary protein, but the protein × protozoa interaction was significant (P < 0.05). The disappearance of nitrogen from the stomach was lower (P < 0.01) for the SBM diet than for the CA diet and was increased (P < 0.05) for both diets in the presence of protozoa, but the effect of protein × protozoa interaction was not significant (P > 0.05). The ruminal presence of protozoa decreased the flow from the stomach of individual amino acids (from P < 0.05 to P < 0.001) and of nonammonia nitrogen (P < 0.05). However, the decreases were greater (from P < 0.05 to P < 0.001) for the CA diet than for the SBM diet, but the effects of protein × protozoa interaction were not significant (P > 0.05). The ruminal presence of protozoa increased (P < 0.05) the flow from the stomach of ammonia-N for SBM diet but not for CA diet. The effects of protein and of protein × protozoa interaction were not significant (P > 0.05). It was concluded that although ruminal protozoa do not metabolize casein, their effect of decreasing amino acid flow from the stomach can be greater for diets containing casein (soluble protein) as protein supplement than for those containing soybean meal (insoluble protein). Key words: Duodenal flow, nitrogen, protozoa, casein, soybean meal, sheep

Effect of grain level and protein source on ruminal fermentation, degradability, and digestion in milking cows fed silage

Five primiparous Holstein cows (483 kg BW) of low productivity were used in a 4 x 5 incomplete Latin square design to study the effects of feeding two levels of grain containing soybean meal and one level of grain containing fish meal on feed intake, milk production, digestibility, and rumen fermentation. Animals all were fed alfalfa silage for ad libitum intake. Collection of data was between wk 11 and 24 of lactation. The four treatments were an all silage diet (control), silage and medium concentrate fed at 1.8% BW containing soybean meal, and silage and low concentrate fed at 1.3% BW containing either soybean meal or fish meal. Treatments other than control were designed to give similar CP intake from the concentrate, which was based on high moisture corn and cob meal. Milk production and composition were similar among treatments except for fat percentage, which was significantly lower for low grain soybean meal. Intake of DM was higher on medium grain soybean meal compared with the other treatments. Average BW and change in BW (.11 kg/d) were not affected by treatments. Digestibility of DM was higher for cows fed grain (68 to 73%) than for those fed the control diet (60%). Generally, feeding concentrate at 1.3 or 1.8% BW and supplementing with soybean meal or fish meal resulted in pH and concentrations of NH3 N and VFA similar to those observed on the all silage diet. Feeding concentrate at 1.3 or 1.8% BW and supplying fish meal or soybean meal did not change feed utilization enough to increase milk production in low producing cows compared with an all silage diet.

Effects of grain level and protein source on yield, feed intake, and blood traits of lactating cows fed alfalfa silage

Multiparous Holstein cows (n = 27) averaging 590 kg BW were allotted at 3 wk postpartum to nine trios blocked on the basis of similar calving date. Animals were fed alfalfa silage for ad libitum intake and remained in the experiment until wk 11 of lactation. Cows within each trio were assigned randomly to either a medium level of concentrate fed at 1.8% BW containing soybean meal or a low level of concentrate fed at 1.3% BW containing either soybean meal or fish meal. The three treatments were designed to give similar CP intake as percentage of BW from the concentrate. Intake of DM and milk yield were measured daily, and BW and milk composition were recorded weekly. Blood was sampled during wk 7 of lactation. Total DMI was higher for cows fed concentrate at 1.8% BW than for those fed at 1.3% BW. Silage DMI was similar across treatments and averaged 2.17% BW. Milk production, 32.0 kg/d, and milk composition, 3.95% fat, 2.90% protein, and 5.07% lactose, were similar for all treatments. Cows fed at 1.8% BW gained 11.0 kg, whereas those fed at 1.3% BW lost 8.4 and 7.4 kg, respectively, when given soybean meal or fish meal, but these differences were not significant. Prefeeding plasma concentrations of NEFA were higher for cows fed fish meal, which was related to their greater weight lost at wk 7 of lactation compared with those fed soybean meal. Level of concentrate and protein of low or high rumen degradability resulted in similar milk production for cows averaging 32.0 kg/d during early lactation.

Digestibility measured by fecal and ileal collection in preruminant calves fed a clotting or a nonclotting milk replacer

Eight Holstein male calves, each fitted with an ileal reentrant cannula at 7 to 10 d of age, were fed a milk replacer based on low heat skim milk powder with or without an oxalate-NaOH buffer known to prevent curd formation in the abomasum. The calves were used to study the effects of milk clotting on digesta flow at the ileum and apparent digestibility measured by fecal and ileal collection. Patterns of ileal flow of total digesta, DM, N, and fat were similar for the clotting and the nonclotting milk replacers. The apparent digestibility of DM and N was higher when measured by fecal than ileal collection for both milk replacers. Digestibility of DM was higher for the clotting than for the nonclotting milk replacer when measured by ileal collection. Clotting did not affect N digestibility measured by either fecal or ileal collection. The concentration of amino acids differed generally in the ileal digesta compared with concentration in feces. In the ileal digesta, some amino acids showed lower concentrations in the clotting milk replacer fed calves compared with those fed the nonclotting milk replacer. The coefficients of digestibility of each amino acid were similar when measured by either fecal or ileal collection. Clotting had no effect on amino acid digestibility measured by both fecal and ileal collection. The data suggest that fecal collection might indicate higher digestibility as compared with ileal collection and that the absence of milk replacer clotting does not affect ileal flow and digestibility of milk replacer N and fat.

Digestibility and blood parameters in the preruminant calf fed a clotting or a nonclotting milk replacer

Eight male Holstein calves 7 to 10 d of age were fed a milk replacer containing a skim milk powder subjected to low-temperature drying either with or without addition of an oxalate-NaOH buffer known to prevent curd formation. The calves were used in a completely randomized design to study the effect of milk clotting on digestibility and blood parameters. Plasma glucose and plasma insulin were similar (P greater than .05) for the clotting and the nonclotting milk replacers. For both treatments, concentrations of glucose and insulin reached a peak 2 h postfeeding (P less than .01). Plasma triglycerides were higher (P less than .01) postfeeding for the nonclotting than for the clotting milk replacer. Plasma essential amino acids and plasma urea were higher, whereas plasma calcium was lower, for the nonclotting milk (P less than .01). Digestibility of dry matter, protein and fat was similar (P greater than .05) between clotting and nonclotting milk. The dry matter content of feces was not affected by clotting (P greater than .05). The data are interpreted to indicate that clotting of the milk replacer modifies blood concentrations of triglycerides, essential amino acids and urea without changing the digestibility of the diet.

Duodenal flow of digesta in preruminant calves fed clotting or nonclotting milk replacer

Four Holstein male calves each were fitted with a reentrant duodenal cannula and fed a low heat milk replacer with or without an oxalate-NaOH buffer known to prevent curd formation in the abomasum. Animals were used in a crossover design to study the effect of milk clotting on duodenal flow of DM, fat, protein, lactose, and Ca. Clotting affected the flow of DM, protein N, total N, and fat as shown by the more uniform gastric emptying of the clotting milk replacer compared with the nonclotting one. For both treatments, the flow rate of these components reached a peak 2 h after feeding. Clotting did not alter the flow rate of free amino N, lactose, and Ca. The cumulative flow of DM, lactose, and Ca was similar for the clotting and nonclotting milk replacers rising gradually during the first 4 h postfeeding and tending to plateau thereafter. The clotting milk replacer resulted in a more linear cumulative flow of fat, protein N, and total N than the nonclotting one. Proteolysis of milk protein in the abomasum was the same for the two milk replacers as indicated by the total flow of free amino N measured over 24 h. Data suggest that milk clotting modifies abomasal flow of milk constituents retained in the abomasal clot but does not alter the flow of constituents in the whey fraction.

An oxalate-sodium hydroxide buffer to study the role of milk replacer coagulation in preruminant calves

An oxalate-NaOH buffer, which prevents coagulation in the abomasum of young calves, was added to a nonclotting milk replacer based on high heat skim milk powder, to investigate effects of this buffer on digestibility and metabolism of dietary components. Twelve Holstein male calves were allotted at random in two groups of six animals each and fed the experimental milk replacers from 3 to 17 d of age. Digestibility of dry matter, protein, and fat was similar for both control and buffered milk replacers. Concentrations of plasma glucose, triglycerides, alpha-amino nitrogen, and urea were the same in animals receiving buffer treated milk replacer and control diets. The data suggests that this oxalate-NaOH buffer would be suitable to prevent milk clotting in studies dealing with the importance of coagulation in digestion and metabolism in preruminant calves.