Milk production response to diets supplemented with dried brewers grains, wet brewers grains, or soybean meal

Forty four multiparous Holsteins, 114 +/- 28 days in milk (32 kg/day, 3.4% fat), were fed a basal diet of 12% crude protein and 20% acid detergent fiber for 10 days, then stratified by milk production into four groups. Cows were randomized to one of nine diets in a 3 X 3 factorial in which basal was supplemented with dried brewers grains, wet brewers grains, or soybean meal to supply in the diet 14.5, 16.0, and 17.5% crude protein. Eight cows remained on basal during the 50-day trial. Basal contained: 14% alfalfa silage, 27% ensiled ground-corn, 53% corn silage, and 6% vitamin-mineral mix. Milk production (kg/day) for cows fed dried brewers grains (29.4) and wet brewers grains (28.9) was higher than soybean meal (26.2) and basal (23.1). Milk production was different for diets with high (29.6) vs. low (27.8) and medium (27.2) protein. Dry matter intake (as percent of body weight) was 3.7, 3.5, 3.3, and 2.9 for dried brewers, wet brewers, soybean meal, and basal, respectively. Milk protein percent and milk fat percent differed for protein source. Rumen fluid ammonia nitrogen for combined 2, 4, and 6 h post-feeding, was (mg/100 ml) 10.4 for dried brewers, 14.9 for wet brewers, and 18.0 for soybean meal and increased from 13.2 to 15.4 with increased protein. Plasma urea tended to follow patterns of rumen ammonia. Dried brewers grains had lower apparent nitrogen digestibility but equal nitrogen balance, indicating more efficient metabolic use than soybean meal.     

Microbial numbers, rumen fermentation, and nitrogen utilization of steers fed wet or dried brewers' grains

Holstein steers were fed corn silage supplemented with either wet or dried brewers' grains to determine effects of heat drying commercial brewers' grains. Four rumen-fistulated steers were fed a 12.5% crude protein diet in a single reversal design experiment. Brewers' grains supplied 45% of the protein of the diet. Bacterial numbers, concentration of ciliated protozoa, and ammonia concentration in the rumen were higher, and rumen pH was lower, for steers fed wet brewers' grains. Concentrations of rumen volatile fatty acids were similar for both diets. Ruminal digestibility of dry matter decreased when wet versus dried brewers' grains were fed (56.9 versus 39.3%). The rate of dry matter passage from the rumen was faster with wet brewers' grains. In Experiment 2, 12 steers were in a 2 X 2 factorial design. Diets contained wet or dried brewers' grains supplemented at 22 or 40% of the diet dry matter (12.5 and 14.5% crude protein). Nitrogen retention was increased in steers fed the higher crude protein diet. Apparent digestible nitrogen, acid detergent fiber nitrogen, and nitrogen retention were higher with wet versus dried brewers' grains. Plasma essential and nonessential amino acids were also higher in steers fed wet brewers' grains. Alteration in microbial numbers, fermentation measurements, and nitrogen utilization were associated with more soluble nitrogen with wet (13.4%) versus dried (3.3%) brewers' grains.     

Influence of synchronizing protein and starch degradation in the rumen on nutrient utilization and microbial protein synthesis

A 4 x 4 Latin square design with four multiparous cows in midlactation fitted with duodenal cannulae was used to determine the effect of synchronization of protein and starch degradation in the rumen on nutrient availability in lactating cows. As major starch and protein sources, diets contained: barley plus cottonseed meal; barley plus brewers dried grains; milo plus cottonseed meal; and milo plus brewers dried grains. Experimental periods were 12 d and consisted of 8 d adjustment and 4 d collection. Chromium oxide was used as the marker to determine digestibility and nutrient flow from the rumen. Microbial protein synthesis was estimated from nucleic acid content in duodenal samples. Apparent and corrected rumen digestibilities of DM, organic matter, CP, and starch were higher for diets containing barley than milo but were not affected by protein source. For diets containing barley and milo, starch digested postruminally averaged 820 and 2190 g/d and percentage digestibility was 70 and 77%. No difference among diets was found in DM, organic matter, and CP flow to the small intestine; however, microbial N synthesis was higher in diets containing barley than in diets containing milo.     

Influence of nonprotein nitrogen and protein of low rumen degradability on nitrogen flow and utilization in lactating dairy cows

Four lactating cows, each fitted with a rumen cannula and duodenal and ileal t-cannulae, were used to measure flow and digestion of nitrogenous compounds in the digestive tract. Dietary dry matter contained 17% crude protein and 50:50 forage:concentrate. Treatments were: 1) corn silage-soybean meal; 2) corn silage-heated soybean meal; 3) ammonia-treated corn silage-soybean meal; and 4) ammonia-treated corn silage-heated soybean meal. Flow of organic matter to the duodenum was overestimated when lanthanum or chromium ethylene-diaminetetraacetate was used as an indigestible marker. This resulted in low estimates of ruminal digestion of organic matter and high estimates of nitrogen flow to the duodenum. However, calculations using lanthanum or lignin as markers yielded similar organic matter flow to ileum and feces. With acid-detergent lignin as a marker, estimates of dietary nitrogen degraded in the rumen were: corn silage-heated soybean meal, 55.0% ammonia-treated corn silage-heated soybean meal, 58.8%; ammonia-treated corn silage-soybean meal, 63.3%; and corn silage-soybean meal, 66.0%. Digestion in the small intestine of nonammonia nitrogen was equal for all treatments suggesting that availability of heated soybean meal in the intestine was not different, although ruminal degradability tended to be lower. Feeding diets containing nonprotein nitrogen did not decrease available nitrogen at the duodenum.     

Effects of sarsaponin on digestion and passage rates in cattle fed medium to low concentrate

Four dairy cows with duodenal cannulae were fed diets consisting of sorghum silage (67% of dietary dry matter) at 85% of ad libitum intake with 0 (control diet) or 44 ppm (dry matter) sarsaponin (sarsaponin diet) in a crossover experiment. Digestion coefficients for organic matter were low but increased by addition of sarsaponin both in the rumen (43.7 versus 32.4%) and total tract (52.1 versus 48.2%). Digestibilities of starch and nitrogen in the rumen and total tract and passage rates of fluid, concentrate, and silage tended to be greater for the sarsaponin diet. Extent of ruminal digestion of organic matter was related to passage rate of concentrate (correlation .81) and fluid (correlation .75). In a second study, diets contained 50% concentrate either with or without sarsaponin added at 44 ppm. Ruminal pH for animals given sarsaponin tended to be lower 4, 8, and 12 h after feeding. In situ rate constants of dry matter disappearance tended to be greater with the control diet for corn, alfalfa, and prairie hay and lower for milo and soybean meal. Lag time of digestion tended to be longer with the sarsaponin diet for corn, milo, soybean meal, and corn gluten meal but shorter for alfalfa and prairie hay. Although sarsaponin may increase ruminal digestion of medium to low concentrate diets, in situ data indicate that effects may differ with type of feed.     

Effect of rumen protein degradability on milk yield of dairy cows in early lactation

Twenty-four mature Holstein cows were fed diets of 40% corn silage and 60% concentrate (dry matter) beginning at parturition through wk 16 of lactation. A control concentrate (corn, soybean meal, and barley) was fed through wk 4 followed by assignment of cows to either a concentrate of low or high rumen protein degradability. In situ trials with two fistulated cows fed similar diets yielded rumen protein degradabilities of 78.5, 70.3, 69.9, 67.3, 49.1, and 36.5% for barley, corn, corn gluten feed, soybean meal, brewer's grains, and cottonseed meal. The low degradability concentrate (corn, cottonseed meal, brewer's grains, and corn gluten feed) had an estimated rumen protein degradation of 52.9% and a total ration crude protein of 14.3%. The high degradability concentrate containing corn, barley, and soybean meal was 72.8% rumen degradable, and total ration protein for this treatment was 14.5%. Dry matter intakes were 21.0 and 22.0 kg/day for the low and high degradability diets. Milk yield, fat percent, and fat-corrected milk were not affected by treatment. Milk protein percent and protein yield decreased from 3.00 to 2.84% and 1.07 to .99 kg/day in the high and low degradability diets. Efficacy of use of degradability as a criterion for feed formulation is questioned until understanding of both feed protein breakdown and microbial synthesis is greater.     

Dietary energy regulation during gestation on subsequent lactational response to soybean meal or dried brewers grains

Forty-two Holstein cows were paired by body condition and mature equivalent milk production and fed either a high or low energy diet for the last 16 to 18 wk of lactation. Cows fed the high energy diet produced more milk (21.6 versus 17.6 kg/d), gained more body condition, and were heavier after calving (641 versus 591 kg) than cows fed the low energy diet. Beginning wk 3 postpartum, half the cows in each prepartum energy group were fed supplemental dried brewers grains or soybean meal. During wk 1 to 15 of lactation, cows from the high energy group produced more 3.5% fat-corrected milk (33.8 versus 31.3 kg/d), consumed less dry matter (23.2 versus 24.4 kg/d), and lost more body weight (-2.7 versus .9 kg/wk) compared with cows from the low energy group. Milk production, feed intake, and body weight change were not affected by protein source. The high amount of bound nitrogen in dried brewers grains resulting in decreased intestinal digestibility of escape protein may have been responsible for the lack of production response to this protein source.     

Microbial Protein Synthesis in Rumens of Cows Fed Dried Whole Whey

Two rumen-fistulated Holstein cows, weighing approximately 550 kg, were in an experiment with switchback design to evaluate effects of consuming large amounts (38% of total ration dry matter) of dried whole whey on synthesis of microbial protein in the rumen. Cows were fed total mixed rations of (dry matter) 45% corn silage, 10% alfalfa hay, and 45% concentrate mix. The concentrate mix was primarily corn and soybean meal (control) or 85% dried whole whey. Dry matter intakes averaged 16.4 and 15.3 kg/day for control and whey diets. Diaminopimelic acid nitrogen as percent of bacterial nitrogen was similar for both diets (.61 and .63% for control and whey diets). Likewise, aminoethylphosphonic acid nitrogen as percent of protozoal nitrogen was similar for both diets (.17 and .19% for control and whey diets). For the control diet, total ruminal nitrogen was estimated to be 45% bacterial and 27% protozoal. Bacteria and protozoa accounted for 52 and 22% of the total ruminal nitrogen in the cows fed the whey diet. Ruminal fluid volume (33.8 and 39.2 liters for control and dried whey diets) and dilution rates (10.2 and 12.8% h) were higher for dried whey. Ruminal ammonia (5.0 and 3.4 mg/dl) was lower for dried whey. Butyrate (16.5 and 24.4 moles/100 moles total volatile fatty acids) was higher, whereas propionate was lower (32.4 and 23.2 moles/100 moles total volatile fatty acids) when cows were fed dried whey. Bacterial synthesis appeared to be increased when cows were fed a diet containing large amounts of dried whey.     

Effects of feeding triticale dried distillers grains plus solubles as a nitrogen source on productivity of lactating dairy cows

The objective of this study was to compare triticale dried distillers grains plus solubles (TDDGS) as a source of dietary N with other high-protein feeds commonly used in North America: corn dried distillers grains plus solubles (CDDGS), canola meal (CM), and soybean meal (SBM). Rumen degradable protein (% of crude protein, CP) after 16 h of incubation in the rumen was higher for CDDGS and TDDGS (69.3% and 64.5%, respectively) than for CM (62.2%) and SBM (53.0%). For the lactation study, experimental diets were formulated to supply 30% of dietary CP from TDDGS, CDDGS, CM, or SBM. These diets contained 22.3% forage neutral detergent fiber and approximately 19.2% CP and were fed to 12 multiparous Holstein cows (130 ± 40 d in milk) in a 4 × 12 Latin rectangle design with 21-d periods. Neither dry matter intake nor milk yield was affected by treatment, averaging 25.5 and 35.5 kg/d, respectively. Plasma concentrations of Arg, Lys, and Thr were greater for cows fed CM or SBM compared with those fed TDDGS or CDDGS, whereas plasma concentrations of Leu and Phe were lower for cows fed CM or SBM compared with those fed TDDGS or CDDGS. Cows fed CDDGS had lower milk CP yield compared with cows fed CM (1.07 vs. 1.16 kg/d). Contrarily, milk CP and milk lactose yields were not different for cows fed TDDGS compared with CM or SBM. These data suggest that TDDGS can replace CM or SBM in the diets of lactating dairy cows without adverse effects on production. Furthermore, although dried distillers grain has been generally accepted as a feed high in ruminal undegradable protein, CDDGS and TDDGS used in the present study had high in situ ruminal degradable crude protein. Further investigation is warranted to determine the extent of variation in ruminal protein degradation among different types of dried distillers grains.     

The energy content of wet corn distillers grains for lactating dairy cows

Forty-five energy balances were completed with 12 multiparous, lactating Holstein cows in a study designed to determine the energy content of wet corn distillers grains. Treatments were applied in a repeated switchback design and consisted of total mixed diets containing 31.4% corn silage, 18.4% alfalfa hay, and either 30.7% rolled corn and 16.7% soybean meal or 17.0% rolled corn and 31.2% wet corn distillers grains (dry matter basis). Replacement of corn and soybean meal with wet corn distillers grains reduced dry matter intake 10.9% but did not affect milk production. Neither digestible nor metabolizable energy were affected by diet composition. Heat and milk energy output did not differ by diet, but body energy retained was 2.8 Mcal/d less in cows fed the wet corn distillers grains diet. Multiple regression estimates of maintenance metabolizable energy requirement and partial efficiencies of metabolizable energy used for lactation and body energy deposition did not differ by diet. Pooled estimates were 136.2, 0.66, and 0.85, kcal of metabolizable energy/ body weight0.75 per day, respectively. Calculated by difference, wet corn distillers grains was estimated to contain 4.09, 3.36, and 2.27 Mcal/kg of dry matter as digestible, metabolizable, and lactational net energy, respectively. These energy estimates were 7 to 11% and 10 to 15%, respectively, greater than those reported for dried corn distillers grains by the 1989 and 2001 dairy NRC publications.     

Effect of sodium bicarbonate on rate of passage and degradation of soybean meal in postpartum dairy cows

Effects of sodium bicarbonate on rate of passage and disappearance of soybean meal from the rumen were determined in a change-over experiment with eight cows. Experimental diets containing 50 or 60% roughage were fed over five 21-day periods with four cows per diet. Sodium bicarbonate at 1.0 and 2.5% (diet dry matter) were changed over in periods 2 and 4, whereas periods 1, 3, and 5 served as control. Rate of passage of soybean meal was measured with chromium-mordanted soybean meal and rate of disappearance by nylon bag technique. Effects of diet were similar for all responses. Response to the two percents of buffer was similar for dry matter intake, milk yield, milk fat, and protein. Percent buffer fed was associated positively with ruminal pH and with disappearance of nitrogen from nylon bags. The 0, 1, and 2.5% of buffer resulted in turnover rates of mordanted soybean meal of 8.22, 9.80, and 10.52%/h, but degradation of protein remained relatively constant at 36.0, 38.4, and 38.2%. The influence of rate of passage on ruminal degradability is discussed.     

Influence of protein supplementation of alkaline hydrogen peroxide-treated wheat straw on ruminal microbial fermentation

A dual flow continuous culture system was used to determine the effects of four protein sources (soybean meal, Ca-ligno-sulfonate treated-soybean meal, blood meal, and feather meal), supplied individually or in combination in diets composed predominantly of alkaline hydrogen peroxide-treated wheat straw, on ruminal microbial fermentation and amino acid flow. Diets containing blood meal had lower organic matter and fiber digestion, NH3 N and VFA concentrations, and CP degradation but higher non-NH3 N, dietary N, total amino acid, and essential amino acid flows. Feather meal fed alone or combined with other sources was not different from the blood meal diet in organic matter and fiber digestion. Combining treated soybean meal and blood meal resulted in similar organic matter and fiber digestibilities compared with the soybean meal diets. This combination was similar to the treated soybean meal diet in VFA concentration, non-NH3 N, and essential and total amino acid flows; however, amino acid profile was different with this combination, showing higher histidine and leucine flows. Results from this study suggest that amino acid profiles of digesta leaving the rumen may be manipulated by choice of protein supplement when diets containing a low protein, highly fermentable feedstuff such as alkaline hydrogen, peroxide-treated wheat straw are fed.     

Ruminal degradability of dry matter,crude protein,and amino acids in soybean meal,canola meal,corn, and wheat dried distillers grains

Different protein sources, such as canola meal (CM) or dried distillers grains (DDG), are currently used in dairy rations to replace soybean meal (SBM). However, little data exists comparing their rumen degradation in a single study. Therefore, the objective of this study was to compare the ruminal degradation of dry matter (DM), crude protein (CP), and AA of SBM, CM, high-protein corn DDG (HPDDG), and wheat DDG plus solubles (WDDGS). In situ studies were conducted with 4 rumen-fistulated lactating Holstein cows fed a diet containing 38% grass hay and 62% corn-based concentrate. Each protein source was incubated in the rumen of each cow in nylon bags for 0, 2, 4, 8, 16, 24, and 48 h to determine DM and CP rumen degradation kinetics, whereas additional bags were also incubated for 16 h to evaluate AA ruminal disappearance. Rumen DM and CP degradability was calculated from rumen-undegraded residues corrected or not for small particle loss. Data were fitted to an exponential model to estimate degradation parameters and effective degradability (ED) was calculated with a passage rate of 0.074 h⁻¹. The WDDGS and SBM had higher uncorrected ED (DM = 75.0 and 72.6%; CP = 84.8 and 66.0%, respectively) than CM and HPDDG (DM = 57.2 and 55.5%; CP = 59.3 and 48.2%, respectively), due to higher soluble fraction in WDDGS and a combination of higher potentially degradable fraction and rate of degradation in SBM. Correction for small particle loss from bags, higher for WDDGS than for the other protein sources, decreased estimated ED but did not alter feed ranking. The ruminal disappearance of AA after 16 h of incubation reflected the overall pattern of CP degradation between protein supplements, but the ruminal disappearance of individual AA differed between protein supplements. Overall, these results indicate that, in the current study, (1) SBM and WDDGS were more degradable in the rumen than CM and HPDDG, and (2) that small particle loss correction is relevant but does not alter this ranking.     

Effect of rumen ammonia concentration on in situ rate and extent of digestion of feedstuffs

Three dry Holstein cows fitted with rumen fistula were fed a 7.4% crude protein diet consisting of 47.4% corn, 50% cottonseed hulls, and 2.6% minerals and vitamins during a 44-d experiment. Treatments consisted of rumen infusion, 0, 33, 67, and 100 g/d of urea nitrogen applied in a four period Youden Square design. Increasing urea infusion increased rumen fluid ammonia nitrogen from 4.3 to 25.0 mg/dl. Estimated effective dry matter degradation based on in situ rates of digestion were increased from 67.9 to 74.4% for corn and 77.5 to 80.3% for soybean meal with maximums at 100 g/d infused urea nitrogen. Up to 67 g/d infused nitrogen increased dry matter degradation of corn gluten feed from 67.0 to 71.4% and cottonseed meal dry matter degradation from 56.7 to 60.1%. Alfalfa hay dry matter and neutral detergent fiber degradation were not increased by urea infusion. Minimum rumen ammonia required in feeds in this trial were pooled with literature data and suggest that lowest ammonia concentrations required for maximal digestion was a function of the rumen fermentability of the diet or feed. The equation: minimum ammonia concentration (mg/dl) = .452 fermentability % - 15.71, accounted for 50% of the variation in minimum ammonia requirements. We conclude that rumen ammonia concentrations required for maximum digestion are not constant but rather are a function of fermentability of the diet.     

Site and extent of nutrient digestion in lactating dairy cows fed alfalfa protein concentrate or soybean meal

In vivo and in situ trials were conducted to investigate the utilization of alfalfa protein concentrate as a protein supplement for lactating dairy cows. In the in vivo trial, four Holstein cows fitted with ruminal, duodenal, and ileal cannulae were used in a crossover experiment to measure site and extent of nutrient digestion. Isonitrogenous and isoenergetic diets containing alfalfa protein concentrate or soybean meal were fed four times daily. Sixty percent of dietary total N was provided by the test proteins. Ruminal ammonia and total VFA concentrations were lower in cows fed alfalfa protein concentrate. Fractional digestion coefficient of organic matter (52 vs. 43%) and degradation of dietary protein (57 vs. 47%) in the rumen were slightly lower in cows fed alfalfa protein concentrate. The ratio of amino acid flow to the small intestine to dietary intake of amino acid was higher in cows fed alfalfa protein concentrate. In the in situ trial, rate of N disappearance (2.4 vs. 9.5%.h-1) and potential protein degradability (35 vs. 68%) were lower for alfalfa protein concentrate. Results suggest that alfalfa protein concentrate may be more resistant to ruminal degradation than soybean meal and could be utilized as a relatively undegradable protein source for milk production.     

Influence of varying protein and starch degradabilities on performance of lactating cows

A milk production and digestibility trial with 32 cows (2 X 2 factorial with 8 cows per treatment) was conducted to test animal response to varying rumen degradation of dietary starch and protein. Four rations (barley-cottonseed, barley-brewers dried grains, milo-cottonseed, and milobrewers dried grains) were compared in early lactation cows fed 65% concentrate and 35% forage for 60 d. Digestibilities of starch were higher for barley than milo diets; whereas, those for organic matter were higher for cottonseed meal than brewers dried grains. Milk production was highest on barley-cottonseed with mean adjusted values of (kg/d): 37.4, 34.9, 34.2, and 34.6 for respective treatments. Dry matter intakes were not different among rations. Milk fat was higher on milo than barley with respective diets averaging (%): 3.1, 2.9, 3.4, and 3.6, and resulting in lowest FCM for the barley-brewers dried grains diet. Milk protein was not altered by treatment. These data suggest that responses to varying protein degradability can be altered by rate of starch breakdown in the rumen.     

Influence of dietary protein degradability and energy concentration on growth of heifers and steers and intraruminal protein metabolism

Two studies with 4-mo old Holstein steers and heifers and one abomasal digesta collection study were used to determine the influence of altering the dietary energy content and crude protein escape on growth, intraruminal protein metabolism, and site of digestion of dry matter, starch, cellulose, hemicellulose, and protein. Dietary energy concentration was increased by tallow, and rumen protein escape was increased by dehydrated alfalfa and distillers dried grains with solubles substituted for soybean meal. Tallow appeared to depress intake and gain, but gain was increased by protein escape from the rumen. Total and particulate digesta crude protein reaching the abomasum was increased by protein escape; however, percentage crude protein digested was decreased in these treatments due to increased acid detergent insoluble nitrogen. Decreasing crude protein solubility decreased ruminoreticular digestion of dry matter, cellulose, hemicellulose, and starch; however, lower intestinal starch digestion compensated for decreased ruminoreticular digestion. In a third study, with growing steers and heifers, corn gluten meal provided the escape protein and soybean meal the degradable protein. Total and average daily gain were greater for the corn gluten meal diet, but intake was not influenced by energy concentration or protein escape.     

Response of lactating dairy cows to high protein distillers grains or 3 other protein supplements

This study compared high protein dried distillers grains (HPDDG) with soybean meal (SBM), canola meal (CM), and dried distillers grains with solubles (DDGS) as protein supplements in dairy diets. A lactation trial used 12 multiparous cows averaging 78 d in milk at the start of the experiment in a 4 × 4 Latin square design with 28-d periods. Weeks 1 and 2 of each period were used for adjustment and wk 3 and 4 for data collection. Each treatment diet consisted of 55% forage and one of the 4 protein supplements in a concentrate mix. Total mixed diets averaged 15.3% crude protein, with 38% of the protein from one of the 4 protein supplements. Dry matter intake (24.4 kg/d) and crude protein intake (3.57 kg/d) were similar for all 4 diets. Milk production (31.8 kg/d), protein yield (1.05 kg/d), fat yield (1.29 kg/d), and protein percentage (3.31) were similar for all 4 treatment diets. Milk fat percentage was lower when fed DDGS (3.78) than when fed SBM or HPDDG (4.21), but similar with CM (4.07). Feed efficiency (1.44 kg of energy-corrected milk/kg of dry matter intake) and nitrogen efficiency (0.29) were not affected by diet. Total milk nitrogen and true milk protein were highest when fed the HPDDG diet. Molar proportions of acetate, propionate, and the acetate to propionate ratio in ruminal contents and ruminal ammonia concentrations were similar for all diets. Arterial and venous concentrations of total essential AA tended to be lower when fed CM, reflecting lower concentrations of His, Ile, Leu, and Val when fed the CM diet. Extraction efficiency of AA from blood by the mammary gland indicated that Met was the first limiting AA when fed the SBM diet, whereas Lys was first limiting for the other diets. Phenylalanine was third limiting with all diets. Feeding HPDDG was equally as effective as feeding SBM, CM, and regular distillers grains as a protein supplement for lactating cows.     

Forestomach and whole tract digestibility for lactating dairy cows as influenced by feeding frequency

Three lactating Holstein cows, averaging 510 kg and fitted with T-type duodenal cannulae in the proximal duodenum, were in a 3 X 3 Latin-square experiment to measure digestion in forestomachs and whole tract of feed nitrogen and neutral detergent fiber components as influenced by frequency of feeding. Cows were fed one diet containing 65% chopped grass legume hay, 26% cracked corn, and 8% soybean meal. Mixed ration was fed either once daily, four times daily, or the concentrate portion of the diet was fed once daily and the forage portion four times. Ytterbium, as ytterbium chloride, was included with diets to allow calculation of flow rates of duodenal and fecal dry matter. Assayed ratios of nitrogen to diaminopimelic acid in ruminal bacteria and duodenal digesta or fecal bacteria and feces were used to calculate duodenal and fecal bacterial nitrogen flows respectively. Ratios of nitrogen to diaminopimelic acid in ruminal and fecal bacteria averaged 4.15 and 2.38 g/mmol. Apparent digestibility of organic matter in the forestomachs and whole tract averaged 43.7 and 66.4%. Forestomach and whole tract digestibility of cellulose, hemicellulose, and lignin averaged 56.1, 52.0, 14.7, and 58.7, 58.5, and 16.8. Bacterial nitrogen flows averaged 255 and 91 g/day at the duodenum and in the feces. Bacterial nitrogen yield in the rumen averaged 36.6 g/kg organic matter apparently digested in the forestomachs. Frequency of feeding had no effect on almost all measures and components of rumen and whole tract metabolism and digestion. For these intakes, frequency of feeding had little effect on feed intake and nutrient utilization.     

Ruminal degradability and intestinal digestibility of protein and amino acids in soybean and corn distillers grains products

New fractionation and fermentation technologies in the ethanol industry have resulted in the production of different forms of distillers grains (DG). Such products are reduced-fat, high-protein, and “modified” wet feeds. Characterization of protein fractions of these co-products and other commonly used feedstuffs is important for the formulation of dairy cattle diets. In situ and in vitro techniques were conducted to compare crude protein (CP) availability in 4 DG products with commonly used soybean proteins. Soybean protein products included solvent-extracted soybean meal (SBM; 44% CP), expeller soybean meal (ESBM), and extruded soybeans (ES). The DG products were conventional distillers dried grains with solubles, reduced-fat distillers dried grains with solubles (RFDGS), high-protein distillers dried grains, and modified wet distillers grains with solubles (MWDGS). Nylon bags containing 5 g of each feed were incubated in the rumen of 3 cannulated lactating cows for 2, 4, 8, 16, 24, and 48 h. The rapidly degradable CP fraction varied from 8.1 to 37.2% for SBM and MWDGS, respectively. The slowly degradable CP fraction was greatest for SBM, ES, and high-protein distillers dried grains (88.0% ± 3.7), followed by ESBM, distillers dried grains with solubles, and RFDGS (76.8 ± 4.1%). The MWDGS had the lowest slowly degradable CP fraction (61.1%). The rate of degradation of the slowly degradable CP fraction ranged from 11.8 for SBM to 2.7%/h for RFDGS. Rumen-undegradable protein varied widely (32.3 to 60.4%), with RFDGS having the greatest and SBM the lowest concentrations. Intestinal digestibility of rumen-undegradable protein (IDP) was estimated by pepsin-pancreatin digestion of ruminally preincubated (16 h) samples. The IDP was greatest for SBM, ESBM, and ES (97.7% ± 0.75), whereas IDP of DG products was 92.4% ± 0.87. Similarly, total digestible protein was greatest (99.0%) for soybean products, whereas DG products had a total digestible protein of 96.0%. Intestinal digestibility of most AA in DG products exceeded 92% and was slightly lower than for soybean products, except for Lys, where the digestibility was 84.6% for DG compared with 97.3% for soybean products. Absorbable Lys was lower for DG (7.0 g/kg of CP) compared with ESBM and ES (average of 23.8 g/kg of CP). Dried DG, ESBM, and ES provided more absorbable AA compared with SBM and MWDGS. These results suggest that the AA availability from DG products is comparable with that from soybean products.