Intestinal supply of amino acids in sheep fed alkaline hydrogen peroxide-treated wheat straw-based diets supplemented with soybean meal or combinations of corn gluten meal and blood meal

Ruminal Microbial Degradation of Individual Amino Acids from Heat-Treated Soyabean Meal and Corn Gluten Meal in Continuous Culture

Eight dual-flow continuous culture fermenters were used in three periods to study the effects of diets containing heat-treated soyabean meal (HSBM) or corn gluten meal (CGM) on ruminal microbial fermentation and the degradation of individual amino acids (AA). Treatments were a mix of non-protein nitrogen (N; urea and tryptone) that were progressively substituted (0, 33, 67 and 100%) for HSBM or CGM. Ruminal escape of AA was calculated with the slope ratio technique. Total volatile fatty acids (95.0 mM) and molar proportions (mol/100 mol) of acetate (59.3), propionate (21.8) and butyrate (10.5) were not affected by the treatments. As the level of HSBM or CGM increased, the concentration of ammonia-N and the degradation of protein decreased (p < 0.01), and the flows of nonammonia and dietary N increased (p < 0.01) quadratically. Compared with HSBM, CGM provided the highest flow (g/d) of total (20.6 vs. 18.3, p < 0.01), essential (9.04 vs. 8.25, p < 0.04) and nonessential (11.5 vs. 10.0, p < 0.01) AA, and increased linearly (p < 0.01) as the level of supplemental protein increased. Ruminal degradation of essential AA was higher (p < 0.04) than nonessential AA in CGM, but not in HSBM. Degradation of lysine was higher (p < 0.01) in both proteins, and degradation of methionine was higher in CGM. Ruminal degradation of individual AAs differ within and between protein sources and needs to be considered in precision feeding models.

Estimating degradation of individual essential amino acids in fish meal and blood meal by rumen microbes in a dual-flow continuous-culture system

Current feeding systems are based on the assumption that the AA profile of rumen undegraded protein is similar to that of the original feed. The objective of this experiment was to determine rumen bacterial degradation of individual essential AA in fish meal (FM) and blood meal (BM). Eight dual-flow continuous-culture fermentors were used in a completely randomized block design with a factorial arrangement of treatments and 3 replicated periods. Fermentors were supplied with 95 g of dry matter/d of isonitrogenous diets. Treatments contained a nonprotein N source (urea and tryptone) that was substituted with increasing proportions of FM or BM (0, 33, 67, or 100%). Diets consisted of 22.0% crude protein, 35.2% neutral detergent fiber, 34.6% nonfiber carbohydrates, 2.0% ether extract, and 9.2% ash. We hypothesized that the increase in the flow of individual AA would be attributed to the increase in the supply of the AA from each protein supplement. True organic matter degradation was decreased by increasing levels of FM or BM, but did not affect degradation of neutral detergent fiber and acid detergent fiber, total volatile fatty acids (VFA) concentration, or the molar proportion of propionate. There was a substrate by level of inclusion interaction in acetate molar proportion and branched-chain VFA. Butyrate concentration decreased linearly with increasing levels of FM and BM in treatment. Changes in branched-chain VFA reflected differences in content of branched-chain AA between supplements and the level of inclusion, although the quadratic effect suggests that other factors were involved. Ammonia-N concentration showed a substrate by level of inclusion interaction. Total dietary N and AA flows increased with increasing levels of FM or BM in treatment. The efficiency of bacterial crude protein synthesis was not affected by treatment, but the flow of bacterial N decreased in FM diets as the level of FM increased. Flows of AA increased linearly with increasing levels of the respective AA from supplements. Arginine, Ile, Met and Phe were more degradable, while His was more resistant to bacterial degradation. Results suggest that the resistance to rumen bacterial degradation of individual AA varies within FM and BM protein and may affect the estimates of dietary supply of individual AA to the small intestine.

Effects of soybean small peptides on rumen fermentation and on intestinal and total tract digestion of luxi yellow cattle

Four Luxi beef cattle (400±10 kg) fitted with ruminal, duodenal and ileal cannulas were used in a 4×4 Latin square to assess the effects of soybean small peptide (SSP) infusion on rumen fermentation, diet digestion and flow of nutrient in the gastrointestinal tract. The ruminal infusion of SSP was 0 (control), 100, 200 and 300 g/d. Ruminal SSP infusion linearly (p<0.01) and quadratically (p<0.01) increased microbial protein synthesis and rumen ammonia-N concentration. Concentrations of total volatile fatty acid were linearly increased (p = 0.029) by infusion SSP. Rumen samples were obtained for analysis of microbial ecology by real-time PCR. Populations of rumen Butyrivibrio fibrisolvens, Streptococcus bovis, Ciliate protozoa, Ruminococcus flavefaciens, and Prevotella ruminicola were expressed as a proportion of total Rumen bacterial 16S ribosomal deoxyribonucleic acid (rDNA). Butyrivibrio fibrisolvens populations which related to total bacterial 16S rDNA were increased (p<0.05), while Streptococcus bovis populations were linearly (p = 0.049) and quadratically (p = 0.020) decreased by infusion of SSP. Apparent rumen digestibility of DM and NDF were (Q, p<0.05; L, p<0.05) increased with infusion SSP. Total tract digestion of DM, OM and NDF were linearly (p<0.01) and quadratically (p<0.01) increased by infusing SSP. The flow of total amino acids (AA), essential amino acids (EAA) and individual amino acids were linearly (p<0.01) and quadratically (p<0.01) increased with infusion SSP. The digestibility of Lysine was quadratically (p = 0.033) increased and apparent degradability of Arginine was linearly (p = 0.032) and quadratically (p = 0.042) increased with infusion SSP. The results indicated that infusion SSP could improve nutrient digestion, ruminal fermentation and AA availability.

Effects of dietary protein sources on mohair growth and body weight of yearling Angora doelings

Fifty-one yearling Angora doelings (20+/-0.6kg initial body weight (BW)) were used to determine effects of different dietary protein sources on BW change and mohair growth. Diets consisted of approximately 40% roughage and 18-19% CP (DM basis), of which two-thirds was supplied by corn gluten meal (CG), cottonseed meal (CT), hydrolyzed feather meal (FT) or menhaden fish meal (FI); DM intake was restricted at approximately 0.7kg/day. During the 94-day experiment, fleece-free ADG was greatest (P<0.05) for FI (35, 33, 35 and 50g), whereas greasy fleece weight was greatest (P<0.05) for CG (4.4, 3.6, 3.4 and 3.4kg for CG, CT, FT and FI, respectively). Likewise, mohair growth rate was greatest among treatments (P<0.05) for CG in each of the three 31- or 32-day periods. Ruminal fluid ammonia N concentration was 8, 11, 6 and 13mg/dl (S.E. 1) immediately before feeding; 10, 18, 11 and 23mg/dl (S.E. 2) at 2h after feeding; 8, 15, 10 and 18mg/dl (S.E. 2) at 4h after feeding; and 4, 6, 5 and 8mg/dl (S.E. 1) at 6h after feeding for CG, CT, FT and FI, respectively. Total VFA concentration in ruminal fluid was similar among treatments (P>0.05) at 4 and 6h, but was generally lower for CG and FT than for CT and FI immediately before feeding (29, 33, 26 and 37mM; S.E. 2) and at 2h after feeding (44, 57, 45 and 51mM for CG, CT, FT and FI, respectively; S.E. 3). In conclusion, the different protein supplements had dissimilar effects on ADG (greatest for FI) and mohair growth (greatest for CG). Factors responsible for these results are unclear, and the range of experimental or production conditions under which comparable findings might occur are unknown and deserve further study.

Preference for flavoured foods by lambs conditioned with intraruminal administration of nitrogen

We suggested that food preference depends on the interplay between flavour and post-ingestive effects, and we predicted that protein-restricted lambs would acquire preferences for foods paired with supplemental sources of N, including urea (Expts 1 and 2), casein (Expt 3), and gluten (Expt 4). In each experiment, twenty lambs, in two groups of ten, were conditioned as follows: on odd-numbered days, lambs in group 1 received wheat straw (Expts 1, 3, and 4) or ground barley (Expt 2) flavoured with a distinctive flavour, and lambs in group 2 received the same food but with a different flavour. On even-numbered days, flavours were switched and lambs received capsules containing different amounts of urea (ranging from 0.12 to 0.92 g N/d), casein (ranging from 0.23 to 0.69 g N/d), or gluten (ranging from 0.23 to 0.69 g N/d). After conditioning period of 8 d, lambs were given a two-choice test to determine preference for flavours paired with N. In Expts 1 and 2, lambs preferred the flavours conditioned with urea at lower doses (0.12 g N/d in Expt 1, 0.23 and 0.46 g N/d in Expt 2), but they avoided the flavour associated with urea at the highest dose (0.23 g N/d in Expt 1 and 0.92 g N/d in Expt 2). In Expts 3 and 4, lambs avoided the flavours associated with the lowest doses of casein or gluten (0.23 g N/d), but they preferred the flavours paired with casein or gluten at higher doses (0.46 and 0.69 g N/d). After conditioning, N administrations were suspended and lambs in Expts 3 and 4 were offered a choice of the two flavours at weekly intervals for 2 weeks (extinction); preferences persisted during extinction. Collectively, these results suggest that the post-ingestive effects of N in different forms and concentrations influenced the development of food preferences by lambs.

Addition of ruminally degradable crude protein and branched-chain volatile fatty acids to diets containing hydrolyzed feather meal and blood meal for lactating cows

This study investigated the effects of amounts of RDP and branched-chain VFA on milk production and DMI by 32 early lactation Holstein cows fed diets based on corn silage and corn. All supplemental dietary protein was supplied by animal protein by-products and urea. Hydrolyzed feather meal and ring-dried blood meal served as sources of supplemental protein and were fed in a 3:1 ratio on a N basis. The experimental design was a completely randomized design with a 2 x 2 factorial arrangement of treatments. Main factors were percentage of RDP (8.0 vs. 9.5% of dietary DM) and amount of branched-chain VFA in the diet (0 vs. 90 g/d per cow). Urea was used to adjust the amount of degradable CP. Individual DMI, milk production, and milk composition were monitored during wk 5 to 19 of lactation. Ruminal fluid and blood were collected to examine the treatment effects on ruminal VFA patterns and plasma urea N concentrations. The DMI, total milk production, and milk component yield were unaffected by treatments. The molar percentages of isobutryate, isovalerate, and n-valerate increased when branched-chain VFA were fed, and concentrations of urea N in plasma increased with higher percentages of RDP. A combination of feather meal and blood meal can be used as supplemental protein to support high milk production (> 37 kg/d) in early lactation. No production benefits were observed by increased dietary RDP or branched-chain VFA.

Microbial protein synthesis and flows of nitrogen fractions to the duodenum of dairy cows

Attempts have been made to increase nutrient availability for milk production by increasing feed intake, optimizing ruminal fermentation, and supplementing nutrients to the diet that will escape ruminal degradation. Energy and N are the nutritional factors that most often limit microbial growth and milk production. Ruminal fermentation and flow of microbial and dietary protein to the small intestine are affected by feed intake and by the amount and source of energy and protein in the diet. Feeding protein and carbohydrate that are not degraded in the rumen increases the quantity of dietary protein that passes to the small intestine but may decrease the quantity of microbial protein that is synthesized in the rumen. This often results in only small differences in the total NAN that passes to the small intestine. Because microbial protein supplies a large quantity of total AA that passes to the small intestine, differences in passage of individual AA often are only slight. Additional research with cows consuming large amounts of feed are needed to identify combinations of feed ingredients that synchronize availabilities of energy and N for optimizing ruminal digestion, microbial protein synthesis, nutrient flow to the small intestine, and milk production and composition.