Inaugural ASAS–CAAV Asia Pacif ic Rim Conference Abstracts

90 Response of cows to a low-protein diet supplemented withruminally protected methionine, lysine, threonine, and phenylalanine. Z.Yang* 1,2 , C. Wang 1 , Y. Wang 1 , B. Chen 1 , J. Liu 1 , Y. Wu 1 , and Z. Li 2 , 1 Institute ofDairy Science, Hangzhou, Zhejiang, China, 2 Hangzhou King Techina Feed Co.Ltd., Hangzhou, Zhejiang, China.The objective of the study was to investigate the optimal ratio of Thr to Phein MP on milk performance and nitrogen utilization of Holstein dairy cows.Forty multiparous cows in peak lactation were randomly assigned to a positivecontrol treatment (15% CP) and 4 dietary treatments (14% CP) with adequateMet and Lys (Lys:Met = 3:1). The 4 treatment diets had different ratios of Thr toPhe. On the basis of the control, 65 g/d of ruminally protected Thr was added todiets T and TP, and 52 g/d of ruminally protected Phe was added to diets P andTP. The 4 treatment diets were designed to have a Thr:Phe ratio in MP of 1.04:1,1.2:1, 0.9:1, and 1.05:1 respectively. Total duration of the experiment was 7 wk,following 10 d for adaptation. The addition of ruminally protected essential AAand reduction of the protein level by 1% did not affect the DMI. Cows on dietTP produced more milk and 4% fat-corrected milk than those on the controldiet. Protein percentage and milk protein were significantly higher for diet TPcompared with the other groups (P < 0.05). There were no significant differencein milk fat, milk lactose, and total solids content. Amino acid supplementationalso did not affect plasma concentrations of NEFA, albumin, or glucose (P> 0.05). With the ratio of Thr to Phe at 1.05:1, the concentrations of plasmaessential AA and total AA uptake of mammary gland were higher than thoseof the other groups. Concentrations of urea nitrogen in serum, milk, and urinewere lower for diet TP compared with the other groups (P < 0.05), indicatingthat the efficiency of nitrogen utilization was improved (P < 0.01). These resultsindicated that the optimal ratio of Thr to Phe in MP was approximately 1.05:1,at which the productivity of dairy cattle could be improved while the amount ofnitrogen excreted to the environment could be decreased greatly.Key Words: dairy cow, threonine, phenylalanineRuminant Nutrition92 Protein amide I-to-amide II ratio and α-helix-to-β-sheetratio of new coproducts of bioethanol production in relation to rumendegradability and intestinal availability in dairy cattle. P. Yu*, W. G. NuezOrtín, and D. Damiran, Department of Animal and Poultry Science, Collegeof Agriculture and Bioresources, University of Saskatchewan, Saskatoon,Saskatchewan, Canada.This study aimed to reveal protein molecular structures of the coproducts ofbioethanol production [wheat, corn, wheat distillers dried grains with solubles(DDGS), corn DDGS, and blend DDGS (wheat:corn = 70:30)] using diffusereflectance Fourier transform infrared spectroscopy as a novel approach, andto quantify the protein structure amide I-to-amide II ratio and α-helix-toβ-sheetratio in relation to protein digestive kinetics and nutritive value inthe rumen and intestine of dairy cattle. The results showed that bioethanolprocessing also changed the chemical profiles and protein subfraction profile.In situ results showed a great increase in rumen undegradable protein (RUP).Intestinal digestibility by 3-step in vitro experiments showed changes to RUP.Modeling results showed that the bioethanol processing greatly increased totalintestinally absorbable protein (feed DVE value) and degraded protein balance(feed OEB value). Both the protein structure α-helix-to-β-sheet ratio and theamide I-to-amide II ratio had a significantly negative correlation with the totalintestinally absorbed protein supply (feed DVE value) to dairy cattle and nosignificant correlation with the degraded protein balance (feed OEB value).Multiregression results showed that the protein structure α-helix-to-β-sheetratio was the most important parameter (among the amide I, amide II, amideI-to-II ratio, α-helix, β-sheet, and α-helix-to-β-sheet ratio) and could be used topredict RUP (R 2 = 0.93) and the total intestinally absorbed protein supply (R 2= 0.89) from the coproducts of bioethanol production. In summary, bioethanolprocessing changed the protein molecular structure α-helix-to-β-sheet ratio andprotein amide I-to-amide II ratio, which are strongly related to nutrient values.The protein structure α-helix-to-β-sheet ratio in the coproducts of bioethanolproductions can be used as a predictor of total intestinally absorbed proteinsupply to dairy cattle with 89% accuracy.91 Effects of different dietary rumen-degradable protein andrumen-undegradable protein levels in isonitrogenous diets on nitrogenutilization, ruminal fermentation, and milk production. T. Sun, Z. Cao, andS. Li*, State Key Laboratory of Animal Nutrition, College of Animal Scienceand Technology, China, Beijing, China.Four ruminally cannulated multiparous cows were used in a 4 × 4 Latin squaredesign to determine the effects of different dietary rumen-degradable protein(RDP) and rumen-undegradable protein (RUP) levels in isonitrogenous dietson N utilization, ruminal fermentation, and milk production. Each experimentalperiod lasted 28 d, with the first 7 d for adjustment to the experimental diets.The diets contained (DM basis) 20% alfalfa hay, 20% corn silage, 10%Chinese wildrye hay, and 50% concentrate, mainly from corn, wheat bran,cottonseed meal, rapeseed meal, and soybean meal. Four experimental dietswere formulated to contain similar concentrations of CP, NE l, ADF, and NDF,but with different RDP and RUP levels: A) 9.8% RDP and 4.8% RUP; B) 9.1%RDP and 5.4% RUP; C) 8.5% RDP and 6.0% RUP; and D) 7.9% RDP and6.5% RUP. Results showed that DMI, milk yield, and milk composition weresimilar among the treatments. There was no significant change in ruminal pHamong all diets. However, ruminal NH 3-N concentration increased significantlywith an increase in RDP. There were no significant differences in molarproportions of VFA in the rumen. Apparent digestibility of DM, NDF, and ADFwas similar for all treatments, but tended to decrease with the increase in RUPfor CP digestibility. Blood urea-N and milk urea-N concentrations increasedsignificantly by feeding 9.8% RDP (diet A) compared with the other diets, andestimated bacterial CP synthesis increased significantly with an increase inRDP, but there was little difference between diet A and diet B. Urine volume,urinary N excretion, ratio of urinary N to N intake, and urea N excretionincreased significantly by feeding 9.8% RDP (diet A) compared with feedingthe other diets. Fecal N excretion and the ratio of fecal N to N intake were notsignificantly different across treatments.Key Words: protein structure, bioethanol processing, nutrient availability93 Metabolizable protein of some feedstuffs used in ruminantdiets. H. Paya* and A. Taghizadeh, University of Tabriz, Tabriz, EastAzarBayjen, Iran.Metabolizable protein of test feeds was determined using in situ CP degradabilitycharacteristics and the chemical composition of feeds (CP and ADIN). Thefeeds were corn grain, soybean meal, wheat bran, and alfalfa. For the in situtechnique, duplicate Dacron bags were incubated for 0, 2, 4, 6, 8, 12, 16, 24, 36,48, 72, and 96 h in 2 wethers (38 ± 1.5 kg of BW) fitted with rumen cannulas.The wethers were fed a diet containing (DM basis) 550 g/kg of alfalfa hay,400 g/kg of barley grain, 48 g/kg of wheat bran, and 2 g/kg of limestone atmaintenance. The equation y = a + b(1 – e –ct ) was used to describe the in situ CPrapidly degradable fraction (a), potentially degradable fraction (b), and rate ofdegradation of fraction b (c). The QDP, SDP, ERDP, RDP, UDP, DUP, and MPcontent of feeds was calculated. A large range of CP degradation parameterswas obtained: the a, b, and c values ranged from 5.7 to 33.3% (for soybean mealand wheat bran), 43.9 to 54.5% (for alfalfa and corn grain), and 3.8 to 9.8%h –1 (for alfalfa and soybean meal), respectively. Metabolizable protein valuesfor corn grain, soybean meal, wheat bran, and alfalfa were 86.6, 381.1, 115.5,and 130.8 g/kg, respectively. A difference between amounts of feed MP couldhave resulted because of differences in nutrient composition, such as CP, ADIN,soluble protein, and degradable protein.Key Words: metabolizable protein, feedstuffKey Words: rumen-degradable protein, rumen-undegradable protein, nitrogenutilization28