Study On Rumen Dynamic Degradability And Small Intestinal Digestibility Of Common Feedstuffs In Dairy Cows

Four China Hositan cows with similar age, weight and parity and with permanent rumen fistula were chosen for this study (body weight approximately550kg, daily milk production about20kg).Rumen dynamic degradability of common feedstuffs was estimated by nylon bag technique,and the small intestinal digestibility of rumen undegraded protein (RUP) was estimated by three-step in vitro procedure (TSP) and modified three-step in vitro procedure (MTSP). The nylon bag method was used to study the rumen degradation of amino acid(AA)in feed and MTSP was used to determine the small intestine digestibility of rumen undegraded AA(RUP-AA)in feed.The preliminary results is as following with this experimental conditions:(1) For concentrated feeds, soybean meal had the highest the effective degradation rates of DM,CP,NDF and ADF, and were53.72%,54.46%,45.19%and59.34%respectively. The effective degradation rates of CP in corn and sunflower meal were higher, about50%, and the effective degradation rate of CP of DDGS was the lowest(33.38%). The effective degradation rates of DM in com and DDGS were higher, about50%,and sunflower meal was slightly lower,was41.48%.The effect degradation rates of NDF and ADF in soybean meal were higher,about50%,and sunflower meal and DDGS Were lower, NDF was about40%, about20%for ADF.(2) The effect degradation rate of DM, CP, NDF and ADF in rumen showed decreasing trend with the prolonged cutting time of alfalfa in different cutting time. Among all roughages,the effective degradation rate of DM for leymus chinensis,corn silage and corn stalk were lower than alfalfa at different degree; the effective degradation rate of DM and ADF for alfalfa of bearing pod stage was lower,and were24%and18%respectively; and the effective degradation rates of other roughages for NDF was33%～42%,26%～35%for ADF; the effective degradation rate of alfalfa for CP (about70%) was higher than whole corn silage (about60%),leymus chinensis (about52%),corn straw silage (about45.85%) and corn straw(25.71%).(3) There was a significant positive correlation between effective degradation rate in rumen in dairy cows and the degradation rate at24h for the concentrated feed(DM:R2=0.9117,p=0.0452; CP:R2=0.9548,p=0.0228; NDF:R2=0.8145,p=0.2835; ADF: R2=0.9991,p=0.0195). There was a significant and strong and correlation between effective degradation rate and the degradation rate at36h in dairy cows for the roughages (DM:R2=0.927,p<0.0001; CP:R2=0.9834,p<0.0001:NDF:R2=0.9255,p<0.0001; ADF:R2=0.8971,p<0.0001).(4) Small instestinal digestibility of RUP in concentrated feed was about more than65%,and higher than in roughages. Bud stage of alfalfa had the highest small intestinal digestibility of RUP among roughages, about55%,and corn stalk silage had the lowest small intestinal digestibility of RUP, about40.5%. Small instestinal digestibility of RUP determined by MTSP was slightly higher than by TSP, and there was a significant strong correlation between them (R2=0.967, p<0.01)(5) The ruminal degradation rates of TAA, EAA and BCAA of alfalfa after cultured for16h in the rumen were higher generally than other feeds, and alfalfa in squaring period had the highest degradation rates, were all above80%, and the DDGS and corn were under30%. The ruminal degradation rate of Lys and Met in alfalfa was more than60%, and higher generally than in other feeds, those in the corn straw silage and corn straw were the lowest, under40%. The ruminal degradation rate of Lys was higher than Met.(6) Small intestinal digestibility of RUP-TAA,RUP-EAA,RUP-BCAA,RUP-Lys and RUP-Met in concentrated feeds were higher generally than in roughages. Small intestinal digestibility of RUP-Arg of most feedstuffs was higher than other RUP-AA,and RUP-Lys was higher than RUP-Met.