| Exp.1: Three Luxi Yellow beef bulls (averaging initial BW=540±30kg) with ruminalcannula, proximate duodenal (simple T-piece) and terminal ileal fistulae were used in a3×3Latin square design to investigate the effects of different levels of cottonseed in diets onrumen fermentation and digestibility of nutrients in beef cattle, and to make reference tooptimum level of cottonseed in beef cattle diets. Three experimental diets contained contral(CT):basal diet; middle cottonseed (MC):11.3%cottonseed and high cottonseed (HC):21.8%cottonseed. The experiment included3feeding periods with21days each, and each periodcomprised a8-day adaptation and13-day collection.(1)During a feeding period, the mean pHof three treatments CT, MC, and HC were6.60,6.58, and6.63, respectively (P>0.05). Therewere no significant differences among treatments in pH of the same time (P>0.05). But theminimum value of ruminal pH was observed at2to4h after feeding, then ascended gradually.(2) During a feeding period, the mean pH of three treatments CT, MC, and HC were7.09,7.21, and6.95mg/100mL, respectively (P>0.05). There were no significant differencesamong treatments in NH3-N of the same time (P>0.05). But there was a peak value ofruminal NH3-N concentration at2h after feeding and then declined gradually.(3) During afeeding period, the mean total VFA of three treatments CT, MC, and HC were87.47,92.71,and88.91mmol/L, respectively (P>0.05). There were no significant differences amongtreatments in total VFA, acetate, propionate, butyrate, and A/P of the same time (P>0.05). Themean total VFA, acetate, propionate, butyrate, and A/P of treatment MC was the hightest.(4)There were no significant differences among treatments in intake N, fecal N, urine N,digested N, and appsrent digestibility of N (P>0.05). The mean fecal N and urine N oftreatment MC were the hightest. The mean digested N and appsrent digestibility of N oftreatment MC were the hightest.(5) During a feeding period, there were no significantdifferences among treatments in total digestive tract digestibility of DM, OM, NDF, and ADF(P>0.05), and that of MC was the highest. There were no significant differences amongtreatments in duodenal flow, Ileal flow, fecal excretion, small intestinal digestibility, and largeintestinal digestibility (P>0.05). The MC increased reticuloruminal digestibility of NDF(P<0.05), but there were no significant differences among treatments in reticuloruminal digestibility of DM, OM, and ADF.The result of this experiment indicated: There were no significant differences amongtreatments in rumen fermentation and digestibility of nutrients. In this experiment, theoptimum level of cottonseed was11.3%.Exp.2: This trial was conducted to assess the effects of CP levels and cottonseed meal(replacing soybean meal) on the fattening of Beef steers. Forty healthy28-month-oldfirst-filial generation steers (average weight was678±122.22kg, P>0.05) were fed differentdiets containing two levels of CP and adding different amount of cottonseed for240d.(1)The results showed dietary supplementation of14.8%CP increased (P<0.05) the carcassyield, meat percentage, fat thickness of rib, and backfat thickness of steers, but had no effecton the ADG, eye muscle area, percentage of superior beef relative to body weight, and feedconversion efficiency (P>0.05). Replacing soybean meal with cottonseed meal on conditionthat the CP content was12.8%and14.8%had no effect on the ADG and carcass traits ofsteers (P>0.05).(2) The results showed dietary supplementation of14.8%CP increased(P<0.05) total VFA, acetate, and propionate, but had no effect on the pH, NH3-N, butyrate,and A/P (P>0.05). Replacing soybean meal with cottonseed meal on condition that the CPcontent was12.8%and14.8%had no effect on pH, NH3-N, acetate, propionate, and A/P(P>0.05), but decreased (P<0.05) total VFA and butyrate.(3) During a experimental period,there were no significant differences among CP levels and replacing soybean meal withcottonseed meal in IGF-1, IGF-2, ACC, and HSL (P>0.05).(4) During a experimental period,there were no significant differences among CP levels and replacing soybean meal withcottonseed meal in prevotella ruminicola, ruminococcus flavefaciens, ciliate protozoa,butyrivibrio fibrisolvens, and streptococcus bovis (P>0.05).The result of this experiment indicated: Using of cottonseed meal instead of soybeanmeal in the later stage of fattening of beef cattle was viable to reduce feeding costs. Theoptimum level of CP for fattening of first-filial generation steers was14.8%. |
PDF Full Text Request