Comparison of milk production, intake, and total-tract nutrient digestion in lactating dairy cattle fed diets containing either wheat middlings and urea, commercial fermentation by-product, or rumen protected soybean meal

摘要

The objective of this study was to evaluate the effectsof a commercially available fermentation by-product ina diet containing adequate rumen-degradable protein(RDP) on milk performance, intake, and total-tractnutrient digestion in lactating dairy cattle. Primiparous(n = 48) and multiparous (n = 144) lactating dairycattle were stratified by milk production and randomlyallocated into 12 pens containing 4 primiparous and12 multiparous animals each. Cattle averaged 118 d inmilk and 712 kg of body weight at trial start. Treatmentdiets, on a dry matter (DM) basis, consistedof 42% corn silage, 13% alfalfa hay and silage, 20%grain corn, and 25% protein premix containing eithersoybean meal, wheat middlings, and urea (SBM+U),soybean meal and fermentation by-product (SBM+F),or soybean meal and rumen-protected soybean meal(RP-SBM). All 3 diets provided a similar level (DM basis)of neutral detergent fiber analyzed using α-amylaseand sodium sulfite and corrected for ash content (31%),crude protein (CP, 14.9%), starch (26%), and metabolizableenergy (2.7 Mcal/kg), and differed in sourcesof RDP. The trial consisted of a 2-wk adaptation andcovariate period during which all cows were fed theRP-SBM diet and covariate measurements were taken.Pens were then randomly allocated to treatments, andweekly measurements of milk production, intake, bodyweight, and condition score were taken for 10 wk. Alldata were analyzed using the Proc Mixed procedure inSAS (SAS Institute Inc., Cary, NC). Increased DM intakewas observed for cows fed SBM+F compared withcows fed SBM+U and RP-SBM (28.3 vs. 26.9 and 26.7kg/d, respectively). Cows fed SBM+F produced moreenergy-corrected milk (45.3 kg/d) compared with cowsfed SBM+U and RP-SBM (43.6 and 43.7 kg/d, respectively).Milk protein yield was also increased in cowsfed SBM+F. No differences were observed with bodyweight or condition score gain throughout the trial. Apparenttotal-tract digestibility of fiber was decreased incows fed SBM+F, likely as a result of increased intake.Responses are consistent with previous research in ourlaboratory that demonstrated a decrease in ruminal CPdegradation, leading to an increase in metabolizableprotein supply in the small intestine. The fermentationby-product might be useful in diets containing adequateamounts of RDP from soybean meal or alfalfa. Theresults from this experiment demonstrate beneficialmilk performance responses to fermentation by-productwhen fed with a source of RDP.