76 Nutrient intake apparent total tract nutrient digestion and N excretion in backgrounding cattle fed increasing amounts of grape pomace.

摘要

Although grape pomace (GP) is increasingly available for use as cattle feed, there is still limited information on its feeding value. Therefore, our objective was to determine the effects of feeding increasing amounts of GP in backgrounding cattle diets on nutrient intake and digestibility, ruminal fermentation, and nitrogen (N) excretion. Six ruminally-cannulated heifers (mean initial BW ± SD, 614 ± 49.5 kg) were used in a replicated 3 × 3 Latin square with 21-d periods (14 d for adaptation). Heifers were fed backgrounding diets containing 0, 15, or 30% GP (DM basis); GP partially replaced alfalfa silage. Dry matter intake was measured daily. Ruminal fluid was collected from d 19 to 21 to determine fermentation characteristics, as were feces and urine to measure apparent total tract nutrient digestibility and N excretion. Plasma was collected 3 h post-feeding on d 21. Data was analyzed using PROC MIXED in SAS. Dry matter intake tended ( = 0.07) to be greater, and ADF and CP intake were greater ( < 0.02) for heifers fed the 15 and 30 than 0 % GP diet. However, DM, OM, NDF, ADF, and CP digestibility decreased ( ≤ 0.01) as dietary GP content increased in the diet. Although there was no diet effect ( ≥ 0.33) on rumen NH -N, plasma urea-N, and urine N and urea-N excretion, fecal N output was greatest ( < 0.01) for heifers fed 30% GP. Apparent N retention tended to be greater ( = 0.06) for heifers fed the 15% than 0 and 30% GP diet. In summary, although it increased intake, increasing the dietary inclusion level of GP reduced apparent total tract DM, ADF, and CP digestion. However, N retention tended to be greater for heifers fed the 15 than 0 and 30 % GP diets.