Effects of enzymatically hydrolyzed yeast supplementation and supplementation frequency on nitrogen balance and apparent diet digestibility in periparturient beef cows

Abstract Text: We evaluated effects of enzymatically hydrolyzed yeast (EHY) and supplementation frequency on nitrogen balance and digestibility parameters in periparturient beef cows. Eighty multiparous cows fed a common brome hay-based diet (CP = 8.0 ± 0.17%) were blocked by expected calving date and stratified by BCS before random assignment of treatment. Beginning 88 ± 5 d prior to parturition, cows were provided 1-kg daily or 3-kg every 3-d of a soybean hull-based supplement that contained 0 or 3 g/kg EHY. The daily supplement was designed to meet ruminal N requirements. Cows were provided a bolus of TiO₂ (10 g/d) at the time of supplement feeding for 10-d beginning 64-d prior to calving and again 34-d prior to calving. Fecal and urine samples were collected each 12-h for 6-d beginning 4-d after cattle first received TiO₂. Initiation of sample collection was delayed between each d so that composite samples of urine and feces were representative of every 2-h in a 24-h period. Samples of hay, supplement, feces and urine were analyzed for DM, OM, N, NDF, ADF and ADIA. Fecal TiO₂ allowed calculation of fecal output and ADIA was used to calculate hay intake. Urine creatinine acted as a urine output marker. Data were analyzed as a 2 × 2 factorial design. There were no interactions of EHY, supplementation frequency or sampling time. Neither EHY (P = 0.31) or supplementation frequency (P = 0.57) affected estimates of DMI, but DMI estimates tended to increase (P = 0.08) from 10.8 to 11.1 ± 0.2 kg/d as cattle neared parturition. Apparent total-tract digestibility of DM (54.4 ± 0.6%), OM (58.2 ± 0.6%), NDF (51.7 ± 0.8%) and ADF (46.0 ± 0.9%) was not different (P > 0.10) between EHY and control; however, daily supplementation increased (P ≤ 0.06) apparent total-tract digestibility of DM (55.6 vs. 54.1 ± 0.8%), OM (58.9 vs. 57.5 ± 0.6%), NDF (52.6 vs. 50.8 ± 0.8%) and ADF (46.8 vs. 45.2 ± 0.9%) compared to supplementation every 3-d. We observed no effects of EHY (P = 0.55) or supplementation frequency (P = 0.60) on N retention (15.1 ± 4.6 g/d); however, N retention decreased (P = 0.03) from 21.3 to 8.8 ± 4.4 g/d as cattle neared parturition. These data suggest that daily supplementation can provide benefit to diet digestion, but increases in diet digestibility in response to more frequent supplementation were not related to changes in N retention.

Keywords: Cattle, supplementation, digestion