Feeding behavior, ruminal fermentation, and performance of pregnant beef cows differing in phenotypic residual feed intake offered grass silage.

摘要: This study examined the relationship of residual feed intake (RFI) and performance with feeding behavior ruminal fermentation variables in preg- nant beef cows offered a grass silage diet. Individual DMI (dry matter digestibility = 666 g/kg) was recorded on 47 gestating (mean gestation d 166, SD 26 d) Simmental × Holstein-Friesian for period 80 d. Cow BW, BCS, skel- etal measurements, ultrasonically scanned muscle fat depth, visual muscular score, fermentation, blood metabolites, were measured. Phenotypic RFI calculated as actual minus expected DMI. Expected computed each animal by regressing conceptus-adjusted mean BW 0.75 ADG over an 80-d period. Within breed, ranked into low (efficient), medium, or high groups. Overall (SD) values (kg/d), RFI, initial conceptus- adjusted 8.41 (1.09) kg/d, 0.01 (0.13) 646 (70) kg, −0.07 (0.32) respectively. High-RFI ate 25% 8% more than low- medium-RFI cows, Live weight not cor- related (P > 0.05), positively correlated (r 0.80; P 0.05) ADG, muscu- lar scores, skeletal calf birth weight, calving difficulty scores. All ultra- sonic depth measurements similar high-RFI except back thickness change, where low-RFI gained less < cows. Low-RFI had greater pH lower ammonia concentrations fluid compared to their contemporaries. Low- fewer 0.001) daily events, but these longer duration (min·feed event −1 ·d ). Despite this, total feed- ing shorter 0.001; min/d) lon- ger nonfeeding events showed that those consumed levels productivity, spent time engaged feeding-behavior-related activities, differed parameters. Feeding are significant (17%) contributory factor variation pregnant silage.