TITLE:
Effects of physiological age on residual feed intake of growing heifers
AUTHORS:
Andrea N. Loyd, Charles R. Long, Andrew W. Lewis, Ronald D. Randel
KEYWORDS:
Cattle; Puberty; Residual Feed Intake
JOURNAL NAME:
Open Journal of Animal Sciences,
Vol.1 No.3,
October
14,
2011
ABSTRACT: Using a retrospective evaluation of feed effi- ciency, this study investigated the effects of physiological age on residual feed intake (RFI) in growing heifers. Data were collected during 1973 and 1974 at the McGregor location of the Texas Agricultural Experiment Station. Heifers (n = 77) were obtained from a large crossbreed- ing program utilizing a five-breed diallel mating scheme using Angus, Brahman, Hereford, Hol- stein and Jersey breeds. At approximately 6 months of age, pre-pubertal heifers were indi- vidually penned and received ad libitum access to a balanced diet. Individual feed intake and body weight data were collected at 28-day in- tervals for 84 days prior to puberty and for 90 days after puberty. The diet was changed at puberty to provide a lower energy density. Con- sidering all females as cohorts, RFI was calcu- lated for each heifer for each period using separate models for the pre- and post-pubertal periods. A moderate, positive Pearson correla- tion (r = 0.48; P