Effects of physiological age on residual feed intake of growing heifers

Abstract

Using a retrospective evaluation of feed efficiency, 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 crossbreeding program utilizing a five-breed diallel mating scheme using Angus, Brahman, Hereford, Holstein and Jersey breeds. At approximately 6 months of age, pre-pubertal heifers were individually penned and received ad libitum access to a balanced diet. Individual feed intake and body weight data were collected at 28-day intervals for 84 days prior to puberty and for 90 days after puberty. The diet was changed at puberty to provide a lower energy density. Considering all females as cohorts, RFI was calculated for each heifer for each period using separate models for the pre-and post-pubertal periods. A moderate, positive Pearson correlation (r = 0.48; P < 0.001) was detected between pre-and post-pubertal RFI. Furthermore, heifer RFI rank was compared between the pre-and post-pubertal periods using Spearman rank order correlation and a similar correlation (r = 0.46; P < 0.001) was revealed. This suggests that RFI determined during the pre-pubertal period may only be a moderate predictor of post-pubertal RFI. As a result, physiological age should be considered when evaluating cattle for feed efficiency using RFI.

JOINT ALPHARMA-BEEF SPECIES SYMPOSIUM: Interactions of feed efficiency with beef heifer reproductive development1

“…Brody (1945) suggested that puberty occurs at an infl ection point of the growth curve corresponding to a shift in body composition away from lean accrual and toward fat deposition. In a study where individual feed intake and puberty were recorded with the heifers fed for 84 ± 6 d before puberty and for 90 ± 4 d after puberty, there was a correlation of 0.48 (P < 0.001) between prepubertal and postpubertal RFI (Loyd et al, 2011). The conclusion from this report was that "physiological maturity should be considered when selecting cohorts of cattle for RFI evaluation."…”

Identification of Gene Networks for Residual Feed Intake in Angus Cattle Using Genomic Prediction and RNA-seq

“…Comparing predicted and observed ADG and DMI as well as RFI, a trend of increased ADG was observed in the finishing period with no difference in intake, in contrast to the predicted difference in genomic breeding values for DMI. This may be partially accounted for by the low n of our study and that RFI has been shown to be only lowly to moderately repeatable (0.29 to 0.62) [ 28 – 30 ]; however another cause could be differing trait definitions between the reference data (predominantly purebred bulls) and the test data (feedlot steers). American Angus DMI records depend on bull test data, which is generally collected before the bull is one year of age, making the DMI breeding value potentially more similar to a growing period DMI, which in our data showed a trend of decreased DMI in progeny of the low RFI sire relative to the high RFI sire.…”

Meat and sensory quality of major muscles from Angus, Charolais, and Angus crossbred steers with high and low residual feed intake

“…Angus and Charolais steers were tested for RFI at about 422 d of age (from June to August) and Angus crossbred steers at about 344 d of age (from April to June) due to anticipated finishing/slaughter date and limitations in GrowSafe capacity and availability. Testing for RFI was conducted at different times to accommodate differences in physiological age (Loyd et al 2011) between the genetic groups. The use of the GrowSafe feeding system was described in detail by Basarab et al (2003).…”