Genetic parameters and breed differences for feed efficiency, growth, and body composition traits of young beef bulls

Abstract

breed differences for feed efficiency, growth, and body composition traits of young beef bulls. Can. J. Anim. Sci. 84: 177-185. Genetic associations between feed efficiency, growth, and live ultrasound measured body composition traits were studied in purebred beef bulls of six breeds in Ontario bull test stations from 1991 to 2000. Feed traits included average daily feed intake (FI), feed conversion ratio (FCR), and residual feed intake [feed intake adjusted for production alone (RFIp) or production and backfat thickness (RFIb)]. Growth traits were average daily weight gain (ADG), mid-test metabolic weight (MW), hip height (HH), and scrotal circumference (SC). Body composition traits included ultrasound backfat thickness (BF), longissimus muscle area (LMA), and predicted percentage of intramuscular fat (IFAT). Bulls were measured every 28 d for weight and individual feed intake, and at the end of test for ultrasound body composition traits. Number of records per trait ranged from 2284 (FI) to 13 319 (ADG). Fixed effects of test group, breed and end of test age (within breed), and random effects of animal and herd of origin were modeled using REML bivariate analyses for all traits. Heritability estimates were moderate for all traits (0.30 to 0.55), except for IFAT (0.14). The genetic correlation between RFIp and RFIb was high (0.99) within breeds, but breeds ranked differently with respect to RFIp and RFIb. Genetic correlations of RFIb with ADG and backfat thickness were essentially zero, which indicate that selection on residual feed intake could be implemented to reduce feed intake and improve feed conversion without compromising growth or changing levels of subcutaneous fat.

Live animal measurements, carcass composition and plasma hormone and metabolite concentrations in male progeny of sires differing in genetic merit for beef production

“…The significant negative relationship between sire EPD DMI with carcass meat proportion is consistent with the findings in dairy and late-maturing beef breed cross comparisons, whereby Holstein/Friesian cattle were shown to have higher intake and lower carcass meat proportion than similarly managed Charolais cattle (Keane et al, 1990;McGee et al, 2005). Furthermore, Schenkel et al (2004) reported a significant genetic correlation of 0.24 between feed intake and ultrasonically measured back fat thickness, which is consistent with the increases in scanned fat depth and carcass fat proportion per unit increase in sire EPD DMI observed in the present study. Clarke et al (2009) reported an increase in DM intake with increasing sire EPD DMI .…”

Visceral organ weights, digestion and carcass characteristics of beef bulls differing in residual feed intake offered a high concentrate diet

“…Animal performance and feed efficiency Overall ADG, initial BW and DMI of the bulls used in the current study are within the ranges observed by Schenkel et al (2004), Lancaster et al (2009) and Kelly et al (2011) for growing beef bulls offered an energy dense, high concentrate diet. The current study has shown that for growing beef bulls, weight and growth accounted for a substantial proportion (0.79) of the variation in RFI and that high RFI bulls had a 14% greater DMI than low RFI bulls for the same level of production.…”

Feed efficiency of Nellore cattle selected for postweaning weight

“…Correlations found in this work were consistent to the ones reported in literature (Schenkel et al, 2004;Nkurumah et al, 2004), evidencing that average daily gain and body weight are variables that influence the intake by the animal. According to Tedeschi et al (2006) cattle that have genetic potential for faster growth, at the same growth stage, are the ones that consume more food in order to satisfy the increases on nutrient requirement.…”