Residual feed intake adjusted for backfat thickness and feeding frequency is independent of fertility in beef heifers

Abstract

Basarab, J. A., Colazo, M. G., Ambrose, D. J., Novak, S., McCartney, D. and Baron, V. S. 2011. Residual feed intake adjusted for backfat thickness and feeding frequency is independent of fertility in beef heifers. Can. J. Anim. Sci. 91: 573–584. This study examined the effects of residual feed intake (RFI), RFI adjusted for off-test backfat thickness (RFIfat) and RFI adjusted for off-test backfat thickness and feeding event frequency (RFIfat & activity) on heifer fertility and productivity. Beef heifers (n=190) were monitored for individual daily feed intake and feeding event activity over 108–112 d using the GrowSafe System® and assessed for age at puberty based on plasma progesterone concentration. Individual animal daily feed intake, feeding event activity and off-test backfat thickness were then used to calculate RFI, RFIfat and RFIfat & activity and group heifers as either negative ([−], RFI<0.0) or positive ([+], RFI≥0.0) for RFI. Heifers averaged 298 kg (SD=34) in body weight, were 276 days of age (SD=19) at the start of test, grew at 0.90 kg d−1 (SD=0.21), consumed 7.62 kg DM head−1 d−1 (SD=0.84) and had a feed conversion ratio of 8.93 (SD=2.43). Age (351 d, SD=43) and weight (367.3 kg, SD=45.0) at puberty were similar between [−] and [+] RFI heifers, but age at puberty was delayed in [−] RFIfat (P=0.04) and RFIfat & activity (P=0.08) heifers compared with [+] RFIfat and RFIfat & activity heifers. Efficient or [−] RFI heifer exhibited a lower pregnancy (76.84 vs. 86.32%, P=0.09) and calving rate (72.63 vs. 84.21%, P=0.05) compared with [+] RFI heifers. These differences were partially removed in [−] RFIfat and completely removed in [−] RFIfat & activity compared with their [+] RFI counterparts (pregnancy rate, 80.85 vs. 82.29%, P=0.80; calving rate, 75.53 vs. 81.25%, P=0.34). No differences were observed between efficient and inefficient heifers in calving difficulty, average calving date, age at first calving, calf birth weight, calf pre-weaning ADG, calf weaning weight and heifer productivity. However, [+] RFI heifers exhibited a 1.9-fold higher calf death loss compared with [−] RFI heifers (11.11% vs. 5.71%, P=0.24). This difference was more pronounced in [+] RFIfat and [+] RFIfat & activity heifers, which exhibited 2.2-fold (11.84% vs. 5.33%, P=0.15) and 3.0-fold (12.66% vs. 4.17%, P=0.06) higher calf death loss compared with [−] RFI heifers. There was no relationship of RFI adjusted for backfat thickness and feeding activity on fertility traits indicating that backfat thickness and feeding activity may be associated with feed intake and should be considered when selecting heifers for improved feed efficiency.

Effect of post-weaning residual feed intake classification on grazed grass intake and performance in pregnant beef heifers

“…Low RFI fat heifers had similar (P !0.10) feeding duration, head down time, and feeding event frequency compared with high RFI fat heifers. However, significantly lower feeding event frequency (events/day; Kelly et al 2010a;Basarab et al 2011), eating rate (g min (1 ; Kelly et al 2010a), and feeding duration (min d…”

“…Following weaning, heifers were housed in a drylot pen and fed once daily for ad libitum intake of barley silage until the beginning of the feed intake test adjustment period. Heifers were then fed twice daily for ad libitum intake a 90% barley silage and 10% rolled barley grain total mixed ration (as fed; (1 )] were collected as previously described by Basarab et al (2007Basarab et al ( , 2011. Feed samples were collected weekly and composited by month for chemical analysis, and showed (Table 1) that the diet met the nutrient requirements for replacement heifers (NRC 2000).…”

“…The details of RFI fat calculation in drylot condition were provided by Basarab et al (2003Basarab et al ( , 2011. Body weight at the beginning of the test, mid-point weight (MIDWT), and average daily gain (ADG) were calculated by a linear regression of the animal's observed BW against day on test (Basarab et al 2003).…”

Invited review: Improving feed efficiency in dairy production: challenges and possibilities

“…Because feed intakes and body condition scores did not differ during mid lactation between the divergent groups of lactating heifers, significant negative impacts of selection for reduced RFI during growth on fertility are not anticipated. Furthermore, research in growing beef heifers indicated that selection for reduced RFI should have no negative impacts on heifer or cow fertility, but may delay the time of sexual maturity (Basarab et al, 2011;Crowley et al, 2011;Shaffer et al, 2011). To date, no studies have evaluated RFI in dairy cows during the dry period or the relationship between RFI during growth or lactation and subsequent feed intake, BW or body condition during the dry period.…”

Genotype Imputation Methods and Their Effects on Genomic Predictions in Cattle

“…Values of RFI for all 1800 genotyped animals in the Illumina 50K panel were adjusted for contemporary groups including herd-year-sex, age at feedlot test and breed composition. The animal populations and traits are described in Basarab et al [48], Chen et al [49] and Lu et al [46].…”