Growth, feed intake and maternal performance of Angus heifers from high and low feed efficiency selection lines

Abstract

Feed conversion efficiency is an important factor affecting profitability for cow-calf production systems. One method of characterising feed conversion efficiency is by calculating residual feed intake (RFI), the difference between measured and expected feed intakes. A high RFI value indicates low feed efficiency while a low RFI value indicates high feed efficiency. The present experiment used 49 Angus heifers sired by Angus bulls selected for high or low RFI. The progeny were bred on commercial farms and then transferred to Massey University at weaning at ~200 days of age. The heifers were weighed at ~30-day intervals and were mated at 15 months, calved at 2 years old and reared their calf to ~160 days of age. Each heifer had recorded its own liveweight gain (from its weaning to weaning of its first calf), herbage intake at 350 and 450 days of age using the n-alkane technique and maternal performance (calf production). These records were analysed to estimate the RFI of each heifer, and to determine differences in RFI between selection lines. There were no significant differences (P > 0.05) in liveweight or dry matter requirements between selection lines at Day 350, but differences were significant (P < 0.05) at Day 450 such that the high feed efficiency line were 24.6 kg heavier and required an extra 0.32 kg/head.day of herbage. There were no significant differences (P > 0.05) between the two lines in herbage intake or RFI measured at either Days 350 or 450. There were no differences (P > 0.05) in pregnancy rates, calf birth dates or birthweights, estimated 24-h milk production or calf weaning weights between the two lines. This experiment shows that beef cattle selected for low RFI have higher growth rates and heavier liveweights than cattle selected for high RFI; both lines had similar calf production at first breeding.

Invited review: Improving feed efficiency of beef cattle – the current state of the art and future challenges

“…In terms of milk composition, Montanholi et al (2013b) reported a negative relationship between RFI and milk lactose concentration (r = −0.29) in beef cows but no association with other milk constituents. Consistent with reported results on cow milk yield, calf pre-weaning growth was not associated with maternal status for RFI (Lawrence et al, 2013;Morris et al, 2014). Given that maternal weaning weight is representative of dam milk yield and, at a genetic level, Crowley et al (2011) found no relationship between maternal weaning weight and RFI of growing males, these findings corroborate Feed efficiency in beef cattle the absence of a phenotypic association between cow RFI ranking and milk yield or progeny performance pre-weaning.…”

“…In terms of reproductive performance, no differences were found between high and low-RFI beef females with regard to pregnancy, calving and/or weaning rates (Basarab et al, 2007;Morris et al, 2014;Jones et al, 2016), although in other studies a lower pregnancy and calving rate (Basarab et al, 2011) and lower weaning rate (Copping et al, 2016;Hebart et al, 2016) was observed for low-RFI females. Donoghue et al (2011) and Hebart et al (2016) reported that low-RFI females calved later in the calving season than their high-RFI contemporaries; however, this was not evident in other studies (Morris et al, 2014). Crowley et al (2011) reported a negative, but not statistically significant, genetic correlation (r = −0.29) between age at first calving and RFI status in beef cattle.…”

“…Beef females previously ranked as divergent for RFI indoors offered a grass silage diet (Lawrence et al, 2012 and or hay (Meyer et al, 2008) did not differ in herbage intake when subsequently grazing pasture during first pregnancy (Lawrence et al, 2012), during gestation or late lactation (Meyer et al, 2008) or during lactation (Lawrence et al, 2013). Similarly, Morris et al (2014) reported no difference in herbage intake in grazing lactating beef heifers from highand low-RFI selection lines. In contrast, Manafiazar et al (2015) reported that heifers ranked as low-RFI in an outdoor drylot offered a barley silage-based diet had a lower intake of grazed herbage when subsequently measured as pregnant replacement heifers.…”

“…Residual feed intake ranking had no significant effect on milk yield of beef cows (McGee and Drennan, 2006;Lawrence et al, 2011;Morris et al, 2014). In terms of milk composition, Montanholi et al (2013b) reported a negative relationship between RFI and milk lactose concentration (r = −0.29) in beef cows but no association with other milk constituents.…”

Feed efficiency and maternal productivity of Bos indicus beef cows

“…The pregnancy, calving and weaning rates, days to calving, calf weight per cow exposed, and milk production evaluated over three reproductive cycles were similar, with high RFI (most efficient) cows exhibiting more subcutaneous fat at the beginning of the breeding season. Morris et al [26] also demonstrated that heifers born to sires with low EBV (most efficient) and high EBV (least efficient) for RFI did not differ in terms of pregnancy rate in the first or second breeding season, calf weight at birth or weaning, or milk production at 50, 100 and 150 days of lactation. These results encourage the use of negative RFI animals for sire and dam replacement in the herd, since these animals had decreased DMI with similar overall performance, making them more profitable due to lower input costs.…”