Residual feed intake studies in Angus-sired cattle reveal a potential role for hypothalamic gene expression in regulating feed efficiency1,2

Abstract

Mechanisms underlying variation in residual feed intake (RFI), a heritable feed efficiency measure, are poorly understood while the relationship between RFI and meat quality is uncertain. To address these issues, 2 divergent cohorts consisting of High (HRFI) and Low (LRFI) RFI individuals were created by assessing RFI in 48 Angus-sired steers during a 70 d feeding trial to identify steers with divergent RFI. The association of RFI with indices of meat quality and expression of genes within hypothalamic and adipose tissue was then determined in LRFI and HRFI steers. While on test, feed intake was recorded daily with BW and hip heights recorded at 14 d intervals. Ultrasound measurements of rib eye area (REA) and backfat (BF) were recorded initially and before harvest. Carcass and growth data were analyzed using a mixed model with RFI level (LRFI, HRFI) as the independent variable. The least-square means (lsmeans) for RFI were -1.25 and 1.51 for the LRFI and HRFI cohorts (P < .0001). Dry matter intake was higher for the HRFI individuals versus the LRFI steers (P < .0001) while on test BW gain was not different between the 2 groups (P < 0.73). There were no differences detected in marbling score (P < 0.93), BF (P < 0.61), REA (P < 0.15), yield grade (P < 0.85) or objective Hunter color measures between LRFI and HRFI steers indicating that there was no relationship between RFI and meat quality. Neuropeptide-Y (NPY), relaxin-3 (RLN3), melanocortin 4 receptor (MC4R), and GnRH mRNA expression was 64%, 59%, 58%, 86% lower (P < 0.05), respectively, while gonadotropin inhibiting hormone (GnIH) and pro-opiomelanocortin (POMC) mRNA expression was 198% and 350% higher (P < 0.01) in the arcuate nucleus of LRFI steers. Expression of agouti-related protein (AGRP), relaxin/insulin-like family peptide receptor 1 (RXFP1), and melanocortin 3 receptor mRNA was similar between LRFI and HRFI animals. Pituitary expression of FSHβ (P < 0.03) and LHβ (P < 0.01) was correlated to hypothalamic GnRH levels suggesting that changes in gene expression within the arcuate nucleus had functional consequences. Leptin mRNA expression was 245% higher in the adipose tissue of LRFI steers consistent with lower levels of NPY and higher expression of POMC in their hypothalami. These data support the hypothesis that differences in hypothalamic neuropeptide gene expression underlie variation in feed efficiency in steers while the gonadotropin axis may also influence feed efficiency.

Gene expression profiling of hormonal regulation related to the residual feed intake of Holstein cattle

“…Perkins et al (2014) reported significant differences in the mRNA expression of leptin and NPY between high and low RFI Angus-sired cattle. They attributed these differences to hypothalamic neuropeptide gene expression, concluding that these might underlie variation in feed efficiency and that the gonadotropin axis might also influence the RFI [8]. In common with their study, we found that LEP, JAK1, LEPR, STAT, and SOCS3 were down-regulated and that NPY was up-regulated in the low RFI group based on the gene-chip microarrays (Fig.…”

“…Perkins et al (2014) found that neuropeptide-Y (NPY), relaxin-3 (RLN3), the melanocortin 4 receptor (MC4R), and gonadotropin-releasing hormone (GnRH) mRNA expression were 64%, 59%, 58%, and 86% lower, respectively, in the arcuate nucleus of low RFI steers, whereas gonadotropin inhibiting hormone (GnIH) and pro-opiomelanocortin (POMC) mRNA expression was 198% and 350% higher than the high ones. Serum tests among different RFI coefficients have been greatly researched because of the easily obtained samples in dairy cattle [8]. Kelly et al (2010) measured concentrations of insulin-like growth factor-1 (IGF-1), insulin, and various metabolites in finishing heifers, and found that insulin concentrations were correlated with RFI [9].…”

Nutrient utilisation and methane emissions in Sahiwal calves differing in residual feed intake

“…Further, the biological basis for high efficiency in Group Low RFI is thought to be due to better energy and protein metabolism (Karisa et al 2014), improved mitochondrial respiration rate (Kolath et al 2006), increased gene expression of gut microorganisms (Bezerra et al 2013) or hypothalamus (Perkins et al 2014) as observed for Angus-sired cattle. Altogether these factors could improve feed efficiency.…”

“…RFI is the difference between actual intake and the expected requirements of feed for maintenance and body weight gain and is independent of mature weight and average daily gain (ADG) (Nkrumah et al 2006;Lawrence et al 2013;Steyn et al 2014) and thus will be desirable as a nutritional tool for genetic improvement of the livestock (reviewed by Bezerra et al 2013). RFI, being moderately heritable (h 2 for cattle ranges from 0.25 to 0.49), has been studied as a selection method for feed efficiency in beef cattle (Kolath et al 2006;Nkrumah et al 2006;Hegarty et al 2007;Jones et al 2011;Perkins et al 2014), dairy cows (Lawrence et al 2013;Steyn et al 2014), Murrah buffaloes (Bisitha et al 2014), sheep (Muro-Reyes et al 2011Redden et al 2014), pigs (Grubbs et al 2013), chicken (Zhen-qiang et al 2014), rabbits (Larzul and de Rochambeau 2005) and minks (Hedemann and Damgaard 2012), although mechanisms underlying variation in RFI are poorly understood (Perkins et al 2014). Recently, Berry and Crowley (2013) and Bisitha et al (2014) concluded that RFI is an effective and robust index of feed efficiency evaluation in growing bovines.…”

A glimpse of the future in animal nutrition science. 2. Current and future solutions

“…Since about two-thirds of the cost of producing beef is due to the expense of feed inputs, strategies that improve efficiency of feed utilization will substantially increase the economic viability of beef production systems. In fact, Weaber (apud Perkins et al, 2014) estimated that the U.S. beef industry could save $1 billion annually by reducing residual feed intake (RFI) by 10% (equivalent to reducing daily intake by 0.9 kg per animal). Furthermore, as improvements in feed efficiency will also reduce nutrient excretions and GHG emissions (Waghorn and Hegarty, 2011), discovery and adoption of technologies to enhance genetic merit for feed efficiency is arguably one of the most cost-effective strategies available to meet future demands for animal protein in a more sustainable manner.…”