Residual feed intake and blood variables in young Nellore cattle

Abstract

This study was conducted to evaluate associations of performance traits, feed efficiency, and blood variables with residual feed intake (RFI) in growing Nellore cattle. A total of 118 growing Nellore animals, 62 males and 56 females, were used. A diet containing 2 Mcal/kg was offered ad libitum and individual DMI was measured over a period of 84 d. Animals were classified as low (≤0.128 kg/d; = 40), medium (-0.128 to 0.135 kg/d; = 42), or high RFI (>0.135 kg/d; = 36). Blood samples were collected at the beginning and at the end of the test for determination of plasma concentrations of different blood variables. Data were analyzed using a mixed model that included the random effect of facility the fixed effects of sex, RFI class, and linear effect of the covariate age within sex; and the interaction between RFI class and sex. Least squares means were compared using a -test. Animals of different RFI classes presented similar performance traits and different DMI. Low-RFI animals consumed, on average, 0.670 kg/d less DM than high-RFI animals. Among the blood variables analyzed, significant differences among RFI classes were observed for urea, IGF-1, and insulin. Plasma urea concentrations were lower (5.58 vs. 5.91 mmol/L) and insulin (4.45 vs. 3.70 μIU/mL) and IGF-1 (433 vs. 399 ng/mL) concentrations were higher in low-RFI animals when compared to high-RFI animals. Plasma concentrations of urea, IGF-1, and insulin can be used as indicators of feed utilization efficiency in Nellore cattle.

Feed utilization, blood metabolites and ingestive behavior in Sahiwal calves divergently selected for low and high residual feed intake

“…well with the 19% differences in the Murrah buffalo calves divergently selected for low (-0.14 kg/d) and high RFI (0.14 kg/d), with no difference in body weight gain (SHARMA et al, 2016). NASCIMENTO et al (2015) noted that low RFI (≤0.128 kg/d) Nellore cattle consumed 7.2 kg DM/d, which was 14.0% less feed than animals with high RFI (>0.135 kg/d), although no significant differences in ADG were observed among RFI classes. A 10% reduction in DMI by the low RFI Murrah buffalo calves compared to high RFI (-0.20 vs. 0.23 kg DM/d), despite no differences in body weight gain, was reported by BOSE et al (2014).…”

“…Similar to the findings of the present study, PAULA et al (2013) and observed a negative correlation (r = -0.45) between RFI and the mean concentration of serum creatinine, and a comparison of the two RFI groups showed significant differences for this variable. However, no differences in the levels of blood creatinine between the low and high RFI groups were observed by SHARMA et al (2016) andBOSE et al (2014) in Murrah buffalo calves, or by NASCIMENTO et al (2015) in Nellore cattle.…”

“…The better feed efficiency in low RFI calves compared to high RFI calves have also been shown through traditional measures of feed efficiency. Low RFI animals showed greater residual weight gain, residual intakeweight gain, feed efficiency, and PEG, as well as lower FCR, than animals with medium and high RFI, respectively (NASCIMENTO et al, 2015). BOSE et al (2014and SHARMA et al 2016 also noted better FCR in low RFI animals than high RFI animals.…”

Biological mechanisms related to differences in residual feed intake in dairy cows

“…Kelly et al (2010b) and Nascimento et al (2015) found that insulin may affect feed efficiency, but we found no changes when we examined measures related to glucose metabolism, such as glucose and insulin, which might be related to a decrease in insulin sensitivity in muscle tissue of energetically inefficient animals (Richardson et al, 2004;Brown, 2005). Considering variability of insulin sensitivity, we do not suggest the use of insulin or glucose as indicators of RFI.…”

“…In accordance with the present findings, Kelly et al (2010a) reported that systemic IGF-1 in yearling Limousin × Holstein-Friesian heifers was not related to RFI, as did Kundu et al (2014). Conversely, IGF-1 was determined to be genetically correlated in a positive manner with RFI in growing bulls (Moore et al, 2005) and Nellore cattle (Nascimento et al, 2015). The likely explanation for this inconsistency is that, in most studies to date in which IGF-I was correlated with RFI, the animals were measured at a young age shortly after weaning (Moore et al, 2005), animals were consuming a roughage-based diet (Brown, 2005), and consequently, animals might be expected to have a greater rate of lean tissue gain and reduced carcass fatness.…”