Relationships of metabolic hormones and serum glucose to growth and reproductive development in performance-tested Angus, Brangus, and Brahman bulls

Abstract

Understanding mechanisms that regulate growth and reproduction are important for improving selection strategies in cattle. In this study, Angus, Brangus, and Brahman bulls (n = 7 per breed) of similar age were selected from a group of 65 weanlings. Bulls were evaluated after weaning (i.e., approximately 6 mo of age) for 112 d for serum concentrations of metabolic hormones and glucose, growth, and reproductive traits. Performance data and blood sera were collected on d 0, 28, 56, 84, and 112. Sera were also collected in periods from d 50 to 59 (56D) and 103 to 112 (112D). Angus bulls were heavier (P < 0.05) throughout the study than Brahman bulls and were heavier than Brangus bulls on d 56, 84, and 112. Initial and final BW for Angus, Brangus, and Brahman bulls were 292.7, 260.6, and 230.4 and 468.3, 435.6, and 350.7 +/- 12 kg, respectively. Conversely, Brahman bulls had greater hip height (P < 0.05) than Brangus, and Brangus were taller (P < 0.05) than Angus. Angus bulls had the greatest (P < 0.05) scrotal circumference (SC) and Brahman bulls the least. Mean SC across days was 31.5, 29.7, and 25.0 +/- 0.6 cm for the three respective breeds. Serum testosterone was greater (P < 0.01) in Angus and Brangus bulls (10.0 and 8.9 +/- 1.4 ng/mL) than in Brahman bulls (4.0 +/- 1.4 ng/mL) throughout the study. After d 112, 100, 86, and 57% of the Angus, Brangus, and Brahman bulls passed a breeding soundness exam (P = 0.51). Serum concentrations of IGF-I and leptin were greater (P < or = 0.06) in Angus bulls on d 56, 84, and 112 than in Brangus and Brahman bulls. Serum concentrations of GH (P < 0.08) and glucose (P < 0.03) were greater in Brangus bulls than in Angus or Brahman bulls throughout the study. Prediction analyses suggested that serum concentrations of leptin could be used to predict (P < or = 0.08) BW and SC (R2 > 0.82) in the 56D and 112D periods among these breeds. Leptin was also useful in predicting (P < or = 0.09) serum concentrations of GH and testosterone in the 112D period (R2 > 0.32). Residual correlation analyses with the effect of breed removed suggested that leptin was correlated (r > or => 0.53, P < 0.05) with both SC and serum testosterone. Angus and Brahman cattle differ in phenotype, level of adiposity, and rate of sexual development. Data herein suggest that these characteristics could be due to varying mechanisms by which metabolic hormones such as leptin, GH, and(or) IGF-I are regulated.

Effect of leptin gene polymorphisms on growth, slaughter and meat quality traits of grazing Brangus steers

“…Just to give one example, polymorphisms in the leptin receptor have been significantly associated with production traits in beef cattle (Schenkel et al, 2006). Differences in circulating leptin levels have been reported among Angus, Brahman and Brangus (Thomas et al, 2002), with the British breed having the highest. However, this kind of results has not been linked to variation at the genomic level.…”

Association of polymorphisms in growth hormone and leptin candidate genes with live weight traits of Brahman cattle

“…Leptin, an adipocyte-derived hormone, is related to different physiological functions and associated with some productive and reproductive traits in livestock (Mácajová et al, 2004). It is considered as a predictor of live weight, scrotal circumference, and reproductive hormones (Thomas et al, 2002). In the present study, the C allele produced a substitution effect of 9.7 kg (P = 0.0007) with a significant difference between the CC genotype in comparison to heterozygous and homozygous (CT and TT) genotypes (Table 3).…”

Genetic markers of body composition and carcass quality in grazing Brangus steers

“…The phenotypic variability in relevant traits for beef production between Bos taurus and Bos indicus has been studied for many years (Wheeler et al, 2001;Thomas et al, 2002;Brunelle et al, 2008). Composite breeds such as Brangus take advantage of this variability, combining the desirable traits for beef production from Angus (B. taurus) with the rusticity and adaptability of Brahman (B. indicus).…”

“…In this respect, genes involved in the control of the somatotropic axis, such as growth hormone (GH), growth hormone receptor (GHR) or insulin-like growth factor I (IGFI) are primary candidates for their influence in many traits related to growth rate and body composition (Hale et al, 2000;Thomas et al, 2002;Farber et al, 2006).…”