Genetics of adaptive traits in heifers and their relationship to growth, pubertal and carcass traits in two tropical beef cattle genotypes

Abstract

Abstract. Genetic analyses of tropical adaptive traits were conducted for two tropically adapted genotypes, Brahman (BRAH) and Tropical Composite (TCOMP). Traits included tick scores (TICK), faecal egg counts (EPG), buffalo fly-lesion scores (FLY), rectal temperatures under hot conditions (TEMP), coat scores (COAT), coat colour on a light to dark scale (COLOUR), navel scores (NAVEL) and temperament measured as flight time (FT). The data comprised adaptive measures recorded at specific times on 2071 heifers comprising 966 BRAH and 1105 TCOMP. The genetic correlations of these adaptive traits with heifer growth, scanned carcass, pubertal measures and steer growth and carcass traits were estimated. BRAH recorded significantly (P < 0.05) lower TICK, EPG, FLY and TEMP than did TCOMP. BRAH also had significantly sleeker coats, lighter coat colour, more pendulous navels and more docile temperament than did TCOMP. The heritability of TICK and FLY was low (<20%), that of EPG, TEMP, NAVEL and FT was moderate (20-50%) and that of COAT and COLOUR high (>50%). In general, phenotypic correlations between these adaptive traits were low and genetic correlations were non-significant, implying trait independence. Genetic correlations between EPG and weight traits (0.29 to 0.44) indicated a positive relationship, implying no deleterious effect of worms on the growth at a genetic level, especially in TCOMP. The negative genetic correlations between COAT and body-condition score across genotypes (-0.33 to -0.48) indicated genetic advantage of sleek coats in tropics. A positive genetic correlation between COAT and the age at the firstobserved corpus luteum (0.73) in BRAH indicated that BRAH with sleeker coats were genetically early maturing. Further, sleeker coats were genetically indicative of lower weights and lower fat cover at puberty in BRAH. The scanned fat measures at rump and rib sites for feedlot steers showed strong genetic correlation (0.50-0.58) with heifer TEMP, indicating genetically fatter animals had genetically lower heat tolerance. In BRAH, a positive genetic association between heifer COLOUR and scanned fat measures in steers (0.50-0.54) implied increased fatness in genetically darker animals. Further, in BRAH, a strong negative genetic correlation (-0.97) was observed between steer retail beef yield and heifer TEMP, indicating a favourable genetic association. In general, genetic correlations between adaptive traits and other economic traits were genotype specific. Further, it can be concluded that selection for productive and pubertal traits in tropical beef cattle genotypes would not adversely affect their tropical adaptability.

A genome-wide association study of tick burden and milk composition in cattle

“…The genetic correlation between tick and milk traits was negative with large standard errors, while the heritabilities of these traits were similar to previous estimates. Compared with previous estimates the heritability for tick burden in this study was larger than the value of h 2 = 0.15 found in zebu and zebu composite Brahman and Tropical Composite cattle for tick scores (Prayaga et al 2009), but similar to the value of h 2 = 0.41 AE 0.08 calculated for taurine cattle using multiple tick counts (Henshall 2004) and within the range of h 2 = 0.34-0.49 previously calculated for cattle in Queensland (Wharton et al 1970;Mackinnon et al 1991). Heritabilities for the milk yields were similar to previously estimated values for these traits (Pander et al 1992) but higher than previous estimates restricted to Australian Holstein and Jersey (Visscher and Goddard 1995).…”

“…In cattle, zebu have greater growth rates and performance in the presence of parasites, in hotter climates and fed lower quality feed than taurine animals, but poorer growth rates and performance in the absence of parasites, in cooler climates and fed better quality feed Vercoe 1977, 1984). However, these might represent breed genetic differences because genetic correlations for growth traits and parasite resistance traits are often close to zero when analysed within a breed (Prayaga and Henshall 2005;Prayaga et al 2009).…”

Importance of adaptation and genotype × environment interactions in tropical beef breeding systems

“…They indicated that most adaptive traits were moderately to highly heritable (Table 3). Their results were confirmed in a later, independent experiment undertaken in similar environments to the studies in the earlier review (Prayaga et al, 2009), indicating there is ample opportunity to improve these traits through selection, even though they are difficult to include in genetic evaluation systems because of their difficulty of measurement.…”

Association weight matrix for the genetic dissection of puberty in beef cattle

“…We used data from 866 cows representing 51 sire families from a tropical composite population bred in the tropical northern regions of Australia that was described elsewhere (5,9,(40)(41)(42). In these cows, 22 traits were annotated: AGECL (days), presence or absence of corpus luteum close to the day when bulls were placed in the same paddock as the heifers (CLJOIN, score 1-0), WTCL (kg), scanned P8 site fat depth at AGECL (FATCL, mm), PPAI (days), PPAI with respect to weaning time (PW, score 1-0), live weight (WT, kg), hip height (HH, cm), serum concentration of insulin-like growth factor I (IGF-I, ng/mL), average daily weight gain (ADG, kg/d), body condition score (CS, score 1-10), scanned longissimus dorsi area (SEMA, cm 2 ), scanned P8 site fat depth (SP8, mm) and scanned fat depth measured between the last 2 ribs (SRIB, mm).…”