Evaluation of beef cattle genotypes and estimation of direct and maternal genetic effects in a tropical environment. 2. Adaptive and temperament traits

Abstract

Data from a crossbreeding experiment conducted during 1992-97 involving 31 genotypes from tropically adapted British (B), Sanga-derived (S), Zebu cross (Zx), Zebu (Z), and Continental (C) beef cattle breed groups on adaptive traits such as mean tick counts (TICK), mean worm egg counts (EPG), mean rectal temperatures (TEMP), and mean coat scores (COAT), and the temperament trait mean flight time (FT) were analysed. The genotypes were grouped as Bos taurus (B, S, C)-and Bos indicus (Z, Zx)-derived to enable the comparison of direct (dD) and maternal (mD) dominance effects among indicine (II), taurine × indicine (TI), and taurine (TT) crosses. British breed group in this study consisted of Belmont Adaptaur, which is a tropically adapted selected line for tick resistance and 550-day liveweight and hence does not represent temperate British breeds. Coefficients of variation ranged between 15.1 and 55.4% and repeatability estimates varied between 0.26 and 0.45 in various adaptive and temperament traits. Significant (P < 0.01) genotype differences with better performance of Zebu and its crosses over taurine crosses were noticed in all the adaptive traits. Although genotype differences were significant for FT, no clear trend was noticed. Direct additive components of Z and Zx expressed as a deviation from the British mean were significant and negative (favourable) for all the adaptive traits, except for EPG in Zx, indicating better adaptability of Zebu and its crosses relative to the British. Unfavourable additive effect for EPG in the Sanga-derived breed group and undesirable additive effect for TICK and COAT in Continental breeds relative to the British were observed. All the adaptive traits benefited by crossing as demonstrated by significant and favourable dD effects in TI and TT crosses. Heterosis estimates were significant and favourable for all the adaptive traits in Z and B crosses. Treatment to control ticks and worms resulted in significantly increased liveweight gains (LWG) in a majority of genotypes, highlighting the negative effect of parasite burdens. As the Bos indicus proportion in the genotypes increased, the responses from treatment were reduced. The additive effect of Z in the treated group was only half that of the control group, relative to the British breed mean, indicating the advantage of Zebu in the presence of parasites. Low and insignificant phenotypic correlations among TICK, EPG, and LWG were observed. A significant positive correlation between TEMP and COAT and a negative correlation between TEMP and LWG were observed in the British purebreds.A R 0 3 0 7 2 K . C . P r a y a g a E v a l u a t i o n o f c a t t l e g e n o t y p e s . 2 .

Heritability of resistance to bacterial infection in meat rabbits

“…Significant heterosis effects have been reported for disease traits in beef cattle where Bos indicus and Bos taurus cattle were crossed (tick and worm resistance, Prayaga, 2003). The general lack of influence of heterosis on disease incidence in this study may be due to less genetic isolation between the breeds of rabbits or simply because there is no consistent heterosis effect for this trait.…”

“…After an initial evaluation of the three main meat breeds (Prayaga andEady, 2002, 2003) in Australia (New Zealand White, Californian and Flemish Giant) a selection program began in July 2001. A composite strain of rabbits was established and selection of breeding stock has been based on an index of economic return combining estimated breeding values for litter size at weaning and average daily live weight gain from weeks 5 to 10 of age.…”

Genetic selection for temperament traits in dairy and beef cattle

“…For example, Fell et al ( 1999 ) found that calm animals are less likely to be hospitalized in feedlots than excitable animals, and Reinhardt et al ( 2009 ) showed that mortality rates were higher in excitable than calm steers. However, Burrow ( 2001 ), Prayaga ( 2003 ), and Prayaga and Henshall ( 2005 ) did not find significant relationships between temperament and counts of ticks or flies and fecal egg counts. Reinhardt et al ( 2009 ) did not find any effect of temperament on number of respiratory treatments required or on incidence of lung lesions at slaughter.…”

Interação genótipo-ambiente em bovinos de corte compostos

“…Diante de todas essas questões, diversos trabalhos têm sido realizados principalmente no Clay Center (EUA) e também na Austrália (Tropical Beef Cattle) a fim de avaliar o potencial de cruzamentos e formação de bovinos compostos (GREGORY; CUNDIFF; , PRAYAGA, 2003.…”