Inbreeding depression on beef cattle traits: Estimates, linearity of effects and heterogeneity among sire-families

Abstract

-Records from up to 19 054 registered cows and 10 297 calves in 155 herds of the Alentejana cattle breed were used to study the effects of individual (F i ) and maternal (F m ) inbreeding on reproductive, growth and carcass traits, as well as assessing the importance of non-linear associations between inbreeding and performance, and evaluating the differences among sire-families in the effect of F i and F m on calf weight at 7 months of age (W7M). Overall, regression coefficients of performance traits on inbreeding were small, indicating a minor but still detrimental effect of both F i and F m on most traits. The traits with the highest percentage impact of F i were total number of calvings through life and calf weight at 3 months of age (W3M), followed by longevity and number of calves produced up to 7 years, while the highest effect of F m was on W3M. Inbreeding depression on feed efficiency and carcass traits was extremely small and not significant. No evidence was found of a non-linear association between inbreeding and performance for the traits analyzed. Large differences were detected among sire-families in inbreeding depression on W7M, for both F i and F m , encouraging the possibility of incorporating sire effects on inbreeding depression into selection decisions.Alentejana / cattle / inbreeding depression / individual inbreeding / maternal inbreeding

Inbreeding depression on production and reproduction traits of buffaloes from Brazil

“…According to Carolino and Gama (2008), the frequently assumed linear association between inbreeding and performance is compatible with the dominance hypothesis, as it would correspond to the loss of heterozygosity and an increase in the frequency of deleterious recessive homozygotes as inbreeding accumulates. However, if epistatic effects are also involved in inbreeding depression, a non-linear decline in mean performance would result from accumulated inbreeding (Charlesworth & Charlesworth 1999).…”

“…In a review, Burrow (1993) reported decreases of 0.44 kg/1% for weaning weight and 0.69 kg/1% for W365 of calves. According to Carolino and Gama (2008), the high results presented by Burrow (1993) are mostly based on highly inbred lines of cattle, while their data originated from commercial herds subject to mild artificial selection and with moderate rates of inbreeding, thus with lower expected effects of inbreeding depression. At lower levels of inbreeding the linear model provides a reasonable approximation of the phenomenon.…”

Pedigree analysis and inbreeding depression on growth traits in Brazilian Marchigiana and Bonsmara breeds1

“…Santana et al (2010), studying Nellore animals, also found an unfavorable effect of F i on WW. Burrow (1998) and Carolino and Gama (2008) also reported an inbreeding depression of −0.32 to −1.49 kg/1% increase in F i on BW at 12 and 18 mo of age of beef cattle. The estimates of inbreeding depression indicate that the lack of control of inbreeding in the populations will result in economic losses for production systems.…”

Population structure and genetic trends for indigenous African beef cattle breeds in South Africa

“…The application of quantitative breeding methodology and reproductive biotechnology (artificial insemination) has resulted in more intense selection pressure on a number of traits of economic importance that might have contributed to an increase in production efficiency, but in some cases at the expense of genetic diversity. The use of a small number of elite genotypes poses the danger of increasing undesirable recessive genes within a population that may result in inbreeding depression in the long run (Carolino & Gama, 2008;Oltenacu & Broom, 2010). The loss of genetic diversity due to increased inbreeding within cattle breeds has been reported to have negative effects on some production and fitness traits in dairy (Oltenacu & Broom, 2010) and beef cattle breeds (Carolino & Gama 2008;Santana et al, 2010).…”

“…The use of a small number of elite genotypes poses the danger of increasing undesirable recessive genes within a population that may result in inbreeding depression in the long run (Carolino & Gama, 2008;Oltenacu & Broom, 2010). The loss of genetic diversity due to increased inbreeding within cattle breeds has been reported to have negative effects on some production and fitness traits in dairy (Oltenacu & Broom, 2010) and beef cattle breeds (Carolino & Gama 2008;Santana et al, 2010). Maintenance of within-breed genetic diversity is therefore essential in making selection decision for genetic improvement.…”