Number of calves born, number of calves weaned, and cumulative weaning weight as measures of lifetime production for Hereford cows1

Abstract

Genetic parameters for lifetime production for cows with the opportunity to produce from 2 through 7 yr of age, as measured by the number of calves born (NB2, …, NB7), the number of calves weaned (NW2, …, NW7), and cumulative weaning weight (CW2, …, CW7), were estimated using data from 3,064 Hereford cows from a selection experiment with a control line (CTL) and three lines selected for weaning weight (WWL), yearling weight (YWL), and an index of yearling weight and muscle score (IXL). Weaning weights were adjusted to 200 d of age and for sex and age of dam. Estimates of heritability and genetic and environmental correlations were obtained by restricted maximum likelihood with bivariate animal models, with year of birth of the cow as a fixed effect and direct genetic and residual as random effects. Genetic trends were estimated by regressing means of estimated breeding values by year of birth and line on birth year. Estimates of heritability (SE) for opportunity groups of 2 to 7 yr of age ranged from 0.08 (0.03) to 0.16 (0.05) for NB; from 0.05 (0.02) to 0.16 (0.05) for NW; and from 0.06 (0.02) to 0.16 (0.05) for CW. Estimates of genetic correlations (SE) among NB traits ranged from 0.60

Genetic variation in meat production related traits in reindeer (Rangifer t. tarandus)

“…More data, like few thousand animals (cf. Kruuk et al, 2000;Martinez et al, 2004a;2004b), could have improved the power of the analyses, but using incomplete cohorts would have led to biased heritability estimates (Tanida et al, 1988;Martinez et al, 2004b). Modelling the incomplete cohorts by treating them as censored data (e.g.…”

“…Quality of dam a ects productivity via her reproduction rate, maternal care and survival (Tanida et al, 1988;Brommer et al, 2002;Martinez et al, 2004a;2004b). Herders expect the dams to have a calf at foot in every autumn round-up (Muuttoranta & Mäki-Tanila, 2011).…”

“…Herders expect the dams to have a calf at foot in every autumn round-up (Muuttoranta & Mäki-Tanila, 2011). e good dams should have a long productive life which facilitates less need of recruitment animals, and hence a higher annual proportion for culling or meat production (Tanida et al, 1988;Martinez et al, 2004a).…”

“…In beef cattle the lifetime production is measured for example by the cumulative weaning weight of calves of beef dams at the age of 7 years. Heritabilities are reported to range from 0.06 to 0.18 (Martinez et al, 2004a;2004b). Lifetime number of o spring weaned has been reported to have h 2 varying from 0.05 to 0.21 (in beef: Tanida et al, 1988;Martinez et al, 2004a;2004b;in sheep: Safari et al, 2005).…”

“…Heritabilities are reported to range from 0.06 to 0.18 (Martinez et al, 2004a;2004b). Lifetime number of o spring weaned has been reported to have h 2 varying from 0.05 to 0.21 (in beef: Tanida et al, 1988;Martinez et al, 2004a;2004b;in sheep: Safari et al, 2005). Dam quality, measured as number and weight of weaned o spring, can be assessed towards the end of her productive life only.…”