retrospective data from sebele dairy farm were analysed for reproductive performance of friesian/holstein cows. three hundred records from 1989 to 1995 were used. the herd was zero grazed and the data was analysed for age at first calving (afc), calf birth weights (bw), calving interval (ci), days open (do), calving rate (cr), reproductive wastage (rw) and calving difficulty (cd); dystocia, aft...

There is limited genetic information relating calving difficulty and body weights to other productive and reproductive traits. Such information is useful for specifying selection criteria and for predicting economic consequences of selection. Genetic, maternal, and environmental covariances of six productive and reproductive measurements with calving difficulty, birth weight, 200-d weight, and ...

Records of 547, 2-yr-old heifers of three breed groups were used to evaluate the relative influence of dam's body and pelvic measurements, calf birth weight, sire birth weight and some relative measures (ratios) of calf birth weight and dam weight at calving on calving difficulty. The data were analyzed by regression and least squares procedures. The full model explained 32.5% of the variation ...

The objective of this study was to estimate genetic correlations between calving difficulty score and carcass traits in Charolais and Hereford cattle, treating first and later parity calvings as different traits. Genetic correlations between birth weight and carcass traits were also estimated. Field data on 59,182 Charolais and 27,051 Hereford calvings, and carcass traits of 5,260 Charolais and...

Heritability of 2-yr-old heifer calving difficulty score was estimated in nine purebred and three composite populations with a total of 5,986 calving difficulty scores from 520 sires and 388 maternal grandsires. Estimates were 0.43 for direct (calf) genetic effects and 0.23 for maternal (heifer) genetic effects. The correlation between direct and maternal effects was -0.26. Direct effects were ...

Lifetime productivity of young (2 to 6-yr-old) crossbred cows containing various proportions (0, 1/4, or 1/2) of Braham breeding was evaluated using 188 spring-calving and 154 fall-calving cows. Cows were mated to Limousin sires to produce 1983 through 1986 calf crops. The 1987 calf crops were produced using Limousin and Salers sires. Significant (P less than .10) genotype (crossbred cow group)...

Weight gain of young dairy replacement heifers, even over several months, is highly variable, lowly heritable, and a poor indicator of either weight at calving or first lactation milk yield. Voluntary forage consumption is much less variable, more heritable, and a better predictor of weight at calving and milk yield. Weight at calving is highly heritable but not correlated genetically with milk...

Effects of selection for 2-yr-old heifer calving ease (reduced calving difficulty score) on phenotypic differences between select and control lines of cattle for birth, growth, yearling hip height, and pelvic measurements were estimated. The selection objective was to decrease calving difficulty score in 2-yr-old heifers, while either maintaining or increasing yearling weight. The control line ...

Characters related to production and reproduction were observed on 744 straightbred and F2 calves and their dams produced in a five-breed diallel with Angus, Brahman, Hereford, Holstein and Jersey breeds. These data were analyzed to estimate the effects of these characters on the relationship between weaning weight and calving interval. The model used for analysis of postpartum conception and c...

Fertility and reproductive performance of Landim and Africander females were compared using data collected from 1968 to 1981 at the Chobela Research Station in Mozambique. Breeds were managed together and grouped by age and sex, except when separated for breeding. Traits were relative fertility (probability of fertile females calving from the first breeding season), age at first calving, first ...