Pre-weaning Traits Research Articles

Comparison of Two- and Three-Way Rotational Crossing and Synthetic Variety Production Involving Inbred Lines of Hereford Cattle: Preweaning and Weaning Traits

Comparison of Two- and Three-Way Rotational Crossing and Synthetic Variety Production Involving Inbred Lines of Hereford Cattle: Preweaning and Weaning Traits

INFLUENCE OF BODY WEIGHT AND CHANGES IN BODY WEIGHT OF THE COW ON PREWEANING TRAITS OF THE CALF

This study was designed to estimate and evaluate environmental factors affecting birth weight, weaning weight and preweaning average daily gain (ADG) of purebred Shorthorn calves from the control line of a selection experiment. Nine years of data consisted of 635 birth weight and 607 weaning weight records. Least squares analysis of variance revealed that sex of the calf was the most important source of variation: males averages 2.31 kg heavier at birth, were 14.3 kg heavier at weaning and gained 0.08 kg more per day from birth to weaning than females. Heavier cows in June, October, and December prior to parturition and at parturition produced heavier calves at birth. Heavier cows in October prior to parturition, at parturition, and in June or October following parturition produced calves which grew more rapidly from birth to weaning and were heavier at weaning. There was no apparent effect of cow weight changes before or after parturition on preweaning traits. Correlations of birth weight with weaning weight, preweaning ADG and cow weight at parturition were 0.56 ± 0.03, 0.43 ± 0.04 and 0.24 ± 0.04 respectively. Correlations of weaning weight and preweaning average daily gain with cow weights at parturition were 0.42 ± 0.04 and 0.40 ± 0.04. Correlations among cow weights in June, October, and December prior to parturition, at parturition, and in June and October following parturition were estimated.

Estimates of genetic parameters for pre-weaning and post-weaning growth traits of Chios lambs

ABSTRACTData on 792 Chios lambs born during the 1972/73 and 1973/74 lambing seasons were used to estimate genetic and phenotypic parameters for birth weight, weaning weight, age at weaning, pre-weaning daily gain, body weight at 5, 10, 15 and 20 weeks of age, and postweaning daily gain. Body weight at 15 weeks of age had the highest heritability estimate (0·73 ± 0·17) and that of post-weaning daily gain was also high (0·56 ± 0·15). Selection for either weight at 15 weeks or post-weaning daily gain would be expected to yield a greater response than selection for pre-weaning daily gain or weaning weight. Genetic correlations among weights and/or gains were positive (approximately 0·20). Phenotypic correlations among weights and gains were generally higher than genetic correlations. However, the correlation between pre— and post-weaning daily gain was small (0·08). Likewise, post-weaning daily gain had low correlations with all weights before 10 weeks. Age at weaning had moderate negative associations with all weights but a very low positive correlation with post-weaning daily gain.

Lamb growth performance of Iranian fat-tailed Karakul, Mehraban and Naeini breeds of sheep and their crosses with Corriedale and Targhee rams

SUMMARYBirth weights, weaning weights (75 days of age) and pre-weaning average daily gains of 291 lambs and post-weaning average daily gains, feed conversions and market weights of 136 ram lambs were studied. The lambs were of three fat-tailed Iranian breeds of sheep, Karakul, Mehraban and Naeini, and their crosses with Corriedale and Targhee rams.The crossbreds were significantly superior to the purebreds in all the traits studied, by approximately 7% in the pre-weaning traits and up to 18·4% in the post-weaning daily gain. Among the purebreds, Mehraban lambs were superior to the other two breeds in the preweaning traits and final weight.The progeny of the Targhee and Corriedale rams were similar in performance except for feed conversion, in which the lambs sired by Targhee rams were more efficient. Breed of dam had a significant effect on the pre-weaning traits and feed conversion. Mehraban ewes produced lambs with the highest pre-weaning average daily gain and weaning weight among the crossbreds, but they were the least efficient lambs after weaning.Age of dam significantly influenced the pre-weaning but not the post-weaning traits. Lambs born to 4-yr-old ewes were the heaviest and those born to 2-yr-old ewes were the lightest at birth. The lambs reared by 2-yr-old ewes had significantly lower rates of growth and were the lightest at weaning. Sex had a highly significant effect on the pre-weaning traits in favour of the male lambs.

The Importance of Sire × Sex Interactions for Preweaning and Weaning Traits

The Importance of Sire × Sex Interactions for Preweaning and Weaning Traits

Effectiveness of selection for growth rate in Zebu × British crossbred cattle. II.* Post-weaning growth and genetic estimates

The response to one generation of selection for weight per day of age at 18 months (W/Af), in Africander cross (AX) and Brahman cross (BX) cattle, was evaluated in the female offspring of the up and down selected parents. The high W/A< line gained significantly more than the low line over a year from weaning. The advantage of the high W/A line occurred during flush nutritional periods. The realized heritability (h2) of W/Af at 18 months was 0.52, while the estimates of h2 from mid-parental means computed within sires was higher. Heritability estimates for birth weight (Wb), weaning weight per day of age (W/Aw), pre-weaning average daily gain (Gbw) and total average daily gain from birth to final weight (Gt) were all high, while the estimate for post-weaning average daily gain from weaning to final weight (Gpw) was low. The correlated responses of all the traits were high. The genetic correlations estimated from the response and the parent-offspring regressions were all positive and high. Birth weight was the most highly correlated with Gt. All phenotypic correlations were positive but lower than the genetic correlations, the correlation between Gbw and Gpw being the lowest. Environmental correlations between birth weight and pre-weaning traits were essentially zero, and between birth weight and post-weaning traits and Gt, negative. Weight per day of age at 18 months appeared to be the most efficient and practical single trait to select beef cattle for increased growth rate.

Genetic and Maternal Effects on Pre-Weaning Traits in Crosses of High- and Low-Fat Lines of Swine

Genetic and Maternal Effects on Pre-Weaning Traits in Crosses of High- and Low-Fat Lines of Swine

Genetic relationships among milk yield, growth, feed intake and efficiency in laboratory mice.

Fifty-seven paternal half-sib families (including 533 lactating female progeny) were formed over three replicates in order to estimate heritabilities and genetic and phenotypic correlations among milk production, feed intake, body weight gain and the efficiency of feed utilization. Milk production was estimated daily from 6 to 21 days of lactation by isolating the litters (size 8) for 6 hr. daily and weighing the entire litter before and after a 1.5-hr. nursing period. A nested model was used to estimate components of variance and covariance to estimate the heritabilities and genetic correlations. The heritability values for gain in weight ranged from 0.12±.10 to 0.22±.12; for feed intake from 0.14±.11 to 0.34±.13; for feed efficiency from 0.11±.10 to 0.24±.12; and for body weight from 0.05±.09 to 0.33±.13. The heritability estimates for milk yield was 0.17±.11, and for 12-day litter weight it was 0.24±.12. The genetic correlations among the preweaning traits, i.e., gain from 5 to 21 days and 12- and 21-day body weight with milk yield were 1.47±.56, 0.74±.80 and 0.92±.35, respectively. Genetic correlations between milk yield and postweaning body weight and early postweaning gain were also large and positive. Calculated relative efficiencies of correlated responses indicated that either 21- or 42-day body weight would serve as suitable genetic indicators of milk yield in mice. Genetic correlations between milk yield and feed intake and feed efficiency measurements were all considerably lower than those for the body weight traits. Postweaning feed efficiency and feed intake were both positively correlated genetically with early postweaning gain. However, feed efficiency and feed intake were negatively correlated. Phenotypic correlations between milk yield and all other traits measured were small. Therefore, it is unlikely that any one of these traits would serve as a suitable phenotypic predictor of lactational milk yield in the mature animal.

INTERRELATIONS BETWEEN SOME REPRODUCTIVE TRAITS IN SWINE

The associations between 15 preweaning traits in pigs were studied to determine which had the most important effects on litter weights at birth and weaning. The traits were litter size at birth and weaning, number born alive, percentage survival to birth and weaning, pig and litter weights at birth and weaning, daily gain from birth to weaning, gestation length, number of teats, weights of dam at farrowing and at weaning, and the change in dam weight during lactation. Of the 105 correlations, 66 were statistically significant, though many were markedly low. Litter weights at birth and weaning were significantly and relatively highly correlated with most of the other traits, whereas number of teats was correlated only with survival rates at birth and weaning and pig birth weight. The results showed that the importance of litter size was almost twice that of pig weight in determining litter weights at birth and weaning. The results in general indicated that most of the economically important traits related to swine reproductivity are favorably associated.

Effectiveness of reciprocal selection for performance of crosses between Montana no. 1 and Yorkshire swine. I. Preweaning traits.

RESULTS from early studies of individual and family selection for litter size and growth rate within inbred lines of swine (Comstock and Winters, 1944; Laben and Whatley, 1947; Kottman, Lush and Hazel, 1948; Fine and Winters, 1952, 1953; Rempel and Winters, 1952) were far from encouraging when adjusted for accumulated effects of inbreeding (Dickerson, 1951). Also, lack of control populations made it impossible to separate genetic response from environmental trends. The apparent lack of response in spite of intensive selection and substantial estimates of heritability, especially for growth rate, suggested direct progeny test selection for increased heterosis (Comstock, Robinson and Harvey, 1949; Dickerson, 1952) in crosses of specific stocks as a possible method for obtaining further genetic improvement in performance of swine. The objective of the experiment was to determine the effectiveness of selection based upon (1) both pure strain and crossbred progeny performance and that (2) based solely upon pure strain performance. Selection was based on both preweaning and post-weaning performance.