Schmidt P I, Campos G S, Roso V M, Souza F R P, Boligon A A
Animal Science Department, Federal University of Pelotas, 96010-900, Pelotas, Brazil.
Animal Science Department, Federal University of Rio Grande do Sul, 90040-060, Porto Alegre, Brazil.
Theriogenology. 2019 Apr 1;128:47-53. doi: 10.1016/j.theriogenology.2019.01.032. Epub 2019 Feb 1.
This study estimated the genetic variability and correlations between growth and reproductive traits in Nelore cattle. Annual genetic changes in female reproductive traits were also evaluated using repeated measures. Direct heritability was moderate for the growth traits and scrotal circumference (0.235 ± 0.015 to 0.443 ± 0.006), indicating genetic variability in these traits in the population studied. Maternal heritability was low for weaning height (0.042 ± 0.012) and weaning weight (0.112 ± 0.013). Regarding female reproductive traits, gestation length (GL) exhibited a slightly higher heritability (0.179 ± 0.006) than days to calving (DC) and calving interval (CI) (0.123 ± 0.006 and 0.105 ± 0.008, respectively). Repeatability was lower for GL (0.222 ± 0.006) compared to DC (0.318 ± 0.004) and CI (0.406 ± 0.006). Moderate and positive genetic correlations were obtained between the growth traits and scrotal circumference, ranging from 0.193 ± 0.019 to 0.519 ± 0.007. Weaning height showed low and positive genetic associations with GL (0.138 ± 0.007) and CI (0.189 ± 0.016), but was not correlated with DC (-0.016 ± 0.011). Similarly, weaning weight, yearling height or yearling weight was not associated with any of the female reproductive traits. The genetic correlations between scrotal circumference and female reproductive traits were negative and favorable, but low: -0.116 ± 0.020 (GL), -0.084 ± 0.028 (DC), and -0.054 ± 0.038 (CI). Favorable genetic associations were estimated between all female reproductive traits, ranging from 0.170 ± 0.040 to 0.442 ± 0.050. Genetic changes were favorable for GL and CI (-0.02 days/year and -0.11 days/year, respectively) and unfavorable for DC (0.16 days/year). In conclusion, selection for higher growth using the estimated breeding values for height and weight will not affect the reproductive performance of Nelore females. Nonetheless, simultaneous selection for growth and reproductive traits is possible.
本研究估计了内洛尔牛生长性状与繁殖性状之间的遗传变异性及相关性。还采用重复测量法评估了雌性繁殖性状的年度遗传变化。生长性状和阴囊周长的直接遗传力中等（0.235±0.015至0.443±0.006），表明在所研究的群体中这些性状存在遗传变异性。断奶高度（0.042±0.012）和断奶体重（0.112±0.013）的母系遗传力较低。关于雌性繁殖性状，妊娠期长度（GL）的遗传力（0.179±0.006）略高于产犊天数（DC）和产犊间隔（CI）（分别为0.123±0.006和0.105±0.008）。与DC（0.318±0.004）和CI（0.406±0.006）相比，GL的重复性较低（0.222±0.006）。生长性状与阴囊周长之间存在中等程度的正遗传相关性，范围为0.193±0.019至0.519±0.007。断奶高度与GL（0.138±0.007）和CI（0.189±0.016）呈低正遗传关联，但与DC不相关（-0.016±0.011）。同样，断奶体重、周岁高度或周岁体重与任何雌性繁殖性状均无关联。阴囊周长与雌性繁殖性状之间的遗传相关性为负且有利，但较低：与GL为-0.116±0.020，与DC为-0.084±0.028，与CI为-0.054±0.038。所有雌性繁殖性状之间估计存在有利的遗传关联，范围为0.170±0.040至0.442±0.050。GL和CI的遗传变化是有利的（分别为-0.02天/年和-0.11天/年），而DC的遗传变化是不利的（0.16天/年）。总之，利用身高和体重的估计育种值选择更高的生长速度不会影响内洛尔母牛的繁殖性能。尽管如此，同时选择生长性状和繁殖性状是可行的。
