Center for Quantitative Genetics and Genomics, Faculty of Science and Technology, Aarhus University, DK-8830 Tjele, Denmark; SEGES, Agro Food Park 15, 8200 Aarhus N, Denmark.
Center for Quantitative Genetics and Genomics, Faculty of Science and Technology, Aarhus University, DK-8830 Tjele, Denmark; SEGES, Agro Food Park 15, 8200 Aarhus N, Denmark.
J Dairy Sci. 2021 Jan;104(1):678-682. doi: 10.3168/jds.2019-17866. Epub 2020 Nov 6.
During the last decade, the use of systematic crossbreeding in dairy cattle herds has increased in several countries of the world. The aim of this study was to estimate the effect of breed proportion and heterosis on milk production traits and udder health traits in dairy cattle. The study was based on records on milk yield (MY), protein yield (PY), fat yield (FY), somatic cell score (SCS), and mastitis (MAST) from 73,695 first-lactation dairy cows in 130 Danish herds applying systematic crossbreeding programs. Around 45% of the cows were crosses between Danish Holstein (DH), Danish Red (DR), or Danish Jersey (DJ), and the remaining were purebred DH, DR, or DJ. The statistical model included the fixed effects of herd-year, calving month, and calving age and an effect representing the lactation status of the cow. In addition, the model included a regression on calving interval from first to second lactation, a regression on the proportion of DH, DR, and DJ genes, and a regression on the degree of heterozygosity between DH and DR, DH and DJ, and DR and DJ. Random effects were the genetic effect of the cow and a residual. The effect of breed proportions was estimated relatively to DH. For MY, a pure DR yielded 461 kg milk less than DH, whereas a pure DJ yielded 2,259 kg milk less than a pure DH. Compared with DH, PY was 41.7 kg less for DJ, whereas PY for DR was 4.0 kg less than for DH. For FY, a DR yielded 10.6 kg less than DH, whereas there was no significant effect of breed proportion between DJ and DH. A DR cow had lower SCS (0.13) than DH, whereas DJ had higher SCS (0.14) than DH. There was no significant effect of breed proportion on MAST between the 3 breeds. Heterosis was significant in all combinations of breeds for MY, FY, and PY. Heterosis for crosses between DH and DR was 257 kg (3.2%), 11.9 kg (3.2%), and 8.9 kg (3.2%) for MY, PY, and FY, respectively. Corresponding figures for crosses between DH and DJ were 314 kg (4.4%), 14.3 kg (4.4%), and 10.4 kg (4.0%), whereas heterosis between DR and DJ was 462 kg (6.7%), 19.6 kg (6.7%), and 13.9 kg (5.4%) for MY, PY, and FY, respectively. Heterosis was only significant for SCS in the crosses between DH and DR. Heterosis effects for MAST were nonsignificant for all the crosses. The results obtained in this study demonstrate that in first lactation cows, there is a positive effect of heterosis on milk production traits, but limited effect on udder health traits.
在过去的十年中，世界上许多国家的奶牛群中系统杂交的使用有所增加。本研究的目的是估计品种比例和杂种优势对奶牛产奶量和乳房健康性状的影响。该研究基于丹麦 130 个采用系统杂交计划的牛群中 73695 头初产奶牛的产奶量（MY）、蛋白产量（PY）、脂肪产量（FY）、体细胞评分（SCS）和乳腺炎（MAST）记录。约 45%的奶牛是丹麦荷斯坦（DH）、丹麦红牛（DR）或丹麦泽西（DJ）之间的杂交，其余为纯系 DH、DR 或 DJ。统计模型包括 herd-year、产犊月份和产犊年龄的固定效应以及代表奶牛泌乳状态的效应。此外，模型还包括从第一次产奶到第二次产奶的产犊间隔回归、DH、DR 和 DJ 基因比例回归以及 DH 和 DR、DH 和 DJ、DR 和 DJ 之间杂合度的回归。随机效应是奶牛的遗传效应和残余效应。品种比例的影响相对于 DH 进行了估计。对于 MY，纯系 DR 比 DH 少产 461 公斤牛奶，而纯系 DJ 比 DH 少产 2259 公斤牛奶。与 DH 相比，DJ 的 PY 少 41.7 公斤，而 DR 的 PY 比 DH 少 4.0 公斤。对于 FY，DR 比 DH 少产 10.6 公斤，而 DJ 和 DH 之间的品种比例没有显著影响。DR 奶牛的 SCS（0.13）低于 DH，而 DJ 的 SCS（0.14）高于 DH。DH、DR 和 DJ 三种品种之间的 MAST 品种比例没有显著影响。DH 和 DR 之间的杂种优势在 MY、FY 和 PY 的所有组合中均显著。DH 和 DR 之间杂交的杂种优势分别为 257 公斤（3.2%）、11.9 公斤（3.2%）和 8.9 公斤（3.2%）用于 MY、PY 和 FY，DH 和 DJ 之间杂交的相应数字分别为 314 公斤（4.4%）、14.3 公斤（4.4%）和 10.4 公斤（4.0%），而 DR 和 DJ 之间的杂种优势为 462 公斤（6.7%）、19.6 公斤（6.7%）和 13.9 公斤（5.4%），用于 MY、PY 和 FY。DH 和 DR 之间的杂交仅在 SCS 上具有杂种优势效应。DH 和 DR 之间杂交的 MAST 杂种优势效应不显著。本研究的结果表明，在初产奶牛中，杂种优势对产奶量性状有积极影响，但对乳房健康性状影响有限。
