Ferrari V, Visentin G, van Kaam J B C H M, Penasa M, Marusi M, Finocchiaro R, Cassandro M
Associazione Nazionale Allevatori della Razza Frisona, Bruna e Jersey Italiana, Via Bergamo 292, 26100, Cremona (CR), Italy.
Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova, Viale dell'Università 16, 35020, Legnaro (PD), Italy.
JDS Commun. 2022 Nov 18;4(1):35-39. doi: 10.3168/jdsc.2022-0270. eCollection 2023 Jan.
Excellent fertility performance is important to maximize farmers' profit and to reduce the number of culled animals. Although female fertility of adult cows has been included in Italian Holstein breeding objectives since 2009, little has been done to quantify genetic variation of heifer fertility characteristics so far. The aim of the present study was to estimate genetic parameters of 4 fertility traits in nulliparous Italian Holstein heifers and to develop an aggregate selection index to improve heifer fertility. Data were retrieved from the national fertility database and included information on insemination, calving, and pregnancy diagnosis dates. The investigated phenotypes (mean ± standard deviation) were age at first insemination (AFI, mo; 17.25 ± 2.89), nonreturn rate at 56 d from the first insemination (NRR56, binary; 0.78 ± 0.41), conception rate at first insemination (CR, binary; 0.61 ± 0.49), and interval from first to last insemination (IFL, d; 26.09 ± 51.85). Genetic parameters were estimated using a 4-trait animal model that included the following fixed effects: herd-year of birth and month of birth for AFI, and herd-year-season of birth and month-year of insemination for IFL, NRR56, and CR; the animal additive genetic effect (fitted to the pedigree-based relationship matrix) was considered as a random term. An aggregate index was developed from the estimated additive genetic (co)variance matrix by considering CR as the breeding goal and AFI, NRR56, and IFL as selection criteria. Heritability estimates from average covariance matrices ranged from 0.012 (CR) to 0.015 (IFL), with the exception of AFI (0.071). Conception rate at first insemination was strongly correlated with both IFL (-0.730) and NRR56 (0.668), and weakly to AFI (-0.065), and the relative emphasis placed on each selection criteria in the aggregate index was 10%, 47%, and 43% for AFI, IFL, and NRR56, respectively. The results of the present study suggest that heifer fertility should be considered as an additional trait in the breeding objectives of Italian Holstein.
优异的繁殖性能对于最大化农民利润以及减少淘汰动物数量至关重要。尽管自2009年以来，成年母牛的繁殖力已被纳入意大利荷斯坦牛的育种目标，但迄今为止，在量化后备母牛繁殖特征的遗传变异方面几乎没有做什么工作。本研究的目的是估计意大利荷斯坦未产母牛4个繁殖性状的遗传参数，并制定一个综合选择指数以提高后备母牛的繁殖力。数据从国家繁殖数据库中检索，包括授精、产犊和妊娠诊断日期的信息。所研究的表型（平均值±标准差）为首次授精年龄（AFI，月；17.25±2.89）、首次授精后56天的返情率（NRR56，二元；0.78±0.41）、首次授精的受胎率（CR，二元；0.61±0.49）以及首次授精到最后一次授精的间隔时间（IFL，天；26.09±51.85）。使用一个4性状动物模型估计遗传参数，该模型包括以下固定效应：AFI的出生年份-牛群和出生月份，以及IFL、NRR56和CR的出生年份-季节-牛群和授精月份-年份；动物加性遗传效应（拟合到基于系谱的亲缘关系矩阵）被视为随机项。通过将CR作为育种目标，AFI、NRR56和IFL作为选择标准，从估计的加性遗传（协）方差矩阵中开发了一个综合指数。平均协方差矩阵的遗传力估计值范围从0.012（CR）到0.015（IFL），AFI除外（0.071）。首次授精的受胎率与IFL（-0.730）和NRR56（0.668）都强烈相关，与AFI弱相关（-0.065），并且在综合指数中对每个选择标准的相对权重分别为AFI的10%、IFL的47%和NRR56 的43%。本研究结果表明，后备母牛的繁殖力应被视为意大利荷斯坦牛育种目标中的一个额外性状。
