Mehtiö T, Mäntysaari P, Negussie E, Leino A-M, Pösö J, Mäntysaari E A, Lidauer M H
Production Systems, Natural Resources Institute Finland (Luke), Tietotie 2, FI-31600Jokioinen, Finland.
Faba Co-op, PO Box 40, FI-01301Vantaa, Finland.
Animal. 2020;14(8):1588-1597. doi: 10.1017/S1751731120000439. Epub 2020 Mar 13.
Inclusion of feed efficiency traits into the dairy cattle breeding programmes will require considering early lactation energy status to avoid deterioration in health and fertility of dairy cows. In this regard, energy status indicator (ESI) traits, for example, blood metabolites or milk fatty acids (FAs), are of interest. These indicators can be predicted from routine milk samples by mid-IR reflectance spectroscopy (MIR). In this study, we estimated genetic variation in ESI traits and their genetic correlation with female fertility in early lactation. The data consisted of 37 424 primiparous Nordic Red Dairy cows with milk test-day records between 8 and 91 days in milk (DIM). Routine test-day milk samples were analysed by MIR using previously developed calibration equations for blood plasma non-esterified FA (NEFA), milk FAs, milk beta-hydroxybutyrate (BHB) and milk acetone concentrations. Six ESI traits were considered and included: plasma NEFA concentration (mmol/l) either predicted by multiple linear regression including DIM, milk fat to protein ratio (FPR) and FAs C10:0, C14:0, C18:1 cis-9, C14:0 * C18:1 cis-9 (NEFAFA) or directly from milk MIR spectra (NEFAMIR), C18:1 cis-9 (g/100 ml milk), FPR, BHB (mmol/l milk) and acetone (mmol/l milk). The interval from calving to first insemination (ICF) was considered as the fertility trait. Data were analysed using linear mixed models. Heritability estimates varied during the first three lactation months from 0.13 to 0.19, 0.10 to 0.17, 0.09 to 0.14, 0.07 to 0.10, 0.13 to 0.17 and 0.13 to 0.18 for NEFAMIR, NEFAFA, C18:1 cis-9, FPR, milk BHB and acetone, respectively. Genetic correlations between all ESI traits and ICF were from 0.18 to 0.40 in the first lactation period (8 to 35 DIM), in general somewhat lower (0.03 to 0.43) in the second period (36 to 63 DIM) and decreased clearly (-0.02 to 0.19) in the third period (64 to 91 DIM). Our results indicate that genetic variation in energy status of cows in early lactation can be determined using MIR-predicted indicators. In addition, the markedly lower genetic correlation between ESI traits and fertility in the third lactation month indicated that energy status should be determined from the first test-day milk samples during the first 2 months of lactation.
将饲料效率性状纳入奶牛育种计划需要考虑早期泌乳能量状态，以避免奶牛健康和繁殖力下降。在这方面，能量状态指标（ESI）性状，例如血液代谢物或乳脂肪酸（FAs），备受关注。这些指标可通过中红外反射光谱法（MIR）从常规乳样中预测得到。在本研究中，我们估计了ESI性状的遗传变异及其与早期泌乳期雌性繁殖力的遗传相关性。数据包括37424头初产北欧红牛奶牛，其有产奶8至91天（DIM）的测奶日记录。使用先前开发的用于血浆非酯化脂肪酸（NEFA）、乳脂肪酸、乳β-羟基丁酸（BHB）和乳丙酮浓度的校准方程，通过MIR对常规测奶日乳样进行分析。考虑并纳入了六个ESI性状：通过包括DIM、乳脂蛋白比（FPR）和脂肪酸C10:0、C14:0、C18:1顺-9、C14:0 * C18:1顺-9（NEFAFA）的多元线性回归预测的血浆NEFA浓度（mmol/l）或直接从乳MIR光谱预测的（NEFAMIR）、C18:1顺-9（g/100 ml乳）、FPR、BHB（mmol/l乳）和丙酮（mmol/l乳）。从产犊到首次输精的间隔时间（ICF）被视为繁殖性状。使用线性混合模型对数据进行分析。在前三个泌乳月中，NEFAMIR、NEFAFA、C18:1顺-9、FPR、乳BHB和丙酮的遗传力估计值分别从0.13至0.19、0.10至0.17、0.09至0.14、0.07至0.10、0.13至0.17和0.13至0.18不等。在第一个泌乳期（8至35 DIM），所有ESI性状与ICF之间的遗传相关性为0.18至0.40，在第二个时期（36至63 DIM）总体略低（0.03至0.43），在第三个时期（64至91 DIM）明显下降（-0.02至0.19）。我们的结果表明，可使用MIR预测指标确定早期泌乳期奶牛能量状态的遗传变异。此外，第三个泌乳月中ESI性状与繁殖力之间明显较低的遗传相关性表明，应在泌乳的前两个月从首次测奶日乳样中确定能量状态。
