The large-scale recording of traits such as feed efficiency and methane emissions for use in genetic improvement programs is complex, costly, and time-consuming. Therefore, heritable traits that can be continuously recorded in dairy herds and are correlated to feed efficiency and methane emission traits could provide useful information for genetic evaluation. Rumination time has been suggested to be associated with feed efficiency, methane production (methane emission in g/day), and production traits at the phenotypic level. Therefore, the objective of this study was to investigate the genetic relationships among rumination time, feed efficiency, methane and production traits using 7,358 records from 656 first lactation Holstein cows. The estimated heritabilities were moderate for rumination time (0.45 ± 0.14), methane production (0.36 ± 0.12), milk yield (0.40 ± 0.08), fat yield (0.29 ± 0.06), protein yield (0.32 ± 0.07), and energy corrected milk (0.28 ± 0.07), while low and non-significant for feed efficiency (0.15 ± 0.07), which was defined as the residual of the multiple linear regression of DMI on ECM and MBW. A favorable negative genetic correlation was estimated between rumination time and methane production (−0.53 ± 0.24), while a positive favorable correlation was estimated between rumination time and energy corrected milk (0.49 ± 0.11). The estimated genetic correlation of rumination time with feed efficiency (−0.01 ± 0.17) was not significantly different from zero but showed a trend of a low correlation with dry matter intake (0.21 ± 0.13, = 0.11). These results indicate that rumination time is genetically associated with methane production and milk production traits, but high standard errors indicate that further analyses should be conducted to verify these findings when more data for rumination time, methane production and feed efficiency become available.

中文翻译：

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第一泌乳荷斯坦奶牛反刍时间、饲料效率和甲烷生产性状遗传参数的估计

用于遗传改良计划的饲料效率和甲烷排放等性状的大规模记录是复杂、昂贵且耗时的。因此，可以在奶牛群中连续记录并与饲料效率和甲烷排放性状相关的遗传性状可以为遗传评估提供有用的信息。反刍时间被认为与饲料效率、甲烷产量（甲烷排放量，以克/天为单位）和表型水平的生产性状有关。因此，本研究的目的是利用 656 头泌乳荷斯坦奶牛的 7,358 条记录来调查反刍时间、饲料效率、甲烷和生产性状之间的遗传关系。反刍时间（0.45±0.14）、甲烷产量（0.36±0.12）、产奶量（0.40±0.08）、脂肪产量（0.29±0.06）、蛋白质产量（0.32±0.07）和能量校正乳的估计遗传力中等(0.28 ± 0.07)，而饲料效率 (0.15 ± 0.07) 较低且不显着，饲料效率被定义为 DMI 对 ECM 和 MBW 的多元线性回归的残差。反刍时间和甲烷产量之间估计存在有利的负遗传相关性（-0.53±0.24），而反刍时间和能量校正牛奶之间估计存在正的有利相关性（0.49±0.11）。反刍时间与饲料效率的估计遗传相关性（−0.01±0.17）与零没有显着差异，但显示出与干物质摄入量相关性较低的趋势（0.21±0.13，= 0.11）。这些结果表明，反刍时间与甲烷产量和产奶性状在遗传上相关，但高标准误差表明，当获得更多关于反刍时间、甲烷产量和饲料效率的数据时，应进行进一步分析以验证这些发现。