The aim of this study was to investigate the impact of ewe genetic merit on ewe performance and efficiency parameters. The study consisted of three genetic merit groups (New Zealand [NZ], High Irish, and Low Irish) and ran from 2016 to 2019, inclusive. Each genetic merit group contained 30 purebred Suffolk and 30 purebred Texel ewes, which were selected based on their maternal genetic indexes in their country of origin, namely Ireland (€uro-star Replacement index) or New Zealand (New Zealand Maternal worth). Ewe body condition score (BCS), ewe body weight (BW), milk yield, milk composition, dry matter intake (DMI), and efficiency parameters were all analyzed using linear mixed models. Ewe BW was similar across all genetic merit groups at each time point (P > 0.05). In comparison to both High and Low Irish ewes, NZ ewes had a higher BCS at mating, mid-pregnancy, lambing, week 10 post-lambing (PL, P < 0.05). Ewe BW change was similar across genetic merit groups, except between mating and mid-pregnancy where ewe BW loss was greater for NZ ewes than Irish ewes (P < 0.05) and between weeks 6 PL and 10 PL, where NZ ewes gained BW and High and Low Irish ewes lost BW (P < 0.01). Ewe milk yield, milk fat, total solids, and gross energy content were superior for milk produced by NZ ewes at week 6 PL in comparison to milk produced by High Irish and Low Irish ewes (P < 0.01). NZ ewes produced a greater quantity of milk solids/kg of BW at week 6 PL compared with High Irish ewes (P < 0.01), whereas Low Irish ewes did not differ from either NZ or High Irish (P > 0.05). Low Irish ewes had a greater daily DMI than High Irish ewes in late lactation (week 10 PL, P < 0.05) and had a greater DMI/kg of ewe BW compared with the High Irish ewes at the same time point (P < 0.05). NZ ewes weaned a litter BW equivalent to 60.4% of their mating BW, which was more than the Low Irish ewes who weaned 57.1% of the ewe’s BW at mating (P < 0.01), whereas the High Irish ewes did not differ from either the NZ or Low Irish ewes at 59.3% of the ewe’s BW at mating (P > 0.05). This study presents a range of parameters across ewes of high and low genetic merit, demonstrating the ability to achieve gains through selection of animals of high genetic merit. Sheep producers should consider genetic indexes as a tool to assist in the decision-making process of selecting replacement ewes and/or breeding rams, once satisfied the animal is correct, and meeting the breeding objectives of the system.

中文翻译：

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遗传价值对母羊性能和效率参数的影响

本研究的目的是调查母羊遗传价值对母羊生产性能和效率参数的影响。该研究由三个遗传价值组（新西兰 [NZ]、高爱尔兰和低爱尔兰）组成，从 2016 年到 2019 年进行，包括在内。每个遗传价值组包含 30 只纯种 Suffolk 和 30 只纯种 Texel 母羊，这些母羊是根据其原产国的母体遗传指数选择的，即爱尔兰（€uro-star Replacement index）或新西兰（新西兰母体价值）。母羊身体状况评分（BCS）、母羊体重（BW）、产奶量、乳成分、干物质摄入量（DMI）和效率参数均使用线性混合模型进行分析。在每个时间点，所有遗传价值组的母羊体重都相似（P > 0.05）。与高和低爱尔兰母羊相比，新西兰母羊在交配、妊娠中期、产羔、产羔后第 10 周的 BCS 较高（PL，P < 0.05）。母羊体重变化在遗传价值组之间相似，除了在交配和怀孕中期之间，新西兰母羊的母羊体重损失大于爱尔兰母羊（P < 0.05），以及在产后第 6 周和产后 10 周之间，新西兰母羊体重增加和高和低爱尔兰母羊体重下降（P < 0.01）。与高爱尔兰和低爱尔兰母羊生产的牛奶相比，新西兰母羊在产后第 6 周生产的牛奶的母羊产奶量、乳脂、总固体和总能量含量均优于高爱尔兰和低爱尔兰母羊（P < 0.01）。与高爱尔兰母羊相比，新西兰母羊在产后第 6 周生产的乳固体/kg BW 的乳固体量更高（P < 0.01），而低爱尔兰母羊与新西兰或高爱尔兰母羊没有差异（P > 0.05）。在泌乳后期（产仔 10 周，P < 0.05），低爱尔兰母羊的每日 DMI 高于高爱尔兰母羊，并且与同一时间点的高爱尔兰母羊相比，其 DMI/kg 母羊体重更高（P < 0.05）。 0.05)。新西兰母羊断奶一窝体重相当于交配体重的 60.4%，高于交配时断奶 57.1% 的低爱尔兰母羊（P < 0.01），而高爱尔兰母羊与这两者没有差异新西兰或低爱尔兰母羊交配时​​母羊体重的 59.3% (P > 0.05)。这项研究提出了一系列高遗传价值和低遗传价值的母羊的参数，证明了通过选择高遗传价值的动物来获得收益的能力。绵羊生产者应考虑将遗传指数作为一种工具，以协助选择替代母羊和/或繁殖公羊的决策过程，