The Australian prime lamb industry is seeking to improve lean meat yield (LMY) as a means to increasing efficiency and profitability across the whole value chain. The LMY of prime lambs is affected by genetics and on-farm nutrition from birth to slaughter and is the total muscle weight relative to the total carcass weight. Under the production conditions of south eastern Australia, many ewe flocks experience a moderate reduction in nutrition in mid to late pregnancy due to a decrease in pasture availability and quality. Correcting nutritional deficits throughout gestation requires the feeding of supplements. This enables the pregnant ewe to meet condition score (CS) targets at lambing. However, limited resources on farm often mean it is difficult to effectively manage nutritional supplementation of the pregnant ewe flock. The impact of reduced ewe nutrition in mid to late pregnancy on the body composition of finishing lambs and subsequent carcass composition remains unknown. This study investigated the effect of moderately reducing ewe nutrition in mid to late gestation on the body composition of finishing lambs and carcass composition at slaughter on a commercial scale. Multiple born lambs to CS2.5 target ewes were lighter at birth and weaning, had lower feedlot entry and exit weights with lower pre-slaughter and carcass weights compared with CS3.0 and CS3.5 target ewes. These lambs also had significantly lower eye muscle and fat depth when measured by ultrasound prior to slaughter and carcass subcutaneous fat depth measured 110 mm from the spine along the 12th rib (GR 12th) and at the C-site (C-fat). Although carcasses were ~5% lighter, results showed that male progeny born to ewes with reduced nutrition from day 50 gestation to a target CS2.5 at lambing had a higher percentage of lean tissue mass as measured by dual energy X-ray absorptiometry and a lower percentage of fat during finishing and at slaughter, with the multiple born progeny from CS3.0 and CS3.5 target ewes being similar. These data suggest lambs produced from multiple bearing ewes that have had a moderate reduction in nutrition during pregnancy are less mature. This effect was also independent of lamb finishing system. The 5% reduction in carcass weight observed in this study would have commercially relevant consequences for prime lamb producers, despite a small gain in LMY.

中文翻译：

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在妊娠中期至后期降低双生母羊的营养水平可在宰杀时产生较瘦的初生羔羊。

澳大利亚优质羔羊产业正在寻求提高瘦肉产量（LMY），以此作为提高整个价值链效率和盈利能力的一种手段。从出生到宰杀，初生羔羊的LMY受遗传和农场营养的影响，是相对于car体总重量的总肌肉重量。在澳大利亚东南部的生产条件下，由于牧场供应和质量下降，许多母羊羊群的妊娠中期至晚期营养水平有所下降。要在整个妊娠期纠正营养不足，就需要补充营养。这使怀孕的母羊在产羔时达到条件评分（CS）的目标。然而，农场资源有限通常意味着很难有效管理妊娠母羊群的营养补充。妊娠中期至晚期母羊营养减少对肥育羔羊的身体成分和随后的cas体成分的影响仍然未知。这项研究以商业规模研究了在妊娠中期至后期适度减少母羊营养对肥育羔羊的身体成分和car体成分的影响。与CS3.0和CS3.5目标母羊相比，多头出生到CS2.5目标母羊的羔羊在出生和断奶时体重较轻，育肥场出入口体重较低，而屠宰前和car体重量较低。当在屠宰和car体皮下脂肪深度从脊柱沿第十二肋骨（GR 12）和C部位（C脂肪）测量110毫米之前，通过超声波测量时，这些羔羊的眼部肌肉和脂肪深度也明显降低。尽管car体重量减轻了5％，结果表明，从双胎X射线吸收法测定，从妊娠50天到产后目标降低CS2.5的母羊所生的营养减少的羊具有较高的瘦组织质量百分比，而在精加工和结实时脂肪含量较低。屠宰，CS3.0和CS3.5目标母羊的多胎后代相似。这些数据表明，由多头母羊生产的羔羊在怀孕期间营养水平有所降低，但它们的成熟度较低。这种效果也与羔羊精加工系统无关。尽管LMY的增加很小，但这项研究中观察到的car体重量减少5％对优质羔羊生产者具有商业意义。通过双能X射线吸收测定法测得的羔羊中5的瘦肉组织质量百分比较高，而在精加工和屠宰时的脂肪含量较低，CS3.0和CS3.5目标母羊的多胎后代相似。这些数据表明，由多头母羊生产的羔羊在怀孕期间营养水平有所降低，但它们的成熟度较低。这种效果也与羔羊精加工系统无关。尽管LMY的增加很小，但这项研究中观察到的car体重量减少5％对优质羔羊生产者具有商业意义。通过双能X射线吸收测定法测得的羔羊中5的瘦肉组织质量百分比较高，而在精加工和屠宰时的脂肪含量较低，CS3.0和CS3.5目标母羊的多胎后代相似。这些数据表明，由多头母羊生产的羔羊在怀孕期间营养水平有所降低，但它们的成熟度较低。这种效果也与羔羊精加工系统无关。尽管LMY的增加很小，但这项研究中观察到的car体重量减少5％对优质羔羊生产者具有商业意义。这些数据表明，由多头母羊生产的羔羊在怀孕期间营养水平有所降低，但它们的成熟度较低。这种效果也与羔羊精加工系统无关。尽管LMY的增加很小，但这项研究中观察到的car体重量减少5％对优质羔羊生产者具有商业意义。这些数据表明，由多头母羊生产的羔羊在怀孕期间营养水平有所降低，但它们的成熟度较低。这种效果也与羔羊精加工系统无关。尽管LMY的增加很小，但这项研究中观察到的car体重量减少5％对优质羔羊生产者具有商业意义。