De la Torre G, Serradilla J M, Gil Extremera F, Sanz Sampelayo M R
Consejo Superior de Investigaciones Científicas, Estación Experimental del Zaidín, Unidad de Nutrición Animal, Profesor Albareda 1, 18008 Granada, Spain.
J Dairy Sci. 2008 Jun;91(6):2443-8. doi: 10.3168/jds.2007-0278.
A study was carried out with 20 goats of the Malagueña breed, half with a high (HG) and half with a low (LG) genetic capability for alpha(S1)-casein (AS1-CN) synthesis, to determine whether the 2 different genotypes (that cause differences in goat milk composition) are related to differences in nutritional feed utilization. Among the 10 HG goats, 7 had BB and 3 had AB genotypes for AS1-CN, whereas there were 7 EF and 3 FF genotypes in the 10 LG goats. The goats were fed diets differing in crude protein content (13.6 vs. 17.7% dry matter for diets 1 and 2, respectively). For each genotype group, a balance trial was conducted with each of the 2 diets in a 2-period balanced changeover designed with half the animals consuming diet 1 and the other half diet 2, determining individual feed intake and the utilization of N and energy in the diets. Greater voluntary feed intake on a metabolic body weight basis among the HG goats was identified as the first possible cause of their milk production. The HG goats also had a greater level of feed utilization, on a metabolic body weight basis, for N and energy intake. Greater ratios of N balance/ digestible N, milk protein N/digestible N, milk energy/ digestible energy, and milk energy/ME were found for HG goats compared with LG. These effects appear to be dependent on the level of protein in the diet, indicating interactive effects. The greater N and energy utilization of HG versus LG goats may explain the differences in milk composition between the 2 genotype groups.
对20只马拉盖尼亚品种的山羊进行了一项研究，其中一半具有高（HG）和一半具有低（LG）α（S1）-酪蛋白（AS1-CN）合成遗传能力，以确定这两种不同基因型（导致山羊奶成分差异）是否与营养饲料利用差异有关。在10只HG山羊中，7只AS1-CN的基因型为BB，3只为AB，而在10只LG山羊中有7只EF和3只FF基因型。给山羊饲喂粗蛋白含量不同的日粮（日粮1和日粮2的干物质分别为13.6%和17.7%）。对于每个基因型组，在一个两期平衡转换设计中，用两种日粮中的每一种进行平衡试验，一半动物消耗日粮1，另一半消耗日粮2，确定个体采食量以及日粮中氮和能量的利用率。HG山羊以代谢体重为基础的更大的自愿采食量被确定为其产奶量的第一个可能原因。HG山羊以代谢体重为基础，对氮和能量摄入的饲料利用率也更高。与LG山羊相比，HG山羊的氮平衡/可消化氮、乳蛋白氮/可消化氮、乳能量/可消化能量和乳能量/代谢能的比率更高。这些影响似乎取决于日粮中的蛋白质水平，表明存在交互作用。HG山羊比LG山羊对氮和能量的利用率更高，这可能解释了两个基因型组之间羊奶成分的差异。
