title: Nutritional utilization in Malagueña dairy goats differing in genotypes for the content of alphaS1-casein in milk.
abstract: 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.
authors.affiliation: Consejo Superior de Investigaciones Científicas, Estación Experimental del Zaidín, Unidad de Nutrición Animal, Profesor Albareda 1, 18008 Granada, Spain.
authors.forename: G
authors.initials: G
authors.lastname: De la Torre
authors.forename: J M
authors.initials: JM
authors.lastname: Serradilla
authors.forename: F
authors.initials: F
authors.lastname: Gil Extremera
authors.forename: M R
authors.initials: MR
authors.lastname: Sanz Sampelayo
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena / Q000502:physiology*; D000818:Animals; D002364:Caseins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D018592:Cross-Over Studies; D004044:Dietary Proteins / Q000008:administration & dosage; D002149:Energy Intake / Q000502:physiology; D005260:Female; D005838:Genotype; D006041:Goats / Q000235:genetics* / Q000502:physiology; D007774:Lactation / Q000378:metabolism*; D008892:Milk / Q000737:chemistry*; D011897:Random Allocation
chemical_list: D002364:Caseins; D004044:Dietary Proteins