Goat polymorphism at αs1-casein loci (CSN1S1) influences milkyield and composition. Milk of goats with strong alleles associatedto high αs1-casein shows higher fat and casein, longer coagulationtime, firmer curds and variation in fatty acids than milkfrom goats with weak alleles linked to low αs1-casein. Sincethese milk properties are also affected by nutrition, the aim ofthis study was to investigate the impact of nutritional level onmilk production traits of Girgentana goats with different CSN1S1genotype. From a group of goats genotyped using PRC protocolsat DNA level, 12 goats having the same genotype at αs2, β and κ-casein loci and differing for CSN1S1 genotype were selected: 6were homozygous for strong alleles (AA) and 6 heterozygous ofstrong and weak alleles (AF). Within each genotype, goats weredivided into 3 sub-groups based on days of milk (50 or 120 d),housed individually and fed ad libitum with 3 diets in a 3x3 Latinsquare design with periods of 21 d (14 d for adaptation, 7 d formeasuring and sampling). The diets with different nutritionallevels were as follows: fresh sulla (Hedysarum coronarium L.)(FS); fresh sulla and 800 g/d of barley (FB); sulla hay and 800 g/dof barley (HB). The milk yield increased passing from FS to HBand FB (1352, 1423, 1664 g/d; P<0.01). The effect of genotype onmilk yield was linked to the nutritional level, since the milk fromFB was higher by 350 g/d in AA and 200 g/d in AF goats. In bothgenotypes, barley supplement reduced milk fat (3.6, 3.2, 3.0% inFS, FB, HB; P<0.01) and urea (35, 32, 31 mg/dL in FS, FB, HB;P<0.01), and fresh sulla increased casein content (2.7, 2.7, 2.6%in FS, FB, HB; P<0.01). The AA genotype did not increase thecasein percentage, but AA milk showed longer coagulation time(r: 16 vs 13 min; P<0.01) and higher curd firmness (a30: 35 vs 29mm; P<0.01) than AF milk. In this study, CSN1S1 genotypeshowed to interact with nutritional level only for milk yield.
|Number of pages||1|
|Publication status||Published - 2011|