Influence of the mountain pasture on the chemical composition and nitrogen fractions of the sheep milk.Original Title Influenza del pascolo in alpeggio sulla composizione chimica e sulla ripartizione delle frazioni azotate del latte di pecora.

摘要

The quality of the milk plays a very important role in all dairy productions for the effects on cheese yield and quality. The aim of this research was to make a comparison of the milk quality of sheep reared in different environmental conditions: mountain pasture (GT) and plain pasture (GS). The research was carried out in 6 herds. Three of them moved to the mountain pasture during summer months (GT) while 3 have always been located in the plain (GS). The following milk samples were collected: one per herd in the period before the mountain pasture (both GT and GS were in the plain); two per herd in the period of mountain pasture (GT was in the mountain and GS was in the plain); one per herd after the mountain pasture (both GT and GS were in the plain again). On every milk sample the following parameters were determined: crude protein, crude wheyprotein, casein, casein number, NPNx6.38, true protein, non-coagulable protein, paracasein, lactose, fat, somatic cells, dry matter and ash. The values were submitted to statistical analysis with ANOVA univariate, with the type of breeding (GS vs GT) and the breeding (1,...6) as fixed factor; the significance of the differences was tested by means of Least Significant Difference control. No significant (P>0.05) variation of milk parameters was observed between GT and GS, before and after the mountain pasture. On the other hand, the milk produced by GT group in the mountain pasture, was characterised by a higher content of crude protein (6.91 vs 4.65 g/100 g; P<=0.05), casein (5.34 vs 3.61 g/100 g; P<=0.01), crude wheyprotein (1.56 vs 1.04 g/100 g; P<=0.05), true protein (6.63 vs 4.42 g/100 g; P<=0.01), non-coagulable protein (2.13 vs 1.50 g/100 g; P<=0.05) and paracasein (4.77 vs 3.15 g/100 g; P<=0.05) than GS group milk. The milk of GT group was characterized by a higher content of crude protein (+2.26 g/100 g), casein (+1.73 g/100 g) and paracasein (+1.62 g/100 g).