Effect of non-structural carbohydrate dietary content on the productive performance of Sarda primiparous ewes

In order to enhance our knowledge of milk sheep rationing, 30 Sarda primiparous ewes, for which single birth was diagnosed by ultrasonography prior to lambing, were divided into two homogeneous groups (L-NSC and H-NSC) and fed isoproteic diets containing different amounts of non-structural carbohydrates (NSC, 36 vs 40 % DM). The lambs were weighed both at birth (between February and March 2002) and at sale (about one month later) in order to estimate milk produced by their mothers during the lactation period, by using a specific equation developed on Sarda ewes. Individual milk yield and quality were then monitored monthly until the ewes dried off (July 2002). Our results showed that group H-NSC (which received the diet with the highest NSC content) was associated to the highest milk yield (P<0.01) during the suckling period. In contrast, in the milking period group L-NSC showed significantly higher (P<0.05) mean milk yield (996.2 vs 899.8 g/d) and fat and protein corrected milk yield (979.6 vs 877.7 g/d). Dietary treatments did not significantly affect milk composition. In conclusion, considering the milk production of each group as a function of the lactation month, group H-NSC had its best performance during the first two months of lactation, while group L-NSC was more productive during the remaining months. Also the percentage of protein, fat and casein of the milk during milking showed a similar trend. While the latter parameters were higher in the H-NSC group during the first two months of milking, from the 4th control onward higher levels were observed in the L-NSC group. These results suggest, at least for Sarda primiparous ewes, the adoption of diets with different contents of non-structural carbohydrates according to the productive period (40 %, DM basis, in the first two months of lactation, 36 %, DM basis, in subsequent months).