Decreasing dietary NFC concentration during mid-lactation of dairy ewes: Does it result in higher milk production?

Abstract

The effect of the level of dietary non-fiber carbohydrates (NFC) on intake, in vivo digestibility, milk production and endocrine-metabolic status was studied in 20 Sarda ewes (mean±SE, BW 42.5±3.9kg) at mid-lactation stage (89±1 DIM). Ewes were divided into 2 groups and fed chopped alfalfa hay at 400g/d and pelleted concentrates ad libitum in metabolic cages during 3 weeks. The concentrates differed in NFC concentration (NFC=36% of DM: group NFC36; NFC=23% of DM: group NFC23), due to the substitution of cereal grains with soybean hulls in the low NFC diet. Dry matter intake was higher for NFC23 than for NFC36 (2900g/d vs. 2555g/d; P<0.01). Dry matter digestibility was higher in NFC36 than in NFC23 (68.4% vs. 62.9%, P<0.001), while the contrary occurred for NDF digestibility (52.9% vs. 56.1%, P<0.015). Energy intake did not differ between groups (P>0.2). Dietary NFC concentration negatively affected milk yield (1813ml/d vs. 2110ml/d, for NFC36 and NFC23 groups, respectively, P<0.001) and positively affected milk protein concentration (4.68% vs. 4.51%, P<0.05, respectively), whereas milk fat concentration was similar between groups (5.06% vs. 5.19%, P>0.2). Body fat increased (P<0.05) without treatment-associated differences. Higher glucose (P<0.05) and lower urea concentrations (P<0.001) were found in blood plasma of NFC36 ewes compared to NFC23 ewes. Insulin concentration in blood plasma was higher in NFC23 than in NFC36 (P<0.01), whereas GH levels were similar between groups. In conclusion, the low dietary NFC concentrate based on soybean hulls exerted positive effects on intake and milk yield in mid-lactating ewes, probably due to a higher proportion of the ingested energy being devoted to milk secretion.