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 ± 3.9 kg) at mid-lactation stage (89 ± 1 DIM). Ewes were divided into
2 groups and fed chopped alfalfa hay at 400 g/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 (2900 g/d vs. 2555 g/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 (1813 ml/d vs. 2110 ml/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.
