Effects of fibrolytic enzymes and soybean oil on dairy sheep performance and nutrient digestibility
Résumé
Two experiments were conducted with the aim of studying the effects of a fibrolytic enzyme complex (
E) and soybean oil (SBO) on lactational performance and digestibility in dairy sheep. In Exp. 1, 24 Lacaune (LC) and 24 Manchega (MN) ewes (49 DIM) were blocked in 4 pens of 6 ewes per breed,
and used in a replicated 4 × 4 Latin square for periods of 20 d. Dietary treatments were: 1) C (control); 2) SBO (2.8% of TMR on DM basis); 3) E (Promote, 2 ml/kg TMR on DM basis); and, 4) SBO plus E. Total mixed rations consisted of 60% forage (alfalfa and fescue dehydrated mixture, 1:1) and 40% concentrate. Diets were isonitrogenous (16.2% CP), but ether extract varied from 2.3 to 3.7% according to SBO addition. Breed responses to treatments were similar despite the differences between breeds (LC vs. MN; P < 0.001):
DMI (3.06 vs. 2.43 kg/d), milk yield (2.07 vs. 1.08 L/d), and fat (5.60 vs. 6.63%) and casein (3.70 vs. 4.13%) milk contents. Feed intake (2.74 kg DM/d) did not vary between treatments. Addition of SBO increased milk and milk fat yields (6.2 and 5.3%, respectively; P < 0.05), and long chain fatty acids (38%; P <0.001), but decreased (P < 0.001) milk protein, CN, and medium and short chain fatty acids. Increases in C18:1, C18:2 and CLA were 56, 22 and 300% (P< 0.05), respectively. Addition of enzymes increased milk and true protein yields (6.1 and 4.2%, respectively; P < 0.05), but decreased (P < 0.05) fat, total and true protein, and CN milk contents. In Exp. 2, the digestibility of the diets used in Exp. 1 was measured in 8 dry and open MN ewes in randomized block design (two periods of 20 d). When used alone, SBO increased ether extract digestibility (P < 0.001) but did not vary DM (64.4%), OM (67.9%) and NDF (53.6%) digestibilities. Moreover, the E treatment increased (P < 0.05) DM (8%), OM (7%) and NDF (12%) digestibilities. With regard to the SBO plus E treatment, SBO decreased (P < 0.05) DM (8%), OM (9%) and NDF (14%) digestibilities, and E complex was unable to recover the control values. Surface effects of soybean oil may have been responsible for the decrease of enzyme activity.
Domaines
Sciences du Vivant [q-bio]
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