Effect of dietary animal fat and methionine on dairy ewes milk yield and milk composition

The effect of supplemental animal fat, or animal fat and rumen protected methionine, on lactating dairy ewes production was evaluated in the present study. Twelve dairy pregnant ewes of the Karagouniko breed, with two embryos, were allocated to three groups (treatments), in order to examine the effect of three diets: control (C), diet with animal fat at 7% of concentrates’ DM (F) and diet F plus 5 g rumen protected methionine (RPM) per kg of concentrate (F+m). The experiment started 2 weeks before lambing and continued for the 13 first weeks of lactation. During the experiment, dry matter intake (DMI), energy supply, daily milk yield and milk composition were determined. Prepartum, DMI and energy supply did not differ between treatments C and F+m. During the first 7 weeks of lactation (from lambing to weaning), the inclusion of fat in the diet increased DMI, energy supply (P<0.001), and the milk lactose content (P<0.05), but decreased the milk fat content (P<0.05). The inclusion of fat with RPM in the diet resulted in an increase (P<0.001) of DMI, milk yield and daily fat and protein yield, compared to treatments C and F. After weaning (8-13th week of lactation), significant differences were observed only in DMI and energy intake which increased (P<0.001) for treatments F and F+m. Milk fat content reduced (P<0.05) for treatments F and F+m, compared to control, but the mean daily milk fat and protein yield did not change significantly. For the first 13 weeks of lactation there was not treatment effect on milk protein profile, while the concentration of short chain fatty acids of milk fat was reduced (P<0.001) and that of short chain fatty acids increased (P<0.001) for treatments F and F+m, compared to treatment C. From the results of this experiment it is concluded that the inclusion of animal fat in sheep diets had no significant effect on ewes milk yield, while the use of rumen protected methionine, combined with animal fat, in diets of high producing ewes, at least at the first stage of lactation, increased significantly milk yield.