Relation between the distribution of time spent on pasture and protein content of the concentrate on milk yield and grazing behaviour

Abstract

The objective of this study was to assess the influence of the crude protein (CP) content (130 vs. 190 g CP kg-1) of the concentrate on milk yield and body reserves in a production system where ewes can spend a limited time on pasture. A total of 40 multiparous Latxa ewes were blocked into 4 groups on the basis of milk yield, number of days in lactation, body weight and condition score. Ewes either grazed during 4 hours continuously after the morning milking or grazed 2 hours continuously after the morning and evening milking. Ewes were assigned to one of the following experimental treatments: 2+2 hours high protein; 2+2 hours low protein; 4 hours high protein and 4 hours low protein. Ewes spending 2+2 hours grazed longer on a daily or per hour basis. Nevertheless, neither concentrate CP content nor time spent on pasture significantly affected milk yield or milk composition, but ewes with the high CP concentrate lost more weight. In conclusion, under this rationed grazing system, the inclusion of high CP supplementary concentrates resulted in very poor differences in terms of milk yield or milk composition but distribution of time spent grazing could affect the grazing behaviour.