Effects of chopping grass silage and mixing silage with concentrate on feed intake, dietary selection, chewing activity and faecal particle size of ewes in late pregnancy and early lactation

The effects of chopping grass silage and of mixing grass silage and concentrate on feed intake, dietary selection, chewing behaviour and faecal particle size in pregnant and lactating ewes were studied. The three experimental diets used in both experiments were: 1. un-chopped grass silage and 0.8 kg concentrate, fed separately (US); 2. chopped grass silage and 0.8 kg concentrate, fed separately (CS); and 3. chopped grass silage mixed with concentrate to the same forage:concentrate ratio as in the CS treatment (CM). Twin bearing/suckling ewes (n=7 per treatment) were penned and fed individually during the experiments. The silages used in Experiments 1 and 2 contained 10.9 and 11.4 MJ ME/kg dry matter (DM), 139 and 193 g CP/kg DM, and 580 and 483 g NDF/kg DM, respectively. All measurements and recordings were carried out during two four-day periods in each experiment, one in late pregnancy and one in early lactation. Daily DM intake increased from late pregnancy to early lactation by 0.7 and 1.7 kg in Exp. 1 and Exp. 2, respectively, averaged over treatments (P<0.0001). Chopping silage decreased dietary selection of feed particles with low NDF content in both periods and in both experiments (P<0.0001). Pregnant and lactating ewes fed chopped silage, separately or mixed with concentrate, spent less time eating daily compared with ewes fed un-chopped silage. Ewes also increased their daily eating time from pregnancy to lactation in Exp. 1 and, averaged over periods, increased rumination time per day and per kg DM intake in Exp. 1 and 2, compared with the ewes fed un-chopped silage. In conclusion, chopping silage decreased dietary selection, eating time and eating:rumination ratio and increased rumination time in pregnant and lactating ewes with large body size and high milk production. Mixing highly digestible grass silage with concentrates increased proportion of large particles in faeces. In early lactation, feed intake and proportion of large particles in faeces were higher, whereas eating, rumination and total chewing time per kg DMI were lower than in late pregnancy, suggesting more efficient fibre degradation in pregnancy than in lactation.