Most difference with grazing
HIGH merit cows best outperform medium merit cows on grass-based systems.
Milk production for the groups in both the Moorepark and high grass intake feeding systems was similar last year and this year.
The difference in milk production between genotypes is lowest in the high concentrate system.
High merit cows eat more grass than their medium merit contemporaries. When on grass only last summer the high and medium merit heifers had daily intakes of 15.6 and 14.8kg DM, respectively. Pat Dillon, who ran the research, said the high merit cows ate 5% extra grass over the grazing season. But, he stressed, securing such performance off grass required skilled management.
Time spent grazing and the grazing pattern over 24 hours was similar for genotypes and feeding systems. But there was a trend to fewer, longer grazing bouts in the medium merit animals and more, shorter bouts for the high merits.
The key difference in grazing behaviour both within and between the feeding systems was bite rate.
High merit cows had higher biting rates than their medium merit counterparts within each feeding treatment. When the high merit cows only were considered, there was a difference between the feeding systems. The highest bite rate was recorded for cows on the standard Moorepark system, then for the high grass intake system and lastly the high concentrate system. The pattern was similar for the medium merit animals.
Grazing time was fairly constant – from 9.5 to 1