Genetics decide dry matter intake

Dry matter intakes vary greatly according to the strain and genetic merit of Holstein Friesians, according to a study at Teagasc Moorepark, Co Cork.

Sean McCarthy told delegates at the recent British Grassland Society Research Conference, Cirencester that three strains of cows were assessed: High production North American; high durability, medium merit North American; and New Zealand cows imported as embryos. A group of each was fed on three different feeding systems.

“There proved to be a large genetic variation on grazing behaviour which influences dry matter intake.

” The high production strain cows had the highest grass dry matter (DM) intake and total DM intake, 0.9 and 1kg a day higher than the other two, respectively, on the high output from pasture system, said Mr McCarthy.

However, the New Zealand strain achieved a higher intake/kg of liveweight and longer grazing time than both other strains, more than an hour a day longer than the high durability strain and 24 mins more than the high production strain.

Yet, when fed 3.5kg DM of concentrate, the NZ strain ate 2.8kg DM a day less grass, whereas the high production cows only ate 0.6kg DM less grass. So feeding concentrate to the NZ stain reduced their feeding drive for grass. All cows demonstrated the same bite size and bite rate.