A physiological basis of genetic improvement in milk production of Friesian and Jersey cows

S.R. Davis, G.A. Hughson, A.M. Bryant and D.D.S. Mackenzie

Ruakura Animal Research Station, Ministry of Agriculture and Fisheries, Hamilton and Department of Animal Science, Massey University, Palmerston North

Proceedings of the New Zealand Society of Animal Production. 1985, 45: 21-26

The difference in milk production of HBI and LBI Jersey herds (2 to 4 litres/day) was entirely attributable to difference in udder volume. This difference was generated during late pregnancy. Udder volume declined during lactation; 35 to 40% of udder volume at calving being lost by 20 weeks of lactation.

There was no difference in udder volume between BHI and LBI Friesian cows measured at peak and in late lactation. Differences in production between these herds were due to increased udder productivity in the HBI animals (HBI, 2.0 litres/litre tissue/d; LBI 1.8 litres/litres tissue/d). Udder productivity in Friesians was 25% greater than in Jersey cows at peak and in late lactation.

Milk yield and udder volume were significantly correlated (P<0.05) in Friesian and Jersey cows at all stages of lactation.

Genetic selection of Friesian and Jersey cows has resulted in more productive animals in both breeds but through differing physiological mechanisms.

Keywords: NZSAPAB; Milk yield; udder volume; udder productivity; Jersey; Friesian; lactation; breeding index.