Abstract

The average milkfat test for groups of first Friesian x Jersey (FJ) cows in 9 Waikato herds was 4.68%, ranging from 4.36% to 5.46%. Animals with 75% Friesian breeding had an average test 0.05% lower than their first cross contemporaries whereas those with 25% Friesian breeding had an average test which was 0.25% higher. Variation in colour and height at withers were not reliable indicators of an FJ animal's test. Regression analyses with records of sires' progeny-tested by the New Zealand Dairy Board from 1961 to 1979 showed that each 1 unit increase in milkfat breeding index (BI) in Jerseys was associated with an increase of 0.85 units in milk BI. The comparable figure for Friesians was 0.55 milk BI units. Since 1961, the average milkfat BI of Jersey sires selected for further use has increased by 24 units (117 to 141) with an associated increase in milk BI of 14 units (114 to 128). Comparable changes for Friesian sires were 17 units (121 to 138) and 6 units (115 to 121). The average live weight at calving over 4 seasons at Ruakura for high BI Jerseys was 385 kg compared to 404 kg for 'AB' Friesians. The concurrent increases in milk and milkfat BI's in the Jersey breed may have been associated with a greater increase in live weight than in the Friesian breed. Owners of herds of FJ cows need not expect substantial changes in milkfat test or live weight through the continued use of Friesian sires to produce replacement heifers.

KL, Macmillan, VK Taufa, and P Phillips

Proceedings of the New Zealand Society of Animal Production, Volume 44, , 63-66, 1984