Effects of stage of lactation and season on udder development and milk yield in pasture-fed cows

S.J. Eichler and T.B. McFadden

AgResearch, Ruakura Research Centre, Private Bag 3123, Hamilton, New Zealand.

Proceedings of the New Zealand Society of Animal Production, 1996, 56: 58-60

Effects of stage of lactation and season on mammary development and milk yield were determined in three herds of lactating Friesian cows (n~25 cows/herd) during June and July 1995. The herds in early, mid or late lactation calved in Apr-95, Jan-95 or Oct-94, respectively.

Milk yield, in June, was higher in early and mid than in late lactation (16.1, 15.3 and 11.7 kg/d respectively, P<0.001). In July, yield was highest in early lactation and significantly lower with each successive stage of lactation (14.0, 12.5 and 10.4 kg/d, P<0.02). Yield decreased from June to July (14.4 to 12.3 kg/day, P<0.001) under increasingly severe nutritional/environmental influences. Udder capacity was higher in early and mid lactation than in late (16.1, 16.2 and 14.3 L, P=0.07), and decreased 18% from June to July (17.1 to 14.0 L, P<0.001). These results suggest that loss of mammary capacity is an important cause of declining milk production due to stage of lactation and season.

Keywords: NZSAPAB; Mammary gland; development; persistency; bovine; milk.

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Last Updated 18-03-1997