Effect of heat load on milk production in cows
Marschang, F.
Deutsche Tierärztliche Wochenschrift 80(8): 187-189
1973
ISSN/ISBN: 0341-6593 PMID: 4577194 Document Number: 63670
Between Mar. and Oct. 1971, the av. daily milk yield/cow, corrected to 3.5% fat, of a herd of imported Danish Black Pied cows was studied in relation to outside air temp. In addition, 80 cows (28.5% of the herd), all in their 2nd lactation, had their milk yields studied in relation to months of calving. A graph is given showing the results. High temps. were found to cause a drop in milk production, the decrease being directly correlated with intensity and duration of the heat stress. Byre temps. were about 1 deg -3 deg C above outside temps. It is believed that when the mean daily byre temp. rises above 18 deg C, milk production begins to fall. The av. daily milk yield rose from 9.2 kg in Aug. (mean daily temp. of 28 deg C) to 12.2 kg in Sep. (mean temp. of 13 deg C). From the point of view of milk production, it was disadvantageous for cows to calve during the summer or early autumn as heat stress in late pregnancy caused them to be poorly prepared for their next lactation.