CHEMICAL-COMPOSITION AND CLOTTING PROPERT IES OF MILK SECRETED DURINGLATE PREGNANCY BY DAIRY-COWS MANAGED WITHOUT THE DRY PERIOD

Among 12 dairy Holstein cows in their first lactation that we attempte d to milk until their 2nd calving, five had to be dried off, 9 days be fore calving on average. Milk progressively enriched in somatic cells and fat. Increase in proteins was mainly due to caseins but soluble pr oteins increased relatively more, so that the casein/protein ratio dec reased. Increase in IgG1 explained 80% of the soluble protein augmenta tion. Free fatty acids measured either in the milk just milked or afte r 26 h in refrigerator highly increased in late pregnancy. pH collapse d just before calving (6.22). Rennet clotting time (Ri) and curd firmn ess time (K20i) measured at natural pH were divided by a nearly 3 fact or whereas curd firmness (A30i) increased by approximately 40 %. Measu red at standardized pH (6.60) these clotting properties changed simila rly but in an attenuated manner. In the succeeding lactation, secretio n of milk by these cows was lower than that by the control cows (n = 8 ) conventionally dried off in the late preceding lactation, but their milk was richer in proteins.