Milk secretion in machine-milked and suckled cows

In the period between parturition and the 100th day of lactation (early lactation), 12 cows were machine milked while a further 12 were suckled twice daily, each by 4 calves. All animals were machine milked between the 100th and 230th day of lactation (mid-lactation). Thereafter, until the end of lactation, the early lactation treatments were repeated. There were 2.1 % of udder quarters infected in suckled cows in early lactation and 29.2% in those that were machine milked. This difference persisted into the mid-lactation period. Suckling at lactation-end did not lead to any marked alteration in the number of infected quarters. In early lactation, the total milk yield per animal of the suckled and machine-milked cows, respectively, was 1751 and 1593 kg (an 11.3% increase in the suckled animals) and in the mid lactation period, 1452 and 1340 kg (a 7.7 % increase in the suckled animals). Suckling in early lactation had no effect on the composition of milk produced in the subsequent mid-lactation period. Animals suckled in late lactation yielded 22.4% more milk (214 versus 166 kg per animal) than did their machine-milked herd mates. The marked increase in milk yield in suckled animals in early lactation may be attributable to factors such as the degree of milking stimulus or udder evacuation but must arise largely as a result of the almost total absence of mammary infections in the suckled animals. The increased milk pro duction concurrent with suckling in late lactation was attributed to the greater degree of stimulus applied to the animals which were suckled in this period.