Modeling lactation curves of "Barrosa" beef cattle with Woodʹs model

This study aimed to investigate the lactation curve properties of primiparous and mul-tiparous Barrosa cows, using two different milking systems. A data set with 2518 daily milk yields of 15 primiparous (107 test day records by lactation) and 11 multiparous (83 test day records by lactation) cows was individually fitted with the Woodʹs model by the application of a non linear procedure. Milk yield measurements were recorded using a weigh-suckle-weigh technique in half of the cows and the remaining cows were hand-milked. Average daily milk yield of primi-parous and multiparous suckled cows were 4.9 and 5.2 kg, respectively, while correspondent scores on milked cows were lower (2.4 and 3.0 kg). All 26 fitted lactations followed the typical curve shape with high goodness of fit. Analysis performed on Woodʹs parameters indicated that milked cows have a peak yield of 3.5 and 4.6 kg reached at lactation day 23 and 16, for primiparous and multiparous, respectively. On the other hand, suckled cows reached later (56-63 d) their peak of lactation and the peak yield (5.3-5.7 kg) was greater than milked cows. The absence of the calf and the cowʹs difficulty in adapting to the hand-milking can explain differences between milked and suckled cows. Barrosa cows, in their traditional production system, have lactation yields of 805 and 843 kg in parities 1 and 2, respectively.