Milk production and lactation curve of guinea pigs

Milk was collected daily from 65 albino English guinea pigs throughout the first 21 days of lactation. Mean milk yield was 21.7 +/- .38 g per day per animal. Production on the 1st day of lactation was 10.8 +/- .44 g. It peaked on days 6 and 7 at 40.1 +/- 1.17 g and then decreased. It was 18.7 +/- .93 g on day 14 and 2.9 +/- 2.5 g on day 21. Total milk production for 21 days varied from 223 to 787 g with a mean of 455 +/- 13.2 g. Predictive equations for lactation curves included linear, quadratic, cubic, linear-, quadratic-, cubiccum-log, and several exponential models. The equation chosen was Y(g) = 10.23D .913e-.00984D2 where Y was milk production per day and D was day of lactation. This equation had a coefficient of determination of .812 for an individual response. Alternately, three lines could be used to fit the lactation curve. These were: Y = .739 + 10.35D - .625D2 for days 1 to 6, Y = 61.9 - 3.10D for days 7 to 18, and Y = 25.5 - 1.08D for days 18 to 21.