Daily milk weights from 1006 lactations on 775 Holstein-Friesian cows in 42 herds and monthly test-day weights from 102 540 lactations on 73 717 cows in 17 481 herd-year-seasons were used to study the influence of covariances among milk weighings within a lactation on three models for describing the shape of the lactation curve for individual cows. The models included a gamma function, an inverse quadratic polynomial function, and a regression model of yields on day in lactation (linear and quadratic) and on log of 305 divided by day in lactation (linear and quadratic). For each model, several variance-covariance matrices of the observation vector were used. Models were compared on the basis of squared deviations of predicted versus actual milk weights and on the correlation between predicted and actual weights through the lactation averaged over cows. Better predictions were observed when covariances among test-day yields were ignored while models could be ranked regression model, gamma function, and inv...

Accounting for covariances among test day milk yields in dairy cows

Energy balance of dairy cattle in relation to milk production variables and fertility.

The relationship between milk yield and the incidence of some diseases in dairy cows.

Factors Affecting the Shape of Lactation Curves of Holstein Cows from the Balikesir Province of Turkey

Assessing economic consequences of foot disorders in dairy cattle using a dynamic stochastic simulation model

MANY factors may influence the total milk yield of a single lactation, but the general shape of the curve, defined by the locus of weekly yield, remains substantially unchanged. Economically, the configuration of the curve is important, for the animal which produces milk at a moderate level steadily throughout her lactation is to be preferred to one which produces a great deal of milk at her peak but little thereafter (see Cersovsky1 for a review of the literature).

Algebraic Model of the Lactation Curve in Cattle

THE lactation curve in cattle has been represented by the function where yn is the average daily yield in the nth week and A, b and c are constants. I have previously1 suggested a measure of persistency (the extent to which peak yield is maintained) given by which was related to expected total yield (Y) by Y = AeS.

P. D. P. Wood

Papers

Algebraic Model of the Lactation Curve in Cattle

Factors affecting Persistency of Lactation in Cattle