THE OBJECTIVE OF THIS STUDY WAS TO COMPARE THE GOODNESS OF FIT OF FOUR LACTATION CURVE MODELS: Wood's Gamma model (WD), Wilmink (WL), and Pollott's multiplicative two (POL2) and three parameters (POL3) and to determine the environmental factors affecting the complete lactation curve of F1 dairy sheep under organic management. A total of 5,382 weekly milk yields records from 150 ewes, under orga...

Persistency of lactation is the ability of a cow to continue producing milk at a high level after the peak of her lactation. Differences in persistency, if not properly accounted for, reduce accuracy of genetic evaluation when incomplete records are used. Persistency has also direct economic value. Reduction of feed, health and reproductive costs are the major factors which favour more persiste...

The association of birth type (single vs. double) and pregnancy type (single vs. double) with lactation performance and lactation curve was investigated in Holstein cows in Iran. Data of 243298 lactations on 138021 cows in 261 herds collected during January 2000 to December 2012 were used. The average twinning rate was 3.64% and ranged from 1.44% (primiparous) to 5.41% (multiparous). Factors as...

Nonlinear equations were compared with categorical analysis to account for DIM effects on milk production. Five different models for lactation curves were evaluated. Derived from a multiphasic lactation curve, the selected lactation curve appeared to result in random residuals and performed more consistently than the multiphasic curve. Residuals from the fitting of lactation curves were then us...

In this research, 272977 test day records collected from 659 herds during years 2001 to 2011 by the Iranian animal breeding center were used. In the first section the ability of different models to predict daily milk yield from alternative milk recording was tested. The result showed that a complex model including noon milking time plus the effect of lactation curve of Ali and Schaeffer functio...

Animals with the same lactation breeding value can have different shapes of additive genetic curve, implying differences in persistency lactation. Since environmental conditions change across lactation, animals re-rank through leading to genotype by environment interaction for daily milk yield. The objectives this project is describe curve pattern estimated values and assess extent sire cow re-...

in this research, 272977 test day records collected from 659 herds during years 2001 to 2011 by the iranian animal breeding center were used. in the first section the ability of different models to predict daily milk yield from alternative milk recording was tested. the result showed that a complex model including noon milking time plus the effect of lactation curve of ali and schaeffer functio...

Milk production is largely dependent on the shape of the lactation curve. Relevant elements of the lactation pattern are the peak yield, which represents the maximum milk yield during the lactation, and the lactation persistency, which expresses the ability of animals to maintain a reasonably constant milk yield after the lactation peak (Figure 1). Thus, persistent animals are those that show f...