Modeling extended lactations of dairy cows
Nine mathematical models were compared for their ability to predict daily milk yields (n = 294,986) in stan- dard 305-d and extended lactations of dairy cows of Costa Rica. Lactations were classified by parity (first and later), lactation length (9 to 10, 11 to 12, 13 to 14, 15 to 16, and 1...
| Autores Principales: | Koops, W. J., Herrero, M., VAN ARENDONK, J.A.M., Vargas, Bernardo |
|---|---|
| Formato: | Artículo |
| Idioma: | Inglés |
| Publicado: |
American Dairy Science Association
2022
|
| Materias: | |
| Acceso en línea: |
http://hdl.handle.net/11056/24079 https://doi.org/10.3168/jds.S0022-0302(00)75005-3 |
| Sumario: |
Nine mathematical models were compared for their
ability to predict daily milk yields (n = 294,986) in stan-
dard 305-d and extended lactations of dairy cows of
Costa Rica. Lactations were classified by parity (first
and later), lactation length (9 to 10, 11 to 12, 13 to 14,
15 to 16, and 16 to 17 mo), and calving to conception
interval (1 to 2, 3 to 4, 5 to 6, 7 to 8, and 9 to 10 mo).
Of the nine models, the diphasic model and lactation
persistency model resulted in the best goodness of fit
as measured by adjusted coefficient of determination,
residual standard deviation, and Durbin-Watson coef-
ficient. All other models showed less accuracy and posi-
tively correlated residuals. In extended lactations, mod-
els were also fitted using only test-day records before
305 d, which resulted in a different ranking. The dipha-
sic model showed the best prediction of milk yield in
standard and extended lactations. We concluded that
the diphasic model provided accurate estimates of milk
yield for standard and extended lactations. Interpreta-
tion of parameters deserves further attention because
of the large variation observed. As expected, the calving
to conception interval was found to have a negative
effect on milk yield for cows with a standard lactation
length. In extended lactations, these negative effects of
pregnancy on milk yield were not observed. |
|---|