Modeling extended lactations of dairy cows
Uloženo v:
| Autoři: | , , , |
|---|---|
| Médium: | artículo |
| Datum vydání: | 2000 |
| Popis: | 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. |
| Země: | Repositorio UNA |
| Instituce: | Universidad Nacional de Costa Rica |
| Repositorio: | Repositorio UNA |
| Jazyk: | Inglés |
| OAI Identifier: | oai:https://repositorio.una.ac.cr:11056/24079 |
| On-line přístup: | http://hdl.handle.net/11056/24079 https://doi.org/10.3168/jds.S0022-0302(00)75005-3 |
| Access Level: | acceso abierto |
| Klíčové slovo: | DAIRY CATTLE GANADO DE LECHE PRODUCCION LECHERA MILK YIELD COSTA RICA |