|Olson, T. - UNIV. FL, GAINESVILLE, FL|
|Lucena, Carlos - UNIV. CENTROCCIDENTAL|
Submitted to: Archivos Latinoamericanos De Produccion Animal
Publication Type: Proceedings
Publication Acceptance Date: March 28, 2000
Publication Date: March 28, 2000
Interpretive Summary: Nonadapted dairy cows continue to suffer from reduced milk yields and pregnancy rates in warm climates. In the tropics and subtropics of the world, dual-purpose cattle (i.e., used for meat and milk production) must be heat tolerant as their owners can seldom afford to provide anything other than shade to alleviate such stress. Senepol cattle are a Red Poll-based non-Zebu (Bos taurus) composite with very short hair likely also possess criollo breeding that we have previously shown to be heat tolerant. At least one other composite breed, the Carora of Venezuela that is 5/8 or more Brown Swiss in breed composition with the remaining percentage being milking criollo, is composed of animals with a high frequency of slick hair coats. In Venezuela, we demonstrated that rectal temperatures of slick-haired Carora x Holstein crossbred cows were consistently lower than those of normal-haired contemporaries in spite of an apparent lack of heat stress among the normal cows. The slick-haired cows produced more milk than their normal-haired contemporaries, but the greatest advantage was that days open were 22 days less for slick-haired cows. The impact of lowered rectal temperature due to the slick hair condition under the management used in this study is likely less than would be observed under less intensive grazing systems.
Technical Abstract: The impact of hair coat type on the rectal temperatures, milk yields, and days open of Carora x Holstein F1 and 3/4 Holstein:1/4 Carora crossbred cows maintained under drylot conditions was studied near Barquisimeto, Lara, Venezuela. Hair coat type was subjectively classified as 1) very short and sleek ("slick"), 2) intermediate or doubtful or 3) normal, similar to contemporary Holsteins. The rectal temperatures of the slick-haired F1 and 3/4 cows were 0.4 and 0.8 degrees C (P<0.001) lower than those of their normal contemporaries, respectively in spite of an apparent lack of heat stress among normal cows. Slick-haired F1 cows had 22 fewer days open (P<0.001) and slightly higher milk yields (P<0.05) than their normal-haired F1 contemporaries. The impact of lowered rectal temperatures on milk yield and reproductive traits due to slick hair coat type is likely to be greater under grazing conditions and in locations with more extreme levels of heat stress than were endured by the cattle in this study.