The effects of bull exposure and lasalocid on the development of replacement beef heifers

Autor:	D. R. Ward, R. P. Del Vecchio, W. P. Sutherland, W. P. McCaughey, J. A. Small
Rok vydání:	2000
Předmět:	Estrous cycle Delayed puberty media_common.quotation_subject Ice calving Beef cattle Biology Breed chemistry.chemical_compound Animal science Food Animals chemistry medicine Weaning Animal Science and Zoology medicine.symptom Ovulation Lasalocid media_common
Zdroj:	Canadian Journal of Animal Science. 80:615-624
ISSN:	1918-1825 0008-3984
Popis:	At weaning in the fall, crossbred heifers (n = 224), born in either the winter (January–February) or spring (March–April), were assigned on the basis of age, sire-breed and body weight to one of two similar winter housing facilities (with or without sterilized bulls), and to one of two forage-based (87%) diets (with or without lasalocid, 200 mg d−1) within each housing facility. Observations for estrus were made twice daily. Timed AI (66 h after PGF2α) was used to breed heifers for the first time at 14 mo of age. Plasma progesterone concentrations were used to confirm estrus/ovulation and to determine the PGF2α response rate. Bull exposure advanced puberty in winter-born heifers, but delayed puberty in spring-born heifers (P ≤ 0.029). Similarly, timed AI pregnancy for winter-born heifers was higher with than without bull exposure (58.9 vs. 32.5 ± 5.3%; P = 0.017) while the opposite occurred for the spring-born group (27.1 vs. 59.1 ± 4.7%; P
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::75f6ddaf1b9ccae5fa2b800a43e3cb2f https://doi.org/10.4141/a99-127 Zobrazit plný text záznamu