Abstract
The effects of body weight, hormone treatment (Syncro-Mate-B treatment of Searle Agriculture, Inc.) and system of breeding were studied in 323 Santa Gertrudis heifers. Heifers were weighed individually and fed in a manner such that attained weight groups (AWG) differed (P<.01) in weight at the start of the breeding season. The weights were 341 and 377 kg for AWG1 and AWG2, respectively. On the basis of AWG and weight 30 days prior to the start of breeding, cycling or noncycling heifers were divided into: A natural mating single sire group (SS) (20 heifers per bull, 4 groups), natural mating multiple sires group (MS) (82 heifers and 4 bulls), artificial insemination (AI) (81 heifers), and artificial insemination hormone treatment (SBT) (80 heifers). AWG affected (P<.05) the number of heifers reaching puberty by the start of the breeding but not the number cycling after 45 and 60 days or the number pregnant after 21, 45 and 60 days. Breeding groups differed (P<.05) in heifers pregnant after 4, 21, 45 and 60 days of breeding. After 60 days of breeding, the number of animals pregnant in the naturally mated groups (68%) was greater (P<.05) than the number pregnant in the artificially mated groups (47%). Only one bull was used in the AI program. Consequently, results should not be interpreted as differences in AI and natural mating, but may be a result of poor fertility in one bull. Pregnancy rates obtained after 60 days of breeding were not different (P<.05) from those obtained after 45 days. Body temperature at time of insemination did not appear (P<.05) to be a factor affecting fertility. Elevations above 39.7°C tended to be recorded only following the synchronization treatment and did not appear (P<.05) to have an adverse effect. Pregnancy rate was not different (P<.05) from artificial insemination occurring 12 hours following detection of estrus (38%) as compared to 24 hours (31%). Quantity of cervical-vaginal secretions was not related to (P<.05) fertility. Pregnancy rate was reduced (P<.05) when secretions were described as abnormal (cloudy).
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
