Abstract
The objective of this study was to evaluate seasonal changes of cortisol and prolactin (PRL) concentrations in Brahman and Hereford bulls moved to locations that differ in geographical and environmental conditions. Postpubertal Hereford bulls from Montana (n = 15) and Nebraska (n = 15) and Brahman bulls from Texas (n = 18) were located in or relocated to Montana, Nebraska or Texas so that each location had 5 Montana Herefords, 5 Nebraska Herefords and 6 Texas Brahman bulls. Blood samples were collected at 20-minute intervals for 8 hours in November (Fall 1), April (Spring) and November (Fall 2) of the next year. These dates corresponded to 6, 12 and 18 months, respectively, after relocation in May of the first year. Cortisol concentrations were higher (P<0.05) in Fall 1 than in Fall 2 and were higher (P<0.05) for bulls in Montana than for bulls in Texas. The decrease in cortisol concentrations from Fall 1 to Fall 2 was negatively related (P<0.05) to age and weight. There was a three-way interaction (P<0.05) of breed-type origin, location and season for PRL concentrations. Seasonal patterns of PRL concentrations differed between relocated Texas Brahman and Hereford bulls, and patterns for relocated bulls differed from those of the nonrelocated bulls. Seasonal patterns of PRL were influenced to a greater extent by relocation in Texas Brahman bulls than in Hereford bulls.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 641-654 |
| Number of pages | 14 |
| Journal | Theriogenology |
| Volume | 37 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 1992 |
Funding
Acknowledgements This article is contribution No. J-2585 from the Montana Agricultural Experiment Station. It is Journal Paper TA 26029 from the Texas Agricultural Rxperiment Station: and this study is a contribution to Western Regional Project, W-112, and was supported in part by the American Brahman Breeders Association, Houston, TX. The authors thank K. Curry, J. Leary, M. Guthrie. D. Neuendorff. A. Lewis, A. Kuger, S. Furman and T. Gavin for their technical services. Mention of trade name, proprietary product or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply its approval to the exclusion of other products that may be suitable. aAddress correspondence and reprint requests to J. G. Berardinelli.
Keywords
- bulls
- cortisol
- prolactin
- relocation
- seasonal variation
ASJC Scopus subject areas
- Small Animals
- Food Animals
- Animal Science and Zoology
- Equine