| Autor: |
Butler, SAA, Phillips, NJ, Boe-Hansen, GB, Bo, GA, Burns, BM, Dawson, K, McGowan, MR |
| Předmět: |
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| Zdroj: |
Reproduction in Domestic Animals; Jun2012, Vol. 47 Issue 3, p463-471, 9p, 2 Diagrams, 4 Charts, 2 Graphs |
| Abstrakt: |
Contents The primary objective of this study was to investigate the impact of animal-level factors including energy balance and environmental/management stress, on the ovarian function of Bos indicus heifers treated to synchronize ovulation. Two-year-old Brahman (BN) (n = 30) and BN-cross (n = 34) heifers were randomly allocated to three intravaginal progesterone-releasing device (IPRD) treatment groups: (i) standard-dose IPRD [Cue-Mate® (CM) 1.56 g; n = 17]; (ii) half-dose IPRD [0.78 g progesterone (P4); CM 0.78 g; n = 15]; (iii) half-dose IPRD + 300 IU equine chorionic gonadotrophin at IPRD removal (CM 0.78 g + G; n = 14); (iv) and a control group, 2× PGF2α [500 μg prostaglandin F2α (PGF2α)] on Day −16 and −2 (n = 18). Intravaginal progesterone-releasing device-treated heifers received 250 μg PGF2α at IPRD insertion (Day −10) and IPRD removal (Day −2) and 1 mg oestradiol benzoate on Day −10 and −1. Heifers were managed in a small feedlot and fed a defined ration. Ovarian function was evaluated by ultrasonography and plasma P4 throughout the synchronized and return cycles. Energy balance was evaluated using plasma insulin-like growth factor 1 (IGF-I) and glucose concentrations. The impact of environmental stressors was evaluated using plasma cortisol concentration. Heifers that had normal ovarian function had significantly higher IGF-I concentrations at commencement of the experiment (p = 0.008) and significantly higher plasma glucose concentrations at Day −2 (p = 0.040) and Day 4 (p = 0.043), than heifers with abnormal ovarian function. There was no difference between the mean pre-ovulatory cortisol concentrations of heifers that ovulated or did not ovulate. However, heifers that ovulated had higher cortisol concentrations at Day 4 (p = 0.056) and 6 (p = 0.026) after ovulation than heifers that did not ovulate. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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