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Animal‐Level Factors Affecting Ovarian Function in Bos indicus Heifers Treated to Synchronize Ovulation with Intravaginal Progesterone‐Releasing Devices and Oestradiol Benzoate
Author(s) -
Butler SAA,
Phillips NJ,
BoeHansen GB,
Bo GA,
Burns BM,
Dawson K,
McGowan MR
Publication year - 2012
Publication title -
reproduction in domestic animals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.546
H-Index - 66
eISSN - 1439-0531
pISSN - 0936-6768
DOI - 10.1111/j.1439-0531.2011.01905.x
Subject(s) - ovulation , estradiol benzoate , medicine , endocrinology , corpus luteum , zoology , biology , ovary , chemistry , estrogen , hormone , ovariectomized rat
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 (P 4 ); 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× PGF 2α [500 μg prostaglandin F 2α (PGF 2α )] on Day −16 and −2 (n = 18). Intravaginal progesterone‐releasing device‐treated heifers received 250 μg PGF 2α 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 P 4 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.