Tauck SA, Olsen JR, Wilkinson JR, Wedlake RJ, Davis KC, Berardinelli JG
Reprod. Biol. Endocrinol. 2010;8:89
PMID: 20642864
Abstract
BACKGROUND: The physiological mechanism by which bulls stimulate resumption of ovarian cycling activity in postpartum, anovular, suckled cows after calving may involve the concurrent activation of the hypothalamic-hypophyseal-ovarian (HPO) axis and hypothalamic-hypophyseal-adrenal (HPA) axis. Thus, the objectives of this experiment were to determine if characteristics of temporal patterns of cortisol and luteinizing hormone (LH) in postpartum, anovular, beef cows are influenced by acute exposure to bulls. The null hypotheses were that daily, temporal characteristics of cortisol and LH concentration patterns do not differ between cows exposed acutely to bulls or steers.
METHODS: Sixteen cows were assigned randomly 67 +/- 4 (+/- SE) after calving to be exposed to bulls (EB, n = 8) or steers (ES, n = 8) 5 h daily for 9 d (D 0 to 8). Blood samples were collected daily from each cow via jugular catheters at 15-min intervals for 6 h from 1000 to 1600 h each day. The 5-h exposure period began 1 h after the start of the intensive bleeding period. Characteristics of cortisol and LH concentration patterns (mean, baseline, pulse frequency, pulse amplitude, and pulse duration) were identified by PULSAR analyses.
RESULTS: Mean cortisol concentrations decreased (P < 0.05) in cows in both treatments from D 0 to D 2. Thereafter, mean cortisol concentrations stabilized and did not differ (P > 0.10) between EB and ES cows. The decrease in mean cortisol concentrations in EB and ES cows from D 0 to D 2 was attributed to cows acclimatizing to intensive blood sampling and handling procedures. Consequently, analyses for characteristics of cortisol and LH concentration patterns included D 2 through 8 only. Cortisol mean and baseline concentrations, and pulse amplitude did not differ (P > 0.10) between EB and ES cows. However, cortisol pulse duration tended to be longer (P = 0.09) and pulse frequency was lower (P = 0.05) in EB than ES cows. LH pulse frequency was greater (P = 0.06) in EB than ES cows. All other characteristics of LH concentration patterns did not differ (P > 0.10) between EB and ES cows. Characteristics of cortisol concentration patterns were not related to characteristics of LH concentration patterns for ES cows (P > 0.10). However, as cortisol pulse amplitude increased, LH pulse amplitude decreased (b1 = -0.04; P < 0.05) for EB cows.
CONCLUSIONS: In conclusion, exposing primiparous, postpartum, anovular, suckled cows to bulls for 5-h daily over a 9-d period did not alter mean concentrations of cortisol or LH compared to mean concentrations of cortisol and LH in cows exposed to steers. However, exposing cows to bull in this manner altered characteristics of temporal patterns of both LH and cortisol by increasing LH pulse frequency and decreasing cortisol pulse frequency. Interestingly, in cows exposed to bulls, as amplitude and frequency of cortisol pulses decreased, amplitudes of LH pulses increased and frequency of LH pulses tended to increase. Thus, the physiological mechanism of the biostimulatory effect of bulls may initially involve modification of the HPA axis and these changes may facilitate activation of the HPO axis and resumption of ovulatory cycles in postpartum, anovular, suckled cows.
[Title]
anovular: anovulatory 無排卵の
acutely: 鋭く，激しく.
[Abstract]
resumption: (中断後の)再開(始), 続行 〔of〕
concurrent: Occurring at the same time. 同時(発生)の，伴う.
amplitude: largeness, fullness; wideness in range or extent. 振幅, 広さ
acclimatize: 気候順応する, 気候順化する
[Conclusions]
In conclusion, bull exposure for 5 h daily over a 9-d period did not appear to alter mean concentrations of cortisol or LH; however, bull exposure altered temporal patterns of cortisol and LH concentrations by decreasing frequency of cortisol pulses, tending to increase duration of cortisol pulses, and increasing frequency of LH pulses. Even though no biostimulatory effect, i.e., resumption of ovarian cycling activity, was observed in cows within the 9-d experiment, these results indicate that the presence of bulls for 5 h daily over a 9-d period altered the activity of the HPO axis and influenced adrenal function and/or regulation. Therefore, bulls may release a pheromone(s) that has an immediate effect on activity of the HPO axis and adrenal function and/or regulation of primiparous, postpartum, anestrous, suckled cows. This effect may facilitate or support the physiological mechanism whereby the biostimulatory effect of bulls accelerates resumption of ovarian cycling activity in primiparous, postpartum, anestrous, suckled cows.
[Introduction]
excretory: Of, relating to, or used in excretion. 排泄の.
[Methods]
steer: castrated male cattle beast over a year of age. (食用)去勢牛.
EB groupは2頭の成熟したbullに曝され、ES groupは2頭のsteerに曝された。