Effects of environmental lighting on early semen production and correlated hormonal responses in turkeys

Abstract

Recent work at our institution on lighting turkey males for semen production and correlated changes in plasma luteinizing hormone (LH) and testosterone (T) are summarized in this paper. In sexually mature males, both LH and T are secreted in pulses, with a pulse of LH about 10 min prior to a pulse of T. Pulses of LH and T occurred about every 2 h and were equally distributed between the light (L) and dark (D) portions of a 14 h L:10 h D d. The pattern of secretion and overall concentrations of LH and T were not affected by intermittent photoperiod lighting (1 L:2 D, 8 x d) in comparison to continuous photoperiod lighting (14 L:10 D) lighting. Pulses of LH or T were not entrained by L or D with the intermittent or continuous lighting treatment. To study the interaction of age and lighting treatment, males were exposed to one of two lighting treatments: long-day photoperiods (16 L:8 D) d(-1) from 10 to 12 or 29 wk of age (WOA) (Treatment LDLD) or short-day photoperiods (6 L:18 D d(-1) from 10 or 12 to 29 WOA, then long-day photoperiods (Treatment SDLD). Males in the LDLD treatment attained puberty earlier (25 WOA) than those in the SDLD treatment. In the later treatment, most of the males attained puberty after 29 WOA. Both LH and T were low until 18 WOA in the LDLD males, then both increased to adult levels over the next 2 to 3 wk. In the SDLD males, LH and T were lower than in the LDLD males until 48 h after switching to long-day photoperiods, when both were transiently higher before declining to lower adult levels by 35 WOA. Secretory patterns of LH and T were estimated at 13, 23, and 35 WOA, under both lighting treatments. At 13 WOA, LH and T were secreted in pulses, but levels of both hormones were low and not different between lighting treatments, and none of the birds (0/4) in either treatment were producing semen. At 23 WOA, LH and T were secreted in robust pulses, with the LDLD males having higher concentrations of LH and T than the SDLD males. At 23 WOA, most of the males in the LDLD group (3/4) but none in the SDLD group (0/4) were producing semen. At 35 WOA, 6 wk after photostimulation of the SDLD group, all males (4/4) in both groups were producing semen, and LH and T were at adult levels. However, fewer pulses of T were noted for males in the SDLD treatment.

Effect of various photoperiods on testicular weight, weekly sperm output and plasma levels of LH and testosterone over the reproductive season in male turkeys

“…Previous studies using commercial breeder turkeys revealed a high degree of sensitivity to photoperiod for TW [10,11], semen output [18], and circulating LH and testosterone concentrations [6][7][8][9]. The present results confirmed previous observations [10,11] that prepubertal male turkeys maintained under constant long days are precocious semen producers (26-29 wk) In .…”

“…In males from previously named species, LH and testosterone are discharged in pulsatile patterns during both the photophase and the scotophase of the nycthemere. Moreover, it appears that in mature male www.journals.elsevierhealth.com/periodicals/the Theriogenology 66 (2006) [851][852][853][854][855][856][857][858][859] turkeys, a pulsatile pattern of testosterone is maintained regardless of its baseline concentration, whereas the pulsatile pattern of LH is maintained only if associated with low plasma concentrations of both LH and testosterone [6,7]. Turkey males in semen production exposed to continuous or intermittent light regimes had minor differences in patterns of LH and testosterone secretion [7,8].…”

“…Moreover, it appears that in mature male www.journals.elsevierhealth.com/periodicals/the Theriogenology 66 (2006) [851][852][853][854][855][856][857][858][859] turkeys, a pulsatile pattern of testosterone is maintained regardless of its baseline concentration, whereas the pulsatile pattern of LH is maintained only if associated with low plasma concentrations of both LH and testosterone [6,7]. Turkey males in semen production exposed to continuous or intermittent light regimes had minor differences in patterns of LH and testosterone secretion [7,8]. Immature male turkeys exposed first to a short (6L:18D) and then to a long photoperiod (16L:8D) had marked increases in plasma concentrations of both LH and testosterone during the first 4 wk following photostimulation [9]; this was followed by an increase in testis weight but not in semen output.…”

“…Other than work by Bacon et al [7], there has been little fundamental research with commercial breeder turkeys addressing the role of photoperiod on the endocrine control of semen production. The objectives of the present study were to assess the impact of various photoperiods on testis development, semen output, and hormonal (LH, testosterone) status in male turkeys over a reproductive season.…”

Succession in the intestinal microbiota of preadolescent turkeys

“…Other positive functions such as host‐derived signals may stimulate the transformation. Possible host‐derived signals include puberty, although measurable levels of testosterone do not accumulate until week 19 (Bacon et al , 2000). Other signals could be derived from the expansion of the gut‐associated lymphoid tissue that occurs between 6 and 12 weeks of age and the concurrent increase in TCR1‐expressing T cells between 9 and 12 weeks (Befus et al , 1980; Lillehoj & Chung, 1992).…”