Episodic Gonadotropin Secretion in the Mature Fowl: Serial Blood Sampling from Unrestrained Male Broiler Breeders (Gallus domesticus)1

Abstract

Forty-week-old male broiler breeders were used in two experiments. Males were reared as recommended by the breeder, housed in individual cages, and cannulated to facilitate blood sampling. In experiment 1, blood samples were collected at 10- min intervals for 4 h commencing the day of cannulation (Day 0) and for 12 h on each of Days 1 and 2. In experiment 2, blood samples were collected at 10-min intervals for 8 h on Day 1. After centrifugation, plasma was stored at -20 degrees C until LH, FSH (experiment 1 and 2), testosterone, and corticosterone (experiment 1) concentrations were determined by RIA. Different statistical methods used to identify hormone secretion profiles revealed a characteristic pulsatile pattern of LH and FSH in plasma. However, LH pulses were more frequent and had greater amplitude than FSH pulses. Less than 32% of the FSH pulses were associated with LH episodes. Conversely, the association between LH and testosterone pulses averaged 83% in birds with testis weight greater than 10 g. Concentrations of corticosterone tended to increase after cannulation and remained elevated for only 3-4 h. Our data indicate that LH, FSH, and testosterone secretion is pulsatile in male broiler breeders. Additionally, LH pulses are associated with testosterone episodes but not with FSH pulses. The pulsatile pattern of FSH secretion, which is unique from those of LH, in adult males suggests that FSH secretion is independently regulated in the adult male fowl.

Testis development and gonadotropin secretion in broiler breeder males

“…In addition, birds are subjected to long-day photostimulation to maintain their reproductive productivity throughout their adult life. However, when one examines the results of testes development, using present-day management systems, much variability in testis size is observed (Vizcarra et al, 2004).…”

Contribution of Chicken GnRH-II and Lamprey GnRH-III on Gonadotropin Secretion

“…Only 23% of the LH pulses were associated with FSH episodes, suggesting that in the adult male fowl LH and FSH secretion are regulated independently (Vizcarra et al, 2004). Adapted from (Vizcarra et al, 2004) Both cGnRH-I and -II stimulates gonadotropin release in vivo and in vitro in the chicken (Hattori et al, 1986). However, cGnRH-II was not found in the median eminence of the white-crowned sparrow (Zonotrichia leucophrys gambelii), suggesting that in these species cGnRH-II does not regulate pituitary gonadotropin secretion (Meddle et al, 2006).…”

“…In addition, we have reported the episodic nature of gonadotropin secretion in the mature fowl (Vizcarra et al, 2004). Gonadotropin secretion in chickens is characterized by a pulsatile pattern with LH pulses being more frequent and having greater amplitude than FSH pulses ( Figure 2).…”

“…Furthermore, we observed that there was a lack of synchrony between the episodic release of LH and FSH. Only 23% of the LH pulses were associated with FSH episodes, suggesting that in the adult male fowl LH and FSH secretion are regulated independently (Vizcarra et al, 2004). Adapted from (Vizcarra et al, 2004) Both cGnRH-I and -II stimulates gonadotropin release in vivo and in vitro in the chicken (Hattori et al, 1986).…”

Photostimulation of male broiler breeders to different photoperiods

“…Vizcarra et al (2004) reported that in male broiler breeders a normal testis size was >10 g. Sharp et al (1977) found that only when the testes (average of left and right testis) of birds weighed more than 10 g was spermatogenesis completed and a significant increase in the mean plasma concentration of testosterone observed. These findings are in agreement with the results reported in female broiler breeders, where those provided longer photoperiods became photorefractory earlier (Lewis & Gous, 2006).…”