The response of broilers' adiposity to testosterone after embryonic exposure to androgen and tamoxifen

The effect of selected in ovo green light photostimulation periods on post-hatch broiler growth and somatotropic axis activity

Targeted in ovo green light (GL) photostimulation during the last days of broiler egg incubation increases embryonic expression of the somatotropic axis, similar to in ovo green light photostimulation from embryonic day (ED) 0 to the end of incubation. The aim of this study was to examine the effect of selected in ovo GL photostimulation periods on post-hatch broiler growth. Four hundred twenty fertile broiler eggs were divided into 7 treatment groups: the first incubated in the dark (standard conditions) as a negative control; the second incubated under monochromatic GL from ED0-ED20 (positive control); the third group incubated under monochromatic GL light from ED15-ED20; the fourth, fifth and sixth groups were incubated under monochromatic GL on ED16, ED17, and ED18, respectively; and the seventh group was incubated under monochromatic GL from ED18-ED20. All illumination was provided intermittently using LED lamps. After hatch, all chicks were transferred to a controlled room under standard rearing conditions. The group incubated under green light from ED18 until hatch showed similar results to the positive control group in body weights, as well as breast muscle weights (as % of body weights), and an elevation in the somatotropic axis activity during the experiment. We suggest that broiler embryos can be exposed to in ovo GL photostimulation from ED18 until hatch (hatching period), and still exhibit the same performance as obtained by photostimulation from d 0 of incubation.

Impact of Oral Supplementation of Different Levels of Tamoxifen on Productive and Reproductive Efficiencies and Carcass Traits of Avian48 and Arbor Acres Broilers

This research was aimed at estimating the effect of oral supplementation of Tamoxifen on productive efficiency, carcass characteristics, hormonal profile and gonadal structure of two broiler breeds. One hundred and eighty chicks of each breed of Avian48 and Arbor Acres were divided into three groups: control group; TAM10 group, supplied with 10 mg Tamoxifen/kg of body weight at 3, 5, 7 and 9 days of life; and TAM20 group, supplied at the same intervals with 20 mg Tamoxifen/kg of body weight. Both levels of Tamoxifen improved productive performance at early ages, but Arbor Acres produced better results with TAM20 levels than TAM10, while Avian48 breeds reacted adversely. On the contrary, Tamoxifen supplementation significantly decreased feed intake and feed conversion (after the first two weeks of life) compared to control with a higher level of decrease reported for TAM20 treatments than TAM10 and for Arbor Acres compared to Avian48 breed. Carcass traits were not affected significantly with Tamoxifen supplementation compared to control although Arbor Acres responded better to TAM20 and Avian48 for TAM10. With regard to the effect of Tamoxifen (TAM) on sex hormones, it could be concluded that TAM10 treatments showed a stimulating effect on the level of such hormones as compared with the TAM20 group with the most favourable results being clearly detectable in 42-day-old birds although both concentrations of Tamoxifen did not differ significantly from control. However, treatment of broiler chickens with Tamoxifen in different doses caused a gradual decrease in follicle production rate and eventually led to an increase of the atretic follicles in different stages of atresia. Finally, we can conclude that Tamoxifen supplementation can improve performance and carcass efficiency of broilers without changing the hormonal profile, however much research is required to estimate the best concentration required for each breed.

Role of the serotonergic axis in the reproductive failure associated with aging broiler breeder roosters

Reproductive failure associated with aging is a well-known phenomenon. However, the mechanism by which this failure occurs in broiler breeder roosters is still unclear. A previous study conducted in our laboratory, comparing young and aging broiler breeder roosters, demonstrated an elevation in hypothalamic vasoactive intestinal peptide (VIP) and pituitary prolactin (PRL) gene expression accompanied by a deterioration of gonadal axis function. This resulted in a decrease in semen-quality variables as roosters aged. The objective of this study was to examine the involvement of the serotonergic axis in the age-associated reproductive failure in broiler breeder roosters. Cobb roosters aged 64 wk were divided into 3 groups (n = 20 each): parachlorophenylalanine (PCPA) administration, active immunization against chicken VIP, and controls. At 69 wk of age, each group was divided into 2 equal subgroups: 1 received ovine PRL and the other served as controls. Weekly semen volume, concentration and motility, and plasma testosterone, estradiol, and PRL concentrations were examined. At the end of the experiment, roosters were euthanized, testes were weighed, and hypothalamus and pituitary were removed to assay the expression of genes encoding hypothalamic GnRH-I, pituitary FSH, pituitary LH, hypothalamic VIP, and pituitary PRL. Both PCPA administration and active immunization against chicken VIP significantly increased testis weight, semen volume, sperm concentration, ejaculation grade, plasma testosterone level, and GnRH-I, FSH and LH gene expression compared with controls (P ≤ 0.05). In addition, a decrease in plasma estradiol and PRL concentrations and VIP and PRL gene expression was observed in PCPA- and VIP-immunized birds compared with controls (P ≤ 0.05). Administration of PRL in all groups decreased gonadal axis function and semen-quality variables (P ≤ 0.05). Collectively, these results suggest that the increasing expression levels of the serotonergic axis in aging broiler breeder roosters inhibit proper gonadal function and reproductive performance. This article establishes for the first time the inhibitory role of serotonin on reproduction in aging roosters.

Benzpyrene treatment in adulthood increases the testosterone level in neonatally steroid(allylestrenol)-treated male rats

1. Serum testosterone level was significantly elevated in adult male rats after a single perinatal allylestrenol administration. 2. Benzpyrene treatment of adult rats perinatally treated with allylestrenol, did not cause changes 1 week after benzpyrene treatment, but 3 weeks later an extremely high serum testosterone level was found. 3. In control animals benzpyrene administration in adulthood did not influence the serum testosterone level either 1 or 3 weeks following the treatment.

Research note: effect of in ovo 17-beta-estradiol or tamoxifen administration on sexual differentiation of the external genitalia

The effect of in ovo administration of tamoxifen or 17 beta-estradiol on external sexual dimorphism in chickens was investigated. In two trials, fertile eggs were injected with either tamoxifen (200 micrograms per egg) or vehicle (100 microL corn oil) on Day 1 of incubation, or with 17 beta-estradiol (20 micrograms per egg) or vehicle on Day 11 of incubation. Sexes were determined by visual inspection of the external genitalia and by gonadal identification at Day 1 posthatch. Tamoxifen injection resulted in a significantly greater number of phenotypic male identifications, with male:female ratios of 76:24 (Trial 1) and 62:38 (Trial 2) based on external genitalia phenotype. Gonadal sexing corrected these ratios to 46:54 and 44:56, resulting in genital sexing errors of 27% (Trial 1) and 18% (Trial 2). These errors were significantly higher than genital sexing errors of the chicks treated with vehicle (2 and .6% for Trials 1 and 2, respectively). In ovo administration of 17 beta-estradiol resulted in an increased number of female identifications based on genital sex determination, with male:female ratios of 37:63 (Trial 1) and 46:54 (Trial 2). Gonadal sexing corrected these ratios to 54:46 and 51:49, resulting in genital sexing errors of 10 and 6% for Trials 1 and 2, respectively. These errors were significantly higher than genital sexing errors of vehicle-treated chicks (4 and .9% for Trials 1 and 2, respectively). The results of the present study indicate that early embryonic administration of estrogen or an estrogen antagonist alters chicken external sexual dimorphism near the time of hatch.

Embryonic differentiation of sexual dimorphism in vasotocin and mesotocin levels in chickens

Chicken embryos of both sexes were injected on the tenth day of incubation with either estradiol benzoate (EB), aromatase inhibitor [1,4,6-androstatrien-3, 17-dione (ATD)], antiestrogen [tamoxifen (TAM)], antiandrogen [flutamide (FLU)], or the oil vehicle as control (C). At adulthood, at the age of 26 weeks, 10 chickens of each sex were killed and the amounts of immunoreactive arginine vasotocin (AVT) and mesotocin (MT) in the anterior hypothalamus (AHA), posterior hypothalamus (PHA), neurohypophysis (NHP), and pineal gland (PNL) were determined. Control hens had significantly more AVT in PNL and less MT in AHA and NHP than the corresponding roosters. This sexual dimorphism was affected by the embryonic treatments; TAM increased AVT in AHA of cockerels but not of hens. In both sexes, TAM and FLU increased AVT content in NYP. In males, but not in females, ATD also increased AVT content in the NHP. TAM and FLU administration to the female embryo reduced PNL AVT to the amount present in normal males. None of the treatments effected AHA MT in hens, while in cockerels TAM increased it. In females, TAM and FLU significantly increased NHP MT to the level of C males. In roosters, ATD, TAM, and FLU increased NHP MT further. In hens, but not roosters, FLU reduced MT in PNL. These results indicate that embryonic differentiation of the MT and AVT systems is affected by gonadal steroids in chickens.