Effect of Testosterone Administration and Spiking on Reproductive Success of Broiler Breeder Flocks

Determining the priority semen characteristics and appropriate age for genetic improvement in Thai native roosters

Semen characteristics are crucial indicators of reproductive success and directly influence the production efficiency of native chickens, which play a vital role in sustainable poultry production systems in Thailand. Key semen traits, including mass movement, semen pH, semen volume, sperm viability, sperm abnormalities, and sperm concentration, are routinely evaluated to assess the reproductive performance of Thai native grandparent roosters. Improved reproductive efficiency in these chickens can lead to increased fertility rates, better hatchability, and enhanced productivity, significantly benefiting smallholder farmers and the poultry industry. To enhance the accuracy and efficiency of evaluating the genetic potential of grandparent roosters, this study aimed to compare rooster age groups, estimate genetic parameters and breeding values, and develop an optimal selection index for semen traits. A total of 3,475 test-day records of six semen traits from Thai native grandparent roosters (Pradu Hang Dum), obtained from the Khon Kaen University native chicken experimental farm, were analyzed using a multi-trait animal model with average information restricted maximum likelihood (AI-REML). The heritability estimates for semen volume, mass movement, sperm concentration, sperm abnormalities, sperm viability, and semen pH across age groups were low, ranging from 0.128 to 0.161, 0.102 to 0.115, 0.101 to 0.111, 0.090 to 0.091, 0.067 to 0.083, and 0.043 to 0.057, respectively. Repeatability estimates ranged from low to moderate, between 0.119 and 0.384 for all traits and age groups. Genetic correlations among semen traits ranged from ‒0.332 to 0.580, ‒0.554 to 0.640, and ‒0.631 to 0.773 for rooster age Groups 1, 2, and 3, respectively. Based on heritability and genetic correlations, the three most important semen traits identified were semen volume, mass movement, and sperm concentration. The study revealed a strong relationship between rooster age and semen quality, with the highest selection index values observed in the youngest age group (32-52 weeks). This finding highlights the potential for genetic improvement by implementing a selective breeding program targeting the top 10% of young roosters based on the developed selection index. Such a strategy would significantly accelerate genetic progress in semen traits, improving reproductive efficiency and boosting the economic viability of native chicken production. Furthermore, these findings contribute to a deeper understanding of genetic evaluation in native chicken populations and can serve as a model for developing sustainable breeding programs for other poultry breeds under tropical conditions.

How concerned should we be about broiler breeder fertility declines?

Broiler breeder fertility is the bedrock on which modern broiler production rests. Over the last decade, fertility and hatchability issues have emerged as key topics of interest for both breeders and producers. In this study, we took an analytical approach to interrogate declining fertility trends among U.S. broiler breeders from 2013 to 2022, leveraging data from the USDA National Agricultural Statistics Service (NASS). Despite an increase in the number of eggs set and broilers raised to meet the rising demand for poultry, projections indicate that hatchability rates could decrease to approximately 60 % by 2050 without corrective action. Our Markov Chain Monte Carlo (MCMC) analysis reveals significant declines in essential production metrics, including hatchability, chick livability, and production efficiency. The analysis also includes 95 % credible intervals that confirm a persistent downward trend across these parameters. We developed the Broiler Breeder Performance Index (BBPI) to deepen our understanding of these trends, utilizing both Gaussian and Cauchy models to evaluate predictive performance. The BBPI projections suggest a decline below baseline values over time, underscoring the urgent need for interventions to counteract the fertility crisis in the broiler industry. Several factors contribute to this decline, including management practices and genetic selection strategies. Effective flock management techniques, such as sex-separate feeding and careful weight monitoring, are vital for improving reproductive viability among broiler breeders. Our findings highlight the necessity of addressing these fertility issues to ensure the long-term sustainability of U.S. poultry production. As the global demand for poultry meat grows, the poultry industry faces significant challenges in maintaining productivity. By pinpointing the causes of fertility decline and implementing effective management strategies, stakeholders can better navigate the complexities of poultry production and contribute to food security. This study aims to draw attention to the urgency of addressing broiler breeder fertility issues. It encourages further research into solutions that can enhance reproductive performance across various genetic stocks in the industry.

Recent strategies to mitigate reproductive aging in male broiler breeders: A review

The continued improvement of genetics, nutrition, and management has resulted in rapid growth, better feed efficiency, and higher meat yield with competitive prices in the broiler industry. Nowadays, however, it is well-documented that productive traits and fertility are negatively correlated, and male broiler breeders are exposed to a fertility decline after 45 wk of age. Considering a low male-to-female ratio in breeder flocks, roosters have a prominent impact on flock fertility. Consequently, strategies to maintain the fertility of male broiler breeders could guarantee the reproductive performance of commercial herds. Understanding reproductive aging demands deep insights into its molecular and physiological mechanisms. Over-weighting, Sertoli and Leydig cell dysfunctions, compromised antioxidant capacity, imbalance in sexual hormones, and epididymal lithiasis are among candidate culprits associated with reproductive aging in roosters. Nutritional and managing strategies have been successfully applied to modulate body weight, improve sperm fatty acid profile and antioxidant status, and boost spermatogenic and steroidogenic pathways. The current review characterizes the physiology and biochemistry of reproductive aging in male broiler breeders and then highlights strategies and their underlying mechanisms to mitigate this failure. In summary, applying one or more of the abovementioned strategies might result in consistent post-peak reproduction and benefit producers in the poultry industry.

Welfare of broilers on farm

This Scientific Opinion considers the welfare of domestic fowl (Gallus gallus) related to the production of meat (broilers) and includes the keeping of day-old chicks, broiler breeders, and broiler chickens. Currently used husbandry systems in the EU are described. Overall, 19 highly relevant welfare consequences (WCs) were identified based on severity, duration and frequency of occurrence: 'bone lesions', 'cold stress', 'gastro-enteric disorders', 'group stress', 'handling stress', 'heat stress', 'isolation stress', 'inability to perform comfort behaviour', 'inability to perform exploratory or foraging behaviour', 'inability to avoid unwanted sexual behaviour', 'locomotory disorders', 'prolonged hunger', 'prolonged thirst', 'predation stress', 'restriction of movement', 'resting problems', 'sensory under- and overstimulation', 'soft tissue and integument damage' and 'umbilical disorders'. These WCs and their animal-based measures (ABMs) that can identify them are described in detail. A variety of hazards related to the different husbandry systems were identified as well as ABMs for assessing the different WCs. Measures to prevent or correct the hazards and/or mitigate each of the WCs are listed. Recommendations are provided on quantitative or qualitative criteria to answer specific questions on the welfare of broilers and related to genetic selection, temperature, feed and water restriction, use of cages, light, air quality and mutilations in breeders such as beak trimming, de-toeing and comb dubbing. In addition, minimal requirements (e.g. stocking density, group size, nests, provision of litter, perches and platforms, drinkers and feeders, of covered veranda and outdoor range) for an enclosure for keeping broiler chickens (fast-growing, slower-growing and broiler breeders) are recommended. Finally, 'total mortality', 'wounds', 'carcass condemnation' and 'footpad dermatitis' are proposed as indicators for monitoring at slaughter the welfare of broilers on-farm.

Semen quality and sperm characteristics in broiler breeder cockerels fed vitamin E during hot season

Thirty-two Arbor Acres (AA) cockerels aged 27 weeks were used to determine the effect of vitamin E (VE) on the semen characteristics and sperm quality during hot season. The birds were fed diets containing 0, 50, 100 and 150mg VE kg-1 feed. There were 4 replicates and two birds per replicate. Semen collection was done thrice a week for three weeks in all birds. Dietary vitamin E significantly (p < 0.05) increased the semen volume (SV) and number of sperm cells (NS) in AA cockerels. CONTROL birds (0.71 mL) had lower SV than birds fed 150 mg VE (0.94 mL). Birds on 100 and 150 mg VE recorded similar NS, which was higher than 0 and 50 mg VE groups. The least NS was in the CONTROL group. Sperm abnormality gradually (p < 0.05) decreased as dietary VE increased from 0 to 150 mg. Significant (p < 0.01) effect of dietary VE was recorded in percentage live sperm (PLS). Semen from cockerels on VE treatment had higher PLS than the CONTROL. In conclusion, it may be beneficial to supplement the broiler breeder cockerel diet with VE up to 150 mg kg-1 feed during hot season as it increased SV, NS and PLS and decreased sperm abnormality.

Effect of orally administrated letrozole on reproduction performance and gene expression of FOXJ1, LPR2 and PVRL3 in reproductive tract in aged roosters

letrozole is an aromatase inhibitor that stops the production of estrogen through interrupting the entrance of hormone androgen into a small amount of estrogen. Therefore, the current study was developed to estimate orally administrated Letrozole on the reproductive performance and relative abundance of Foxj1, PVRL3, and LPR2 mRNA in aged roosters. Fifty-five-week old ROSS 308 breeder roosters (n = 18) were orally treated using letrozole. Primarily, the body weight of the animals was recorded, and they were randomly classified into three groups (n = 6 birds/group) receiving different doses of Letrozole, including 0, 0.015, and 0.03 mg/kg body weight/day for three weeks. At the end of the trial, seminal traits, plasma, testicular hormone levels (testosterone, estradiol, and FSH), histopathological studies, in vitro fertility, and relative abundance of testis PVRL3, epidydimal Foxj1, and LPR2 mRNA were evaluated. Based on the results, the sperm quality variables were statistically higher in the 0.03 group compared to the controls. Greater histologic parameters, such as diameter of seminiferous tubules, thickness of seminiferous epithelium, categorized epididymal region, and in vitro fertility rates were estimated for the treated groups(p < 0.001). Plasma and testicular testosterone, estradiol concentrations, and plasma FSH levels were significantly influenced by letrozll treatment (p < 0.001). Relative mRNA transcript abundance increased for PVRL3 and decreased for Foxj1 and LPR2 in treated groups. Overall, aromatase inhibitors can enhance the reproductive performance of aged commercial broiler breeder roosters. However, it can impact endocytosis and ciliogenesis events via reducing estradiol.

Letrozole, an aromatase inhibitor, reduces post-peak age-related regression of rooster reproductive performance

This study was designed to evaluate orally administrated Letrozole (Lz) on reproductive performance, plasma testosterone and estradiol concentrations and relative abundance of mRNA of GnRH, FSH and LH in roosters. Ross 308 roosters (n=32) that were 40-weeks of age were individually housed and received a basal standard diet supplemented different amounts of capsulated Lz [0 (Lz-0), 0.5 (Lz-0.5), 1 (Lz-1) or 1.5 (Lz-1.5), mg Lz/bird/day] for 12 weeks. Sperm quality variables and plasma testosterone and estradiol concentrations were assessed from the first to the tenth week of the treatment period. Semen samples from the 11th to 12th week were used for artificial insemination and eggs were collected and allotted to assess fertility and hatchability rates. Relative abundance of hypothalamic and pituitary GnRH, LH and FSH mRNA was evaluated at the end of 12th week. The results indicated that total and forward sperm motility as well as egg hatchability rate were greater in the Lz-0.5 group. Greater sperm concentrations, ejaculate volume, sperm plasma membrane integrity, testis index and fertility rates were recorded for both Lz-0.5 and Lz-1 groups compared with the Lz-0 group (P<0.05). Body weight, percentage of sperm abnormalities, and sperm plasma membrane functionality were not affected by treatment. Testosterone and estradiol concentrations were negatively related with greater testosterone concentrations in the Lz-1.5 group which had lesser estradiol concentrations. Relative mRNA transcript abundance for GnRH, LH and FSH was Lz dose responsive being greater in the treated groups; however, this trend plateaued for GnRH and for the relative abundance of both LH and FSH mRNA was less in the Lz-1.5 group than the other treatment groups. It is concluded that Lz may be an effective treatment to improve age related post-peak reproductive performance of roosters.