Active immunization of broiler breeder hens with a recombinant chicken inhibin fusion protein enhances egg lay

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.

Effect of active immunization with recombinant-derived goose INH-α, AMH, and PRL fusion protein on broodiness onset and egg production in geese (Anser cygnoides)

This study was conducted to investigate the potential effects of active immunization against recombinant-derived goose inhibin-α (INH-α), anti-Müllerian hormone (AMH), and prolactin (PRL) fusion protein on broodiness onset and egg production in geese. The purified fusion proteins (INH-α, AMH, and PRL) were prepared using a prokaryotic expression system. Female Zhedong geese (10 mo old) were randomly assigned to one of 4 treatments and raised in separate pens. The geese were actively immunized with the recombinant goose INH-α, AMH, or PRL, respectively, and phosphate-buffered saline as control. The results showed the corresponding antibodies were produced when the geese were immune INH-α, AMH-, and PRL-recombinant proteins. The significantly higher luteinizing hormone contents were observed in the INH-α, AMH, and PRL recombinant protein-immunized geese, while the lower AMH hormone content only in PRL-immunized birds. AMH recombinant protein immunized geese had more large yellow follicles of ovary, while the INHα-treated birds with more other follicles compared with control geese. In addition, the geese receiving INH-α recombinant protein, the broodiness onset was about 6 d, which significantly shorter than did PBS immunization (16 d). The INHα- and PRL-immunization also resulted in 12.5 and 8.5 d shorter broody duration intervals compared to the control birds. Moreover, the lower new broodiness rate was observed in three recombinant proteins treated birds. Finally, the PRL recombinant protein-immunization resulted in an average increase of 1.34 eggs during a 40-d observation. Collectively, the data demonstrated that active immunization against recombinant proteins INH-α or AMH could promote LH hormone secretion, regulate follicle development and decrease the broodiness rate. Also, active immunization with a recombinant-derived goose PRL protein might improve egg laying performance.

Trends in recombinant protein use in animal production

Recombinant technologies have made possible the production of a broad catalogue of proteins of interest, including those used for animal production. The most widely studied proteins for the animal sector are those with an important role in reproduction, feed efficiency, and health. Nowadays, mammalian cells and fungi are the preferred choice for recombinant production of hormones for reproductive purposes and fibrolytic enzymes to enhance animal performance, respectively. However, the development of low-cost products is a priority, particularly in livestock. The study of cell factories such as yeast and bacteria has notably increased in the last decades to make the new developed reproductive hormones and fibrolytic enzymes a real alternative to the marketed ones. Important efforts have also been invested to developing new recombinant strategies for prevention and therapy, including passive immunization and modulation of the immune system. This offers the possibility to reduce the use of antibiotics by controlling physiological processes and improve the efficacy of preventing infections. Thus, nowadays different recombinant fibrolytic enzymes, hormones, and therapeutic molecules with optimized properties have been successfully produced through cost-effective processes using microbial cell factories. However, despite the important achievements for reducing protein production expenses, alternative strategies to further reduce these costs are still required. In this context, it is necessary to make a giant leap towards the use of novel strategies, such as nanotechnology, that combined with recombinant technology would make recombinant molecules affordable for animal industry.

Current and future reproductive technologies for avian species

The global demand for poultry meat and eggs is expected to increase exponentially in the next several decades. Increasing global poultry production in the future would require significant improvements in genetics, nutrition, and managerial practices including reproduction. This chapter summarizes some of the recent developments in ameliorating reproductive dysfunction in broiler breeder chickens, cryopreservation of avian spermatozoa, sex selection, and avian transgenesis.

Effect of a DNA vaccine harboring two copies of inhibin α (1-32) fragments on immune response, hormone concentrations and reproductive performance in rats

The objective was to investigate the effects of a novel DNA vaccine (pcISI) harboring two copies of inhibin α (1-32) fragments on immune response, hormone concentrations and reproductive performance in rats. Female Wistar rats (n=18 per group) were immunized (twice, 4 wk apart) with 10, 50, or 100 μg (T1, T2 and T3, respectively), of the pcISI plasmid. At 4 wk after the second immunization, plasma antibody titers were higher (P<0.05) in T3 than in either T1 or T2 (0.341±0.123, 0.236±0.068, and 0.251±0.077, respectively, mean±SD). Concurrrently, plasma concentrations of FSH and estradiol were highest (P<0.05) in T3, and were higher (P<0.05) in T1 and T2 than in control groups. For antibody-positive rats, there was a correlation (P<0.01) between antibody titer and FSH concentrations after two pcISI immunizations. The number of mature follicles in the T3 group (46.00±4.65) was higher (P<0.05) than in two control groups (29.25±3.72 and 27.92±3.48), and also higher (P<0.05) than in T1 and T2 (37.17±4.99 and 38.75±7.09). Antibody-positive rats had more mature ovarian follicles than negative rats (46.75±4.23 vs. 35.60±3.38, P<0.05). Moreover, litter size and number of placentas were increased (P<0.05) in the pcISI immunization groups, except for the T1 group, compared to the control groups. In conclusion, the pcISI DNA vaccine successfully induced a humoral immune response, improved reproductive hormone concentrations, stimulated follicular development, and increased number of placentas and litter size. Furthermore, 100 μg yielded the best immune response.

Phylogenomic analyses reveal the evolutionary origin of the inhibin alpha-subunit, a unique TGFbeta superfamily antagonist

Transforming growth factor-beta (TGFβ) homologues form a diverse superfamily that arose early in animal evolution and control cellular function through membrane-spanning, conserved serine-threonine kinases (RII and RI receptors). Activin and inhibin are related dimers within the TGFβ superfamily that share a common β-subunit. The evolution of the inhibin α-subunit created the only antagonist within the TGFβ superfamily and the only member known to act as an endocrine hormone. This hormone introduced a new level of complexity and control to vertebrate reproductive function. The novel functions of the inhibin α-subunit appear to reflect specific insertion-deletion changes within the inhibin β-subunit that occurred during evolution. Using phylogenomic analysis, we correlated specific insertions with the acquisition of distinct functions that underlie the phenotypic complexity of vertebrate reproductive processes. This phylogenomic approach presents a new way of understanding the structure-function relationships between inhibin, activin, and the larger TGFβ superfamily.

Intra-ovarian growth factors regulating ovarian function in avian species: a review

There is now overwhelming evidence that the avian ovary is a site of production and action of several growth factors that have also been implicated in the functioning of the mammalian ovary. Several members of the Insulin-like growth factor family (IGF), the Epidermal growth factor family (EGF), the Transforming growth factor-beta family (TGF-beta), Fibroblast growth factors (FGF), the Tumour necrosis factor-alpha (TNF-alpha), and others, have been identified either in the granulosa and/or theca compartments of ovarian follicles and in the embryonic and juvenile ovary. Some have been specifically localized to the germinal disc area containing the oocyte. The mRNAs and proteins of the growth factors, receptor proteins and binding proteins of some of the members of each group have been reported in the chicken, turkey, quail and duck. The intra-ovarian roles reported for the different growth factors include regulation of cell proliferation, steroidogenesis, follicle selection, modulation of gonadotrophin action, control of ovulation rate, cell differentiation, production of growth factors, etc. The aim of this paper is to provide a review of the current knowledge of avian ovarian growth factors and their biological activity in the ovary. The review covers the detection of the growth factor proteins, the receptor proteins, binding proteins, their spatial and temporal distribution in embryonic, juvenile and adult ovaries and their regulation. The paper also discusses their roles in each follicular compartment during follicular development. Greater emphasis is given to the major growth factors that have been studied to greater detail and others are discussed very briefly.

Active immunization of broiler breeder cockerels against chicken inhibin accelerates puberty and prevents age-induced testicular involution

Injection of quail and breeder hens with a recombinant protein antigen (MBP-cINA521)--a fusion of the bacterical maltose-binding protein (MBP) and a fragment of the alpha-subunit of chicken inhibin (cINA521)--accelerates puberty and enhances lay. Herein, the effects of this immunogen on reproductive responses in broiler breeder males were assessed. Cockerels were subcutaneously injected with 0 (vehicular controls), 1, 3, or 5 mg of MBP-cINA521 at 13 wk of age and with one-half of these dosages (boosters) at 18 wk. Bird subsamples were weighed, blood sampled, and killed at 24, 28, and 39 wk of age to assess age and vaccination effects on BW, testes weight (TWT), TWT relative to BW (RTWT), TWT > or = 20 g (TWT20; theoretical threshold TWT for maximum fertility), and plasma testosterone. Breeder males are sexually developing, reach peak sexual activity, and show age-related reproductive decline at these ages. Because vaccine gonadal effects at 24 wk appeared to be dramatic, the size of the left testis was also scored to see if size differences could be detected by mere visual inspection. Male fighting increasingly reduced sample sizes beyond 24 wk. Because mortality was unrelated to the treatments and to insure meaningful statistical comparisons, MBP-cINA521 data were pooled. Body weight (P < 0.04), testis score (P < 0.02), TWT (P < 0.03), RTWT (P = 0.06), and plasma testosterone (P = 0.08) were elevated in immunogen-treated males at 24 wk of age, and more (P < 0.05) MBP-cINA521-treated birds than controls achieved a TWT20 at this time. These variables did not differ by treatment at 28 wk. However, by 39 wk, treatment effects reemerged as follows: TWT (P < 0.04), RTWT (P = 0.06), and TWT20 (P < 0.01) were increased in vaccinated males who also showed nearly 3-fold higher levels of plasma testosterone. We conclude that immunoneutralization of inhibin accelerates puberty and retards age-related sexual senescence that typically occurs in broiler breeder males.