Effects of different stocking densities on the development of reproductive and immune functions in young breeder pigeons during the rearing period

ABSTRACT

1. Stocking density (SD) is closely related to animal performance. This experiment was designed to evaluate the development of reproductive and immune functions of young pigeons under different SDs.

2. A total of 288 (half male and half female) 40-day-old pigeons (body weight 400 ± 15 g) were allocated into four groups: High stocking density (HSD; 0.308 m³/bird), standard stocking density (SD; 0.616 m³/bird), and low stocking density (LSD; 1.232 m³/bird) and a caged (control; 0.04125 m³/bird). Every group had six replicates of the same sex.

3. The results showed that caged male pigeons had the highest testis index, testosterone content, and gene expression of the androgen receptor gene. LSD treatment induced the highest concentrations of oestradiol, progesterone and mRNA levels of reproductive hormone receptor genes in female pigeons. In male pigeons, the spleen index (organ weight calculated as a percentage of total body weight) showed a peak level (0.09 ± 0.020) in the LSD group, and the thymus index peaked (0.23 ± 0.039) in SD group. However, the index for ovary, spleen, thymus and bursa of Fabricius in female pigeons showed no significant changes among different groups.

4. The IL-1β, IL-8, IFN-γ, TGF-β and toll-like receptor 2 (TLR-2) mRNA levels reached their maximum values in both male and female pigeon spleens in the LSD group.

5. Young male pigeons housed in cages showed increased testicular development while low stocking density increased the development of reproductive function in young female pigeons. A larger activity space could help enhance the immune function of both male and female pigeons.

KEYWORDS:

• Immunity
• pigeons
• reproductive function
• stocking density
• hormones

Acknowledgments

The authors thank all the members in the school and institute for their generous technical advice. This research was supported by the Key RandD Plan Project of Huai’an City (Rural Revitalisation; HAN202203) and the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (23KJA23001).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Animal welfare statement

The authors confirm that the ethical policies of the journal, as noted on the journal’s author guidelines page, have been adhered to and the appropriate ethical review committee approval has been received. The authors confirm that they followed EU standards for the protection of animals used for scientific purposes.

Data availability statement

All data included in this study are available upon request by contact with the corresponding author.

Additional information

Funding

The work was supported by the Natural Science Foundation of the Jiangsu Higher Education Institutions of China [23KJA23001]; Key R&D Plan Project of Huai’an City (Rural Revitalisation) [HAN202203].