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

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.

Effects of different stocking densities on organ development, blood biochemical indices, and antioxidative status of breeder pigeons during the rearing period

The present experiment was conducted to investigate the effect of different stocking densities on the organ development, blood biochemical indices, and antioxidative status of breeder pigeons during the rearing period. A total of 280 (half male and half female) 40-day-old young pigeons were allocated into 4 groups, including 3 experimental groups (in compartments of the flying room): the 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). The results showed that the contents of corticosterone and heat shock protein 70 in males and the corticosterone content in females were higher in the control than in the other groups. The relative weight of liver, lung, and gizzard in males of the HSD group was the highest among the 4 treatments, whereas the abdominal fat index in the control group was higher than those in the other 3 treatments. Body weight and the relative weight of liver and abdominal fat in female pigeons in HSD group increased significantly. The levels of serum urea nitrogen and uric acid in pigeons of LSD group increased significantly, while the concentration of total cholesterol and the activity of alanine aminotransferase were higher in the control group. Ion (K+, Ca2+, and Na+) concentrations in female pigeon serum were also elevated in the control. The activity of antioxidant enzymes, including the total antioxidant capacity, superoxide dismutase, and glutathione peroxidase in pigeon breast muscle and liver had different degrees of inhibition when the space room was crowded. Moreover, the level of malondialdehyde in the liver of male caged pigeons was higher than that in the other treatments. In summary, rearing in cages or at a high density caused stress responses in the breeder pigeons. The stocking density of breeder pigeons during the rearing period should be ranged from 0.616 m3/bird to 1.232 m3/bird.

Effects of stocking density on ovarian development and maturation during the rearing period in Shan-ma ducks

Stocking density critically affects the growth and subsequent performance of animals in modern poultry production. This study investigated the effects of stocking density on ovarian development, ovarian maturation, and the mRNA expression of key genes in the reproductive axis during the rearing period of Shan-ma ducks. The experiments involved 180 healthy 7-wk-old Shan-ma ducks and randomly divided into low stocking density (LSD; n = 30, density = 5 birds/m²), medium stocking density (MSD; n = 60, density = 10 birds/m²) and high stocking density groups (HSD; n = 90, density = 15 birds/m²), for rearing. After examining ovarian development and measuring hormone levels in the plasma and expression levels of key regulatory genes in the reproductive axis at 19 wk of rearing, analysis of the gonad index analysis, reflecting stocking density, uncovered statistically significant differences. The gonad index of the LSD group was significantly higher than those of the MSD and HSD groups (P < 0.01), while no significant difference was observed between the MSD and HSD groups. pre-ovulatory follicles (POFs) and small yellow follicles (SYFs) development was only apparent in the LSD group, with the large white follicles (LWFs) number of this group being significantly higher than that of the MSD group (P < 0.05). The blood levels of E2 (estradiol), P4 (progesterone), and T (testosterone) were significantly higher in the LSD group than in the MSD and HSD groups (P < 0.05 or 0.01). Also, the levels of both P4 and T were significantly higher in the MSD group than in the HSD group (P < 0.01). The gene expression levels of GnRHR, FSH, AMHR, and FSHR were significantly increased in the LSD group compared to the MSD and HSD groups (P < 0.05 or 0.01), while the expression levels of GnIHR and GDF9 were significantly decreased in the LSD and MSD groups compared to the HSD group (P < 0.05 or 0.01). Steroid biosynthesis pathway genes such as StAR, CYP11A1, 3β-HSD, CYP19A1, and BMP15 were significantly downregulated at greater stocking densities (P < 0.05 or 0.01). Likewise, the protein expression of StAR, 3β-HSD, and CYP19A1 was also significantly decreased (P < 0.05 or 0.01). These results demonstrate that both medium and high stocking densities suppressed the expression of the key reproduction-promoting factors, while the expression level of the key reproductive inhibitory factors was enhanced. Therefore, rates of ovarian development and maturation could be reduced by a high stocking density leading to a delay in reproduction performance during the rearing period of Shan-ma ducks.

Stocking density: a clue for improving social behavior, welfare, health indices along with productivity performances of quail (Coturnix coturnix)-a review

The quail populations are considered to be one of the largest among the poultry species. Although quail egg and meat production are growing rapidly, still, quail farming practices and welfare aspects are not well established. Stocking density is one of the factors that can significantly affect the welfare, health, and performance of birds, but according to The Expert Group for Technical Advice on Organic Production, no allowed space standards have been reported for new hybrids and different breeds of quail. This review presents an overview of 1) the benefits of egg and meat of quail, 2) the global market of quail products, 3) the factors affecting the stocking density rate, and 4) the effects of stocking density rates and housing systems on the social behavior, welfare, physiological indices, and performance parameters of broiler and laying quail. Conclusively, larger space and enriched aviaries reduce aggressive behavior, and improve the quail welfare and immunological indices. However, the effect of stocking density on some blood biochemical indices and growth performance parameters showed mixed results. A better understanding of the relationship between housing, health, growth performance, and welfare aspects would assist in the implementation of welfare-economic standards for quail production. According to available data, stocking density ranges for broiler and laying Japanese quail are suggested; however, these stocking rates should be tested under different conditions.

Lead exposure induced inflammation in bursa of Fabricius of Japanese quail (C. japonica) via NF-κB pathway activation and Wnt/β-catenin signaling inhibition

Bursa of Fabricius (BF), one of primary lymphoid organ, is unique to birds. Meanwhile, lead (Pb) is well known for its high toxicology to birds. Therefore, this study aimed to examine the chronic toxic effects of lead exposure on BF in Japanese quails (C. japonica) and the underlying mechanism of lead immunotoxicity. One-week old male quails were exposed to 0 ppm, 50 ppm, 500 ppm and 1000 ppm Pb concentrations by drinking water for four weeks. The results showed that Pb accumulation in BF increased in a dose dependent way. The growth and development of BF was retarded in 500 ppm and 1000 ppm Pb groups. The number of lymphocytes was decreased and the release of immunoglobulin G and M (IgG, IgM), complement 3 and 4 (C3, C4) was inhibited by Pb exposure. Lead exposure also caused oxidative stress and increasing apoptosis in BF. Moreover, histopathological damages characterized by inflammatory hyperemia and inflammatory cell infiltration and ultrastructural injury featured by mitochondrial vacuole, cristae fracture and chromatin concentration were found in BF of 500 ppm and 1000 ppm Pb groups. Furthermore, RNA sequencing based transcriptomic analysis revealed that molecular signaling and functional pathways in BF were disrupted by lead exposure. In addition, the activation of Nuclear Factor kappa B (NF-κB) pathway while the inhibition of wingless integrated/catenin beta 1 (Wnt/β-catenin) signaling by Pb exposure were confirmed by quantitative real-time PCR (qPCR). Our study may benefit to understand potential mechanistic pathways of developmental immunotoxicology under Pb stress.

Japanese quail classified by their permanence in proximity to a high or low density of conspecifics: a search for underpinning variables

Test of sociality in poultry is mainly based on the bird's individual ability to make quick social discriminations. In recent years, a density-related permanence (DRP) test has been developed that enables us to classify young birds (while in groups) according to their individual permanence in proximity to either a high or low density of conspecifics (HD or LD, respectively). Thus, the result of the classification depends not only on the bird's individual response but also on the outcome of the social interactions within the whole group. The birds' performance in DRP was associated with underlying differences in social responses of their individuals. Quails in homogeneous groups of LD residents responded with less compact groups and higher levels of agonistic interactions to the presence of an intruder and showed higher levels of agonistic interactions among cage-mates than the homogeneous groups of HD birds. An acute stressor also induced a higher corticosterone response in the LD birds than in their HD counterparts. The present study addressed the question of whether contrasting DRP performance by Japanese quail can also reflect underlying differences in fearfulness and social reinstatement responses. Thus, LD and HD categorized juvenile birds underwent one of the following tests: tonic immobility (TI), open-field (OF), or a one-way runway. Results showed that HD birds required more inductions and developed shorter responses (P ≤ 0.05) in the TI test and walked more, faster, and greater distances in the OF (P ≤ 0.05) than their LD counterparts. No differences between groups were found in short social reinstatement responses. The present findings suggest that underlying fearfulness is lower in the HD than in the LD birds. A reduced fearfulness could be regarded as an additional favorable trait of the HD-classified quail to cope with environmental challenging situations.

Impact of temperature-humidity index on egg-laying characteristics and related stress and immunity parameters of Japanese quails

The aim of this study was to investigate the effect of temperature-humidity index (THI) level on productive parameters, welfare, and immunity in Japanese quails. One hundred and eighty (180) birds of Japanese quail, 14 weeks old, were used. Birds were divided randomly into three equal groups, control (at low THI, less than 70), H1 (at moderate THI, 70-75), and H2 (at high THI, 76-80). Birds in the control group had higher body weight (281.2 g, p = 0.001), egg mass (745 g, p = 0.001), fertility (85.4 %, p = 0.039), hatchability (80.4 %, p = 0.001), and immune response titer to Newcastle disease virus (p = 0.031), compared with H2 group. Furthermore, the thermoneutral group had higher internal egg quality score [albumen height (5.14 mm, p = 0.001), yolk height (10.88 mm, p = 0.015), yolk index (42.32 %, p = 0.039), and Haugh unit (92.67, p = 0.001)]. Nevertheless, there were no significant differences in fertility percentage, immune response, and corticosterone concentration between control and H1 group. Birds in the H2 group had the lowest total leucocytic count and lymphocyte percentage (p = 0.001 and 0.020, respectively) but the highest H/L ratio (0.83, p = 0.001). Corticosterone concentration was lower in control and H1 groups (5.49 and 6.41 ng/mL, respectively, p = 0.024) than that in H2 group. Japanese quail exposed to heat stress revealed drop in production and immunological parameters, as well as a detrimental effects on welfare. Thus, practical approaches might be used to reduce the detrimental effects of greater THI level.