Effects of granular feed on reproductive metabolism of breeding pigeons, intestinal development and microbiota of squab pigeons-A double-edged sword.

Pigeons like to eat raw grains, but meat pigeon enterprises often use compound feeds instead of raw grains to feed breeding pigeons to increase economic efficiency, which may change the pigeon's dietary behavior, and consequently lead to health and welfare problems. The purpose of this study was to investigate the effect of granular feeds on the health of high-yielding breeding pigeons and squabs in lactation. The results showed that, compared with raw grain group, the provision of granular feed resulted in lower total feed intake without affecting the weight of lactating breeding pigeons. Meanwhile, reproductive metabolism was improved and no oxidative stress was observed, which indicated that granular feeds had a positive effect on breeding pigeon's health. However, granular feed adversely affected jejunum development in squabs, compare wtih raw grain group, the growth rate of squab was reduced. Sequencing of the 16 s rRNA gene revealed that granular feed induced intestinal microbiota dysbiosis in the squabs. The use of granular feed reduced the relative abundance of gut microorganisms in functional categories related to lipid and energy metabolism, resulting in a decrease in the relative abundance of beneficial bacteria such as Bifidobacterium, Ligilactobacillus, Atopobium, and an increase in that of inflammation-related Limosilactobacillus, which likely inhibited squab intestinal development and growth. Although the use of granular feed can improve breeder metabolism, it affect the composition of the microbial community and gut development of squabs. Therefore, the use of granular feed in production should be more careful to avoid causing growth obstruction of squab.

Transcriptomic Analysis on Pectoral Muscle of European Meat Pigeons and Shiqi Pigeons during Embryonic Development.

In avian muscle development, embryonic muscle development determines the number of myofibers after birth. Therefore, in this study, we investigated the phenotypic differences and the molecular mechanism of pectoral muscle development of the European meat pigeon Mimas strain (later called European meat pigeon) and Shiqi pigeon on embryonic day 6 (E6), day 10 (E10), day 14 (E14) and day 1 after birth (P1). The results showed that the myofiber density of the Shiqi pigeon was significantly higher than that of the European meat pigeon on E6, and myofibers with a diameter in the range of 50~100 µm of the Shiqi pigeon on P1 were significantly higher than those of European meat pigeon. A total of 204 differential expressed genes (DEGs) were obtained from RNA-seq analysis in comparison between pigeon breeds at the same stage. DEGs related to muscle development were found to significantly enrich the cellular amino acid catabolism, carboxylic acid catabolism, extracellular matrix receptor interaction, REDOX enzyme activity, calcium signaling pathway, ECM receptor interaction, PPAR signaling pathway and other pathways. Using Cytoscape software to create mutual mapping, we identified 33 candidate genes. RT-qPCR was performed to verify the 8 DEGs selected-DES, MYOD, MYF6, PTGS1, MYF5, MYH1, MSTN and PPARG-and the results were consistent with RNA-seq. This study provides basic data for revealing the distinct embryonic development mechanism of pectoral muscle between European meat pigeons and Shiqi pigeons.

Optimal dietary energy and protein levels for breeding pigeons in the winter "2 + 3" lactation pattern.

The nutritional requirements of breeding pigeons depend on their physiological period, breeding pattern, and environmental conditions. Despite works on reduced litter size in winter production to combat high mortality and the poor welfare of squabs, there are few studies on the related nutritional requirements of these pigeons. A total of 432 pairs of European Mimas pigeons were randomly divided into 9 groups in which 3 crude protein (CP) levels (15, 16.5, and 18%) and 3 metabolizable energy (ME) levels (12.2 MJ/kg, 12.4 MJ/kg, and 12.6 MJ/kg) were tested to determine the optimal energy and protein requirements of breeding pigeons in the winter "2 + 3" breeding pattern. The results showed that ME and CP levels had little effect on the body weight, feed intake, and egg quality of breeding pigeons during the lactation period. An 18% CP diet significantly increased the laying rate and hatchability (P < 0.05), but there was no difference in the laying rate with 18% CP and 16.5% CP during the whole reproductive cycle (P > 0.05). There was a significant interaction between ME and CP levels, and the laying interval of breeding pigeons in group 9 (18% CP; 12.6 MJ/kg) was significantly shortened (P < 0.05). For squabs, the ME level had no effect on growth performance, slaughter performance, or meat quality. The body weight of 21-day-old squabs in the 18% CP group increased by 3.16% compared with that of the 15% CP group, but there was no difference between the 18% CP and 16.5% CP groups. Compared with other experimental groups, group 7 (18% CP; 12.2 MJ/kg) had the fastest growth rate in squabs (P < 0.05), and the corresponding slaughter weight was also the heaviest (P < 0.05). We further found that the height of the squab intestinal epithelium was significantly increased in both the 16.5% CP and 18% CP groups of squabs (P < 0.01), but male breeding pigeons showed a certain degree of oxidative stress with an increase in CP level. In conclusion, the effects of 15 to 18% CP levels and 12.2 to 12.6 MJ/kg ME levels on the reproductive metabolism of breeding pigeons and the growth and development of squabs in the "2 + 3" breeding pattern during winter are small. For economic efficiency, we suggest that the CP level can be reduced to 16.5% while the ME level should not be less than 12.2 MJ/kg in practical production.

Effects of Astragalus, Epimedium, and Fructus Ligustri Lucidi extractive on antioxidant capacity, production performance, and immune mechanism of breeding pigeons under stress.

With the large-scale and intensive development of pigeon breeding industry and the improvement of production level, stress factors have an important impact on the immune, antioxidant capacity, and productivity of pigeons. In this study, the extenuating effect of Astragalus, Epimedium, and Ligustrum lucidum (AEF) on the antioxidant, production performance, and immune mechanism was investigated in breeding pigeons. Eighty pairs of 11-month-old healthy breeding pigeons with the same egg production batch were randomly divided into 4 groups: control group (C group), treated with AEF (AEF group), in restraint stress (S group) and treated with AEF and in restraint stress (S+AEF group). Results showed that AEF reduces weight loss during lactation and increases spleen weight, increased IgA, IgG, T4, GSH-Px, and SOD in serum and decreased T3 and MDA (P < 0.05). Furthermore, treatment with AEF declined HSP60, HSP70, HSP90, GR levels in liver and cFOS, GR mRNA levels in the Hypothalamus, GR mRNA levels in the pituitary (P < 0.05). Meanwhile, the results of the intestine studies showed that AEF promoted relative abundances of Firmicutes and relieve intestinal injury in the colon of pigeons. These results indicated AEF enhanced stress resistance, immunity, production performance and antioxidant capacity of pigeons.