Effect of Changes in Photoperiods on Melatonin Expression and Gut Health Parameters in Laying Ducks.

We investigated the effect of photoperiod on ileal morphology, barrier function, short-chain fatty acid (SCFA) contents, microbial flora, melatonin expression, and synthesis in laying ducks. After adaption, a total of 180 Jinding laying ducks (252 days old) were randomly divided into three treatments, receiving 12L (hours of light):12D (hours of darkness), 16L:8D, or 20L:4D. Each treatment had six replicates with 10 birds each. The formal experiment lasted 58 days. Compared with 12L:12D, the significantly higher values of villus height and goblet cell percentage (GCP) were observed in 16L:8D treatment, accompanied with the higher mRNA relative expression of zonula occludens-1, zonula occludens-2, zonula occludens-3, claudin-1, occludin, and mucin 2 (P < 0.05). Besides, significantly higher values of acetate and propionate, butyrate and total SCFA concentrations were simultaneously observed in ileal chyme of 16L:8D treatment (P < 0.05). For the ileal microbial community, the results of principal coordinate analysis (PCoA) visually presented that three photoperiod groups were mainly scattered into three clusters, indicating that the microbiota composition in different photoperiod treatments were quite dissimilar. Lower values of Shannon indicators were observed in the 20L:4D treatment (P < 0.05), meaning that the microbiota α-diversity decreased in the 20-h photoperiod. The relative abundance of Actinobacteria, Fusobacteria, and Proteobacteria at phylum level and Fusobacterium, Clostridium_sensu_stricto_1, and Pectobacterium at genus level kept an appropriate balance in the 16L:8D photoperiod. Melatonin level in serum decreased with the increasing photoperiods at 6:00 and 12:00, which was consistent with melatonin receptor expressions in the hypothalamus and ileal tissue. Meanwhile, the adenosine 3',5'-cyclic phosphate (cAMP) contents were significantly downregulated in the pineal gland (P < 0.05), in response to the increase in photoperiod. In conclusion, an appropriate photoperiod could improve ileal morphology, barrier function, SCFA profile, and microbial flora, which may be attributed to the appropriate regulation of the circadian rhythm through melatonin as well as its receptor expression, and 16 h could be an adequate photoperiod for laying ducks.

Effect of photoperiod on eggshell quality and quality characteristics of tibia, femur, and ulna in laying ducks.

We investigated the effect of photoperiod on eggshell quality, bone quality characteristics and bone metabolism related enzymes and factors in laying ducks. After adaption, 300 Jinding laying ducks (252-day-old) were randomly divided into 5 treatments, receiving 12L (hours of light):12D (hours of darkness), 14L:10D, 16L:8D, 18L:6D or 20L:4D, respectively. Each group had 6 replicates of 10 birds each. The feeding experiment lasted 8 wk. Compared with 12L:12D, the higher values of eggshell breaking strength occurred in ≥18 h photoperiods at the end of 6 wk, and in ≥16 h photoperiods at the end of 4 wk, with the common highest values in 18 h photoperiod (P ˂ 0.05). Besides, 18L:6D had higher values of ultimate load Fu and cortical cross-sectional area A in tibia, femur, and ulna (P ˂ 0.05), compared with 12L:12D. The higher values of proximal bone mineral content (BMC; tibia), distal BMC (ulna), total Ca (tibia), and cortical volumetric bone mineral density (vBMC; tibia and ulna) were observed in 16L:8D and 18L:6D treatments (P ˂ 0.05). Meanwhile, 18 h photoperiod group had the higher proximal BMC (femur) and total Ca in ulna (P ˂ 0.05). In serum, compared with 12L:12D group, the higher ALP activity occurred in ≥16 h photoperiods (0:00 and 18:00), with the highest values in 18L:6D treatment (P ˂ 0.05); the higher values of TGF-ß (6:00) and OC (6:00 and 18:00) were simultaneously observed in 18 h photoperiod (P ˂ 0.05). Moreover, values of trACP activity, TNF-α and IL-6 contents decreased in ≥18 h photoperiods at 0:00 (P ˂ 0.05), compared with 12L:12D group. To sum up, an appropriate photoperiod could improve eggshell quality, bone strength and mineral content through increasing osteogenesis during the light time and decreasing resorption activity during the dark, and 18 h is an adequate photoperiod for the eggshell and bone quality of laying ducks.

Effects of photoperiod on performance, ovarian morphology, reproductive hormone level, and hormone receptor mRNA expression in laying ducks.

We investigated the effect of photoperiod on performance, ovarian morphology, reproductive hormones levels, and their receptors mRNA expressions in laying ducks. After adaption, 300 252-day-old Jinding laying ducks were randomly allocated to 5 groups, receiving 12L:12D, 14L:10D, 16L:8D, 18L:6D, or 20L:4D, respectively. Each treatment had 6 replicates of 10 birds each. The feeding trial lasted 8 wk. Egg production, egg mass, and ADFI increased linearly and quadratically with increasing photoperiods (P < 0.05), and the higher values of them occurred in photoperiods ≥ 16 h, compared with 12L:12D (P > 0.05). Initial and bare stroma weight increased quadratically, while total large white follicle (LWF) number and weight increased linearly and quadratically, with increasing photoperiods (P < 0.05). The higher values of them occurred in 16L:8D and 18L:6D treatments as well as the higher total LWF weight also occurred in 20L:4D, compared with 12L:12D (P > 0.05). Besides, 16.93 and 16.93 h were the optimal photoperiods for bare stroma (follicles ≥ 2 mm in diameter removed) weight and total LWF weight, respectively, calculated from reliable regression equations (R2 ≥ 0.5071). Compared with 12L:12D, the higher levels of estradiol, progesterone, follicle-stimulating hormone (FSH) as well as the higher expressions of estrogen, luteinizing hormone (LH) and progesterone receptors were observed in ≥16 h photoperiods (P < 0.05), while the higher LH level and FSH receptor expression only occurred in 16L:8D and 18L:6D (P < 0.05). In the hypothalamus, higher mRNA expression of gonadotropin-releasing hormone occurred in 16L:8D and 18L:6D groups (P < 0.05). Meanwhile, gonadotropin-inhibitory hormone and prolactin increased in 20-hour photoperiod (P < 0.05), and the latter may be due to theup-regulation of vasoactive intestinal peptide expression (P < 0.05). To sum up, an appropriate photoperiod could improve the performance and reproductive organ and ovarian follicles development through reproductive hormones and their receptors, and 16.56 to 10.93 h is an adequate photoperiod for laying ducks.

Effect of photoperiod on ovarian morphology, reproductive hormone secretion, and hormone receptor mRNA expression in layer ducks during the pullet phase.

We evaluated the effect of photoperiod on ovarian morphology, reproductive hormone secretion, and hormone receptor mRNA expression in layer ducks during the pullet phase. A total of 480 71-d-old Jinding layer ducks were randomly divided into 5 groups that received 6L (hours of light):18D (hours of darkness), 8L:16D, 10L:14D, 12L:12D, or 14L:10D, respectively. Each group had 6 replicates with 16 birds each. The photoperiod feeding trial lasted 80 d until 150 d of age. The age at first egg (AFE), the total number, and weight of eggs increased linearly with increasing photoperiods (P < 0.05); lower values of AFE occurred with photoperiods ≥8 h, whereas a higher total number and weight of eggs occurred with photoperiods ≥10 h, compared with 6L:18D (P > 0.05). Oviduct weight, ovary percentage, and initial and bare stroma (weight and percentage) increased quadratically with increasing photoperiods (P < 0.05), and 10.24, 10.01, and 10.10 h were the optimal photoperiods for oviduct weight, bare stroma (follicles ≥2 mm in diameter removed) weight, and bare stroma percentage, respectively, as calculated from reliable regression equations (R2 ≥ 0.5791). Compared with 6L:18D, 10L:14D had a higher total large white follicle weight, small yellow follicle number, and weight (P < 0.05). In addition, higher serum levels of follicle-stimulating hormone, luteinizing hormone, and progesterone were observed with ≥10-h photoperiods (P < 0.05), as were levels of hormone receptor mRNA expression in ovarian follicles (P < 0.05), with the highest values for both measures at 10L:14D. In the hypothalamus, mRNA expression of gonadotropin-releasing hormone increased in ≥8-h photoperiods, with the highest value at 10L:14D. In contrast, gonadotropin-inhibitory hormone increased in photoperiods ≥12 h (P < 0.05). In conclusion, an appropriate photoperiod led to early sexual maturity and improved the development of reproductive organs and ovarian follicles through effects on reproductive hormones and their receptors; 10 to 10.24 h is an adequate photoperiod for layer ducks during the pullet phase.

Effect of photoperiod on growth performance and quality characteristics of tibia and femur in layer ducks during the pullet phase.

This study aimed to evaluate the effect of photoperiod on growth performance and bone development in layer ducks during the pullet phase. A total of 480 11-wk-old Jinding layer ducks were randomly divided into 5 groups, receiving 6L (light): 18D (dark), 8L: 16D, 10L: 14D, 12L: 12D, 14L: 10D, respectively. Each group had 6 replicates of 16 birds each. The feeding trial lasted 80 d until 150 d of age. The results showed that 8L: 16D increased body weight (BW) and average daily gain (ADG; P < 0.05) compared with 6L:18D, whereas average daily feed intake, feed conversion ratio, and mortality rate had no difference among all treatments (P > 0.05). The midpoint perimeter (tibia and femur) and work to fracture (Wu; tibia) increased quadratically (P < 0.05), in response to photoperiod increment. Compared with 6L:18D, 8L:16D had higher tibia midpoint perimeter, ultimate load (Fu), and cortical cross-sectional area (P < 0.05), accompanied with higher content of total Ca, distal bone mineral content (BMC), and cortical volumetric BMC (vBMC; P < 0.05). A linear increase was observed in trabecular volumetric bone mineral density (vBMD) and vBMC (tibia and femur), elastic energy (femur), work to fracture Wu and young modulus of elasticity E (tibia) in response to photoperiod increase (P < 0.05), and treatment with 14L:10D had higher ultimate load Fu and total Ca of tibia (P < 0.05). Besides, estradiol and testosterone levels (serum), estrogen receptor gene mRNA expression (bone tissue), alkaline phosphatase and tartrate-resistant acid phosphatase activities, transforming growth factor-ß, osteocalcin and tumor necrosis factor-α contents increased in ≥12 h photoperiods (P < 0.05). In summary, appropriate photoperiod increased BW, ADG, cortical bone generation, and bone mineralization, whereas only medullary bone formation increased with photoperiods. These results suggest that 8L:16D could be an adequate photoperiod for layer ducks' growth and bone development during the pullet phase.

Effect of dietary supplementation with Moringa oleifera leaf on performance, meat quality, and oxidative stability of meat in broilers.

The objective of this study was to evaluate the effects of dietary supplementation with Moringa oleifera leaf (MOL) on performance, carcass characteristics, meat quality, and oxidative stability of breast muscle in broilers. A total of 720 1-d-old male Arbor Acres birds were randomly divided into 6 dietary groups, which were fed a basal diet supplemented with 0, 1, 2, 5, 10, and 15% MOL, respectively. Each group had 6 replicates of 20 birds each. The feeding trial lasted for 42 d. The results showed dietary MOL supplementation linearly and quadratically decreased body weight and average daily gain (P < 0.01), and increased feed conversion ratio (P < 0.001). Abdominal fat decreased linearly and quadratically in response to the supplementation of MOL in diets, both on d 21 and 42 (P < 0.001). In breast muscle, dietary supplementation with MOL quadratically increased the contents of C18:2, C18:3n-3, C20:4, polyunsaturated fatty acids (PUFA), n-3 PUFA, n-6 PUFA (P < 0.01), and decreased thrombogenic index (TI; P = 0.019). Dietary inclusion of MOL improved meat color, evidenced by quadratically reduced b* (yellowness) values (45 min postmortem, P = 0.001; 24 h postmortem, P = 0.018) and increased a* (redness) values (24 h postmortem, P < 0.001). Besides, diets supplemented with MOL quadratically decreased malondialdehyde (MDA) levels in breast muscle during storage (P < 0.001). Plasma total anti-oxidative capacity, total superoxide dismutase, glutathione peroxidase activities increased quadratically (P < 0.01), whereas MDA decreased quadratically (P < 0.001), in response to dietary MOL supplementation. In summary, MOL could be used as a feed ingredient for broilers to improve PUFA contents, oxidative stability, color of breast muscle, and abdominal fat without adverse effects on growth performance, with an inclusion of 1.56% in the diets.