The Effect Of Illumination Time At Growing Period On Laying Performance And Expression Levels Of Lepr And Tshβ Genes

Light is one of main determinant factor of reproduction in pullet. Leptin receptor (LEPR) and thyroid stimulating hormone (TSH) play important roles in development of follicle, laying and photoperiod signal transduce, both leptin and thyroid hormones related to regulate energy balance and seasonal reproduction, the possible pathways of lighting effects on chicken reproduction performance were hypothalamo-pituitary-gonadal axis, which involves leptin binding leptin receptor (LEPR) regulated sexual hormones-FSH and LH secretion hypothalamo-pituitary-thyroid axis, which involves thyroid-stimulating hormones (Tsh) retrograde regulated Dio2/Dio3, then effected T3 secretion. In this study, the experimental materials were high quality chicken BH02 and Luhua laying hens. Using different light regime, we measured the influence of illumination time on production performance, content of related hormones and laying performance in two colonies. At the same time, we quantified Lepr, Mc4r, Tshβ, Dio2 and Dio3, which involves seasonal reproduction, to research the molecular basis of light application influence high quality chicken reproduction performance. The results as follows:The result of growth and development showed that illumination time at growing perriod have not significant effect on body weight after 4 weeks of light treatment, a significant effect on body weight of LHc from 5 week on, G2(10 h) and G3(12 h) have the same body weight and heavier than G1 (8 h) (P< 0.05); illumination time at growing perriod have no effect on growth performance in BH02 (P> 0.05). The results showed LHc is more sensitive to light application than BH02.The laying performance result showed that illumination time at growing perriod have significant effect on AFE of LHc and BH02, the AFE of G3(12 h) is earlier than G2(10 h), earlier than Gl(8 h) (P< 0.05). Both BWFE and WFE of LHc and BH02 are not influenced by illumination time (P> 0.05). Illumination time at growing perriod has effect on EWTA of LHc and BH02 (P< 0.05), G1 (8 h) is lighter than G2 (10 h) and G3 (12 h) in LHc; G1 (8 h) is heavier than G2 (10 h) and G3 (12 h) in BH02; Illumination time at growing perriod has no difference on BWTA (P> 0.05).The result of egg quality test showed that egg weight, albumen height and shell thickness are influenced by illumination time at growing perriod (P<0.05), egg weight of d300, G3 (12 h) is heavier than other two groups (P<0.05); egg weight, albumen height and shell thickness at 300 days of age, G1 (8h) are better than G2 (10 h) and G3 (12 h) (P<0.05) and the top egg quality in BH02.The result of related hormones contents showed, the time point of plasma leptin concentration of LHc and BH02 are influenced by illumination time at growing perriod is a week in advance, compared with plasma LH and FSH concentration. The result showed that illumination changed breed related hormones by changing body weight.The result of quantified related reproduction genes of LHc showed that illumination time at growing perriod have an effect on hypothalamus Lepr mRNA level of LHc at d 126 and d 137, and Lepr mRNA level was down regulated by long illumination, hypothalamus Lepr mRNA level of G3 (12 h) lower than G1 (8 h) (P<0.05). Hypothalamus Lepr mRNA level of BH02 are influenced by illumination at d 139, hypothalamus Lepr mRNA level of G3 (12 h) lower than G1 (8 h) (P<0.05), and not influenced by illumination at d 126. The MC4R expression patterns of LHc and BH02 were similar to their Lepr expression patterns, the action of Lepr is by regulating MC4R. Pituitary Tsh β mRNA levels and DIO2 mRNA levels were upregulated by long illumination at d 126, were unregulated at d 137 and d 139. Tsh P mRNA levels and DIO2 mRNA levels are influenced by illumination and changing of light time. Hypothalamus DIO3 mRNA levels were down regulated at long illumination.This study presented the difference of the effects of illumination time at growing period in LHc and BH02, on laying performance, plasma hormones levels and related reproduction genes expression levels, to make an optimum illumination time of BH02 at growing period, at the same time, lay the basis of molecular mechanism research of BH02.