Spexin mRNA profile and its response to different photoperiods in Chinese Yangzhou geese (Anas cygnoides).

Spexin (SPX, NPQ), a novel neuropeptide composed of 14 amino acid residues, is evolutionarily conserved among different species. Spexin has been suggested to have pleiotropic functions in mammals. However, reports on spexin in birds are limited. To clarify the role of spexin in goose reproduction, the spexin gene was cloned and analyzed. Analysis of tissue distribution by RT-PCR showed that the expression of spexin and its two receptors was widespread. During the long photoperiod, the expression levels of spexin in the pituitary and hypothalamus and of GALR2/3 in the pituitary decreased, and the GnRH, LHß, and FSHß expression levels increased significantly. This suggests that a long photoperiod regulates reproductive activities by activating the gonadotrope-axis, which is modulated by decreased spexin levels.

Analyses of mathematical models for Yangzhou geese egg-laying curves.

Mathematical models of the egg-laying curves for Yangzhou geese exposed to both natural and artificial photoperiods were established to optimise the parameters for maximising geese reproductive performance and for the development of precision feeding methods. With the natural photoperiod, egg-laying starts in autumn when daily photoperiod decreases, but accelerates after the winter solstice, and reaches the peak in spring when photoperiod increases. An accumulating model was constructed based on the hypothesis that the egg-laying capacity of geese was determined by two components of the photoperiod: photo-stimulation and photo-inhibition. In addition, a second segmented model was constructed based on the hypothesis that the photo-stimulation only occurred with lengthening photoperiods after the winter solstice, and the lesser laying rate in autumn could be attributed to the non-photo-dependent animal-husbandry technologies. This model consists of a logistic model before the winter solstice, and an accumulating model after this solstice. The use of the logistic and accumulating resulted in more precise predictions that occurred with use of Model 1 with a greater R2 and lesser RMSE, AIC and BIC. Likewise, the egg-laying curves when there was consideration of artificial photoperiods could also be constructed with consideration of stimulatory and inhibitory photoperiodic effects. The model consists of an initial logistic and subsequently a quadratic polynomial model. With use of this model, there is consideration of changes in egg-laying patterns when there is a fixed photoperiod, with the model parameters reflecting the effects by photoperiod control-programs and age of the geese. In conclusion, new mathematical models have been developed to best fit egg-laying curves when there are both natural and artificial photoperiods. These models can contribute to development of precision-feeding technologies for breeding geese in future.

Induction of out-of-season egg laying by artificial photoperiod in Yangzhou geese and the associated endocrine and molecular regulation mechanisms.

This study was carried out to induce out-of-season breeding, in the summer, and to achieve high reproductive performance using artificial photoperiod manipulation in the long-day breeding Yangzhou goose. Young geese were subject to a two-phase short-to-long (group A) or a three-phase (long-short-long; group B) photoperiod program February through October. Egg-laying was induced to start similarly in both groups in May, increased to a peak level in July, and then decreased gradually through to October. The peak and post-peak laying rates were higher with the three-phase than with the two-phase program. Plasma progesterone concentrations changed similarly in the two groups, increasing from low levels during the pre-lay periods until the peak laying stage, then decreasing with decline in the egg-laying rate. Plasma T3 concentrations increased from the beginning of the experiment to form the first peak under a short photoperiod, declined to a trough at peak lay and then progressively increased to high levels towards the end of the experiment. Plasma T4 concentrations increased throughout the experiment, showing little response to changes in photoperiod. GnIH mRNA expression level in the hypothalamus steadily decreased from high levels under the short photoperiod to a nadir at peak of lay, but was abruptly up-regulated by over a thousand-fold thereafter. This mRNA expression pattern was also shared by GnIHR, VIPR, TRHR, TSH, and PRL genes in the pituitary gland, and to lesser extent, by GnRH, VIP, and TRH genes in the hypothalamus. Pituitary GnRHR mRNA expression levels changed in a similar manner to that of reproductive activities of geese in both groups. FSH beta subunits mRNA expression levels increased to high levels after day 11 of the long photoperiod, and were higher in group B than in group A at peak laying. LH beta gene expression level was similarly upregulated by photoperiod and was higher in group B than in group A when used the multivariable and two-way analyses of variance. Taken together, photoperiod, through regulation of expression of an array of genes in the hypothalamus and pituitary gland, synchronized stimulation and refractoriness of the reproductive system in Yangzhou geese. The higher out-of-season egg laying performance following the three-phase photo-program treatment was mediated by higher FSH beta and LH beta subunit mRNA expression levels.

[Construction, expression and purification of repeat fragment polymer of oInhibin alpha-subunit N terminal 1-33 fragment].

A cDNA sequence coding for ovine inhibin N terminal 1-33 AA residue fragment (INH) was inserted between BamHI\SacI sites in plasmid pRSET-A to generate plasmid pR-INH. By utilizing a pair of isocaudamer BamHI and Bgl II sites and another downstream Hind III site, following simple double digestions and combination ligation of the resultant products, 2 to 6-repeat INH genes were constructed respectively. Each plamids containing 3 to 6 repeated INH fragment genes, pR-3INH, pR-4INH, pR-5INH and pR-6INH, directed expression of the target proteins in E. coli. BL21 (DE3) under induction of ITPG, which respectively accounted for 6%, 6%, 7% and 8% of the total bacterial protein. The expressed target proteins were all in the form of inclusion bodies. The above results implied that utilization of isocaudamer restriction disgetion sites in expression plasmid is capable of rapidly and correctly constructing repeat fragment polymer of short peptides, which may become a new method in construction of high immunogenic recombinant vaccines of short peptides.