A Study On The Expression Of Ovalbumin In The Oviduct Magnum Of Laying Hens

The experiments were conducted to study the effects of the rearing environment, management and crude protein(CP) level in the diet on the expression of ovalbumin in the oviduct which was related closely to egg weight. The purpose was to regulate egg weight to meet people’s needs. About the rearing environment and management, we detected the expression of ovalbumin in the oviduct of hens under the condition of different laying rate and egg weight, heat stress and forced molting. About the CP level, we reduced the crude protein level at the later and peak stage, then detected the expression of ovalbumin in the oviduct.In Experiment 1, we investigated the expression of ovalbumin in the oviduct of hens with different laying rates and different egg weights. Twenty Hy-line Brown layers were selected and assigned to four groups of 5 hens according to their laying rate(low and high) and egg weight(small and large): higher laying rate with large or small egg weight, and lower laying rate with large or small egg weight. The results showed that the four groups of hens had no difference in feed intake or serum levels of urate, glucose and 17-β-estradiol. The hens with high laying rate and small egg weight, however, had higher ovalbumin expression levels in the oviduct magnum compared to the other groups of hens.In Experiment 2, we investigated the effects of heat stress on the egg weight and the expression of ovalbumin in the oviduct of hens. Forty-five Hy-line Brown layers were divided into three groups of 15 hens and randomly subjected to three treatments: a group exposed to 32 oC for 10 days(heat stress), a pair-fed group and a control group. The results showed that feed intake and hen-day egg production were lower in the heat stressed hens, while the laying rate, egg weight and body weight were not significantly influenced by heat stress. The expression of ovalbumin in the oviduct magnum and the serum urate, glucose and 17-β-estradiol levels were not changed by heat exposure.In Experiment 3, we investigated the effects of forced molting on the egg weight and the expression of ovalbumin in oviduct of hens. Eighty 82-week-old Hy-line Brown layers were divided into four groups. The laying performance and the expression of ovalbumin in the oviduct magnum were determined before, during and post molting. The level of ovalbumin in the magnum was lower in the hens during molting compared to the hens before and post molting. In conclusion, the expression of ovalbumin in the oviduct magnum is associated with the reproductive status of hens. Additionally, serum estrogen level is not relevant to either the protein or mRNA expression levels of ovalbumin.In Experiment 4,we investigated the effects of CP level in diets at the later stage on the expression of ovalbumin in the oviduct. One hundred and sixty 70-week-old Hy-line Brown layers were divided into two groups: the control group and the low CP group. The CP level of the control group was 16.5%, while the CP level of the low CP group was 13%. To reduce the CP level, we decresed the soya bean meal rate in the diet and supplemented lysine, methionine, arginine, threonine, tryptophan, valine and isoleucine to normal level, and 0.25% glycine. The experiment proceeded for 8 weeks. The results showed that the reduced CP level resulted in the decline of egg weight and body weight, but did not influce the laying rate, egg mass and egg quality, except the increased egg yolk color. Serum urate, urea nitrogen and TOFAA were not changed by the low CP level. The expression of ovalbumin in oviduct was reduced by the low CP level.In Experiment 5, we investigated the effects of CP level in diets at the peak stage on the expression of ovalbumin in the oviduct. Four hundred and eighty 25-week-old Hy-line Brown layers were divided into four groups: the control group, low CP group, low CP+glycine group and low CP+alanine group. The CP level of the control group was 16.5%, while the CP level of the low CP group was 12.5%. To reduce the CP level, we decresed the soya bean meal rate in the diet and supplemented lysine, methionine, arginine, threonine, tryptophan, valine and isoleucine to normal level. The diet of the low CP+glycine group was the diet of the low CP group with supplyment of 0.25% glycine. The diet of the low CP+ alanine group was the diet of the low CP group with supplyment of 0.30% alanine, which equal the CP level of the diet of the low CP+ glycine group. The results showed that the reduced CP level resulted in the decline of egg weight, laying rate, egg mass, feed intake and body weight, but did not influce the egg quality, except the increased egg yolk color. The expression of ovalbumin in the oviduct was not influenced by the low CP level.In conclusion, the expression of ovalbumin in oviduct magnum is not relevant to the egg weight or laying perpormance closely, but is associated with the reproductive status of hens, and it might be regulated by the CP level of diets.