Protein improves health and performance of molted layers

The poultry sector is among the largest and still growing industries of Pakistan. According to the economic survey of Pakistan (2008-09) the total population of birds increased to 1,061 million in 2008-09, from 895 million in 2006-07, with the total including 28.42 million layers. The total egg production was 10,197 million in 2006-07 and in 2008-09 it was reported to be 11,258 million, similarly total poultry meat production also increased from the previous years which was 651 thousand tonnes in 2008-09.

Yet the maximum production potential of our commercial layer could be further explored and in this regard technical know how and skills should be assessed and summarised to make more comprehensive future recommendations. In the process of the production cycle as the layers get older, their egg production and egg external quality decreases. Forced/induced molting is still a common practice all over the world to restore their reproductive system capacity, and promote a new laying cycle.

Induced molting
In the avian species the phenomenon of self molting is a natural thing in which the bird may lose up to 50 % of their body weight after a phase of fasting. The concept of this natural molt was brought into the practice of artificially induced molting in the commercial layer industry, which is used to rejuvenate and boost the reproductive tract for the beginning of next production cycle. Among the different molting techniques the generally in practice method for the induction of molt is feed withdrawal.

Dietary zinc has also been used by many researchers to induce the molt and it has been proved to be a better inducer of molt as compared to other molting techniques. A previous study of our lab proved the efficiency of zinc induced molting over fast induced molting regarding the immune status and dynamics of pituitary hormone producing cells. Based on this study and other literature reports, zinc induced molting was selected in the current study to induce the molt in white leg horn birds at the end of their first production cycle.

Efficacy of supplementation
There were some studies in literature regarding the supplementation in the diet of molted layers to get early recovery from the molting stress, better production performance and health status which is now a growing field of interest. The current study was designed in this context to seek beneficial impact of supplementation (protein, symbiotic and probiotic) in the improvement of post molt production performance and health status of the layers. Some researchers have reported the positive effect of supplementation with protein and follicle stimulating hormones in molted nera black hens regarding the early recovery from the post molt stress and better performance.

The most common non pathogenic habitant microorganisms of the intestine like Lactobacilli and Bifidobacterium are more sensitive to the stress. The process of induced molting is also a type of stress in which these microorganisms were most commonly compensated in birds. So the supplementation of these probiotic microbes in the post molt rest phase can augment the efficacy of induced molting. Probiotics (meaning ‘‘for life’’) are defined as microbial cell preparations commonly having Lactobacilli, Bifidobacterium and yeast that have a beneficial effect on the health and wellbeing of the host. Moreover the use of microbial cell preparations in replacing the antibiotics is also a better substitution after the emerging issue of antibiotic resistance.

The supplementation with 2% extra crude protein (CP 18% rather 16%), probiotic (Protexin) and symbiotic (Perfectin) in the molted layers was thus experimented in the current study. A non supplemented, receiving CP 16% diet group of molted birds was also studied parallel as control group to compare the efficacy of supplementation. The study was novel in an aspect as there were no reports in literature available regarding the efficacy of these supplementations on the biological health markers, serum biochemistry, immune status and production performance (egg production and quality) of molted layers.

Biological health markers
The enhanced generations of reactive oxygen species and the reduced defences by low production of endogenous antioxidants/decreased intake in the diet are some common factors towards the development of oxidative stress. The study of oxidative health markers and related enzymes in response to these supplementation programmes will be of prime importance.

The supplementation in the current study did show a significant response in decreasing the total oxidant status and homocysteine level alongside increasing the total antioxidant capacity of the body in molted birds. The improvement in the total antioxidant capacity was seen due to the increase in antioxidant related enzymes (Paraoxonase, Arylesterase and ceruloplasmin) activity. This positive response was more prominent in the protein supplemented group.

Hormonal profile
Despite the increase in the triglyceride concentration in the supplemented groups, significantly improved level of HDL cholesterol along with a decrease in the LDL cholesterol and total cholesterol after supplementation is depicting the healthy sign of supplementation, specifically with the probiotic supplementation. The triiodothyronine (T3; metabolic hormone) concentration was significantly improved in all the supplemented groups, which could be attributed to the enhanced metabolism after the supplementation.

The increase in the circulatory cortisol after the fast induced molting in layers was reported. They referred it to the impact of stress conferred by the fasting, used to induce the molt. The reduction in the cortisol level in all the supplemented groups after molting is indicating the better relief from stress in these groups as compared to the control.

Supplementation and immune status
In the humoral immunity the NDV geometric mean titer (GMT) was found to be high in all the supplemented groups. The EDS GMT was high in the protein supplemented group throughout the study period, however at the end of production it was high in all the supplemented groups as compared to control group. To assess the delayed type of hypersensitivity response DNCB assay was conducted and response found significantly increased in the probiotic supplemented group after 72 hours of DNCB inoculation.

The nitric oxide (NO) production by the in vitro cultured macrophages from the birds was assessed to calculate the cell mediated immune response. No production was found significantly enhanced in the probiotic and symbiotic supplemented birds depicting the improvement in the cell mediated immune response in these groups.

Egg production and quality
The supplementation did show a significant response in improving the egg production as well as egg quality. The egg production was increased and more stable in all the supplemented groups as compared to control group. However it was remarkable in the protein supplemented group. In terms of egg quality egg weight, egg diameter, albumin diameter, egg shell thickness, egg breaking strength and FCR were improved in all the supplemented groups and it was also superior in the protein supplemented group comparatively.