The Efficacy of California versus High dietary Zinc forced Molting Methods on Performance and Egg Quality Traits of Commercial Layers in the Sudan

Abstract

A total of 450 commercial strain (Lohman) single comb white leghorn hens, 75wks of age and 43.6 % hen day production were used in this study to determine the effect of high dietary Zinc (ZFMM) versus the California (CFMM) forced molting programs on performance and egg quality traits of commercial layers in the Sudan. The hens were divided into two treatment groups of 150 hens and three replicates of 50hens each .The hens in the Zinc treatment group were watered and fed a layer ration containing 20000 ppm of zinc on adlib bases and received natural day light for five successive days .In the California group, the conventional layer ration was withdrawn for 10days and received natural day light, oyster shell and water were provided for adlibitum consumption .At day 11, hens were allowed sorghum grain and oyster shell ad libitum until day 30th and at day 31, hens were returned to a full feed layer ration and light was increased to 16h/day .Body weight ,egg production ,internal and external egg quality were measured. Liver weight and oviduct weight and length were also determined and mortality recorded. Total and differential circulating leukocyte counts were also measured. The results demonstrated that induced molting significantly increased egg production from 43.6± 0.99 to levels ranging from 55.6±0.99 to 65.6 ± 0.99 (% ) viiand shell thickness from 0.37± 0.01 to a range of 0.41± 0.01 to 0.47± 0.01 (mm) when compared to the post molting period. Egg weight, specific gravity, yolk colour largely remained unaffected by either of the induced molting programs. There was no significant difference in mortality rate between the two molting methods. From 1st day till 14 days of the experimental period CAL group was significantly (P<0.05) higher in body weight losses (26.7±1.79 %).No treatment were observed in liver weight in the 2 nd period of the study. During the 3 rd period no significant differences (P<0.05) were observed in the reproductive system parameters including ovary weight, oviduct weight and length. Plasma progesterone levels decreased from between 0.60 ± 0.12 ng/ml on day 0 to undetectable levels 0.00 ±0.00 ng/ml by day 7 and 14 in both CAL and Zn groups. By day 21 plasma progesterone started rising in CAL group to (0.40± 0.06 ng/ml), although it was significantly (P<0.05) lower than that of premolted hens (0.77±0.09 ng/ml) and Zinc group (0.81± 0.16 ng/ml). Calcium level remained unaffected by either of the tested molting methods, while molting methods significantly (P>0.01) reduced the plasma phosphorous and magnesium levels, they depicted significant elevation in the plasma levels of sodium and potassium in the blood plasma of the hens viiisubjected to forced molting total protein, albumin, glutamic oxaloacetate transaminase and glutamic pyruvate transaminase were decreased independent of the force molting method. Total circulating leukocytes were also significantly lower in the molted hens. The heterophil to lymphocyte ratio was significantly increased, reaching 0.39±0.05 versus that of nonmolted hens of 0.17±0.01. It is concluded from the study that molting process has substantial impact on egg production and can be successfully practiced in the Sudan. In this study the high Zinc force molting program generally seemed to excelled the California force molting program in recovering better egg production rate and egg quality.