Abstract:
Previous research studies have been limited to the effect of dietary salt (deficiency or excess) on the general performance of laying birds and there is dearth of information on its effects on the reproductive tract, reproductive parameters and serum biochemistry of laying birds. An experiment was conducted to evaluate the effect of varying levels of dietary salt on the performance, follicular development, gonadal morphometry and serum biochemistry of late production layers. One hundred and twenty (120) late production layers were randomly assigned to four experimental diets each containing 30 birds replicated thrice with 10 birds per replicate. Four experimental diets were formulated with varying levels of dietary salt. The control diet had 0.25% salt, whilst the remaining diets had 0.50%, 0.75% and 1.00% levels of salt respectively. The feeding trial lasted for eight weeks. Data were collected daily on feed intake, hen day production, egg weight and mortality. At the end of the trial, thirty-six birds were slaughtered, dissected and the reproductive tract and the ovaries were weighed, counted or measured accordingly. The number and dimensions of follicles in each of the bird slaughtered was taken. Blood samples were also collected and analyzed for serum biochemistry. All the data obtained were analyzed using one way analysis of variance (ANOVA) in a Completely Randomized Design. The results showed a significant dietary effect (P<0.05) on hen-day production, hen-housed production, total feed intake and mortality. The results also showed a significant dietary effect (P<0.05) on the weight of ovary and the length of the infundibulum. The ovarian mass was highest (34.56g) in birds fed 1.00% dietary salt and lowest (23.12g) in those fed 0.50% dietary salt. Birds fed 1.00% dietary salt had the highest weight (95.45g) of entire reproductive tract and ovary. The dietary salt levels also significantly affected (P<0.05) the number of follicles with birds fed 1.00% salt producing the highest number (22.67) of pre-vitellogenic follicles. The biochemical indices of the late production layers was also significantly (P<0.05) influenced by the dietary salt levels. Total Protein increased in birds fed higher inclusion of dietary salt relative to the control, Albumin level was significantly lower (P<0.05) at higher dietary salt levels in comparison with the control. It was also discovered that there was a negative correlation between glucose levels and egg production. Conclusively, increasing the dietary salt allowance of late production layers could be used as a management strategy to sustain them in production until it is economically favourable to dispose them off as spent layers.
