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The effects of dietary boric acid (BA) supplementation on feed consumption, feed efficiency, egg production, egg weight, eggshell thickness, eggshell breaking strength, and some serum parameters (Ca, P, and Mg) were examined in 100 layer hens at 60 weeks of age. Commercial corn-soy-based layer diets were formulated as basal diets for the control treatment. Basal diets were supplemented with 25, 50, and 100 mg/kg BA (H3BO3), respectively, in experimental groups I, II, and III. In total, 4 dietary treatments were employed in the experiment. The experiment lasted 75 days. Feed efficiency and egg production values were not affected significantly by dietary treatments during the experiment (P > 0.05). However, layer hens that received diets supplemented with BA had better feed consumption, egg weight, percentage of cracked eggs, and egg shell quality (eggshell thickness, eggshell breaking strength) than the control group. Additionally, serum Mg levels were significantly (P < 0.01) increased by BA supplementation. It was concluded that dietary boron supplementation has positive effects on mineral balance, and therefore reduces the percentage of cracked eggs by improving eggshell thickness and egg shell breaking strength in aged laying hens. [ABSTRACT FROM AUTHOR]

The present study was performed to determine the structural differences and immunohistochemical distribution of follicle-stimulating hormone (FSH) producing cells in the pars distalis region of the pituitary glands of 5 month-old laying hens, using the labeled avidin-biotin method. Hens begin to lay eggs at approximately the age of 5 months. It was observed that gonadotrophic cells containing FSH were present in both the cephalic and caudal zones and were densely distributed throughout the pars distalis. They appeared to be arranged in either cords or follicles in which branching and anastomosing occurred as well as being found as separate cells. The strongest positive FSH immunoreactivity was observed in most of the cells located in the caudal and cephalic zones of the pars distalis in 5 month-old laying hens. Furthermore, the total numbers of FSH immunoreactive cells (in 1 µm2) were similar in the cephalic and caudal zones. [ABSTRACT FROM AUTHOR]