African Journal of Biotechnology Vol. 4 (9), pp. 1005-1009, September 2005          
ISSN 1684–5315 © 2005 Academic Journals

Full Length Research Paper

Different techniques of moult induction were used to force moult 360 commercial old layers, aged 85 weeks. The techniques were: natural day length with feed and water ad libitum, natural day length with water but no feed, natural day length with no feed and no water, reduced day length with feed and water ad libitum, reduced day length with water but no feed, reduced day length with no feed and no water, designated as T1, T2, T3, T4, T5 and T6, respectively. The T1 served as the control. Sixty hens were randomly assigned to each treatment which was replicated 3 times. The moult induction period was for 10 days coupled with 50 days of recovery period when the birds were fed low protein moult diet. At day 7, the ovaries of T2, T3, T5, T6 regressed weighing 3.43, 7.03, 5.00, 4.80 g, respectively. These were significantly (P<0.05) lower than the ovarian weights of 34.73 and 35.13 g of T4 and control (T1), respectively. By day 35 of moult induction, the ovaries of T2, T3, T5 showed the greatest recovery increasing to 18.53, 20.73, 13.27 g, respectively, while T4 decreased to 13.00 g. The number of large yellow follicles of T2, T3, T5, T6 decreased from 3.33 on day 0 to 0.00 on day 7. By day 21 the large yellow follicles of T2, T3, T5 and T6 started regenerating, ranging between 2.33 and 3.00 and by day 49 were significantly (P<0.05) higher than T4 (1.67). Plasma progesterone levels decreased from between 0.50 and 0.60 ng/ml on day 0 to undetectable levels by days 7 and 14 in T2, T3, T5, T6.  By day 21, plasma progesterone levels (ng/ml) started rising in T2 (0.40), T3 (0.33), T5 (0.40), T6 (0.33) although these were significantly (P<0.05) lower than those of T1 (0.77) and T4 (0.81). As the number of large yellow follicles increased, the concentration of progesterone in the plasma increased.

 Key words: Layers, forced-moult, ovarian follicle, progesterone