Effect of Melatonin Implants and Nutritional Restriction on Growth Performance of Local Male Lambs

This experiment was conducted from 17 October 2021 to 9 January 2022 on the Department of Animal Production sheep field at the College of Agriculture, University of Anbar. The study aimed to determine the impact of melatonin implants and dietary restrictions on local male lambs' nutritional and growth performance. It included 16 local male lambs ranging in age from 5 to 6 months and weighing an average of 35.31 3.71 kg. The lambs were separated into four equal groups (n=4) and placed in separate pens. The actual duration of the experiment was 69 days, divided into two phases: the first phase consisted of 42 days of nutritional restriction, and the second phase consisted of 27 days of re-nutrition. As a control treatment during the stage of nutritional restriction, the first group (T₁) was fed ad libitum. In contrast, the second group (T₂) was fed Ad libitum with 36 mg subcutaneous-ear implanted melatonin implants, and the third group (T₃) was fed a restricted diet (R) of 75% of the Ad libitum. Comparatively, the fourth group (T₄) was fed a restricted diet of 75% of the Ad libitum with 36 mg of subcutaneous-ear implanted Melatonin. Until the end of the re-feeding phase, all experimental treatments were provided with unrestricted access to food. The nutritional and growth performance parameters were measured during the nutritional restriction and re-feeding stage and the entire experiment duration. During the nutritional restriction stage (42 days), there was no significant difference between the experimental treatments in terms of total weight gain, daily weight gain, feed conversion efficiency, and feeding efficiency. However, the experimental groups exhibited statistically significant differences in daily feed intake, daily dry matter intake, and dry matter intake as a percentage of body weight. In the re-feeding stage, there were no significant differences in the above nutritional and growth parameters among the experimental groups (27 days). This experiment concluded that feeding local male lambs 75% of Ad libitum with or without melatonin implants for 42 days, followed by re-feeding for 27 days, maintained the growth performance of the lambs with minimal feed intake and reduced lamb production costs.