Nutritional performance, clinical chemistry and semen characteristics of goats fed a mustard ( Brassica juncea) cake based supplement with or without iodine

Abstract

Effects of iodine (I) supplementation on performance of intact and castrated goats fed a mustard ( Brassica juncea) cake based diet were studied in fourteen 2-year-old goats (six intact and eight castrated bucks) for 210 days. Goats were initially assigned to one of the two dietary treatments (0 or 0.1 mg supplemental iodine) in a 2×2 factorial design. Concentrate supplement contained 35% mustard cake, which was fed along with oat hay ad libitum. A metabolic trial conducted 180 days after the experimental feeding revealed no effect of I on the digestibility of the organic nutrients. Castrated animals, however, exhibited greater ( P<0.05) digestibilities than intact bucks. Mean daily intake (per unit metabolic body size) of DM (44.86 versus 36.13 g) and ME (379.0 versus 300.7 kJ) were increased ( P<0.05) due to I supplementation, but not the CP or DCP intakes. Retention of N, Ca and P were similar irrespective of I level or castration. Average daily gain of the goats at the end of 210 days of study was higher ( P<0.01) in the I supplemented (25.5 g) than non-supplemented (10.9 g) goats. DM intake also improved ( P<0.01) because of provision of extra iodine (556.2 versus 448.9 g per day). Serum triiodothyronine concentration was similar between the groups, I supplementation increased ( P<0.01) serum thyroxine from 21.43 to 29.72 ng ml −1 with a concomitant reduction ( P<0.01) in serum cholesterol. Semen quality of bucks assessed at the end of the study revealed a significant ( P<0.05) improvement in the physical seminal attributes, viz. volume, motility, concentration and number of spermatozoa/ejaculate due to extra iodine, with a concurrent improvement in serum testosterone (1.75 versus 0.47 ng ml −1). Overall, the study revealed significant beneficial effect of extra I in goats fed high level of mustard cake in their diet.