The effect of graded levels of ram testes on sex, growth and survival of <i>Oreochromis niloticus</i> (Linnaeus, 1856)

Abstract

The study investigated the effects of homogenized ram testes using shrimp meal as carrier on the phenotypic sex, survival and growth of Oreochromis niloticus. To determine the phenotypic males, specific growth rate and survival rate, 4 different ratios of shrimp to ram testes 1:0 (T0), 1:1 (T1), 1:2 (T2) and 1:3 (T3) were fed to 7 days-old fry for the period of 28 days in plastic tanks (45 cm diameter x 30 cm deep) indoors. The results showed that the highest (82.0 %) numbers of males were recorded in fry treated with 1:3 shrimp to ram testes, followed by those treated with 1:2 shrimp to ram testes. Significant variation (p<0.05) was observed between the number of males in fry treated with 1:3 shrimp to testes and those fed 1:2 of shrimp to ram testes. Survival was higher (92.3 %) in the 1:0 (control) shrimp to ram testes. However, fry treated with higher dosage of the ram testes were heavier (66.0g). Feeding 7 days old fry with ram testes at the ratio of 1:2 to 1:3 testes and fish diet could reduce the number of females in the cultured population thereby decreasing the precocious reproduction in fish ponds. Ruminant testes are cheap and readily available, hence could be utilized for the control of precocious reproduction in tilapia.