Influence of addition of different antibiotics in semen diluent on viable bacterial count and spermatozoal viability of Awassi ram semen

The objectives of the present study were to determine the effects of six different antibiotics in controlling the growth of semen contaminating bacteria and if these antibiotics have any adverse effect on Awassi ram spermatozoa. Semen samples from six mature Awassi rams were used in this study. A total number of 120 ejaculates were collected from the rams using an artificial vagina once a week. Semen ejaculates were evaluated for volume, sperm concentration, mass motility, individual motility, percentage live sperm, sperm abnormalities, and viable bacterial count. Semen samples were diluted by sodium citrate-fructose-egg yolk. The diluted semen sample was divided into 7 parts. Six types of antibiotics were added to the semen diluent parts including; penicillin G 1000 IU ml-1 with streptomycin 1 mg ml-1, gentamicin sulphate 250 mg ml-1, tetracycline 0.5 mg ml-1, lincomycin 1 mg ml-1, cefoperazone sodium 1mg ml-1, cefdinir 1 mg ml-1 and the seventh part considered as a control group without antibiotic addition. The diluted semen samples were cooled and preserved at 5 Co for 5 days. Cooled diluted semen samples were examined for individual motility, percent of live sperm, sperm abnormalities, acrosomal defects and bacterial count every 24 h until 5 days. Comparing with the control, all the antibiotics examined were effective in controlling bacterial growth (P<0.05) from 24 h to 96 h of preservation at 5 Co. Cefdinir and cefoperazone sodium proved to be significantly (P<0.05) effective than other antibiotics in controlling bacterial growth at 96 h of preservation as the bacterial count were 23.3 &#177; 3.7 x 103 / ml and 25.4 &#177; 6.2 x 103 / ml, respectively. Lincomycin, gentamicin sulphate and tetracycline proved ineffective in controlling bacterial growth at 96 h of preservation as the bacterial count were 57.1 &#177; 20.1 x 103 / ml, 52.5 &#177; 29.4 x 103 / ml and 46.5 &#177; 8.8 x 103 / ml, respectively. The addition of tetracycline to diluted ram semen significantly reduced (P<0.05) sperm individual motility and percent live sperm and a significant increase (P<0.05) acrosomal defects was observed at 96 h of preservation in comparison to control and other antibiotics. Sperm viability was highly correlated with bacterial count in the control part of diluted semen (r = 0.794; P < 0.01). It could be concluded from the results of the present study that additions of cephalosporins (cefdinir or Cefoperazone sodium) at the dose of 1 mg ml-1 were most effective amongst the antibiotics used in checking the bacterial growth and improving semen quality of Awassi ram. [Vet. World 2012; 5(2.000): 75-79]