To study the effect of dietary lasalocid on serum insulin, cholesterol, Ca, P, Mg, Zn and Cu as well as semen quality and freezability, a number of six mature Barki rams (about 26 months of age and 46.5kg) were used during the periods of pretreatment (before feeding for 3 sucessive weeks) and post treatment (after feeding for 9 sucessive weeks) periods. The pretreatment diet was 4 kg green corn (Darrawa) plus 250 kg of pelleted complete diet (11% crude protein and 2.4 Mcal ME/kg). Lasalocid treatment (post treatment) was the pretreatment diet with the addition of 22 mg lasalocid sodium head\day. Feeding lasalocid resulted in significantly (p < 0.05) higher serum insulin (5.53 -6.19 ng/ml), cholesterol(81.00 - 85.78 mg/dl), P (5.13 - 5.52 mg/dl), Mg (2.93- 3.03 mg/dl), Zn (1.38 -1.46 mg/l) and Cu (0.99 . 1.15 mg/dl) during post-treatment period than before (pretreatment; 4.83 ng/ml, 78.5mg/dl, 4.65mg/dl, 2.86mg/dl, 1.14mg/l and 0.86mg/l, respectivily). On the contrary, serum Ca level was significantly (p < 0.05) lower after lasalocid supplementation (9.52 - 9.08 mg/dl) than before(9.88 mg/dl). Lasalocid fed rams also exhibited a greater(p < 0.01)scrotal circumference (33.95 - 37.83 cm) than before feeding (31.92 cm). On the other hand, neither semen volume (ml) nor L/D (%) was affected by lasalocid supplementation. However, both semen concentration and individual motility were significantly (p < 0.05) improved by lasalocid feeding (4243.3 - 6133.3 X10°/ml and 85.28 - 90.00%, respectivily) than before (2434.4 x 10ml and 71.67%, respectivily). On contrast, both major and minor abnormalities tended to be increased by lasalocid feeding. Meanwhile, both post-thawing motility and viability index of frozen semen were significantly (p < 0.05) higher during post-treatment (38.33-55.83% and 48.75-102.92, respectivily) than during pretreatment (33.06% and 38.91, respectivily) period. Significant correlation coefficients were reported between some serum and semen
parameters as well as scrotal circumferance. It can be concluded that, lasalocid sodium can be used in a rate of 22mg\head\day for Barki rams for improving semen quality and freezability during breeding season.