The aim of this study was to investigate the possibility of adding whole soybean treated with different physical process (heating and grinding) to rations of lambs.

A total of 32, 7-8 month old male lambs with 37 kg average body weight were used. The rations were prepared as isonitrogenic and isocaloric. The experimental groups were based on the type physical processing method applied to the whole soybean. Accordingly: ground and heat-treated soybean group (I+ÖS), ground soybean group with no heat treatment (ÖS), heat-treated whole soybean group (I+BS) and whole soybean group with no heat treatment (BS).

The highest daily body weight gain was obtained in I+ÖS group and the lowest in BS group (P<0.05). Feed efficiency ratios in I+ÖS, ÖS, I+BS and BS groups were 4.98, 5.78, 5.55 and 6.34, respectively (P<0.05). There were no significant differences between the groups with respect to the digestibility of dry matter, ether extract, crude fiber and ash. While the digestibility of organic matter, crude protein and nitrogen free extract were similar in ÖS group and I+BS groups; the highest digestibility of organic matter, crude protein and nitrogen free extract were in I+ÖS group and the lowest in BS group.

In conclusion, physical processing of whole soybean involving grinding and heat-treatment (120 ºC 1 hour) positively affected the digestibility of organic matter, crude protein and nitrogen free extract and performance in growing lambs.