The effect of fat supplement type on performance, nutrient digestibility and ‎physiological parameters of finishing lambs during summer heat stress

An experiment was performed to investigate the effects of using saturated and unsaturated fatty acids calcium salts on the production performance and some physiological traits of finishing lambs fattened under heat stress condition. Thirty-two cross bred Lori-BakhtiariÍRomanov lambs were randomly divided into 4 groups. Lambs were fed individually with the following experimental diets for 6 weeks (early July to mid-August): 1) Basal diet without supplemental fat (control), 2) Basal diet supplemented with 2% (on DM basis) of fish oil calcium salt, 3) Basal diet supplemented with 2% (on DM basis) of olive oil calcium salt and 4) Basal diet supplemented with 2% (on DM basis) of saturated fat calcium salt. Daily feed intake was recorded and lambs body weight was measured weekly. Rectal temperature and respiration rate were measured once per week. Using calcium salts of fish oil, olive oil and saturated fats in the diet significantly increased daily weight gain and reduced the lambs feed conversion ratio compared to control group (P≤ 0.05), but had no effect on dry matter intake of the Lambs. Regardless of fatty acid origin, supplementing lambs with calcium salts of fatty acids, reduced rectal temperature and respiration rate of lambs exposed to heat stress, compared to control group (P≤ 0.01). Also, using calcium salts of Fish oil, olive oil and saturated fat had no effect on DM, CP and EE digestibility, however, EE digestibility was higher in lambs consumed fat-supplemented diets than the control group. NDF digestibility was significantly higher in the control group lambs than the other groups. The results of this study showed that diet supplementation with calcium salts of unsaturated fatty acids of fish and olives and saturated fatty acids, improved the production performance of finishing lambs exposed to heat stress. No difference was detected between fat supplements with different fatty acid patterns, in this investigation.