872 Effects of including ruminally inert fat in the diet of heat-stressed lambs on dry matter and water intake and physiological parameters

Abstract

The effect of 3 ruminally inert fat supplements in the diet of crossbred lambs on DMI, water intake (WI), and physiological parameters associated with heat stress under tropical conditions (28–30°C and 75% relative humidity) was determined. Twelve lambs (25.83 kg average initial weight) were fed to meet or exceed current NRC recommendations with a basal diet providing 17% CP and consisting of 50% alfalfa hay, 36.24 cracked corn, and 12.01% soybean meal and supplemented or not with 1.75% of ruminally inert fat provided as free fatty acids (FFA) or 2 experimental fat products from palm oil (E1 and E2). The lambs were assigned to 1 of 3 Latin squares. Treatments were no additive or diets containing FFA, E1, and E2. Feed was offered daily at 4% of lamb BW (DM basis). Experimental periods were 21 d, consisting of 14 d of adaptation to the diet followed by 7 d of data collection. Data collected included DMI (g/d), WI (L/d), and percentage WI in relation to animal BW, and the DMI:WI ratio was determined. Physiological parameters associated with heat stress included respiration rate (RR), heart rate, (HR), and rectal temperature (RT). Data were analyzed according to a 4 × 4 Latin square experimental design replicated 3 times. The Tukey test was used for mean comparison. There were no differences (P > 0.05) in DMI or WI among experimental treatments, averaging 1,190 g/d and 4.48 L/d. Percentage WI in relation to animal BW and the DMI:WI ratio were also similar for all experimental treatments (averaging 21.93% and 3.76, respectively). Inclusion of ruminally inert fat did not affect HR, RR, and RT and resulted in an average of 109 breaths/min, 73.24 beats/min, and 102.9°C. In summary, the inclusion of 1.75% ruminally inert fat in the diet of crossbred lambs did not affect DMI, WI, and physiological parameters associated with heat stress under tropical conditions.