Heat production determined of Saanen and Anglo Nubian goats using CN method
Previous studies have demonstrated that heat production of goats is highly dependent on breed. Heat production (HP) can be determined using the respiratory quotient (RQ) method or the C-N balance (CN method).The CN method estimates the retained energy (RE), and the heat production (HP) is calculated as the difference between metabolizable energy intake (MEI) and RE. Therefore, this study aimed to assess the HP of Saanen and Anglo Nubian goats using the CN method. Six dry and non-pregnant Saanen weighing 55 ? 8 kg body weight (BW)and six Anglo Nubian goats weighing 51 ? 7 kg BW were used. Goats were allocated in individual metabolism cages and fed total mixed ration (9.8% CP, 16.7 MJ ME/kg dry matter, DM), consisted of 90% of corn silage and 10% of concentrate. After 15 d of adaptation, feed intake, fecal and urine output were recorded daily during 5 d, and samples of diet, feces and urine were collected daily, stored, and pooled for chemical analysis. Fat was assumed to have an energy equivalent of 39.76 kJ/g and a content of 0.767 C, and protein was assumed to have 23.86 kJ/g and 0.16 N and 0.52 C. The RE (kJ) as protein (REprot) and as fat (REfat) were estimated as: REprot (kJ/kg0.75BW/d) = N balance (g) x 6.25 x 23.86, and REfat (kJ/kg0.75BW/d) = (C balance (g) - N balance (g) x 6.25 x 0.52) x 1.304 x 39.76. The RE (kJ) was calculated as RE = REprot + REfat. Statistical analyses were performed using MIXED procedure (SAS, 9.4). The REprot , REfat and RE did not differ between breeds (P = 0.85, 0.64 and 0.63, respectively) and averaged 17.6 ? 11.1, -54.8 ? 113.4 and -37.2 ? 105.4 kJ/kg0.75BW/d, respectively, indicating that goats mobilized fat to supply their energy deficit. The MEI and HP did not differ between breeds (P = 0.10 and 0.96, respectively) and averaged 328.3 ? 26.1 and 365.5 ? 115.3 kJ/kg0.75BW/d, respectively. In conclusion, the HP and RE of Saanen and Anglo Nubian goats are similar when estimated using CN method.