Different methods and times to estimate heat production in sheep fed with sunflower meal.

The objective of this study was to assess the oxygen pulse and heart rate method (O2 P-HR) using a respiration chamber at different measurement times for estimate the heat production (HP) of lambs fed increasing levels of sunflower meal in their diet. Twenty-four lambs were assigned to four experimental diets (0, 100, 200, and 300 g of sunflower meal kg-1 DM). Heat production was estimated using the O2 P-HR (HPO2P) method and a respirometry chamber (HPRC). Measurements were obtained by simultaneously measuring heart rate (HR) and oxygen consumption over 3, 6, 9, 12, 15, 18, 21 and 24 h. A flow-through respirometry chamber for small ruminants was used to determine oxygen consumption (VO2) and carbon dioxide and methane production. Data on dietary treatment, measurement times and their interactions were analyzed as repeated measures using mixed model procedures and Restricted Maximum Likelihood (REML) estimation. The Pearson's correlation coefficient was used to compare techniques. There was no effect of the different levels of sunflower meal inclusion on VO2 and heat production. The HPO2P (126.16 kcal/ BW0.75/day) was 2% higher than that of the HPRC (124.61 kcal/ BW0.75/day), and the correlation coefficients was 0.628. The coefficient of variation was greater for the HPO2P (21.33%) than for HPRC (11.44%). HR (beats/min), VO2 (mL/min/BW0.75) and O2 P-HR (mL/beat) required measurement times of 24, 15 and 9 hours, respectively. A measurement time of 24 h was necessary to ensure a more accurate estimate of the heat production using the O2 P-HR method. [ABSTRACT FROM AUTHOR]