80 Effects of feeding level on performance and heat production of high and low residual feed intake beef steers

• Published in: Journal of animal science 2018-12, Vol.96 (suppl_3), p.401-401
• Main Authors: Andreini, E, Augenstein, S, Fales, C, Sainz, R, Oltjen, J
• Format: Article
• Language: English
• Subjects: Abstracts
• ISSN: 0021-8812; 1525-3163
• DOI: 10.1093/jas/sky404.880

Abstract Comparing heat production after ad libitum (ADLIB) and restricted (RESTRICT) feeding periods may offer insight to how residual feed intake (RFI) groups change their energy requirements based on feeding level. This study sought to explain efficiency changes of high and low RFI steers after feed restriction. To identify RFI classification, 56 Angus-cross steers were individually housed, offered ad libitum access to a total mixed ration, and daily intakes were recorded for 56 days. RFI was defined as the residual of the regression of DMI on mid-test BW 0.5 standard deviation above or below the mean of zero, respectively. Fourteen steers of each high and low group (n = 28) were selected for the subsequent 56-day RESTRICT period. During RESTRICT, DMI was restricted to 75% of previous ad libitum DMI as a percent of BW2 and CH4 emissions and O2 consumption were measured after each period. Fasting heat production (FHP) was measured during the last two days of a four-day fast. For high RFI animals, ADG (kg/d) differed (P0.05) between ADLIB (1.75 ± 0.13) and RESTRICT (1.07 ± 0.13) but was not statistically different (P=0.17) between ADLIB (1.74 ± 0.13) and RESTRICT (1.34 ± 0.13) for low RFI. For high RFI, FHP (Mcal/kg BW^0.75) did not differ (P=0.16) between ADLIB (0.195 ± 0.005) and RESTRICT (0.186 ± 0.005) and did not differ (P=0.07) for low RFI between ADLIB (0.196 ± 0.005) and RESTRICT (0.183 ± 0.005). For ADLIB, FHP did not differ (P=0.92) between low and high RFI and did not differ (P=0.72) between low and high RFI for RESTRICT. There was no difference between the decrease in FHP between high and low RFI.