PSII-34 Comparison of the activity level of high and low residual feed intake beef steers

Abstract

Abstract Activity level may affect residual feed intake (RFI), and cattle that move more may have less energy for gain. We compared activity level in high and low RFI beef steers under different nutritional conditions. Lying time, lying duration and lying bouts were recorded at 1-minute intervals utilizing Hobo G Pendant Loggers attached to the right hind leg. To identify RFI classification, 57 Angus-cross steers were individually housed and offered ad libitum access to a TMR for 56 d. RFI was defined as the residual of the regression of DMI on mid-test BW0.75 and ADG. High and low RFI groups (14 steers each) were defined as > 0.5 SD above or below the mean of zero, respectively. Ad libitum feeding was followed by restricted feeding at 75% of previous ad libitum DMI/BW0.75. After 56 d ad libitum feeding, steers were moved to group pens, ad libitum fed 4 days (ADLIBFED), then fasted 4 days (ADLIBFASTED). This was followed by the 56 d individual restricted feeding, after which, steers were moved to group pens, fed 4 days of restricted DMI (RESTRICTFED), then fasted 4 days (RESTRICTFASTED). There was no difference in lying time (800 and 804 minutes/day, P = 0.85), lying bouts per day (9.8 and 11.4, P = 0.16) and lying duration (99 and 84 minutes/bout, P = 0.18) between low RFI and high RFI cattle, respectively. Fasted animals had less lying time each day (P < 0.05), manifested by fewer lying bouts per day (P < 0.05), that tended (P > 0.05) to be slightly longer than fed animals. Ad lib animals tended (P > 0.05) to have less lying time each day, with a similar number of lying bouts per day, that were slightly (P > 0.05) shorter than restricted animals. Although activity is not affected by RFI level, results suggest that periods of limited feed availability increases activity level.