|Cammack, Kristi - UNIV MISSOURI, COLUMBIA|
|Nielsen, Merlyn - UNIV NEBRASKA, LINCOLN|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 29, 2004
Publication Date: April 4, 2005
Citation: Cammack, K.M., Leymaster, K.A., Jenkins, T.G., Nielsen, M.K. 2005. Estimates of genetic parameters for feed intake, feeding behavior, and daily gain in composite ram lambs. Journal of Animal Science. 83:777-785. Interpretive Summary: Feed is a major cost of production for sheep producers and affects profitability of an enterprise. Understanding the role of genetics in feed intake is necessary to develop effective methods to select for improved conversion of feed into lean meat. An electronic feeding system was used to collect information on feed intake and feeding behavior of ram lambs. Feed intake is genetically controlled and sheep with greater intakes grow more rapidly and tend to eat more meals per day and spend more time eating. Selection to improve conversion of feed into lean meat is possible and would also cause changes in feeding behavior.
Technical Abstract: The objective was to estimate genetic parameters for feed intake, feeding behavior, and daily gain in composite ram lambs (½ Columbia, ¼ Hampshire, ¼ Suffolk). Data were collected from 1986 to 1997 on 1,239 ram lambs in Pinpointer units from approximately 11 to 17 wk of age at the U.S. Meat Animal Research Center near Clay Center, NE. Pinpointer units consisted of an elevated pen with an entrance chute that permitted access for only one ram lamb at a time to the feeder with disappearance of feed measured by an electronic weighing system. Ram lambs were grouped 11 per pen in 1986 through 1989, and 9 per pen in 1990 through 1997. Data were edited to exclude invalid feeding events. Approximately 80% of the data remained after edits were applied. Traits analyzed were daily feed intake (DFI), event feed intake (EFI), residual feed intake (RFI), daily feeding time (DFT), event feeding time (EFT), number of daily feeding events (DFE), and average daily gain (ADG). Feed intake traits of DFI and EFI had estimated heritabilities of 0.25 and 0.33, respectively, while estimated heritability of RFI was 0.11. Heritability estimates for feeding behavior traits, including DFT, EFT, and DFE, ranged from 0.29 to 0.36. Average daily gain had an estimated heritability of 0.26. Genetic correlations were positive between all traits, except RFI and ADG, and that estimate was essentially zero. Phenotypic correlations were generally similar to genetic correlations. Genetic correlations were greatest (0.80) between DFI and ADG, intermediate between DFI and RFI (0.61) and between DFT and DFE (0.55), and low (0.17 to 0.31) for the other pairs of traits with the exception of RFI and ADG (-0.03). Genetic correlations between behavioral traits were greater than correlations between behavioral traits and measures of feed intake or ADG. However, selection for daily gain and/or feed intake would be expected to cause some changes in feeding behavior.