- Animals: sheep
- Animal Production: livestock breeding
- Education and Training: extension
This project aimed to improve sheep producer awareness and knowledge of residual feed intake (RFI) as a measure of feed efficiency, determine relationships of RFI with other traits of economic importance and identify variants in the leptin gene associated with improved RFI. Informational packets and surveys were distributed to producers to assess and improve knowledge regarding the RFI measurement. Performance test data analyses indicated that selection for RFI in sheep should not adversely affect carcass and fleece traits. Finally, sequence data of the leptin gene did not identify any genotypic variants associated with improved RFI status.
Feed costs represent >50% of total input costs for sheep producers (Nash, 1991). For sheep producers to remain profitable, means of reducing feed usage while not sacrificing performance are necessary. Residual feed intake (RFI) is an alternative measure of feed efficiency that is independent of body weight and maturity (Koch et al., 1963), a distinct advantage over traditional measures of efficiency. It is a preferred assessment of feed efficiency in many beef cattle breeds. Genetic selection for improved RFI would allow producers to select animals that are able to perform to standard with less feed usage. However, for genetic selection of RFI to successfully improve the bottom-line for producers, RFI must not be unfavorably correlated with other economic traits of interest, including carcass merit and fleece traits. In beef cattle, carcass traits such as rib fat thickness, loin mass area and marbling score are not correlated with RFI (Ribeiro et al., 2006). There have yet to be any reports on potential implications of RFI selection on fleece traits.
The leptin hormone has a regulatory role in whole-body energy metabolism. In beef cattle, variants of the leptin gene (i.e. genotypes) have been associated with changes in performance, namely growth rate, feed intake, metabolic body weight and final slaughter weight (Lagonigro et al., 2003; Nkrumah et al., 2005; Barendse et al., 2007). It is hypothesized that a number of these variants also contribute to differences in feed efficiency observed among individual cattle and have potential to ultimately serve as markers for genetic selection. We hypothesized that some of these variants also exist in the ovine leptin gene, providing a similar avenue for marker-assisted selection to improve RFI in sheep.
- Barendse, W., A. Reverter, R. J. Bunch, B. E. Harrison, W. Barris, and M. B. Thomas. 2007. A validated whole-genome association study of efficient food conversion in cattle. Genetics. 176: 1893-1905.
Koch, R. M., L. A. Swiger, D. Chambers, and K. E. Gregory. 1963. Efficiency of feed use in beef cattle. Journal of Animal Science. 22: 486-494.
Lagonigro, R., P. Wiener, F. Pilla, J. A. Woolliams, and J. L. Williams. 2003. A new mutation in the coding region of the bovine leptin gene associated with feed intake. Anim Genet. 34: 371-374.
Nash, T. G. 1991. Getting started with sheep emphasis on a commercial operation. Illinois Sheepman's Holiday and Symposium.
Nkrumah, J. D., C. Li, J. Yu, C. Hansen, D. H. Keisler, and S. S. Moore. 2005. Polymorphisms in the bovine leptin promoter associated with serum leptin concentration, growth, feed intake, feeding behavior, and measures of carcass merit. J Anim Sci. 83: 20-28.
Ribeiro, F. R. B., G. E. Carstens, P. A. Lancaster, L. O. Tedeschi, and M. H. M. R. Fernandes. 2006. Evaluation of feed efficiency traits in growing brahman heifers and relationship with body composition ultrasound traits and feeding behavior. In: American Society of Animal Science, Minneapolis, MN. p 123.
Objective 1. Assess and improve producer knowledge of RFI and determine acceptability of RFI adoption as the standard measure of efficiency in sheep.
Objective 2. Use producer rams on-test at the University of Wyoming to determine relationships of RFI with other traits of economic importance, including carcass and fleece traits.
Objective 3. Identify genetic markers associated with improved RFI of rams on-test for marker-assisted selection implementation in the long-term.