**Factors That Affect Energy Efficiency and Indirect Response of Selection for Efficiency on Related Traits**

Ghader Manafiazar, Thomas McFadden, Laki Goonewardene, Erasmus Okine and Zhiquan Wang

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/50776

## **1. Introduction**

120 Milk Production – An Up-to-Date Overview of Animal Nutrition, Management and Health

meat quality: a review. *Meat Sci,* 78: 343-358

Wood, J. D., Enser, M., & Fisher, A. V. (2008). Fat deposition, fatty acid composition and

The breeding goal of most livestock operations is maximizing profitability, which is a function of input and output ( Veerkamp & Emmans, 1995; Archer et al., 1999; Crews, 2005). In most livestock populations, selection programs have primarily focused on progressively improving means for output traits such as live weight gain, fertility, meat and milk yield (Archer et al., 1999; Sainz & Paulino, 2004; Crews, 2005). However, there has recently been a renewed interest in another component of profitability, namely the reduction of inputs or the increase in efficiency (Crews, 2005). Feed is one of the most important input components, and it represents more than one-half of the total costs in most livestock operations (Kennedy et al., 1993). In the dairy industry, feed cost represents about 40 to 50% of the total milk production cost and has increased substantially over the last few years (Garcia, 2009). Gibb & Macallister (1999) reported that the economic effect of a 5% improvement in feed efficiency is four times greater than a 5% improvement in average daily gain. Therefore, reducing production costs or increasing feed efficiency are the two most important ways to improve production efficiency and profitability. They also decrease environmental pollution and the carbon footprint (Capper et al., 2010). In order to gain the maximum benefits of genetic selection for energy efficiency, factors that influence energy efficiency and its indirect effects on other traits should be known. The most common measures of energy efficiency and their properties are reviewed in this chapter. It also deals with factors that practically affect energy efficiency. Furthermore, as there are very few reports on direct selection for energy efficiency in dairy cattle (Linn, 2006), the authors reviewed the indirect effect of selection for energy efficiency on other traits in beef cattle as well as in other species in addition to dairy cattle.

© 2012 Manafiazar et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
