Transferencia de embriones

Bioeconomic evaluation of embryo transfer in beef production systems: III. Embryo lines for producing bulls F. Ruvuna, J. F. Taylor, J. P. Walter, J. W. Turner and R. M. Thallman J Anim Sci 1992. 70:1091-1097.

The online version of this article, along with updated information and services, is located on the World Wide Web at: http://jas.fass.org

www.asas.org

Downloaded from jas.fass.orgby on May 1, 2008. Copyright © 1992 American Society of Animal Science. All rights reserved. For personal use only. No other uses without permission.

Bioeconomic Evaluation of Embryo Transfer in Beef Production Systems: 111. Embryo Lines €or Producing Bulls1
F. Ruvuna, J. F. Taylor, J. P. Walter, J. W. Turner, and R. M. Thallman Department of Animal Science, Texas A&M University, CollegeStation 77843

ABSTRACT: A model was developed for the economic evaluation of embryos for producing bull lines for use in commercial beef production. The fundamental concept underlying the model is that a cloned and sexed embryo of known genetic characteristics for beef traits is used to produce a bull. After reaching physiological maturity, the bull is used in natural matings. Equations relatingfeed energy requirements and growth rates based on NRC requirements and costs and returns discounted to present value allow investigation of expected economic merits of progeny from different embryo bull lines. The model has the flexibility to determine optimal embryo characteristics for different production environments. Model sensitivity to variation in progeny sex ratios, growth rates, yield andquality grades, and herd fertility characteristics was examined. Net present values (NPV)

per embryo transferred were determined at the optimal marketing age of progeny produced from mating the bull to 30 cows per year for 5 yr. Relative to the lowest NPV of $18,209 for progeny with a n expected quality grade of Select and yield grade of 4 at 400 d, increments in NPV ranged from $329 to $22,708depending on differences in expected progeny carcass grade characteristics. The difference between NPV for 100% male and 40% male sex ratios was $7,518. The NPV differences between progeny growth rates of 1.6 and .9 kg/d holding herd conception rate constant at .9 and .5 were $8,311 and $4,611, respectively. The model evaluates relative economic values of embryo lines for producing bulls,accommodating interactions among progeny characteristics, and environments.

Key Words: Econometric Models, Embryo Transfer, Net Present Value
J. Anim. Sci. 1992. 70:1091-1097

Introduction
Increased selection intensity and reduced generation interval are potential advantages of embryo cloning and transfer (ECT;Nicholas and Smith, 1983; Seidel and Elsden, 1989). Reports in the dairy industry(Gramlin, 1981; McDaniel and Cassell, 1981; Van Vleck, 1982; Navarro-Fierro et al., 1986) have concluded that ECT is profitable only to registered cattle breeders who supply young sires for AI and merchandise surplus female animals. Most evaluations of ECT have been based on a
~ ~

'Technical article TA25998 of the Texas Agric. Exp. Sta., College Station, 77843. This study was supported in part by agrant from Granada Biosciences, Inc. and in part by grant number 3248 of the Texas Advanced Technology Program. Received March 6 , 1991. Accepted October 31, 1991.

single criterion such as the number of progeny obtained per donor, with limited assessment of consequences to the whole production system. Economic merits of ECT for producing beef bulls applying a systems approach have not beenconsidered. Youngs et al. (1986) demonstrated in beef cattle that after one generation of selection the improvement in yearling weight could be 29.9% greater by using ECT rather than conventional methods. Nicholas and Smith (19831 showed that selected clones in a commercial dairy herd could increase genetic merit by > 25%. Considering that ECT techniques are becoming commercialized, there exists a...