Bioeconomic evaluation of embryo transfer in beef production systems: III. Embryo lines for producing bulls

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 relating feed 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 and quality 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 an expected quality grade of Select and yield grade of 4 at 400 d, increments in NPV ranged from $329 to $22,708 depending 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.

Simulation and economic analysis of bovine sex selection

“…Ruvuna et al (1992) found major increases in the proportion of males when using sexed sperm to produce bulls. Smeaton & Vivanco (2002) noted that the value of sexed semen in ET beef cattle was dependent on the cost paid for males and females at birth.…”

“…Aspects of the viability of sexed semen were also studied by Ruvuna et al (1992) and Madalena et al (2004). In these studies, the NPV was used to evaluate the use of sexed semen in AI and ET, which showed promising expectations for the implementation of this biotechnology.…”

Sexagem de espermatozoides bovinos por centrifugação em gradiente descontínuo de densidade de Percoll

“…A sexagem de espermatozoides tem valor econômico significativo nos animais de interesse zootécnico com aptidão para produção de leite ou carne e em sistemas em que a produtividade é favorecida pela progênie de um dos sexos (Taylor et al, 1985;Van Vleck et al, 1987;Ruvuna et al, 1992;Hohenboken, 1999).…”

Avaliação das características da motilidade (CASA), morfologia e funcionalidade da membrana plasmática (HOST) de espermatozóides bovinos sexados por cimetria de fluxo

“…Na produção de animais para abate, o peso da carcaça num macho, aos 24 meses é cerca de 25 % maior que o peso da carcaça numa fêmea da mesma idade. O valor de um rebanho com 100 % de machos vai ser 34 % maior, comparado com um rebanho composto de 40 % de machos (RUVUNA et al, 1992). Nos programas de cruzamento industrial a pré-seleção do sexo maximiza a produtividade devido às diferenças entre os sexos nas características de carcaça.…”

“…Vários autores registraram o valor econômico significativo da pré-seleção de sexo na pecuária de leite e de corte, atividades onde a produtividade é favorecida quando a progênie é constituída, em sua maioria, por um dos sexos (NICHOLAS; SMITH, 1983;TAYLOR et al, 1985;VAN VLECK et al, 1987;RUVUNA et al, 1992). A pré-seleção do sexo pode acelerar o progresso genético como também, beneficiar o manejo e a eficiência produtiva PARRILLA et al, 2005).…”