Crossing Inbreeds lines for Commerical Production

Introduction

Commercial hybrid corn's success is attributed to crossing highly inbred lines, resulting in hybrids that outperform varieties from older breeding methods. Heterosis, or hybrid vigor, plays a significant role, along with the careful selection of inbred lines to create favorable gene combinations in hybrids. The uniformity of these combinations contributes to higher yields, primarily due to consistent production across all plants rather than extraordinary yields from specific ones.

Inbreeding Challenges in Farm Animals

While most farm animal breeds are slightly inbred and genetically diverse, crosses between them exhibit only a modest level of hybrid vigor. The hypothesis that crosses between highly inbred lines could surpass existing performance levels necessitated the development of inbred lines. However, this task is more challenging in farm animals compared to crops due to factors such as the impossibility of self-fertilization, higher costs of maintenance, and limited resources for developing and maintaining inbred lines.

Inbreeding in Farm Animals

In spite of the difficulties, inbred lines with inbreeding levels typically not exceeding 30 to 60 percent have been successfully developed in various farm animal species. Higher levels of inbreeding lead to reduced productivity, with some lines being more affected than others. Traits of low heritability are particularly impacted, and in some cases, lines have been discarded due to low reproductive rates. However, the overall performance of inbred animals does not consistently surpass that of non-inbred counterparts.

Productivity and Inbreeding

As inbreeding levels increase, productivity tends to decrease, with specific traits affected more drastically. While some inbred lines have shown higher productivity, the average performance of all inbred lines does not consistently exceed that of non-inbred animals. This challenges the notion that inbreeding alone creates genetic strength leading to improved productivity in crossbreeding scenarios.

Potential of Crosses and Remaining Questions

Specific line crosses have occasionally outperformed outbred animals, suggesting the potential usefulness of the technique. However, doubts persist about whether the results from selected crosses are superior to those achievable through the selection within outbred stocks and the crossing of non-inbred strains within breeds or by breed crosses. The expenditure of time, effort, and money remains a key consideration in evaluating the overall effectiveness of different breeding strategies.