Cow-Calf Certification Practice Exam

Which term describes the increase in performance observed when different breeds are crossed?

1. Hybrid vigor

2. Selective breeding

3. Inbreeding

4. Genetic drift

The correct answer is: Hybrid vigor

Hybrid vigor, also known as heterosis, is the phenomenon observed when the offspring resulting from the crossing of two different breeds exhibit enhanced performance or traits compared to their parents. This increase in performance can manifest in various aspects such as growth rate, fertility, disease resistance, and overall health. The advantages of hybrid vigor arise because the genetic diversity introduced through crossbreeding can enhance the expression of desirable traits and mask deleterious traits present in the parental breeds. This concept is particularly significant in livestock production, where crossing breeds can lead to more robust animals with improved productivity. By utilizing hybrid vigor, producers can achieve better outcomes in breeding programs aimed at enhancing livestock efficiency and sustainability. In contrast to hybrid vigor, selective breeding focuses on choosing specific individuals from a breed to perpetuate desired characteristics, which does not inherently lead to the genetic benefits seen in hybrid vigor. Inbreeding, on the other hand, involves mating closely related individuals, which can often reduce genetic diversity and lead to inbreeding depression, rather than the improved performance seen with hybrid vigor. Genetic drift refers to random changes in allele frequencies in a population, which is unrelated to the systematic performance improvements observed in crossbred offspring.