Cattle breeders would like to improve the protein content and butterfat content of milk produced by a herd of cows. Narrow sense heritability values are 0.60 for protein content and 0.80 for butterfat content. The average percentages of these traits in the herd and the percentages of the traits in cows selected for breeding are as follows. Trait Herd Average Selected Cows Protein content 20.2% 22.7% Butterfat content   6.5%   7.4% Determine the selection differential (S) for each trait in this herd.

Key Concepts

Narrow Sense Heritability

Narrow sense heritability (h²) quantifies the proportion of phenotypic variance in a trait that can be attributed to additive genetic variance. It is crucial for predicting the response to selection in breeding programs. A higher h² value indicates that a trait is more likely to be passed on to the next generation, making it a key factor in determining the effectiveness of selective breeding.

Selection Differential (S)

The selection differential (S) is the difference between the average trait value of selected individuals and the average trait value of the entire population. It reflects the extent to which selected individuals exceed the population average, providing insight into the potential for improvement in the trait through selective breeding. Calculating S is essential for understanding the impact of selection on trait enhancement.

Response to Selection

Response to selection refers to the change in the average trait value of a population following selection. It can be estimated using the formula R = h² × S, where R is the response, h² is narrow sense heritability, and S is the selection differential. Understanding this concept helps breeders predict how much a trait will improve in future generations based on current selection practices.