Preweaning growth of Yorkshire, Hampshire, and Landrace pigs.

Individual pig growth curves were derived on 445 Yorkshire, 323 Hampshire, and 316 Landrace boars and gilts. The range in age was from 1 to 35 d and these growth curves were linear. The regression parameters (x- and y-intercepts, and slopes) were different among the three breeds, and differences between boars and gilts were found in the Yorkshire breed for the y-intercept and slope and in the Landrace breed for the y-intercept and slope and in the Landrace breed for the y-intercept. An additional 130 Yorkshire, 126 Hampshire, and 96 Landrace boars and gilts were used to evaluate the effectiveness of adjustments that were additive, multiplicative, additive-multiplicative, or based on the x- and y-intercepts. Effectiveness was evaluated in terms of accuracy, equality of variance, and practical application. The multiplicative adjustments were the most effective in the Hampshire breed and the average of the additive and multiplicative adjustments was the most effective in the Yorkshire breed. In the Landrace breed none of the four methods evaluated produced a credible adjusted 21-d weight. From an industry standpoint this study suggests the need for breed-specific specific adjustments, and in some breeds this may have to be extended to sex-specific adjustments.