Abstract
One hundred twenty-eight pigs were used in a balanced 24 × 8 factorial experiment in which the two-level factors were year, breed (Yorkshire and Duroc), line (high- and low-fat) and diet (normal and 25% reduction in gross energy intake). The pigs were slaughtered at eight ages from 84 to 392 days. The high-fat line gained 8 and 16% slower than the low-fat line in the Yorkshires and Durocs, respectively. There was an over-all 20% reduction in rate of gain and a 4% improvement in feed efficiency when energy intake was reduced. There was a significant breed x line x diet effect on rate of gain as a result of the variable, within line response to energy restriction. Average carcass and fat weights were heavier (P<.01) for Durocs than Yorkshires and the reverse was true for weight of lean and bone. Low-fat lines had more total lean and bone and less fat than high-fat lines. There were average decreases of 34% in fat weight and 7% in weight of lean and bone because of dietary energy restriction. This restriction resulted in changes of +4, −12, −10 and −9% in weight of lean for high-fat and low-fat Yorkshires and high-fat and low-fat Durocs, respectively. Copyright © 1969. American Society of Animal Science . Copyright 1969 by American Society of Animal Science