Abstract
The present experiment aimed to examine the effects of controlled feeding (which is well known as a method for body fat deposition reduction) with low-CP feed on the growth and carcass quality of fattening pigs. Feed used in this study was prepared by reducing the CP level by 2.2% from the standard level during the fattening period according to the Japanese feeding standard for swine (1998), and by supplementing it with lysine. Eight crossbred pigs were used and they were divided into two groups having the same mean body weight as follows : a control group, ad libitum of low-CP feed and an experimental group, 85% controlled feeding of low-CP feed. The animals were fed in a temperature-controlled room at 25±2°C using a single cage with feed and water every day. Feed intake, water drinking, and feces were determined every day. Body weight and body size were determined every week. Digestion trial was conducted in the last week. After slaughtering, carcass measurements and analysis of the chemical composition of the loin and the chemical character of the back fat were conducted.
The fattening period, from a body weight of 70kg to 106.9±1.9kg, took 41 days in the control, and in the experimental group it took 55 days to reach 106.5±1.5kg. Although the feeding level of the controlled feeding was designed to be 85% of the control group, it resulted in at about 81%. This reduction induced an increase in the fattening periods and total feed intake. The enlarging of body length, depth of chest, and width of chest in the experimental group was significantly (P<0.05) smaller than that of the control group. Digestibility of ether extracts in the experimental group was significantly (P<0.05) higher than that of the control group, but the levels of nitrogen free extracts and ADF were significantly (P<0.05) lower in the experimental group. In the results of carcass measurements, the shoulder part and waist part of back fat thickness in the experimental group were significantly (P<0.05) thinner than those in the control group.
In the results of amino acid analysis, lysine and threonine intake was insufficient even in the control group. Intakes for those amino acids, sulfur-containing amino acids, tryptophan, and branched-chain amino acids were also insufficient in the experimental group. The present results suggest that controlled feeding reduces the body fat deposition, although the amino acid imbalance might induce body fat deposition.
