Effects of low-CP and low-TDN feeding on the growth, meat quality, and nitrogen excretion of fattening pigs

In this experiment, we examined the effects of CP and TDN reduction on the growth, meat quality, and nitrogen excretion of eight fattening crossbred pigs (70110 kg). Two types of feed were prepared as follows : as a control, low-CP and standard-TDN feed (9.5%-75%) and as experimental feed, low-CP and low-TDN feed (9.5%-70%). Both of them were supplemented with lysine. They were formulated using the same ingredients and TDN decrease was induced by increasing the corn cob meal ratio in the feed. The animals were divided into the above-mentioned two groups having the same mean body weight. Experimental feeding was conducted in a temperature-controlled room at 25+-2 deg C using a single cage with feed and water given ad libitum. Feed intake, water drinking, feces, and urea were determined every day. Body weight and body size were determined every week. Digestion trial was conducted in the last week. The loin area and backfat thickness at the starting point and end of experiment were determined using ultrasonic measurement. After slaughtering, carcass measurements and analyses of the chemical composition of the loin and the chemical character of the backfat were conducted. Furthermore the fecal and urinal nitrogen and ammonium gas generation density from these was determined. It took 42days to reach a mean body weight of 110kg in both groups. While there was no significant difference in the daily body weight gain, feed intake, water drinking, feed efficiency, body size measurements, loin area obtained by ultrasonic measurement, and backfat thickness, feed intake and feces amount tended to increase in the experimental feed group. Digestibilities of CP, ether extracts, ADF, and calories in the experimental feed group showed significantly lower values than those in the control group and the DCP values in the experimental feed group were also significantly (P<0.05) lower than those in the control feed group. There was no significant difference in the results of carcass measurements, but the backfat thickness in the experimental feed group tended to be slightly thinner. Ether extract contents in loin also tended to decrease in the experimental feed group. Nitrogen contents in feces and urea tended to decrease in the experimental feed group, but the ammonium gas generation changed with a higher value in the experimental feed group. Present results were concluded as follows ; the low-CP and low-TDN feeding did not reduce the growth and evaluation of carcass and it reduced the concentration of nitrogen in feces and urea, however it tended to consume more feed and excrete more feces and urea. Therefore a high absolute value of nitrogen was excreted in the low-CP and low-TDN feeding.