Effects of level of feed intake on nitrogen, amino acid and energy digestibilities measured at the end of the small intestine and over the total digestive tract of growing pigs.

A replicated trial of 3 X 3 Latin square design was conducted with growing pigs (about 29 kg initially) to determine the effects of different levels of feed intake on nutrient digestibilities determined near the end of the small intestine and over the total digestive tract. Pigs were fiftted with simple T-cannula. Feeding levels were ad libitum (AL) and limit-fed (4.5 or 3% of body weight/d). A 16% sorghum-soybean diet was used. Limit-fed pigs were fed at 12-h intervals and water was limited to 2 liters/kg of diet; AL pigs received water ad libitum. Consumption by pigs fed ad libitum averaged 6% of body weight/d. Neither feeding method nor level greatly affected nutrient digestibility measured at the end of the small intestine, but values tended to decrease as feeding level decreased. Comparisons of nutrient digestibility between AL and limit-fed pigs ranged from 2.9 to .7 percentage units, with only N (P less than .10) and methionine (P less than .05) reaching significance. Differences between 4.5 and 3% were slightly larger, ranging from 4.3 to -.2 percentage units, with differences for dry matter, N, gross energy and several amino acids reaching significance (P less than .10 or P less than .05). Measured over the total tract, observed differences among feeding levels were again small, but the trend was reversed, with digestibilities increasing as feeding level decreased. The estimated percentage of ingested nutrients that disappeared in the large intestine increased as feeding level decreased.(ABSTRACT TRUNCATED AT 250 WORDS)