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

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Abstract
A replicated trial of 3 × 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% sorghumsoybean 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<.10) and methionine (P<.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<.10 or P<.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 disappearaed in the large intestine increased as feeding level decreased. Most comparisons between AL and limited feeding, and between 4.5 and 3%, were significant (P<.10 or P<.05). Estimated daily losses of dry matter and gross energy in the large intestine decreased with decreasing feed intake, but losses of N and amino acids increased with decreasing feed intake. The increased losses of N and amino acids may have resulted from the combination of longer retention time in the large intestine and lower daily supplies of nonprotein substrate to meet energy needs of the microbes at the lower levels of feeding. Copyright © 1984. American Society of Animal Science . Copyright 1984 by American Society of Animal Science

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