Journal of Animal Science, Vol 72, Issue 6 1583-1590, Copyright © 1994 by American Society of Animal Science

JOURNAL ARTICLE

Effects of feeding high-concentrate diets at restricted intakes on digestibility and nitrogen metabolism in growing lambs

T. A. Murphy, S. C. Loerch and F. E. Smith
Department of Animal Science, Ohio State University, Wooster 44691.

In Trial 1, 12 wether lambs (34.2 +/- .8 kg BW) were used to determine the effects of restricting intake of diets increasing in percentage of concentrate, to achieve isoenergetic intakes, on digestibility and N metabolism. The trial consisted of two 14-d periods, 9 d for adaptation and 5 d for total collection of urine and feces. Treatments were 22, 39, 61, and 92% concentrate diets fed at ad libitum intake and 90, 80, and 70% of ad libitum intake, respectively. Diets were formulated to provide equal daily intakes of ME. Feeding diets increasing in proportion of concentrate at restricted intakes resulted in linear increases (P < .001) in DM, OM, ADF, and NDF digestibilities. Starch digestibility was not affected (P > .10) by intake. Apparent N digestion was improved (P < .001) with restricted feeding of diets containing greater proportions of concentrate. Nitrogen retention was increased (P < .005) for lambs receiving diets containing a greater proportion of concentrate at reduced intakes. In Trial 2, 12 wether lambs (30.6 +/- .6 kg BW) were used to determine the effects of feeding high-concentrate (92%) diets at reduced intakes on digestibility and N metabolism. Diets were fed at ad libitum intake and 90, 80, and 70% of ad libitum intake. The trial consisted of two 14-d periods, similar to Trial 1. Restricting the intake of high-concentrate diets improved (P < .001) digestibility of DM, OM, ADF, starch, and CP. Digestibility of DM, ADF, CP, and starch increased .142, .423, .497, and .046 percentage units, respectively, for each 1% reduction in DM intake.(ABSTRACT TRUNCATED AT 250 WORDS)

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