Chlortetracycline

Abstract

Two trials were conducted to evaluate the addition of a forage-fat blend (FFB) as a substitute for grain in finishing diets for feedlot cattle. Treatments consisted of a steam-flaked wheat-based finishing dies containing 15, 29, or 45% FFB. The FFB contained 80% chopped alfalfa hay and 20% yellow grease and was formulated to have NE^sub m^ and NE^sub g^ values similar to that of wheat. In Trial 1, 126 crossbred steers (225 +/- 5.4 kg) were used to

evaluate treatment effects on growth performance and dietary NE. In Trial 2, three Holstein steers (448 +/- 21 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on characteristics of digestion. Increasing the FFB did not affect (P>0. 10) ADG, but decreased gain efficiency (linear effect, NO. 05) and dietary NE concentration (linear effect, NO. 01). Increasing the FFB did not affect

(P>0. 10) ruminal digestion of starch, N, or microbial N (MN) efficiency, but decreased (linear effect, P0.10) postruminal digestion of OM, starch, and N, but decreased postruminal digestion of fatty acids (linear effect, NO. 05). Increasing the FFB did not affect (P>0. 10) percentage of total tract starch, N, and ADF digestion, but decreased the percentage of total tract digestion of OM (linear effect, P15%, dietary NE and, hence, BW gain efficiency may decrease. The magnitude of the effect of FFB inclusion rate on energy recovery is a predictable function of the relationship between fatty acid intake and intestinal fatty acid digestion.

(Key Words: Feedlot Diets, Fat, Forage, Performance, Digestion.)

Introduction

The tabular NE^sub m^ and NE^sub g^ values of fat are 6.00 and 4.50 Mcal/kg, respectively (21). However, these values are considered valid only when the level of fat intake is low [

Results and Discussion

Implications

A FFB comprised of 80% alfalfa hay and 20% yellow grease can replace steam-flaked wheat at up to 45% of the DM in growing-finishing diets for feedlot cattle without affecting daily BW gain. However, at dietary inclusion rates >15%, dietary NE and, hence, feed efficiencies are decreased. The magnitude of the decrease in energy recovery is a predictable function of the relationship between fatty acid intake and intestinal fatty acid digestion. More work is needed to evaluate treatment effects on digestive function and growth performance when using a grass hay as the forage source in the FFB.

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A. PLASCENCIA* and R. A. ZINN^,1, PAS

Instituto de Investigaciones en Ciencias Veterinarias, Universidad Aut6noma cle Baja California, Mexicala, Mexico; ^Desert Research and Extension Center, University of California, El Centro, CA 92243

1To whom correspondence should be addressed: razinn@ucdavis.edu

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