Effects of Varying Forage Source in a Concentrate Diet on the Metabolism and Apparent Retention of Crude Protein by Lambs

Abstract

Twenty-one Rambouillet wether lambs (average initial body weight (BW) = 41 kg) were used in a metabolism trial to evaluate the digestibility of three different concentrate diets each containing one of the following: alfalfa pellets (Medicago sativa L.), bermudagrass-clipping (Cynodon dactylon L.) pellets, or Coastal bermudagrass hay (Cynodon dactylon L.) pellets.  Treatments were arranged in a completely randomized design for dry matter intake (DMI), fecal excretion, and dry matter digestibility (DMD) using analysis of variance.  Analysis of covariance was used for N intake, (g/d), fecal N, (g/d), fecal N, (% of intake), urinary N, (g/d), urinary N, (% of intake), N absorbed, (g/d), % N absorbed, N retained, (g/d), and N retained, (% of intake).  Prior to the study, lambs were housed in pens and fed the control diet containing alfalfa pellets.  A five day adaptation period was followed by a seven day collection period.  Intake by lambs was limited to 2.5% of BW.  Dry matter intake and dry matter digestibility were not different (P > .05) among treatment groups.  Nitrogen intake, apparent absorption, and apparent retention expressed as percent of intake and g/d did not differ among lambs fed their diets.  Initial weight was used as a covariate in the N data to account for any unwanted variation within treatment groups.  Based on the absorption and retention data, bermudagrass-clipping pellets are an adequate forage source at 10% of the diet for lambs on a concentrate diet.