SHIMELS WASSIE, JOAQUÍN CASTRO-MONTOYA, TIAGO MACHADO, AMERICO GARCEZ NETO, UTA DICKHOEFER
University of Hohenheim, Inst. of Animal Production in the Tropics and Subtropics, Germany
Federal University of Parana, Laboratory of Animal Nutrition, Brazil
The study aimed to evaluate the effect of different carbohydrate and nitrogen (N) supplements on feed intake, nutrient utilisation, and performance of sheep. Twelve male Dorper sheep with a body weight (BW) of 23kg (standard deviation (SD) 2.20) were used. The experimental design was a 4 3 Youden square which consisted of four experimental diets and three 21-d-experimental periods (14 d adaptation and 7 d sample collection). Two carbohydrate sources (whey permeate, corn) and two N sources (protected urea, unprotected urea), which differed in their rate and extent of degradation in the rumen, were combined, resulting in four diets:
1) rapidly degradable carbohydrate with rapidly degradable N source (whey permeate-unprotected urea), 2) slowly degradable carbohydrate and slowly degradable N source (corn"=protected urea), 3) rapidly degradable carbohydrate with slowly degradable N source (whey permeate"=protected urea), and 4) slowly degradable carbohydrate with rapidly degradable N source (corn"=unprotected urea).
Dry matter (DM) intake (), apparent total tract digestibility of DM (), and daily BW gain () were not affected by dietary treatment. Mean daily DM intake (g/kg BW0.75), total tract DM digestibility (%), and daily BW gain (g/kg BW0.75) were 60.4 (SD 3.45), 60.1 (SD 3.17), and 2.0 (SD 6.34), respectively. However, N intake (g/d), urinary and fecal N excretions (% of N intake) and, to some extent, N retention (% of N intake), were affected by carbohydrate source, regardless of N source. Urinary N excretion was significantly reduced (), fecal N excretion was higher, and N retention had a tendency () to increase when sheep were fed a rapidly degradable carbohydrate (whey permeate) compared with corn, regardless of N sources. This implies that sheep receiving whey-permeate-based diets utilised N more efficiently than those sheep receiving diets containing corn. Moreover, the decrease in N excretion with whey permeate may be of ecological significance by potentially reducing the excretion of N into the environment.
Keywords: Carbohydrate, nitrogen metabolism, protected urea, protein, sheep, whey permeate