EFFECT OF DIETARY ROUGHAGE AND PHOSPHORUS LEVELS ON MINERAL ABSORPTION AND UTILIZATION BY SHEEP

HENRIQUE OTAVIO DA SILVA LOPES, Purdue University

Abstract

The metabolism trial (18-day adjustment period, 7-day collection) was conducted with sheep to investigate the effects of phosphorus and roughage dietary levels upon phosphorus, calcium, magnesium, potassium, and nitrogen balance. Thirty-six lambs (rams) were randomly assigned to nine treatment groups in a 3 x 3 factorial design with three levels of phosphorus (0.120, LP; 0.240, MP; 0.480%, HP) and three levels of roughage as corn cobs (25%, LR; 50%, MR; 75%, HR). Interaction between phosphorus and roughage was observed on apparent phosphorus digestibility and percent of dietary phosphorus retained (P < 0.01). Phosphorus balance, percent dietary phosphorus retained and apparent phosphorus digestibility were higher (P < 0.01) for animals fed the MP and HP diets as compared with the animals fed the LP diet. Blood serum phosphorus levels increased (P < 0.01) with each increment of dietary phosphorus. Phosphorus balance, percent of dietary phosphorus retained and apparent phosphorus digestibility decreased significantly as the dietary roughage levels increased. There was an interaction between phosphorus and roughage on urinary calcium excretion (P < 0.01). Calcium balance and apparent calcium digestibility were lower (P < 0.01) for the lambs fed the HP diet as compared with those fed the LP and MP diets. Blood serum calcium and magnesium levels decreased significantly as the dietary phosphorus levels increased. Urinary magnesium excretion (gm/day) and blood serum magnesium levels were significantly affected by an interaction between phosphorus and roughage. Apparent magnesium digestibility was lower (P < 0.05) for the lambs fed the HP diet as compared with those fed the LP and MP diets. Potassium balance increased significantly with each increment of dietary roughage whereas percent of dietary potassium retained was higher (P < 0.01) for the lambs fed the HR diet as compared with those fed the LR and MR diets. Urinary nitrogen and apparent nitrogen digestibility were significantly affected by an interaction between phosphorus and roughage. Percent of dietary nitrogen retained was higher (P < 0.05) for the animals fed the MP ration as compared with the animals fed the HP ration. Apparent nitrogen digestibility was lower (P < 0.0) for the lambs fed the HR diet as compared with those fed the LR and MR diets.

Degree

Ph.D.

Subject Area

Livestock

COinS