This study was carried out to evaluate the effects of different phosphorus sources, in diets of growing cattle, on apparent partial and total nutrient digestibility; ruminal parameters; microbial efficiency synthesis and plasma phosphorus. Four Holstein steers weighting 280 kg and implanted with ruminal and duodenal cannulas were used. The experimental design was a 4 × 4 Latin Square and treatments were four supplemental phosphorus sources in the diet as follows: dicalcium phosphate (DP), supertriple phosphate (SP), monoammonium phosphate (MP) and Araxa rock phosphate (ARP). Phosphorus sources did not affect intake, fecal flow, apparent ruminal and intestinal digestibility of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF) and non fiber carbohydrates (NFC). There was a lower phosphorus apparent absorption for ARP, differing of DP and MP. Animals receiving ARP showed higher intake, fecal flow, duodenal flow, ruminal disappearance and total disappearance for fluoride. Animals receiving ARP presented fluoride levels higher than those acceptable to avoid toxicity. Phosphorus sources did not affect plasma phosphorus, nitrogen intake, microbial efficiency synthesis and ruminal bacteria composition. Treatments did not affect ruminal pH and ruminal ammonia concentration. These results show a possible use for supertriple phosphate and monoammonium phosphate to replace dicalcium phosphate.
dicalcium phosphate; monoammonium phosphate; microbial synthesis; rock phosphate; supertriple phosphate
