Evaluation of different inclusions of complexed phosphorus in diets for confined lambs on the in vitro ruminal fermentation profile

Abstract

This study aimed to evaluate different inclusion levels of complexed phosphorus in diets for confined lambs, focusing on the in vitro ruminal fermentation profile. Six concentrations of complexed phosphorus (0.55%, 0.28%, 0.22%, 0.17%, 0.11%, and 0.06%) were tested in comparison to a control diet containing dicalcium phosphate. The analysis considered pH and ammonia nitrogen (N-NH₃) concentrations. The research was conducted using two rumen-cannulated sheep (Santa Inês × Dorper) as rumen fluid donors. The diets consisted of corn silage, ground corn, soybean meal, calcitic limestone, and different phosphorus sources. Final pH values varied little between treatments (5.80 to 5.85), indicating that the inclusion of complexed phosphorus did not significantly alter medium acidity. The highest N-NH₃ concentration (35.24 mg/dL) was observed in the treatment with 0.55% complexed phosphorus, significantly exceeding the control and other treatments. The lowest concentration (27.71 mg/dL) was recorded with 0.06% complexed phosphorus. After 6 hours of incubation, the 0.17% treatment showed the highest N-NH₃ concentration (21.80 mg/dL), while the control with dicalcium phosphate showed the lowest value (14.23 mg/dL). It is concluded that complexed phosphorus, even at lower concentrations, can efficiently replace dicalcium phosphate. The adoption of this phosphorus source may contribute to more sustainable nutrition by optimizing nutrient absorption and reducing phosphorus excretion into the environment.