Influence of Dietary Undegraded Crude Protein on Intake, Nitrogen Partitioning, and Apparent Organic Matter Digestibility in Alpacas

The present study evaluated the influence of three dietary levels of undegraded crude protein in the fermentative compartment (UDCP) on intake, fecal and urinary excretion, nitrogen partitioning, and apparent organic matter digestibility in alpacas. Eight male alpacas were assigned to low (14% crude protein), medium (24% crude protein), and high (34% crude protein) UDCP treatments in an incomplete and unbalanced 3-period crossover design using isoproteic and isoenergetic diets. No differences were observed among treatments in dry matter intake, organic matter intake, fecal excretion of dry matter, organic matter, and nitrogen; nitrogen retention; or apparent organic matter digestibility. In contrast, water intake, nitrogen intake, urinary nitrogen excretion, nitrogen absorbed, and nitrogen efficiency ratios were influenced by UDCP treatment. The high UDCP treatment was characterized by lower urinary nitrogen losses and a higher proportion of retained nitrogen relative to absorbed nitrogen compared with the low UDCP treatment, despite similar nitrogen intake. Conversely, the low UDCP treatment promoted higher nitrogen absorption but was associated with greater urinary nitrogen excretion and a lower retention-to-absorption ratio. Overall, these results indicate that increasing the dietary contribution of UDCP reduces post-absorptive nitrogen losses in alpacas, thereby improving nitrogen utilization efficiency relative to low UDCP diets.