Objective.

To quantify the concentration and consumption of the protein fragments (NPN, TP, RDTP, SDTP, NDIP, and ADIP) present in the diet supplied to cattle, and its effect on the digestibility of crude protein.

Materials and methods.

Diets offered to Chino Santandereano cattle in stables were analyzed, receiving different levels of supplementation, using four animals in the 4x4 Latin square outline, the treatments being: NS, not supplemented; LOW, supplemented with an amount relative to 0.5% of body weight; MEDIUM, supplemented with an amount relative to 1.0% of body weight; HIGH, supplemented with a quantity relative to 1.5% of body weight. Consumption was determined daily, and digestibility through total stool collection in the last two days of each period.

Results.

A higher concentration of crude protein was found in supplement compared to grass (p<0.001), the forage exhibiting a higher concentration of CPNPN (p<0.001), at the same time, that the supplement presented higher concentration of TP (p<0.001) and RDTP (p=0.027). Supplemented animals presented higher consumption of CP, CPNPN (p=0.037), TP, NDIP, RDTP, ADIP and SDTP (p<0.05), however, when the concentration that represents the consumption of ADIP in the consumption of CP was determined, no difference was observed between supplemented and NS (p=0.078). Higher digestibility of CP was found in supplemented animals when contrasted with NS (p<0.001), an upward linear effect was observed between supplemented treatments as the level of supplementation increased.

Conclusions.

Supplementation improves the digestibility of crude protein by providing a greater amount of highly digestible nitrogenous fragments.

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