Undegradable dietary protein in alpaca diets affects fibre diameter and time spent urinating

Abstract

There is evidence that alpacas derive most of their glucose for energy from the deamination of amino acids. Consequently, they may have an insufficient supply of amino acids to meet their requirements for fibre growth. To optimise fibre production, it may be necessary to supply alpacas with supplemental protein to meet their requirement for extra amino acids. In this study, we examined if the proportion of rumen-degradable dietary protein (RDP) to undegradable dietary protein (UDP) from canola meal influenced the fibre growth of alpacas. We hypothesised that alpacas fed at maintenance a diet containing canola meal protein high in UDP would produce more fibre and spend less time urinating than peers fed a similar amount of canola meal protein with a low proportion of UDP. Four groups of eight alpacas were fed diets with the following ratios of UDP : RDP: 0 : 100, 30 : 70, 60 : 40 or 100 : 0 from canola meal protein. The fibre growth of the animals was measured over 2 months and the behaviour of the animals in the two extreme groups (0 and 100% UDP) was measured over 5 days. The alpacas fed the 0% UDP diet produced fibre of finer diameter than the alpacas fed diets containing higher levels of UDP (P = 0.039) and the 0% UDP group also spent more time urinating (P = 0.027). This result suggests that alpacas may have a limited ability to recycle nitrogen to the fermentative chambers of their stomach when fed a diet low in UDP. Consequently, microbial protein synthesis in the fermentative chambers may have limited the supply of amino acids available to the alpacas.