Design, operation, and validation of metabolism crates for nutrition studies in alpacas (Vicugna pacos)

Metabolism studies in farm animals require reliable measurements of feed intake and water consumption, as well as the accurate collection of feces and urine. When designing metabolism crates, aspects such as: animal behavior, minimization of injury risks, and animal cleanliness should be considered. In the present study, morphometric measures taken from 30 Huacaya male alpacas (five years old) were the basis for designing an initial prototype of metabolism crates, which was built largely of metal for strength and durability, and has replaceable parts. Two of these metabolism crates were built and tested with experimental animals sequentially allocated in pairs during five days each. Based on the observed performance, both length and width of metabolism crates were adjusted (2.00 × 0.55 m respectively) for an up-graded design, which was tested during the validation phase. These features provided greater comfort and ease of handling of the experimental animals. Metabolism crates are illustrated by photos and drawings, which give dimensions and details of construction. At the end, five units were built. Validation of metabolism crates comprised the evaluation of animal performance of five alpacas fed at maintenance level of intake in terms of: daily feed intake and water consumption, fecal and urine excretion, and diet digestibility over a two-week experimental period. Data were analyzed by descriptive statistics. Overall, both dry matter intake per kg of metabolic body weight (DMI: 42.7 ± 1.29 g/kg BW0.75), and water consumption (100 ± 7.1 ml/kg of BW0.75), which was equivalent to 2.3 times the observed DMI (kg/d), were in line with a number of previous studies conducted with alpacas for this feeding regime. Due to differences mainly related to diet composition, direct comparisons with studies in the literature in terms of fecal production and diet digestibility are difficult to draw. However, these results appear to be in line with expected performance for the given diet (70:30 oat hay and alfalfa pellets on a fed basis). Same applies to urine volume (428 ± 34.2 ml/d), which in the present study represented 19% of the daily water consumption. It is concluded that proposed metabolism crates are suitable for conducting nutritional studies with alpacas.