Abstract :
To determine the effect of barley diets on digestibility, nitrogen balance, and blood metabolites, mature gelded llamas and alpacas
(n = 8; 4 llamas, 36±4 months, 90±10.7 kg; 4 alpacas, 24–36 months, 50±4 kg) were randomly fed 100% barley (B) and 20%
alfalfa/80% barley (BA) hay. Animals were housed in metabolism crates and diets were fed for a 7 days adjustment period followed
by a 5 days collection period. Feed, feed refusal, feces and urine were collected, dried and N content determined by combustion
analysis. Blood samples were collected on day 12 at 30 min intervals over a 6 h period. Plasma was harvested and analyzed for
electrolytes (Na, K, Cl, Ca, Ca2+, P, Mg), metabolites glucose, non-esterified fatty acids (NEFAs), urea N, creatinine, albumin,
total protein (TPP), osmolality (Osm). Plasma glucose, urea N, albumin, osmolality, electrolyte and metabolite levels were similar
between species, and were unaffected by diet. On a metabolic weight basis, only diet was significant for N intake, urinary and fecal
N, and total N excreted. Dry matter intake was not significantly different; however, BA consumption was greater than B, (B) 1272 g
N/day and (BA) 1636 g N/day for llamas, and for alpacas (B) 835 g N/day and (BA) 1034 g N/day, respectively. Nitrogen intake
followed the same pattern, (B) 21.4 g N/day and (BA) 33.9 g N/day, respectively for llamas, and (B) 13.6 g N/day and (BA) 20.6 g
N/day, respectively for alpacas (diet, P < 0.002). Diet affects were significant for urine N excretion (P < 0.02), (B) 11.2 g/day and
(BA) 18.2 g/day for llamas, and (B) 6.8 and (BA) 10.8 g N/day for alpacas. Fecal N excretion was different for diet (P < 0.03), with
fecal excreted N of 9.0 g N/day and 11.9 g N/day for B and BA in llamas, and 5.9 g N/day and 9.1 g N/day for B and BA respectively
in for alpacas, respectively. Nitrogen retention, DM digestibility and N digestibility were unaffected by diet or species. However,
the llamas in this study displayed an increase in nitrogen intake of 64.6% between the B and BA diets with a 381% increase in
N retention. Alpacas increased their N intake by 57.4% when they consumed the BA forage, which only increased N retention by
22.2%. These species differences indicate that alpacas have a lower N requirement to meet metabolic needs than llamas, which are
likely related to the smaller body size of the alpaca. When examining the biological value of N from the respective diets, alpacas
and llamas had a value of 56.2% when consuming barley. The BA diet had a higher biological value of 65.0% in llamas compared
to 57.4% in alpacas. Therefore, on the basis of this study, extrapolations between llamas and alpacas with respect to nitrogen
requirement and balance are not valid.
© 2006 Elsevier B.V. All rights reserved.
