Clinical biochemical reference ranges for female alpacas (Lama pacos)

Energy metabolism and methane production in llamas, sheep and goats fed high- and low-quality grass-based diets

This study aimed to test whether the digestive and metabolic characteristics of pseudo ruminants provide superior ability to utilise low-quality diets compared to true ruminants. A total of 18 mature, non-pregnant, non-lactating female animals, including six llamas (Lama glama), six Danish Landrace goats and six Shropshire sheep, were used in a crossover design study. The experiment lasted for two periods of three weeks. Half of the animals were fed either high-quality grass hay (HP) or low-quality grass seed straw (LP) during each period. Animals were placed in metabolic cages during the last 5 d, and gaseous exchange was measured by open-circuit indirect calorimetry for 22 h. Metabolisable energy for maintenance (MEm) and fasting energy expenditure (FEExp) were estimated by regression approach. Dry matter (DM) intake per kg(0.75) was substantially reduced in llamas and sheep, but not in goats, on the LP compared to HP diet. Llamas had lower daily energy expenditure (324 kJ · kg(-0.75)) than sheep (416 kJ · kg(-0.75)) and goats (404 kJ · kg(-0.75)) on the LP diet. Llamas in comparison with sheep and goats had lower methane emission (0.83 vs 1.34 and 1.24 l · d(-1) · kg(-0.75), p < 0.05), lower MEm (328 vs 438 and 394 kJ · d(-1) · kg(-0.75), p < 0.05) and lower FEExp (246 vs 333 and 414 kJ · d(-1) · kg(-0.75), p < 0.05), respectively. In conclusion, llamas had lower basal metabolic rate and hence maintenance requirements for energy.

Reference intervals for hematologic and coagulation tests in adult alpacas (Vicugna pacos)

BACKGROUND

Species-specific reference intervals are needed for interpretation of laboratory tests. Reference interval studies of alpacas have been limited by low numbers and use of outdated methods.

OBJECTIVES

The aims of this study were to establish reference intervals for hematologic and coagulation tests in alpacas using a laser-based hematology analyzer and a mechanical clot detection coagulation analyzer, respectively; to compare results for automated and manual differential WBC and platelet counts and fibrinogen concentrations; and to examine the effect of herd and sex on hematologic tests in a population of alpacas.

METHODS

Blood collected from clinically healthy female and male adult alpacas (Vicugna pacos) from 5 herds underwent full CBC analysis using an ADVIA 2120 (n = 65). Blood smears were examined for manual differential WBC counts, platelet estimates, and morphologic examination of blood cells. PCV and plasma protein and heat-precipitable fibrinogen concentration measured by refractometry were also determined. Partial thromboplastin time, prothrombin time, and clottable fibrinogen concentration were measured using a STA Compact analyzer (n = 13). Reference intervals were established using 2.5th and 97.5th percentiles for hematologic analytes and minimum and maximum values for coagulation tests. Automated and manual differential WBC counts, platelet counts, and fibrinogen concentrations were compared. Results were also evaluated for herd- and sex-associated effects.

RESULTS

Hematologic reference intervals for alpacas were similar to those reported previously, except for lower RBC-related results, which showed a herd bias. Correlations between automated and manual neutrophil, lymphocyte, eosinophil, and platelet counts were moderate to good, with weak to poor correlations for monocyte and basophil counts and fibrinogen concentrations. Owing to the low number of samples analyzed, reference intervals for coagulation tests should be considered estimated intervals.

CONCLUSIONS

Reference intervals will be useful guides for interpreting hematologic and coagulation results in alpacas, particularly when using the same instrumentation and reagents.

Direct colloid osmometry in healthy New World camelids

BACKGROUND

Direct colloid osmometry provides an objective assessment of the oncotic effects of crystalloid or colloidal fluid therapy, which is especially useful in monitoring fluid therapy of critically ill camelids due to their tendency toward nonspecific hypoproteinemia with increased risk of developing edema and ascites.

OBJECTIVES

The aims of this study were to measure colloid osmotic pressure (COP) of alpacas and llamas, determine its correlation with concentrations of total protein (TP) and total solids (TS), as well as both albumin (A) and globulin (G) concentrations in the same model (A+G), and evaluate the effects of sample type and storage conditions on COP.

METHODS

Blood was collected from clinically healthy alpacas (n=23) and llamas (n=22) into heparin tubes. COP of fresh whole blood (COP(FB) ) and plasma (COP(FP) ) was determined using a membrane osmometer. For 20 alpacas, COP of refrigerated whole blood (COP(RB) ) and frozen plasma (COP(FrP) ) was also measured. Correlations between COP(FB) and TS, TP, and A+G concentrations were assessed by simple and multiple regression analysis to model potential predictors.

RESULTS

Median COP(FB) from alpacas (24.6 mmHg, range 19.3-28.1) was not significantly different from that of llamas (25.3 mmHg, range 22.5-33.7). Sample type or storage conditions did not affect COP. Measured COP had a strong positive linear correlation with TS, TP, and A+G concentrations in alpacas (r(2) =.7, .74, and .88, respectively). In llamas, COP correlated best with TS concentration (r(2) =.59), whereas correlation with TP and A+G concentrations was poor (r(2) =.19 and .25, respectively).

CONCLUSION

COP can be measured using heparinized whole blood or plasma, either fresh or stored. Direct measurement is recommended whenever quantitative knowledge of COP is required in clinical or research setting. Further studies are needed to verify if the poor association of COP with TP found in this study can be generalized to llamas.