Excretal Near Infrared Reflectance Spectrometry to monitor the nutrient content of diets of grazing young ostriches (Struthio camelus)

Abstract

Feeding systems in which young ostriches feed on pasture but have access to concentrates provide better welfare than confined systems but are sustainable only if nutrition is carefully controlled. This study was conducted to evaluate the potential of "excretal NIRS", a methodology that associates excretal spectral information in the near infrared (NIR) region with dietary attributes, in predicting dietary quality and nutrient intake in grazing ostrich chicks. Sixty sets of excretal and dietary information from chicks fed only concentrate or also grazing lucerne, barley, sulla or natural pastures, were used. The coefficient of determination (R²) and the standard error of cross validation (SECV) served to evaluate calibration quality. The prediction of dietary concentrate content ranging 420 to 1000 g/kg of DMI, was highly linear (R² = 0.96), with SECV of 63 g/kg. Similar R² values were noted for the dietary contents of crude protein (CP), acid detergent fibre (ADF) and ash; that for the prediction of neutral detergent fibre (NDF) was lower (0.87). Ash, CP, NDF and ADF were predicted with SECV values of 14.8, 5.0, 8.9 and 10.7 g/kg DM diet, respectively. The calibration for apparent total organic matter digestibility was of poor quality. Good (R² = 0.95) and acceptable (R² = 0.86) calibrations were obtained for the daily intakes of pasture and concentrate, respectively, with SECVs of 75 and 131 g/d. Predictions of ash (R² = 0.85, SECV = 11 g/d) and ADF (R² = 0.80, SECV = 19 g/d) intakes had mediocre accuracy, and calibrations for CP and NDF intakes were even poorer. These results suggest that excretal NIRS may be useful to predict dietary intake and composition for grazing ostriches when applied to a known nutritional environment attended with calibration standards.

Keywords: Ratites, faecal NIRS, nutrition; pasture, herbivory

South African Journal of Animal Science Vol. 36 (4) 2006: pp. 248-256