ANDREAS JENET, MATTHIAS SAURER, SALVADOR FERNANDEZ-RIVERA, AZAGE TEGEGNE, HANS-RUDOLF WETTSTEIN, MICHAEL KREUZER
Swiss Federal Institute of Technology (ETH), Institute of Animal Science, Switzerland
Paul Scherrer Institute, Villigen, Switzerland
International Livestock Research Institute (ILRI), Ethiopia
Knowledge of composition of fat, protein and water in the body is indicative for the determination of effects of changes in nutrition in terms of body reserves. Deuterium oxide dilution technique has been proposed as easy, reliable and non-destructive method of determining body composition using the ratios of protein:water and mineral:water to predict fat.
Twenty Bos indicus (Boran) and 21 BoranHolstein have been exposed for 4 years to calculated energy requirements for maintenance (M) (low) or M 20% (medium) and M 40% (high). In the third lactation these treatments were sub-divided into either low or high feeding level. Before deuterium application animals were weighed and a blood sample was collected from the jugular vein. Deuterium was slowly administered at 0.3 g/kg fasted body weight, directly into the jugular vein and the syringe was rinsed with refilled blood. Blood samples were taken at 5, 7, and 9 h post infusion and deuterium concentrations in plasma were analysed using isotope mass spectroscopy (3960 nm against water). The gastrointestinal tract (GIT) of the cows was assumed to amount to 0.20 of body weight (BW), and empty body weight (EBW) was described as . Body composition was estimated in the following equations:
Empty body water (kg) = 0.4717BW (kg) + 0.1536DO-space (kg) - 25.046
Empty body ash (kg) = 0.0363BW (kg) + 0.0231DO-space (kg) - 5.755
Empty body protein (kg) = 0.1624BW (kg) + 0.0165DO-space (kg) - 11.488
Empty body fat (kg) = 0.3790BW (kg) - 0.2955DO-space (kg) - 42.163
Previous feeding level and the genotype explained most of the differences between treatment groups. Boran cows showed higher levels of fat, but the difference of 20% and 40% of the previous medium and high treatment was still visible. Fat reserves from the crossbred cows were strongly influenced by milk production, however, crossbreds previously on low plane of nutrition replenished their fat deposits instead of producing more milk when receiving higher amounts of feed.
Keywords: Body composition, carry over, deuterium, undernutrition, zebu