Body composition: the precision and accuracy of new methods and their suitability for longitudinal studies

The effect of supplementation on productive performance of Boer goat bucks fed winter veld hay

Fifteen Boer goat bucks, (6-8 months old), were allocated into two groups and fed ad libitum for a period of 29 days. The WH group (winter hay; n = 8) received a chopped diet consisting of grass hay, predominantly Themeda trianda grass (cut during the winter) from a natural pasture (veld). The WH+S group (winter hay plus supplement; n = 7) received a chopped diet consisting of Themeda trianda veld hay, supplemented with maize meal, molasses meal and urea. Body weights and feed consumption were recorded. Animals were slaughtered and carcass characteristics (weight and percentages of selected carcass cuts) and the carcass chemical composition were determined. The WH+S animals showed a higher live weight and cumulated feed intake. Carcass cuts from WH animals represented a higher percentage of the total carcass, especially cuts where muscle depots are higher (legs, best end chops and prime cuts). There is an attempt by non-supplemented animals to preserve the body's nitrogen reserves under prolonged nutritional stress conditions, and there is consequently a necessity to supplement feeding of small ruminants fed winter veld hay, especially if the animals are to be used in subsequent breeding seasons.

High-resolution magnetic resonance imaging tracks changes in organ and tissue mass in obese and aging rats

Magnetic resonance imaging (MRI) has the ability to discriminate between various soft tissues in vivo. Whole body, specific organ, total adipose tissue (TAT), intra-abdominal adipose tissue (IAAT), and skeletal muscle (SM) weights determined by MRI were compared with weights determined by dissection and chemical analysis in two studies with male Sprague-Dawley rats. A 4.2-T MRI machine acquired high-resolution, in vivo, longitudinal whole body images of rats as they developed obesity or aged. Weights of the whole body and specific tissues were determined using computer image analysis software, including semiautomatic segmentation algorithms for volume calculations. High correlations were found for body weight (r = 0.98), TAT (r = 0.99), and IAAT (r = 0.98) between MRI and dissection and chemical analyses. MRI estimated the weight of the brain, kidneys, and spleen with high accuracy (r > 0.9), but overestimated IAAT, SM, and liver volumes. No differences were detected in organ weights using MRI and dissection measurements. Longitudinal MRI measurements made during the development of obesity and aging accurately represented changes in organ and tissue mass.