H. K. Henderickx

Effect of Virginiamycin on Carbohydrate and Protein Metabolism in the Rumen In Vitro

The effect of virginiamycin in incubations of rumen fluid with carbohydrate or protein substrate was investigated. In carbohydrate incubations, methane production was partially inhibited while propionate proportions increased. Total microbial growth was slightly decreased, but net microbial growth was considerably lower. Protein degradation was slightly lowered after addition of virginiamycin. These effects were compared with results obtained with other rumen manipulating additives.

Influence of Virginiamycin on the Digestive Physiology in Precaecal Re-entrant Cannulated Pigs

The present experiment was set up to study the effect of Virginiamycin, a nutritional growth promoting antibiotic, on the digestive physiology using precaecal cannulated pigs. The semipurified diet used provided 21% protein and 60% of nitrogen free extract (NFE), 2/3 as starch and 1/3 as lactose. Due the older age of the pigs, the lactose induced some degree of malabsorption as precaecal flow rate of digesta was markedly higher (3.2 kg/d) compared with published data obtained with purified diets without lactose. This was also reflected in the rather low ileal digestibility of the nutrients (%): dry matter 68.6, protein 79.6, fat 78.4 and NFE 75.0. Virginiamycin markedly lowered flow rate (2.2 kg/d) and significantly improved apparent precaecal digestibilities (%): dry matter 74.0, protein 81.4, fat 81.9 and NFE 78.7. The faecal apparent digestibility was comparable with published data. There were no treatment differences indicating that precaecal digestibilities are much more sensitive then faecal ones. In order to explain the differences obtained the mean retention time in the upper intestine was measured. Although significant differences were noted (control: 5 h, Virginiamycin: 6 h) a direct cause-effect relationship was not evident. Also the activity of selected pancreatic enzymes in ileal contents was compared. There were no consistent differences between the two treatments, except for a lower lipase activity during Virginiamycin treatment.

The nutritional mode of action of some feed additives in pigs

THE NUTRITIONAL MODE OF ACTION OF SOME FEED ADDITIVES IN