M 0 usa H. M.: Ruminal and blood characteristics of Nubian goats dosed with the growth promoter monensin. Acta vet. BrilO, 63, 1994: 13-17. • Twelve cannulated male growing bucks (goats) were used in a 56-day study to determine the effect of monensin on ruminal and blood characteristics on animals receiving 10 mg of monensin solution daily through the rumen cannula. There was slight increase in body weights of treated animals. Monensin increased significantly (P<O.OOI) the level of blood glucose and decreased (p<O.OOl) the concentration of plasma lactic acid, urea and magnesium. Serum albumin, cholesterol, sodium, chloride, potassium and calcium were not affected after treatment. In the rumen fluid, there was a significant decrease in rumen ammonia (P<O.OOI), the molat proportion of acetic acid (P<O.OOI) and acetate: propionate ratio (P<O.05). A significant increase (P<O.OOI) in the level of propionic acid was detected. Other volatile fatty acids and the pH of the rumen were not affected. Monensin, growth promoter, Nubian goats, biochemical parameters Monensin is a biologically active compound produced by the fungus Streptomyces cinamonensis.1t is a Catboxylic polyether ionophore. It is classified as an ionophore because it facilitates transport of monovalent cations across membranes (Pressman 1976). Monensin was found to alter rumen fermentation and increase the efficiency of feed utilization by growing and finishing cattle (potter etal.1976;Boling etal.1977;Dinius and Baile 1977). The change in the fermentation pattern is brought about by the fact that monensin changes the rumen ecology. It enhances the growth of some microorganisms and inhibits the growth of others, this in tum changes the concentration of the products of fermentation towatds a more beneficial effect to the host. Although monensin is extensively used in Europe and the United States, as a feed additive, it has not been introduced in this country before. As part of an extensive study in the use of monensin as growth promotor for local breeds of ruminants in this country, the present work aims at investigating the basic biochemical changes, reported as associated with monensin in cattle, in young growing goats in the Sudan. Materials and Methods Animals and feed Twelve healthy Nubian bucks (Capra hircus), aged 5-7 months and weighing 10-15 kg, were fitted with rumen cannulae and housed in sepatate pens. Throughout the experimental period, the animals were fed on mature dry Abu-70 forage (Sorghum vulgaris, Vat.). Samples of Abu-70 analysed for chemical composition according to the A. O. A. C. (1970) contained (on DM basis) 5.2 % CP (0.83 % N), 1.8 % EE, 25 % CF and 8.1 % ash. Water and food were available ad libitium. Experimental procedure The animals were kept for two weeks of adaptation period before the start of the experiment. The experiment began by dividing the animals into two groups, six each, group C (control) and group M (treated with monensin). The sodium salt of monensin (crystalline potency 885 mglkg), obtained from Lilly Research Centre, England), was suspended in water and each animal in group M received an equivalent of 10 mg monensin daily through the rumen cannula for 56 days. At the end of the treatment period, blood (10 rnl) was collected into heparinized tubes. Plasma was collected by centrifugation of the blood at 900 g for 10 minutes, then stored at -20°C, pending analysis. Another blood sample was collected from the opposite jugulat vein for serum preparation. Rumen fluid was obtained by a syringe fitted with a rubber tubing and inserted through the cannula. Rumen fluid (5 rnl) was sucked from each animal and transferred to small vials, containing 0.5 rnl formic acid as preservative, for determination of volatile fatly acids (VFA). Another rumen sample was collected for the other determinations. Body weights were recorded at the start and at the end of the experimental period. Food intake was also observed.