I. The effects of cadmium and zinc at dietary concentrations typical of those that can arise as a result of adventitious contamination of feedstuffs were investigated. II. Cadmium (1.5 - 18 mg/kg) in the diet of rats induced copper deficiency over a period of 9 weeks when the diet contained 2.6 mg Cu/kg but not when it contained 7.8 mg Cu/kg. III. The effect of cadmium on copper status of rats was due to reduced copper absorption. Cadmium supplementation induced no measurable change in hepatic copper metabolism in rats. IV. Zinc at a concentration of 300-1000 mg/kg diet induced copper deficiency , in rats receiving 2.6 mg Cu/kg diet. The first signs of deficiency (achromotrichia) were evident four weeks after introduction to a diet containing 1000 mg Zn/kg. V. The combined effects of zinc and cadmium on copper status in rats were greater than the effect of zinc or cadmium alone. Zinc supplement ation did not protect rats against the effects of cadmium on copper metabolism. VI. Cadmium and zinc, separately and in combination reduced cortical bone thickness in the femur of rats. VII. Cadmium at a concentration of 3 mg/kg had no detectable effect on pregnant ewes maintained for the last 100 days of pregnancy on a semi-synthetic diet containing 2.5 mg Cu/kg. VIII. Zinc at a concentration of 150 mg/kg in the diet of pregnant ewes had no detectable adverse effects on the health of the sheep. At a concentration of 750 rag/kg diet zinc induced severe copper deficiency in pregnant ewes when the diet contained 2.5 mg Cu/kg. This level of zinc supplementation greatly reduced the viability of perinatal lambs. Increasing the copper content of the diet of ewes receiving 750 mg Zn/kg, from 2.5 to 10 mg/kg prevented the development of copper deficiency in the ewes but did not increase the viability of the lambs. IX. Cadmium (3m g/kg) in the diet of weanling lambs markedly reduced growth rate when the diet contained 2.5 or 4.5 ag Cu/kg. This effect of cadmium was partially alleviated by a dietary zinc concentration of 150 mg/kg. Low growth rate in the cadmium supplemented lambs was not a result of cadmium-induced copper deficiency although an increase in dietary copper concentration from 4.5 to 15 mg/kg stimulated growth rate. Cadmium reduced the activity of cytochome oxidase in the duodenal mucosa and this may have been responsible for the very low growth rate of these animals. Over a period of approximately 10 months cadmium (3 mg/kg diet) reduced the thickness of cortical bone in lambs. Over this period, the cadmium concentration of liver and kidney rose to a level at which they would probably be considered unfit for human consumption. X. Contrary to the findings of other workers, zinc at a concentration of 150 mg/kg diet induced rapid accumulation of copper in liver when the copper concentration in the diet of lambs was raised from 4.5 tolS.O mg/kg. This level of zinc was associated with an increase in the proportion of soluble hepatic copper bound to a protein fraction similar to metallothionein. The proportion of soluble hepatic copper located in this fraction was greatest when the diet was supplemented J with both zinc and cadmium. The accumulation of copper in sheep receiving 150 mg Zn/kg diet was indicative of derranged copper metabolism as copper accumulation was associated with increased hepatic iron concentration and reduced hepatic cytochrome oxidase activity. In calves maintained on a diet containing an adequate concentration of copper (12.5 mg/kg), cadmium at concentrations of 2.0 and 4;0 mg/kg prevented hepatic copper accumulation. When the copper concentration of the diet was reduced from 12.5 to 8 mg/kg, cadmium reduced the efficiency of feed utilization, induced iron accumulation in duodenal mucosa and liver, and caused changes in bone conformation similar to those observed in copper deficiency. Significant changes in liver copper concentration were not observed, however.

No description available.

No description available.

A comparison of various parameters for estimating the extent of the microbial deterioration of hay was made, these parameters being viable microbial counting by dilution plate and air sampling techniques, viable and non-viable microbial material estimates by chitin and diaminopimelic acid level determinations and finally temperature measurements. The inhomogenous nature of hay created considerable sampling errors and it was therefore concluded that heat production, expressed as degree days, was probably the most convenient measure of microbial activity. A microbial succession was found to occur in deteriorating hay which frequently caused two separate heating phases, and it was concluded that in the first phase readily available nutrients were utilised and the second phase was due to microbial metabolism of nutrients produced by extra cellular enzymes especially cellulases. Several chemicals and chemical mixtures were assessed as hay preservatives by three methods. Firstly, using chemically defined agar media buffered at p.H values of 5, 6, 7 and 8. Secondly, by their application to re-wetted hay stored in dewar flasks and thirdly by their application to hay at baling. It was found that higher levels of these chemicals were needed on hay, than in agar media, to inhibit microbial growth and certain compounds, e.g. formaldehyde, were inactivated on hay. Also the minimum effective levels of preservative were found to increase with an increase in the moisture content of the hay and it was concluded that propionic acid was the most practical preservative, the addition of sorbic acid possibly being of some benefit. There appeared to be three problems concerned with the chemical preservation of hay. Firstly, poor preservative distribution, secondly preservative loss by evaporation and microbial degradation and thirdly a lack of information relating the minimum effective levels of preservative with nutrient and water content or, probably more important, the water activity of hay. Possible means of overcoming these problems are discussed.

No description available.

No description available.

A series of experiments were conducted to ascertain the effects of sex conditions, slaughter weight, environment and sire performance on the growth and carcass composition of Welsh Mountain lambs. Entire lambs reached target slaughter weight 28.5 days earlier than castrates. Killing our percentage was higher in castrates regardless of rearing environment and they yielded significantly greater carcass weights than entires. Estimated lean and fat percentages showed entire animals to have greater lean and less fat than castrates. Increases in slaughter weight resulted in significant increases in fat percentage with a corresponding decrease in lean percentage. Progeny testing of high and low performance tested rams was carried out to assess their influence on liveweight growth and carcass composition of entire Welsh Mountain lambs. Ram lambs were reared on the ffridd. High progeny reached slaughter weight on average 30 days earlier than the progeny of low rams. Killing out percentage and cold carcass weights were significantly higher in low performance progeny. However, high progeny had significantly greater lean and less fat percentage in their carcasses. Ewe lambs reared on the open mountain also showed that progeny of high rams grew at a faster rate than progeny sired by low rams. When ram lambs were individually penned indoors it was found that the progeny of high sires had greater liveweight gain than low progeny whilst feed intake was similar for both groups, as a result feed conversion efficiency was better in progeny of high performance rams. Wool samples taken from ewe lambs were compared but no consistent differences could be detected in any wool characteristics. The results suggest that Welsh Mountain lambs if reared as entires could be taken to heavier slaughter weights than is normal, with no adverse effect on carcass composition. Progeny sired by rams who perform well on performance test grew faster and at the same slaughter weights produce leaner carcasses than progeny sired by low performance sires.

Watershed degradation and the conversion of wetlands to alternative uses affect water quality, having profound implications for the freshwater ecosystem and fisheries of Lake Victoria. Through dynamic simulations using the Ecopath approach we show that eutrophication may explain the sudden upsurge of the introduced Nile perch during the 1980s. During these years an important trigger of change was an abrupt shift in primary productivity due to an external shock, probably related to an El Nino-ENSO event. The Nile perch population explosion during the 1980s caused a profound transformation ofthe fishing industry leading to a dramatic increase in fishing effort. Our equilibrium analysis from the base values of an Ecopath mo~l for year 1989 depicts an overfishing situation. To quantify the combined effect of eutrophication and fishing effort on the-aggregate fish stock and fishery we specify and estimate a biomass dynamics model, which embeds a measure of phytoplankton biomass as an environmental variable. We found that in a eutrophic state, which for the Kenyan waters of Lake Victoria was above an estimated chlorophyll-a concentration threshold of 17.11 mg m-3 , a further increase in phytoplankton biomass would cause a decrease in aggregate fish stock biomass and landings respectively. We then model the relation between land use change and water quality, considering the nutrient retention function of wetlands. First, we identify catchment-based indicators, in particular price indicators and wetland extent, which may anticipate changes in ,. environmental variables driving stock assessment models. We then study both nutrient loading and wetland reclamation externalities to the fishery sector, focusing on the Yala swamp, one of the largest wetlands in the Kenyan basin of Lake Victoria. Finally we propose a spatially distributed land use tax as policy instrument for reaching the desired objective of changing farmers' behaviour and maximising the total economic benefit to society.

Kocuria SM1 and Rhodococcus SM2 were administered to juvenile rainbow trout as dietary supplements dosed at ~107–108 cells g−1 of feed for two weeks, and conferred protection against Vibrio infections. Thus, use of SM1 and SM2 led to a significant (P < 0.05) reduction in mortalities, i.e. 12–15% (relative percent survival, RPS = 81– 85%) and 15–20% (RPS = 73–80%) after challenge with V. anguillarum and V. ordalii, respectively, compared to the 80% and 74% mortalities among the respective controls. A two-week feeding regime, compared with 1–4 weeks, for SM1 led to the maximum reduction in mortalities after challenge with V. anguillarum. The use of an equi-mixture of SM1 and SM2 led to significantly enhanced survival against vibriosis, but the result was not better than the use of single cultures. Moreover, use of SM1 for two weeks led to protection for up to 4 weeks. Fish inoculated with cell wall proteins (CWPs) and whole cell proteins (WCPs) of SM1 and SM2 demonstrated better protection against challenge with V. anguillarum, although extracellular proteins (ECPs) fared less well. The mode of action reflected competitive exclusion (= antibiosis), nutrition (= positive effects on growth), and stimulation of cellular and humoral innate immunity, notably greater head kidney macrophage phagocytic, respiratory burst, peroxidase and bacterial killing activities, and elevation of leucocytes, globulin, protein, complement and lysozyme levels. These results demonstrate the efficacy of dietary bacteria as probiotics for the control of vibriosis in rainbow trout.

Five years' data of the Beluga, <I>Huso huso, </I>Stellate Sturgeon, <I>Acipenser stellatus</I>, Persian Sturgeon, <I>A. persicus</I> and Russian Sturgeon, <I>A. guldenstadti</I>, in the southern Caspian Sea were analysed for sex and age, and length and weight composition. The von Bertalanffy growth parameters, and total, natural and fishing mortalities were estimated. Yield-per-recruit curves were derived from each species, based on growth parameters and mortality rates, and the optimum fishing mortality in terms of yield-per-recruit was calculated as a basis for sturgeon fishery management in the Caspian Sea. Age of the sturgeons was determined from the fin ray sections. In all five years, for all the species, there were more females than males in the catches. Catches of fish older than 20 years were a very low percentage. Von Bertalanffy growth parameters for each species were estimated for sexes separately. For female Beluga, the values of L<SUB>∞</SUB> and K were estimated for three growth stanzas as 320 cm and 0.065 for juveniles, 450 cm and 0.029 for the middle stanza and 533 cm and 0.023 for older fish. For male Beluga and other species the values of L<SUB>∞</SUB> and K were estimated both from L<SUB>max</SUB> and by using the Fishery Science Application System (FSAS) computer program. L<SUB>∞</SUB> and K for male Beluga were estimated as 270 cm and 0.086 using L<SUB>max</SUB>, 302 cm and 0.072 using FSAS. For female Stellate Sturgeon L<SUB>∞</SUB> and K were 213 cm and 0.062 using L<SUB>max</SUB>, 188 cm and 0.104 using FSAS; and for males 190 cm and 0.083 from L<SUB>max</SUB>, 171 cm and 0.113 by FSAS.