Risks connected with the use of conventional and genetically engineered vaccines.

A review is given of real and potential risks connected with the use of conventional and genetically engineered live and dead vaccines. Special attention is given to live carrier vaccines expressing one or more heterologous genes of other microorganisms. Because most carrier vaccines are still in an experimental phase, there is only limited experience with the risks of carrier vaccines. There are three potential risks of live carrier vaccines which will be discussed: 1. Changes in cell, tissue, of host tropism, and virulence of the carrier through the incorporation of foreign genes. 2. Exchange of genetic information with other vaccine or wild-type strains of the carrier organism. 3. Spread in the environment. Only limited experimental data are available on changes in biological behaviour of microorganisms through the incorporation of foreign genes. For example, there are indications that vaccinia virus carrying the attachment protein G of respiratory syncytial virus (RSV) replicates better in lungs of mice than vaccinia virus carrying other genes of RSV. Poxviruses carry genes that probably determine their replication in different hosts. Exchange of such host tropism genes might alter their host spectrum. Recombination between herpesvirus vaccine or wild-type strains may lead to the appearance of virulent strains with of without heterologous genes. Before carrier vaccines are applied, these risks must be thoroughly evaluated case-by-case. Potential methods for the design of safe carrier vaccines are discussed.     

Risks connected with the use of conventional and genetically engineerd vaccines

Summary

A review is given of real and potential risks connected with the use of conventional and genetically engineered live and dead vaccines. Special attention is given to live carrier vaccines expressing one or more heterologous genes of other microorganisms. Because most carrier vaccines are still in an experimental phase, there is only limited experience with the risks of carrier vaccines. There are three potential risks of live carrier vaccines which will be discussed:

1. Changes in cell, tissue, of host tropism, and virulence of the carrier through the incorporation of foreign genes.

2. Exchange of genetic information with other vaccine or wild‐type strains of the carrier organism.

3. Spread in the environment.

Only limited experimental data are available on changes in biological behaviour of microorganisms through the incorporation of foreign genes. For example, there are indications that vaccinia virus carrying the attachment protein G of respiratory syncytial virus (RSV) replicates better in lungs of mice than vaccinia virus carrying other genes of RSV. Poxviruses carry genes that probably determine their replication in different hosts. Exchange of such host tropism genes might alter their host spectrum. Recombination between herpesvirus vaccine or wildtype strains may lead to the appearance of virulent strains with of without heterologous genes. Before carrier vaccines are applied, these risks must be thoroughly evaluated case‐by‐case. Potential methods for the design of safe carrier vaccines are discussed.

This article is based on a contribution to the course ‘Introduction of Genetically Modified Organisms into the Environment: Biosafety Aspects’, 4–14 December 1991, Wageningen, the Netherlands.     

Crystal-associated cholangiopathy associated with the ingestion of Panicum spp. and other plants

Several panicoid grasses and some other plants throughout the world have been associated with a crystal-associated hepatopathy causing photosensitisation in ruminants. We have prepared sheep with reentrant bile duct cannulae and fed them on Panicum dichotomiflorum from the Waikato region. Bile from these sheep has been collected and crystals harvested by centrifugation and Percol density gradient techniques. These sheep, when slaughtered after showing elevations of serum bilirubin and enzymes indicating liver injury, had the typical cholangiohepatopathy of Panicum spp. toxicity. The crystals have now been identified as calcium salts of epismilagenin glucuronide. Likely precursor saponins of the sapogenin have been identified in Panicum dichotomiflorum. While we regard these findings as an important step forward in the understanding of these diseases, we are now investigating the factors, including known hepatotoxins, responsible for the occurrence of these hepatopathies.     

Responses of chicks to dietary supplements of copper sulphate

Sixteen groups of 20 1‐d‐old male chicks of a hybrid laying strain were reared for 25 d and given free access to diets supplemented with o, 100, 200 or 350 p.p.m. copper (as CuSO4.5H2O), with or without antibiotic. The unsupplemented diet, based on cereals, fish and soyabean meals, contained 9.6 p.p.m. copper. Live‐weight gains, food intakes and hepatic copper concentrations were measured.

The mean hepatic copper concentration was 10.0 p.p.m. (of dry tissue) in 1‐d‐old chicks, and after 25 d rose to a mean concentration of 15.3 p.p.m. in birds fed the diets without added copper and 17.6, 32.9 and 148 p.p.m. in birds fed diets supplemented with 100, 200 and 350 p.p.m. copper respectively.

In relation to copper supplementation, two trends in live‐weight gain were noted: (1) an increase in weight gain reaching an average of +2.3 per cent at 100 p.p.m. copper, (2) a depression of weight gain at 350 p.p.m. copper averaging ‐7.5 Per cent. Only the latter trend was statistically significant. Chicks given the antibiotic supplement gained 3.6 per cent more weight than those fed the diets without antibiotic.

All these differences in weight gain were associated with differences in food consumption; food conversion efficiency was almost uniform. There were no overt signs of poisoning nor any. apparent relation between the weight gains and hepatic copper concentrations of individual chicks given the 350 p.p.m. copper supplement.     

Effects of breed and different lipid dietary supplements on beef quality

Focus of this study was to evaluate the most suitable breed/crossbred and the appropriate nutritional strategies to increase marbling in beef muscle and to improve its healthy properties, in particular the n‐3 fatty acids content. One hundred and seventy‐six heifers of three crossbreed commonly reared by Emilia‐Romagna farmers: 48 Bleu Belge × Freisian (ITA), 48 Charolais × Aubrac (FRA), and 80 Angus (ANG) were used. Animals of each breed were randomly subdivided in two experimental groups that received two diets, differing for the dietary lipid source. Control group (C) received a basal diet containing protected vegetable fats, whereas treated one (T) received the same basal diet supplemented with 0.9 kg/head/day of extruded flaxseed. After slaughtering, a sample of Longissimus thoracis was collected from each animal for meat quality analysis. Our results demonstrated that, in a shorter fattening period, ANG animals obtained the best dry matter intake, average daily gain and the best fattening scores. ITA and ANG meat presented the highest marbling scores. ANG breed had the highest amount of C18:1, the highest unsaturated/saturated fatty acids ratio and the lowest n‐6/n‐3 ratio. The T animals, independently from breed, showed the highest amount of α‐linolenic acid (ALA). In addition, ANG‐T meat presented the highest ALA content.     

Dietary and other management factors associated with colic in horses.

OBJECTIVE: To determine whether dietary and other management factors were associated with development of colic in horses. DESIGN: Prospective matched case-control study. POPULATION: 2,060 horses examined by veterinarians in private practice in Texas for colic and noncolic emergencies. PROCEDURE: Each month for 12 months, participating veterinarians were sent forms to collect information on 1 horse with colic and 1 horse that received emergency treatment for a condition other than colic, information collected included signalment, farm management and characteristics, diet, medical and preventive medical factors, transport, and activity or use. Case and control horses were compared by means of conditional logistic regression to identify factors associated with colic. RESULTS: Recent change in diet, recent change in type of hay, history of previous episode of colic, history of abdominal surgery for colic, recent change in weather conditions, recent change in housing, Arabian breed, administration of an anthelmintic during the 7-day period prior to examination, failure to receive regular deworming, age > 10 years, and regular exercise (vs pastured at all times) were associated with increased risk of colic. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that changes in diet (particularly in type of hay fed) contribute to increased risk of colic. A regular program for administration of anthelmintics may reduce the overall frequency at which colic develops, but recent administration of anthelmintics may predispose some horses to colic. Arabian horses may have an increased risk of colic, and horses at pasture may have a decreased risk of colic.     

Prevention of milk fever (hypocalcemic paresis puerperalis) by dietary salt supplements.

Twelve cows of 14 given a basic diet supplemented with Na₂GO₃ and NaHCO₃ during four weeks pre partum and one week past partum were attacked by milk fever (hypocalcemic paresis puerperalis), while 12 cows of 13 receiving the same basic diet supplemented with sulfates and chlorides remained healthy. A mixture of CaCl₂, Al₂(SO₄)₃ and MgSO₄ was found to be a convenient prophyllactic supplement.It was found possible to induce and prevent milk fever at successive parturitions in the same cow by altering the dietary conditions.The data give further support to the hypothesis that the alkali alkalinity of the diet is the major factor in induction or prevention of milk fever.     

Effect of dietary cysteine supplements on canola meal toxicity and altered hepatic glutathione metabolism in the rat.

Experiments were conducted to determine the effects of feeding canola meal (Brassica campestris and Brassica napus) on the rat hepatic glutathione detoxification system and whether dietary cysteine supplements might modify such effects. Rats were fed test diets for 14 d. Body weight change, feed consumption, hepatic glutathione concentration, and hepatic glutathione-S-transferase (GSH-S-T) activities were determined. Weight gain was decreased when canola meal was fed, whereas hepatic glutathione concentrations increased, as did hepatic GSH-S-T activity. All effects correlated with total glucosinolate concentration in the canola meal. Dietary cysteine supplements, however, did not influence the growth reduction and increased hepatic glutathione concentrations caused by feeding canola meal. Supplemental cysteine prevented the elevation in hepatic GSH-S-T activity. The elevation in hepatic glutathione concentration caused by canola meals was not an overcompensation caused by an initial depletion and therefore reflected a general hepatotoxicity. Feeding supplemental cysteine increased hepatic glutathione levels at early time intervals and delayed the induction of GSH-S-T caused by canola meal toxicity. There was no beneficial effect of supplemental dietary cysteine in overcoming the toxicity of high levels of canola meal, but supplemental cysteine did modify the canola meal-induced changes in hepatic glutathione metabolism.     

Peripheral neuropathy associated with dietary riboflavin deficiency in the chicken. I. Light microscopic study

Chickens fed a riboflavin-deficient diet from hatching had leg weakness and paralysis as early as 12 days of age. Signs worsened through day 16; after 35 days, recovery was evident. Sciatic nerves from affected chickens were enlarged. Significant microscopic lesions were confined to peripheral nerves and included tissue separation (suggesting interstitial edema), Schwann cell swelling, perivascular leukocytic infiltration, and segmental demyelination accompanied by accumulation of osmiophilic debris in Schwann cell cytoplasm. Axon degeneration was present, but was not a primary lesion. Acid phosphatase enzyme activity of Schwann cells was increased in affected nerves. These results demonstrate that dietary riboflavin deficiency causes a demyelinating peripheral neuropathy in young, rapidly growing chickens.     

Risks factors associated with subclinical mastitis in water buffaloes in Pakistan

The present study was carried to ascertain the association of various risk factors of mastitis in water buffaloes. The milk samples from buffaloes were collected and screened through California Mastitis Test for the presence of mastitis. In the present study, 15.2 % prevalence of subclinical mastitis was recorded both at the government (13.4 %) and private farms (15.5 %). The chi-square analysis showed significantly higher involvement of the right rear and front quarters. The analysis of variance technique showed significant difference in live body weight, milk yield, teat end to floor distance (P?<?0.001), udder depth, teat length, and teat diameter in mastitic and healthy buffaloes. The frequency analysis also revealed significant difference between various groups including lactation stage, teat and/or udder pathology, teat shape, and udder shape (P?<?0.001). The logistic regression analysis revealed significant positive association of mastitis with milk leakage, live body weight, milk yield, parity, calf suckling, pendulous udder, number of attendants at the farm, dirty hind legs, and udder depth.     

The effect of herbs and their associated essential oils on performance, dietary digestibility and gut microflora in chickens from 7 to 28 days of age

1. The effect of the dietary inclusion of 5 culinary herbs or their essential oils on the growth, digestibility and intestinal microflora status in female broiler chicks was assessed. From 7 to 28 d of age, either a basal control diet without supplement was given or one of 10 others, consisting of the basal diet with either 10 g/kg herb (thyme, oregano, marjoram, rosemary or yarrow) or 1 g/kg of essential oil. 2. Body mass (BM) and feed consumption (AFC) were measured on a weekly basis and used to calculate chick performance. Total viable counts of lactic acid bacteria, coliforms, anaerobes and Clostridium perfringens were determined at 25 d. Apparent nutrient digestibilities were calculated from the measured values for gross energy, nitrogen (N), dry matter (DM) and organic matter, and sialic acid concentration was also measured. 3. Generally, dietary thyme oil or yarrow herb inclusion had the most positive effects on chick performance, while oregano herb and yarrow oil were the poorest supplements. Only thyme and yarrow in these diets had a different effect when used as a herb or oil on weight gain and BM. 4. Dietary treatment had no effect on the intestinal microflora populations, apparent metabolisable energy (AME) or the calculated coefficients of digestibility. Sialic acid concentration was greatest in the birds given dietary thyme oil, compared with all other treatments except those birds receiving marjoram oil, rosemary herb and the controls. However, less sialic acid was excreted in those birds given diets with oregano or rosemary oils, or oregano herb, than in the controls. 5. Plant extracts in diets may therefore affect chick performance, gut health and endogenous secretions, although the chemical composition of the extract appears to be important in obtaining the optimal effects.     

Promoting the use of home-mixed supplements as alternatives to commercial supplements in smallholder beef production systems in the subhumid region of Zimbabwe

The economic and performance effect of supplementing smallholder cattle by substituting commercial feed with iso-nitrogenous and iso-energetic diets based on alternative protein sources was investigated in two trials. In trial 1, three diets (commercial concentrate, commercial concentrate partially substituted with mucuna, and commercial concentrate partially substituted with lablab–cowpea) compared with veld grass were allocated to 12 cattle in a complete randomised block design. In trial 2, a double complete randomised block design with 40 cattle assigned to four forage legume-based diets, a poultry-based diet and a commercial beef concentrate was carried out. Diets were offered at 1.5% of body weight daily over 56 d. Average daily weight gain (ADWG) was measured weekly in trial 1 and fortnightly in trial 2. In trial 1, ADWG was significantly (p < 0.05) higher for animals on supplements compared with non-supplemented cattle. In trial 2, ADWG was significantly highest on the groundnut stover-based diet and least on the poultry litter diet. Supplementation had a positive effect on ADWG and economic performance of smallholder beef cattle. Substitution of commercial concentrates with alternative protein sources reduced diet costs and significantly improved gross margins.     

Comparative effect of dietary supplements on the performance and severity of experimental Eimeria tenella infection in broiler chickens

Tropical Animal Health and Production - This study evaluated the productive and reproductive performance of Charolais cows with different body mass index (BMI) at calving and the development of...