Feed Additives For Growth Promotion Research Articles

Effect of yeast cultures supplementation on live weight change, rumen fermentation, ciliate protozoa population, microbial hydrolytic enzymes status and slaughtering performance of growing lamb

Yeast cultures are being exploited as a substitute of antibiotics in animal feeding to promote gut health and performance. This experiment assessed the effect of supplementation of the live yeast cultures on live weight change, rumen fermentation, ciliate protozoa population, microbial hydrolytic enzymes status and slaughtering performance of growing lamb during post weaning phase of growth. Sixty weaner lambs were fed ad libitum a composite feed mixture (CFM) for 91 days in five equal groups. The CFM had roughage to concentrate (R:C) ratio of 25:75. In addition to CFM control lambs were supplemented sterilized culture while other lamb groups received either Kluyveromyces marximanus (NRRL3234; KM), Saccharomyces cerevisiae (NCDC42; SC), Saccharomyces uvarum (ATCC9080; SU) or mixed (all tree cultures in 1:1:1 ratio) culture. The yeast cultures contained 1.5–2.0 × 10 9 cells per ml, which were fed at 1 ml per kg live weight to each lamb of treatment groups. Dry matter intake was similar among control and yeast culture supplemented lambs ranging from 68.4 to 81.2 g/kg W 0.75. However, daily gain was higher (p = 0.002) in SC and mixed yeast culture supplemented lambs. Half carcass weight ranged from 14.2 to 15.1 kg and dressing 52.2 to 53.5% were similar among five lamb groups. Similarly, other carcass traits did not change by yeast supplementation. The SU and mixed culture supplementation declined rumen fluid pH and total volatile fatty acid (TVFA) concentration. Individual yeast cultures increased but mixed yeast culture reduced total ciliates protozoa. Individual cultures increased Entodinomorphs while mixed culture reduced its number in rumen ecosystem. The SU culture increased (p = 0.023) Diplodinomorphs population. Proteases activity was 499, 407, 284 and 144 units higher respectively, in mixed, SC, SU and KM culture supplemented lambs. Cellular activity of α-amylase enzyme was lower in SC, KM and mixed yeast culture lambs. Extra cellular activity of β-glucosidase enzyme was similar (p = 0.581), whereas cellular (p = 0.007) and total activity was higher (p = 0.029) in SU culture lambs. The extra cellular and total activity of xylanase was not different but cellular activity was higher (p = 0.042) in KM lambs. The carboxymethyle cellulase activity was similar among the five animal groups. The SC, SU and mixed culture supplementation improved feed intake (p = 0.722) by 8.0, 13.3 and 18.8% and daily gain (p = 0.002) by 26.6, 11.7 and 18.8% respectively in lambs. The SC culture feeding promoted feed intake and growth by 8 and 26.6% respectively showing the suitability of growth promoting microbial feed additive. The SC culture supplementation in rumen ecosystem also facilitated microbial growth and improved activity of short chain polysaccharides degrading micro-organism. Therefore, SC culture can be used as a growth promoting feed additives in meat animal production.

Antibiotics Susceptibility Pattern of Escherichia coli Strains Isolated from Chickens with Colisepticemia in Tabriz Province, Iran

Antimicrobial agents are used extremely in order to reducing the enormous losses caused by Escherichia coli infections (colibacillosis) in Iran poultry industry. In this investigation fifty avian pathogenic Escherichia coli (APEC) strains isolated from broiler chickens with colisepticemia and examined for susceptibility to antimicrobials of veterinary and human significance. In vitro antibiotic activities of 32 antibiotic substances against the isolates were determined by disc diffusion test (Kirby Bauer method). Multiple resistances to antibiotics were observed in all the isolates. The highest rate of resistance was against Nalidixic acid (100%), Lincomycin (100%), Erythromycin (97%), Oxytetracycline (95%), Chlortetracycline (95%), Tetracycline (94%), Flumequine (94%), Tiamulin (91%), Doxycycline (88%), Difloxacin (83%), Neomycin (81%), Streptomycin (81%), Trimethoprim-Sulphamethoxazole (80%), Kanamycin (77%), Enrofloxacin (76%), Norfloxacin (68%), Ciprofloxacin (67%), Chloramphenicol (67%), Furazolidone (66%), Nitrofurantoin (56%), Amoxicillin (53%) and Ampicillin (47%). Resistance to Gentamicin wasn’t observed and to Amikacin, Cefazolin, Colistin, Tobramycin, Ceftizoxime, Cefixime, Lincospectin, Ceftazidime and also Florfenicol were low. This study showed resistance rate against the antibiotics that are commonly used in poultry is very high but against them that are only used in human or less frequently used in poultry is significantly low. These findings confirm significant increase in the incidence of antimicrobial resistance in the E. coli strains is most probably due to increased use of antibiotics as feed additives for growth promotion and prevention of diseases, use of inappropriate antibiotics for treatment of diseases, resistance transfer among different bacteria and possible cross resistance between antibiotics used in poultry. This study also showed that the prevalence of Quinolone-Resistant Escherichia coli (QREC) is very high in broiler farms in Tabriz province. The high presence of QREC from broiler chickens probably is due to overuse of enrofloxacin in these farms for therapeutic purposes. The present study suggests introduction of surveillance programs to monitor antimicrobial resistance in pathogenic bacteria is strongly needed because other than animal health problems, transmission of resistant clones and resistance plasmids of E. coli from food animals (especially poultry) to humans can occur.

Performance of growing–finishing pigs fed medium- or high-fibre diets supplemented with avilamycin, formic acid or formic acid–sorbate blend

A total of 160 growing–finishing pigs with initial body weights of 27 kg and originating from eight farms were used in a performance trial to investigate the effects of dietary fibre content (medium or high) and growth-promoting feed additives (none, avilamycin, formic acid or formic acid–sorbate blend) on pig growth, the feed to gain ratio and the incidence of diarrhoea. Medium-fibre grower and finisher diets [188 and 196 g neutral detergent fibre (NDF)/kg dry matter (DM)] were composed of barley and soybean meal and the respective high-fibre diets (239 and 284 g NDF/kg DM) of barley, oats, barley fibre, peas, soybean meal and vegetable oil. Both medium- and high-fibre diets were similar in net energy (8.7 MJ/kg) and ileal digestible lysine content (8.0 and 6.6 g/kg for grower and finisher diets, respectively). Avilamycin (40 mg/kg) was added to grower diets only whereas formic acid (8 g/kg) and formic acid–sorbate blend (8 g/kg formic acid and 0.4 g/kg potassium sorbate) were added to both grower and finisher diets. No diet×additive interactions were observed in the performance or carcass characteristics of pigs. Dietary fibre content did not affect the growth or feed to gain ratio of pigs. In the growing period, pigs fed diets with avilamycin, formic acid or formic acid–sorbate blend grew faster and had a lower feed to gain ratio than did those fed diets without additives. The differences between the additives were not significant. In the finishing period, pigs fed acidified diets grew faster and utilised feed more efficiently than did those in the avilamycin group. Furthermore, formic acid–sorbate blend enhanced pig performance more than did plain formic acid. For the total fattening period, the average growth rates were 856, 878, 896 and 930 g/day and the feed to gain ratios 2.55, 2.51, 2.43 and 2.32 kg DM/kg gain for diets without additives and with avilamycin, formic acid and formic acid–sorbate blend, respectively. Additives improved the growth and feed to gain ratio compared to diets without additives. Performance was better with organic acid supplementation of grower and finisher diets than with avilamycin supplementation of grower diet only. In addition, formic acid–sorbate blend improved the feed to gain ratio more than did plain formic acid. In the growing period, additives decreased the incidence of diarrhoea in the medium-fibre diet. In the high-fibre diet, the incidence of diarrhoea was generally low, except in the avilamycin treatment. We concluded that formic acid and formic acid–sorbate blend were equally effective alternatives to the antibiotic avilamycin in grower diets. Since organic acids can be added to finisher diets as well, their use resulted in further improvements in pig performance compared to avilamycin which can be used in grower diets only. The efficacy of formic acid as a growth promoter was intensified with sorbate addition.

Antibiotic usage in animals: impact on bacterial resistance and public health.

Antibiotic use whether for therapy or prevention of bacterial diseases, or as performance enhancers will result in antibiotic resistant micro-organisms, not only among pathogens but also among bacteria of the endogenous microflora of animals. The extent to which antibiotic use in animals will contribute to the antibiotic resistance in humans is still under much debate. In addition to the veterinary use of antibiotics, the use of these agents as antimicrobial growth promoters (AGP) greatly influences the prevalence of resistance in animal bacteria and a poses risk factor for the emergence of antibiotic resistance in human pathogens. Antibiotic resistant bacteria such as Escherichia coli, Salmonella spp., Campylobacter spp. and enterococci from animals can colonise or infect the human population via contact (occupational exposure) or via the food chain. Moreover, resistance genes can be transferred from bacteria of animals to human pathogens in the intestinal flora of humans. In humans, the control of resistance is based on hygienic measures: prevention of cross contamination and a decrease in the usage of antibiotics. In food animals housed closely together, hygienic measures, such as prevention of oral-faecal contact, are not feasible. Therefore, diminishing the need for antibiotics is the only possible way of controlling resistance in large groups of animals. This can be achieved by improvement of animal husbandry systems, feed composition and eradication of or vaccination against infectious diseases. Moreover, abolishing the use of antibiotics as feed additives for growth promotion in animals bred as a food source for humans would decrease the use of antibiotics in animals on a worldwide scale by nearly 50%. This would not only diminish the public health risk of dissemination of resistant bacteria or resistant genes from animals to humans, but would also be of major importance in maintaining the efficacy of antibiotics in veterinary medicine.

Antibiotic resistance of bacterial litter isolates

Use of antibiotics in subtherapeutic doses as growth-promoting feed additives for animal production is widespread in the U.S. and throughout the world. Previous studies by our research group concluded that size fractionation of poultry (broiler) litter followed by storage facilitated reutilization of litter as a soil amendment or bedding supplement. However, litter microbial contamination, including antibiotic-resistant populations, and accumulation of metals and other elements may limit litter reutilization. Litter from four broiler houses was separated into a fine fraction for use as a soil amendment, and a coarse fraction for reutilization as a bedding supplement in growing subsequent flocks of broilers. Fractions and whole litter were stored in indoor piles simulating farm storage conditions for 4 mo with periodic analysis for metals, other elements, and culturable bacteria (including total and fecal coliform, Aeromonas hydrophila, Pseudomonas aeruginosa, Yersinia enterocolitica, and Campylobacter jejuni). Representative bacterial isolates were tested for their sensitivity to 12 common antibiotics (ampicillin, bacitracin, cephalothin, erythromycin, gentamicin, kanamycin, nalidixic acid, neomycin, penicillin, streptomycin, sulfisoxazole, and tetracycline) using the Kirby-Bauer technique. Pathogens and indicator bacteria tested were found to be resistant to multiple antibiotics. Data suggest that microbial contamination of litter should be reduced or eliminated prior to reutilization to minimize environmental health risks related to transfer of antibiotic-resistant bacteria to humans or other animals.

Influence of the gut flora and of some growth-promoting feed additives on nitrogen metabolism in pigs. II. Studies in vivo

Analysing the gastrointestinal contents of 22 slaughtered pigs, it was found that about 10% and 25% of the non-protein nitrogen (NPN) in the small and large intestine respectively, consisted of ammonia derived from deamination of amino acids and from urea degradation. Also the decarboxylation of amino acids was important. Both deamination and decarboxylation processes were greatly reduced by nutritional levels (20 p.p.m.) of Virginiamycin and Spiramycin. From the analysis of the N and urea content of the urine it could be deduced that Virginiamycin and Spiramycin can enhance N retention in pigs. Digestibility experiments with re-entrant cannulated pigs on a semi-purified diet revealed that Virginiamycin (50 p.p.m.) increases ( P < 0.15–0.30) the apparent ileal digestibility of nitrogen (+2.1%), lysine (+1.4%), glycine (+4.8%), valine (+2.2%) and methionine (+3.3%). Absorption experiments based on perfusion of a temporarily isolated loop (2 m) of the terminal small intestine of the pig, demonstrated that Virginiamycin enhances the net absorption of free amino acids by about 9% ( P < 0.05–0.001). Growth promotion by nutritional antibacterials can therefore partly be explained by an altered digestion, absorption and retention of N in the pig.

Influence of the gut flora and of some growth-promoting feed additives on nitrogen metabolism in pigs. I. Studies in vitro

Nine growing pigs (10–40 kg) were cannulated either in the duodenum or ileum or caecum and fed a dry-milk powder diet. These pigs were used as donors of fresh intestinal contents for short (4 h) incubation experiments. From the incubations of duodenal contents, it appeared that the bacterial activity was not important. In consequence, the antibiotic effects of Virginiamycin and Spiramycin were also negligible. During incubations of ileal contents, eventually supplemented with free amino acids, on the other hand, 20–30% of the amino acids were degraded by the flora either by deamination, with formation of ammonia, or by decarboxylation with formation of amines: histamine, putrescine, cadaverine, tyramine, phenylethylamine. Cadaverine, the decarboxylation product of lysine, was the most important amine detected. Both processes were severely decreased when the antibacterials Virginiamycin (50 p.p.m.), Spiramycin (50 p.p.m.), Carbadox (50 p.p.m.) and copper sulphate (200 p.p.m.) were present during the incubation of the ileal contents. The fermentation of caecal contents was characterized by a pronounced production of ammonia, slightly inhibited by Virginiamycin and Spiramycin. Testing the amino acid decarboxylation activity of the dominant flora ( E. coli, S. faecalis, L. acidophilus and L. fermenti) in the small intestine of the pig, it was found that E. coli is the main producer of amines in the small intestine of pigs. We conclude that the gut flora of pigs has a measurable negative influence on protein digestion in the small intestine and that this effect can be overcome by feeding nutritional antibacterials.

FEED ADDITIVES AS GROWTH PROMOTERS FOR LIVESTOCK IN THE UNITED KINGDOM AND IN THE EUROPEAN ECONOMIC COMMUNITY

The recommendations of the Swann Committee and their enactment are reviewed in relation to feed additive practice in the United Kingdom. Results from surveys of enterobacteria in farm animals, animal products and man in the UK are given and their indications considered. Procedures for regulating the use of feed additives for growth promotion in the European Economic Community are outlined and some current preoccupations are considered. Criteria for feed additives used in growth promotion are discussed in relation to the evidence of the outcome of prohibiting therapeutic antibiotics for growth promotion in the U.K.