Eva Skřivanová

Influence of dietary selenium and vitamin E on quality of veal

Three groups of six calves each were fed a milk replacer and a starter concentrate for 15weeks. Calves of the first group received the basal diet containing selenium (Se) and vitamin E at 0.095-0.128mg and 30-33mg per kg of total solids, respectively. Calves of the second group received the basal diet supplemented with Se-enriched yeast to increase dietary Se concentration to 0.50mg/kg. The third group of calves received the latter diet supplemented with vitamin E to increase its concentration to 100mg/kg. There was no effect of diet on growth rate, digestibility of dry matter and Se, chemical composition of meat (M. Longissimus thoracis et lumborum), meat colour and fatty acid profile of meat lipids. The Se supplementation significantly increased Se concentration in muscle from 0.21 to 0.43mg/kg. The activity of glutathione peroxidase (GSH-Px) in muscle and liver tissue of Se-supplemented animals was increased by 56% and 67%, respectively, compared to the control. The combined supplementation of vitamin E and Se significantly improved the lipid stability of meat compared to the control diet, but not compared to the Se-supplemented diet. It can be concluded that dietary Se supplementation increases the concentration of Se and the GSH-Px activity in meat, but has limited potential for improving meat oxidative stability.

Susceptibility of Campylobacter jejuni to organic acids and monoacylglycerols

Organic acids can be used as feed supplements or for treatment of poultry carcasses in processing plants. The antimicrobial activity of nineteen organic acids and two monoacylglycerols in cultures of Campylobacter jejuni CCM 6214T (ATCC 33560) was determined using a SYBR Green-based real-time PCR assay. The IC50 was a concentration at which only 50 % of a bacteria specific DNA sequence was amplified. Caprylic, capric and lauric acids were the most efficient antimicrobials among the compounds tested (IC50 ≤ 0.1 mg/mL). In a weakly acidic environment (pH 5.5), the antimicrobial activity was more pronounced than at pH 6.5. At pH 5.5, oleic and fumaric acid also had clear antimicrobial activity, as did monocaprylin. The antimicrobial activity of acetic, butyric, stearic and succinic acid was low. In cells treated with fumaric acid, the potential of potassium and tetraphenylphosphonium ion-selective electrodes changed, indicating an increase in cytoplasmic and outer membrane permeability, respectively. No changes in membrane permeability were observed in cells treated with capric acid or monocaprin. Transmission electron microscopy revealed separation of the inner and outer membrane in cells treated with capric and fumaric acid, as well as cytoplasmic disorganization in cells exposed to capric acid.

Inhibitory activity of rabbit milk and medium-chain fatty acids against enteropathogenic Escherichia coli O128

Colibacillosis represents a major cause of diarrhea in young rabbits. In order to elucidate protective effect of milk, in vitro and in vivo experiments were carried out. In the in vitro experiment, rabbit milk treated with lipase significantly decreased the number of viable cells in cultures of Escherichia coli, O128 serotype, from 10.3 to 6.2-7.3log(10)/(cfuml). The lipase effect was the same with heat-treated (100 degrees C/10min) and raw milk. Raw milk without lipase decreased the number of E. coli only marginally. In the in vivo experiment, weaned rabbits received feed contaminated with the same bacterium. The course of the infection was moderate, only 2 out of 36 infected rabbits died. Seven days after inoculation, caprylic acid at 5g/kg feed and triacylglycerols of caprylic and capric acid at 10g/kg feed decreased faecal output of E. coli from 10.2log(10)/(cfug) to 5.8 and 6.1log(10)/(cfug), respectively. The number of E. coli in faeces of non-infected rabbits averaged 4.0log(10)/(cfug). The growth of infected rabbits was slow for 2 weeks after infection. In the third week a compensatory growth was apparent. At the end of the experiment, average body weights of rabbits receiving caprylic acid and those of non-infected rabbits were not significantly different. It can be concluded that (i) lipids rather than proteins seem to be responsible for the antimicrobial activity of rabbit milk; and (ii) this activity was lipase-dependent. Caprylic acid or oils with high a concentration of it may be used as feed supplements for weanlings.

In Vitro effect of C2–C18 fatty acids on salmonellas

The susceptibility ofSalmonella spp. to 15 fatty acids was determinedin vitro in cultures grown on glucose. Antimicrobial activity was expressed as IC50 (a concentration at which only 50 % of the initial glucose in cultures was utilized). Caprylic acid was the only acid inhibiting glucose utilization. In cultures ofS. enteritidis, S. infantis andS. typhimurium, IC50 of caprylic acid ranged from 0.75 to 1.17 mg/mL. A moderate adaptation effect was observed as these values increased 1.5–1.8 times when bacteria were subcultured 10 times in media containing a low concentration of capyrlic acid (1/3 IC50). No effect of calcium ions added in excess on antimicrobial activity of caprylic acid was observed. Incubation of salmonellas with caprylic acid (1 mg/mL; 30 min) at pH 5.2–5.3 led to a reduction in the concentration of viable cells below the detection limit; 2–6 % ofSalmonella cells survived at pH 6.3–6.6.

Inhibitory effect of organic acids on arcobacters in culture and their use for control of Arcobacter butzleri on chicken skin.

The inhibitory effects of 17 organic acids (C₂-C₁₆ fatty acids, sorbic, benzoic, phenylacetic, fumaric, succinic, lactic, malic and citric) on Arcobacter butzleri, Arcobacter cryaerophilus and Arcobacter skirrowii were investigated by determining their IC₅₀ values, defined as the concentration of acid at which the target DNA sequence was expressed at 50% of the positive control level in cultures incubated at 30°C for 24 h. DNA was analysed by real-time PCR. The Arcobacter strains tested were inhibited by all the organic acids, with the sensitivities in the order A. skirrowii > A. cryaerophilus > A. butzleri. Eight acids with IC₅₀ values of <1 mg/mL against A. butzleri were tested for their effects on A. butzleri inoculated on chicken carcasses at a concentration of 5 log CFU/g of skin. Inoculated halved carcasses were immersed in solutions of the acids at 5 mg/mL for 1 min. Samples of skin were collected from carcass halves after storage at 4°C for 0, 1, 2 or 3 days for enumeration of arcobacters on Muller-Hinton agar. All eight tested acids suppressed bacterial proliferation. The highest inhibitory activities were observed for benzoic, citric, malic and sorbic acids. Subsequent sensory analysis revealed benzoic acid to be the most suitable organic acid for chicken skin treatment.

Effect of coated and non-coated fatty acid supplementation on broiler chickens experimentally infected with Campylobacter jejuni

The aim of this study was to examine whether and to what extent the supplementation of feed with a coated or non-coated mixture of fatty acids (caprylic and capric acid) affects broiler chickens experimentally infected with Campylobacter jejuni. The study was carried out using 48 chickens divided into four experimental groups. Throughout the whole rearing period (1-42 days), the chickens were fed a diet supplemented with 0.25% caprylic and capric acid (1:1), coated or non-coated. At the age of 14 and 28 days, chickens were orally challenged with C. jejuni. At regular time intervals post-inoculation, the shedding of C. jejuni was assayed using quantitative real-time PCR. Both supplements significantly decreased faecal C. jejuni counts by 1.2-4.1 log(10) CFU/g 4 days post-inoculation; after this time period, the effect of medium-chain fatty acids (MCFA) was less pronounced or absent. Campylobacter jejuni counts in excreta samples were significantly lower in chickens fed coated MCFA than in those fed non-coated MCFA. No effect of MCFA on feed intake or growth of chickens was observed. In conclusion, (i) MCFA are active against C. jejuni and (ii) the encapsulation enhanced the efficacy of the acids. These results allow the recommendation of using MCFA as feed additives in chickens, preferably 2-3 days before slaughter.

Changes in the bacterial population of the caecum and stomach of the rabbit in response to addition of dietary caprylic acid.

The effect of caprylic acid, either in its pure form, or as Akomed R, on the microbial community of the stomach and caecum of farmed rabbits was investigated. This fatty acid, which is often added to the diet of farmed rabbits to reduce mortality rates was shown to reduce the number of coliforms isolated from both the stomach and the caecum. Moreover, it led to a reduction in the total number of anaerobic bacteria isolated from the caecum, but not for those isolated from the stomach. Its mode of action remains unclear, but here it is shown by use of both DGGE and TRFLP analysis that these changes are not confined to one specific group of bacteria, but rather affects a number of species.

Comparative effect of amidated pectin and psyllium on cholesterol homeostasis in rats.

The effects of amidated pectin and psyllium on serum, hepatic and faecal cholesterol concentration were compared in female rats fed diets supplemented with palm fat and cholesterol at 50 and 10 g/kg, respectively. Control rats were fed a diet supplemented with cellulose at 60 g/kg. In treated rats, cellulose was replaced with either amidated pectin or psyllium. Amidated pectin and psyllium intake significantly decreased serum cholesterol from 3.41 μmol/ml (control) to 1.68 and 2.04 μmol/ml, respectively, and hepatic cholesterol from 31.9 μmol/g (control) to 7.2 and 9.0 μmol/g, respectively. Histology with lipid-staining Sudan Black B revealed that liver tissue from control rats was infiltrated with lipids, but staining was absent in livers of treated rats. No hepatic pathophysiology was apparent in treated rats. Amidated pectin and psyllium intake significantly increased faecal fat content. Faecal cholesterol content was significantly increased in rats that were fed amidated pectin, and non-significantly increased in rats that were fed psyllium. Body weight and food intake did not differ among treatment groups. In conclusion, amidated pectin, a novel sequestrant of sterols, demonstrated a similar effect on rat serum and hepatic cholesterol concentration to psyllium, which is a well-established hypocholesterolaemic agent.

A mobile system for rearing meat chickens on pasture

The effect of grazing on the productive performance and meat quality was evaluated for chickens (Ross 308, n = 192). Chickens were kept in two pens on wooden shavings (2 × 96) from one day of age. On day 23 in the original pen until the end of the experiment at 6 weeks of age. Both groups were fed the same pelleted feed ad libitum. For the pasture-reared group, the moveable shelter was moved twice daily around the pasture with a predominance of grass species. The herbage intake of chickens was indirectly assessed by compressed sward height measurement after each cage movement, which employed a rising plate-meter. In the pasture, chickens preferred grass over clover. There was no significant effect of grazing observed on chicken body weight. The mortality of chick - ens in the grazing group was lower than that in the control group. Pasture treatment improved meat flavour by 9% (P = 0.014), produced breast meat with significantly higher ( P = 0.009) redness, and almost doubled the concentra - tion of α-tocopherol ( P < 0.001). There were no significant effects of grazing on the dry matter, fat, cholesterol or pH of the meat. The production of TBARS in the breast meat of the pasture group after storage at 4°C for 5 days was lower ( P = 0.013) than that in the breast meat of the control chickens. Although the differences between K, Ca, P, Mg, and N concentrations in pasture and soil before and after grazing reached 20%, these differences were not significant.

Effect of green alga Planktochlorella nurekis on selected bacteria revealed antibacterial activity in vitro.

The green alga Planktochlorella nurekis (Chlorellaceae, Chlorophyta) is considered a producer of antibacterial mixture of long-chain fatty acids, which has possibly similar composition and mode of action as chlorellin produced by another green alga, Chlorella vulgaris. Although the antibacterial properties of C. vulgaris have been reported, the interactions of P. nurekis with bacteria have not been determined yet. The aim of this study was to elucidate the effect of P. nurekis water suspension on growth of selected gastrointestinal bacteria in vitro so that it could be used as a suitable feed supplement in animal farming. Unknown bacterial populations occurring in the algal suspension were identified using 16S rRNA sequencing assay. Selected strains were cultivated with lyophilized P. nurekis and the antibacterial effect was monitored. The composition of fatty acids and heat sensitivity of antibacterial substances were also examined. Sequencing analysis of 71 bacterial 16S rRNA genes in xenic algal suspension identified common environmental microbiota, one strain belonging to the class Alphaproteobacteria, 17 to Betaproteobacteria, 44 to Gammaproteobacteria (dominated by Pseudomonas putida strains), and nine to Sphingobacteria. The antimicrobial activity of P. nurekis suspension was tested at a concentration range of 0.75–6 mg/ml. The highest inhibitory effect was observed on bifidobacteria. Statistically significant reductions in bacterial counts were also observed for Escherichia coli, Salmonella enterica var. Enteritidis, S. enterica var. Infantis, Campylobacter jejuni, and Arcobacter butzleri. The growth of Lactobacillus johnsonii was significantly stimulated. The relative proportions of C14–C22 fatty acids in P. nurekis were found as follows: saturated 54.28%, monounsaturated 30.40%, and polyunsaturated 7.16%. The antibacterial compounds present in P. nurekis suspension exhibited thermostability. The results indicate that P. nurekis can inhibit some pathogenic gastrointestinal bacteria and seems to be a promising essential nutrients source in animal nutrition.