Responses of broiler chickens to high-frequency and low-frequency fluorescent light.

1. The influence of the flicker frequency on physical activity and energy expenditure of broilers was studied using commercially available high-frequency (HF) and low-frequency (LF) fluorescent lamps in a 23L:1D lighting schedule. 2. Broilers were reared under and adapted to HF. They were alternately subjected to HF and LF during measurement of activity and energy expenditure. 3. In comparison with HF, LF inhibited activity (number and intensity of movements), but did not influence energy expenditure. 4. It was concluded that the 100 Hz flickering of low-frequency light is detected by broilers and has measurable behavioural effects upon them. 5. The results were discussed in relation to current knowledge of human and birds' critical flicker frequency and perception.     

Feeding dihydroquercetin to broiler chickens

1. A total of 80 male Ross 308 broilers were used in a study to investigate the effect of dietary dihydroquercetin (DHQ) on growth performance variables, gastrointestinal tract (GIT) and immune organ development, glutathione peroxidase (GPx) and haemoglobin in blood, hepatic vitamin E content, dietary N-corrected metabolisable energy (AMEn) and nutrient retention coefficients when fed to broiler chickens from 7 to 35 d of age.

2. Two treatments were used in this study: control (C) and C + 0.5 g/kg extract of Siberian Larch (Larix sibirica) per kg feed, containing 85% DHQ. The diets were fed over 2 feeding phases, a grower phase from 7 to 28 d of age and a finisher phase from 28 to 35 d of age. The birds were reared under the breeder’s recommended conditions.

3. In general, there were no effects of DHQ on growth performance of broiler chickens. However, the results of this experiment showed that there can be changes in the redness colour of the breast meat when DQH is fed. No negative effects of feeding DHQ at 0.5 g/kg diet were observed in this study.

4. Supplementation of poultry diets with DHQ under standard industry-rearing conditions did not improve the performance or any of the studied variables, except an increase of redness index of the breast fillets. Feeding DHQ at different doses and/or under more challenging conditions, e.g. heat stress, may, however, bring positive responses.     

Ocular responses to ammonia in broiler chickens

In two trials, 60 male commercial broilers were placed in each of eight environmentally controlled chambers receiving 0, 25, 50, or 75 ppm aerial ammonia from 1 to 28 days. Birds exposed to 25 ppm (lower concentration) ammonia gas developed ocular abnormalities but at a slower rate when compared with birds exposed to 50 and 75 ppm (higher concentrations). Birds exposed to higher concentrations also developed more severe lesions. With little atmospheric ammonia present after 28 days of the grow-out stage, the corneas indicated signs of healing. Lymphocytes and heterophils were seen in the iris at 49 days in ammonia-exposed birds even when ammonia exposure was terminated at 28 days. The lower ammonia concentrations resulted in abnormalities that were slight when compared with those seen at the higher ammonia concentrations. As measured by the incidence of inflammatory infiltrates in the trachea, lung, and air sacs, respiratory tract tissues did not appear to be affected by any tested level of aerial ammonia. The findings in this investigation represent the first report indicating that ammonia-induced uveitis in chickens clears rapidly after exposure to ammonia ceases.     

Leg health and performance of broiler chickens reared in different light environments

1. The effects of light source and intensity on leg health and performance of female ROSS 308 broiler chickens were investigated in a 2 x 2 experimental design (8 groups of 275 chicks) of two light sources (Osram biolux and Osram warm-white) and two light intensities (5 and 100 clux, adjusted to fowl-perceived illuminance). 2. At 41 d of age, body weight, gait-score, footpad dermatitis and hock-burn were measured on 50 birds from each light environment. In addition, weekly feed intake and body weight were determined on a group basis and mortality was recorded continuously. 3. The light environment did not affect the severity of the gait-score or hock-burns. The risk of moderate to severe lameness and hock-burns increased with body weight. Birds weighing more than 2400 g had an increased probability of moderate footpad lesions in biolux light. 4. Weight and gait-score, as well as gait-score and hock-burn were positively correlated. Podo-dermatitis was weakly correlated with hock-burn, which contradicts earlier findings. The light environment did not affect feed intake, body weight or mortality. 5. The light sources and intensities employed in this study did not adversely affect production or leg health of broiler chickens reared semi-commercially.     

Development of disaccharidase activity in the small intestine of broiler chickens

1. The changes in disaccharidase activity in the small intestine of broiler chickens were investigated in isolated enterocytes on d 18 of embryonic development and d 1, 7, 21, 35 and 56 after hatching. 2. The specific activities of maltase, lactase and trehalase were greatest on d 18 of embryonic development. After hatching, maltase specific activity gradually decreased until d 18. 3. After d 7 postnatally only traces of lactase and trehalase activity were found in the enterocytes. 4. Significant sucrase activity was found on d 18 of embryonic development and the activity of this enzyme increased 2-fold after hatch and remained generally constant up to d 35, after which the enzyme specific activity declined.     

Pathogenicity and control of Eimeria mitis infections in broiler chickens.

The pathogenicity of two strains (B4 and C2) of Eimeria mitis was studied using young broiler chickens. Both strains of coccidia were pathogenic, and C2 strain was more virulent than B4. Growth of the broilers was depressed as early as day 3 postinoculation (PI), but the depression was greatest during days 5 and 6 PI. Feed conversion and shank skin pigment of the young broiler chickens were concomitantly affected by infections of E. mitis. Infection subsided by day 7 or 8 PI and was accompanied by a compensatory growth. The drugs effective against the infections were halofuginone, lasalocid, monensin, and nicarbazin. The least efficacious were zoalene and amprolium plus ethopabate.     

Swollen-head syndrome in broiler chickens

Swollen-head syndrome is a disease seen in broiler chickens between 4 and 6 weeks of age in Southern Africa. It appears to be caused by a mixed coronavirus and Escherichia coli infection. The coronavirus appears to be of a hitherto unrecorded serotype. The disease is controlled by an attenuated live-virus vaccine and antibacterial medication.     

Salt poisoning in broiler chickens

The clinical signs of salt poisoning in young chickens are thirst, diarrhoea and weakness. When 13 500 broilers are simultaneously affected, the deterioration that occurs in their physical condition and in the litter beneath their feet is dramatic. Two flocks of meat chickens on a small unit in North Otago were affected in this way.     

Campylobacter succession in broiler chickens

The competitive ability of Campylobacter coli OR12 over C. jejuni OR1 has been examined in experimental broiler chickens following the observation that C. coli replaced an established C. jejuni intestinal colonisation within commercial chicken flocks reared outdoors [El-Shibiny, A., Connerton, P.L., Connerton, I.F., 2005. Enumeration and diversity of campylobacters and bacteriophages isolated during the rearing cycles of free-range and organic chickens. Appl. Environ. Microbiol. 71, 1259-1266]. Co-cultures of C. coli OR12 with C. jejuni OR1, revealed that the two species were able to grow together at similar growth rates in exponential growth phase but if the disparity of the inoculum ratios were >log(10)4 in favour of C. coli OR12, C. jejuni OR1 was observed to prematurely enter decline phase. Chickens were pre-colonised with C. jejuni OR1 at 21-days-old to examine succession in vivo. The birds were inoculated between 2 and 12 days later with C. coli OR12, to determine if the second isolate could efficiently colonise and compete with an established C. jejuni strain. C. coli OR12 were able to co-colonise before replacing C. jejuni OR1 as the dominant species when the birds were more than 27 days of age at the time of administration over a 4-day period. If these criteria were met C. coli OR12 became the dominant isolate otherwise co-colonisation occurred until they were met. C. coli OR12 was also found to displace three alternative C. jejuni strains from pre-colonised chickens challenged with C. coli OR12 at 30 days of age and tested at 40 days. These data raise the possibility of manipulating populations of Campylobacter colonising chickens through competition.     

Live attenuated vaccine-based control of necrotic enteritis of broiler chickens

A vaccine for necrotic enteritis (NE) of chickens would reduce the current need to prevent or treat the disease in broiler chickens with antimicrobial drugs. The objective of this study was to understand aspects of immunity to the disease. The first experiment examined the virulence of six strains of Clostridium perfringens isolated from cases of NE in broiler chickens. Using a 5-day experimental oral infection of 2-week-old broiler chickens, four of the six strains were found to be virulent. Pulsed-field gel electrophoresis and PCR showed that virulence was not associated with a plasmid encoding the beta2 toxin gene, cpb2, since this was present in virulent and one of the two avirulent strains. In the second experiment, two virulent and one avirulent strains were tested for their ability to immunize ("infection-immunization") chickens through the oral route. The procedure used experimental infection for 5 days followed by bacitracin treatment for 9 days, and then re-challenge 2 days later with a virulent strain, CP4. Infection-immunization with the virulent isolates protected chickens from subsequent virulent challenge, whereas the infection-immunization with the avirulent isolate did not. In a third experiment, two of four alpha-toxin-negative mutants of CP4 protected birds from experimental NE after oral immunization. These two mutants were also attenuated for virulence. We conclude that it is possible to immunize chickens successfully against NE and that immunogen(s) other than alpha-toxin are important in protective immunity against oral infection.     

Salt poisoning in broiler chickens

The incident occurred on a small, owner-operated broiler unit that used home-mixed feed. Two flocks of broilers, one aged 6 weeks and one aged 6 days, developed signs of watery diarrhoea, thirst and weakness. Over 3 days the mortality increased considerably and many birds were noticed to show laboured breathing. The majority of dead birds had an excess of clear fluid in the pericardial sac, oedematous lungs and pale swollen kidneys. Cystic dilation of the testes was conspicuous in several birds from the younger flock killed at 12 days of age. This lesion is a specific indication of sodium toxicity in young broilers. Histological lesions were those associated with cardiovascular collapse and hypoxia. Liver levels of sodium chloride were 4 g/kg of wet weight. Broiler feed samples contained more than 7% sodium chloride whereas the nutritional specifications were for 0.4%. The rations had been correctly mixed and the problem was traced to a faulty batch of meatmeal that had been contaminated by salt used for curing hides.     

A trial of biosecurity as a means to control Campylobacter infection of broiler chickens

We ran a controlled intervention trial to assess whether the risk of a broiler flock becoming infected with Campylobacter could be reduced by biosecurity measures. These were a standard method of cleansing and disinfecting the poultry house prior to stocking, and a standard hygiene protocol followed by all personnel who entered the study house during the flock's life. Thirty-nine flocks were allocated to intervention or control groups in a ratio of 1:2. Intervention flocks were asked to follow the specified biosecurity measures; all flocks were monitored weekly for Campylobacter infection. Analysis of infection at 42 days of age and over the life of the flock showed that the risk of thermophilic Campylobacter infection of broilers was reduced by over 50% in intervention flocks. Parts of the intervention identified as significant in the univariable analysis included twice weekly replenishment of boot dip disinfectant; potential independent risk factors identified included the location of ventilation fans and daily sanitisation of the water supply. The non-random allocation of 10 flocks to the control group may have introduced some study bias (the effect of which is discussed in the paper).     

Nutritional approaches to ameliorate pulmonary hypertension in broiler chickens

This article reviews recent nutritional approaches for counteracting the development of pulmonary hypertension syndrome (PHS; ascites) in broiler chickens especially when they are reared at high altitudes. High altitudes impose the sustained stress of hypobaric hypoxia, which reduces the availability of atmospheric oxygen to red blood cells passing through the lungs, thereby causing systemic arterial hypoxaemia (undersaturation of haemoglobin with oxygen), pulmonary arterial hypertension and PHS/ascites in susceptible broilers. Proper nutritional strategies are needed to reduce metabolic activity and prevent the development of ascites especially when modern broilers are reared in regions where the existing altitudes limit the availability of atmospheric oxygen. This article also addresses controversies with regard to broiler nutrition in relation to PHS. For example, the catabolism of protein from feed ingredients incurs increased oxygen consumption, suggesting that feeding reduced‐protein diets to broiler chickens may result in reduced PHS incidences. However, experimental and field data indicate that feeding reduced‐protein diets to broilers subjected to hypobaric hypoxia increases the development of PHS. Controversies on the nutrition of unsaturated fat in relation to PHS are also discussed. In conclusion, hypoxia, acidosis, vasoconstriction and enhanced metabolic rate are triggers of PHS. Feeding reduced‐protein diets might promote the susceptibility of broilers to PHS by decreased dietary intake of arginine, decreased uric acid production and increased lipogenesis. Feeding high‐protein diets, dietary arginine supplementation, partial substitution of sodium bicarbonate for sodium chloride, feeding low‐fat diets and effective feed restriction programmes can be considered as nutritional approaches to prevent PHS.