December 2006 science into practice
Scientists say moulting may affect the invasion of tissues by Salmonella enteritis (SE) in laying hens.
Salmonella infection affected by moulting
Using a tissue culture procedure, scientists at the USDA in Athens, Georgia, USA, have concluded that moulting may affect the invasion of tissues by Salmonella enteritis (SE) in laying hens.
They conducted three identical trials in which 80-week-old, active laying hens were divided into two groups of 6 birds each. The moulted group was subjected to a 14-day period of feed withdrawal, and the fully-fed group was offered a standard layer ration. After feed treatment, the crop, ileum, caecum and ovary were collected and subjected to a series of treatments to prepare them for incubation with SE. This was followed by the removal of bacteria that had not penetrated the tissues, and the counting of SE that remained in the tissues.
SE invasion of the ovaries was reduced in tissues from moulted hens in trials 1 and 2 compared with full-fed controls (>1.2 log reduction) but not in trial 3. Salmonella invasion of the caeca of moulted hens was numerically increased in trials 1 and 2 and significantly increased in trial 3 compared to the controls (>0.8 log increase). No significant differences in SE invasion were detected for crops and ileum.
— Moore R.W. & P.S. Holt, 2006. The effect of feed deprivation on tissue invasion by Salmonella enteritidis. Poultry Science, 85: 1333-1337
Foot pad dermatitis could be eliminated through breeding
Interesting work by a group of Danish researchers hints that it may in future be possible to select against the susceptibility of broilers to foot pad dermatitis (FPD) without adversely affecting performance.
Scientists at the Danish Institute of Agricultural Sciences in Tjele found that, at 0.31, the heritability for susceptibility to FPD pad lesions was quite high compared to the heritability for bodyweight. The heritability of hock burn (HB) susceptibility, however, was only 0.08 and so a solution to this condition through selection is unlikely.
A total of more than 2000 birds from 2 strains (fast-growing and slow-growing) were allocated to groups in two time-separated replicates. The development of FPD and HB were recorded weekly from day 8 to slaughter on a sample of the live animals. The feet and hocks of all birds were investigated at slaughter (4 or 6 weeks for the fast-growing strain and 8 or 10 weeks for the slow-growing strain).
No FPD lesions and very few low-grade HB were found in slow-growing birds. In the fast-growing strain, the first signs of both lesions were seen in week 2, and the incidence of both types of lesions increased thereafter. Bodyweight did not affect FPD but more HB was found at higher bodyweights.
— Kjaer J.B. et al., 2006. Foot pad dermatitis and hock burn in broiler chickens and degree of inheritance. Poultry Science, 85: 1342-1348
Egg turning angle & frequency impact on embryo position
In a co-operative project between the universities of Ankara, Turkey and North Carolina State, USA, it was concluded that the incidence of malpositioned embryos was increased by a reduced turning angle. However, the effect was ameliorated by increasing the frequency of turning. The work was reported by Drs Elibol and Brake.
Two experiments, each comprising two trials, were carried out to determine if a turning angle of less than 45 from vertical could be successful in terms of the number of malpositioned embryos, i.e. with the head at the narrow end of the egg.
Hatching eggs from commercial broiler breeder flocks aged 55-61 weeks were turned at angles of 35 , 40 or 45 degrees every hour for 18 days in experiment 1. Turning angle had no effect on fertile hatchability but the incidence of malpositioned embryos was higher in the eggs turned at 35 degrees than with the other treatments.
In experiment 2, eggs were subjected to turning angles of 35 and a turning frequency of every 60 or 15 minutes, or 45 every 60 minutes. This time, turning angle and frequency had no effect on fertile hatchability or embryonic mortality. However, the incidence of malpositioned embryos was higher in the group turned with a 35 angle hourly than with the other treatments.
— Elibol O. & J. Brake, 2006. Effect of egg turning angle and frequency during incubation on hatchability and incidence of unhatched broiler embryos with head in the small end of the egg. Poultry Science, 85: 1433-1437
Why is the avian ‘flu virus so dangerous for humans?
Scientists have established a theory why the H5N1 strain of avian influenza (AI) virus is so dangerous for humans. The disease so far has been fatal in more than half of the people who have contracted it since 2003.
The explanation lies in the patient’s viral load and the subsequent inflammatory response, say researchers from the Oxford University Clinical Research Unit in an article published in Nature Medicine.
Dr Menno de Jong and colleagues assessed 27 people at the Hospital for Tropical Diseases in Ho Chi Minh City, Vietnam. Eighteen of the patients were infected with H5N1; the other nine had contracted common human influenza viruses.
The investigators learned that those who had H5N1 were carrying substantially higher viral concentrations in their blood and throat than their counterparts who had sub-types of human ‘flu. The H5N1–infected patients who died had much higher viral loads than those who survived.
The team concluded that the higher the level of H5N1, the greater the likelihood of death. The severity of lung damage and the increased risk of dying probably were associated with high levels of cytokines, low levels of lymphocytes and the resulting intense inflammatory responses in H5N1 patients, the scientists suggested.
Early diagnosis and effective treatment with anti-virals – such as Tamiflu and Relenza – to prevent an intense cytokine response ought to be the primary focus of clinical management, they advised.
— Nature Medicine
Enriching chicken with vitamin E
A group of scientists working in Barcelona, Spain, have found that the vitamin E level in chicken meat can be boosted by feeding higher levels of α-tocopheryl acetate to the birds. Furthermore, the content was maintained, even after 7 months of storage at minus 20 C. The meat could supply about 25% of the recommended dietary allowance.
A factorial design was used for the experiment: three different dietary fat sources (beef tallow, fresh and oxidised sunflower oils and linseed oil), α-tocopheryl acetate (0 or 225mg/kg feed), and ascorbic acid (0 or 110mg/kg/feed).
Raw meat fatty acid composition was affected by dietary fat sources and tocopheryl acetate supplementation. After cooking, it was only affected by dietary fat source. Birds fed linseed oil yielded meat rich in n-3 fatty acids, especially linolenic acid, and the meat would provide about 20% of the recommended intake for this fatty acid. Birds fed fresh or oxidised sunflower oil produced meat rich in n-6 fatty acids, while those fed beef tallow had meat rich in saturated and monounsaturated fatty acids.
The α-tocopherol content of raw and cooked dark chicken meat was only affected by tocopherol supplementation.
— Bou R. et al., 2006. Effects of various fat sources, α-tocopheryl acetate and ascorbic acid supplements on fatty acid composition and α-tocopherol content in raw and vacuum-packed, cooked dark chicken meat. Poultry Science, 85: 1472-1481