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This article was published in 1962
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Recent Progress in Poultry Research
Poultry Research Station, Seven Hills
M. W. McDONALD, M.Sc.Agt, Ph.D., Senior Livestock Research Officer
INTRODUCTION
The Poultry Research Station, Seven Hills has played a leading role in the scientific development of the Poultry Industry. A measure of this was provided in a recent review of poultry nutrition research in Australia; of 40 scientific papers cited as containing original information in this field, 22 originated from this Station.
Originally the Station was located in the middle of a belt of poultry farms, stretching from Liverpool to Pennant Hills and containing almost one third of the laying hens in Australia. Encroachment on this area for urban development has tended to isolate the Research Station among intensive housing developments. While this has reduced the direct contact between the Station staff and the poultry industry, it is hoped that there will be no reduction in the impact of the research.
As the poultry industry has developed from extensive or sideline farms to intensive units, exemplified by laying cage or broiler farms, the nature of the investigations carried out at the Research Station has changed also. There has been a steady evolution in the approach to the industry's problems, from the conducting of simple and practical trials to the present stage where the research is largely fundamental in character and aimed at assisting the long term evolution of the poultry industry.
The following summarises current investigations at the Research Station:—
1. Sodium metabolism of poultry
Following work published by Beilharz and McDonald (1960) indicating that the feeding of high levels of sodium in chicken diets could increase the susceptibility of the chicken to renal damage, loosely referred to as "uraemia" by the poultry industry, there has been a tendency towards the reduction in the sodium level of diets fed to poultry. This has been produced both by the feeding of feedstuffs low in sodium, and the reduction in the amount of common salt added to the diets.
Preliminary work on the need for salt supplementation of laying diets highlighted the inadequacy of the evidence upon which the estimates of sodium requirements of laying birds and growing chickens were based. A series of experiments designed to estimate these requirements has been undertaken. Sodium requirements of growing chickens are believed to be between 0.18 and 0.25 per cent. sodium, and of laying hens at about 0.20 per cent of the diet. An interesting observation of reduced egg size in sodium deficiency was made.
Because of the similarity between the "uraemia" syndrome in chickens and adrenal failure in other species, a study of adrenal changes with sodium intake in chickens has begun. Chickens fed extremely low levels of sodium for five weeks demonstrated very severe adrenal hypertrophy which was found on histological examination to be associated with considerable disorganisation of the tissues of this gland. Minimum adrenal size was observed at 0.18 per cent sodium in the diet. Levels of sodium higher than this figure tended to produce adrenal hypertrophy suggesting increased adrenal activity associated with the excretion of the excess sodium.
This evidence provides a clearer picture of the nature of the "uraemia" syndrome, which is considered now to be adrenal failure as a result of stress and/or excess intake of sodium or phosphate. The nature of the stress producing the final collapse in the birds may vary from infection to poultry management.
Breeding Diets and Hatchability
McClymont and Duncan (1955) and McDonald and McClymont (1955) concluded that riboflavin (vitamin B2) was the only nutrient likely to be deficient in a typical laying diet responsible for the depressed hatchability observed at that time. Addition of all available B vitamins failed to increase hatachability more than riboflavin alone.
These conclusions have been re-examined and it has been found that the addition of a more complex vitamin mixture does result in a sufficiently large increase in hatchability to justify the increased cost of the diet. The following Table summarises the results of three experiments supporting these conclusions:—
| Chickens hatched per 100 eggs incubated | ||
|---|---|---|
| Control | Complex Vitamin Mixture | |
| Experiment I B Vitamin mixture |
70.0 | 78.0 |
| Experiment II Vitamin E and K + B vitamins |
71.2 | 75.4 |
| Experiment III as Expt. II |
70.3 | 79.3 |
| Average | 70.5 | 77.6 |
In future experiments it is hoped to investigate the additive producing this effect.
Early Deaths in Chickens
The loss during the first few weeks of life of between 2 and 7 per cent of all chickens started represents a considerable economic burden on the poultry farmer. Control of such diseases as Pullorum and Paratyphold has reduced this problem but there is still a consistent loss.
Among the factors that have been identified as being associated with the incidence of deaths are genetic effects and the washing of eggs before incubation. The storage conditions of the fertile eggs have been eliminated as a factor in chicken neo-natal deaths.
Recent results indicate that maternal diet may be a factor of considerable importance to this problem. The following Table illustrates the decreased mortality associated with feeding a more complete maternal diet.
| Deaths in the first 2 days after hatching | ||
|---|---|---|
| Maternal Diet | Control | Supplemented with Complex vitamin mixture |
| Experiment I | 6.0 | 5.1 |
| Experiment II | 4.8 | 2.6 |
| Average | 5.4 | 3.9 |
Pyridoxine (Vitamin B6) in Chicken Diets
Improved growth and feed conversion have been observed following addition of pyridoxine, 2 parts per million, in standard chicken diets. This is the first time that a pyridoxine deficiency in a practical diet has been observed.
Using published values for pyridoxine content of feedstuffs, it has been calculated that the diets used should contain between 4 and 5 parts of pyridoxine per million. When compared with the estiate requirement of chickens for this vitamin, 3.5 parts per million, there is an apparent discrepancy.
The possibilities that might account for this result:
1. One or more feedstuffs containing less pyridoxine than previously reported
2. The pyridoxine requirements of chickens being higher than accepted
3. The existence of an anti-pyridoxine factor, similar to that known to be contained in linseed meal, in an ingredient in the diets, are being actively investigated.
References
- Beilharz, R. G. and McDonald, M. W. (1960) — Aust. vet. J. 36: 89
- McClymont, G. L. and Duncan. D. C. — Aust. vet. J. 31: 91
- McDonald, M. W. and McClymont. G. L. — Aust. vet. J. 31: 93