Lameness in poultry is a major concern for the industry due to its negative implications for both bird welfare and productivity levels, explained Fiona Short of Nottingham Trent University in the introduction to her paper reporting two experiments looking at the effects of a novel form of dietary silicon supplement in reducing lameness in poultry (1).

The results of the first indicated that the supplement has the capacity to reduce lameness in broilers and hence silicon may have a role in improving bird welfare. Using the highest level of inclusion (1,000ppm), clearly fewer birds were unable to stand than the other treatments and more of them stood without encouragement. The second trial demonstrated that the silicon was easily absorbed as the serum silicon concentration was dose-dependent. Overall, the researchers concluded that the novel form of silicon supplementation has high bioavailability. Larger-scale studies are needed to substantiate its potential role as a commercial supplement for reducing the incidence of lameness in broilers, they added.

Bristol University scientists have been examining the possibility of using diets with additional ω-3 fatty acids as a means to improve bone strength and reduce keel bone fractures in laying hens. These fractures are a significant welfare issue, explained Dr Michael Toscano, as evidence has been found of new or old breaks in up to 70 per cent of free-range hens (2). Early research with diets containing short-chain ω-3-enhanced diets were effective in reducing keel bone fractures but they also adversely impacted egg production.

In experimental pens, 23-week-old layers were given one of four diets ranging in ω-3:ω-6 ratio between 0.12 and 1.35, with the ω-3 source being a mixture of flaxseed and salmon oils.

There was no treatment effect on the presence of keel bone fractures, and the number of poor quality shells was found to correlate positively with ω-3:ω-6 ratio in a dose-dependent manner. Looking at the Campylobacter concentration in the caecum, the Bristol researchers found a treatment effect of a parabolic nature and a peak at 0.36 ω-3:ω-6 ratio.

Dr Toscano said the data indicate that some of the long-chain ω-3 diet's negative impacts, e.g. poor egg quality, can be alleviated while sufficient ω-3 egg yolk quality is maintained by providing a mixture of short- and long-chain ω-3 content. Benefits of mixed ration to bone and overall health issues are less clear and require further research, he added.

Wet litter is a multifactorial problem, which has implications for welfare as well as carcass quality issues owing to the links with foot and leg problems and breast blisters in poultry. Soybean meal has been identified as a cause of wet litter. The aim of a study by M.W. Mirza of SAC, presented by Dr Vasil Pirgozliev, was to gain understanding of the relative importance of the protein and potassium in soybean meal on water intake and excretion by turkeys (3).

The results of the study indicate that it is the protein rather than potassium that is the main driver of water intake in turkeys. Dietary potassium may influence water output but the effect of crude protein is more pronounced.

Turning to the effects of feeding on health, researchers at Scottish Agricultural College (SAC) looked at the impact of feed withdrawal on sub-clinical necrotic enteritis. The withdrawal of antimicrobial growth promoters has been accompanied by a resurgence in sub-clinical necrotic enteritis, a disease caused by Clostridium perfringens, explained G. Saleem and colleagues (4). Field evidence indicates that subclinical necrotic enteritis occurs after some disruption to feeding, such as a failure in the feeder system.

The results from SAC showed that the duration of feed withdrawal imposed in the present study did not predispose the birds to necrotic enteritis, with no specific lesions observed and the C. perfringens count in the digesta was low. Feed withdrawal alone does not appear to predispose birds to necrotic enteritis.

Novel Feeds and Additives

There have been a multitude of studies investigating the effects beta-glucanase in broiler diets but the use of this feed enzyme for laying hens has been neglected, according to Dr Helen Masey O'Neill of AB Vista Feed Ingredients, reporting a trial carried out in China (5).

Feeding different levels of beta-glucanase to laying hens from 19 to 48 weeks of age in a diet based on wheat and barley and fed as mash, she and her co-authors concluded that beta-glucanase supplementation can improve the laying performance of hens. In each phase of the trial, laying rate and egg mass were significantly higher for the enzyme-supplemented groups than the for the control (P<0.05). However, they noted that, while the benefit of the enzyme was noted within the first 10 weeks of the start of the study, the FCR benefit took considerably longer to develop. Furthermore, the scale of the response to the enzyme seemed to increase with time, in terms of egg mass, laying rate and FCR.

These birds were fed one diet consistently throughout the study. It is possible that more consistent results in egg weight and FCR may be achieved if diets were formulated on a phase basis, added Dr Masey O'Neill.

The rising production of biofuels in the European Union has prompted interest in altering the bio-refining process to improve the nutritive value of the co-products, said Dawn Scholey of Nottingham Trent University, reporting part of her PhD thesis (6).

She and her co-authors fed to broilers from day-old to 15 days of age wheat and soya-based diets containing zero, three, six or nine per cent of two fermented wheat co-products, one from a potable alcohol source and one from a bioethanol source.

Both yeasts increased broiler weight gain at the lower inclusion level. The researchers noted an increase in digesta viscosity for the product from potable yeast production, which could limit its use as a feed ingredient and so they concluded that the yeast derived from bioethanol production appeared to provide a viable alternative protein source for broiler starter diets.

From the University of Developmental Studies in Ghana, H.K. Dei reported an evaluation on the nutritive value of Icacina oliviformis seed meal in broiler diets (7). He explained that I. oliviformis is commonly known is the false yam and that it is a drought- and fire-resistant shrub that grows widely across the savannah regions of West and Central Africa. Its high starch content indicate that Icacina may be a suitable substitute for maize in broiler diets.

The seeds were fed either raw or after processing by boiling or soaking and then drying. Health status of the birds was not affected by treatment and the researchers concluded that processing Icacina seeds by soaking in water improved its nutritive value for broilers up to 100g/kg in the diet.

References

All papers were presented at the WPSA UK Branch Annual Meeting in Nottingham on 4 to 5 April 2011.

1. Short, F.J., E.J. Burton, D.J. Belton, G.E. Mann and C.C. Perry. Efficacy of a novel form of dietary silicon supplement in reducing lameness in poultry.
2. Toscano, M., F. Booth, T. Cogan, L. Williams and J. Tarlton. Identifying an optimum ω-3:ω-6 dietary content to improve bone health for laying hens with minimal impacts on production end-points.
3. Mirza, M.W., V. Pirgozliev and N. Sparks. The effect of dietary crude protein and potassium on water intake and excretion by turkeys.
4. Saleem, G., N. Sparks, J. Houdijk, T. Acamovic and V. Pirgozliev. Does feed withdrawal assist experimental induction of sub-clinical necrotic enteritis in broiler chickens?
5. Masey O'Neill, H.V., M.R Bedford and N. Liu. The effect of beta-glucanase on the performance of laying hens fed barley/wheat based diets.
6. Scholey, D.V., N.K. Morgan, P. Williams and E.J. Burton. Effect of incorporating a novel bioethanol co-product in poultry diets on bird performance.
7. Dei H.K., R.A. Adjokatse, S. Abdulai, G.K. Amoako, A. Mohammed an G.A. Teye. Evaluation of nutritive vale of Icacina oliviformis seed meal in broiler chicken diets.

August 2011