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Atlanta Poultry Forum Offered New Insights on Feed Ingredients and Additives

05 March 2014

Among the 140 papers presented at the International Poultry Scientific Forum in Atlanta in January were those reporting research into a range of feed-related topics, writes Jackie Linden. Included in this article are those offering insights into the feeding value of newer feedstuffs and feed additives, strategies for hot weather and for hens in aviaries and how antibiotics affect the environmental impact of broiler production in the US.

Broiler Growth More Affected by DDGS Inclusion Level Than Oil Content

New data from an experiment at Auburn University suggests that increased inclusion rate of distiller’s dried grains with solubles (DDGS) had a more pronounced effect than DDGS oil content on the performance and processing yields of broilers to 33 days of age.

W.A. Dozier explained that the test diets contained low-, moderate- or high-oil DDGS at moderate and high inclusion rates. The three sources of DDGS had ether extract contents of 6.1, 8.8 and 11.6 per cent (dry matter basis).

The diets contained maize, soybean meal, animal protein meal and one of three DDGS sources - five, seven or nine per cent (moderate inclusion rate) or eight, 10 and 12 per cent (high inclusion rate), respectively in the starter (days 1 to 14), grower (days 15 to 25) and finisher (days 26 to 33). Apparent metabolisable energy and digestible amino acid values of the three DDGS sources had been determined from previous research at the Auburn laboratory.

Diets varying in DDGS source did not alter bodyweight gain or feed conversion in this study.

However, broilers fed diets formulated to the moderate inclusion rate of DDGS grew faster and more efficiently from days 1 to 25 and 1 to 33 than those given diets containing the higher inclusion rate.

The researchers noted significant interactions for feed conversion (days 1 to 25), carcass yield, total breast meat yield, wing yield and abdominal fat percentage; birds fed diets containing high-energy DDGS at moderate inclusion rate had superior results for these parameters than the other dietary treatments.

Feed Adjustments Help Broilers Cope with Heat Stress

The results of a floor pen experiment evaluating the effect of maize particle size in combination with either time-limited or ad libitum feeding on the performance of broilers to 49 days of age were reported by Satid Auttawong from North Carolina State University.

Feeding coarse maize and time-limited feeding significantly improved adjusted feed conversion ratio of the birds in this experiment. Adjusted feed conversion ratio was used as there were differences in mortality; the mechanism responsible for decreased mortality of broilers grown in hot weather may be a lower body temperature, the researchers commented.

Male chicks were fed either finely ground maize (ground with a hammermill to 262 microns; 2.4-mm screen) or coarsely ground maize (ground with a roller mill to 1082 microns) or various combinations of these two materials in the starter, grower and finisher.

Birds fed the coarsely ground maize consumed less feed but there were no treatment effects on bodyweight, mortality or cloacal temperature at 49 days of age, so this treatment resulted in the best adjusted feed conversion.

Feed intake and bodyweight were increased by ad libitum feeding but time-limited feeding improved adjusted feed conversion ratio and decreased mortality to 49 days of age.

Investigating Optimum Limestone Particle Size for Pullets

A study at University of Nebraska, Lincoln, reported by Pamela Eusebio-Balcazar, evaluated the carry-over effects of limestone particle size fed to two different layer strains housed in aviaries or cages.

The mixture of fine and coarse particle sizes of limestone in the pullet diet positively influenced eggshell percentage and keel bone integrity during the layer phase.

Pullets were given diets containing either fine (F) or a blend of fine and coarse particle size (FC) limestone (Unical S=0.431mm versus FreFlo=0.879mm; ILC Resources, Des Moines, Iowa) from seven to 17 weeks of age.

The two strains were Lohmann Brown (B) and Bovan White (W). In the same environmentally controlled room, pullets were housed in aviary units (A) or cages (C). Those destined for the aviaries were reared in litter floor pens until six weeks of age, while those destined for the cages were reared in brooder batteries to 10 weeks of age.

The limestone with mixed particle sizes increased eggshell percentage at 41 weeks and reduced keel bone fracture incidence for W hens and reduced keel bone depression incidence at 54 weeks. It did not influence hen bodyweight, bone mineral density or egg production.

The researchers observed differences between the strains in terms of bodyweight, egg production, egg size and bone parameters, as well as some interactions between strain and housing system.

Birds housed in the aviaries were heavier and produced fewer eggs than those in cages at some time-points and their eggs were heavier, had stronger egg shells and had a higher eggshell percentage at some stages. They also had a higher incidence of keel bone depression incidence than the caged hens.

Effects of a Mycotoxin on Broiler Health and Performance

There are more than 400 different mycotoxins worldwide with trichothecenes forming the largest group, according to Karin Naehrer of Biomin Holding in Austria. This group comprises type A (e.g. T-2 toxin and diacetoxyscirpenol) and type B (e.g. deoxynivalenol and nivalenol). The most important source of trichothecenes contamination in cereal grains today is the Fusarium head blight, which is primarily caused by type-B trichothecene producers.

Due to its worldwide distribution in cereal grains as a common contaminant in animal feed, deoxynivalenol (DON) is one of the most important mycotoxins in the trichothecenes group.

Dr Naehrer reported a trial conducted to evaluate the efficacy of a mycotoxin-deactivating product (Mycofix® Select; MSE) in broiler diets to reduce the adverse effects of DON.

Contamination of broiler diet with DON adversely affected the growth of broiler chickens as well as damaging the DNA of blood lymphocytes and inducing lipid peroxidation and oxidative stress in the jejunal tissue. It also induced other changes suggesting an impairment of immune function.

Addition of MSE to the DON-contaminated diet counteracted these adverse effects.

Dr Naehrer said that, to counteract the effects of mycotoxins, applying an effective and long-standing mycotoxin risk management approach is crucial to minimise losses arising from the presence of these mycotoxins in animal feeds.

Effect of Organic Acids in Feed or Water on Salmonella Typhimurium in Broilers

Three trials were performed to evaluate the effectiveness of formic acid and propionic acid on environmental and caecal recovery of the potential foodborne pathogen, Salmonella Typhimurium, reported Kim Wilson of the University of Georgia.

In two of the experiments - when the birds were exposed to Salmonella seeders for one week - those given formic acid in feed and water had the lowest recovery of Salmonella. Those given 5kg per ton of propionic acid for the six-week growing period showed no detectable levels of Salmonella in the caeca, litter or breast skin at the end of that time.

The other experiment - the first - had resulted in no treatment differences, which the researchers attributed to high exposure of Salmonella from seeders in the challenge pens for three weeks and low exposure in the other pens.

In the second trial, chicks were allocated to one of four treatments, namely formic acid in feed or water or both; there was also a negative control without formic acid. The lowest recovery of Salmonella from the caecum was from the group receiving formic acid in both feed and water.

The third experiment included propionic acid treatments; formic acid was included in the feed at 4 or 6kg per ton for the last two weeks of grow-out and this was compared with 5 or 10kg per ton of propionic acid in the feed for the whole six-week growing period or just the last two weeks; there was also a negative control.

At the end of the experimental period, the group on the low level of propionic acid throughout the six-week period had no Salmonella-positive caeca or litter in all pens. Those groups receiving the acids in weeks 5 and 6 as a clean-out supplement had at least one Salmonella-positive caecum. Only the negative controls had Salmonella-positive breast skin (20 per cent) following scalding and defeathering.

In-feed Antibiotic Reduces the Environmental Impact of Broiler Production

A study reported by Cody Brown from the University of Georgia aimed to compare responses of an antibiotic (virginiamycin; 20ppm) and/or a multi-enzyme product (Rovabio; 0.05 per cent) on the environmental impact of broiler production in the US, using typical commercial diets that were formulated to be low in energy (-110Kcal per kg) and contained wheat, distiller’s dried grains with solubles (DDGS) and poultry by-product meal.

Despite the low-energy formulations, the birds in all groups grew faster than the breed standard. The best final weights (at 35 days) were achieved by the group receiving the antibiotic; the enzyme had no significant effects on performance.

Calculating the maize and soybean meal savings from feeding the antibiotic to broilers, the authors made a conservative assumption that feed additives like virginiamycin are capable of improving bodyweights by one per cent, feed conversion by two per cent and carcass yields by 0.5 per cent.

They calculated that yearly savings for a complex processing 1.2 million birds per week would amount to 410 hectares of maize and 724 hectares of soybeans with harvests typical of the US. Yearly savings for the national flock are of the magnitude of 55,000 hectares of maize and 98,000 hectares of soybean meal, they estimated.

Adding Phytase to Diets Containing Low-phytate Soybean Meal for Broilers

An experiment investigating the effects of adding phytase to low-phytate and normal phytate soybean meal diets on performance, phosphorus digestibility, bone ash and bone strength of male broilers was reported by Basheer Nusairat from North Carolina State University.

Adding phytase to the diet with low-phytate soy had adverse effects on live performance, bone breaking strength and the percentage of bone ash. The researchers attributed these effects to a dietary imbalance associated with increased phosphorus digestibility.

As in previous trials, phytase improved live performance and phosphorus digestibility in birds fed the diets containing normal phytate soybean meal.

In this experiment, male broiler chicks were fed a typical maize-soybean diet, without phytase to nine days of age.

From 10 to 35 days, they received diets with low- or normal-phytate soybean meal, with or without phytase addition.

From 23 to 35 days, feed intake decreased when phytase was added to the low-phytate soy diet and bodyweight was reduced at 35 days.

Phytase improved phosphorus digestibility, decreased bone strength for both soy types and reduced bone ash in the low-phytate soy-based dietary treatment.

Microalgal Feed Additive Affects Broiler Health

The long chain n-3 fatty acids, particularly docosahexaenoic acid (DHA, 22:6), are very important in the structure and function of cellular membranes, according to Lizza Macalintal from the Alltech-University of Kentucky Nutrition Research Alliance in her introduction to a study of the effects of dietary supplementation of microalgae on growth performance, immunity and fatty acid profile of broiler chicks.

Previous studies indicated that DHA provides unique properties to the lipid bilayer of cell membranes and contributes to membrane plasticity, fluidity and permeability, she said. These properties play a direct role in a variety of cellular and multicellular processes, including inflammation and immunity. Microalgae contain high amounts of omega-3 fatty acids, particularly DHA.

From their results, the researchers concluded that dietary supplementation of SP-1 enriched  omega-3 fatty acid deposition in fat tissue and enhanced the immune response.

Chicks were fed maize-soybean meal diets containing 0, 0.5, 1.0 or 2.0 per cent Schizochytrium sp (SP-1, Alltech, Inc.) for 28 days. 

The addition of SP-1 did not affect the birds' feed intake, weight gain or feed conversion ratio to 21 days of age. However, linear increases were observed in the concentrations of DHA, eicosapentaenoic acid and total omega-3 FA in the abdominal fat with SP-1 supplementation.

Compared to other treatments, higher IgM titres persisted for 14 days after the first injection of sheep red blood cells for those birds fed diets with SP-1, and IgG titres were higher in this group seven days after a second injection.


Auttawong S. et al. The effects of corn particle size and time-limited feeding on broiler live performance during hot weather rearing.

Brown C. et al. The environmental impact of broiler production as influenced by virginiamycin and a feed enzyme.

Dozier W.A. III and J. B. Hess. Growth and meat yield responses of Hubbard × Cobb 500 male broilers fed diets formulated with distiller’s dried grains with solubles varying in ether extract content and inclusion rate from 1 to 33 days of age.

Eusebio-Balcazar P. et al. Effects of limestone particle size in pullet diets on hen performance, bone mineral density and keel bone deformities in aviaries or conventional cages.

Macalintal L. et al. Effects of dietary supplementation of microalgae on growth performance, immunity and fatty acid profile of broiler chicks.

Nusairat B. et al. Effect of adding phytase to low phytate and normal phytate SBM diets on male broiler live performance, phosphorus digestibility, bone ash, and bone strength.

Naehrer K. et al. Effects of deoxynivalenol on selected parameters of health performance in broiler chickens and the efficacy of a mycotoxin-counteracting feed additive.

Wilson K. et al. Evaluation of formic acid and propionic acid feed additives on environmental and caecal Salmonella Typhimurium in broilers.

All papers were presented at the 2014 International Poultry Science Forum, Atlanta, Georgia, US.

March 2014

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