How much dried distillers grains with solubles (DDGS) can be included in poultry diets without affecting flock performance? What's the best way to evaluate the application of combinations of disinfectants in poultry processing? These and many other questions were answered by research presented at the International Poultry Scientific Forum. Both platform and poster presentations dealt with basic and applied studies at universities and government research facilities.
Microbiological quality
HIMP processing validated. Scientists at the USDA-ARS Russell Research Center presented data on processing plants operating according to the HACCP-Based Inspection Models Project (HIMP). Data comparing recovery of Salmonella spp., E. coli and Campylobacter spp. before and after chilling were compared.
The number of Campylobacter spp. at re-hang ranged from 0 to 3 CFU/mL on carcass rinses. Chilling reduced numbers to a range of zero to 0.69 CFU/mL with a mean of 0.04 CFU/mL. Recovery of E. coli was lowered from a mean of 2.88 CFU/mL to 0.49 CFU/mL post-chill. The equivalent values for recovery of Salmonella ssp. extended from zero to 100 percent of carcasses with a mean of 54 percent. Although the range for post-chill spanned from 0 percent to 60 percent, the average of 11 percent is approximately half the USDA upper limit of 20 percent.
This data can be compared to the survey conducted in 2004 which showed essentially similar values at post-chill although there were reductions in the levels of microbial contamination at re-hang. The most recent study confirms the value of the HIMP Program, which involved over twenty plants at the time of the survey.
Model for evaluating combinations of disinfectants. In a related presentation, scientists at the Russell Research Center evaluated mixtures of potassium hydroxide and lauric acid to reduce bacterial contamination of skin. Successive washes were carried out with a range of concentrations of the two compounds. Total plate count and enumeration on specific selective media were used to quantify levels of bacterial contamination. Repeated washing did not significantly lower microbial levels, although 0.25 percent and 0.5 percent potassium hydroxide were effective after the first wash. This study demonstrated the suitability of the model to evaluate wash solutions and may lead to new methods of applying combinations of disinfectants and surfactants to improve microbial quality and extend shelf life.
Nutrition
Dried distillers grains with solubles. Escalation in the cost of corn is a result of diversion of feed grain to ethanol production. Considerations of cost and availability dictate the incorporation of dried distillers grains with solubles (DDGS) in poultry diets. Studies conducted by the University of Georgia in conjunction with two manufacturers of synthetic amino acids evaluated incremental inclusion of 0 percent to 25 percent DDGS in broiler diets. At 42 days of age, feed conversion, body weight gain, breast meat yield and fat pad were not affected by any of the levels of DDGS when compared to a corn-soy basal diet. It is important to note that diets were isonitrogenous and adjusted to contain equal quantities of lysine and sulfur-containing-amino acids. Due to the higher levels of fat in DDGS, pellet durability was markedly affected by increasing levels of DDGS.
Upper limit for glycerin? Glycerin is a by-product of producing diesel fuel from vegetable oils. A series of isocaloric diets were formulated containing incremental levels of glycerin in various combinations with poultry fat. Increasing dietary levels of glycerin above 2.5 percent depressed body weight gain and feed intake. This value appears to be the upper limit of inclusion of glycerin, which contains methanol as a contaminant.
Evaluating sex-separate grow-out. In contrast to the European Union, the USA has limited application of separate-sex grow-out. Studies conducted at Mississippi State University evaluated the lysine requirement of male and female broilers over 14 days to 28 days of age. Digestible lysine values ranging from 0.85 percent to 1.25 percent were evaluated by supplementing a corn-soy-peanut meal diet with synthetic lysine. The digestible lysine requirement to support optimal body weight, gain and feed conversion was estimated to be from 1.10 percent to 1.13 percent. A comparative trial on female broilers suggested a digestible lysine requirement estimate of 1.06 percent based on 95 percent of the minimum response to a diet containing excess lysine.
Although minor differences in male and female nutritional requirements can be determined under experimental conditions, the practical application of these values is limited. In reality, the inherent variation in quality of ingredients incorporated into diets will result in differences greater than the range considered in these two trials.
Logistical considerations and hence costs relating to separate-sex rearing include feather sexing at the hatchery, scheduling of grow-out placements and harvest and arranging for the correct duration of withdrawal feeds. These factors have limited separate-sex growing in the USA and will probably preclude further expansion of this practice. Advances in first-processing equipment and technology have largely negated the justification for separate-sex programs, which were a common practice in the UK during the 1980s and 1990s.
Welfare of poultry
Flock gait scoring. A combined study by the University of Georgia and Mississippi State University compared the UK Kestin scoring system and a simpler U.S. System to derive a flock gait score to determine whether broilers in a flock are affected with musculoskeletal abnormalities.
The Kestin System involving six categories is considered to be too complicated and possibly unrealistic to evaluate heavy broilers at six weeks of age under U.S. conditions. A simpler three-category scoring system was evaluated by trained observers. There was significant inter-observer agreement in each system but the Kappa statistic favored the U.S. system indicating greater consistency. The scores using the U.S. and Kestin evaluations were statistically significant justifying the use of a three-category evaluation.
Producers in the USA have been subjected to inappropriate standards adopted by "advisory panels" based on UK and EU research. It is hoped that the three-category scoring system will be used for further welfare audits. Assessing locomotory dysfunction is extremely difficult for untrained observers, based on the disinclination of heavy strain broilers to voluntarily move as they mature from "ballerinas" at two weeks of age to "sumo wrestlers" at seven weeks.
Photoperiod and intensity of illumination for broilers are contentious topics. The National Chicken Council (NCC) Guidelines were compared to proposed EU Standards in a comprehensive trial conducted at Auburn University. Each of the programs was compared at low U.S. levels of intensity (0.025 foot candle, weeks 2 -7) or the brighter EU values (2 foot candle). No details were provided for relative performance under alternative programs. Broilers subjected to high light intensity showed higher levels of fear and aggression but neither stress nor movement were affected by duration of photoperiod.
Flock health
Avian reovirus. Application of advance molecular biological techniques has facilitated a greater understanding of the epidemiology of broiler diseases. Real-time reverse transcriptase polymerase chain reaction (RT-PCR) assays can now be used to identify avian reovirus strains. This sensitive procedure was able to detect shedding of reovirus within two days after infecting chicks. It was also observed that the chicks derived from vaccinated parents carrying maternal antibodies showed a lower rate of excretion of a known enteric strain (2408) which is associated with malabsorbsion.
Laryngotracheitis strains. Genomic analysis based on RT-PCR followed by sequencing of specific regions of the genome enabled a research group at the University of Georgia to classify laryngotracheitis strains into nine biotypes. Type IV corresponds to the chick embryo origin vaccine and this biotype together with V and VI is most frequently isolated from broilers under commercial conditions. In contrast, biotypes VII through IX are usually encountered in backyard flocks.
Efficacy of LT vaccine. A companion study also conducted at the University of Georgia developed a challenged model to determine the efficacy of LT vaccine. It was demonstrated that tissue culture origin products provided adequate protection against clinical signs in vaccinated and challenged broilers. Non-vaccinated birds and non-vaccinated contact birds showed clinical signs including conjunctivitis and lachrymation associated with propagation of virus which could be reisolated from tracheal and cloacal swabs. Studies on laryngotracheitis are important based on the extensive prevalence of the infection in the U.S. industry.
Understanding Salmonella enteritidis. Studies on Salmonella enteritidis conducted at the University of Georgia applied random polymorphic DNA amplification-PCR to differentiate among isolates. Genetic differences which cannot be discerned using conventional pulse-field gel electrophoresis will lead to an understanding of the method of dissemination of this pathogen in integrated operations. This is a necessary pre-requisite for developing effective control and eradication procedures.
The International Poultry Scientific Forum is sponsored annually by the U.S. Poultry & Egg Association.
