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on June 22, 2009

Research Digest: October 2008

The current research looks at a scalder additive used to control salmonella and how KCl supplementation of heat stressed birds.

Scald additive to reduce Salmonella

Salmonella is major pathogen that can result in foodborne illness. Currently, there are performance standards for salmonella that broiler processors are required to meet. Therefore, intervention strategies in the processing plant are important to help reduce salmonella on poultry. One possible intervention strategy is the use of an alkaline scald additive. RP scald (Duchem Industries, Newnan, GA) is an additive used to reduce the appearance of bruising on carcasses and its active ingredient is sodium hydroxide which is highly alkaline. Scalding temperatures may also affect microbial loads on poultry. Therefore, the purpose of this study was to evaluate the effectiveness of RP scald to reduce salmonella levels on inoculated poultry carcasses when used in either soft scald or hard scald conditions.

In this study, 600 broilers were processed in two trials. Birds were subjected to the following inoculated treatments: soft scald (SS; 122°F for 90 seconds), soft scald with 1.0 percent added RP scald (SSRP), hard scald (HS; 134°F for 45 seconds), hard scald with 1.0 percent added RP (HSRP). Additionally, two noninoculated treatments were included, soft scald (SS0) and hard scald (HS0). After bleedout, birds were inoculated with 2.5 mL of fecal slurry containing 108 Salmonella Typhimurium (ST) along the feather tract directly on the skin. The slurry was allowed to dry for 10 minutes and then birds were scalded (according to treatment) and defeathered. Samples for ST analysis were then collected from the New York dressed carcasses.

In trial 1, there were no samples positive for salmonella in the SS0 or HS0; however in trial 2, these non-inoculated controls were 100 percent and 48 percent positive in the SS0 and HS0, respectively, indicating birds in trial 2 were already contaminated. Therefore, the data from the two trials were presented separately. In trial 1, the temperature of the scald impacted salmonella recovery on carcasses. Scalding with a hard scald (high temperatures) resulted in lower ST levels and salmonella-positive birds than scalding with a soft scald. This trend has been observed by other researchers. After adding RP scald, the ST levels on carcasses were lower than the treatments without the additive, and the percentage of salmonella-positive birds was lower. The authors explained this by the increased pH in the scald water (7.8 to 11.7) and suggested that this mechanism is an effective means of reducing salmonella. In trial 2, the temperature of the scald impacted ST levels similar to observed results in trial 1 where birds subjected to a hard scald had lower ST levels than those subjected to a soft scald. With the addition of the RP scald, ST levels and salmonella-positive birds were reduced. In contrast to results of trial 1, the SSRP had higher ST levels compared to HS suggesting that the RP was not as effective in trial 2. The authors explained this inability of RP to cause greater reductions in the soft scald treatments due to the higher level of background contamination (i.e., SS0 and HS0 were positive). Similar to trial 1, the HSRP had the lowest level of ST and fewest salmonella-positive carcasses suggesting a synergistic effect of high scald temperatures and high pH.

Water samples were also collected and results showed that organic matter was present in the water. Authors suggested that the addition of RP scald was effective in reducing ST levels regardless of organic load. Additionally, it was reported that water samples collected in trials 1 and 2 of the scald water with RP additive were negative for salmonella. The authors explained that this the high pH environment could serve as an antimicrobial in scalds.

The results of this study indicated that the addition of RP scald may be an effective intervention strategy in reducing salmonella in poultry plants. The data also suggest that this additive may be more effective when used in combination with hard scald applications. Because of the high pH of this additive, it is possible that it could inactivate the chlorine in the chillers so the authors stated that proper pH control of the chiller would be necessary to maintain effectiveness of chlorine.

McKee, S.R., J.C. Townsend, and S.F. Bilgili. 2008. Use of a scald additive to reduce levels of Salmonella Typhimurium during poultry processing. Poultry Science 87:1672-1677.

KCl supplementation can improve performance

Heat stress on poultry has many negative impacts on growth performance and even meat quality. In the U.S., poultry are often subjected to high environmental temperatures in the summer season. Feed intake, body weight, and mortality are all factors that can be negatively affected by heat stress and these can result in higher economic losses. Potassium is involved in many metabolic processes and changes in potassium homeostasis can affect cellular functions. Feeding or supplementing drinking water with potassium may elicit favorable changes in the physiological adjustment of heat stressed poultry. The purpose of this study was to determine the effects of two levels of potassium chloride (KCl) supplementation through the drinking water of chickens under heat stress conditions.

One hundred fifty broilers were raised to 42 days of age in three replications and were subjected to average elevated temperatures of approximately 95°F to 100°F during the growout period using heat cycles (approx. 82°F to 100°F). Treatments consisted of supplementing water with 0.3 and 0.6 percent KCl (wt/vol) and a non-supplemented control. Feed intake, body weight gain, and mortality were recorded, and feed:gain ratio was calculated. Additionally, blood pH, rectal temperature, mortality and ready-to-cook yield were measured.

Feed intake was not affected by supplementing water with KCl. However, body weight gain was improved at 28 and 42 days of age in the birds drinking 0.6 percent KCl supplemented water. Supplementing water with 0.3 percent did not affect body weight gain. The authors explained that heat stress leads to lowering of plasma K+ and that the higher body weights in the 0.6 percent treatment may be due to the increase in plasma K+ concentration in this treatment. Feed:gain ratio was improved in the 0.6 percent at 28 and 42 days of age, but the lower level of KCl supplementation did not impact feed:gain ratio. The authors explained that this was improved possibly due to the higher body weight gain resulting from normalization of blood electrolyte balance.

Supplementing the water with 0.6 percent KCl resulted in significantly lower blood pH compared to the control or the 0.3 percent KCl treatment. The authors stated that the blood pH was at a more favorable pH for physiological function. The authors explained that hyperventilation and associated respiratory alkalosis induced by hyperthermia may have led to the higher blood pH in the control and 0.3 percent KCl. However, previous research has not always reported this trend. The authors offered another explanation, the acidogenic effect of Cl- and maintenance of blood electrolyte balance due to increased K+ in the blood. Another possible explanation was that the birds on the 0.6 percent KCl supplementation were better able to adapt to the long term heat stress conditions.

Supplementing water with 0.6 percent KCl also resulted in significantly lower rectal temperatures compared to the control and 0.3 percent KCl treatments which were not different. The authors explained that this was likely due to increased water consumption (not measured in this study) which has been shown to be associated with supplementation of water with electrolytes. This may have also been the reason for higher body weight gain. Supplementing water with KCl did not impact mortality or yield in this study.

The results of this study suggest that supplementing water with KCl can significantly improve performance of heat stressed broilers. However, a minimum of 0.6 percent KCl was required in this study to get the optimum performance under the heat stress conditions of 95-100°F.

Ahmad, T., T. Khalid, T. Mushtaq, M.A. Mirza, A. Nadeem, M.E. Babar, and G. Ahmad. 2008. Effect of potassium chloride supplementation in drinking water on broiler performance under heat stress conditions. Poultry Science 87:1276-1280.

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