Influence of chlorine addition to drinking water of broilers subjected to feed and water withdrawal, before slaughter, on the population of enterococci in the ingluvio

Pre-slaughter fasting, is a routine practice in the poultry industry, the purpose of reducing contamination at the slaughter house, as well as expenses associated to contamination, due to the fact that the feed intake of this animals before processing, is not transformed into meat. Fasting starts at the farm, with the feed withdrawal, but water is still administered until birds are captured (Mendes, 2001). Chlorine is the most used antimicrobial agent during the different stages of food production for human consumption, due to its availability, its relative low cost and its high efficiency (Tsai et al., 1992). The main disadvantage of chlorine is its capacity of binding to organic matter, diminishing its antimicrobial effect (Lillard, 1980; Tsai et al., 1992). Hence, enough amounts of chlorine should be added, in order to produce a free residue. The presence of free chlorine keeps its antimicrobial activity during a longer period and controls the proliferation of microorganisms in the treated water (Gavin and Weddig, 1995). Banhart et al. (1999) stress that tests should be carried out in order to prove the efficacy of the antemortem ingluvio, or crop disinfection, reducing the use of antimicrobial products, at a commercial scale, and diminishing or eliminating the pathogenic load of food origin which could become a serious problem for public health. The aim of this experiment was that of proving the efficacy of the use of chlorine in broiler´s drinking water, since the beginning of the food withdrawal, until the end of the fasting period and the beginning of the capture, in order to reduce microorganisms, such as enterococci in the crops of birds, due to the fact that if one is able of reducing the amount of such germs, it is quite probable that such pathogens will follow the same trend.

Forty Cobb broilers were fed with commercial diets of Purina do Brasil^®, administering the initiator (Inicina^®) up to day 21 of age and growing diet (Nutriengorda^®) until slaughter, according to the recommendations of the manufacturer. Water and feed were administered ad libitum. Twelve hours before slaughter of the birds (42 days old), samples of the crop content were taken for their microbiologic analysis, after the slaughter of 10 birds. The same analysis was repeated at the end of the feed and water withdrawal, 10 more birds from each treatment group were slaughtered, for sampling purposes. A totally random design was used with four treatments (without fasting at the beginning of the pre-slaughter period, 12 hours fasting without the addition of chlorine to water, 12 hour fasting with the addition of chlorine to water and without fasting during the pre-slaughter period), with 10 replications per treatment. The methods of the statistical analysis used were: the variance analysis according to test F and the one of means comparison using the Tukey at 5% of probability test. The Agroestat computing program was used for the statistical analysis. Sample swabs of the internal face of the ingluvio were placed in tubes containing 5 ml of TSB broth. Dilutions were made, adding 5 ml of the solution of the swabs, after homogenization, at 45 ml of peptonated water at 0.1%, in order to obtain a dilution of 10^-1. As of this dilution, decimal consecutive dilutions were done, according to the same proportion. With the dilutions of 10^-1 to 10^-5 of the samples of the cecal content, and of the crop´s swab, three tubes containing Chromocult^® Broth were inoculated with 1 ml, respectively. After inoculation, the tubes were incubated at 35ºC during 24 hours, and those which presented a bacteria growth, characterized by turbidity of the means and a blue greenish coloration were considered as positive. Results were obtained by the comparison of the numbers of the positive tubes with the data of the Table of the MPN, and the enterococci MPN by ml of the solution of the swab transport solution (APHA, 2001) was determined. The salt of the dichloride isocyanide acid (Hidroall do Brasil Ltda. Aviclor choque^â) was used in the drinking water of fasting and water withdrawal birds. In order to determine the concentration of free residual chlorine in water samples, measured at the collection time, NN Dietil Parafenileno Diamino (DPD) reagent and an electronic colorimeter (¹HI93710C-Hanna Instruments) were used. The colorimeter was initially calibrated at zero, with 10 ml of the water sample without the DPD reagent. Reading took place after the addition of the reagent to the container of 10 ml of the sample, homogenizing the sample and proceeding to the reading in mg.L^-1.

Table 1. Most probable number (MPN) of enterococci  (y=log [x+5]) in the crop (MPN. mL^-1 of conservative solution of the swab) in broilers, 12 hours before slaughter, subjected to fasting, or to fasting with the addition of chlorine to the drinking water, or without pre-slaughter period (12 hours)

When comparing the material collected 12 hours before slaughter (without fasting), with those of fasting birds, 12 hours before slaughter, with any type of water treatment (fasting without chlorine in water), a significant difference (P<0.05) in the amount of enterococci in the crop of birds was found. Enterococci values of the fasting birds were higher than those of the birds 12 hours before slaughter. In spite of the fact, that fasting is mentioned as an important factor, in literature, for reducing the contamination in the gastrointestinal tract (Duke et al., 1997; Northcutt et al., 1997), further amounts of enterococci in the ingluvies of birds subjected to fasting than in others were found. This fact may be due to the ingestion of litter during the fasting period previous to slaughter, in spite of the time used for fasting in this experiment, it was in agreement with what is suggested in literature (Smidt et al., 1964; Wabeck, 1972; Veerkamp, 1986; Lyon et al., 1991). In spite of the fact, that the number of enterococci, found in the crops of birds subjected to fasting plus chlorine, was less, in comparison to the results, 12 hours before slaughter (without fasting), such difference did not reach a statistical significance (P>0.05) because of the variability of the data. Nonetheless, when preparing the results obtained from the birds subjected to fasting, without chlorine in the drinking water, with those of the birds subjected to fasting, plus chlorine in the water. We see a significant reduction (P<0.05) in the MPN of enterococci in the crop, because such variation in the individual results was less, since all birds were subjected to fasting, at the same time, and independently from the amount of litter ingested, the crop´s contamination was the same, different to the birds without fasting, the option of ingesting, both, feed as well as litter.

Chlorine was truly efficient in the reduction of microorganisms in the crops of broilers. It is necessary to associate fasting to disinfection of this organs using chlorine in the drinking water, since treatment, just and only by means of fasting, seems to increase the most probable number of enterococci in the ingluvio, representing a higher risk of contamination of the carcass during processing at the slaughter house, consequently representing a higher risk to public health.

APHA - American Public Health Association. 2001. Committee on Microbiological Methods for Foods; Compendium of methods for the microbiological examination of foods. 4^a. ed. Washington: American Public Health Association. 676 p.

Barnhart ET, Sarlin LL, Caldwell DJ, Byrd JA, Corrier DE, Hargis DM. 1999. Evaluation of potential disinfectants for preslaughter broiler crop decontamination. Poult Sci. 78(1):32-37.

Duke GE, Bash M, Noll S. 1997. Optimum duration of feed and water removal prior to processing in order to reduce the potential for fecal contamination in turkeys. Poult Sci. 76:516-522.

Gavin A & Weddig LM. 1995. Canned Foods: Principles of Thermal Process Control, Acidification, and Container Evaluation. Washington: Food Processors Institute.

Lillard HS. 1980. Effect on broiler carcasses and water of treating chiller water with chlorine or chlorine dioxide. Poult Sci. 59(8):1761-1766.

Lyon CE, Papa CM, Winlson Junior RL. 1991. Effect of feed withdrawal on yields, muscle pH, and texture of broiler breast meat. Poult Sci. 70(4): 1020-1025.

Mendes AA. 2001. Jejum pré-abate em frangos de corte. Rev. Bras. Cienc. Avic. 3:199-209.

Northcutt JK, Savage SI, Vest LR. 1997. Relationship between feed withdrawal and viscera condition of broilers. Poult Sci. 76:410-414.

Smidt MJ, Formica SD, Fritz JC. 1964. Effect of fasting prior to slaughter on yield of broilers. Poult Sci. 43:931-934.

Tsai LS, Schade JE, Molyneux BT. 1992. Chlorination of poultry chiller water: chlorine demand and disinfection efficiency. Poult Sci. 71(1):188-196.

Veerkamp CH. 1986. Fasting and yields of broilers. Poult Sci. 65(7):1299-1304.

Wabeck CJ. 1972. Feed and water withdrawal time relationship to processing yield and potential fecal contamination of broilers. Poult Sci. 51:1119-1121.

To the Amparo Foundation for the State Research of the State of São Paulo (FAPESP) because of the granting of the Master´s schoolarship, as well as for the help provided for this research.