Effects of Dietary Lactose on Incidence and Levels of Salmonellae on Carcasses of Broiler Chickens Grown to Market Age 1 2 AMY L. WALDROUP, WAKAKO YAMAGUCHI, JAMES T. SKINNER, and PARK W. WALDROUP Animal and Poultry Sciences Department, University of Arkansas, Fayetteville, Arkansas 72701
ABSTRACT Two trials were conducted to evaluate the effects of lactose in the diet of broilers grown to market weights on incidence and levels of salmonellae on the carcass. Lactose was substituted for sand in otherwise nutritionally complete diets at levels of 0,2.5,5, and 7.5% and fed from day-old to 49 days of age. Birds were reared on used (Trial 1) or new (Trial 2) litter and inoculated via the drinking water on Days 2, 7, and 14 with 108 cfu/mL Salmonella typhimurium (ATCC 14028). At 50 days, 12 (Trial 1) or 24 (Trial 2) birds per treatment were processed and prechill carcasses were evaluated for salmonellae incidence and level by the most probable number (MPN) method. Body weight of male broilers was significantly reduced by feeding diets containing up to 7.5% lactose. Feed intake of broilers fed diets containing lactose was significantly reduced and feed utilization improved, suggesting that lactose provided some metabolizable energy. The degree of litter caking was significantly increased, and cecal pH was significantly decreased as dietary lactose increased. Prechill carcasses of broilers fed diets with 7.5% lactose had significantly higher levels of salmonellae than did prechill carcasses of broilers fed 0% lactose. The results of the present study suggest that supplementing poultry diets with lactose is not a viable means in itself of reducing or eliminating salmonellae incidence or levels on processed broiler carcasses. (Key words: Salmonella, lactose, carcasses, processing, food safety) 1992 Poultry Science 71288-295
tissues are carbohydrate in nature, and treatment with an appropriate carbohyNumerous studies have been conducted drate may prevent effective attachment by in efforts to decrease salmonellae contami- obstructing adhesion or the attachment nation of broiler carcasses during produc- site (Bitton and Marshall, 1980; Ofek and tion and processing. One approach is Beachey, 1980; Abraham et ah, 1983). preventing attachment of salmonellae in Recent in vitro studies suggest that adherthe intestine and cecae or on the surface of ence of Salmonella typhimurium to the the carcass by various physical or chemical means. Most bacterial attachment intestine of day-old chicks and to the cecae mechanisms and receptor sites on animal of 7- to 10-day-old broilers is inhibited by d-mannose (McHan et ah, 1989; Oyofo et ah, 1989a,b,c) or lactose (Corrier et ah, 1990a,b; Hinton et ah, 1990; Ziprin et ah, •'Published with the approval of the director, Ar- 1990). kansas Agricultural Experiment Station. Salmonellae colonization of the chick is Supported through a USDA Cooperative State Research Service Special Research Grants Program most likely to occur during the first few weeks of life (Smith and Tucker, 1980; (8902384). INTRODUCTION
288
Downloaded from http://ps.oxfordjournals.org/ at UIC Library, Collections Development on May 7, 2015
(Received for publication August 13, 1991)
LACTOSE AND SALMONELLA CONTAMINATION
289
Downloaded from http://ps.oxfordjournals.org/ at UIC Library, Collections Development on May 7, 2015
was assumed that lactose 4 provided no energy to the diet (Atkinson et al., 1957; Moran, 1985) and was nutritionally inert; therefore the energy content of the diet was reduced slightly below that normally observed in commercial United States broiler diets so as not to require excessive levels of supplemental fats. The ratio of energy to essential nutrients suggested by Thomas et al. (1986) was maintained. Complete vitamin and trace mineral mixtures that met the requirements suggested by the National Research Council (1984) were used to supplement all diets. Diets were formulated for starter (0 to 21 days), grower (21 to 42 days), and finisher (42 to 49 day) periods. Salinomycin 5 (66 m g / k g ) MATERIALS AND METHODS was added to starter and grower diets as an anticoccidial. Composition of the diets In two consecutive trials, sexed day-old is shown in Table 1. chicks of a commercial broiler strain 3 were A large batch of each feed was mixed obtained from a local hatchery and 60 chicks (30 males and 30 females) were for each feeding period and aliquots used randomly allocated into each of 16 pens for mixing test diets. Lactose was included (5.2 m 2 ) in an insulated broiler house with in test diets at 0, 2.5, 5.0, or 7.5%; washed concrete floors. In the first trial the pens builder's sand was used as an inert filler contained previously used oak shavings as needed. Diets were fed in meal form. Each diet was assigned to four replicate with a top dressing of new oak shavings; pens of chickens in each trial in a randomin the second trial the pens contained an ized block design; diets and tap water equal mixture of new rice hulls and new were given for ad libitum consumption. pine shavings. Each pen was equipped Samples of diets were subjected to Kjelwith two hanging feeders and an auto- dahl assay for crude protein (Association matic waterer; during the first 7 days of Official Agricultural Chemists, 1970) to supplemental feeders and waterers were verify proper mixing; all diets were found used. Whole-house brooding was used to be within expected values for crude with minimum temperatures set at 30 C protein. for the 1st wk, with a reduction of 2.8 C / On Days 2, 7, and 14, birds were wk to a minimum of 19.2 C. ThermostatiSalmonella typhimurium cally controlled gas stoves, ventilation inoculated with 6 (ATCC 14028) via the drinking fountains fans, and sidewall curtains were used to as described by Izat et al. (1990a,b,c). This maintain proper temperature and ventilaprocedure, utilizing this organism, has tion rates. Incandescent lights were used been shown to result in a high percentage 23 h daily (0100 to 2400 h). of colonized birds (Izat et al, 1990a,c). Diets were formulated to meet a miniAt 21, 42, and 49 days of age, the mum of 105% of the amino acid needs chickens in each pen were group-weighed suggested for the broiler male by Thomas by sex and pen feed consumption was et al. (1986). For formulation purposes it determined. Feed utilization was calculated as feed consumed divided by body weight. Deaths were noted as they oc3 Cobb 500, Cobb-Vantress, Inc., Siloam Springs, curred; all birds that died were weighed and the weight of dead birds used in AR 72761. 4 Lactose provided by Milk Specialties Co., Dun- determining feed utilization. dee, IL 60118. Samples of birds were taken at 21 (Trial ^io-Cox, Agri-Bio Corp., Gainesville, GA 30503. American Type Culture Collection, Rockville, 2) and 49 (both trials) days of age for determination of cecal weight and p H of MD 20852. DeLoach, 1989; Ziprin et al, 1989). Intervention during this time may reduce salmonellae contamination of processed broiler carcasses at market age. However, chickens are continually exposed to salmonellae from many sources throughout their growing period and interference with intestinal colonization per se may not necessarily reduce the incidence of salmonellae contamination of the carcass. Therefore, the objective of the present study was to evaluate the effects of feeding lactose to broilers from day-old to market weight on performance and salmonellae incidence and levels of processed broiler carcasses.
290
WALDROUP ET AL. TABLE 1. Composition and calculated nutrient content of experimental diets
Ingredients and calculated nutrient content
Grower (21 to 42 days)
Finisher (42 to 49 days)
50.62 30.12 6.69 2.33 1.45 .40 .09 .20 .50 .10 7.50 100.00
51.16 29.23 7.45 2.14 1.35 .40 .00 .17 .50 .10 7.50 100.00
59.77 21.36 7.00 1.99 1.27 .40 .00 .11 .50 .10 750 100.00
2,975 19.57 1.12 56 1.32 1.15 .52 .85 .75
3,030 19.09 1.04 .52 1.29 1.05 .48 .81 .74
3,085 16.11 .97 .48 1.05 .83 .39 .68 .62
Provides per kilogram of diet: vitamin A, 9,900 IU; cholecalciferol, 3,300 ICU; vitamin E, 13 IU; menadione, 1.1 mg; riboflavin, 6.6 mg; niacin, 66 mg; pantothenic acid, 16.5 mg; choline, 660 mg; thiamin, 1.1 mg; pyridoxine, 3.3 mg; vitamin Bj2, -013 mg; biotin, .11 mg; folic acid, 1.1 mg; ethoxyquin, 125 mg; selenium, .2mg. 2 Provides per kilogram of diet: Fe, 100 mg; Mn, 100 mg; Zn, 100 mg; Cu, 10 mg; I, 1 mg. 3 Consists of variable amounts of lactose or washed builder's sand.
cecal contents. At each age period, three females from each pen were randomly selected with the proviso that they were within one half standard deviation of the sexed mean weight. The birds were killed by cervical dislocation, and the cecae were removed and weighed. The contents of the cecae were removed, placed in an equal part by weight of distilled water, shaken with glass beads, and the p H determined. At 50 days of age the birds were removed from the pens and a subjective Utter score was assigned to each pen; the scores were based upon percentage of the surface area of the pen that was caked over. Three (Trial 1) or six (Trial 2) males from each replicate pen (12 or 24 per
'Cervin Automated Systems, Inc., Minneapolis, MN 55410. Pickwick Co., Cedar Rapids, 1A 52402.
treatment for Trials 1 and 2, respectively) that were within one-half standard deviation of the sexed mean weight were processed in a pilot processing plant. Eight hours prior to processing, feed (but not water) was withdrawn. Birds were placed in clean coops and transported 4 k m to the processing plant where they were processed within 1 h. Birds were stunned by an electric knife/ killed by severing the jugular vein, allowed to bleed for 90 s, scalded for 2 min in clean hot water at 60 C, and picked in a rotary d r u m picker. 8 The carcasses were manually eviscerated, taking care not to contaminate the carcass with intestinal material. All birds within a single treatment were processed as a group, with the treatments processed in random order, determined by lot. The processing equipment and the evisceration area were cleaned and disinfected between treatments, and fresh scald water was used for each treatment group.
Downloaded from http://ps.oxfordjournals.org/ at UIC Library, Collections Development on May 7, 2015
Ground yellow corn Dehulled soybean meal Animal-vegetable fat Dicalcium phosphate Ground limestone Iodized salt Lysine HC1 DL-methionine Vitamin premix 1 Trace mineral mix 2 Variable3 Total Calculated nutrient content ME, kcal/kg Crude protein, % Calcium, % Nonphytate phosphorus, % Arginine, % Lysine, % Methionine, % TSAA, % Threonine, %
Starter (0 to 21 days)
LACTOSE AND SALMONELLA CONTAMINATION
9
Difco Laboratories, Detroit, MI 48201.
were used as the error mean square. There were no interactions of trial by lactose for microbiological data, so data from the two trials were combined for presentation. Where applicable, treatment means were separated using the Least Squares Means option of base SAS® software, which uses repeated t tests. Statements of statistical significance in all instances is based upon P
ABSTRACT Two trials were conducted to evaluate the effects of lactose in the diet of broilers grown to market weights on incidence and levels of salmonellae on the carcass. Lactose was substituted for sand in otherwise nutritionally complete diets at levels of 0,2.5,5, and 7.5% and fed from day-old to 49 days of age. Birds were reared on used (Trial 1) or new (Trial 2) litter and inoculated via the drinking water on Days 2, 7, and 14 with 108 cfu/mL Salmonella typhimurium (ATCC 14028). At 50 days, 12 (Trial 1) or 24 (Trial 2) birds per treatment were processed and prechill carcasses were evaluated for salmonellae incidence and level by the most probable number (MPN) method. Body weight of male broilers was significantly reduced by feeding diets containing up to 7.5% lactose. Feed intake of broilers fed diets containing lactose was significantly reduced and feed utilization improved, suggesting that lactose provided some metabolizable energy. The degree of litter caking was significantly increased, and cecal pH was significantly decreased as dietary lactose increased. Prechill carcasses of broilers fed diets with 7.5% lactose had significantly higher levels of salmonellae than did prechill carcasses of broilers fed 0% lactose. The results of the present study suggest that supplementing poultry diets with lactose is not a viable means in itself of reducing or eliminating salmonellae incidence or levels on processed broiler carcasses. (Key words: Salmonella, lactose, carcasses, processing, food safety) 1992 Poultry Science 71288-295
tissues are carbohydrate in nature, and treatment with an appropriate carbohyNumerous studies have been conducted drate may prevent effective attachment by in efforts to decrease salmonellae contami- obstructing adhesion or the attachment nation of broiler carcasses during produc- site (Bitton and Marshall, 1980; Ofek and tion and processing. One approach is Beachey, 1980; Abraham et ah, 1983). preventing attachment of salmonellae in Recent in vitro studies suggest that adherthe intestine and cecae or on the surface of ence of Salmonella typhimurium to the the carcass by various physical or chemical means. Most bacterial attachment intestine of day-old chicks and to the cecae mechanisms and receptor sites on animal of 7- to 10-day-old broilers is inhibited by d-mannose (McHan et ah, 1989; Oyofo et ah, 1989a,b,c) or lactose (Corrier et ah, 1990a,b; Hinton et ah, 1990; Ziprin et ah, •'Published with the approval of the director, Ar- 1990). kansas Agricultural Experiment Station. Salmonellae colonization of the chick is Supported through a USDA Cooperative State Research Service Special Research Grants Program most likely to occur during the first few weeks of life (Smith and Tucker, 1980; (8902384). INTRODUCTION
288
Downloaded from http://ps.oxfordjournals.org/ at UIC Library, Collections Development on May 7, 2015
(Received for publication August 13, 1991)
LACTOSE AND SALMONELLA CONTAMINATION
289
Downloaded from http://ps.oxfordjournals.org/ at UIC Library, Collections Development on May 7, 2015
was assumed that lactose 4 provided no energy to the diet (Atkinson et al., 1957; Moran, 1985) and was nutritionally inert; therefore the energy content of the diet was reduced slightly below that normally observed in commercial United States broiler diets so as not to require excessive levels of supplemental fats. The ratio of energy to essential nutrients suggested by Thomas et al. (1986) was maintained. Complete vitamin and trace mineral mixtures that met the requirements suggested by the National Research Council (1984) were used to supplement all diets. Diets were formulated for starter (0 to 21 days), grower (21 to 42 days), and finisher (42 to 49 day) periods. Salinomycin 5 (66 m g / k g ) MATERIALS AND METHODS was added to starter and grower diets as an anticoccidial. Composition of the diets In two consecutive trials, sexed day-old is shown in Table 1. chicks of a commercial broiler strain 3 were A large batch of each feed was mixed obtained from a local hatchery and 60 chicks (30 males and 30 females) were for each feeding period and aliquots used randomly allocated into each of 16 pens for mixing test diets. Lactose was included (5.2 m 2 ) in an insulated broiler house with in test diets at 0, 2.5, 5.0, or 7.5%; washed concrete floors. In the first trial the pens builder's sand was used as an inert filler contained previously used oak shavings as needed. Diets were fed in meal form. Each diet was assigned to four replicate with a top dressing of new oak shavings; pens of chickens in each trial in a randomin the second trial the pens contained an ized block design; diets and tap water equal mixture of new rice hulls and new were given for ad libitum consumption. pine shavings. Each pen was equipped Samples of diets were subjected to Kjelwith two hanging feeders and an auto- dahl assay for crude protein (Association matic waterer; during the first 7 days of Official Agricultural Chemists, 1970) to supplemental feeders and waterers were verify proper mixing; all diets were found used. Whole-house brooding was used to be within expected values for crude with minimum temperatures set at 30 C protein. for the 1st wk, with a reduction of 2.8 C / On Days 2, 7, and 14, birds were wk to a minimum of 19.2 C. ThermostatiSalmonella typhimurium cally controlled gas stoves, ventilation inoculated with 6 (ATCC 14028) via the drinking fountains fans, and sidewall curtains were used to as described by Izat et al. (1990a,b,c). This maintain proper temperature and ventilaprocedure, utilizing this organism, has tion rates. Incandescent lights were used been shown to result in a high percentage 23 h daily (0100 to 2400 h). of colonized birds (Izat et al, 1990a,c). Diets were formulated to meet a miniAt 21, 42, and 49 days of age, the mum of 105% of the amino acid needs chickens in each pen were group-weighed suggested for the broiler male by Thomas by sex and pen feed consumption was et al. (1986). For formulation purposes it determined. Feed utilization was calculated as feed consumed divided by body weight. Deaths were noted as they oc3 Cobb 500, Cobb-Vantress, Inc., Siloam Springs, curred; all birds that died were weighed and the weight of dead birds used in AR 72761. 4 Lactose provided by Milk Specialties Co., Dun- determining feed utilization. dee, IL 60118. Samples of birds were taken at 21 (Trial ^io-Cox, Agri-Bio Corp., Gainesville, GA 30503. American Type Culture Collection, Rockville, 2) and 49 (both trials) days of age for determination of cecal weight and p H of MD 20852. DeLoach, 1989; Ziprin et al, 1989). Intervention during this time may reduce salmonellae contamination of processed broiler carcasses at market age. However, chickens are continually exposed to salmonellae from many sources throughout their growing period and interference with intestinal colonization per se may not necessarily reduce the incidence of salmonellae contamination of the carcass. Therefore, the objective of the present study was to evaluate the effects of feeding lactose to broilers from day-old to market weight on performance and salmonellae incidence and levels of processed broiler carcasses.
290
WALDROUP ET AL. TABLE 1. Composition and calculated nutrient content of experimental diets
Ingredients and calculated nutrient content
Grower (21 to 42 days)
Finisher (42 to 49 days)
50.62 30.12 6.69 2.33 1.45 .40 .09 .20 .50 .10 7.50 100.00
51.16 29.23 7.45 2.14 1.35 .40 .00 .17 .50 .10 7.50 100.00
59.77 21.36 7.00 1.99 1.27 .40 .00 .11 .50 .10 750 100.00
2,975 19.57 1.12 56 1.32 1.15 .52 .85 .75
3,030 19.09 1.04 .52 1.29 1.05 .48 .81 .74
3,085 16.11 .97 .48 1.05 .83 .39 .68 .62
Provides per kilogram of diet: vitamin A, 9,900 IU; cholecalciferol, 3,300 ICU; vitamin E, 13 IU; menadione, 1.1 mg; riboflavin, 6.6 mg; niacin, 66 mg; pantothenic acid, 16.5 mg; choline, 660 mg; thiamin, 1.1 mg; pyridoxine, 3.3 mg; vitamin Bj2, -013 mg; biotin, .11 mg; folic acid, 1.1 mg; ethoxyquin, 125 mg; selenium, .2mg. 2 Provides per kilogram of diet: Fe, 100 mg; Mn, 100 mg; Zn, 100 mg; Cu, 10 mg; I, 1 mg. 3 Consists of variable amounts of lactose or washed builder's sand.
cecal contents. At each age period, three females from each pen were randomly selected with the proviso that they were within one half standard deviation of the sexed mean weight. The birds were killed by cervical dislocation, and the cecae were removed and weighed. The contents of the cecae were removed, placed in an equal part by weight of distilled water, shaken with glass beads, and the p H determined. At 50 days of age the birds were removed from the pens and a subjective Utter score was assigned to each pen; the scores were based upon percentage of the surface area of the pen that was caked over. Three (Trial 1) or six (Trial 2) males from each replicate pen (12 or 24 per
'Cervin Automated Systems, Inc., Minneapolis, MN 55410. Pickwick Co., Cedar Rapids, 1A 52402.
treatment for Trials 1 and 2, respectively) that were within one-half standard deviation of the sexed mean weight were processed in a pilot processing plant. Eight hours prior to processing, feed (but not water) was withdrawn. Birds were placed in clean coops and transported 4 k m to the processing plant where they were processed within 1 h. Birds were stunned by an electric knife/ killed by severing the jugular vein, allowed to bleed for 90 s, scalded for 2 min in clean hot water at 60 C, and picked in a rotary d r u m picker. 8 The carcasses were manually eviscerated, taking care not to contaminate the carcass with intestinal material. All birds within a single treatment were processed as a group, with the treatments processed in random order, determined by lot. The processing equipment and the evisceration area were cleaned and disinfected between treatments, and fresh scald water was used for each treatment group.
Downloaded from http://ps.oxfordjournals.org/ at UIC Library, Collections Development on May 7, 2015
Ground yellow corn Dehulled soybean meal Animal-vegetable fat Dicalcium phosphate Ground limestone Iodized salt Lysine HC1 DL-methionine Vitamin premix 1 Trace mineral mix 2 Variable3 Total Calculated nutrient content ME, kcal/kg Crude protein, % Calcium, % Nonphytate phosphorus, % Arginine, % Lysine, % Methionine, % TSAA, % Threonine, %
Starter (0 to 21 days)
LACTOSE AND SALMONELLA CONTAMINATION
9
Difco Laboratories, Detroit, MI 48201.
were used as the error mean square. There were no interactions of trial by lactose for microbiological data, so data from the two trials were combined for presentation. Where applicable, treatment means were separated using the Least Squares Means option of base SAS® software, which uses repeated t tests. Statements of statistical significance in all instances is based upon P
