Examination of potential interactions between methods of coccidiosis control and nutrition in broilers

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1 Examination of potential interactions between methods of coccidiosis control and nutrition in broilers J.S. RENNIE 1 and R.A.H.M. TEN DOESCHATE 2 1 Schering Plough Animal Health, Harefield, Uxbridge, UB9 6LS, UK. 2 Abnatech Global, ABN House, PO Box 250, Oundle Road, Peterborough, PE2 9QF, UK. Corresponding author sarah.rennie@spcorp.com Interactions between two methods of coccidiosis control and nutrition were tested in a 64 pen 2x2x2x2 factorial trial with 25 male and 25 female Ross 308 broilers per pen. Basal diets were formulated to current UK nutritional standards. Trial diets were supplemented with up to 10% whole wheat. Coccidiosis was controlled either by vaccinating day-old chicks with Paracox 5 TM or by including coccidiostats (ACS): nicarbazin (50 mg/kg) and narasin (50 mg/kg) in the starter diet (1-12 days), followed by monensin (100 mg/kg) in the grower (13-27 days) and finisher (28-35 days) diets. The first nutritional factor tested whether addition of extra methionine, threonine and betaine (nutrients thought to benefit gut health) to starter, grower and finisher diets would improve performance. Secondly, we tested whether avoiding a feed change during maximal vaccinal oocyst multiplication in the gut (around day 20) would improve performance. Birds were either fed grower 1 from days followed by grower 2 (with a reduced nutrient level) from days or fed grower 2 from days. The third factor was based on the hypothesis that, during the withdrawal period (36-43 days) vaccinated birds may have better gut health due to development of immunity than birds previously fed ACS, allowing the use of a reduced specification withdrawal (RW) diet (-5% digestible amino acids) without reducing bird performance. Statistical analysis (Genstat 8.1) of liveweight (LW) and feed conversion (FCR) data showed no interactions between method of coccidiosis control and nutritional factors at 42 days nor were there any significant (P>0.05) differences in LW and FCR between Paracox 5 TM vaccinated birds and ACS fed birds. The results suggest that there was no performance benefit (LW and FCR) of enhancing nutrition over the basal specification starter, grower and finisher diets or from cutting the number of grower diets from 2 to 1 for Paracox 5 TM vaccinated birds. Use of RW did not affect LW or FCR indicating that reduction of withdrawal diet cost is possible. In conclusion, vaccinating broilers fed good quality basal rations with Paracox 5 TM is not associated with a drop in performance and thus dietary enhancement will not increase performance. Further work is needed in order to examine to what extent advantage can be taken of the immune status of birds during the withdrawal period. Keywords: coccidiosis; Paracox 5; broiler; nutrition Introduction Coccidiosis is one of the most commonly reported diseases of chickens and the consequences of infection range from poor performance to mortality depending on the level of infection and the species of Eimeria. Coccidiosis in broiler chickens may be controlled by using anti-coccidial medication incorporated into the birds feed or by using a vaccine such as Paracox 5 TM. Paracox 5 TM is a live attenuated oral vaccine for the active immunisation of broiler chickens to reduce infection and clinical signs of coccidiosis caused by Eimeria acervulina, E. maxima, E. mitis and E. tenella. Broilers vaccinated with Paracox 5 TM at day-old develop immunity to coccidial infection, which is boosted by exposure to field strains of Eimeria through the life of the birds. A common UK in feed coccidiostat programme consists of a chemical coccidiostat during the first part of the bird s life followed by an ionophore during the latter part. The rationale behind such shuttle programmes is to minimize exposure to coccidial oocysts during the early phase whilst allowing a trickle infection during the later stages which helps immunity to develop in a controlled fashion. However, the use of thinning programmes may result in rather long withdrawal periods before birds are slaughtered, leading to the possibility of a late coccidial challenge and a drop in performance, particularly if there is resistance to the anti-coccidial medications being used.

2 The nutritional requirements of Paracox 5 TM vaccinated broilers may be different from those of broilers receiving in feed anti-coccidial medication at several stages during the life of the bird. Firstly, during the period of development of immunity in the gut over the first 3 weeks of life, the requirements for certain nutrients may be relatively greater. Secondly, during the period of maximal vaccine replication in the gut, any changes in feed composition might be detrimental to gut health and function. Thirdly, during the later stages of growth requirement of certain nutrients may be less due to the fully immune status of the bird which lasts until slaughter. This hypothesis has been given the acronym IDEA and aspects of it have been tested in Southern European countries using maize-based diets formulated to local nutritional standards. Results of trials have suggested that nutrient quality, particularly essential amino acid content, is important for maximal zootechnical response in Paracox 5 TM vaccinated birds (Carnicier Garcia and Bolis, 2005). Minimising, and preferably eliminating, feed changes during the period of vaccinal replication may also enhance bird performance. Broiler growing in UK and Northern Europe presents a particular set of challenges, including very high welfare requirements, the weather conditions which make maintaining good litter condition challenging, and diets based on wheat, which can be associated with dysbacteriosis or necrotic enteritis, and which necessitate the use of dietary enzymes to reduce the viscosity of gut contents. A 2x2x2x2 factorial experiment was designed using pens of broiler chickens to test the interactions between two methods of coccidiosis control and nutrition. The basal diets were formulated to replicate typical UK nutritional standards for broilers. Materials and Methods Diets, based on wheat, hipro soya, Extrupro (extruded mixture of oilseed rape and beans) and fishmeal, were formulated by Abnatech Global, and manufactured in a specialist mill. Equipment was swept and flushed between batches of coccidiostat-containing and coccidiostat-free diets. The composition of a sample of each diet was confirmed by proximate analysis. Diets were fed as crumb (starter diets) or pellets (grower, finisher and withdrawal diets). The trial was carried out in a house containing 64 pens measuring 2.15 x 1.54 metres. Each pen was equipped with a tube feeder and a bell drinker and 25 male and 25 female Ross 308 broilers were placed. The house was heated by thermostatically-controlled space heaters. The birds were either vaccinated at day old with Paracox 5 TM or fed feed containing coccidiostats (ACS). Paracox 5 TM was administered at day old by first of all diluting it with tap water, and then spraying on the feed at a rate of one dose per chick, shortly before the chicks were placed, using a hand held sprayer. For the treatment groups receiving coccidiostats, the starter diets contained Maxiban (supplying 50 mg/kg nicarbazin and 50 mg/kg narasin) and the grower and finisher diets contained Elancoban (supplying 100 mg/kg monensin). The first nutritional factor to be investigated was nutrient balance in starter, grower and finisher diets. The specifications of the basal (B) and enhanced (E) nutrient balance diets are shown in the table below. Table 1 Nutrient specification of starter, grower and finisher diets. Starter Grower 1 Grower 2 Finisher B E B E B E B E AMEn (MJ/kg) Digestible Lysine (g/kg) Digestible Methionine & Cysteine (g/kg) Digestible Threonine (g/kg) Betaine (mg/kg) Whole wheat mixed with above diet (g/kg)

3 The second nutritional factor to be investigated was feed change during the grower period. Either both Grower 1 and Grower 2 diets were fed to birds consecutively, or only Grower 2 over the entire period. The third nutritional factor to be tested was a reduction in the content of balanced amino acids during the withdrawal period. The specifications of the basal (B) and reduced (R) nutrient diets are shown in the table below. Table 2 Nutrient specification of withdrawal diets Withdrawal B R AMEn (MJ/kg) Digestible Lysine (g/kg) Digestible Methionine & Cysteine (g/kg) Digestible Threonine (g/kg) Betaine (mg/kg) 0 0 Whole wheat mixed with above diet (g/kg) The starter diets were fed from days 0-12, grower 1 diets from days 13-20, grower 2 diets from days 21-27, finisher diets from days and withdrawal diets from days Diets were supplemented with whole wheat at increasing ratios through the trial as shown in Tables 1 and 2. Birds were weighed at the start of the trial and at the end of each feeding period with weights of dead birds and culls also being recorded. All feed added to the tube feeders and remaining in feeders at the end of each feeding period was weighed. Feed Conversion Ratio (FCR) was calculated using bird weight (live and dead) and feed intake data. Water intake was calculated by recording the volume of water consumed from each drinker in two out of every four pens during each feeding period. Litter moisture content was determined in composite samples from each pen at 21 and 42 days by drying in an oven for 12 hours at 80 ºC. At 21 and 28 days of age, two birds from each pen were killed by cervical dislocation and examined for lesions of coccidiosis (Johnson and Reid, 1970) and signs of dysbacteriosis. Data were analysed using Genstat 8.1. Liveweight (LW), FCR and water intake data were analysed by analysis of variance (ANOVA). Dysbacteriosis data were analysed by fitting a generalized linear model (GLM) with binomial errors. Results and Discussion During the grower 1 (13-20 days) feeding period a significant (P<0.001) increase in water consumption was associated with Paracox 5 TM vaccination. The average water consumption was l/survivor for birds previously vaccinated with Paracox 5 TM compared with l/survivor for birds receiving feed containing ACS. This increase in water consumption was not maintained during the grower 2, finisher and withdrawal periods (data not shown). Paracox 5 TM is a live attenuated vaccine and the development of active immunity is associated with replication of vaccinal oocysts in the bird s gut. Vaccinal oocyst replication typically results in some birds developing mild gut lesions scoring 1 or 2 (Williams and Andrews, 2001) Such lesions were seen in this trial at 21 and 28 days of age (data not shown) and the mild gut damage induced by vaccine replication may be the cause of the increased water intake during this period. The increased water consumption was not, however, associated with a significant difference in litter moisture content. At 21 days the average litter moisture content was 51.2% for birds previously vaccinated with Paracox 5 TM, compared with 49.0% for birds fed ACS. At 42 days, the figures were 54.5% and 53.6% respectively. This supports the view that factors other than water consumption have a part to play in achieving low litter moisture content and maintenance of dry, friable litter.

4 Dysbacteriosis may be considered to be a mild form of enteritis, with the intestine showing signs of thinning, ballooning or inflammation. Gut contents may be watery and caecal contents may be gassy or very liquid. There was a trend towards a higher incidence of dysbacteriosis in birds vaccinated with Paracox 5 TM compared with birds receiving feeds containing ACS, which differences were not statistically significant (P>0.05) at 21 days of age, but were (P<0.05) at 28 days of age. One explanation for this trend could be that Paracox 5 TM vaccination per se is a predisposing factor to dysbacteriosis as the mild gut damage caused by vaccination could be allowing the establishment of bacteria capable of causing enteritis. This mechanism has been suggested as a factor in the association between coccidial infection caused by field strains and the development of necrotic enteritis involving clostridial infection (Williams, 2005). Another possible explanation could be that the combination of wheat-based diets, whole wheat feeding and environmental and management conditions on farm increased the likelihood of birds developing dysbacteriosis, and that this condition was suppressed in the birds receiving ionophore coccidiostats, which are known to have antibiotic properties as well as anticoccidial activity. At the end of the Grower 2 feeding period, birds previously vaccinated with Paracox 5 TM were significantly lighter than birds receiving feed containing ACS (Table 3). This difference was not maintained at the end of finisher and withdrawal periods (vaccinated birds were numerically heavier at 42 days), indicating compensatory growth. Birds receiving two grower feeds were significantly heavier than birds receiving one feed through the grower period. There was a significant interaction between enhanced nutrient balance, grower feed change and method of coccidiosis control in that making a grower feed change had no effect on LW of ACS fed birds on the basal nutrient balance but increased LW for the other treatment combinations. Birds on the enhanced nutrient balance showed an increased LW as a result of the grower feed change whereas birds on the basal nutrient balance did not. Table 3a Mean liveweights (g) Cocci Control Nutrient Balance Grower Feed Change Reduced Withdrawal Starter Grower 2 Finisher Withdrawal 1 P5 B Yes No P5 B Yes Yes P5 B No No P5 B No Yes P5 E Yes No P5 E Yes Yes P5 E No No P5 E No Yes ACS B Yes No ACS B Yes Yes ACS B No No ACS B No Yes ACS E Yes No ACS E Yes Yes ACS E No No ACS E No Yes SED

5 Table 3b F test probabilities for significance of treatment effects on mean liveweights Starter Grower 2 Finisher Withdrawal Nutrient Balance (1) Grower Feed Change (2) Coccidiosis Control (3) < Reduced Cost Withdrawal (4) (1) x (2) (1) x (3) (2) x (3) (1) x (4) (2) x (4) (3) x (4) (1) x (2) x (3) (1) x (2) x (4) (1) x (3) x (4) (2) x (3) x (4) (1) x (2) x (3) x (4) At the end of the second grower period, birds previously vaccinated with Paracox 5 TM had a significantly poorer FCR than birds receiving feed containing ACS (Table 4). This difference was not maintained through the finisher and withdrawal periods, resulting in nearly equal values (1.814 for vaccinated and for ACS fed birds) at 42 days. There was a significant interaction between nutrient balance, grower feed change and method of coccidiosis control, in that the FCR of ACS fed birds receiving the basal nutrient balance feeds combined with a grower feed change was higher whereas for all other treatment combinations feeding two grower feeds resulted in a lower FCR. Birds fed an enhanced nutrient balance showed a lower FCR when two grower feeds were used whereas on the basal nutrient balance there was no benefit of using two grower feeds. There were no significant treatment effects at the end of finisher or withdrawal periods. Table 4a Mean feed conversion ratios Cocci Control Nutrient Balance Grower Feed Change Reduced Withdrawal Starter Grower 2 Finisher Withdrawal 1 P5 B Yes No P5 B Yes Yes P5 B No No P5 B No Yes P5 E Yes No P5 E Yes Yes P5 E No No P5 E No Yes ACS B Yes No ACS B Yes Yes ACS B No No ACS B No Yes ACS E Yes No ACS E Yes Yes ACS E No No ACS E No Yes SED

6 Table 4b F test probabilities for significance of treatment effects on mean feed conversion ratios Starter Grower 2 Finisher Withdrawal Nutrient Balance (1) Grower Feed Change (2) Coccidiosis Control (3) < Reduced Cost Withdrawal (4) (1) x (2) (1) x (3) (2) x (3) (1) x (4) (2) x (4) (3) x (4) (1) x (2) x (3) (1) x (2) x (4) (1) x (3) x (4) (2) x (3) x (4) (1) x (2) x (3) x (4) It is concluded that, using the experimental combination of relatively high specification basal diets and wheat feeding described, there was no benefit to the Paracox 5 TM vaccinated birds in final liveweight and final FCR in enhancing the nutrient content of the starter, grower and finisher rations, or from eliminating feed change during the period of maximal vaccine replication. Reducing the specification of the withdrawal ration likewise had no impact on final liveweight or final FCR in Paracox 5 TM vaccinated birds, but also had no impact on the final liveweight or final FCR or birds fed diets containing ACS. It is possible that the specification of the basal withdrawal diets used in the trial was sufficiently high for the reduction (approximately 5% reduction in digestible amino acids) to have no impact. Further work focussing on the withdrawal period, and using a greater range of diets, is necessary to test the theory that fully immune birds have a nutritional advantage at this stage of the growing cycle over birds fed ACS. Commercially, this is important because broilers may be exposed to coccidia during the later stages of production, when, because of concerns about residues in meat for human consumption, withdrawal feeds containing no ACS must be fed and if thinning is carried out, withdrawal periods may extend for up to two to three weeks of the broiler s life. Acknowledgments We thank Jim Craigon of Nottingham University School of Biosciences for expert statistical analysis. References CARNICIER GARCIA, C. AND BOLIS, D. (2005) Nutrition is key building block of successful drugfree broiler production. World Poultry, 21(12): Supplement. JOHNSON, J. AND REID, W.M. (1970) Anticoccidial drugs: lesion scoring techniques in battery and floor-pen experiments with chickens. Experimental Parasitology, 28: WILLIAMS, R.B. (2005) Intercurrent coccidiosis and necrotic enteritis of chickens: rational, integrated disease management by maintenance of gut integrity. Avian Pathology 34(3): WILLIAMS, R.B. AND ANDREWS, S.J. (2001) The origins and biological significance of the coccidial lesions that occur in chickens vaccinated with a live attenuated vaccine. Avian Pathology, 30: