Finding
All breeding animals were of the same breed and they were vaccinated against Aujeszky’s disease, porcine reproductive and respiratory syndrome, parvovirus infection, erysipelas, leptospirosis and E coli.
Paper
Evaluation of probiotics as a substitute for antibiotics in a large pig nursery
Abstract
ANTIMICROBIALS, when used as growth promoters, are claimed to improve daily weight gain by 3 to 9 per cent and feed utilisation by 2 to 7 per cent, with fewer scour problems (Visk 1978, Hedde 1984, Doyle 2001). For this reason they are customarily used in pigs even on high-health status farms. They appear to act by reducing the pathogenic bacteria and modifying the microflora in the gut, providing more nutrient availability for the animal itself and less substrate for the bacterial organisms to use for their own growth (Visk 1978, Hedde 1984). Dritz and others (2002) showed that antibiotics are justified for use only in nursery pigs but not in growers and finishers. Despite their beneficial effects, recent concerns regarding the presence of drug residues in edible animal products and the potential transfer of antibiotic resistance to human pathogens has directed research towards alternative solutions such as probiotics. Legislation to phase out the routine feeding to food animals of eight classes of antibiotics as feed additives (penicillin, tetracycline, bacitracin, macrolides, lincomycin, streptogramin, aminoglycoside and sulphonamides) judged to be directly or indirectly of human medical importance has been recently introduced in the USA and has already been applied in the EU. Thus, alternative solutions should always be sought. Probiotics are live cultures of harmless bacteria or yeast species (for example, Lactobacillus, Streptococcus and Saccharomyces species) that equilibrate intestinal microflora, to the benefit of the animal (Fuller 1989, Ferencik and others 2000). They may promote growth by competing with harmful gut flora, and by stimulating the immune system of the animal and therefore increasing its resistance to infectious agents (Tannock 1980, Fuller 1989, Khajarern and Khajarern 1994). Several studies in various animal species have indicated a beneficial role of probiotics against diseases; for example, they may control some Escherichia coli-induced diseases (Khajarern and Khajarern 1994, Zani and others 1998, Kyriakis and others 1999, Genovese and others 2000). Other studies including untreated, antibiotic-free control pigs have shown that the average daily weight gain (ADG) and feed conversion ratio (FCR) are significantly improved after probiotic treatment (Kyriakis and others 1999, 2003, Kritas and others 2000). This short communication describes a study to examine the ability of probiotics to act as a substitute for growthpromoting antibiotics on the health and productivity of weaned pigs on one farm with high-health status. The study was carried out from October 2002 to October 2003, on a commercial, three-site production farm of 1600 sows in Minnesota, USA. All breeding animals were of the same breed and they were vaccinated against Aujeszky’s disease, porcine reproductive and respiratory syndrome, parvovirus infection, erysipelas, leptospirosis and E coli. The piglets on the farm were weaned in weekly batches of (mean [sd]) 520 (50) animals at the age of 20 (2) days and, after separation by sex and bodyweight, were transferred to two adjacent off-site nurseries, where they remained until the age of 64 (3) days. Each nursery contained four small rooms of 16 pens and two large rooms of 32 pens, with approximately 22 pigs per pen. The nursery rooms were filled sequentially one after another, and each small room contained pigs of the same week of age, or of two sequential weeks of age in the large rooms. A common outer corridor connected the rooms in each nursery, and footbaths in the corridor outside each room were used before personnel entered. A separate feed bin supplied each room. The pigs were fed ad libitum rations containing low doses of antibiotics: 400 ppm neomycin (Neomix; Phibro Animal Health) for the first five to seven days postweaning; 100 ppm neomycin plus 100 ppm oxytetracycline (Neo-Terramycin; Phibro Animal Health) for the next seven days, and thereafter 20 ppm tylosin (Tylan 10; Elanco Animal Health) up to the age of 70 days. The programme had been started five years previously to prevent E coli postweaning diarrhoea. Postweaning mortality in the nurseries was historically low (<2 per cent). To test the effects of probiotics compared with subtherapeutic doses of antibiotics, the product BioPlus 2B (Chr Hansen) containing 1012 colony-forming units total Bacillus content (Bacillus licheniformis and Bacillus subtilis) per 0·45 kg of product was used instead of the antibiotics. The US Food and Drug Administration has approved this product for use in feeds, and the Bacillus species strains included do not produce any antibiotic (Anon 2005). The product was included in the usual rations of the nursery period at the standard dose of 0·45 kg/tonne of complete feed. Forty-two nursery rooms were used chronologically but in an alternate mode; for example, the pigs of the first room received feed with probiotics, those of the second room feed with antibiotics, those of the third room feed with probiotics, and so on. At the end of the trial, the two treatment groups, that is, pigs receiving the usual feed that contained antibiotics (21 rooms) and pigs receiving the same type of feed but containing probiotics instead of antibiotics for the same period (21 rooms), were compared. As shown in Table 1, the average age and bodyweight of the pigs between the groups did not differ significantly at the beginning of the trial. Mortality and reasons of death were recorded by the farmer for each group of pigs up to the end of the nursery period. At that time, the pigs were weighed again. The feed consumption per group was also recorded during this period, and the ADG, the average daily feed intake (ADFI) and the FCR were calculated. At least 20 treated and 20 control rooms were needed to detect a 1·50 per cent difference in mortality (α=0·05, power 80 per cent, sd 1·5 per cent). Each parameter was recorded and analysed with ‘room’ as the experimental unit by one-way analysis of variance using the SPSS for Windows statistical package (release 11.0.1; SPSS). The results shown in Table 1 were derived from a total of 10,955 pigs in 21 probiotic rooms and 10,800 pigs in 21 antibiotic rooms. In both treatment groups, the nursery periods had the same average length. The bodyweight of pigs at the end of the nursery period, the ADG, ADFI and FCR were similar for both groups. The cost of feed per pig and per kg of bodyweight was also similar. There was no difference in morVeterinary Record (2005) 156, 447-448
Authors
S. Kritas, R. Morrison
Journal
Veterinary Record