A broader outlook will be required when managing porcine enteric disease once Zinc Oxide is withdrawn as a therapeutic treatment in June and for most herds, a multifaceted approach will be needed to effectively treat, control and prevent post-weaning diarrhoea and associated losses. Routine diagnostics are already becoming an integral part of health management strategies, with many veterinary specialists urging producers to adopt more rigorous disease surveillance programmes.

Paul Thompson, BA VetMB MRCVS, PVS senior vice-president and veterinary surgeon at the Garth Pig Practice, says tackling post-weaning scours requires a clear understanding of a herd's disease complex because a multitude of microbial strains can be implicated.Identifying which key pathogens are circulating, and the reasons why they are persistent, can help herds develop defined management plans, aimed at reducing infection risk and improving piglet immunity. "Culture and sensitivity investigations will be imperative, going forward. Producers and vets need to know what bugs they are dealing with," he says.

He advocates regular screening as the clinical information provided will help determine what control measures are needed to keep disease under control. Using diagnostic techniques, such as ELISA tests, quantitative PCR tests and serology, provide valuable biological evidence that will help vets identify what's causing infections, the microbial load circulating in the herd. These details that can help them build a disease profile and develop effective, often bespoke, prevention and control programmes.

Many pig businesses have already removed zinc from their post-weaning health care routines and are choosing to vaccinate pigs to protect them against key enteric pathogens. Routine surveillance is also beginning to feature within management routines and the combination of both strategies, combined with and more stringent hygiene, is revealing positive outcomes.

Undetected and eating profits Ileitis, a bacterial infection caused by Lawsonia Intracellularis, is a wide spread problem in rearing and finishing herds. Also known as Porcine Proliferative Enteropathy (PPE) and Porcine Intestinal Adenomatosis (PIA), the condition is often misdiagnosed, frequently undetected and rarely considered a major problem. In many herds it exists at sub-clinical levels and unless an outbreak is severe causing a spike in mortality in finishers and or a high incidence of watery-bloody diarrhoea, inappetence, depressed growth and general morbidity.

Dr Ruben Del Pozo Sacristan, UK technical manager for pigs at MSD Animal Health says infections tend to exist at sub-clinical levels and are often misdiagnosed. "Unless an outbreak is severe - usually presenting as a spike in mortality rates in late-stage finishers, a high incidence of watery-bloody diarrhoea, inappetence, depressed growth and general morbidity - Ileitis is rarely considered significant. But it does compromise growth rate and FCR and that affects production economics." he adds.

A trial, carried out on a commercial, 240-sow farrow-to-finish farm in East Anglia showed how vaccinating pigs against Lawsonia improved production outcomes and economic returns. This herd had a longstanding ileitis problem which was controlled using antibiotic medication. The results were mixed and the herd still experienced episodes of diarrhoea in growing pigs with some PHE related deaths in the finishing herd. Low-grade scour was also evident from weaning. Ileitis related mortality was around 3 per cent and pig growth and carcase quality were variable.

The investigation monitored four batches of pigs that were vaccinated with Porcilis Lawsonia® at 21 days of age. Each piglet received a single, 2ml dose of the vaccine (intramuscular injection) and were weaned at 28 days. No medication was used during the rearing-finishing period and performance was recorded. Changes to dung consistency and pig uniformity were noticed early on and in the nursery and fewer pigs 'went behind'. At grower stage there was a marked improvement in pig health and diarrhoea outbreaks decreased. Growth rates increased by 30 gday during the weaner - grower period and performance was more consistent.

In the finishing house PHE deaths stopped, ADG improved by between 40 and 45 gday and pigs reached market weight six days earlier and pig quality was noticeably better. Growth was also more uniform, and that meant pens could be cleared sooner. The farm was able to clear 20 per cent of its finishers in the first draw, with 70 per cent sent for slaughter the following week, with the remainder were sold in week three leaving pens empty ready to be cleaned, rested and restock at the end of week four. This shorter 'clearance time', taking two to three weeks, rather than four to five weeks which had previously been routine, improved pig-flow through the farm and allowed more efficient use of finishing accommodation.

Another interesting outcome was improvements seen in carcase quality. Vaccinated pigs were more evenly sized, had better conformation and a higher number of them achieved optimum back fat and leanness.

Danish experience values vaccines
E. coli is another persistent cause of post-weaning scours and although many herds routinely vaccinate sows before farrowing to protect them and their young piglets from infection during lactation, this maternal derived immunity is not sustained beyond weaning. Choosing to vaccinate piglets just before or soon after weaning can bolster their immunity. When used in combination with good hygiene and disinfection protocols many herds find they can effectively control, E.coli related scours and other associated problems. Kirsten Jensen, swine vet and technical adviser at Elanco Animal Health, has been working with Danish vets and pig farmers to investigate zinc-free methods to control post-weaning E. coli diarrhoea.

More than 90 per cent of Danish rearing herds were regularly using ZnO to control scours, but Ms Jensen says producers and veterinarians have been proactively seeking alternatives for quite a few years.

"Removing therapeutic levels of Zinc from piglet diets will be a challenge and producers and veterinary professionals will need to works together to develop control strategies that are appropriate for the very different clinical conditions they will be presented with. Alternatives to ZnO are available and E. coli vaccination is proving a very useful tool, but farmers must consider other options too, such as nutritional adjustments and improvements to unit hygiene and biosecurity." she said.

Vaccination with Elanco's Coliprote® is proving a useful tool and an increasing number of Danish herds are successfully using this in-water vaccines. Feedback from some farms using this vaccine report a 2 per cent reduction in mortality with good growth and performance recorded across the early rearing period. A vet survey in 2020, conducted by SEGES Pig research Centre, also concluded that Coliprotec offered effective E. coli protection to young weaners, although it should not be used in isolation. Danish veterinary experience does show varying degrees of efficacy in the field, but when this vaccine is used alongside other infection control measures, outcomes do confirm it is a useful method of reducing E. coli-associated weaning scour and need for antibiotic treatments.

Covid jab research benefits scour vaccine development

A new vaccine to combat post-weaning diarrhoea is currently undergoing trials at SEGES Danish Pig Research Centre and Copenhagen University. The combination vaccine, which has been under development since 2019, benefits from research carried out when producing a human COVID-19 vaccine. Poul Bækbo, Senior Veterinary Adviser, Nutrition & Health, SEGES said this vaccine has huge potential for both Danish and international pig production and if successful will have a significant impact reducing the use of antibiotics in piglet production and make in-feed zinc treatments unnecessary. Initial trials with the combination vaccine will began in May. A total of 60 pigs will vaccinated and their immune responses closely monitored. The study aims to find out if the pigs produce antibodies against E.coli, Lawsonia and Brachyspira, the bacterial pathogens commonly associated with post-weaning scours. This new vaccine aims to protect pigs against all three organisms.