Maximising feed efficiency in weaners

This is the full text of the article on Dr Amy Taylor’s pig nutrition PhD project that appeared in the January 2014 issue of Pig World, where an unfortunate production error meant a significant part of the feature was missing. The project, which was undertaken at the University of Leeds, has helped ABN fine-tune its weaner diets

A significant input affecting a pig unit’s efficiency and performance is the feed component, and making investment into nutritional research and development vital for future improvements. According to ABN’s pig nutritionist, Dr Steve Jagger, a particular area of focus is the role for nutrition in addressing growing industry pressures to reduce the amount of medication and antibiotics being used in pig production.

Dr Jagger highlights that the weaner phase is a particularly vulnerable stage and a period where medication may be needed.

“Weaners are at risk due to the heightened levels of stress involved when they are moved into new accommodation and into larger peer groups, while at the same time their passive immunity from the sow is naturally waning,” he says.

“This can lead to pigs with low immune competence and a higher risk of experiencing diarrhoea and other health challenges, which can lead to a need for treatment.”

Previous work has clearly demonstrated that lowering dietary protein levels can reduce the incidence of diarrhoea, and Dr Jagger was keen, therefore, to explore the effects of reducing protein levels on weaner performance, with the view that a ‘safer’ diet could be produced with such an approach resulting in fewer cases needing medical intervention to combat challenges, such as diarrhoea.

A recently published PhD, conducted by Dr Amy Taylor over a four-year period at the University of Leeds, was funded by ABN and the Biotechnology and Biological Sciences Research Council (BBSRC) to research part of this theory. The thesis title, The effects of previous dietary lysine experience on subsequent growth response in pigs details the specifics covered by this work.

Dr Jagger explains that with his industry experience and knowledge of existing research, he was able to establish the initial concept, which Dr Taylor then studied at length for her PhD.

The hypothesis, he says, was that if protein intake, specifically lysine, was restricted during the weaner phase and then a high-lysine diet was introduced during the grower and finisher phase, pigs would demonstrate compensatory growth with increased feed efficiency.

“If we could get the same overall performance but with a reduced protein intake during the vulnerable weaner phase, we would expect to be able to reduce some of the medication demands at this time,” he adds.

Dr Jagger explains that prior to Dr taylor’s work ABN had funded several pilot projects alongside the University of Leeds to establish the value of differing levels of lysine, fed at different ages of the pig for best growth performance results. Trial work also looked to establish what level of lysine should be included in the diet that followed the period of protein restriction.

“This initial pilot work helped us to establish the best possible methodology for Dr Taylor’s PhD,” he says, adding that the new work on compensatory growth is unique in that the method incorporated a higher than standard protein diet for the grower period following the restricted weaner diet. “Previously, researchers in this area have always fed pigs standard diets following any periods of restriction.”

Dr Taylor explains that the fundamental methodology involved in her PhD included undertaking four trials over a period of nearly four years, using the same facilities, genotype of pig and period of growth restriction.

“Two treatments in each trial were the same, which allowed us to establish if consistent results were seen,” she says.

The pig genotype used for the trials were Hampshire sire x Large White cross Landrace dam, with a total of 576 pigs studied. The pigs were weaned onto the trial at about 27 days, and they remained on the trial until they were slaughtered, with regular measurements of body weight and feed input taken throughout to give feed efficiency statistics. Health scores and antibiotic treatments were regularly recorded but, no effect of treatment was observed under the university conditions.

During the three-week period post weaning, the pigs were fed ad-lib, receiving either a high (17.5g/kg) or a low (8g/kg) lysine diet. These two lysine diets were established following the earlier pilot trial work.

“We then fed a higher-protein diet to all pigs during the period following the weaner phase, which gave two dietary treatments; a control versus a restricted weaner treatment, where the main difference was the protein levels during the weaner phase (4-7 weeks),” Dr Taylor says.

Protein concentrations in diets were determined by lysine concentrations with all amino acids kept at the ideal ratio to lysine, thus ensuring that lysine was the first limiting amino acid. The diets met all other nutritional requirements.

“During the weaner phase, across all four trials, consistently significant results were seen, proving the low lysine diet resulted in a reduced growth performance,” Dr Taylor says. “But inconsistent results relating to the grower and finisher phases meant that compensatory growth wasn’t consistently observed across the four trials, and cannot be reliably predicted.”

She concludes that although considerable attention and effort has gone into studying the growth of pigs following a period of restriction, it’s clear there are many aspects that are still not fully understood.

“There’s definite scope for further research in this area before any commercial practical use can be made of compensatory growth,” Dr Taylor adds. “However, this research certainly identifies the need to ensure that diets match the exacting nutritional requirements of a pig at each stage of its growth.”

Dr Jagger agrees, noting that working with the unit to ensure the right feed specification is fed is essential to maximise performance.

“Currently, it’s not possible to guarantee that we can get the growth back following feeding regimes that include restricted protein diets and target compensatory growth,” he says.

But despite the research showing an inconclusive outcome, Dr Jagger says there are still commercial gains to be made from this PhD.

“The comprehensive weaning to slaughter data set collated during this research has allowed us to refine diets to improve the performance of young pigs,” he says. “This has allowed the development of a growth model and feed programming tool for our sales team to be able to establish the profitability of feeding certain diets based on their performance potential.”

Dr Jagger adds that continued research into other areas of weaner nutrition will help ensure new developments continue to become a reality on farm, while also exploring the underlying concept of reducing medication use without limiting performance.

“Maintaining pig health while reducing the use of antibiotics is an extremely important issue facing the industry,” he says. “It’s one that definitely needs further research to truly understand how nutrition can have a positive impact in this area.

“Research that has been conducted which may help improve the health and performance of the pig includes the examination of diet acidification in both weaner and finisher pigs and this is now widely practiced.

“There’s also a need to establish further information on the effect of feed structure and particle size on gut health and subsequent feed efficiency. The aim of all the research in this arena is to maximise feed efficiency and optimise the pigs’ health.

“It is a case of attempting to strike a balance between maintaining pig production and making inroads into reducing medication use,” Dr Jagger adds. “Developments are always on-going and I’d like to see further research

to help us understand the interactions between health and nutrition in general, and between immune response and feed efficiency in particular.”

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