Nutrition: Can a feed supplement improve performance and help clean up the barn?

Wednesday, April 2, 2008

Yes, suggests research at the University of Arkansas. But whether or not the additive will 'clean up' after itself in a commercial setting remains to be seen

by JANICE MURPHY

Intensive swine production practices create many manure management challenges - storage and handling of manure, odour control, accumulation of solids on pen surfaces and in manure pits.    

The presence of offensive odours and accumulation of manure solids are the direct result of inadequate microbial decomposition of manure. Researchers admit that these problems are further complicated by swine diets deliberately formulated to contain high levels of trace minerals and antibiotics which stifle the very bacteria needed for effective manure decomposition.

Many commercial solutions are available to alleviate problems associated with odour and manure handling, including aeration of manure pits, feed additives (such as crystalline amino acids, fermentable carbohydrates, enzymes, or microbes), and odour-masking pit additives. Unfortunately, these methods can be costly, inconvenient or even ineffective in supporting the manure breakdown process.

Research has shown that Bacillus species are particularly appropriate as feed additives because of their stability as spore-forming bacteria and ability to produce a wide variety of enzymes that promote manure digestion. The spore coat of Bacillus serves as protection from heat, enzymatic degradation and stomach acid, therefore allowing a dietary source of these microorganisms to provide a convenient and continuous inoculation strategy for manure storage facilities.

Research at the University of Arkansas recently evaluated the ability of dietary supplementation with specifically selected strains of Bacillus subtilis and Bacillus lichenformis to improve performance and manure decomposition of growing/finishing pigs, as measured by pen cleaning time.

Three experiments were conducted at the University of Arkansas Swine Research Unit, involving 336 crossbred barrows and gilts. In each experiment, pigs were fed one of two dietary treatments (0 and 0.05 per cent Bacillus-based direct-fed microbial) during the grower-finisher phase to provide 1.47 x 108 colony forming units (cfu) of Bacillus organisms per gram of supplement. Pigs were weighed and feed intake was recorded at the start and end of each phase (starter, grower, and finisher).

At the end of the first and third experiments, pen cleaning time was measured. Pens were scraped with a scraper and then washed with a high pressure washer delivering unheated tap water at 2,000 psi. In addition, two solid manure mat samples (four grams each) were collected from solid manure build-up in each pen and the time required to disperse each sample was determined in the laboratory.

Supplementation with Bacillus in the first experiment increased the gain-to-feed ratio (G:F) in the trial overall (starter to market weight) compared to control pigs, but no difference was observed between Bacillus and control pigs in either of the other two experiments. Armed with these results, the researchers decided to combine the results of all three studies (Table 1).

In the combined analysis, average daily gain (ADG) and average daily feed intake (ADFI) did not differ between the two dietary treatments. However, G:F increased when pigs were fed diets containing Bacillus compared to control diets during the finisher phase and in the overall growing-finishing period.

The researchers suggested that G:F may have improved in the finishing phase of the Bacillus pigs as a result of some well-known functional characteristics of these microorganisms. Bacillus species are known to produce extracellular degrading enzymes, such as amylase, cellulase, lipase and protease, which improve nutrient digestion and feed utilization and, ultimately, the efficiency of growth.

Alternatively, Bacillus organisms may have improved pig health by acting as a probiotic and enhancing immune function. Based on the data derived from this series of experiments, the specific mechanism could not be determined.

The time required to dissolve the manure mat in the lab was significantly lower (33 per cent) in samples collected from pens containing pigs fed Bacillus compared to control pens. Although the time required to wash pens housing control or Bacillus pigs did not differ (8.7 and 8.5 minutes, respectively), the researchers noted that this result was supported by numerically less total time needed to clean (scrape and wash) the Bacillus pens (23 vs. 21 minutes). However, these differences were not statistically significant.

The researchers are confident that the rapid dispersal of the solid manure samples obtained from pens housing Bacillus pigs is a clear indication that the microorganisms were effective at breaking up manure solids in the barn and in the pit. The Bacillus strains included in the supplement were selected for their multiple enzyme activities, which likely explains the speed of the manure dispersal in the treated samples. Unfortunately, the nutrient composition of the manure samples was not measured in this study, which might have shed some light on the mechanism involved.

To bring it back to the farm, an additional study was carried out over 16 months on a large commercial swine operation. All-in, all-out wean-to-finish facilities within the system were randomly assigned as control or treated sites. Initially, both sites were fed typical corn-soybean meal diets for seven months in order to collect baseline data. Subsequently, treated sites were switched over to the 0.05 per cent Bacillus diet and control sites continued feeding the same diet without the supplement.

One of the major challenges in implementing new technologies within the swine industry is measuring the benefits of these technologies under commercial conditions. Statistical process control is a technique which provides a way to monitor an agricultural system, much like manufacturing industries monitor their production processes, to detect changes after implementing new technologies.

Because of the limitations (labour, facilities, and biosecurity) in a large commercial swine operation, such as the one used in this trial, the evaluation of the Bacillus treatment on-farm focused on data that could be pulled out of existing records already being collected with the PigChamp software system and only included ADG, G:F, and death loss percentage over the growing-finishing period. Using statistical process control analysis, the researchers were able to conclude that adding Bacillus to the diet increased the expected mean for ADG and decreased the expected mean for death loss percentage.

Overall, the results of the experiments in Arkansas showed that supplementing diets of grower-finisher pigs with a specially formulated Bacillus additive improved feed efficiency and decreased the time required to disperse a manure sample in a controlled environment. On a commercial operation, the supplement improved rate of gain and decreased mortality of pigs during the growing-finishing period. Whether or not the additive will "clean up" after itself in a commercial setting remains to be seen.  BP

Source: Davis, M.E., Parrott, T., Brown, D.C., de Rodas, B.Z., Johnson, Z.B, Maxwell, C.V. and
Rehberger, T. 2008. Effect of a Bacillus-based direct-fed microbial feed supplement on growth performance and pen cleaning characteristics of growing-finishing pigs. J. Anim. Sci. Published online January 11, 2008.

Janice Murphy is a former swine nutritionist with the Ontario agriculture ministry who now lives and works in Prince Edward Island.