FOR academic swine nutrition researchers, the place to present research is typically the American Society of Animal Science's midwestern section meeting held each March in Des Moines, Iowa, but this year, several abstracts presented at the southern section meeting broke ground in young pig nutrition.
In an abstract that received a National Pork Board Swine Industry Award for Innovation, J.R. Donaldson and J. Grissett of Mississippi State University, J.A. Carroll, N.C. Burdick Sanchez and T.R. Callaway of the U.S. Department of Agriculture's Agricultural Research Service and T.B. Schmidt of the University of Nebraska-Lincoln examined the novel use of lipid-producing bacteria to increase circulating triglycerides (TAGs) in swine (abstract 59).
Donaldson et al. said weanling pigs are at a high risk of succumbing to illness primarily due to an insufficient supply of available energy and, therefore, a weakened immune system. Solutions have been investigated to supplement feed with alternate energy sources, yet pigs still face limitations with the utilization of these sources due to their relatively immature gastrointestinal systems.
Donaldson et al. said their objective was to evaluate whether providing swine with bacteria that produce TAGs, such as the bacterium Rhodococcus opacus (RO), could increase the concentrations of circulating TAGs and, thus, available energy.
They housed 36 weaned pigs at 30 days of age in individual pens. After a two-week acclimation period, the pigs were randomly assigned to one of three treatment groups of 12 pigs each, stratified by bodyweight.
Treatments consisted of daily oral supplementation for five days with: (1) RO at 1x1010 colony-forming units (CFU), (2) an alternate form of RO (JD103) at 1x1010 CFU that secretes TAGs into the surrounding environment or (3) an equivalent volume of phosphate-buffered saline (PBS).
Serum samples were collected every six hours for 96 hours and analyzed for non-esterified fatty acids, TAGs, free glycerol and glucose concentrations.
Fecal samples were collected daily to assess shedding of RO or JD103 by viable plate counts. At the conclusion of the trial, gastrointestinal tract contents were collected and analyzed for colonization patterns of RO or JD103.
According to Donaldson et al., circulating TAGs increased by 84 hours in pigs supplemented with either RO (P = 0.04) or JD103 (P = 0.01) in comparison to PBS controls. Both RO and JD103 were present in the gastrointestinal tract, with minimal shedding observed, suggesting that both forms of RO are capable of colonizing within the tract.
Donaldson et al. concluded that these data indicate that lipid-producing bacteria can be used to provide an available source of utilizable lipids to weanling pigs and could potentially decrease detrimental effects associated with illness and reduced feed intake during this transitional period. They noted that further research is needed to determine whether this correlates with improved immune function in the presence of pathogens.
The researchers added that these are the first data to demonstrate the potential use of a non-pathogenic bacterium to improve the health, well-being and overall productivity of swine.
In abstract 55, Donaldson, T.C. McLaurin of Mississippi State, Carroll and Burdick Sanchez looked at the effects of citrus pulp on the viability of a probiotic and subsequent effects in the presence of pathogens.
They said the probiotic Saccharomyces cerevisiae subtype boulardii is commonly provided to weaned piglets and nursing sows to promote intestinal health through stabilization of the gut flora.
However, they explained that other recent research they have conducted found that supplementing this probiotic to feed containing the citrus pulp reduced (P = 0.01) average daily gain (ADG) of newly weaned pigs that were challenged with salmonella.
The researchers said the objective of the current study was to determine if this reduction in ADG could potentially be attributed to an abnormal interaction of the live yeast with salmonella and citrus pulp and whether similar interactions would occur in the presence of other pathogens, such as Escherichia coli O157:H7.
Using an in vitro approach, viability was assessed for the live yeast and salmonella or E. coli in a swine fecal growth medium supplemented with either 0% or 5% citrus pulp through viable plate counts for 48 hours, the researchers said.
According to the research group, citrus pulp reduced (P < 0.01) populations of live yeast by 1.5 log10 within 48 hours after exposure, which they said suggests that citrus pulp may exhibit fungicidal activity.
In co-cultures of salmonella and live yeast, the populations of live yeast decreased (P < 0.001) by 1.5 log10, the researchers reported, but when citrus pulp was included in the co-culture, greater reductions in the populations of salmonella and live yeast were observed than in either single treatment.
Together with the previously observed decreased ADG, these data suggest that the increase in salmonella lysis from exposure to both live yeast and citrus pulp may increase the release of cytotoxins, which could potentially compound the immune response, the researchers explained.
Populations of E. coli did not decrease in the presence of live yeast, indicating that this enteric pathogen responds differently to this treatment than salmonella, the researchers noted.
Although further research is needed to determine if this effect occurs in vivo, the researchers concluded that caution should be exercised in providing citrus pulp to swine being fed diets supplemented with live yeast probiotics.
M.J. Estienne and A.F. Harper of Virginia Polytechnic & State University's Tidewater Agricultural Research & Extension Center examined the effects of dietary menhaden fish oil (MFO) on the growth performance of gilts farrowed by sows fed gestation and lactation diets with or without MFO (abstract 54).
Estienne and Harper said the positive effects of dietary omega-3 polyunsaturated fatty acids (PUFAs) on swine reproduction, such as an increase in boar sperm numbers, have already been reported, but the effect of a rich PUFA source on growth and reproduction in replacement gilts has received little attention.
In the experiment, pregnant sows received one of two isocaloric diet regimens that were equal with respect to amino acids, minerals and vitamins: four sows were fed corn/soybean meal gestation and lactation diets (control), and three sows were fed corn/soybean meal gestation and lactation diets that included 4% MFO.
At weaning (21 days of age), 24 gilt pigs farrowed by sows fed the control or MFO diets were placed in pens of three gilts each and were given ad libitum access to nursery and grow/finish control or MFO diets as per a 2 x 2 factorial arrangement of treatments (three pens per group), Estienne and Harper said.
According to the researchers, there were no effects (P > 0.1) on ADG of pig diet or the interaction of sow diet and pig diet, but pigs born to sows fed MFO diets tended (P = 0.09) to have greater overall ADG than pigs from sows fed control diets (0.78 kg versus 0.67 kg).
For gilt bodyweight, the sow diet by time interaction was significant (P < 0.01) in that pig bodyweights at weaning were similar (P > 0.1) among groups, but at the end of the 18-week trial, gilts born to sows fed MFO diets had greater (P < 0.01) bodyweights than pigs from sows fed control diets (105.2 kg versus 94.1 kg), Estienne and Harper said.
There were tendencies (P = 0.07) for pig diet to affect average daily feed intake and gain:feed, with gilts on MFO diets consuming less feed (1.67 kg versus 2.0 kg) but displaying a greater gain:feed (0.43 versus 0.36) than gilts fed the control diet, the researchers noted.
Estienne and Harper suggested that feeding sows diets containing omega-3 PUFAs during gestation and/or lactation may affect the resulting gilt offspring such that growth is enhanced during the growing/finishing period. They added that gilts fed diets with MFO had decreased feed intake but enhanced gain:feed.