Nutrition: Potato protein can improve growth and reduce bacteria in starter diets

Wednesday, October 8, 2008

Research has shown that using a new potato variety called Gogu valley in starter diets not only helps growth but also provides an alternative to antibiotics

by JANICE MURPHY

Pork producers have always been innovators, pushing the limits of what is considered possible to explore the physiological and biological boundaries of the pig. In this quest for efficiency, the industry has decreased weaning age in an attempt to increase the number of pigs produced per sow per year and, ultimately, to improve profitability.

The end result of this trend is the need for very specialized starter diets which contain highly digestible ingredients, such as dried whey, spray-dried plasma and high-quality fish meal.

With this high degree of specialization comes a bigger price tag. As a result, research has focused on finding alternative feed ingredients which improve starter growth performance while controlling feed costs.

Potato protein is one option that may be a cost-effective replacement for the more commonly used protein sources in starter diets. Research in Holland and Kansas has shown that pigs fed potato protein at three to five per cent of the ration had improved growth performance compared to control diets.

Antibiotics have been routinely used in starter diets as growth promoters, but recent history suggests that their use for non-therapeutic purposes is short-lived. The general public and regulatory agencies are peeking over the shoulder of modern agriculture, making it necessary to seek out alternatives to antibiotics in order to maintain 50 years of progress in growth performance.

In addition to the positive effects on growth, potato protein may be able to serve another purpose in starter diets. Recent research in Korea has suggested that potato protein may be an alternative antimicrobial source. Antimicrobial peptides have been isolated and characterized from multiple sources of tissues and organisms.

Researchers have noted that plants and animals are in close contact with many different types of bacteria and fungi, but this association rarely results in the development of disease, mainly because of the existence of antimicrobial defense systems. These antimicrobial peptides are described as "small gene-encoded peptides that show a broad range of activity against gram-negative and gram-positive bacteria, fungi, and myco-bacteria."

Potatoes (Solanum tuberosum) are cultivated for human consumption all over the world and are known for their antimicrobial and antifungal properties. A new potato variety called Gogu valley (Solanum tuberosum L. cv. Gogu valley) was recently developed and is recognized for its resistance to diseases and rotting during storage.

Researchers at Chosun University in Kwangju, Korea, undertook a study with a total of 280 weaned pigs (Landrace x Yorkshire x Duroc) to investigate the effect of feeding different levels of potato protein derived from the Gogu valley variety on growth performance, nutrient digestibility, immune response, small intestinal morphology and bacterial populations in the digestive tract.

Pigs started the experiment at an average of 6.42 kilograms of bodyweight and 23 days of age. They were randomly assigned to one of five treatments: positive control (basal diet + 150 mg/kg apramycin and 10 mg/kg colistin sulfate); and four potato protein levels (0, 0.25, 0.50, or 0.75 per cent). Diets were fed in two phases – phase one (day 0 to 14 postweaning) and phase two (day 14 to 28 postweaning).

Over the one-month trial, pigs fed the control diets showed improved overall average daily gain (ADG) and feed efficiency (G:F) compared with pigs fed potato protein. However, increasing levels of potato protein linearly improved ADG, average daily feed intake (ADFI), and G:F, and at the 0.75 per cent potato protein level the results were comparable to that of the control pigs (Table 1).

The bacterial populations which existed in the feces of pigs fed control and potato protein diets were similar regardless of treatment, except for total bacteria and coliform bacteria in the feces on days 14 and 28, which were lower in control pigs (Table 2).

Weaning can be a stressful time, with pigs facing a host of stressors which can harm their ability to eat and grow efficiently. At weaning, greater fluctuations in intestinal flora occur, providing an opening for pathogenic bacteria to invade the system and compromise performance. Researchers have estimated that as much as six per cent of the energy in a pig's diet can be wasted in the stomach and intestine due to microbial fermentation.

Until now, antibiotics have been added to feed in order to alter the activities of these microbial populations by inhibiting pathogenic bacteria and thereby preventing this loss in energy. With growing concerns over the use of antibiotics, the pork industry may not have this option for much longer.

The results of this study demonstrate that feeding potato protein derived from a new potato variety, Gogu valley, to weanling pigs can be an effective method of improving growth performance and reducing pathogenic bacteria making it a unique alternative to in-feed medication. The researchers hope to continue their work by digging deeper into the potato itself to try to identify the specific peptides or mechanism responsible for the antimicrobial activity. BP

Janice Murphy is a former swine nutritionist with the Ontario Ministry of Agriculture, Food and Rural Affairs, who now lives and works in Prince Edward Island.

Sources:

Z. Jin, Y. X. Yang, J. Y. Choi, P. Shinde, S. Y. Yoon, T.-W. Hahn, H. T. Lim, Y. Park, K.-S. Hahm, J. W. Joo and B. J. Chae. 2008. Potato (Solanum tuberosum L. cv. Gogu valley) protein as a novel antimicrobial agent in weanling pigs. J. Anim Sci. 2008. 86:1562-1572. doi:10.2527/jas.2007-0414.

C. A. Kerr, R. D. Goodband, J. W. Smith, II, R. E. Musser, J. R. Bergstrom, W. B. Nessmith, Jr., M. D. Tokach, and J. L. Nelssen. 1998. Evaluation of Potato Proteins on the Growth Performance of Early-Weaned Pigs. J. Anim. Sci. 76:3024–3033.