The increased fat deposition following vitamin withdrawal is in keeping with an Iowa State University study (Lutz and Stahly, 1998) that looked at riboflavin requirements for protein versus fat accretion in growing pigs. In the Iowa work, protein accretion and feed efficiency both improved linearly as dietary riboflavin concentration increased. The researchers further noted that the riboflavin requirement for protein accretion was six times higher than for fat accretion.
Although vitamin requirements for protein or fat accretion will vary with the age and size of the animal (as well as other factors), the general relationship in vitamin requirements for fat versus protein that the Iowa researchers reported should still hold for finishing pigs as well. Indeed, because of the differences in conditions between commercial and university conditions, the above studies with finishing pigs may have underestimated the importance of adequate vitamin intake throughout finishing to control fat accretion and maintain the meat's nutritional profile.
Before pigs entered these studies, they received fortification levels of many vitamins that were higher than often fed. For example, dietary vitamin A fortification was 45 and 71 percent greater than the DSM Nutritional Products minimum recommended vitamin A fortification levels for the grower and finisher stages, respectively. Vitamin E fortification levels were 33 and 50 percent higher than DSM minimum recommendations. The increased fortification levels may have influenced the later results. If vitamins are withdrawn prior to slaughter, lower fortification levels are likely to be used during the feeding period.
In addition, the vitamin withdrawal programs used in these studies would present producers with sizable management challenges that scientists can avoid in the controlled environment of university research. These studies had between 2 and 12 highly uniform pigs per pen, compared to the 20 to 30 pigs per pen typically found in commercial situations. The studies also began with, and maintained, remarkable weight uniformity within the pens throughout the study.
In a typical production unit, by contrast, considerable variation between animals occurs even by the time they reach the average starting weights of these studies.
Furthermore, weight variations tend to increase with time. A 1996 survey conducted by North Carolina State University found that within one group of commercial pigs averaging 240 to 250 pounds, the actual spread ranged from 170 to 300 pounds.
Because nutritional requirements are generally recognized as greater in lighter-weight pigs, there is a considerable risk of short-changing these animals if the goal is to exactly meet, but not exceed, the nutritional needs of average animals in a pen or group. In a commercial operation, the increased complexity of feed management would quickly prove insurmountable. Otherwise, any savings in feed costs from the heaviest animals would quickly prove counterproductive because of lower weight gains, poorer feed conversion and (or) lower carcass quality in the lighter pigs.
Such losses would directly reduce the profitability of the individual producer, but could be quickly addressed once they were identified. If consumer perceptions of pork's nutritional value were also affected, the cost to the entire industry would be even greater and far more difficult to correct.
- Deyhim, F. et al., 1996. Vitamin and trace mineral withdrawal effects on broiler breast tissue riboflavin and thiamin content. Poultry Sci. 75:201.
- Edmonds, M.S., and B.E. Arentson. 1999. Effect of supplemental vitamins and trace minerals on performance and carcass quality in finishing pigs. J. Anim. Sci. 77 (Suppl.1):129.
- Kim, I.H., et al., 1996. Removing vitamin and trace mineral premixes from finishing diets. Kansas State University Swine Day Report, p. 100.
- Lutz, T.R., and T.R. Stahly. 1998. Dietary riboflavin needs for body maintenance and body protein and fat accretion in pigs. Iowa State University Report, p. 41.
- Mavromichalis, I., et al., 1996. Omitting vitamin and trace mineral premixes, and (or) reducing inorganic phosphorus. Kansas State University Swine Day Report, p. 96.
- Patience, J.F., and D. Gillis. 1996. Impact of preslaughter withdrawal of vitamin supplements on pig performance and meat quality. Prairie Swine Center Inc. Research Report, p. 29.