DSM Corporate | | Print | A A A

Vitamin intake and pork's nutritional quality

While most vitamin research in livestock has concentrated on the animals' health and performance, another important consideration is the nutritional profile of the meat. This profile, along with consumers' general perception of it, is a significant factor in consumer demand, especially with so many other sources of protein vying for the consumer dollar.

Studies continue to show the importance of maintaining sufficient vitamin fortification through finishing to preserve the dense nutritional profile of pork. For example, in one two-part study, Edmonds and Arentson (1999) maintained typical vitamin and trace mineral supplementation levels in the control group of pigs but withdrew supplementation six and 12 weeks before slaughter in two other treatments.

The researchers reported a significant decrease--greater than 75 percent--in the vitamin E content of the loin muscle from animals on the vitamin-deficient diets compared with the meat from the controls. In the second part of the study, using the same feeding regimens, the researchers again found significantly reduced vitamin E content following dietary vitamin withdrawal--in this case in the ham, where concentrations were 50 percent less than in the meat from supplemented control pigs.

The meat in this study was not tested for other vitamin concentrations, but it should be noted that water-soluble vitamins such as the B vitamins are not stored in the body as well as vitamin E and the other fat-soluble vitamins. Thus, decreases in the water-soluble vitamin content of meat could be at least as great with vitamin withdrawal programs. Patience and Gillis (1996) reported a significant reduction (P < 0.05) in the thiamin content in longissimus dorsi muscle following vitamin withdrawal for the final 35 days of finishing. There were also large numerical differences in niacin and pantothenic acid content between treatments.

Similarly, in work with poultry, Deyhim et al. (1996) reported that vitamin withdrawal for 21 days before processing had a marked effect on concentrations of the two B vitamins that were measured--thiamin and riboflavin. In the birds whose diet was vitamin deficient, muscle concentrations were 45 percent lower for thiamin and 31 percent lower for riboflavin than in controls.

Besides changes in the vitamin profile of the meat, researchers have also reported differences in other quality characteristics, such as increased fat content, in finishing pigs that did not receive vitamin fortification at the end of finishing. Mavromichalis et al. (1996) reported a trend toward more backfat (P < 0.06) when vitamins were withdrawn in late finishing (Figure 1). Pigs that continued to receive a full complement of vitamins averaged 0.79 inch of backfat at the 10th rib, compared with 0.85 inch for animals whose vitamins had been withdrawn.

Kim et al. (1996) reported that backfat was 0.15 inch less in pigs that continued to receive vitamin fortification compared to those whose vitamin and trace-mineral premix had been withdrawn. Patience and Gillis (1996) also reported a significant increase in intramuscular fat (P < 0.04) in pigs whose diets were not fortified with vitamins and trace minerals during late finishing (Figure 2). Both studies did not address other important aspects of meat quality, including shrink loss, drip loss, oxidative stability and marketable meat yield.

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.

References:

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.