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Folic acid, vitamin A, and riboflavin: trio may help boost litter size

Folic acid

It was long assumed that swine didn't need supplemental folic acid because it is readily available through many feedstuffs and intestinal microbial synthesis. However, current research suggests that supplemental folic acid may be needed for optimum reproductive performance of sows.

In 11 trials conducted by five Southeastern universities, sows fed supplemental folic acid consistently showed greater litter size than unsupplemented sows (Lindemann, 1993). The reason seems to be greater embryonic or fetal survival rather than increased ovulation, but the exact mechanism has not been determined.

These studies suggest that sows with higher ovulation rates, and, therefore, higher potential for embryonic mortality, seem to benefit most from folic acid supplementation. These include sows from breeds that ovulate more, sows or gilts that have been flushed, and older sows. Lindemann and Kornegay (1989) reported that multiparous sows showed a greater response than gilts or second-parity sows (Figure 1).

Based on these studies and since folic acid is a water-soluble vitamin with limited body storage, it is recommended that folic acid be added to sow diets during the entire gestation and lactation period. Supplementation during breeding could help reduce embryonic death loss during early gestation. The NRC recommended level is 0.3 ppm of folic acid in the feed. But folic acid is one of the less stable vitamins and is affected by light, ultraviolet radiation and oxidizing and reducing agents. It has been reported that 43 percent of the folic acid in a premix was lost during storage of three months. It may be necessary to nearly double the amount of folic acid added to a premix, especially if it will be stored for several months.

Folic Acid, Vitamin A and Riboflavin

Are all found in the ovaries and uterus. Not surprisingly, they affect conception rates and litter size to some degree.

Vitamin A

Vitamin A is essential for reproduction, mainly through the maintenance and development of epithelial and other body tissues. It is also involved in the secretion of specific uterine proteins necessary to maintain pregnancy.

Research at universities and commercial units indicates that sows may need supplemental vitamin A at levels above NRC requirements for optimum reproductive performance. Sows receiving one million IU of vitamin A, injected intramuscularly at weaning, averaged up to half a pig more in the subsequent litter than unsupplemented sows.

In studies at a commercial operation in Texas, sows that previously had small litters showed a greater response to vitamin A injections than sows that normally had larger litters. Older sows, with a greater number of parities, also showed a greater response to vitamin A injections than younger sows.

In a Washington State University study (Brief and Chew, 1985), sows injected with vitamin A and (or) beta-carotene had less embryonic mortality and more live pigs per litter at birth and weaning, as well as heavier litter weights at weaning than controls (Figures 2 and3). The treatments in this study were as follows:

Deficient: fed 2,100 IU vitamin A per head daily in ration.
Pooled data from animals fed 12,300 IU vitamin A and (or) 32.6 mg beta-carotene per head daily in ration.
Pooled data from animals injected with 12,300 IU vitamin A and (or) 32.6 mg beta-carotene per head daily intramuscularly.

A study at North Carolina State University (Coffey et al., 1989) reviewed beta-carotene needs in multiparous sows, which were injected once at weaning with 0, 50, 100, or 200 mg of beta-carotene. The researchers reported a linear increase in litter size at birth with an increased level of beta-carotene. Also, the treated sows had fewer pigs born dead. But first-litter gilts that received a similar beta-carotene treatment showed no effect on litter size or pigs born alive.

Even though beta-carotene is best known as a precursor of vitamin A, it may have an independent role in reproduction as well. Research to date has not determined the mechanism.

The choice between vitamin A and beta-carotene is subject to debate. Dr. Boon Chew, Washington State University, notes that while beta-carotene appears to be more effective in some studies, vitamin A costs less.

Rovimix® AD3 500/100 Facilitates Vitamin A and D3 Fortification of Diet

Vitamin product forms with the right physical and chemical characteristics ensure that animals will receive the dietary fortification levels needed for the nutritional benefits of the vitamins. Recently developed Rovimix AD3 500/100 stabilized gelatin beadlets make it easy to add vitamins A and D3 to feeds. The 5:1 ratio of vitamins A:D3 closely approximates the ratios of the fortification levels of these vitamins added to feeds. Rovimix AD3 500/100 has good chemical and position stability, bioavailability and mixability.