Fine-tuning fiber and mineral content in sow diets deserves a second look, say two British specialists.

William Close, formerly with the Agricultural Food and Research Council in the United Kingdom, and Des Cole, formerly of the University of Nottingham, report that minerals may be a “very neglected” component in sow diets. And, they remind, they are very important for sow performance.

Similarly, the solution to a number of sow performance measures is linked to the soluble fiber content of a gestation diet.

The scientists, co-authors of Nutrition of Sows and Boars (published by Nottingham University Press), continue to monitor the latest nutrition research.

Getting Lactation Right

Both agree the key to reproduction is to minimize the loss of body condition during lactation. If successful, the rest of the breeding cycle will be easier to manage.

The modern sow is longer and leaner than ever, they note. She has larger litters of faster-growing pigs, which puts greater demands on her ability to produce adequate milk. She may also have less appetite and less fat reserves than her ancestors, which causes her to lose weight during lactation. Conse-quently, her performance is further challenged.

More feed isn't the only answer, they continue. First, you must find ways to improve her appetite. That's especially important for first-litter gilts entering late gestation, they say.

Typically, sows don't eat enough for one of three reasons:

  1. Genetics. They just don't have the appetite they once did.

  2. Many producers over-feed sows and gilts during pregnancy, which leads to over-fat females at farrowing and reduced appetite during lactation.

  3. High temperatures and humidity often cause sows to lose their appetite. The loss of appetite during lactation depends upon the sow's body weight and the environmental temperature to which they are exposed.

Figure 1 shows the impact environmental temperature can have on voluntary feed intake during lactation.

High Fiber Diets May Help

To offset the genetics issue, Close suggests one solution may be to increase the gut capacity (and appetite) by feeding high levels of soluble fiber in the gestation diet. Not only are the gestation needs of the animal met, feeds with higher water-holding capacity actually make the gut bigger.

Therefore, when the sow starts receiving her lactation diet, she has both the appetite and physical capacity to eat more feed.

The differences in water-holding capacity of different sources of fiber are substantial. See Table 1 for examples.

Maintaining ‘Good Appetites’

Cole and Close offer these suggestions for maintaining a sow's appetite:

  • Be prepared to feed several times a day.

  • Keep the feed supply fresh.

  • Pay attention to appropriate feed particle size and physical form of the diet. In Europe, pelleted diets are more popular.

  • Gradually increase daily feed intake in the first week of lactation.

  • Avoid overfeeding in early lactation.

  • Be prepared for a large sow with a large litter to drink 8-10 gal. of water per day.

  • Maintain sows on the high-intake lactation diet until they return to estrus.

Pay Close Attention to Trace Minerals

Trace minerals have a role in virtually every element of the reproductive cycle, reports Cole. Seven of the main trace minerals in sow and boar rations are selenium (Se), zinc (Zn), copper (Cu), chromium (Cr), iron (Fe), manganese (Mn) and iodine (I). Evidence on iodine requirements is scarce and unsatisfactory, but levels on the order of 0.4 - 0.5 ppm are generally recommended, he says.

Too often, a crushed mineral is simply dumped into the feed mixer according to a well-known formula — and forgotten.

“The source of mineral is very, very important,” Cole says. “In the past, you met the requirements and didn't worry much about the source. Today, it's a question of meeting the requirements, per se, and providing them in a form that's highly available to the animals.”

In the past decade, researchers have begun finding answers to long-neglected questions about the role and value of minerals.

Recent research shows that mineral reserves in sows normally are declining during late gestation and during the lactation cycle.

If the mineral loss can be slowed or stopped, sows maintain good productivity, remain in the herd longer, and tend to be healthier, Cole continues.

The seven trace elements have roles in ovulation rate, embryo survival, uterine capacity, sow fertility and survival of newborn piglets (Figure 2).

And, as an alternative to traditional, inorganic minerals, producers should evaluate the merit in switching to an organic form of trace elements. “As a rule, organic sources are more available than inorganic,” Cole says.

Trace minerals can be attached to a protein and presented with an amino acid or peptide. In this form, an organic mineral is absorbed better — perhaps at a rate that is enough to replace what's being consumed during the reproductive cycle.

For instance, says Cole, “When we attach a trace mineral to a peptide, we create a proteinate. It is more bioavailable and has the ability to target specific tissues or organs.

“When we attach zinc to a peptide with methionine in it, for example, it can target anything with keratin — the hair, the horn, the hoof and the skin. In sows, it can reduce mastitis because it strengthens the internal epithelium of the udder. It also can improve foot strength.”

Also, organic mineral seems to avoid some nutrient conflict issues, he says. In the past, nutritionists would try to increase uptake of one mineral and find that it led to imbalance reactions with other minerals.

Interactions at the sites of absorption are numerous. For example, the one between calcium and zinc is well known. Providing the zinc as a proteinate is a way of avoiding this.

“When you give an organic mineral, because of the way it is absorbed, that doesn't happen,” Cole says. “You get no competition between them. They give a metabolic response that better meets the animal's needs.”

Close reported that nutritionists in Europe, Australia and Asia are seeing good results from organic mineral additions to diet formulations. They're seeing less mastitis, better feet, improved reproductive performance and improved libido.

The two nutrition consultants recommend working with local consultants or feed dealers to apply the research into both minerals and fiber. “They're in the best position to apply knowledge from new research at a farm level,” says Close.

Table 1. Water-holding Capacity (gram/gram) of Different Fiber Sources

Sugar beet feed 7.5
Citrus pulp 6.4
Alfalfa 5.0
Soy hulls 4.7
Wheat bran 3.8
Sunflower seed meal 2.6
Corn gluten feed 2.6
Rice bran 2.1
Oat hulls 1.5
Basal cereal feed 2.0