Swine Nutrition Guide: Breeding Herd Management

Practical Applications and Outcomes.
The recommendations and concepts presented in this publication are intended to help pork producers apply appropriate nutrition-based technologies. These technologies are designed so that nutrition does not limit production potential and profitability in most situations. However, pigs must be capable of responding to improved nutrition. Weaknesses in the operation such as crowding, poor sanitation, inadequate ventilation, chronic disease, and lack of proper temperature control will limit the response to nutrition. Optimum nutrition can not substitute for good management practices but must be used to complement good management.

Breeding Herd Management -- A "limit-feeding" program is recommended for developing gilts after they reach about 230 lb and for gestating females and breeding boars. However, a "limit-feeding" program should limit only energy and not the intake of other nutrients, such as amino acids, minerals and vitamins.

Energy intake is limited to keep animals from becoming too fat. Excessive feeding of breeding animals leads to increased feed cost and interferes with reproduction and longevity. Sows that are overfed immediately after breeding and throughout gestation often suffer high embryonic mortality, and thus produce smaller litters than sows fed proper amounts. Sows that have become too fat tend to have more farrowing difficulties, crush more pigs and eat poorly during lactation.

This is especially true during the summer when sows are subject to heat stress. The dietary nutrient recommendations for developing gilts, gestating females and breeding boars shown in Table 14 assume that they are fed 6, 4 and 5.5 lb of feed daily, respectively.

When daily feed intake is adjusted, it is important that the concentrations of amino acids, minerals, and vitamins in the diet be adjusted accordingly. Aim to provide a constant daily intake of amino acids, minerals, and vitamins regardless of feed intake.

How much feed should gestating sows and developing gilts receive?
During mild weather (spring/ fall) about 6 to 6.5 Mcal of ME per animal per day (4 to 4.5 lb of a corn or milo-soybean diet) will keep 350-- to 400-lb gestating sows in "good" condition. However, energy intake will need to be decreased or increased depending on the condition and weight of the sow and environmental conditions. See Table 18 for approximate energy and feed needs of gestating sows according to their body weight. Sows (350 to 400 lb) housed outside during the winter should receive about 7.5 to 9.0 Mcal of ME/ day (5 to 6 lb of a corn or milosoybean meal diet). Developing gilts should be restricted to about 90% of ad libitum feed intake or about 6 lb/ day from about 230 lb until 2 weeks before mating.

How can limit-feeding of sows be accomplished?
The success of limit-feeding sows and gilts depends on controlling the intake of each animal. Care must be taken to see that each receives her share. Individual sow feeding stalls are effective devices for controlling boss sows. Interval feeding is another practical method for limiting the feed intake of sows during pregnancy. With interval feeding sows are allowed to consume two or three days worth of feed in one day and then wait two or three days before being provided access to feed again. Adjustments in daily intake are made by altering either the time on the feeder (2 to 12 hours) or time off the feeder (2 or 3 days). For example, two hours out of 72 is an adequate feeding time if enough feeder space is provided so all sows can eat at one time. With time on the feeders restricted, one feeder hole per sow is essential. More total feed is required during gestation when sows are interval-fed, because feed efficiency is reduced. For gilts every-third-day feeding is not recommended, because they gain less weight and farrow smaller pigs than gilts fed once daily. Gilts are not as able as sows to consume large quantities of feed in short time intervals.

What about flushing?
Litter size in limit-fed gilts can be increased by increasing their feed intake or allowing ad libitum access to feed beginning 11 to 14 days before mating. This is called "flushing." Higher energy intake during this time will maximize the number of eggs released by the ovaries. Reduce feed intake to about 4 to 4.5 lb/day when mating occurs. Overfeeding during early gestation may increase embryonic mortality and reduce litter size.

Should feed intake be increased during late gestation?
The majority of fetal development occurs during the last 2 to 3 weeks of gestation. Research indicates that giving sows 2 to 3 lb more feed per day during the last 2 to 3 weeks of gestation can slightly improve the number of pigs weaned per litter. Do not give extra feed to fat sows during late gestation, or they probably will have poor feed intakes during lactation.

How should lactating sows be fed?
Sows should be full-fed during lactation to obtain maximum milk production, minimize weight loss and improve rebreeding performance. Many sows perform best when they are allowed to consume all the feed they can beginning the day they farrow. Severe feed restriction after farrowing predisposes sows to constipation and delayed return to estrus. It is easier for some people, however, to detect lactational problems in sows if they are offered limited amounts of feed during the first 3 days after farrowing. If limit feeding is practiced, provide at least 3 lb of feed the day of farrowing and increase the offering 3 lb/day thereafter. By day four post farrowing, the sow should be given ad libitum (free choice) access to feed. Record the amount of feed added to the sow's feeder daily, especially if more than one person is feeding the sows.

How about feeding after weaning?
After weaning, feeding rate will depend on how adequately the female was fed during lactation and her body condition. Generally, 4 to 4.5 lb/day of a corn or milosoybean meal diet is adequate. Provide 5 or more pounds of feed/day to thin sows. Do not withhold feed from sows after weaning, because it reduces subsequent litter size.

How should developing and breeding boars be fed?
Guidelines for feeding developing boars are shown in Table 15. When the boars weigh about 230 lb they should begin to receive restricted quantities of feed to avoid excessive weight gain. Offer the boars about 5 to 5.5 lb of a corn or milo-soybean meal diet/day (about 7.5 Mcal of ME/day). The diet should contain nutrient levels similar to those for developing gilts shown in Table 14. When boars are between about 1 year and 2 years of age, we suggest they be fed to gain about .4 to .55 lb/day (145 to 200 lb/year). To accomplish this and maintain fertility, feed breeding boars a different diet than the one used for gestating females. The goal is to restrict energy intake to slow growth rate, but to maintain high amino acid, vitamin and mineral intakes to preserve fertility and libido. Weigh boars periodically to determine the appropriate feeding rate for specific conditions. Table 18 gives approximate energy and feeding rates to allow boars to gain about .4 to .55 lb/day. Boars > 2 years of age should be fed to gain at a slower rate, because they are nearing their mature body size. As with sows, the daily feeding rate must be changed to reflect differences due to housing temperature and body condition of the boar.

What role does fiber or nonstarch polysaccharides have in sow diets?
Plant-based feed ingredients contain fiber or nonstarch polysaccharides (NSP) which cannot be digested by pigs. Instead NSP are fermented by microorganisms in the large intestine. The most abundant NSP in plants include cellulose, hemicelluloses and pectins. Gestating sows are excellent candidates to receive high NSP-containing diets. Limit-fed gestating sows obtain more energy from fibrous feedstuffs than growing pigs do and they have a higher fermentation capacity in the hindgut. In addition, sows can consume more of a concentrate diet than necessary to meet their energy requirement during gestation. This excess feed intake capacity can be exploited by including low-energy, bulky feeds in the diets of gestating sows. Litter size weaned may be improved by about .5 pigs/litter when NSP is added to the sow diet during gestation. In addition, NSP in the sow diet may improve sow longevity in the herd. To maximize the chance of an improvement in sow reproductive performance from increased NSP intake, it seems sows should consume 350 to 400 g/d of neutral detergent fiber (NDF) during gestation. Diets containing 45% wheat midds, 20% soybean hulls, 25% alfalfa meal, 30% sugar beet pulp, or 40% oats provide sows about 350 g/d of NDF. There is no strong evidence that increasing the NSP level in the lactation diet improves sow reproductive performance. Fibrous ingredients in the lactation diet may help control constipation, however (see the next question). Bulky diets containing a high level of NSP results in a sow that is more "satisfied" after consuming a meal than one fed typical corn or milo-soybean meal-based diets. The same situation has been observed with breeding boars. Consider that the costs associated with manure handling may increase due to the larger volume of solids produced when high NSP diets are fed.

Can sow constipation be controlled by feeding a specific feed ingredient?
Maybe. Results with laxatives are variable. Most of the published research indicates that laxatives do not improve sow reproductive performance. Often sows are constipated because they are not given enough feed during the first few days after farrowing. If sows are constipated, try offering them more feed after farrowing before adding a laxative to the diet. Also, check that the sows have an ample supply of water. Fibrous feedstuffs or certain chemicals may serve as laxatives. Fibrous feedstuffs such as beet pulp, alfalfa, oats, pysillium, soybean hulls and wheat bran have a high water binding capacity and can act as a laxative. Chemical laxatives include potassium chloride (15 lb/ton), Epsom salts (30 lb/ton), and Glauber salts (60 lb/ton). These inclusion rates are recommended when sows are fed 4 to 4.5 lb of feed/day. The level can be cut in half when sows are full-fed. Natural laxative feedstuffs are preferred because mineral salts may alter water balance in the body and irritate the digestive system. Limit the amount of beet pulp, alfalfa, oats and wheat bran in the diet according to guidelines in Table 1 to avoid reducing the energy density of the diet too much.

How does fat affect breeding herd performance?
Feeding fat to sows during late gestation may improve pig preweaning survival rate by 2 to 3%. The greatest response to dietary fat is achieved in herds in which pig preweaning survival rate is less than 80%. For best results, sows should consume at least 2.5 lb of added fat before farrowing to improve pig survival rate. Feeding a lactation diet with 3% added fat at the rate of 6 lb/day for 14 days before farrowing would be sufficient. Sow feed intake usually decreases when fat is added to the lactation diet; however, energy intake may be increased slightly, especially during hot weather. A greater increase in energy intake is likely during hot weather when sows are drip-cooled. Much of this additional energy consumed by sows fed fat-supplemented diets is made available to the litter via the milk. Consequently, added fat may increase litter gain but does little to reduce sow weight loss during lactation.

How can developing or replacement gilts be fed to reduce the number of "downer sows"?
The dietary calcium and phosphorus levels we recommend for growing-finishing pigs shown in Table 11 support excellent rates of gain and feed efficiency, but are not sufficient to build the skeletal structure and mineral reserves needed by developing gilts to reduce "downer sow" problems. The dietary phosphorus level necessary to achieve maximum growth and feed efficiency is at least .1% less than that needed to achieve maximum bone mineralization. Thus, we recommend that developing gilts from 45 to 230 lb be fed diets containing the levels of calcium and phosphorus shown in Table 15. Dietary calcium and phosphorus recommendations for gilts after they are placed on a limit-feeding program at about 230 lb are shown in Table 14.

Will higher dietary levels of calcium, phosphorus, and other nutrients improve feet and leg soundness?
Probably not, although proper nutrition is clearly important in maintaining feet and leg soundness. Many research studies have investigated the influence of nutrition on feet and leg soundness. As long as the diets contained nutrient densities similar to the recommendations in this publication, no relationship between nutrition and feet and leg soundness was found. In other words, if pigs are fed according to the guidelines in this publication, any feet and leg soundness problems encountered likely are caused by genetic or environmental factors other than nutrition.

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