Genetic advancements have created new challenges in feeding lactating sows.
The major goal for managing nutritional programs for sows in lactation is to maximize milk production without incurring substantial losses in body condition that impair subsequent reproductive performance.
The nutritional demands of the modern lactating sow and litter have changed greatly. Today's genetic advancements provide pigs with faster growth rates, better feed efficiencies and improved leanness.
However, these developments have created new challenges in feeding lactating sows, which generally have lower voluntary feed intake and are leaner with greater body size at maturity.
Likewise, today's piglets have increased growth potential such that even the most productive sows often fail to produce enough milk to meet their requirements for maximizing growth performance. These rapid changes make it important to continuously evaluate and develop sow nutritional programs that account for these changes to maximize both sow reproductive and litter performance.
It is well known that lactating sows need maximum intake of a good quality diet to optimize sow and litter performance. However, too often lactating sows are limited in feed intake, resulting in decreased milk production and excessive sow weight or backfat loss that can hurt future reproductive performance.
Therefore, the three main goals of the sow lactation nutrition program are: 1) maximize intake of a properly formulated diet; 2) match the amino acid and other nutrient levels to the level of feed intake that is achieved; and 3) maintain a reasonable feed cost/weaned pig.
It all begins with the right frame of mind and resolve. Many producers seem to accept that it is “normal” for sows to lose body condition during lactation. However, a number of producers have shown lactation weight loss can be prevented.
Some studies suggest up to 30-35 lb. weight loss won't negatively affect performance. Still, if we adopt the attitude that any amount of weight loss is unacceptable, then there is a greater chance that we will succeed.
Sows have greater capacities to meet their nutritional needs due to their higher feed intake and larger body reserves compared to gilts. More problems are encountered with first- and second-litter sows due to their lower feed intakes, smaller body frames and less fat reserves. These lower reserves produce large gilt body condition losses after farrowing, resulting in lower subsequent litter size and longer wean-to-estrus intervals.
Poor fat reserves at first parity also leads to progressive decreases in body reserves that impact sow longevity.
Gilt pool nutrient management will help prevent this problem. Feed gilts to attain adequate body reserves of lean and fat prior to first mating. Research suggests that gilts should weigh at least 300 lb. and record at least one estrus to provide the body reserves and physiology to optimize lifetime reproductive performance.
Certainly, in addition to an adequate nutrition program, other critical management factors such as boar exposure and proper acclimation are important ingredients for successful gilt integration into the herd and to maximize lactation performance.
Feeding sows for optimum lactation begins at conception, not after parturition. There is a strong, negative relationship between gestation feeding level and lactation feed intake, which is mediated by the female's backfat level at farrowing.
Using the equation, in Table 1, it is predicted that sows with 22 mm. (0.88 in.), 18 mm. (.72 in.) and 14 mm. (.56 in.) of backfat at farrowing will consume an average of 10.4, 11.6 and 12.7 lb. of feed/day during lactation, respectively. So reducing backfat by 4 mm. (0.16 in.) is projected to increase lactation feed intake by about 1 lb./day. Thus, the fatter the sow, the lower her feed consumption during lactation.
Body weight or fatness of each pregnant sow must be managed effectively. Feeding regimens during pregnancy must equally target the demands of lactation as well as the demands for fetal and maternal growth.
Kansas State University nutritionists have developed an objective method of feeding gestating sows based on an estimate of weight and backfat thickness (Table 1). An estimate of weight is obtained by taking a flank-to-flank measurement using a flexible measuring tape to categorize sows into body weight groups. Real-time ultrasound is then used to measure backfat as an objective measure of body condition.
Using these estimates, energy requirements for maintenance, maternal weight gain and fetal gain are converted into daily feed intake nutritional requirements that are easily calculated in a spreadsheet (www.ksuswine.org). This grid can be customized using the spreadsheet to adjust for the total born litter size, environmental temperature and dietary energy density.
Another feature of this spreadsheet is its ability to translate the grid into actual feed box settings. Thus, if the feed box setting is not the same as the weight delivered, farm staff does not need to make the conversions. It is important to periodically update these settings if the bulk density of the diet changes from the addition of different ingredients or changes in the test weight of grain.
The latest challenge we have been addressing is the variability in amount of feed delivered at various feed box settings due to the positioning of the drop and the type of drop.
Based on these studies, we have found that feed drop style definitely influences the accuracy of the amount of feed dropped at various settings. Also, we have found that some designs are more variable due to positioning than others.
Milk production and hence litter growth rates are the main determinants of the nutrient needs of the lactating sow. Milk production represents 70-95% of the requirements for energy and amino acids, and is used as the basis for determining energy and lysine requirements.
To customize lactation diets based on sow productivity, an appropriate dietary lysine level can be calculated if average litter weaning weight and sow feed intake averaged over the entire lactation period are known.
The first step is to get a good estimate of average daily feed intake of lactating sows. For example, over a six-month period, a 3,000-sow farm with 450 farrowing crates farrows 3,615 litters with an average litter weaning weight of 101 lb. at 19 days of age. During this time, 419 tons of lactation feed were delivered to the farm.
Two simple calculations help determine actual lactation feed intake. The first method (above) uses crate days and feed disappearance.
The second method (above) uses number of lactating days and feed disappearance.
The first method should underestimate average lactation feed intake because of days that crates are empty or contain sows that are eating lactation feed but have not farrowed. The second method overestimates lactation feed intake because the feed to prefarrowing sows is counted as feed fed to lactating sows.
The average of these two values should be used as the feed intake estimate. In this example, the daily lactation feed intake should be between 10.2 and 12.2 lb.
Once an accurate estimate of feed intake is determined, the next step is to determine dietary lysine levels. Since milk production accounts for a major portion of the lysine requirement, and litter growth rate is an indirect reflection of milk production, litter weight gain can be used to customize lysine levels based on the level of litter weaning weight.
Sows require about 11.9 grams of lysine per pound of daily litter weight gain plus 2 grams for maintenance; thus, the next step is to determine daily litter weight gain, which can be calculated by dividing litter weaning weight by lactation length.
Based on average daily feed intake and litter weight gain, the dietary lysine level can be customized to accommodate the herd's average milk production. If the previous lactation diet being fed on the farm is higher in lysine than the recommended level, it may be possible to reduce the dietary lysine level without sacrificing performance.
If the previous lysine level being fed is lower or the same as the recommendation, the producer may want to increase the lysine (protein) level and reexamine performance records to determine whether litter weaning weight increases. This relatively simple approach allows the sow lactation diet to be customized to an individual farm.
First-parity sows require special consideration when formulating lactation diets. Usually their feed intake level is about 20% below the herd average. To maintain the same level of litter weaning weight, first-parity sows require about 0.20% higher lysine lactation diet (Table 2).
Also, researchers have demonstrated that first-parity sows require higher lysine levels for maximum reproductive performance than is required for maximal milk production.
Other essential amino acids critical to lactation performance that may become limiting include: isoleucine, methionine, threonine and valine.
More research is needed to determine requirement estimates of these amino acids; however, results to date indicate these amino acids must be carefully considered in diet formulation to prevent costly limitations during lactation.
In practical diet formulation, formulate to meet the lysine requirement of the sow and attempt to maintain high levels of threonine, valine, isoleucine and methionine without incurring excess cost. Typically, these amino acids are formulated in ratios relative to lysine (Table 3). Monitoring these ratios is especially important when using alternative ingredients and synthetic amino acids.
An example of a corn-soybean meal-based formulation for lactating sow diets is provided in Table 4. Additionally, diet formulations with 10, 20 or 30% distiller's dried grains with solubles (DDGS) are included.
With the dramatic increase in ethanol production, DDGS has become more abundant and available for use in swine diets. Data has indicated that DDGS produced from new ethanol plants has approximately the same energy content as corn.
Initially, there was much concern over adding DDGS to lactation diets due to the reductions in palatability when added to finishing pig diets.
However, recent research has failed to indicate a similar reduction in palatability when DDGS is included in lactation diets. Therefore, it appears that high-quality DDGS can be used as an economical ingredient in lactation diets with a substantial reduction in feed cost per ton. Good indicators of high-quality DDGS are greater than 26.5% crude protein, a 2.8 lysine-to-crude protein ratio, 10.5% fat and freedom from mycotoxins.
Adding fat to the lactation diet is an effective means of increasing the fat content of the milk and improving litter weaning weight, but it will not benefit sow reproductive performance. It is important to remember that dietary fat is preferentially used by the mammary gland and results in production of “high fat” milk rather than being used by the sow as an energy source.
Use of high dietary fat levels during lactation will improve litter weaning weights, but may actually impair subsequent reproductive performance by influencing reproductive hormones in early lactation. Therefore, although some added fat (up to 5%) may be beneficial to improving litter performance, high levels of added dietary fat (greater than 5%) should not be used as a remedy for poor lactation feed intake.
Producers should take all steps possible to increase lactation feed intake whether fat is added to the diet or not. Generally, if it is economical to add fat to late nursery diets, it will be economical to use 3-5% fat in the sow lactation diet.
When all sows are housed in the same facility, management must choose either to provide higher amino acid levels than required by the multiparity sows in order to meet requirements of young sows, or formulate closer to the requirements of older sows and not meet the requirements of young sows.
In most situations, the choice is to formulate closer to the requirements of the young sows and oversupply nutrients to the older sows. An advantage of segregated parity flow is that old sows can be fed diets formulated closer to their nutrient requirements in gestation and lactation, resulting in reduced feed cost.
Lactating sows should be full-fed in order to maximize milk production. A lactating sow will normally consume 9 to 15 lb. of feed per day. Intake level will depend on diet composition, sow's body condition, previous gestation feed intake, water availability and environmental temperature of the farrowing facilities. Consider the following procedure to maximize sow feed intake:
Sows are fed 0, 1 or 2-to- 4-lb. scoops at each of three feedings during the day. If there is feed left in the feeder from the previous meal, no feed will be added to the feeder. If a small amount of feed is left, one scoop will be added. If the feeder is empty, two scoops will be fed. Managers may want to consider the extra scoop of feed in the afternoon feeding if feeders are consistently empty in the morning at the next feeding. The only deviation from this pattern is for Day 0 to 2 after farrowing. During this time, the decision is to give 0 or one scoop at each meal to limit over-feeding while milk production is being initiated.
Many farms are implementing mechanized systems that allow for continuous access to lactation feed. One option is to use a beveled PVC pipe clamped within the feeder using U-bolts (Figure 1). The pipe is then attached to a feed line using flexible tubing with an individual shutoff over each feeder. Field observations indicate that average daily feed intake often increases from 1 to 2 lb./day after implementation of these systems.
Suckling piglets have high potential for growth. Studies show that piglets artificially reared can gain at twice the rate of piglets reared by sows. This indicates a large part of piglet biological growth potential remains unachieved in practice, and that increasing the nutrient supply to suckling piglets can further improve birth-to-weaning growth rates.
A reasonable target for preweaning growth rates is 0.62 to 0.66 lb./day to achieve weaning weights of 16-17 lb. at 20 to 22 days of age.
The first and most important option is to improve sow milk output by increasing lactation feed intake of an appropriately formulated lactation diet.
However, milk production becomes limiting at Day 7 to 10 of lactation. This suggests that the difference between the need for nutrients to sustain piglet growth and the nutrient supply increases as lactation proceeds.
Creep feeding, the practice of feeding a solid diet to piglets during lactation, is the most common and easiest way of supplemental feeding of suckling piglets. The usual justifications for creep feeding are:
Provide supplemental milk production, especially to sows nursing large litters;
Prevent preweaning mortality;
Increase weaning weights;
Initiate and promote gut and digestive enzyme development to digest nutrient sources other than sow's milk; and
Reduce severity of postweaning growth reduction and improve postweaning performance.
Some of these benefits have been observed in older weaning ages (4 weeks and over), but little research data indicates benefits of creep feeding to piglets weaned at less than 3 weeks of age. Recently, there has been promising results that may support the value of creep feeding piglets even for 21-day weaning ages.
There are different recommendations on when to initiate creep feeding, but creep feed is often introduced to suckling pigs between 7 to 14 days of age. Daily and total creep feed consumption is highly variable between litters. Also, in our studies, about 75% of the total creep feed intake was consumed in the week prior to weaning (Figure 2).
Contrary to some observations, starting pigs on creep feed when they are older does not have a detrimental effect on the amount of feed the pigs eat. Older pigs seem to accept creep feed more readily than younger pigs, and may actually consume as much or more creep feed overall, compared to pigs started on creep feed at a younger age. It may be more practical to start creep feeding for as little as three to seven days prior to weaning and obtain similar creep feed intake as compared to providing for longer periods prior to weaning.
In recent research, creep feeding in piglets weaned at 21 days of age did not improve weaning weights compared to piglets not provided with creep feed. However, there was evidence that ‘eaters,’ which are piglets that positively consumed creep feed, grew faster after weaning and had higher initial postweaning feed intake than piglets that did not consume creep feed.
Eaters have a shorter time before they begin to consume solid feed after they are weaned than non-eater piglets. Eaters also had higher nutrient absorption rates. This suggests that increasing the proportion of eaters in whole litters may potentially improve postweaning performance. We've studied some of the factors that could encourage more piglets to consume creep feed and become eaters (Table 5).
Restricted feeding of lactating sows did not increase creep feed intake nor the proportion of eaters within litters. This suggests that a limited nutrient supply to piglets through lower milk production fails to promote greater piglet creep feed consumption. Also, this suggests that creep feeding practices are not a substitute for maximizing lactation feed intake.
Creep feeding from 7 days of age (13 days prior to weaning) produced 80% of piglets classified as eaters, compared to about 70% of pigs classified as eaters when provided creep feed at six or two days prior to weaning.
Longer durations of creep feeding did not affect preweaning gain and weaning weights, but did increase the proportion of eaters in whole litters. However, 70% were classified as eaters by providing creep feed for only two days preweaning.
In our experience, a rotary feeder with a hopper is the best type of feeder to use for creep feeding. With this feeder, we were able to significantly increase the number of creep feed eaters compared to conventional bowl feeders and pan feeders (Table 5). The conical shape, curved rim and wings of the feeder with hopper prevented piglets from rooting, standing over or pushing creep feed out of the troughs. It appears that the design of the feeder with the hopper kept pigs from wasting feed, while ensuring that feed was continuously available in the troughs.
The hopper can also be adjusted daily to manage the amount of feed that flowed out of the gap, thus controlling the level of feed in the trough and extending its freshness. This also makes the feeder more practical, because it only requires daily checking of hoppers rather than sprinkling and managing creep feed numerous times in a day.
Finally, changing the taste and aroma of the creep feed also did not increase the proportion of eaters (Table 5). However, there is a trend for improvements in daily gains and an increase in initial feed intake when piglets are exposed to a flavor prior to weaning via the creep feed and fed starter diets that contained the same flavor.
Creep feeds are usually designed to be highly digestible, complex and palatable. This is to match the digestive capacity of these young pigs and to stimulate feed intake. Creep feeds usually contain a high percentage of milk products, processed ingredients and higher levels of amino acids, digestible energy and fat. An example of a highly complex creep diet with the diet specifications is shown in Table 6.
Creep feeds can also come in different forms, usually in meal or mini-pellet form. Extruding, expanding or gels are other forms employed for delivery of creep feed. These processes may help improve the digestibility of the feed or be more easily consumed.
However, there is little scientific data to indicate that one form of creep feed delivery is clearly superior.
Further research is needed to investigate methods by which creep feeding behavior can be encouraged. However, our recommendations when using creep feeding are to use a feeder that minimizes waste and initiates access to creep feed from three to seven days prior to weaning.