Nutrition and feeding management of pigs in wean-to-finish (W-F) systems have received little attention in trade publications and research programs. Generally, producers have adapted nursery feeding strategies for pigs early in the W-F cycle and finishing feeding strategies for pigs late in the W-F cycle.

The concepts involved in developing a sound nutritional program and delivering it effectively and efficiently are similar for both W-F and traditional, nursery/finish production systems. However, there are subtle but important differences, particularly in feeding management, that need to be taken into account in order to maximize profitability.

First, the nutritional needs of the animals during each phase of production must be determined. Second, diets must be formulated to meet those nutritional needs at the lowest possible cost. Third, feeding management must allow the delivery of the feed to the animals in a manner that maximizes production performance and minimizes waste.

Determining Nutritional Needs There is no published evidence that nutrient needs of newly weaned pigs in W-F systems are different than those of pigs weaned to a traditional nursery. Pre-starter and starter diets that work well in a nursery should also work well in W-F facilities. There is evidence, however, that early mortality rates are lower in W-F systems than in nurseries, suggesting that pigs in W-F facilities are healthier. The literature contains compelling evidence that the nutrient and ingredient needs of weaned pigs are affected by the level of immune activation. If weaned pigs in a W-F system have a lower level of immune activation relative to contemporary pigs in a nursery, it may be possible to feed less complex, cheaper nursery diets without having a negative impact on growth.

A logical approach to fine-tuning nutritional accuracy and reducing feed cost of newly weaned pigs in a W-F system is to start with a proven starter program. The next step is to systematically reduce the nutritional complexity of the diets by formulating lower levels of plasma, milk products and highly digestible protein sources, and higher levels of corn and soybean meal, while monitoring animal performance. Producers who don't have the ability to alter diet composition can conduct a similar analysis by altering the amount of each diet fed and monitoring performance. It may be possible to make diet changes earlier in W-F systems, feeding less of the more expensive diets, without reducing performance.

Our experience has shown that pigs in a W-F system will reach market weight 7-10 days faster than similar pigs in a traditional nursery/finish system, with similar carcass composition at slaughter. This suggests that the shape and/or slope of the lean growth curve is different for W-F than for nursery/finish systems. Figure 1 shows the shape of a typical lean growth curve for W-F vs. a typical lean growth curve for nursery/finish. It is clear that the main difference in these two growth curves occurs during the accelerating phase of lean growth, from 40-100 lb. The reason for the differences in the shapes of the lean growth curves for the two systems hasn't been determined.

However, one can postulate that space limitations late in the nursery, and stress caused by transportation and acclimation to new facility and social environments, cause a deviation in the normal growth curve for pigs in nursery/finish systems. Since pigs in the W-F system experience little stress, their lean growth curve doesn't dip in the 40- to 100-lb. phase.

Feed intake pattern is also different for W-F than nursery/finish during this 40- to 100-lb. phase, with pigs in W-F consuming more feed. Producers with both W-F and nursery/finish systems, or those contemplating switching from nursery/finish to W-F, need to develop lean growth and feed intake curves for both systems to accurately determine nutrient needs.

Determining the nutritional needs of W-F pigs over 100 lb. is similar to determining the nutritional needs of pigs in a traditional finishing system. Nutrient needs are determined by assessing feed intake and the lean growth potential of both barrows and gilts during each phase of production. National Hog Farmer Blueprint Series No. 27, Understanding Lean Growth, Oct. 15, 1998, covers in detail the process of establishing lean growth curves, feed intake curves and using this information to develop a feeding program.

Diet Formulation Diet formulation involves taking the nutrient requirements (and ingredient requirements for pigs from weaning to 30 lb.), the available ingredients and their costs, and using a least-cost formulation program to develop diets that meet or exceed requirements at lowest cost. This process is similar for W-F and nursery/finish systems.

However, as mentioned above, nutrient and ingredient needs of pigs in W-F systems may be different than those of pigs in nursery/finish systems, resulting in the need to formulate diets specific to each production system.

Feeding Management Proper feeding management is critical to top W-F performance. In addition, feeding management is substantially different for W-F and traditional nursery/finish systems.

Select a feeder for W-F that allows ready access for weaned pigs and sufficient head space for large finishing hogs. The ideal W-F feeder is a dry feeder with solid dividers. Trough lip height should be low, no more than 4.5 in. high, so that small pigs can easily access the feed. If a feeder without solid dividers is used, it's important to use feeder inserts that prevent pigs from lying in and getting stuck in the feeders.

Wet-dry feeders aren't recommended but can be used with the water shut off to the feeder and another source of water. If the water to the feeder is not disconnected, feed spoilage will occur during the first few weeks when feed intake is low. Pre-starter spoilage is both costly and detrimental to feed intake. Water to the wet-dry feeders can be reconnected when the pigs exceed 30 lb.

Tube feeders aren't ideal for W-F use but can also be made to work. One disadvantage is difficulty in filling them by hand, a common process in W-F feeding management.

Water intake is critical to early feed intake. Cup waterers, particularly those with a drip screw, work best for W-F because there is residual water in the cup to attract pigs to water. If nipple waterers are used, allow them to drip for the first few days to attract pigs to water. Failure to do so can result in increased levels of navel sucking and fall-behind pigs. Install a nipple that can be operated by small pigs. Don't use finishing nipples for small pigs. It may restrict access to water, reducing performance. Provide one water cup per 15 pigs. Place waterers close to feeders.

Ideally, W-F barns will be set up with two feed storage and handling systems. One system can be a conventional bin, auger system common to finishing barns. This system should be designed for separate sex feeding. The second system consists of a smaller bin for pre-starter feed. Without a separate feed system for pre-starter, it's necessary to handle pre-starter in bags to ensure that the proper amount of fresh feed is fed to each pen of pigs and that there is no contamination with finishing feed from the previous group. Store bagged feed in a clean, dry area.

Hand feeding newly weaned pigs on a feed mat is an important way to maximize feed intake and early growth performance and reduce the number of fall-behind pigs. Pigs should be fed at least four times per day on feed mats until they are eating well, which typically occurs at 7-10 days postweaning. Allow 30 sq. in. of mat space per pig. Mats should be rubber or plastic with a lip height of at least 1/2 in. to reduce feed wastage. Avoid using plywood because it's difficult to clean thoroughly. Rubber mats are preferred because they stay in place better than plastic mats. Place mats near the feeders and within the zone heating areas.

Multiple feedings of small quantities is recommended to keep the feed fresh. A good rule of thumb is to provide one-half the pig's daily intake on the mats, keeping the pigs just hungry enough to seek out feed from the feeders. Weaned pigs will typically eat 0.5-0.6 lb./day. Six feedings of 0.05 lb./pig spread throughout the day will meet the objectives of encouraging feed intake and teaching the pigs to seek out, and eat from, the feeders.

Consistent, accurate feeding is most easily done using a scoop that delivers the right quantity of feed based on the number of pigs in the pen. Feed fines and rejected feed should be dumped off the mats before adding more feed. When pigs start to mess the mats repeatedly, remove them from the pens.

Managing 'At-Risk' Pigs It seems that every group of weaned pigs contains "at-risk" animals. That category includes early weaned pigs, pigs with low weaning weights, fall-behind pigs and pigs showing signs of disease. At-risk pigs need to be housed in the warmest section of the barn, near the center on the south side. They shouldn't share a feeder with pigs that aren't at risk because their feed changes need to be staged differently than other pigs in the barn.

Besides mat feeding, at-risk pigs do best if they are gruel-fed. Often, producers are tempted to treat at-risk pigs, when what they really need is nutrition. Gruel feeding is the most effective method of encouraging small, at-risk pigs to consume feed. Gruel (Figure 2) should be mixed fresh for each feeding and fed at least three times per day for the first 5-7 days postweaning. Provide just enough gruel that it can be consumed in no more than 15 minutes. Continue mat feeding while the pigs are being gruel fed.

One technique that works well is to gruel feed first thing in the morning, at noon and last thing in the day, with two to four mat feedings interspersed between gruel feedings. Reduce the quantity of feed put on the mats when gruel feeding to prevent feed waste.

Also, at-risk pigs need to stay on pre-starter 7-10 days longer than normal pigs. Save 4-5 lb. per pig in bags or the cart bin to feed to the at- risk pigs after the other pigs have switched from pre-starter to the first starter feed. When subsequent feed changes are made, filling the feeders of at-risk and fall-behind groups prior to delivery of the new feed will allow these groups to stay on the more nutrient-dense diets longer. This technique can help prevent the small pigs in each group from falling further behind the rest of the group.

Feed Budgeting The feed budgeting process for W-F systems is akin to standard nursery/finish systems. Figure 3 shows an example of a W-F feed budget. The budget should contain eight diets, four diets from weaning to 50 lb. and four diets from 50 lb. to market. Many producers use 10- to 12-step feeding programs in W-F systems in an effort to fine-tune output and reduce cost.

Regardless of the number of diets used, the feed budgeting process is an important step in making sure the right feed is in front of the pigs at all times. Preferably, feed budgets should be based on the quantity of each feed delivered, but can alternatively be based on days on each diet. Separate feed budgets should be developed for barrows and gilts.

Feed bin management takes on added importance in W-F systems. Between groups, it's critical all finishing feed from the previous group has been removed from the bin and that any mold or feed buildup is cleaned out prior to the delivery of starter feeds. Power washing the bin with hot water followed by disinfectant and adequate downtime for complete drying is recommended. In cold climates, all bins should be thoroughly cleaned prior to freeze up.

When changing from one diet to the next, bin inventories must be drawn down before adding the next feed in the sequence to ensure the right feed is in front of the pigs at all times. In addition, bins should be completely emptied at least once a month. This step is key to preventing the contamination of late finishing feed with nursery feed that potentially contains medications with extended withdrawals.

Split-sex feeding has been shown to improve performance and reduce cost in finishing pigs and now is a routine practice in most operations. It's equally important in W-F systems. At arrival, gilts and barrows should be penned and fed by separate feeding systems.

Invariably, there are either more gilts than barrows or more barrows than gilts. If there are more gilts than barrows, the largest gilts should be penned with the barrows. Conversely, if there are more barrows than gilts, the smallest barrows should be penned with the gilts. This method allows all pigs to receive diets that most closely match their nutritional needs.

Conclusions W-F is an exciting new production scheme. An integral part is learning how to properly feed these pigs. Much is known, but we need to learn more about the lean growth patterns of W-F pigs and their resulting nutrient needs.