Introduction

Early weaning has become a popular practice in the swine industry over the last few years. Nutritionally, weaning pigs at 5 to 21 days of age is challenging. It requires the correct levels of nutrients, high quality ingredients, and intensive management. The benefits, however, are a healthy, fast growing pig and increased economic return.

The Sow Versus the Nutritionist

The transition of piglets at weaning from a liquid milk diet to a solid feed is dramatic and can result in low intake and poor growth post-weaning. The digestive tract has been accustomed to milk and as a result is still relatively immature. It has the capability of digesting components of milk, such as milk fat, protein, and lactose, very well. However, the digestibility of nutrients from plant sources and other ingredients used in baby pig diets is low at the time of weaning. As the pig consumes more feed, the levels of digestive enzymes responsible for the breakdown of starches, proteins, and fats increase. Therefore, getting the pig to consume feed quickly is extremely important in getting off to a good start.

A comparison between the nutrient composition of sows milk and a common early weaning ration is presented in Table 1. The main difference between the two sources is the level of fat, and therefore the level of energy the pig has available for growth. This high level of fat, physically cannot be attained in a practical pig ration. In addition, fat in sow milk is very well digested by the pig compared to fat sources added to nursery diets (particularly animal fats).

Digestive Problems

Table 2 shows some of the enzymes that are involved in the digestive process.

The capacity of the pig to secrete these enzymes varies with age and can be dramatically reduced following weaning (Figure 1). Another study (Makkink et al., 1994) showed that enzyme development was related to feed intake and that greater intakes resulted in greater enzyme activities. This observation is in agreement with the results reported by Lindemann et al. (1986), who found that enzyme activity increased throughout nursing, abruptly decreased at weaning (when feed intake was low), and increased again following the post-weaning lag (Figure 1).

Whittemore (1993) reported that voluntary feed intake may be limited by the digestibility of the diet. He estimated that voluntary feed intake is influenced by live weight and diet digestibility as follows: 0.013 * Live Weight, in kg/(1 – Digestibility). Voluntary feed intakes of 0.52, 0.65, and 0.86 lbs per day can be calculated when using digestibility coefficients of 0.75, 0.80, and 0.85, respectively, when this equation is applied to an early weaned pig (use 10 lbs (4.5 kg) for example) . This example demonstrates the large potential effect of diet digestibility on feed intake and therefore ultimately growth rate. For reasons discussed in this section, the use of highly digestible ingredients is an essential component of a successful early weaning program.

Ingredients in Early Weaning Diets

Ingredients commonly used in early weaning diets are shown in Table 3. There are many more ingredients entering the market that can be used in early weaning diets. All ingredients listed in this table are highly digestible and palatable. Typically early weaning diets will contain carbohydrate sources to provide 20 to 25% lactose, have a limited amount of soybean meal as a protein source, and contain varying levels of fishmeal (3 to 8%), plasma proteins (3 to 8%) and synthetic amino acids to provide the remaining protein in the diet. In addition, plasma protein is included because it has been reported to stimulate feed intake in young, weaned pigs. Generally, an early weaning diet will contain approximately 1.6 to 1.8% lysine. Most early weaning diets are supplemented with copper sulfate (200 to 240 ppm of copper) and zinc oxide (1500 to 3000 ppm of zinc) for their growth promoting and antibacterial properties.

Diet Form

Pelleting diets for early weaned pigs will improve the digestibility of the diet and limit feed wastage. Smaller pellets may be more suitable for young pigs, as they are easier to eat. An English study reported a 5% improvement in feed intake when the pellet size was decreased from 2.4 mm to 2.0 mm. Pellet quality is also important. A hard pellet may decrease feed intake, whereas a pellet that is too soft may fall apart and increase the levels of fines, which can also reduce feed intake and increase wastage. Teeth clipping of the newborn pig may influence feed intake in early weaning programs. A study from the National Committee of Pig Breeding, Health and Production (1994) reported substantial differences in problems with teeth depending on methods of clipping and on farm to farm variation. Although this research did not report feed intake patterns following weaning, it appears reasonable to assume that tooth health could have an impact on feed intake.

How to Feed

While on the sow, a pig may suckle 16 to 20 times per day as a group. Two things can be learned from this fact: 1) pigs are social in their feeding behavior. Therefore, feeder space in the nursery needs to be available so pigs can eat as a group. 2) Pigs are accustomed to eat frequently and therefore, feeding small amounts throughout the day can stimulate feed intake. In ad libitum feeding situations this may not seem important, but getting the pig curious and motivated to eat may stimulate intake and consequently pig growth.

In the nursery, pigs are fed according to a phase feeding program that may consist of 2 to 5 phases. Diet transition from one diet to the next will occur at a certain weight or age or a combination of the two, according to their nutrient requirements. The first diet is going to be the most complex and the most expensive, but it will help to get the pigs onto feed quickly which will pay off in improved subsequent performance. Feeding each diet for the "average" pig will result in underfeeding the lighter pig and overfeeding the heavier pig. Therefore, the lightest pig should be allowed to consume more of this diet than the heavier pigs because their nutritional needs are higher. The heavier pigs can be switched to the next diet phase quicker. When switching diets, a smooth transition from one feed to the next is most desirable. Mixing some of the first diet with the next diet in the feeder is an easy way to slowly adapt the pig to the next phase. The goal of the phase feeding program is to match diet composition with the nutritional needs of the pig at the lowest cost.

Cost Calculations

Several endpoints can be used to evaluate the success of an early weaning program. Performance measurements such as average daily gain, feed intake and feed efficiency are a good initial gauge, but they do not take diet cost into consideration. Two other calculations that are often used are feed cost per pound of gain and net value of gain (value of gain minus cost of feed). The latter may be the most appropriate, because it is an indication of gross profits after the nursery phase.

Take-Home Message