In many commercial piggeries there is considerable room for improvement with only a small proportion of producers operating at what is classified as a "good" efficiency level. What is becoming increasingly apparent is that the performance at a specific stage of production is influenced not only by the events and inputs at that time but also the accumulated effects of preceding events. In order to achieve and maintain high performance values, a total quality management approach is required. The production process needs to be viewed as an integrated whole rather than a series of piecemeal stages. The 10 week weight should therefore be viewed as an essential performance benchmark of the successful growth performance of the pig. The 10 week performance standards for 1997 are shown in Table 2:

Table 2: Targets for weaned piglets (Gadd, 1997):

Birthweights are positively correlated to survivability and growth rate. Very small piglets (<900grams) grow very slowly and tend to have a very poor feed efficiency. These piglets are not profitable to rear and at best only break even (Gadd, 1996).

It is typical for a modern high producing sow herd to catabolise body reserves during late pregnancy to allow for fetus growth, udder development and to facilitate the birth process. It is therefore recommended that from day 90 of pregnancy the energy level is increased. Birthweight increases progressively as feed intake increases but, provided the mean birthweight is above about 1kg on the largest litters and piglets are viable at birth, the cost of further increasing birthweight is uneconomical.

Piglets live mainly on sows milk before weaning with generally a low consumption of creep feed. Sows milk contains approximately 29% protein, 40% fat, 27% lactose and 4% ash on a dry matter basis. Sixty percent of the energy requirement of the piglet is thus supplied as fat. The fat is provided in a highly emulsified state, and prevented from interfering with other constituents by being encapsulated in a lipo-protein membrane. The apparent digestibility of the fat is about 100%. Having been born with only 1-2% fat the neonate pig grows fat faster than is does protein so that a body lipid content of 15-20% is achieved at weaning. The importance of high milk production by the sow to enable the piglet to deposit adequate fat reserves in its body cannot be overemphasized.

The act of weaning:

The act of weaning has a profound effect on future growth rates. If this is managed badly it has a deleterious effect on lifetime performance. The objective of weaning is to ensure that the transition from sows milk to the post weaning diets is as smooth as possible without compromising growth and without predisposing the piglets to disease.

The body weight at weaning has a very significant influence on the subsequent growth and development of the piglets as shown in Table 3.

Table 3 shows that a 1.76kg difference at weaning became a 5.2kg per pig at 11 weeks of age. The reason for this is that heavier pigs have greater appetites and consume more feed in the post weaning period. It is always advisable to supply special care to the weaker litter mates. This starts at grouping and should encompass the environment and the feed. A smaller piglet has a more underdeveloped digestive system and therefore needs to be fed on a more digestible diet for a longer time period. Smaller piglets will not only grow slower but will also have a higher post weaning mortality. This is shown in table 4 where 450 piglets were weaned at 18 days and subsequently categorized according to weaning weight.

Providing a highly digestible creep feed during the suckling period can help to enhance nutrient intake and hence to improve weaning weight. There are situations where the milk yield of the sow is inadequate and additional nutrients must be provided. The nutrients must be provided in a highly digestible form and this table shows the advantages of providing such a diet. The advantages are not just specific to the suckling period but extend for some considerable time into the post weaning period; in this example to some 7 to 10 weeks of age.

On many farms a low quality creep feed is used. This normally does not stimulate high pre-weaning feed intakes. In order to get the post-weaning benefits from creep feed, the intake should be more than 500 g/piglet before weaning. This consumption of creep will reduce post weaning scouring, reduce the pigs predisposition to disease by making the piglet immunologically more "tolerant" and will enable the pig to perform better. In order to achieve good creep intakes, it is important to use a highly digestible creep. The feed must be fed fresh in a clean trough to make it more attractive and palatable to the piglets.

It is not only the weaning weight, but also the weight gain of the piglets post-weaning, that can influence subsequent performance. 

Table 6 provides additional information of the effects of providing a highly digestible starter diet in the immediate post-weaning period to piglets weaned at three weeks of age. It is important to note the higher rates of gain in the animals given the high digestible starter ration containing 25% milk powder. There was almost 1 kg difference in body weight after three weeks. In addition, the advantage of the extra growth and feed efficiency was carried into the growing and finishing period.

It is therefore important when giving a starter diet to these young piglets, that it is as highly digestible as possible. Providing a less digestible, cheaper ration at this stage will not ensure the best growth of the piglets and may be detrimental. The challenge for the nutritionist is to select raw materials, which will be digested fully by the immature digestive system minimizing digestive upsets. Offering large amounts of nutrients from non-milk sources will result in increases in partially digested unabsorbed feed throughout the digestive tract, which provides the opportunity for detrimental organisms to proliferate and markedly alter the micro-flora of the gut.

Compensatory growth:

If animals are deprived of nutrients and their actual growth is less than the potential, they are often able to catch up by growing faster if their food supply is restored. The animal is compensating for lost growth time. On better farms catch-up growth is rarely required, while in other production systems it may be an important aspect of overall growth to market weight. If growth is arrested very early or very late in development, catch-up growth requires cautious scrutiny. The occurrence of compensatory growth has been debated for many years and recent work from Holland has clarified this topic. Gilts were fed either 2.2 or 3.7 times maintenance from 20 - 45 kg (treatment L and H respectively). Thereafter the pigs were fed ad lib between the weights of 45 - 85 kg with the results shown in table 7 below. The gilts were slaughtered and dissected on reaching 85 kg into organs, lean and fat tissue.

* Weight included the head and feet

The above data shows that following feed restriction from 20 - 45 kg and subsequent ad lib feeding, pigs compensated in terms of average daily gain and feed conversion. The liveweight data therefore supports the view that compensatory growth does occur. However, the above table shows that the liveweight growth compensation was made up of fat in the carcass and greater body organ weights with no compensation in lean meat growth. Pigs on treatment L had furthermore a lower carcass weight when slaughtered at 85 kg. The practical consequence of this is a substantial increase in housing requirements during the rearing period to produce a lighter and fatter carcass.