Chapter 7
Boars and sows (gilts) make up the breeding herd. These animals are kept to produce pigs for sale or as replacement stock. Care should be taken to properly develop boars and sows to maximize the reproductive efficiency of the herd. One way to accomplish this is through a sound nutritional program that provides the necessary nutrients to meet the needs during different stages of their reproductive life cycle (see page 308).
As Table 7-1 shows, nutrient and energy requirements (reflected by the protein % and ration, lb./day) change throughout the year and are affected by animal's sex, weight, stage of production (e.g., gestation vs. lactation) and season. Therefore, dietary nutrient levels and level of feed intake must change depending on the stage of the life cycle to achieve efficiency. Feed requirements are based on a corn-soybean meal diet that is typically fed to swine with a metabolizable energy (ME) content of about 1500 kcal/lb of feed.
Nutrients and energy are used for maintenance processes as well as growth, lactation, and reproduction. Comparing feed intake (lb/day) of sows during gestating vs. lactating, we find that lactation increases the feed (lb./d) requirement of the sow about three fold . A rule of thumb is to provide about 5 pounds (gestation level) of feed for the sow and 1 pound for each pig she is nursing (e.g., a sow nursing 10 pigs will need about 15 lb. of feed daily).
It is important to maintain sows in good condition throughout the year to avoid to having to feed high levels. It gets expensive to put weight on sows during high nutrient-requirement periods such as lactation. Sow that lose too much weight during lactation may exhibit delayed return to estrus and produce small litters.
Swine eat to meet their caloric needs which are expressed as kcal/day. For example, if a sow requires 6100 kcal of ME/day and the diet contains 1500 kcal ME/lb, eating about 4 lb. (6,100 Mcal/1500 Mcal/lb). If the ME content of the diet to was increase to 1600 kcal/lb then the sow would only need to 3.8 lb (6100/1600) of feed to satisfy her energy needs
Because energy content of the diet can regulate feed intake, it is important that other nutrients (e.g., protein) are maintained at a level based on the energy content of the diet. For example, if the 1500 Mcal./lb diet was balanced to contain 14% CP then eating 4 lb/day of the diet will provide enough protein to meet the sow's daily requirement. Here the sow will be consuming 0.56 lb protein/day (4 lb X 14% protein). However, a 14% CP diet with 1600 kcal/lb of ME will only provide 0.53 lb protein/day because the sow will only eat 3.8 lb. This illustrates the importance maintaining a nutrient:calorie ratio of diets in order that all nutrients are being consumed at adequate levels regardless of the ME content of the diet.
** Be sure to study the lecture notes!!!