Challenges in feeding the modern sow
As little as 25 years ago, it was relatively easy to feed replacement females in a commercial piggery. Gilts could be reared to first service on a normal finisher (or baconer) diet and only a single diet was fed to dry sows and lactating sows. Whilst the dry sow diet has not changed dramatically over the last twenty years, rearing the modern gilt and catering for demand on the lactating sow has required development of special feeds for these animals.
The challenge in feeding gilts and sows is largely influenced by genotype of the animals, general environment, management and disease status of the herd under consideration. The nutritionist is required to design feeds that give optimum performance for a given set of these influences and often decisions need to be made on subjective assessments.
Modern gilt rearing (or developer) diets are high in energy (13.5 MJ/kg DE & total lysine: DE of 0.62) with typical digestible lysine values of 6.9 g/kg in diets on an as-fed basis. The ideal amino acid ratios are based on growing pigs and the crude protein of these diets is usually about 180 g/kg.
Most recommendations advocate an ad libitum feeding schedule up to ovulation and subsequent mating, but genotype must be considered when using such a strategy and if gilts become too fat, either a reduction in diet density or physical feed restriction may be necessary.
Years of selection for low fat levels in pigs, improved growth rates and better feed conversion have reduced feed intakes and compromised the breeding ability of sows. However, feeding to maximum protein gain improves ovulation rate in gilts and the suggested optimum criteria for age and body composition at sexual maturity are:
The early developing embryo requires surprisingly low levels of nutrients relative to the sow's requirements for maintenance and growth. A target maternal weight gain of 20 to 25 kilograms during pregnancy for mature sows, and 40 to 50 kilograms in the hyperprolific first parity sow is suggested.
Energy intake during gestation remains the most important nutrient in monitoring maternal weight change. Changes in P2 in response to energy intake are less clear although there is usually an increase in P2 during early to mid-gestation and then a decrease during the final stages of pregnancy. Embryo survival (ES) is a complex phenomenon and the critical time is during the first 21 days of pregnancy. High feed intake (energy levels) during this time can be detrimental to embryo survival and ultimate litter size.
Typical dry sow diets are 13.0 MJ/kg DE, with crude protein of 140 g/kg and a Lysine: DE of 0.5. Depending on environmental temperature and humidity, feeding levels from 2.0 to 2.5 kilograms per sow per day are recommended, and increasing feeding levels 2 to 3 weeks pre-partum may have a positive influence on piglet birth weight.
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Article made possible through the contribution of NRM and Tegel Foods.