The effect of energy density and the lysine to energy ratio of diets on the performance of piglets

Introduction The aim in the feeding of piglets is to realize the maximum growth rates, according to the high growth capacity of these animals. In this respect, the supply of energy and essential amino acids is of particular significance. Among the essential amino acids, lysine, as the first growth‐limiting amino acid, plays a predominate role. In the practical feeding of piglets, the recommendation is to start feeding, after weaning at 4 weeks of age, with a diet containing 13.4–13.8 MJ metabolizable energy (ME) per kg and a lysine concentration of 12.1–12.4 g/kg, which represents a ratio between lysine and energy of 0.9 g/MJ ME. After the initial phase, when the live weight is in the range 20–30 kg, it is recommended that the dietary energy is reduced to 13.0–13.4 MJ ME/kg and the lysine concentration to a range of 10.7–11.0 g/kg (representing a lysine : energy ratio of 0.82 g/MJ ME) (DLG 1996). The present study was carried out to investigate whether this recommended phase‐feeding system allows maximum growth performance in piglets, or whether a constant high energy and lysine concentration during the whole rearing period is superior with regard to growth performance of piglets. Therefore, two experiments were carried out with early‐weaned piglets. The first experiment, using a bifactorial design, investigated the effects of the dietary energy density and the ratio between lysine and energy on the growth performance of piglets at constant levels during the whole phase of 8–30 kg live weight. The second experiment, using a similar experimental design, was conducted to investigate the combined effect between those factors in the second phase, at live weights between 20 and 30 kg.