An estimation of lysine requirements of fattening pigs maintained and raised in Japan

This study aimed to update the first‐liming amino acid (lysine) requirements of fattening pigs maintained and raised in Japan using 146 fattening pigs with an average weight of 62 kg. Five diets were prepared with total lysine concentrations of 0.45%, 0.65%, 0.85%, 0.95%, and 1.05%. Six replicates were used for each lysine concentration. The feeding trial lasted for 4 weeks until the average weight of the pigs reached 92 kg. The total lysine concentration of the diets affected feed efficiency throughout the 4 weeks and was lowest in pigs fed diets with a total lysine concentration of 0.45% and highest in pigs fed 0.85%. The total lysine requirement was estimated using feed efficiency as the response index. The linear and quadratic models estimated 0.68% and 0.75% of the requirement for the first 2 weeks and 0.66% and 0.72% for the 4‐week period, respectively. These estimates were equivalent to the total lysine requirement of 0.72% for the 50–70 kg body weight (expected gain of 850 g/d) in the Japanese Feeding Standard for Swine 2013 and higher than the 0.59% for the 70–115 kg body weight (expected gain of 1000 g/d).