Reducing Protein Levels in Diets for Local Pig Breeds: A Case Study on Fat-Type Krškopolje Pig

This study investigated the effects of reduced dietary protein levels in fat-type local breed Krškopolje pig in conventional indoor and organic outdoor systems. Two tests were conducted: one in conventional system (n = 28 pigs) and one in organic outdoor system (n = 24 pigs). Two dietary strategies varying in crude protein (CP) level were tested: control, high protein (HP) with phases of 15%, 12.5%, and 10% CP content and low protein (LP) with phases of 15% and 10% CP content. The ingredients used were identical, but in the organic diet, they came from organic agriculture. The feed was offered ad libitum. Feed distribution was recorded, pigs were weighed, and the thickness of the backfat and longissimus lumborum muscle was measured with ultrasound. After 228 days, pigs were slaughtered, and carcass and meat quality were assessed. Modeling growth data with InraPorc indicated that protein and essential amino acid requirements were generally met, except for lysine in the LP diets, which appeared with the transition to a 10% protein diet. Lysine deficiency was more pronounced in the organic than in conventional system. Overall growth rate was similar in LP and HP groups. There were no pertinent differences in carcass or meat quality.