Effects of reduced dietary energy and essential amino acid levels on growth and slaughter performance of female Auburn and B.U.T. 6 turkeys in organic farming

This experiment investigated the effects of reducing dietary AME_N and essential amino acids (EAA) levels by 10 % and up to 30 %, respectively, on growth and slaughter performance of female slow-growing Auburn and fast-growing B.U.T. 6 turkeys. A total of 432 day-old hatchlings were raised at two locations over four four-week phases until 16 weeks of age. Animals were allocated to three feeding strategies with graded EAA levels, featuring strongest reductions during rearing and lower reductions during fattening compared to breeding company recommendations. After rearing indoors in poultry houses (week 8), the turkeys were assigned to two housing systems during fattening (weeks 9–16): poultry indoor housing and mobile housing with free-range access.

B.U.T. 6 turkeys exhibited higher final body weights, total concentrate feed intake and consistently lower concentrate feed conversion ratio compared to Auburn turkeys (P ≤ 0.001). B.U.T. 6 birds had higher proportions of dressing, thighs, and drumsticks (P ≤ 0.007), whereas breast meat and abdominal fat proportion did not differ (P ≥ 0.858). When comparing a 30 % with a 20 % EAA reduction during rearing, the stronger reduction decreased final body weights, slaughter weights and dressing percentages (P ≤ 0.048), but not valuable cuts (P ≥ 0.077). However, final body weights of both feeding strategies remained high and matched the breeding company's conventional targets, indicating that both turkey strains can sustain growth potential despite AME_N and EAA restrictions. Housing turkeys with free-range access led to lower final body weights (P < 0.001) with the same total concentrate feed intake (P = 0.831) compared to those kept solely indoors, resulting in a higher feed conversion ratio (P < 0.001). This underscores the challenges associated with environmental conditions, as fattening occurred from October to December. However, free-range access increased breast meat and reduced abdominal fat proportions (P < 0.001), indicating potential benefits.