Classifying Genetic Lines in Pork Production by Ileal Crude Protein and Amino Acid Digestibility in Growing Pigs

SIMPLE SUMMARY: Breeding programs in pigs have been very successful in recent decades, although the different selection directions have resulted in highly variable growth rates between the genotypes. Simultaneously, the absorption of nutrients may also show differences subject to the genotype of the animals. As far as the development of the feeding strategies is concerned, the main objective is to maximize profitability; therefore, future methods in swine nutrition must also support the different growth rates of the animals through the improved absorption of nutrients. One of the most common tools used to reduce feed costs is the optimization of the dietary lysine-to-energy ratio, because lysine is the first limiting amino acid for swine, and energy content is one of the most defining parameters of their diet. Pigs of different genetic potential can be classified with a high accuracy in respect of their crude protein and amino acid digestive capacity. Consequently, the ileal digestibility of crude protein and amino acids in growing pigs of different genotypes should serve as a basis for the development of genotype-specific feeding strategies. Further studies are needed to identify the differences in the crude protein and amino acid digestibility of cross-bred pigs with different genetic potentials. ABSTRACT: The first aim of the study was to evaluate the effect of different dietary lysine (LYS) to energy (DE) ratios on the apparent ileal digestibility (AID) of crude protein (CP) and selected amino acids (AA) in growing pigs (40–60 kg) of different genotypes. The second aim was to classify genotypes into groups based on the AID of CP and AAs. The trials were conducted on a total of 90 cross-bred barrows (30 animals/genotype) in two replicates. Before the trial series, the experimental animals (average initial body weight (BW) = 40.9 ± 8.5 kg) were surgically fitted with post valve T-cannula (PVTC). The diets were formulated with six different total LYS/DE ratios. Titanium dioxide (TiO(2)) was added to the diets (5 g/kg) as an indigestible marker. Based on our results, it can be concluded that the LYS/DE ratio of the diets affected the AID of the CP and AA in different ways by each genotype (p < 0.05). It can also be concluded that pigs of different genetic potential can be classified with a high accuracy (91.7%) in respect of their CP and AA digestive capacity. Our results indicate the development of genetic-profile-based swine nutrition technologies as a future direction.