Domain-Dependent Phenotypic Positioning of Liaodan Black Pigs Relative to Liaoning Black and Duroc Populations at a Common Target Body Weight

Relative phenotypic positioning among pig populations may differ across production, carcass, and pork-quality domains. We tested whether source-defined Liaodan Black (LDB) pigs occupied a uniformly intermediate position between Liaoning Black (LB) and Duroc (DR) references at a common target body weight. Sixty pigs (20 per source population; 10 barrows and 10 gilts) entered at 70 d and were slaughtered at 106–114 kg. Population effects were evaluated using a Population × Sex model with false-discovery-rate control for individual fatty acids and amino acids. Sensitivity analyses addressed final body weight, slaughter batch, a shared 50–80 kg interval, intramuscular fat (IMF), fatty-acid compositionality, and principal component analysis (PCA) variable selection. Over 50–80 kg, average daily gain increased and feed-to-gain ratio decreased from LB through LDB to DR (both p < 0.001). LDB had the lowest C18:1n-9c and monounsaturated fatty-acid proportion, while its polyunsaturated fatty-acid profile was closer to DR than LB; these lipid differences persisted after IMF adjustment and centered-log-ratio analysis. Exploratory PCA retained the LB–LDB–DR production/carcass ordering under alternative specifications. Thus, production/carcass ordering did not extend uniformly to intramuscular lipid composition within these sampled source populations.