Exploring the Relationship Between the Size and Diverticular Number of Carpal Gland in Four Pig (Sus Scrofa) Populations

The carpal gland is an important exocrine gland in pigs, functioning mainly through diverticula that release strongly odorous secretions. The size of the carpal gland and the number of diverticula may be related to its function. To measure its size, the gland must be dissected from the foreleg, and this procedure is time-consuming and cumbersome. The diverticulum is the outlet of the carpal gland, and its number correlates with the carpal gland size, but the correlation coefficient between them is still unknown. To explore the relationship between the size and diverticular number of the carpal gland, 788 pigs from four populations were used in this study. The length, width, thickness, weight and volume of the carpal gland were measured, together with its diverticular number. The phenotypic correlation coefficient between each pair of the recorded traits was calculated, and a two-factor analysis of variance was used to test whether sex and population have effects on the phenotypes. The carpal gland is a flat small stick with a length of 1.8-8.6 cm, width of 0.6-2.5 cm, and thickness of 0.2-0.8 cm, and its specific gravity is 0.51-1.36. Each carpal gland has 0 to 10 diverticula, and 82.3% carpal glands have 2-6 diverticula. The diverticular number correlates positively with the weight (<i>r</i> = 0.57 and <i>r_s</i> = 0.58, <i>p</i> < 2.2 × 10^-16) and volume (<i>r</i> = 0.55 and <i>r_s</i> = 0.56, <i>p</i> < 2.2 × 10^-16). Population and sex only explain 20% of the phenotypic variance, suggesting that the 80% of carpal gland influences remain unknown. In conclusion, the diverticular number can be used as a proxy for the weightand volume of the carpal gland, because it is easy to count and has a significant positive correlation with the size of thecarpal gland.