The impact of herd structure on the performance of commercial sow-breeding farms

Background The herd structure, i.e., distribution of sows within a farm based on their parity number, and its management are essential to optimise farm reproductive efficiency. The objective of this study is to define different types of herd structure using data from 623 Spanish commercial sow farms. Additionally, this study aims to determine which type of herd structure can enhance reproductive efficiency at the farm level. Results Farms are classified into three groups according to the quadratic function fitted to the percentage of sows over parities. This classification unveils three types of herd structures: type 1 (HS1) exhibits a concave-downward trend, with a higher percentage of sows in intermediate parities (mean of 45.5% sows between the 3rd to 5th parity); type 2 (HS2) presents a trend curve that is close to a straight line, with a gradual decrease in the percentage of sows per parity (approximately 2% loss of sows census per parity); and type 3 (HS3) shows an upward concave trend curve, with an increase in the percentage of sows in later parities (19.0% of sows between 7th and ≥ 8th parity). Additionally, parametric tests (ANOVA followed by the Tukey HSD test) assess productivity differences between the three groups of farms with different herd structures. Significant differences (p < 0.01) are noted in number of piglets weaned per sow per year, farrowing rate, percentage of sows returning to oestrus and number of weaned piglets, with a medium effect size (values of η ² between 0.06 to < 0.14). Farms with HS1 (showing a concave-downward trend) have the best productive outcomes over a year, surpassing the results of farms with HS2 and even more so those of HS3 farms. Conclusions This study shows the importance of herd structure on sow-breeding farms as factor of reproductive efficiency. The results endorse the proposed classification based on the curvature of the trend parabola obtained with the quadratic function to categorize herd structures into three groups. Besides that, these highlight the importance of considering the herd structure in farm decision-making.