Importancia de la evaluación del espesor de grasa y de magro dorsal en cerdas hiperprolíficas

In recent years, sows have undergone a great genetic transformation (productive and morphological), which leads to higher nutritional requirements during their productive cycle. The main objective of this study was to improve the knowledge about body reserves (backfat thickness and loin depth) in a commercial farm with hiperprolific sows. On a total of 283 sows of different parities, backfat thickness and loin depth were recorded at the day of insemination, at days 40 and 110 of gestation, and at weaning. Thus, the effect of parity and the effect of lean-to-fat ratio (categorized into three groups according to their 25th and 75th percentiles: Low, Medium and High) on body reserves during the whole period were evaluated; as well as its potential impact on some reproductive parameters. Gilts showed a lower fat deposition than primiparous and multiparous sows, mainly in early gestation; in addition, they had a greater loss of the loin during the lactation and the whole productive period. Regarding to lean-to-fat ratio, gilts with higher vs. lower ratio showed greater losses of backfat and loin depth during lactation. Backfat gain during the productive cycle was lower in primiparous and multiparous sows with the highest ratio; while during mid and late gestation, the loss of loin depth was lower than sows with the lowest ratio. Moreover, the initial values of backfat and loin depth presented a high and moderate positive correlation with their own backfat and loin depth values (during the whole period); however, the cross-correlation between backfat and loin depth was lower or null, highlighting the importance of measuring both. From a reproductive point of view, primiparous and multiparous sows with the highest lean-to-fat ratio showed the highest culling rate. The results underline the need for specific feeding management according to parity (nuliparous vs. primiparous and multiparous). The study also suggests that periodic measurements of backfat and loin depth are a useful tool that allows nutri - tionists to evaluate the feeding plan applied to each farm. Thus, the establishment of recommendations for the lean-to-fat ratio, on the one hand, would provide a more objective unit of measurement on the nutritional status of sows; and, on the other hand, would allow adjusting an adequate nutrient intake at each stage of the productive cycle of hyperprolific lines.