EFFECT OF SUCCESSIVE LACTATIONS AND NUTRITION ON SELECTED CHEMICAL COMPONENTS OF SOW MILK

The aim of this study was to determine the effect of nutrition and successive lactations on the content of selected chemical components and the fatty acid profile of sow milk. The chemical composition of milk samples collected from 108 PIC sows was evaluated. During the study, sows were allocated to two independent experiments. In Experiment I, sows were divided into three parity groups. In Experiment II, sows were divided into two groups based on the type of concen- trate included in the diet. In both experiments, the content of selected chemical components was determined in sow milk in view of the effect exerted by successive lactations (Experiment I, 54 animals) and nutrition (Experiment II, 54 animals). Milk samples were obtained by hand milking on lactation days 1 and 10, respectively. The samples were subjected to chemical anal- yses to determine their content of dry matter, total protein (Kjeldahl method), crude fat (Soxhlet extraction) and crude ash, and the fatty acid profile. Fat was extracted by the Soxhlet method. Fatty acids were separated and determined by gas chromatography in a gas chromatograph (CP-3800, Varian, Walnut Creek, California, USA). Fatty acid methyl esters (FAMEs) were prepared according to the modified Peisker method (methanol:chloroform:concentrated sulfuric acid, 100:100:1, v/v). Milk collected from sows fed diet 2 was characterized by higher concentrations of monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), unsaturated fatty acids (UFAs), hypocholesterolemic fatty acids (DFAs), n-3 and n-6 fatty acids, compared with milk collected from sows fed diet 1 that contained not only soybean oil but also hardened fish oil. Milk collected during the first and second lactation had higher fat content than milk collected during the third, fourth and subsequent lactations.