Effects of Extruded Linseed and Soybean Dietary Supplementation on Lactation Performance, First-Service Conception Rate, and Mastitis Incidence in Holstein Dairy Cows

Simple Summary Natural and processed fat supplements directly affect milk yield and composition in cows. Oilseed extrusion is a heat-treatment process used for seeds fed to ruminants to prevent rumen biohydrogenation of unsaturated fatty acids. This process increases postruminal fat absorption when compared with the effects of feeding whole oilseeds. Hence, we investigated the effects of feeding a mixture of extruded linseed and soybean on lactation performance, first service conception rate, and mastitis incidence in Holstein dairy cows. We found that supplementing dairy cow feed with a mixture of extruded linseed and soybean at a rate of 100 g/kg feed increased milk yield and both monounsaturated and polyunsaturated fatty acid content. However, incidences of clinical mastitis and first-service conception rates were not affected by extruded linseed and soybean supplementation. Abstract This study quantifies the effects of extruded linseed and soybean (ELS) dietary supplementation on milk yield, composition, and fatty acid profiles, as well as first-service conception rate in Holstein dairy cows. Seventy-eight open Holstein dairy cows were divided into two groups: (1) a control, which received a basal diet; and (2) a test group, which received a basal diet supplemented with the ELS (650 g/kg of extruded linseed and 150 g/kg of extruded soybean) at a rate of 100 g/kg. In the ELS group, milk yield per day and solid not fat (SNF) yield increased by 3.26% and 0.88%, respectively, in relation to the control. Percentage milk fat decreased significantly by 1.4% in the ELS group when compared with the control. The ELS supplement resulted in a decrease in saturated fatty acids (SFAs) and an increase in monounsaturated (MUFAs) and polyunsaturated fatty acids (PUFAs) in milk. In conclusion, the supplementation of dairy cow feed with 100 g/kg of ELS increases milk yield and milk unsaturated fatty acids (especially MUFAs and PUFAs). ELS supplementation also causes a decrease in percentage fat and SFA levels but does not affect the first-service conception rate or the incidence rate of mastitis.