RESUMEN
The dairy industry contributes significantly to anthropogenic methane emissions, which have an impact on global warming. This study aimed to investigate the effects of a dietary inclusion of brown seaweed Ascophyllum nodosum on enteric methane emissions (EMEs), hematological and blood biochemical profiles, and milk composition in dairy cows. Eighteen Holstein cows were divided into three groups: CON (non-supplemented cows), BS50 (50 mL of 10% A. nodosum), and BS100 (100 mL of 10% A. nodosum). In each cow, measurements of EME, dry matter intake (DMI), and milk yield (MY), as well as blood and milk sampling with respective analyzes, were performed before supplementation (P1), after 15 (P2) days, and after 30 (P3) days of supplementation. A. nodosum reduced (p < 0.05) methane production, methane yield, and methane intensity in both BS50 and BS100, and raised DMI (p < 0.05) only in BS50. Total bilirubin (p < 0.05) was higher in BS50 compared to CON cows in P2, and triacylglycerols were lower (p < 0.05) in BS50 than in CON cows in P3. Higher milk fat content was found in BS50 than in CON cows in P3. C16:0 proportions were higher (p < 0.05) in BS50 and BS100 than in CON cows, while C18:3n-3 was higher (p < 0.05) in BS100 than in BS50 and CON cows in P3. Dietary treatment with A. nodosum reduced EMEs and showed the potential to increase DMI and to improve energy status as well as milk composition in peak-lactating dairy cows.
RESUMEN
This study examines the effect of season-related heat stress in dams on mineral status, and hematological profile of their calves. Ten Holstein dams (LowT group) were exposed to the 49-day-long period of low air temperature (5.2 ± 0.5 °C) and ten dams (HighT group) were exposed to a 53-day-long high air temperature (27.4 ± 0.4 °C). The dams' blood samples were taken one hour after parturition, while colostrum was sampled at 2, 14, and 26 h after calving. Ca, P, Mg, Na, K, Fe, Zn, Mn, and Se concentrations were significantly lower while Cu and Co concentrations were significantly higher at least in two examined colostrum sampling points in HighT group. Calf`s blood samples were taken before 1st colostrum intake, and on days 1, 2, 3, and 7 postnatal. Ca, P, Na, K, Fe, Cu, Zn, Mn, Se, and Co were significantly lower while concentration of Mg was significantly higher in calves that originated from HighT group at least at two examined sampling points. Season affected dam's blood mineral status but the pattern was not always the same as in calves, since Na, K, Cu, and Co were significantly higher in HighT group. Calves that originated from HighT group had significantly lower hemoglobin, hematocrit, MCV, MCH, and MPV values, as well as neutrophils and monocyte counts, while platelets, eosinophils, basophils, and lymphocyte counts were significantly higher. Season-related heat stress leads to a reduction of the most minerals in both dams' colostrum and calves' blood and certain minerals' deficiencies are linked to impaired calves' hematological adaptation.