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Effects of repeated short-term Feed-restrictions and LPS induced systemic Inflammation on Metabolism and Performance in Dairy Cows
A negative energy balance (NEB) may occur later in lactation when feed supply and/or quality are insufficient. We investigated if responses of metabolism, performance and immune system to energy deficiency differ between lactational stages. Fourteen multiparous Holstein dairy cows were grouped according to their previous lactation yield in two groups: a control (CON) group and a restricted (RES) group. The trial lasted from wk 3 ap until wk 12 pp. Cows (CON and RES) were fed with grass ad libitum plus additional concentrate throughout the study, except the RES group receiving only grass during 1-wk feed-restrictions in wks 2, 5, 8, and 11 pp. At the end of the first restriction period, LPS from E. coli was infused intravenously (0.5 µg/kg BW) to mimic an inflammatory status interacting with a different metabolic status. DMI and milk yield were recorded daily. Blood was obtained weekly throughout the study, daily during the restriction periods in wks 2, 5, 8, and 11 pp, and every 0.5h during the day of systemic LPS challenge. Blood samples were analyzed for glucose, NEFA, BHBA and IGF-1 concentrations. Data were analyzed using a mixed model including group and wk as fixed effects. During restriction periods, RES had an elevated grass DMI (0.3-4.2 kg/d) compared to CON. In-between restriction periods, DMI did not differ between RES and CON. Milk yield was lower for RES in wks 2, 5, 8 and 11 pp (ca. 5 kg/d) compared to CON and recovered between restriction periods. On the day of LPS challenge, milk yield in RES dropped more distinct than in CON (9.5 vs. 11.3 kg/d). CON cows recovered faster in milk yield after the LPS challenge. During wk 2 pp, plasma concentrations of glucose, NEFA, BHBA were not different between RES and CON, while IGF-1 was lower in RES (41.1 vs. 82.6 ng/mL). During the restriction periods in wks 5, 8 and 11, NEFA and BHBA concentrations were elevated in RES (up to 0.67 mmol/L NEFA and 0.74 mmol/L BHBA), while glucose and IGF-1 concentration were lower in RES compared to CON (3.77 vs. 4.03 mmol/L glucose, 68.8 vs. 98.4 ng/mL IGF-1 in wk 8). In conclusion the experiment showed the changing priority of the lactating mammary gland during different stages of lactation. Performance, metabolic and endocrine changes became less with progress of lactation. Further analyses are in progress.
Keywords:
feed-restriction, metabolism, grass feeding, dairy cow