Recent studies in mid- and late-lactation dairy cows showed that β-hydroxybutyrate (BHB) infusion had a considerable effect on glucose metabolism and immune response during intramammary lipopolysaccharide challenge. The objective of the present study was to infuse BHB during the dry period and after parturition to investigate the effects of elevated plasma BHB concentrations on metabolism and endocrine changes in transition dairy cows. The hypothesis tested was that regulation of glucose metabolism would change at different physiological stages and an additional elevation of BHB concentration would alter glucose concentration. Multiparous Holstein cows in wk -2 (antepartum, a.p.; n = 6) and wk +2 (postpartum, p.p.; n = 8) relative to calving were infused (4 h from 0800 to 1200 h) with a BHB solution to increase plasma BHB concentration to 1.5 to 2.0 mmol/L (HyperB). The same period the next day without any infusion was considered the control period (CON). Blood samples were taken 1 h before the start of infusion as reference samples and every 30 min during the following 6 h (4 h of infusion and 2 h after infusion) in the HyperB and CON periods, and analyzed for glucose, BHB, insulin, and glucagon concentrations. During the steady state period (the latter 2 h of the 4-h infusion), plasma BHB concentration reached 1.87 ± 0.05 mmol/L (a.p.) and 1.93 ± 0.05 mmol/L (p.p.) in HyperB compared with 0.55 ± 0.06 mmol/L (a.p.) and 0.64 ± 0.04 mmol/L (p.p.) in CON, respectively. The 4-h average BHB infusion rate was 12.4 ± 1.0 and 13.3 ± 0.9 μmol/kg of BW per minute in wk -2 and +2, respectively. Infusion of BHB caused a decrease of plasma glucose concentrations relative to preinfusion levels both before and after parturition, although basal glucose concentrations were different before and after calving. Infusion of BHB increased plasma insulin concentrations a.p. but not p.p., despite a higher basal insulin concentration before than after parturition. These findings show that effects of hyperketonemia on plasma glucose concentrations are similar before and after calving but that endocrine adaptation to hyperketonemia differs before and after parturition. We assume that BHB is a metabolic key regulator in early lactating dairy cows and may affect glucose concentration by further pathways such as gluconeogenesis and altered lipolysis.

Supplementation of dairy cows with trans-10, cis-12 conjugated linoleic acid (CLA) allows nutrient repartitioning despite an energy deficiency in early lactation, which might be a benefit for the immune system, too. In this study, we investigated potential nutrient sparing effects of CLA in early lactating cows with low plasma glucose concentrations exposed to an intramammary lipopolysaccharide (LPS) challenge. Fifteen multiparous Holstein cows were exposed to an intramammary LPS challenge in week 4 p.p. Eight cows (CLA) were supplemented daily with 70 g of lipid-encapsulated CLA (6.8 g trans-10, cis-12 and 6.6 g of the cis-9, trans-11 CLA isomer; CLA) and seven cows with 56 g of control fat (CON). Blood samples were obtained every 30 min along with rectal temperature, heart and respiratory rate, and milk samples were taken hourly until 10 hr after the LPS application. Plasma was analysed for concentrations of glucose, free fatty acids, beta-hydroxybutyrate (BHB), cortisol, insulin and glucagon. In milk, somatic cell count and activity of lactate dehydrogenase were determined. Initial plasma glucose concentration was lower in CLA than in CON. During the immunostimulation, CLA had higher glucose concentrations than CON, and BHB decreased distinctly in CLA, whereas CON cows maintained BHB concentration at a lower level. Body temperature in CLA increased earlier, the difference between peak and basal temperature was higher, and the decline thereafter occurred earlier. In conclusion, CLA supplementation of early lactating cows exposed to an intramammary LPS challenge affected local and systemic immune responses. We assume that CLA supplementation triggered glycogen storage. Cows supplemented with CLA provided more glucose and preferentially used BHB as an energy source during the immune response. The more intense metabolic and more concentrated endocrine responses support an immunomodulatory effect of CLA supplementation.

Supplementing conjugated linoleic acid (CLA) is supposed to spare glucose due to the milk fat-depressing effect of the trans-10, cis-12 CLA isomer, and allows repartitioning nutrients despite an energy deficiency in early lactation. However, there is still a lack of knowledge in terms of the dynamic pattern of the glucose turnover in transition dairy cows. We hypothesized that dairy cows supplemented with CLA have an altered rate of glucose turnover and insulin sensitivity during early lactation. We conducted three consecutive hyperglycaemic clamps (HGC) in weeks -2, +2 and +4 relative to parturition in Holstein cows supplemented daily either with 70 g of lipid-encapsulated CLA (6.8 g trans-10, cis-12 and 6.6 g of the cis-9, trans-11 CLA isomer; CLA; n = 11) or with 56 g of control fat (CON; n = 11). From week -3 up to week +4 relative to parturition, milk yield and dry matter intake (DMI) were recorded daily, while body weight (BW) and milk composition were obtained once weekly. Blood samples were taken once weekly and every 30 min during the HGC. Plasma was analysed for concentrations of glucose, fatty acids (FFA), beta-hydroxybutyrate (BHB), insulin, triglycerides and cholesterol. The CLA supplementation did not affect performance and metabolic parameters except for BHB and cholesterol. Furthermore, insulin concentrations and insulin sensitivity were affected by treatment. During the HGC in early lactation, insulin response was lower and decrease in FFA and BHB greater compared with the HGC in week -2 although glucose target concentration achieved during the steady-state period was similar for all three HGC. Our findings in terms of insulin and cholesterol suggest that body reserves are preserved through CLA feeding without restraining animal's performance. Furthermore, CLA effects on cholesterol and triglyceride concentrations indicated beneficial effects on hepatic lipid export contributing to an improved efficiency of prevailing metabolites in circulation.

Infections of the mammary gland in dairy cows are commonly accompanied by reduced milk production and feed intake and poor milk quality. The metabolic status of early-lactating cows is known to affect immune response to pathogens and imposed immune challenges. We investigated the extent to which metabolic status before an intramammary lipopolysaccharide (LPS) challenge (LPS-CH) is associated with immune response, milk production, and feed intake and the recovery thereof. In 15 Holstein cows, weekly blood sampling and daily recording of dry matter intake, milk yield, milk composition, and body weight (to calculate energy balance) was started immediately after parturition. In wk 4 after parturition, cows underwent an intramammary LPS-CH (50 μg of LPS into 1 quarter). Blood and milk samples were taken in parallel at 30-and 60-min intervals, respectively, until 10 h after the LPS application. Plasma concentrations of glucose, nonesterified fatty acids, β-hydroxybutyrate (BHB), cortisol, and insulin were analyzed. In milk, serum albumin, IgG concentration, somatic cell count (SCC), and lactate dehydrogenase (LDH) activity were determined. Dry matter intake and milk yield were recorded for an additional 6 d. Milk of the LPS-treated quarter was sampled at every milking for 8 d after the challenge. Based on plasma glucose concentrations in wk 1 to 4 after parturition before the LPS-CH, cows were retrospectively grouped into a high-glucose group (HG; 3.34-3.93 mmol/L, n = 7) and a low-glucose group (LG; 2.87-3.31 mmol/L, n = 8). Data were evaluated using mixed models with time, group, and time × group interaction as fixed effects and cow as repeated subject. Glucose was lower and BHB was higher in LG compared with HG before LPS-CH, whereas dry matter intake, energy balance, and SCC did not differ. During LPS-CH, SCC and LDH increased similarly in HG and LG, body temperature increased less in HG, and BHB and nonesterified fatty acids were higher in LG compared with HG. Dry matter intake declined in both groups during the day of the LPS-CH but recovered to prechallenge values faster in HG. Milk yield recovered within 2 d after the LPS-CH with no differences in morning milkings, whereas evening milk yield increased faster in HG. During 8 d after LPS-CH, SCC, LDH, IgG, and serum albumin in milk were lower in HG compared with LG. In conclusion, the level of circulating glucose and BHB concentrations in cows was associated with metabolic responses during an LPS-CH as well as the recovery of udder health and performance thereafter.

Metabolic and health disorders account distinctly for culling in dairy cows. This study investigated if metabolic status obtained once in life during a negative energy balance in early lactation allows to predict age and lifetime performance animals achieved at culling. Metabolically stressed cows entering at least their 3rd lactation (n = 200, parity: 5.0 ± 2.1, mean ± SD) were selected from a field study conducted in Switzerland. Age of cows at culling ranged from 4.7 to 20.2 years with parities from 3 to 17. From cows with known reasons of culling, 28.4% were culled because of fertility, 16.4% due to udder health, 15.5% due to high age and 10.4% because of claw health/lameness. A retrospective classification of the one-time recorded metabolic adaptation in week 4 post partum did not differ between animals of different parities at culling. Furthermore, there was no relationship neither between the metabolic adaptation recorded in a preceding lactation and the number of lactations achieved, nor to the lifetime milk production. Contrary to the wide spread assumptions, an inadequate adaptation due to a high metabolic load in early lactation may not result in an earlier culling of dairy cows, although they are more prone to metabolic disorders.