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Objective: Clinical ketosis is common during the dairy cows' transition period and is responsible for considerable economic loss. Early identification of cows with subclinical ketosis is the first step for maintaining the health and productivity of dairy cows. The goals of the study were two-fold: The first was to examine the usefulness of a mobile test device as a cow-side test; and the second was to compare BHB concentrations measured by the ketometer using capillary blood and blood collected from the coccygeal vessels with values determined by a reference method in the laboratory using jugular blood., Material and Methods: Blood samples were collected from a jugular vein or the coccygeal vessels in 81 dairy cows at 7 time points (14 and 7 days pre-partum and 7, 14, 21, 28, and 42 days post-partum) for kinetic enzymatic measurement of BHB concentration in the laboratory. Blood samples were concurrently collected from the coccygeal vessels or by pricking the vulvar lip at the transition of the skin to the mucosa (capillary blood) to determine BHB concentration using the WellionVet BELUA ketometer (MED TRUST GmbH, Marz, Austria)., Results: Initial errors in operating the ketometer were quickly eliminated with experience. BHB concentrations of jugular blood measured in the laboratory were 0.07 mmol/l lower than those measured in coccygeal blood. The mean BHB concentration measured in coccygeal and capillary blood using the WellionVet BELUA ketometer did not significantly differ but were 0.13 and 0.12 mmol/l respectively, lower than the mean jugular vein concentrations measured in the laboratory., Conclusion: The WellionVet BELUA ketometer is useful for determination of BHB concentration in cows provided that the manufacturer's specifications are followed. Capillary blood is best collected at the transition from the vulvar skin to its mucosa. The device generates rapid results that correlate well with BHB concentrations determined in the laboratory and with the results obtained from different blood collection sites. It is ideally suited for monitoring dairy cows for subclinical ketosis using capillary or coccygeal blood., Competing Interests: Die Autoren bestätigen, dass kein Interessenkonflikt besteht., (Thieme. All rights reserved.)

In spring, transition from a total mixed ration (TMR) to a full grazing ration with moderate concentrate supply influences cow's metabolism. It has been shown that feeding moderate amounts of concentrate during fulltime grazing did not prevent energy shortage and lipomobilization, alterations in energy metabolism, decreasing milk production and loss in body weight. As diet change and energy balance are closely related to immune reactivity, in this trial the effect of transition to pasture on specific immune parameters of cows was documented. Over a 12-week trial 43 dairy cows were observed during transition from confinement to pasture (PG; n = 22) and compared to cows fed TMR indoor (CG; n = 21). The CG stayed on a TMR based ration (35% corn silage, 35% grass silage, 30% concentrate; dry matter (DM) basis), whereas the PG slowly switched to a pasture -based ration (week 0 and 1 = TMR, week 2 = TMR and 3 h pasture·day -1 , week 3 and 4 = TMR and 12 h pasture·day -1 , and week 5 to 11 = pasture combined with 4.5 kg DM concentrate·cow -1 ·day -1 ). Inflammatory markers like blood haptoglobin or tryptophan to kynurenine ratio did not indicate acute phase reaction. Proportions of CD4 + (T-helper cells) and CD8 + cells (cytotoxic T-cells) remained uninfluenced as well. White blood cell concentration and its subpopulation of granulocytes increased over time in the PG. Stimulation ability of peripheral blood mononuclear cells to mount an oxidative burst significantly increased during the trial, too. The endogenous antioxidant state as characterized by glutathione peroxidase (GPx) and superoxide dismutase (SOD) activity in blood of the PG did not change, whereas the vitamin E concentration reached the highest level at the end of the trial. The 25-CHO metabolites of vitamin D increased as soon as the PG had pasture access, whereas the other metabolite 25-ERG decreased. The results of this study indicate that transition to pasture affects immune related parameters. However, the consequences of the observed effects on health status of the pasture group need to be clarified in further studies with a defined concurrent immune challenge.

In spring, transition from a total mixed ration (TMR) to pasture requires rumen adaptions for the cow. It had been shown that transition period does not necessarily mean an increased risk for subacute ruminal acidosis (SARA). After adaption to pasture, however, supplying low amounts of concentrate did indicate increased risk, but caused no adverse effects on rumen morphology and absorption capacity. The present study aimed to investigate the effect of transition, and how a supply of 4.5 kg dry matter concentrate·cow -1 · day -1 during fulltime grazing influenced different rumen parameters. During a 12-week trial eleven rumen-cannulated dairy cows were observed during transition from confinement to pasture (PG; n = 6) and compared to cows fed TMR indoors (CG; n = 5). The CG stayed on a TMR based ration (35% corn silage, 35% grass silage, 30% concentrate; dry matter basis), whereas the PG slowly switched to a pasture-based ration (week 0 and 1 = TMR, week 2 = TMR and 3 h pasture·day -1 , week 3 and 4 = TMR and 12 h pasture·day -1 , and week 5 to 11 = pasture combined with 4.5 kg DM concentrate · cow -1 ·day -1 ). Papillae surface area decreased during transition and increased again during fulltime grazing, while the fractional absorption rate of volatile fatty acids (VFA) was not influenced. This suggests only a limited effect of papillae surface area on VFA absorption rate. Feeding changes resulted in different fermentation profiles of VFA. Changing ratio of starch to sugar during transition to fulltime grazing plus concentrate supply did not lead to lower rumen pH. In conclusion, the concentrate supply combined with high fermentable grass during fulltime grazing increased papillae surface area but did not affect absorption rate or rumen pH, so that risk for SARA was not increased.

In spring, the transition from a total mixed ration (TMR) to pasture requires metabolic adaptions for the cow. It had been shown that supply of low amounts of concentrate after transition to full-time grazing caused energy deficits, resulting in a lower milking performance and changes in a variety of variables indicative for energy metabolism. The present study aimed to investigate how a moderate concentrate supply (4.5 kg dry matter cow/day) after transition to pasture influences health and production indicators. Over a 12-week trial period dairy cows were observed during transition from confinement to pasture (pasture group: PG) and compared to cows fed TMR indoors (confinement group: CG). On average, the PG consumed less feed and energy than the CG and mobilized body reserves, which is mirrored in a decrease of body condition and various fat depots. These effects were paralleled by elevated serum concentrations of non-esterified fatty acids and ketone bodies as well as an increase in liver fat content. The physical activity (elevated walking, eating, decreasing rumination time) of the PG was significantly higher than that of the CG, which intensified the energy deficiency and resulted in a lower milk yield. In conclusion, the moderate concentrate supply was insufficient to counterbalance the lower energy intake from pasture during transition.

In spring dairy cows are often gradually transitioned from a silage- and concentrate-based ration (total mixed ration, TMR) to pasture. Rumen microbiota adaptability is a key feature of ruminant survival strategy. However, only little is known on the temporal and spatial microbial alterations involved. This study aims to investigate how the rumen liquid (LAAB), particle (PAAB), and epithelium (EAAB) associated archaea and bacteria are influenced by this nutritional change. A 10-wk trial was performed, including 10 rumen-fistulated dairy cows, equally divided into a pasture- and a confinement- group (PG and CG). The CG stayed on a TMR-based ration, while the PG was gradually transitioned from TMR to pasture (wk 1: TMR-only, wk 2: 3 h/day on pasture, wk 3 & 4: 12 h/day on pasture, wk 5-10: pasture-only). In wk 1, wk 5, and wk 10 samples of solid and liquid rumen contents, and papillae biopsies were collected. The DNA was isolated, and PCR-SSCP and 16S rRNA gene amplicon sequencing analysis were performed. Cluster analysis revealed a higher similarity between LAAB and PAAB, compared to the EAAB, characterized by higher species diversity. At all three locations the microbiota was significantly influenced by the ration change, opposite the generally acknowledged hypothesis that the EAAB remain more consistent throughout dietary changes. Even though the animals in the PG were already on a full-grazing ration for 4-6 days in wk 5, the microbiota at all three locations was significantly different compared to wk 10, suggesting an adaptation period of several days to weeks. This is in line with observations made on animal level, showing a required time for adaptation of 2-3 weeks for production and metabolic variables. A large part of the rumen prokaryote species remained unaltered upon transition to pasture and exhibited a strong host influence, supporting the hypothesis that the rumen microbiota consists of a core and a variable microbiota. For the effect of the location as well as the ration change either very similar or opposite trends among member species of common taxa were observed, demonstrating that microbes that are phylogenetically close may still exhibit substantially different phenotypes and functions.