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Few studies have compared individual variability of an intravenous glucose tolerance test (ivGTT) obtained daily in young cattle. The objective of this study was to evaluate the repeatability of glucose traits and insulin responses derived from ivGTT during 3 consecutive days in Holstein-Friesian cattle (bulls: n = 4, steers: n = 3, heifers: n = 3). Blood collections were performed from min 0 (basal concentrations) to min 63 (last measurement). Additional estimates included maximal concentration for glucose and insulin, glucose half-life time (GHLT), and glucose and insulin area under the curve. Glucose traits showed higher repeatability when compared with insulin responses. On average, the glucose trait and insulin response with the lowest coefficient of variation was GHLT (0.7%) and insulin area under the curve (21.3%), respectively. In addition, a general linear model with repeated measures was used to test for significant differences in glucose and insulin concentrations over time at different trial days. Both glucose and insulin concentrations were influenced by time point but not by trial day or time point × trial day. The results from this study showed that individual insulin responses were more variable than glucose traits. The high repeatability of GHLT evidenced the strict regulatory glucose disposal mechanisms occurring in young Holstein-Friesian cattle, whereas insulin responses showed high variability despite controlled management and nutritional practices., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Glucose metabolism in dairy and beef cattle has received considerable attention because balanced blood glucose is essential for numerous processes, such as milk production and general health. The glucose tolerance test measures the ability of an organism to regulate blood glucose levels. Glucose half-life time (GHLT) has high heritability and could serve as a potential parameter to breed for metabolic resistance. However, studies focusing on identification of an adequate glucose dose have not yet been conducted in cattle. The objective of this study was to analyze the effect of 5 different glucose doses (0.5, 1, 1.5, 2, and 3 g/kg of body weight 0.75 ) on intravenous glucose tolerance test (ivGTT) traits and insulin responses in nongestating heifers. A total of 150 tests were performed in 30 Holstein-Friesian heifers aged 13 to 15 mo. Blood samples were obtained every 7 min after glucose injection until min 63. Glucose traits and insulin parameters included blood serum glucose and insulin concentration at min 0 (basal concentration), min 7 to 21 (peak glucose and insulin concentration), and min 63 (last sampling) relative to glucose administration, glucose and insulin area under the curve (GAUC and IAUC), and GHLT estimated between min 14 and 42. Serum glucose and insulin concentrations were measured according to the hexokinase colorimetric method and radioimmunoassay, respectively. Generalized linear mixed model was used to test for significant differences in ivGTT traits, insulin responses, and glucose elimination rates (k) over time at different glucose doses. Maximum glucose and insulin concentrations at min 63 increased with higher glucose doses. Significantly lower GHLT were obtained at increasing glucose doses, whereas GAUC and IAUC were significantly higher at increasing doses. The k values were affected by glucose dose and by time interval. Glucose dose greatly affected most ivGTT traits, insulin responses, and glucose elimination rates. Therefore, researchers should standardize their methods to achieve repeatable results and use the same time points for GHLT calculation. Higher glucose doses (≥1.5 g/kg of body weight 0.75 ) triggered glucose concentrations above the glucose renal threshold during the initial 42 min, whereas the lowest glucose concentration failed to induce a maximum insulin response. Further research is necessary to determine an adequate dose inducing maximum insulin responses with minimum renal glucose losses., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Glucose is essential for numerous cellular functions due to its involvement in energy supply from early development to adulthood. In the lactating cow, glucose demands by the mammary gland significantly increase to support milk production when compared with other tissues. Thus, insufficient blood glucose levels might predispose dairy cows to metabolic disturbances. The intravenous glucose tolerance test (ivGTT) is a suitable tool to characterize glucose metabolism and insulin responses, but results must be reliable and repeatable. One factor influencing ivGTT is food deprivation period, which has been considered as an obligatory requirement before conduction of glucose tolerance studies in monogastric species, whereas it has been permissive in ruminants. The objective of this study was to determine the influence of 5 fasting periods (0, 12, 24, 36, and 48 h) on ivGTT traits and insulin responses in German Holstein heifers. A total of 140 tests were conducted in 28 females aged 12 to 19 mo. Blood samples were collected every 7 min within 1 h. Assessed glucose and insulin parameters included basal serum glucose and insulin concentration, maximum glucose and insulin concentration obtained between min 7 to 21, and concentrations at min 63 (last sampling) relative to glucose administration, glucose area equivalent (GA), glucose area under the curve (GAUC), insulin area equivalent (InsA), insulin area under the curve (InsAUC), and blood glucose half-life time (GHLT). Serum glucose and insulin concentration were measured according to the hexokinase colorimetric method and solid phase radio immunoassay, respectively. The generalized linear mixed model was used to test for significant differences in all glucose traits and insulin responses at different fasting periods. The model used season and weight as confounding variables. Glucose and insulin concentrations at 0, 7 to 21 (maximum concentration), and 63 min were affected by the duration of food deprivation. The GA, InsA, GAUC, InsAUC, and especially GHLT were also affected by fasting period. A positive linear relationship between GHLT and length of food deprivation was found. Significantly higher GA, GAUC, GHLT values, and glucose and insulin concentration at min 63 were obtained at increasing fasting periods. High intraclass correlation coefficient (0.48) was found for GHLT. The results demonstrate that GHLT might be used to reliably characterize an individual's glucose metabolism and the importance of standardizing food deprivation schedules when performing an ivGTT in nongestating Holstein heifers., (Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Mastitis is one of the most common diseases in dairy production, and homeopathic remedies have been used increasingly in recent years to treat it. Clinical trials evaluating homeopathy have often been criticized for their inadequate scientific approach. The objective of this triple-blind, randomized controlled trial was to assess the efficacy of homeopathic treatment in bovine clinical mastitis. The study was conducted on a conventionally managed dairy farm between June 2013 and May 2014. Dairy cows with acute mastitis were randomly allocated to homeopathy (n = 70) or placebo (n = 92), for a total of 162 animals. The homeopathic treatment was selected based on clinical symptoms but most commonly consisted of a combination of nosodes with Streptococcinum, Staphylococcinum, Pyrogenium, and Escherichia coli at a potency of 200c. Treatment was administered to cows in the homeopathy group at least once per day for an average of 5 d. The cows in the placebo group were treated similarly, using a placebo preparation instead (lactose globules without active ingredients). If necessary, we also used allopathic drugs (e.g., antibiotics, udder creams, and anti-inflammatory drugs) in both groups. We recorded data relating to the clinical signs of mastitis, treatment, time to recovery, milk yield, somatic cell count at first milk recording after mastitis, and culling. We observed cows for up to 200 d after clinical recovery. Base-level data did not differ between the homeopathy and placebo groups. Mastitis lasted for an average of 6 d in both groups. We observed no significant differences in time to recovery, somatic cell count, risk of clinical cure within 14 d after disease occurrence, mastitis recurrence risk, or culling risk. The results indicated no additional effect of homeopathic treatment compared with placebo. The advantages or disadvantages of homeopathy should be carefully assessed for individual farms., (Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Selection for improved health and welfare in farm animals is of increasing interest worldwide. Peripartum energy balance is a key factor for pathogenesis of diseases in dairy cows. The intravenous glucose tolerance test (ivGTT) can be used to study the metabolic response to a glucose stimulus. The aim of this study was to estimate heritability of ivGTT traits in German Holstein bulls. A total of 541 Holstein bulls aged 7 to 17 mo from 2 breeding stations were subjected to the ivGTT. Serum glucose concentrations were measured at 0, 7, 14, 21, 28, 35, 42, 49, 56, and 63 min relative to glucose infusion. The maximum increase in blood glucose concentration, glucose area equivalent, and blood glucose half-life period were calculated. Heritabilities were estimated using a univariate animal model including station-year-season and age as fixed effects, and animal additive genetic and residual as random effects. The estimated heritabilities were 0.19 for fasting glucose concentration, 0.43 for glucose area equivalent, 0.40 for glucose half-life period, 0.14 for the peak glucose concentration, and 0.12 for the maximum increase of blood glucose concentration. Correlations between ivGTT traits and breeding values for milk yield and composition were not found. The results indicate that heritability for response to glucose is high, which warrants further investigation of this trait for genetic improvement of metabolic disorders. Research is necessary to determine the target levels of ivGTT traits and potential associations between ivGTT traits in breeding bulls and periparturient diseases in their offspring., (Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

This study was conducted to investigate hormonal imbalances preceding stillbirths and dystocia in primiparous heifers. The study was conducted between 2003 and 2004 on a German dairy farm, including 433 heifers. Starting 3 wk before calving, a weekly blood sample was collected. At calving, another blood sample was obtained, and the calving ease (grade 0 = unassisted to grade 2 = heavy pull with mechanical calf puller), sex, birth weight, as well as vitality status (stillborn, alive) of the calf were recorded. The blood serum was analyzed for estradiol-17beta and progesterone concentration. At parturition, the measured estradiol-17beta concentration was greater in heifers delivering bulls than in those with female calves and was increasing with greater birth weight of the calf and increasing calving difficulty score. Already 2 wk before calving, the serum estradiol-17beta concentration was significantly smaller in heifers with stillborn than live calves. On the other hand, the progesterone concentration was greater 2 wk before calving in heifers with stillborn calves, but it was unaffected by the birth weight or sex of the calf or the calving difficulty score. Stillborn and live calves did not differ in birth weight or pregnancy duration. The smaller estradiol-17beta concentrations of the heifers with stillborn calves could indicate an abnormality of the placenta or an abnormality of hormonal signals from the calf to the placenta in the weeks before the calving.