Serum fructosamine levels in dairy cows related to metabolic status in early lactation

Methylglyoxal: A newly detected and potentially harmful metabolite in the blood of ketotic dairy cows

Ketosis causes serious economic losses for the modern dairy industry because it is a highly prevalent metabolic disease among cows in high-producing herds during the transition period. Due to some striking similarities between diabetes in humans and ketosis in dairy cows, there is potential for the use of methylglyoxal (MGO)-commonly used in human diabetics-as a biomarker in dairy cattle. However, currently no data are available about the presence of MGO in the serum of dairy cattle or about the characteristics of its production or its potential contribution in the pathogenesis of ketosis. To determine the potential origin and pathway of formation of MGO, cows in different metabolic conditions [i.e., non-subclinically ketotic dairy cows in early lactation (n = 7), subclinically ketotic dairy cows in early lactation (n = 8), overconditioned dry cows (BCS >4.25, n = 6), and nonlactating heifers (n = 6)] were selected. Serum MGO concentrations were determined and correlated with indicators of the glucose and lipid metabolism and with haptoglobin (Hp) as an inflammatory marker. The serum MGO concentrations in subclinically ketotic cows (712.60 ± 278.77 nmol/L) were significantly greater than in nonlactating heifers (113.35 ± 38.90 nmol/L), overconditioned dry cows (259.71 ± 117.97 nmol/L), and non-subclinically ketotic cows (347.83 ± 63.56 nmol/L). In serum of lactating cows, concentrations of glucose and fructosamine were lower than in heifers and were negatively correlated with MGO concentrations. Even so, concentrations of metabolic and inflammatory markers such as dihydroxyacetone phosphate, nonesterified fatty acids, β-hydroxybutyrate, acetone, and Hp were remarkably higher in subclinically ketotic cows compared with nonlactating heifers; these metabolites were also positively correlated with MGO. In human diabetics elevated MGO concentrations are stated to originate from both hyperglycemia and the enhanced lipid metabolism, whereas higher MGO concentrations in subclinically ketotic cows were not associated with hyperglycemia. Therefore, our data suggest MGO in dairy cows to be a metabolite produced from the metabolization of acetone within the lipid metabolization pathway and from the metabolization of dihydroxyacetone phosphate. Furthermore, the highly positive correlation between MGO and Hp suggests that this reactive compound might be involved in the proinflammatory state of subclinical ketosis in dairy cows. However, more research is needed to determine the potential use of MGO as a biomarker for metabolic failure in dairy cows.

Clinical Utility of Plasma Fructosamine Concentration as a Hypoglycemic Biomarker during Early Lactation in Dairy Cattle

Background

Plasma fructosamine concentration ([FRA]) is a widely used long term hyperglycemic biomarker in humans and dogs, but its clinical usefulness as a hypoglycemic biomarker in dairy cattle is uncertain.

Objectives

To evaluate the relationship between plasma [FRA] and glucose concentration ([gluc]) as well as indices of energy balance during early lactation in dairy cattle, and to characterize the influence of plasma total protein concentration ([TP]) and albumin concentration ([albumin]) on [FRA].

Animals

Convenience sample comprising 103 periparturient Holstein–Friesian cattle.

Methods

Plasma [gluc], [TP], [albumin], and other clinicopathologic indices of energy status were determined periodically from Day 4 postpartum. Body condition score (BCS) was assessed, and backfat thickness (BFT) and longissimus dorsi muscle thickness (LDT) were measured ultrasonographically. Plasma [FRA] was measured at approximately 28 days postpartum. Associations between plasma [FRA] and study variables were evaluated using Spearman's rho and stepwise forward linear regression. Statistical significance was declared at P < 0.05.

Results

A positive association was detected between plasma [FRA] and mean plasma [gluc] from Days 4–28 postpartum (r_s = +0.36, P < 0.001), and between plasma [FRA] and LDT (r_s = +0.28, P = 0.007), BCS (r_s = +0.23, P = 0.029), and BFT (r_s = +0.21, P = 0.043). Multivariable regression identified a positive association between plasma [FRA] and mean plasma [gluc] and [albumin] from Days 4–28 postpartum. Correcting plasma [FRA] for [albumin] improved the association (r_s = +0.46, P < 0.001) between plasma [FRA] and mean plasma [gluc].

Conclusions and Clinical Importance

Plasma [FRA] does not provide a clinically useful method for quantifying the magnitude of hypoglycemia or negative energy balance in dairy cows during early lactation.

Efeito da suplementação com colina protegida sobre parâmetros bioquímicos, produção e reprodução de vacas leiteiras no periparto

RESUMO Avaliou-se o efeito da suplementação com colina protegida sobre o perfil energético, as enzimas hepáticas e a reprodução de vacas leiteiras no periparto. Quinze vacas leiteiras foram divididas em dois grupos experimentais: oito receberam 80 gramas de colina protegida por 21 dias no pré-parto e por 40 dias no pós-parto e sete foram consideradas controle. Amostras de sangue foram coletadas nos dias 10, 20, 30 e 60 pós-parto para avaliação dos perfis energético e hepático. Aos 60 dias pós-parto, realizou-se exame ginecológico dos animais para avaliação da saúde reprodutiva. A suplementação com colina protegida não alterou os níveis de beta-hidroxibutirato (BHBA), ácidos graxos não esterificados (AGNE), frutosamina, fator de crescimento semelhante a glicose I (IGF-I), status oxidante total (TOS), aspartato aminotransferase (AST) e gamaglutamiltransferase (GGT) no pós-parto. Não houve diferença também quanto à produção de leite. Aos 60 dias pós-parto, vacas suplementadas com colina protegida apresentaram menor número de casos de endometrite que vacas do grupo controle. A suplementação de colina protegida não alterou o perfil bioquímico e a produção de leite, mas reduziu o número de casos de endometrite no pós-parto de vacas leiteiras.

Evaluation of the serum fructosamine test to monitor plasma glucose concentration in the transition dairy cow

The usefulness of the serum fructosamine (Fser) to monitor the retrospective glucose concentrations in transitional dairy cows (n=17) was evaluated. In weekly blood samples (3 weeks before to 5 weeks after calving) concentrations of plasma glucose and serum fructosamine, β-hydroxybutyrate (βOHB) and total proteins were determined. The observed Fser concentrations (271±55 mean value, range 152–423 μmol/l) were within the range reported in the literature, and showed a progressive and significant decrease after calving. Mean plasma glucose concentration was 60·6±5·0 (range 39·9–82·2) mg/dl increasing from week 3 before calving to the week of calving and then decreasing during the next 5 weeks of lactation. This decrease was coincident with inverse relationships between plasma glucose and milk yield (P=0·03) and serum βOHB (P<0·001). Linear regression analysis performed between serum fructosamine and (a) plasma glucose concentration of the same sampling and (b) plasma glucose concentration of 1, 2 and 3 weeks preceding the sampling, did not show significant and systematizing positive correlations. Persistent hypoproteinaemias that could affect the fructosamine concentrations were not found: mean value and range of serum proteins was 6·3±1·0 and 4·8–7·8 g/dl, respectively, and no correlation was found between serum proteins and Fser (P=0·26). Results did not support the possibility of retrospective monitoring of the plasma glucose concentration by serum fructosamine in dairy cows in the transition period.

Variability characteristics and test selection in herd-level nutritional and metabolic profile testing

Nutritional assessment based on animal response factors is the basis of essentially all dietary recommendations. Blood concentrations of nutrients, metabolites, and hormones are important animal response factors associated with nutriture, making blood analysis an important nutritional assessment technique. There are, however, numerous sources of variability, other than nutrition, affecting the concentration of blood analytes used in nutritional assessment. Minimizing the effects of non-nutrient sources of variability and maximizing the effects of nutritional variability is the objective in designing strategies for blood sampling and testing for nutritional assessment. Important non-nutrient sources of variability are age, sex, gestation stage, lactation stage and milk yield, and season. When interpreting test results, grouping animals by these characteristics is an important means of minimizing the effects of non-nutritional variability. Within these groups, it is important to take an adequate number of samples, generally starting out with at least seven. Finally, selecting appropriate tests is critical. Tests commonly used for clinicopathologic evaluations are not necessarily the best tests for nutritional assessment. Analytes should be chosen that are likely to have a large portion of their total variability caused by nutritional effects. This generally does not include those metabolites the blood concentrations of which are rigidly controlled by homeostatic forces.

Longissimus dorsi muscle diameter, backfat thickness, body condition scores and skinfold values related to metabolic and endocrine traits in lactating dairy cows fed crystalline fat or free fatty acids

An experiment was performed using 18 dairy cows with > or = 2 lactations from parturition until week 20 of lactation to investigate the effects of feeding rumen-protected crystalline fat (group A) or free fatty acids (group B) compared with a control group not fed supplemental fat or fatty acids (group C). The feeding effects studied were those on milk yield and composition, body weight (BW), body conditions scores (BCS), skinfold values (a measure of subcutaneous fat tissue thickness), backfat thickness and longissimus dorsi muscle diameter (measured by ultrasound), as well as on blood plasma metabolic and endocrine traits. Fat and fatty-acid feeding reduced roughage intake. Net energy and protein balances during the first week of lactation were negative. Milk yield was similar in all groups, but concentrations of milk fat were reduced in group B and of milk protein in groups A and B. BW, BCS, skinfold value, backfat thickness and longissimus dorsi muscle diameter similarly decreased in all groups until weeks 8-12. Concentrations of glucose and fructosamine decreased transiently during early lactation, whereas levels of beta-hydroxybutyrate, urea, total protein and albumin increased reversibly and similarly in all groups. Concentrations of creatinine decreased similarly in all groups until week 4 and those of nonesterified fatty acids until week 12. Triglyceride concentrations increased continuously until week 18, whereas concentrations of phospholipid and cholesterol increased until week 10 and then remained elevated. Triglyceride, phospholipid and cholesterol concentrations were higher in group B than in groups A and C throughout the experiment. Concentrations of insulin, insulin-like growth factor-1, thyroxine and 3,5,3'-triiodothyronine started to increase after the first 6-8 weeks of lactation, while those of growth hormone were transiently low in week 16. None of the hormones exhibited group differences. In this study rumen-protected fat or fatty-acid supplementation failed to improve the energy and protein balances during early lactation and did not affect milk yield, likely due to decreased roughage intake. BCS, skinfold values and backfat ultrasound measurements of subcutaneous adipose tissue mass and of longissimus dorsi muscle diameter indicated mobilization of fat tissue and protein mobilization in early lactation and were mirrored by typical changes of metabolic and endocrine traits.