Microbiome and metabolome analyses of milk and feces from dairy cows with healthy, subclinical, and clinical mastitis

Mastitis is commonly recognized as a localized inflammatory udder disease induced by the infiltration of exogenous pathogens. In the present study, our objective was to discern fecal and milk variations in both microbiota composition and metabolite profiles among three distinct groups of cows: healthy cows, cows with subclinical mastitis and cows with clinical mastitis. The fecal microbial community of cows with clinical mastitis was significantly less rich and diverse than the one harbored by healthy cows. In parallel, mastitis caused a strong disturbance in milk microbiota. Metabolomic profiles showed that eleven and twenty-eight molecules exhibited significant differences among the three groups in feces and milk, respectively. Similarly, to microbiota profile, milk metabolome was affected by mastitis more extensively than fecal metabolome, with particular reference to amino acids and sugars. Pathway analysis revealed that amino acids metabolism and energy metabolism could be considered as the main pathways altered by mastitis. These findings underscore the notable distinctions of fecal and milk samples among groups, from microbiome and metabolomic points of view. This observation stands to enhance our comprehension of mastitis in dairy cows.

Alterations in the Milk Metabolome of Dairy Cows Supplemented with Different Levels of Calcium Propionate in Early Lactation

This study aimed to investigate the effects of dietary supplementation with different levels of calcium propionate on the lactation performance, blood energy metabolite parameters, and milk metabolites of dairy cows in early lactation. Thirty-two multiparous Holstein cows were randomly divided into 4 groups, which were orally drenched with 0, 200, 350, and 500 g/d calcium propionate per cow supplemented to a basal diet for 5 weeks from calving. The milk and blood of the dairy cows were sampled and measured every week. The milk samples from the last week were used for the metabolomic analysis via liquid chromatography–mass spectrometry (LC-MS). The results showed that the calcium propionate supplementation quadratically increased the dry matter intake, energy-corrected milk yield, and 4% fat-corrected milk yield; linearly reduced the milk protein and milk lactose concentrations; and quadratically decreased the somatic cell count in the milk. With the increase in calcium propionate, the serum glucose content showed a linear increase, while the serum insulin content showed a quadratic increase. The diets supplemented with calcium propionate quadratically decreased the β-hydroxybutyric acid and linearly decreased the non-esterified fatty acid content in the serum. The metabolomic analysis revealed that eighteen different metabolites were identified in the milk samples of the dairy cows supplemented with calcium propionate at 350 g/d, which decreased the abundance of genistein and uridine 5-monophosphate and increased the abundance of adenosine, uracil, protoporphyrin IX, and sphingomyelin (d 18:1/18:0) compared with the control group. The milk metabolic analysis indicated that the calcium propionate effectively improved the milk synthesis and alleviated the mobilization of adipose tissue and bone calcium. In summary, the calcium propionate could improve the lactation performance and energy status and promote the milk metabolic profile of dairy cows in early lactation. Calcium propionate (350 g/d) is a well-recommended supplement for dairy cows for alleviating negative energy balance and hypocalcemia in early lactation.

Invited review: The influence of immune activation on transition cow health and performance-A critical evaluation of traditional dogmas

The progression from gestation into lactation represents the transition period, and it is accompanied by marked physiological, metabolic, and inflammatory adjustments. The entire lactation and a cow's opportunity to have an additional lactation are heavily dependent on how successfully she adapts during the periparturient period. Additionally, a disproportionate amount of health care and culling occurs early following parturition. Thus, lactation maladaptation has been a heavily researched area of dairy science for more than 50 yr. It was traditionally thought that excessive adipose tissue mobilization in large part dictated transition period success. Further, the magnitude of hypocalcemia has also been assumed to partly control whether a cow effectively navigates the first few months of lactation. The canon became that adipose tissue released nonesterified fatty acids (NEFA) and the resulting hepatic-derived ketones coupled with hypocalcemia lead to immune suppression, which is responsible for transition disorders (e.g., mastitis, metritis, retained placenta, poor fertility). In other words, the dogma evolved that these metabolites and hypocalcemia were causal to transition cow problems and that large efforts should be enlisted to prevent increased NEFA, hyperketonemia, and subclinical hypocalcemia. However, despite intensive academic and industry focus, the periparturient period remains a large hurdle to animal welfare, farm profitability, and dairy sustainability. Thus, it stands to reason that there are alternative explanations to periparturient failures. Recently, it has become firmly established that immune activation and the ipso facto inflammatory response are a normal component of transition cow biology. The origin of immune activation likely stems from the mammary gland, tissue trauma during parturition, and the gastrointestinal tract. If inflammation becomes pathological, it reduces feed intake and causes hypocalcemia. Our tenet is that immune system utilization of glucose and its induction of hypophagia are responsible for the extensive increase in NEFA and ketones, and this explains why they (and the severity of hypocalcemia) are correlated with poor health, production, and reproduction outcomes. In this review, we argue that changes in circulating NEFA, ketones, and calcium are simply reflective of either (1) normal homeorhetic adjustments that healthy, high-producing cows use to prioritize milk synthesis or (2) the consequence of immune activation and its sequelae.

Milk Production and Energetic Metabolism of Heat-Stressed Dairy Goats Supplemented with Propylene Glycol

Heat-stressed dairy animals increase their reliance on glucose. This elevated glucose demand is partially met by increasing the conversion of glucogenic amino acids (AA) in the liver. Propylene glycol (PG) is a glucogenic precursor and was not tested in dairy goats under thermoneutral (TN) and heat stress (HS) conditions simultaneously. We hypothesize that if HS-goats are fed with PG, they would get more glucose and consequently spare more glucogenic AA for milk protein synthesis rather than gluconeogenesis. Eight multiparous dairy goats (40.8 ± 1.1 kg body weight; 84 ± 1 days in milk) were used in a replicated 4 × 4 Latin square design of 4 periods; 21 d each (14 d adaptation, 5 d for measurements, and 2 d of transition). Goats were allocated to one of 4 treatments in a 2 × 2 factorial arrangement. Factors were control (CO) without PG or 5% of PG, and thermoneutral (TN; 15 to 20 °C) or heat stress (HS; 12 h/d at 37 °C and 12 h/d at 30 °C) conditions. Feed intake, rectal temperature, respiratory rate, milk yield, milk composition, and blood metabolites were measured. Compared to TN, HS goats had lower (p < 0.01) feed intake (-34%), fat-corrected milk (-15%), and milk fat (-15%). Heat-stressed goats also tended (p < 0.10) to produce milk with lower protein (-11%) and lactose (-4%) contents. Propylene glycol increased blood glucose (+7%; p < 0.05), blood insulin (+37%; p < 0.10), and body weight gain (+68%; p < 0.05), but decreased feed intake (-9%; p < 0.10) and milk fat content (-23%; p < 0.01). Furthermore, blood non-esterified fatty acids (-49%) and β-hydroxybutyrate (-32%) decreased (p < 0.05) by PG. In conclusion, supplementation of heat-stressed dairy goats with propylene glycol caused milk fat depression syndrome, but reduced body weight loss that is typically observed under HS conditions. Supplementation with lower doses of PG would avoid the reduced feed intake and milk fat depression, but this should be tested.

Propylene Glycol and Maize Grain Supplementation Improve Fertility Parameters in Dairy Cows

Simple Summary

The excessive mobilization of fatty acids from dairy cows’ adipose tissue increases blood non-esterified fatty acid concentrations and could have a negative effect on the fertility parameters and milk yield, as well as increase the risk of metabolic disorders and also result in early-lactation culling risk. Propylene glycol and rumen-protected starch from maize grain are commonly used as glucose precursors reducing nonesterified fatty acid levels; however, no such comparisons are available, thus it was decided to assume it as the aim of this study. Propylene glycol had a positive effect on shortening the period to first ovulation. Propylene glycol and maize grain improved the first service conception rate and decreased the number of services per conception in cows. In conclusion, both treatments with propylene glycol and maize grain had a slight effect on the metabolic profile and no effect on milking performance, yet they improved fertility parameters, which could indirectly enhance milk production economics.

Abstract

The aim of the study was to determine the effect of propylene glycol and maize grain content by-pass starch supplementation during the transition period and the first 56 days of lactation on blood metabolic indices, milk production and fertility parameters in dairy cows. Seventy-five Polish Holstein-Friesian dairy cows were assigned to treatment 21 days before calving. The treatments included: TG—2.5 kg triticale grain/cow per day supplemented from 14 days prepartum to day 56 postpartum, PG—2.5 kg triticale grain/cow per day supplemented from day 14 before parturition to day 56 postpartum, and 400 g propylene glycol/cow per day from 14 days prepartum to 14 days of lactation and MG—2.5 kg maize grain/cow per day supplemented from day 14 before parturition to day 56 postpartum. PG and MG had an effect resulting in the highest glucose concentration at 28 d of lactation. Cows assigned to the PG and MG groups had significantly higher cholesterol levels confronted with TG group at day 14 of lactation, while at days 28 and 56 the same difference was observed only between the MG and TG groups. PG had an effect on shortening the period to first ovulation. PG and MG improved the first service conception rate and decreased the number of services per conception in cows. In conclusion, both treatments of dairy cows with PG and MG improved their fertility parameters, while they had a slight effect on their metabolic profile and no effect on their milking performance.

Effects of Propylene Glycol on Negative Energy Balance of Postpartum Dairy Cows

Simple Summary

After calving, the milk production of dairy cows increases rapidly, but the nutrient intake cannot meet the demand for milk production, forming a negative energy balance. Dairy cows in a negative energy balance have an increased risk of developing clinical or subclinical ketosis. The ketosis in dairy cows has a negative impact on milk production, dry matter intake, health, immunity, and reproductive performance. Propylene glycol can be used as an important gluconeogenesis in ruminants and can effectively inhibit the formation of ketones. Supplementary propylene glycol to dairy cows during perinatal is an effective method to alleviate the negative energy balance. This review summarizes the reasons and consequences of negative energy balance as well as the mechanism and effects of propylene glycol in inhibiting a negative energy balance in dairy cows. In addition, the feeding levels and methods of using propylene glycol to alleviate negative energy balance are also discussed.

Abstract

With the improvement in the intense genetic selection of dairy cows, advanced management strategies, and improved feed quality and disease control, milk production level has been greatly improved. However, the negative energy balance (NEB) is increasingly serious at the postpartum stage because the intake of nutrients cannot meet the demand of quickly improved milk production. The NEB leads to a large amount of body fat mobilization and consequently the elevated production of ketones, which causes metabolic diseases such as ketosis and fatty liver. The high milk production of dairy cows in early lactation aggravates NEB. The metabolic diseases lead to metabolic disorders, a decrease in reproductive performance, and lactation performance decline, seriously affecting the health and production of cows. Propylene glycol (PG) can alleviate NEB through gluconeogenesis and inhibit the synthesis of ketone bodies. In addition, PG improves milk yield, reproduction, and immune performance by improving plasma glucose and liver function in ketosis cows, and reduces milk fat percentage. However, a large dose of PG (above 500 g/d) has toxic and side effects in cows. The feeding method used was an oral drench. The combination of PG with some other additives can improve the effects in preventing ketosis. Overall, the present review summarizes the recent research progress in the impacts of NEB in dairy cows and the properties of PG in alleviating NEB and reducing the risk of ketosis.

Economic value of information from an alert system on physiological imbalance in fresh cows

Physiological imbalance is an abnormal physiological condition that cannot be directly observed but is assumed to precede subclinical and clinical diseases in the beginning of lactation. Alert systems to detect the physiological imbalance in a cow using Fourier transform mid-infrared spectroscopy in milk have been developed. The objective of this study was to estimate the value of information provided from such system with different indicator accuracies, herd prevalence and prices. A decision tree was created to model the probabilities of detection and associated costs of test outcome, intervention and occurrence of disease. We assumed that the negative effect of physiological imbalance was the development of subclinical ketosis and that this negative effect was prevented by drenching the cows with propylene glycol for 5 days. We simulated the economic impact of subclinical ketosis mediated through physiological imbalance to be $194 per case. The results showed that if the alert system was highly accurate (Se = 0.99/Sp = 0.99), and the prevalence of physiological imbalance was 30 %, the value of information provided from the system is $19 per cow-year. In case the prevalence is 5 % or 50 %, the value of information is $3 and $13, respectively. These estimates for the value do not cover the capital costs and operational costs of the alert system. This study furthermore clearly demonstrated that in order to estimate the value of information correctly, it is important to consider that drenching all cows and not drenching any of the cows are the two relevant alternative options in the absence of the alert system. In conclusion, the decision tree and sensitivity analysis developed in this study show that final economic results are highly variable to the prevalence of physiological imbalance and highest at an intermediate prevalence. Other relevant factors are the costs associated with drenching and the cost associated with treating false positives and not treating false negatives. In addition, this study highlights the benefits of simulation to pinpoint where additional information is needed to further quantify the economic value and required accuracy of an indication-based intervention system.

Only few benefits from propylene glycol drench in early lactation for cows identified as physiologically imbalanced based on milk spectra analyses

The main objective of this study was to test the efficiency of a management system combining metabolic clustering of cows based on Fourier-transform mid-infrared (FT-MIR) spectra of milk and targeted treatment of metabolically imbalanced cows with propylene glycol drench. We hypothesized that cows identified in a metabolically imbalanced status during early lactation were associated with subsequent impaired health, reproduction, and production, and that treatment with propylene glycol treatment would improve health, reproduction, and production relatively more in these cows than in control cows. We completed a prospective, randomized controlled trial with 356 early-lactation cows in 2 private dairy herds in Denmark from December 2017 to April 2018. Milk samples of cows were collected before treatment, from 4 to 9 d in milk, and after treatment, from 22 to 27 d in milk. Milk samples were analyzed using FT-MIR spectroscopy. We also measured 4 milk metabolites (β-hydroxybutyrate, isocitrate, malate, and glutamate) and fat and protein contents. Based on FT-MIR spectra and cluster analyses, cows were clustered into groups of metabolically imbalanced and healthy cows. Within each group, cows were allocated randomly to treatment with propylene glycol (500 mL for 5 d) or no treatment. We analyzed the effect of the treatment on cow-level variables: metabolic cluster, milk metabolites, fat and protein contents, and fat-to-protein ratio at a milk sampling after the treatment. Furthermore, we analyzed daily milk yield, calving to first service interval, and disease occurrence. Results showed only a few effects of propylene glycol treatment and few interactions between treatment and metabolic clusters. We found no significant main effects of propylene glycol treatment in any of these analyses. A negative effect of the imbalanced metabolic cluster was found for the outcome of calving to first service interval for multiparous cows. In conclusion, we found a longer calving to first service interval in metabolically imbalanced cows, but we were not able to demonstrate overall benefits from the applied detection of cows in imbalanced metabolic status in early lactation and follow-up by treatment with propylene glycol.

Glycerol use in dairy diets: A systemic review

There is an increasing interest in the production of biodiesel as bio-renewable fuel source, with numerous biofuel byproducts becoming available. The annual productions of biodiesel and crude glycerol were 34.5 and 3.8 billion liters, respectively, in 2016 and that of biodiesel is expected to reach 41 billion liters in 2019. Glycerol is a sugar alcohol without a color or odor, but with a sweet taste and high solubility index in water. Experiments support the use of glycerol at low levels ranging from 5% to 8% of the diet dry matter as a transition cow therapy. Administration of glycerol increases serum glucose and decreases ketone bodies. Glycerol is very rapidly fermented in the rumen to propionate and butyrate, at the expense of acetate, resulting in a decreased milk fat. Because glycerol is highly fermented in the rumen, it requires an adaptation period at the beginning of feeding. Administration of glycerol in the diet of lactating animals was paralleled with a decreased or an unaffected feed intake in most experiments. Improved ruminal environment to enhance nutrient digestibility was observed in many experiments; however, others observed reduced digestion of dietary fiber with feeding glycerol. Enhanced, lowered, or unaffected milk production and composition were observed with the administration of glycerol in lactating animal diets; however, in most cases, glycerol decreased milk fat content. The inconsistencies between results of experiments are due to the level and the purity of glycerol, diets, production stage of the animals, and other factors. Therefore, further research should be conducted to establish the efficacy of different levels, purity and administration periods of glycerol, and production stage of dairy animals fed glycerol-based or supplemented diets.

Prediction of metabolic status of dairy cows in early lactation with on-farm cow data and machine learning algorithms

Metabolic status of dairy cows in early lactation can be evaluated using the concentrations of plasma β-hydroxybutyrate (BHB), free fatty acids (FFA), glucose, insulin, and insulin-like growth factor 1 (IGF-1). These plasma metabolites and metabolic hormones, however, are difficult to measure on farm. Instead, easily obtained on-farm cow data, such as milk production traits, have the potential to predict metabolic status. Here we aimed (1) to investigate whether metabolic status of individual cows in early lactation could be clustered based on their plasma values and (2) to evaluate machine learning algorithms to predict metabolic status using on-farm cow data. Through lactation wk 1 to 7, plasma metabolites and metabolic hormones of 334 cows were measured weekly and used to cluster each cow into 1 of 3 clusters per week. The cluster with the greatest plasma BHB and FFA and the lowest plasma glucose, insulin, and IGF-1 was defined as poor metabolic status; the cluster with the lowest plasma BHB and FFA and the greatest plasma glucose, insulin, and IGF-1 was defined as good metabolic status; and the intermediate cluster was defined as average metabolic status. Most dairy cows were classified as having average or good metabolic status, and a limited number of cows had poor metabolic status (10-50 cows per lactation week). On-farm cow data, including dry period length, parity, milk production traits, and body weight, were used to predict good or average metabolic status with 8 machine learning algorithms. Random Forest (error rate ranging from 12.4 to 22.6%) and Support Vector Machine (SVM; error rate ranging from 12.4 to 20.9%) were the top 2 best-performing algorithms to predict metabolic status using on-farm cow data. Random Forest had a higher sensitivity (range: 67.8-82.9% during wk 1 to 7) and negative predictive value (range: 89.5-93.8%) but lower specificity (range: 76.7-88.5%) and positive predictive value (range: 58.1-78.4%) than SVM. In Random Forest, milk yield, fat yield, protein percentage, and lactose yield had important roles in prediction, but their rank of importance differed across lactation weeks. In conclusion, dairy cows could be clustered for metabolic status based on plasma metabolites and metabolic hormones. Moreover, on-farm cow data can predict cows in good or average metabolic status, with Random Forest and SVM performing best of all algorithms.

Effect of rumen-protected branched-chain amino acid supplementation on production- and energy-related metabolites during the first 35 days in milk in Holstein dairy cows

Essential AA are critical for multiple physiological processes. Branched-chain AA (BCAA) supplementation has beneficial effects on body weight, lipogenesis, and insulin resistance in several species. The BCAA are used for milk and body protein synthesis as well as being oxidized by the tricarboxylic acid cycle to produce ATP during catabolic states. The objective was to evaluate the effect of rumen-protected BCAA (375 g of 27% l-Leu, 85 g of 48% l-Ile, and 91 g of 67% l-Val) with or without propylene glycol (PG) oral administration on milk production, dry matter intake, nonesterified fatty acids, β-hydroxybutyrate, and plasma urea nitrogen during the first 35 d in milk (DIM) in dairy cattle. Multiparous Holstein cows were enrolled in blocks of three 28 d before expected calving and assigned randomly to either the control or 1 of 2 treatments. The control (n = 26) received 200 g/d of dry molasses, the BCAA treatment (n = 23) received BCAA mixed with 200 g/d of dry molasses from calving until 35 DIM, and the BCAA plus PG (BCAAPG) treatment (n = 25) received BCAA mixed with 200 g/d of dry molasses from calving until 35 DIM plus 300 mL of PG once daily from calving until 7 DIM. Postpartum, dry matter intake least squares means (LSM; 95% confidence interval) were 20.7 (19.9, 21.7), 21.3 (20.4, 22.3), and 21.9 (20.9, 22.8) kg for control, BCAA, and BCAAPG, respectively. Milk yield (1-35 DIM) LSM were 41.7 (39.4, 44.0), 42.7 (40.3, 45.0), and 43.7 (41.4, 46.0) kg for control, BCAA, and BCAAPG, respectively. Energy-corrected milk LSM were 50.3 (46.8, 53.7), 52.4 (48.9, 55.8), and 52.9 (49.5, 56.4) kg for control, BCAA, and BCAAPG, respectively. Milk urea nitrogen LSM in milk for control, BCAA, and BCAAPG were 8.60 (8.02, 9.22), 9.70 (9.01, 10.45), and 9.75 (9.08, 10.47) mg/dL. Plasma urea nitrogen concentrations LSM for control, BCAA, and BCAAPG were 8.3 (7.7, 8.9), 10.1 (9.4, 10.9), and 9.6 (9.4, 10.3) mg/dL, respectively. The numbers of plasma samples classified as hyperketonemia were 77, 44, and 57 in control, BCAA, and BCAAPG, respectively. The BCAA supplementation increased plasma urea nitrogen and milk urea nitrogen, free valine concentration in plasma, and decreased hyperketonemia events during the postpartum period.

Prediction of metabolic clusters in early-lactation dairy cows using models based on milk biomarkers

The aim of this study was to describe metabolism of early-lactation dairy cows by clustering cows based on glucose, insulin-like growth factor I (IGF-I), free fatty acid, and β-hydroxybutyrate (BHB) using the k-means method. Predictive models for metabolic clusters were created and validated using 3 sets of milk biomarkers (milk metabolites and enzymes, glycans on the immunogamma globulin fraction of milk, and Fourier-transform mid-infrared spectra of milk). Metabolic clusters are used to identify dairy cows with a balanced or imbalanced metabolic profile. Around 14 and 35 d in milk, serum or plasma concentrations of BHB, free fatty acids, glucose, and IGF-I were determined. Cows with a favorable metabolic profile were grouped together in what was referred to as the "balanced" group (n = 43) and were compared with cows in what was referred to as the "other balanced" group (n = 64). Cows with an unfavorable metabolic profile were grouped in what was referred to as the "imbalanced" group (n = 19) and compared with cows in what was referred to as the "other imbalanced" group (n = 88). Glucose and IGF-I were higher in balanced compared with other balanced cows. Free fatty acids and BHB were lower in balanced compared with other balanced cows. Glucose and IGF-I were lower in imbalanced compared with other imbalanced cows. Free fatty acids and BHB were higher in imbalanced cows. Metabolic clusters were related to production parameters. There was a trend for a higher daily increase in fat- and protein-corrected milk yield in balanced cows, whereas that of imbalanced cows was higher. Dry matter intake and the daily increase in dry matter intake were higher in balanced cows and lower in imbalanced cows. Energy balance was continuously higher in balanced cows and lower in imbalanced cows. Weekly or twice-weekly milk samples were taken and milk metabolites and enzymes (milk glucose, glucose-6-phosphate, BHB, lactate dehydrogenase, N-acetyl-β-d-glucosaminidase, isocitrate), immunogamma globulin glycans (19 peaks), and Fourier-transform mid-infrared spectra (1,060 wavelengths reduced to 15 principal components) were determined. Milk biomarkers with or without additional cow information (days in milk, parity, milk yield features) were used to create predictive models for the metabolic clusters. Accuracy for prediction of balanced (80%) and imbalanced (88%) cows was highest using milk metabolites and enzymes combined with days in milk and parity. The results and models of the present study are part of the GplusE project and identify novel milk-based phenotypes that may be used as predictors for metabolic and performance traits in early-lactation dairy cows.

Lactobacillus reuteri suppresses E. coli O157:H7 in bovine ruminal fluid: Toward a pre-slaughter strategy to improve food safety?

The bovine gastrointestinal tract (GIT) is the main reservoir for enterohaemorrhagic Escherichia coli (EHEC) responsible for food-borne infections. Therefore, it is crucial to develop strategies, such as EHEC suppression by antagonistic microorganisms, to reduce EHEC survival in the GIT of cattle and to limit shedding and food contamination. Most human-derived Lactobacillus reuteri strains produce hydroxypropionaldehyde (HPA), an antimicrobial compound, during anaerobic reduction of glycerol. The capacity of L. reuteri LB1-7, a strain isolated from raw bovine milk, to produce HPA and its antimicrobial activity against an O157:H7 EHEC strain (FCH6) were evaluated in bovine rumen fluid (RF) under strict anaerobiosis. EHEC was totally suppressed when incubated in RF inoculated with L. reuteri LB1-7 and supplemented with 80 mM glycerol (RF-Glyc80). The addition of LB1-7 or glycerol alone did not modify EHEC survival in RF. Glycerol was converted to HPA (up to 14 mM) by LB1-7 during incubation in RF-Glyc80, and HPA production appeared to be responsible for EHEC suppression. The bactericidal activity of L. reuteri LB1-7, the concentration of glycerol required and the level of HPA produced depended on physiological and ecological environments. In vitro experiments also showed that EHEC inoculated in rumen fluid and exposed to L. reuteri and glycerol had a very limited growth in rectal contents. However, L. reuteri exerted an antimicrobial activity against the rumen endogenous microbiota and perturbed feedstuff degradation in the presence of glycerol. The potential administration of L. reuteri and glycerol in view of application to finishing beef cattle at the time of slaughter is discussed. Further in vivo studies will be important to confirm the efficiency of L. reuteri and glycerol supplementation against EHEC shedding in ruminants.

Effects of different dosages of propylene glycol in dry cows and cows in early lactation

In this Research Paper we hypothesised that the temporary insulin resistance seen during the transition period in dairy cows may cause significant differences in the efficacy of PG at different sampling periods and that in some cases this effect will be dose dependent. Eighty four sampling sets were generated by studying 7 multiparous Holstein cows repeatedly at 4 sampling periods of 3 d length (dry cows: days 40, 39 and 38 antepartum; close up cows: days 10, 9 and 8 antepartum; fresh cows: days 3, 4 and 5 post-partum; lactating cows: days 38, 39 and 40 post-partum). On each of these days 3 h after morning feeding propylene glycol was drenched in different dosages of 100, 300 or 500 ml once per day (cross over study). The different doses were applied in an alternating order (Latin square). Blood samples were taken before, every 30 min up to 4 h, after 6 and 12 h after PG application. Following parameters have been measured: insulin, non-esterified fatty acids (NEFA), betahydroxybutyrate (BHB), bilirubin, cholesterol, potassium, aspartate aminotransferase (AST) and glutamate dehydrogenase (GLDH). Revised Quantitative Insulin Sensitivity Check Index (RQUICKI) was calculated. It was found that glucose, insulin, NEFA, BHB, bilirubin and potassium concentrations were influenced differently by the three defined dosages of propylene glycol at four different sampling periods. Whereas RQUICKI, cholesterol, AST and GLDH did not differ between the sampling periods and treatments. The major results of the study are that the effect of PG is dose-dependent and that the effect of PG is depending on the time of application according to calving. It can be concluded that in fresh cows higher dosages are necessary to provoke similar effects in comparison to dry, close up and lactating cows. Although the study did not compare to topdressing of PG from the results it is reasonable to believe that bolus application of a specific PG volume is necessary to provoke the effect.

Effects of ambient temperature and dietary glycerol addition on growth performance, blood parameters and immune cell populations of Korean cattle steers

Objective

This study was performed to evaluate whether ambient temperature and dietary glycerol addition affect growth performance, and blood metabolic and immunological parameters, in beef cattle.

Methods

Twenty Korean cattle steers (405.1±7.11 kg of body weight [BW], 14.2±0.15 months of age) were divided into a conventional control diet group (n = 10) and a 2% glycerol- added group (n = 10). Steers were fed 1.6% BW of a concentrate diet and 0.75% BW of a timothy hay diet for 8 weeks (4 weeks from July 28th to August 26th and 4 weeks from August 27th to September 26th). Blood was collected four times on July 28th, August 11th, August 27th, and September 26th.

Results

The maximum indoor ambient temperature-humidity index in August (75.8) was higher (p<0.001) than that in September (70.0), and in August was within the mild heat stress (HS) category range previously reported for dairy cattle. The average daily gain (ADG; p = 0.03) and feed efficiency (p<0.001) were higher in hotter August than in September. Glycerol addition did not affect ADG and feed efficiency. Neither month nor glycerol addition affected blood concentrations of cortisol, triglyceride, or non-esterified fatty acid. Blood concentrations of cholesterol, low-density lipoprotein, high-density lipoprotein, glucose, and albumin were lower (p<0.05) on August 27th than on September 26 th, and blood phosphorus, calcium and magnesium concentrations were also lower on August 27th than on September 27th. Glycerol addition did not affect these blood parameters. Percentages of CD4⁺ T cells and CD8⁺ T cells were higher (p<0.05) on July 28th than on August 27th and September 26th. The blood CD8⁺ T cell population was lower in the glycerol supplemented-group compared to the control group on July 28th and August 27th.

Conclusion

Korean cattle may not be significantly affected by mild HS, considering that growth performance of cattle was better in hotter conditions, although some changes in blood metabolic and mineral parameters were observed.

Effect of propylene glycol on adipose tissue mobilization in postpartum over-conditioned Holstein cows

Our objective was to investigate the quantitative and qualitative effects of propylene glycol (PG) allocation on postpartum adipose tissue mobilization in over-conditioned Holstein cows. Nine ruminally cannulated and arterially catheterized cows were, at parturition, randomly assigned to a ruminal pulse dose of either 500g of tap water (n=4) or 500g of PG (n=5) once a day. The PG was given with the morning feeding for 4 wk postpartum (treatment period), followed by a 4-wk follow-up period. All cows were fed the same prepartum and postpartum diets. At -16 (±3), 4 (±0), 15 (±1) and 29 (±2) days in milk (DIM), body composition was determined using the deuterium oxide dilution technique, liver and subcutaneous adipose tissue biopsies were collected, and mammary gland nutrient uptake was measured. Weekly blood samples were obtained during the experiment and daily blood samples were taken from -7 to 7 DIM. Postpartum feed intake and milk yield was not affected by PG allocation. The body content of lipid was not affected by treatment, but tended to decrease from 4 to 29 DIM with both treatments. Except for the first week postpartum, no difference in plasma nonesterified fatty acids concentration was noted between treatments in the treatment period. Yet, PG allocation resulted in decreased plasma concentrations of β-hydroxybutyrate (BHB) and increased plasma concentrations of glucose. In the follow-up period, plasma concentrations of nonesterified fatty acids, glucose, and BHB did not differ between treatments. Additionally, the change in abundance of proteins in adipose tissue biopsies from prepartum to 4 DIM was not affected by treatment. In conclusion, the different variables to assess body fat mobilization were concurrent and showed that a 4-wk postpartum PG allocation had limited effect on adipose tissue mobilization. The main effect was an enhanced glucogenic status with PG. No carry-over effect of PG allocation was recorded for production or plasma metabolites, and, hence, a new period of metabolic adaption to lactation seemed to occur with PG treatment after ceasing PG allocation. Thus, PG seemed to induce a 2-step adaption to lactation, reducing the immediate postpartum nadir and peak of plasma concentration of glucose and BHB, respectively; which is beneficial for postpartum cows at high risk of lipid-related metabolic diseases.

Evaluation of hyperketonemia risk period and screening protocols for early-lactation dairy cows

The objectives of this study were to describe the onset of hyperketonemia, the number of positive hyperketonemia test results, and the duration of the longest hyperketonemic period during the first 42 d in milk (DIM) in dairy cows. Furthermore, we set out to evaluate test characteristics of single and repeated measurements of β-hydroxybutyric acid (BHBA) during this period to diagnose hyperketonemia. Using an electronic handheld meter, 252 cows from 3 farms were tested twice weekly for hyperketonemia (blood BHBA ≥1.2 mmol/L) during the first 42 DIM, resulting in 12 test results per cow (i.e., in lactation wk 0.5 to 6). Prevalence and incidence of hyperketonemia were calculated for the 12 examination days and the 42-d period, respectively. Test characteristics for the diagnosis of hyperketonemia were calculated for 4 different testing scenarios (testing all cows 1, 2, 3, or 6 times during the first 42 DIM) and 2 different gold-standard definitions (BHBA ≥1.2 mmol/L at least once during the observation period or BHBA ≥1.2 mmol/L at least twice during the observation period). Mean prevalence of hyperketonemia was 11.8%, ranging from 9.6% in lactation wk 0.5 and 2.0 to 14.6% in lactation wk 5.5. In total, 134 cows (53.2%) had at least 1 positive hyperketonemia test result during the whole 42-d period. Of these cows, 46.3% had only 1 positive result. The median first positive hyperketonemia test result was in lactation wk 2.0 [interquartile range (IQR) 1.0-3.5]. Median frequency of positive test results in cows affected by hyperketonemia was 2 positive test results (IQR 1-3). Median duration of the longest hyperketonemic period per cow affected was 1 examination interval (3-4 d; IQR 1-2). Considering a minimum of 1 positive hyperketonemia test result during the first 42 DIM as the gold standard, sensitivity of a single BHBA measurement during this period to diagnose hyperketonemia was 21%. A weekly testing protocol had a sensitivity of 72%. Specificity was 100% in both cases. Considering a minimum of 2 positive hyperketonemia test results as the gold standard, sensitivity and specificity of a single BHBA measurement during the first 42 DIM were 33 and 97%, respectively. A weekly testing protocol provided sensitivity and specificity of 91 and 83%, respectively. We conclude that the risk period for hyperketonemia lasts at least until lactation wk 6, which should be considered when planning hyperketonemia screening programs. Test characteristics of screening protocols depend on testing frequency.

Effects of propylene glycol on the metabolic status and milk production of dairy buffaloes

OBJECTIVES

The study was designed to investigate the effects of drenching with propylene glycol (PG) on body condition, serum metabolites and milk production during the transition period of dairy buffaloes.

MATERIAL AND METHODS

Animals were randomly allocated to a control group (n=5) and a PG group of 10 buffaloes that were drenched with 500 ml of propylene glycol once daily from 10 (9±3) days prepartum until 2 weeks postpartum. Ultrasound measurements of backfat thickness (BFT) were performed weekly, while blood samples were taken at -4, -2, 2, 4, 6, and 8 weeks from parturition for estimation of hematological and biochemical metabolites.

RESULTS

At -4, -3, and -2 weeks from calving, BFT did not differ between the two groups, but decreased after calving and was higher for the control group than the PG group at weeks -1 and 1. Hematological analysis revealed insignificant changes between the two groups. Serum concentrations of non-esterified fatty acids (NEFA), β-hydroxybutyric acid (BHBA) and glucose did not differ between the two groups before parturition. At 2 and 4 weeks from parturition, NEFA was higher for the control group than the PG group. Serum concentrations of BHBA were higher at 2, 4, 6, and 8 weeks in control animals than in treated buffaloes. In contrast, the glucose level was significantly increased in PG group when compared to the control group at week 2 postpartum (p<0.05). Serum concentrations of total cholesterol, triglycerides, total proteins, albumin, and globulins did not differ significantly between the two groups (p>0.05). Serum enzyme activities of aspartate aminotransferase and γ-glutamyl transferase were significantly higher in the control than in the PG group. In treated buffaloes significantly (p<0.05) higher average 60-day milk yields were recorded (8.4±0.22 vs. 10.7±0.40 kg/day). Milk composition did not differ between the two groups.

CONCLUSION AND CLINICAL RELEVANCE

Drenching of dairy buffaloes with propylene glycol may reduce the risk of ketosis, improve the metabolic status, and increase the milk yield.

Effects of propylene glycol supplementation on blood indicators of hepatic function, body condition score, milk fat-protein concentration and reproductive performance of dairy cows

The aim of the present study was to determine the effects of propylene glycol on metabolic variables of hepatic function, body condition score, milk fat-protein concentration and reproductive performance of dairy cows after ending administration. Postparturient dairy cows (n = 200) of Holstein Friesian breed were divided into two groups of 100 individuals. The experimental group received during days 0-7 post partum an oral daily dose of 600 ml of propylene glycol; the control group was without any supplement. The hepatic enzymes, glucose, cholesterol and serum albumin were measured on days 10-15, 45-50 and 70 post partum. Reproduction indicators of dairy cows were calculated from the farm recording data and the milk data record from a regular dairy control (days 10, 20, 30, and 50 post partum). Animals that received propylene glycol in the first 7 days post partum had reduced activities of aspartate transaminase and gamma-glutamyl transferase, elevated cholesterol concentration (P < 0.05) and low milk fat percentage (P < 0.05) compared to control animals. Direct influence of propylene glycol drenching on the calving to first oestrus interval was observed, the smallest values being detected for the cows in the experimental group compared to the control group (P < 0.05). Our results suggest that some blood indicators of hepatic function, milk fat concentration and calving to first oestrus interval can be improved for 70 days post partum by the use of propylene glycol drenching in the first 7 days post partum. The beneficial effect of this treatment could be evaluated by easily available data, which can be used by practitioners in the field to analyze fertility problems in dairy herds and more exactly to examine whether metabolic stress, among other factors, is involved in the fertility problem.

Effects of feeding dry glycerol to primiparous Holstein dairy cows on follicular development, reproductive performance and metabolic parameters related to fertility during the early post-partum period

This study examined the effects of dry glycerol supplementation on follicular growth, post-partum interval to first ovulation, concentration of serum metabolites and hormones related to fertility, body condition score (BCS) and body weight (BW) in primiparous Holstein dairy cows. Sixty primiparous Holstein dairy cows were randomly assigned to two groups (control: n = 30 and glycerol supplemented: n = 30). Dry glycerol (250 g/day/cow) was fed as a top dressing to the common lactating total mixed ration (TMR) from parturition to 21 days post-partum. Ovaries were examined four times using ultrasonography on days 13, 19, 25 and 36 post-partum to determine ovarian follicular growth. Concentration of serum metabolites and hormones was determined weekly. Body condition score was evaluated weekly from weeks 1 to 5 after parturition, and BWs were recorded three times on days 1, 11 and 21 during the experimental period. The cows fed dry glycerol had more large follicles (p < 0.0001) and corpora lutea (CL) (p = 0.02) compared with the control cows. Days to the first ovulation (p = 0.06), days to first oestrus (p = 0.05), services per conception (p = 0.06) and days open (p = 0.004) were positively affected by dry glycerol supplementation. Serum concentration of glucose and insulin was higher in dry glycerol-supplemented cows (p = 0.1; p = 0.06, respectively). Feeding glycerol had no effect on mean serum concentrations of β-hydroxybutyrate, non-esterified fatty acids and IGF-1 during the experimental period. However, significant differences were observed at concentration of BHBA and IGF-1 (p = 0.02 and p = 0.04, respectively) between two groups on day 21 after calving. The cows in the glycerol-fed group had higher serum progesterone concentrations on days 33 (p = 0.007) and 36 (p = 0.004) after calving. Supplemented cows had lower body condition loss during weeks 1-5 after calving compared with the control cows (0.34 vs 0.41 BCS). In week 13 post-partum, the proportion of cycling cows was 83.3 and 69.9% for those which received supplemented or non-supplemented diet, respectively. These results demonstrated that feeding dry glycerol as a glucogenic supply may be useful to improve negative energy balance and reproductive efficiency in young cows which calve with high requirement of energy.

Effect of supplemental feeding with glycerol or propylene glycol in early lactation on the fertility of Swedish dairy cows

The aim of this field study was to evaluate the effect of supplemental feeding with glycerol (GLY) or propylene glycol (PG) during early lactation on the fertility of Swedish dairy cows. Within 17 commercial dairy herds, 798 cows were randomized to three groups that were daily fed supplements with 450 g GLY, 300 g PG or nothing (control, C). The supplements were given twice daily during 0-21 days in milk as a top dress on concentrates. Data on calving date, insemination dates, gynaecological examinations, as well as breed, parity and monthly milk yield were collected. From a subset of 308 cows in seven herds, milk samples for progesterone analysis were taken twice weekly and used to determine the time for onset of luteal activity. The effects of supplements on the intervals from calving to first luteal activity (FLA), first AI (FAI) and conception (CON), respectively, were analysed using semi-parametric survival models (Cox proportional hazards models) controlling for the effect of parity, breed, calving season, milk yield and the clustering effect of herd. There was no difference in time to FLA between the cows in group C and in group GLY or PG. No differences in time to FAI or in time to CON were found between cows in group PG and group C. However, cows in the GLY group tended to get their FAI later compared with cows in the control group but without at subsequent delaying of time to CON.