Effect of the Lactation Phases on the Amplitude of Variation in Blood Serum Steroid Hormones and Some Hematochemical Analytes in Three Dairy Cow Breeds

Lactation in dairy cows implies comprehensive endocrine and metabolic changes including a systemic electrolytic reaction. Previous studies have rarely considered these specific demands due to the influence of lactation periods. Therefore, this study aimed to assess the effects of early, middle, and late lactation phases on the dynamic changes in serum concentrations of progesterone (P4), 17β-oestradiol (E2), cortisol, and some electrolytes (Ca++, Mg++, Na+, K+, Cl-, Pi) and biochemical parameters (alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), creatine kinase (CK), total bilirubin, urea, and iron (Fe++) in 10 Holstein, 10 Brown Swiss, and 10 Modicana multiparous healthy dairy cows (4.2 ± 1.7 years of age) sampled at 60-day intervals throughout lactation. Lactation induced significant changes in the concentrations of P4, which peaked at >120-180 days, decreased at >240-300 days, and increased again after 300 days. Cortisol showed an opposite trend to P4, with concentrations progressively decreasing, except for the phase between >240 and 300 days, and a steep drop at >300 days compared to previous phases. Na+ concentrations showed the lowest values at 0-60 d and the highest ones at >180-240 days, whereas Mg++ showed the highest values at >60-120 d and the lowest at >300 d. Significant correlations were found between P4 with cortisol, Cl- and K+, and cortisol with Ca++ and LDH. Significant differences in average concentrations of AST, ALT, LDH, Ca++, Mg++, and Fe++ were observed among different dairy cow breeds. Understanding the dynamic changes in hormone levels, electrolytes, and biochemical parameters during different lactation phases, while considering breed differences in dairy cows, is crucial for improving herd health management and milk production in commercial dairy farms.

Developmental programming of production and reproduction in dairy cows: V. Association of the main and interactive effects of maternal level of milk production and milk fat to protein ratio with offspring's birth weight, survival, and productive and reproductive performance from birth to the first lactation period

Level of dam milk production (DMP) and dam milk fat to protein ratio (DFPR), as an indicator of metabolic status in dairy cows, have been identified to be associated with productive and reproductive performance of the offspring. Yet whether the interaction of DMP by DFPR can be associated with performance of the offspring have not been studied to our knowledge. Therefore, the present study was conducted to investigate the association of the main and interactive effects of DMP and DFPR with offspring's birth weight, survival, milk yield and fertility. To this end, data of birth weight, culling rate, milk yield and reproductive variables of offspring born to lactating dams (n = 14,582) and data associated with DMP and DFPR during 305-day lactation were retrieved. Afterwards, offspring were classified in three categories of DMP, including DMP1 (dams with <10.00 × 103 kg of 305-day milk production), DMP2 (dams with ≥10.00 × 103 kg and <14.00 × 103 kg of 305-day milk production), DMP3 (dams with ≥14.00 × 103 kg of 305-day milk production), and three categories of DFPR, including DFPR1 (offspring born to dams with <1.00 FPR), DFPR2 (offspring born to dams with ≥1.00 and < 1.40 FPR) and DFPR3 (offspring born to dams with ≥1.40 FPR). Statistical analysis revealed no association of the interaction effect of DMP by DFPR with investigated variables in the offspring (P > 0.05). However, the main effect of DMP was positively associated with milk yield, but negatively associated with survival, age at first insemination and conception during nulliparity, and transgenerational improvement in milk yield in the offspring (P < 0.05). Moreover, the main effect of DFPR was positively associated with birth weight, survival and first service conception rate during nulliparity, but negatively associated with metabolic status and reproductive performance during primiparity in the offspring (P < 0.05). In conclusion, the present study did not find any interaction effect of DMP by DFPR on productive and reproductive variables in the offspring. This finding implicates the association of DMP with milk production in the offspring was regardless of DFPR. Moreover, this finding implies the association of DFPR with postpartum metabolic status and reproductive performance in the offspring was regardless of DMP.

Combining genetic markers, on-farm information and infrared data for the in-line prediction of blood biomarkers of metabolic disorders in Holstein cattle

BACKGROUND

Various blood metabolites are known to be useful indicators of health status in dairy cattle, but their routine assessment is time-consuming, expensive, and stressful for the cows at the herd level. Thus, we evaluated the effectiveness of combining in-line near infrared (NIR) milk spectra with on-farm (days in milk [DIM] and parity) and genetic markers for predicting blood metabolites in Holstein cattle. Data were obtained from 388 Holstein cows from a farm with an AfiLab system. NIR spectra, on-farm information, and single nucleotide polymorphisms (SNP) markers were blended to develop calibration equations for blood metabolites using the elastic net (ENet) approach, considering 3 models: (1) Model 1 (M1) including only NIR information, (2) Model 2 (M2) with both NIR and on-farm information, and (3) Model 3 (M3) combining NIR, on-farm and genomic information. Dimension reduction was considered for M3 by preselecting SNP markers from genome-wide association study (GWAS) results.

RESULTS

Results indicate that M2 improved the predictive ability by an average of 19% for energy-related metabolites (glucose, cholesterol, NEFA, BHB, urea, and creatinine), 20% for liver function/hepatic damage, 7% for inflammation/innate immunity, 24% for oxidative stress metabolites, and 23% for minerals compared to M1. Meanwhile, M3 further enhanced the predictive ability by 34% for energy-related metabolites, 32% for liver function/hepatic damage, 22% for inflammation/innate immunity, 42.1% for oxidative stress metabolites, and 41% for minerals, compared to M1. We found improved predictive ability of M3 using selected SNP markers from GWAS results using a threshold of > 2.0 by 5% for energy-related metabolites, 9% for liver function/hepatic damage, 8% for inflammation/innate immunity, 22% for oxidative stress metabolites, and 9% for minerals. Slight reductions were observed for phosphorus (2%), ferric-reducing antioxidant power (1%), and glucose (3%). Furthermore, it was found that prediction accuracies are influenced by using more restrictive thresholds (-log10(P-value) > 2.5 and 3.0), with a lower increase in the predictive ability.

CONCLUSION

Our results highlighted the potential of combining several sources of information, such as genetic markers, on-farm information, and in-line NIR infrared data improves the predictive ability of blood metabolites in dairy cattle, representing an effective strategy for large-scale in-line health monitoring in commercial herds.

Nutritional Quality and Socio-Ecological Benefits of Mare Milk Produced under Grazing Management

This review discusses the scientific evidence that supports the nutritional value of mare milk and how its properties are essentially achieved when mares are managed under grazing conditions. Mare milk's similarity with the chemical composition of human milk makes this food and its derived products not only suitable for human consumption but also an interesting food regarding human health. The contribution of horse breeding under grazing management to other socio-ecological benefits generated by equine farms is also highlighted. Both the high added value of mare milk and the socio-ecological benefits derived from pasture-based systems could be explored to improve the performance of equine farms located in arid and semi-arid areas or in regions with moderately harsh environmental conditions as equids have a strong adaptation capacity.

Developmental programming of production and reproduction in dairy cows: IV. Association of maternal milk fat and protein percentage and milk fat to protein ratio with offspring's birth weight, survival, productive and reproductive performance and AMH concentration from birth to the first lactation period

Although the association of maternal milk production with developmental programming of offspring has been investigated, there is limited information available on the relationship of maternal milk components with productive and reproductive performance of the offspring. Therefore, the present study was conducted to analyze the association of maternal milk fat and protein percentage and milk fat to protein ratio with birth weight, survival, productive and reproductive performance and AMH concentration in the offspring. In study I, data of birth weight, milk yield and reproductive variables of offspring born to lactating dams (n = 14,582) and data associated with average maternal milk fat percentage (MFP), protein percentage (MPP) and fat to protein ratio (MFPR) during 305-day lactation were retrieved. Afterwards, offspring were classified in various categories of MFP, MPP and MFPR. In study II, blood samples (n = 339) were collected from offspring in various categories of MFP, MPP and MFPR for measurement of serum AMH. Maternal milk fat percentage was positively associated with birth weight and average percentage of milk fat (APMF) and protein (APMP) and milk fat to protein ratio (FPR) during the first lactation, but negatively associated with culling rate during nulliparity in the offspring (P < 0.05). Maternal milk protein percentage was positively associated with birth weight, APMF, APMP, FPR and culling rate, but negatively associated with milk yield and fertility in the offspring (P < 0.05). Maternal FPR was positively associated with APMF and FPR, but negatively associated with culling rate, APMP and fertility in the offspring (P < 0.05). However, concentration of AMH in the offspring was not associated with MFP, MPP and MFPR (P > 0.05). In conclusion, the present study revealed that maternal milk fat and protein percentage and their ratio were associated with birth weight, survival, production and reproduction of the offspring. Yet it was a preliminary research and further studies are required to elucidate the mechanisms underlying these associations.

Combined Metabolomics and Biochemical Analyses of Serum and Milk Revealed Parity-Related Metabolic Differences in Sanhe Dairy Cattle

The production performance of dairy cattle is closely related to their metabolic state. This study aims to provide a comprehensive understanding of the production performance and metabolic features of Sanhe dairy cattle across different parities, with a specific focus on evaluating variations in milk traits and metabolites in both milk and serum. Sanhe dairy cattle from parities 1 to 4 (S1, n = 10; S2, n = 9; S3, n = 10; and S4, n = 10) at mid-lactation were maintained under the same feeding and management conditions. The milk traits, hydrolyzed milk amino acid levels, serum biochemical parameters, and serum free amino acid levels of the Sanhe dairy cattle were determined. Multiparous Sanhe dairy cattle (S2, S3, and S4) had a greater milk protein content, lower milk lactose content, and lower solids-not-fat content than primiparous Sanhe dairy cattle (S1). Moreover, S1 had a higher ratio of essential to total amino acids (EAAs/TAAs) in both the serum and milk. The serum biochemical results showed the lower glucose and total protein levels in S1 cattle were associated with milk quality. Furthermore, ultra-high-resolution high-performance liquid chromatography with tandem MS analysis (UPLC-MS/MS) identified 86 and 105 differential metabolites in the serum and milk, respectively, and these were mainly involved in amino acid, carbohydrate, and lipid metabolism. S1 and S2/S3/S4 had significantly different metabolic patterns in the serum and milk, and more vitamin B-related metabolites were significantly higher identified in S1 than in multiparous cattle. Among 36 shared differential metabolites in the serum and milk, 10 and 7 metabolites were significantly and strongly correlated with differential physiological indices, respectively. The differential metabolites identified were enriched in key metabolic pathways, illustrating the metabolic characteristics of the serum and milk from Sanhe dairy cattle of different parities. L-phenylalanine, dehydroepiandrosterone, and linoleic acid in the milk and N-acetylornithine in the serum could be used as potential marker metabolites to distinguish between Sanhe dairy cattle with parities of 1-4. In addition, a metabolic map of the serum and milk from the three aspects of carbohydrates, amino acids, and lipids was created for the further analysis and exploration of their relationships. These results reveal significant variations in milk traits and metabolites across different parities of Sanhe dairy cattle, highlighting the influence of parity on the metabolic profiles and production performance. Tailored nutritional strategies based on parity-specific metabolic profiles are recommended to optimize milk production and quality in Sanhe cattle.

Developmental programming of reproduction in the female animal

Successful reproduction is a cornerstone in food animal industry in order to sustain food production for human. Therefore, various methods focusing on genetics and postnatal environment have been identified and applied to improve fertility in livestock. Yet there is evidence indicating that environmental factors during prenatal and/or neonatal life can also impact the function of reproductive system and fertility in the animals during adulthood, which is called the developmental programming of reproduction. The current review summarizes data associated with the developmental origins of reproduction in the female animals. In this regard, this review focuses on the effect of plane of nutrition, maternal body condition, hypoxia, litter size, maternal age, parity, level of milk production and milk components, lactocrine signaling, stress, thermal stress, exposure to androgens, endocrine disrupting chemicals, mycotoxins and pollutants, affliction with infection and inflammation, and maternal gut microbiota during prenatal and neonatal periods on the neuroendocrine system, puberty, health of reproductive organs and fertility in the female offspring. It is noteworthy that these prenatal and neonatal factors do not always exert their effects on the reproductive performance of the female by compromising the development of organs directly related to reproductive function such as hypothalamus, pituitary, ovary, oviduct and uterus. Since they can impair the development of non-reproductive organs and systems modulating reproductive function as well (e.g., metabolic system and level of milk yield in dairy animals). Furthermore, when these factors affect the epigenetics of the offspring, their adverse effects will not be limited to one generation and can transfer transgenerationally. Hence, pinpointing the factors influencing developmental programming of reproduction and considering them in management of livestock operations could be a potential strategy to help improve fertility in food animals.

Dietary supplementation of Aloe vera extract modulates rumen microbes and improves the functional food value of milk by altering phenolic content, antioxidant capacity, and fatty acid profile in lactating goats

Twenty-four cross-breed (Alpine × Beetal) lactating goats (average body weight: 37.5 ± 2.7 kg and milk yield: 1.78 ± 0.31 kg/day) were chosen for the ninety days duration of the experiment and divided into three groups following a completely randomized design. Group I acted as control (T0) and received only a basal diet as per requirement, whereas group II (T1) and group III (T2) received basal diet added with Aloe vera extract at 2% and 4% of dry matter intake (DMI), respectively. Total phenolic compounds (TPC) and milk antioxidant status were higher (p < 0.05) in T1 and T2 than T0. Relative abundance of methanogen, protozoa, Butyrivibrio proteoclasticus, and Ruminococcus flavefaciens in the rumen were lower, while Butyrivibrio fibrisolvens population was higher (p < 0.05) in T2 and T1 compared to T0. Saturated fatty acids levels in milk were lower, whereas different polyunsaturated fatty acids levels were higher (p < 0.05) in T1 and T2 than T0. Nutritional indices of milk increased in both supplemented groups. Overall, it may be concluded that dietary supplementation of Aloe vera extract at 2% and 4% of DMI may enhance the functional characteristics of milk by boosting TPC and antioxidant status, as well as the FA profile and nutritional quality indices of milk fat.

In-Line Registered Milk Fat-to-Protein Ratio for the Assessment of Metabolic Status in Dairy Cows

This study endeavors to ascertain alterations in the in-line registered milk fat-to-protein ratio as a potential indicator for evaluating the metabolic status of dairy cows. Over the study period, farm visits occurred biweekly on consistent days, during which milk composition (specifically fat and protein) was measured using a BROLIS HerdLine in-line milk analyzer (Brolis Sensor Technology, Vilnius, Lithuania). Clinical examinations were performed at the same time as the farm visits. Blood was drawn into anticoagulant-free evacuated tubes to measure the activities of GGT and AST and albumin concentrations. NEFA levels were assessed using a wet chemistry analyzer. Using the MediSense and FreeStyle Optium H systems, blood samples from the ear were used to measure the levels of BHBA and glucose in plasma. Daily blood samples were collected for BHBA concentration assessment. All samples were procured during the clinical evaluations. The cows were categorized into distinct groups: subclinical ketosis (SCK; n = 62), exhibiting elevated milk F/P ratios without concurrent clinical signs of other post-calving diseases; subclinical acidosis (SCA; n = 14), characterized by low F/P ratios (<1.2), severe diarrhea, and nondigestive food remnants in feces, while being free of other post-calving ailments; and a healthy group (H; n = 20), comprising cows with no clinical indications of illness and an average milk F/P ratio of 1.2. The milk fat-to-protein ratios were notably higher in SCK cows, averaging 1.66 (±0.29; p < 0.01), compared to SCA cows (0.93 ± 0.1; p < 0.01) and healthy cows (1.22). A 36% increase in milk fat-to-protein ratio was observed in SCK cows, while SCA cows displayed a 23.77% decrease. Significant differences emerged in AST activity, with SCA cows presenting a 26.66% elevation (p < 0.05) compared to healthy cows. Moreover, SCK cows exhibited a 40.38% higher NEFA concentration (p < 0.001). A positive correlation was identified between blood BHBA and NEFA levels (r = 0.321, p < 0.01), as well as a negative association between BHBA and glucose concentrations (r = -0.330, p < 0.01). Notably, AST displayed a robust positive correlation with GGT (r = 0.623, p < 0.01). In light of these findings, this study posits that milk fat-to-protein ratio comparisons could serve as a non-invasive indicator of metabolic health in cows. The connections between milk characteristics and blood biochemical markers of lipolysis and ketogenesis suggest that these markers can be used to check the metabolic status of dairy cows on a regular basis.

Beef cows' performance and metabolic response to short nutritional challenges in different months of lactation

Lactating cows can react to changes in nutrient availability with a range of behavioural and physiological mechanisms, which may differ among lactation stages. We investigated the effects of short feed restriction and refeeding periods on beef cows' performance and metabolic status in different months of lactation. For this, Parda de Montaña beef cows [n = 31; 626 ± 47.7 kg body weight (BW)] were subjected to short nutritional restriction and refeeding cycles, which were repeated in months 2, 3 and 4 of lactation. Each month, cows were consecutively fed a diet to meet 100% of their energy and protein requirements during a 4-day basal period, 55% during a 4-day restriction period, and again 100% during a 4-day refeeding period. The performance (energy balance, BW, milk yield and composition) and plasma metabolite concentrations (glucose, non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), urea and malondialdehyde) were measured daily. Most of the traits were significantly affected by the interaction between feeding period and lactation month. Feed restriction induced milk yield loss, decreased milk protein and increased milk urea contents to different extents. The plasma NEFA concentrations rose with restriction in months 2, 3 and 4 but BHB and urea concentrations increased only in month 4. Most of these metabolites lowered to basal values during refeeding. These results suggest that beef cows use different adaptation strategies to cope with nutritional challenges as lactation advances, body fat mobilisation predominates in early lactation and protein catabolism prevails at later stages.

Hepatic Lipidosis in Ruminants

Hepatic lipidosis (ie, fatty liver) occurs primarily during the first weeks of lactation in dairy cows because of excessive lipolysis overwhelming the concomitant capacity for beta-oxidation and hepatic export of triglycerides. Besides economic losses due to reduced lactational and reproductive performance, close associations with concomitantly occurring infectious and metabolic health disorders, in particular ketosis, exist. Hepatic lipidosis is not only a consequence from the postpartal negative energy balance but also acts as a disease component for further health disorders.

Integrating on-farm and genomic information improves the predictive ability of milk infrared prediction of blood indicators of metabolic disorders in dairy cows

BACKGROUND

Blood metabolic profiles can be used to assess metabolic disorders and to evaluate the health status of dairy cows. Given that these analyses are time-consuming, expensive, and stressful for the cows, there has been increased interest in Fourier transform infrared (FTIR) spectroscopy of milk samples as a rapid, cost-effective alternative for predicting metabolic disturbances. The integration of FTIR data with other layers of information such as genomic and on-farm data (days in milk (DIM) and parity) has been proposed to further enhance the predictive ability of statistical methods. Here, we developed a phenotype prediction approach for a panel of blood metabolites based on a combination of milk FTIR data, on-farm data, and genomic information recorded on 1150 Holstein cows, using BayesB and gradient boosting machine (GBM) models, with tenfold, batch-out and herd-out cross-validation (CV) scenarios.

RESULTS

The predictive ability of these approaches was measured by the coefficient of determination (R²). The results show that, compared to the model that includes only FTIR data, integration of both on-farm (DIM and parity) and genomic information with FTIR data improves the R² for blood metabolites across the three CV scenarios, especially with the herd-out CV: R² values ranged from 5.9 to 17.8% for BayesB, from 8.2 to 16.9% for GBM with the tenfold random CV, from 3.8 to 13.5% for BayesB and from 8.6 to 17.5% for GBM with the batch-out CV, and from 8.4 to 23.0% for BayesB and from 8.1 to 23.8% for GBM with the herd-out CV. Overall, with the model that includes the three sources of data, GBM was more accurate than BayesB with accuracies across the CV scenarios increasing by 7.1% for energy-related metabolites, 10.7% for liver function/hepatic damage, 9.6% for oxidative stress, 6.1% for inflammation/innate immunity, and 11.4% for mineral indicators.

CONCLUSIONS

Our results show that, compared to using only milk FTIR data, a model integrating milk FTIR spectra with on-farm and genomic information improves the prediction of blood metabolic traits in Holstein cattle and that GBM is more accurate in predicting blood metabolites than BayesB, especially for the batch-out CV and herd-out CV scenarios.

Metabolic and physiological adaptations to first and second lactation in Holstein dairy cows

Huge differences exist between cow yields and body sizes during their first and second lactations. The transition period is the most critical and investigated phase of the lactation cycle. We compared metabolic and endocrine responses between cows at different parities during the transition period and early lactation. Eight Holstein dairy cows were monitored at their first and second calving during which they were reared under the same conditions. Milk yield, dry matter intake (DMI), and body weight (BW) were regularly measured, and energy balance, efficiency, and lactation curves were calculated. Blood samples were collected on scheduled days from -21 d relative to calving (DRC) to 120 DRC for the assessment of metabolic and hormonal profiles (biomarkers of metabolism, mineral status, inflammation, and liver function). Large variations in the period in question for almost all variables investigated were observed. Compared with their first lactation, cows during their second lactation had higher DMI (+15%) and BW (+13%), their milk yield was greater (+26%), lactation peak was higher and earlier (36.6 kg/d at 48.8 DRC vs. 45.0 kg/d at 62.9 DRC), but persistency was reduced. Milk fat, protein, and lactose contents were higher during the first lactation and coagulation properties were better (higher titratable acidity, faster and firmer curd formation). Postpartum negative energy balance was more severe the during the second lactation (1.4-fold at 7 DRC) and plasma glucose was lower. Circulating insulin and insulin-like growth factor-1 were lower in second-calving cows during the transition period. At the same time, markers of body reserve mobilization (β-hydroxybutyrate and urea) increased. Moreover, albumin, cholesterol, and γ-glutamyl transferase were higher during second lactation, whereas bilirubin and alkaline phosphatase were lower. The inflammatory response after calving was not different, as suggested by the similar haptoglobin concentrations and only transient differences in ceruloplasmin. Blood growth hormone did not differ during the transition period but was lower during the second lactation at 90 DRC, whereas circulating glucagon was higher. These results agree with the differences in milk yield and confirmed the hypothesis of a different metabolic and hormonal status between the first and second lactation partly related to different degrees of maturity.

Microbiome-Metabolomics Insights into the Milk of Lactating Dairy Cows to Reveal the Health-Promoting Effects of Dietary Citrus Peel Extracts on the Mammary Metabolism

The effects of dietary supplementation with citrus peel extract (CPE) on milk biochemical parameters, milk bacterial community, and milk metabolites were evaluated. Eight lactating cows were allocated to a replicated 4 × 4 Latin square. Experimental treatments included the control diet (CON), and CON supplemented with CPE at 50 g/d (CPE50), 100 g/d (CPE100), and 150 g/d (CPE150). Supplementing with CPE linearly decreased milk interleukin-6 and malondialdehyde concentrations and linearly increased lysozyme activity and 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity. Compared with CON, the milk of CPE150 cows had fewer abundances of several opportunistic pathogens and psychrotrophic bacteria, such as Escherichia-Shigella, Sphingobacterium, Alcaligenes, Stenotrophomonas, and Ochrobactrum. Supplementing with CPE significantly altered the metabolic profiling in the milk. The metabolites of flavonoids were enriched in the milk of cows fed CPE150, while some proinflammation compounds were decreased compared with CON. Correlation analysis showed that the change in the bacterial community might partly contribute to the alteration in the expression of milk cytokines. In conclusion, CPE exerts health-promoting effects (e.g., antioxidant, anti-microbial, and anti-inflammatory) in the mammary metabolism of cows due to its flavonoid compounds, which also provide additional value in terms of milk quality improvement.

The teat cup detachment level affects milking performance in an automatic milking system with teat cleaning and milking in the same teat cup

The goal of the present study was to determine the best quarter milk flow for teat cup detachment depending on lactational stage and milking interval to optimize the milking process in automatic milking systems (AMS). Milking characteristics and post-milking teat condition were recorded in an AMS with all actions from teat cleaning to post-milking teat dipping occurring in the same teat cup and liner (GEA DairyRobot R9500). In 24 dairy cows, 12 in early (<80 DIM) and 12 in late lactation (>180 DIM), 294 milkings were recorded during 12 consecutive days. Teat cup detachment was set at a quarter milk flow of 50, 87.5 or 125 g/min. Voluntary milking intervals varied similarly in cows in early (6.1-14.8 h) and late lactation (6.3-15.7 h). Total milk yield, milk production per h and average milk flow were higher in early than in late lactation cows. Total milk yield per milking did not differ between detachment levels. The mean milking time was reduced by up to 1.5 min at the highest compared to the lowest detachment level mainly in early lactation cows (P < 0.05). However, no significant effect of the detachment level on milking time was observed at milking intervals >10 h. Average milk flow was higher at milking intervals >10 h than ≤10 h (P < 0.05). In the early lactation cows (only) the average milk flow increased with higher detachment levels (P < 0.05). Teat condition did not differ among detachment settings or milking intervals. In conclusion, teat cup detachment up to 125 g/min reduces milking time in both early and late lactation without a loss of milk yield or affecting the teat condition. Combined with a higher average milk flow through avoiding too short milking intervals, the total milking time and hence stall occupancy can be optimized by early teat cup detachment.

The effect of pre-calving injection of trace mineral supplements on periparturient disease incidence in pasture based dairy cows

Trace minerals, have a role in immune function and a trace mineral supplement (TMS) can improve animal health in dairy herds. This prospective randomised clinical study assessed whether subcutaneous injection of 5.5 mL of TMS (40 mg zinc, 10 mg manganese, 5 mg selenium, 15 mg copper per mL), 14-28 days before planned start of calving (PSC) reduced clinical mastitis (CM), subclinical mastitis (SCM) and purulent vaginal discharge (PVD). From four farms, half of 1700 cows stratified on somatic cell count, age and breed were randomly allocated to treatment or no treatment. Occurrence of CM from - 7 to PSC + 100 days, SCM at PSC + 60 days and PVD at PSC + 24 days was analysed using survival analysis and Bayesian generalised mixed multivariable models. From -7 to PSC +30 days, TMS reduced the adjusted hazard ratio (HR) for CM at quarter and cow level (P < 0.001), with no evidence for an effect beyond 30 days. The adjusted OR (and 95% highest density interval, HDI) for the effect of TMS on CM from -7 to PSC +30 days was 0.40 (95% HDI, 0.26-0.63) at quarter level, 0.51 (95% HDI, 0.38-0.69) at cow level and for SCM, 0.72 (95% HDI, 0.54-0.95). The difference in CM incidence from TMS at the cow level was -2.0% (95% HDI, -3.4 to -1.1%) and -1.2% (95% HDI, -3.2 to - 0.6%) at quarter level. No clear effect was identified of TMS on cumulative incidence of PVD.

Supplementation of Aloe vera extract in lactating goats' diet: effects on rumen fermentation efficiency, nutrient utilization, lactation performance, and antioxidant status

The present work was conducted to investigate the effects of supplementing Aloe vera extract on rumen fermentation efficiency, nutrient utilization, lactation performance, and antioxidant status of goats. Twenty-four crossbreed lactating goats (Alpine × Beetal) were divided into three experimental groups (AV0, AV2, and AV4). AV0 had no supplementation, groups AV2 and AV4 received ready to feed aqueous extract of Aloe vera at 20 and 40 g/kg dry matter intake, respectively, along with basal diet and experiment lasted for 100 days. Average DMI did not vary (P > 0.05) among treatment groups; however, the metabolic bodyweight of AV4 was significantly lower (P < 0.05) than the AV0 and AV2 groups (AV0 = AV2 > AV4). Intake and digestibility of DM, OM, CP, NDF, ADF, and EE were unaffected (P > 0.05) by Aloe vera supplementation. The milk production, yield of milk fat, protein, lactose, and solid not fat (SNF) of goats in the AV4 group were significantly higher (P < 0.05) than other groups (AV4 > AV2 = AV0). The activity of superoxide dismutase and catalase enzymes and levels of plasma ferric reducing total antioxidant power were high (P < 0.01) in the Aloe vera supplemented group (AV4 = AV2 > AV0). There was no significant difference (P = 0.979) in the pH, acetic acid (P = 0.449), and butyric acid (P = 0.864) concentration of the rumen liquor among the treatment groups. The propionic acid concentration was similar between AV2 and AV4 and significantly higher (P = 0.024) than the AV0 group (AV4 = AV2 > AV0). Moreover, C2:C3 values were significantly lower (P = 0.037) in the AV4 group compared to the control (AV0). Thus, Aloe vera supplementation enhanced milk yield, propionic acid production, and antioxidant status without affecting nutrient utilization; however, results were better in the AV4 group. The inclusion of Aloe vera at 40 g/kg of DMI would improve the rumen fermentation efficiency, lactation performance, and overall health status of the dairy goats.

Nuclear factor erythroid 2-related factor 2 protects bovine mammary epithelial cells against free fatty acid-induced mitochondrial dysfunction in vitro

Bovine mammary epithelial cells undergo an increase in metabolic rate, mitochondrial dysfunction, and oxidative stress after calving. Nuclear factor erythroid 2-related factor 2 (NFE2L2), a master regulator of cellular redox homeostasis, plays crucial roles in the regulation of mitochondrial function. The objective of this study was to investigate the role of NFE2L2 on mitochondrial function in bovine mammary epithelial cells under hyperlipidemic conditions. Three experiments were conducted as follows: (1) the immortalized bovine mammary epithelial cell line MAC-T was treated with various concentrations of free fatty acids (FFA; 0, 0.6, 1.2, or 2.4 mM) for 24 h to induce stress; (2) MAC-T cells were transfected with small interfering RNA targeting NFE2L2 (si-NFE2L2) and scrambled nontarget negative control (si-Control) for 48 h; and (3) MAC-T cells were pretreated with 10 μM sulforaphane (SFN), an activator of NFE2L2, for 24 h followed by treatment with 1.2 mM FFA for an additional 24 h. Results indicated that exogenous FFA challenge induced linear and quadratic increases in concentrations of mitochondrial reactive oxygen species (ROS). Compared with 0 mM FFA, mitochondrial membrane potential, mRNA abundance of oxidative phosphorylation complexes (CO I-V), protein abundance of nuclear respiratory factor 1 (NRF1), peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α), mitochondrial transcription factor A (TFAM), and NFE2L2 along with the contents of ATP, mitochondrial DNA (mtDNA), and total mitochondria were greater in the MAC-T challenged with 0.6 mM FFA group, but lower in the 1.2 and 2.4 mM FFA cultures. Knockdown of NFE2L2 via small interfering RNA led to greater mitochondrial ROS content and lower mitochondrial membrane potential along with contents of ATP, mtDNA, and total mitochondria. The SFN pretreatment upregulated protein abundance of NFE2L2 and attenuated the downregulation of NFE2L2 induced by FFA. Pretreatment with SFN attenuated the downregulation induced by FFA of PGC-1α, NRF1, and TFAM protein abundance along with contents of mtDNA and total mitochondria. Furthermore, SFN pretreatment attenuated the upregulation of mitochondrial ROS content, the downregulation of mitochondrial membrane potential, and the decreases in ATP, mtDNA, and mitochondrial content induced by FFA. Overall, data indicated that FFA inhibit NFE2L2, resulting in mitochondrial dysfunction and ROS production in bovine mammary epithelial cells. Thus, NFE2L2 may be a promising therapeutic target against metabolic challenge-driven mitochondrial dysfunction and oxidative stress in bovine mammary epithelial cells.

Invited Review: Ketosis Diagnosis and Monitoring in High-Producing Dairy Cows

This work reviews the current impact and manifestation of ketosis (hyperketonemia) in dairy cattle, emphasizing the practical use of laboratory methods, field tests, and milk data to monitoring this disease. Ketosis is a major issue in high-producing cows, easily reaching a prevalence of 20% during early postpartum when the negative energy balance is well established. Its economic losses, mainly related to decreasing milk yield, fertility, and treatment costs, have been estimated up to €250 per case of ketosis/year, which can double if associated diseases are considered. A deep relationship between subclinical or clinical ketosis and negative energy balance and related production diseases can be observed mainly in the first two months postpartum. Fourier transform infrared spectrometry methods gradually take place in laboratory routine to evaluates body ketones (e.g., beta-hydroxybutyrate) and probably will accurately substitute cowside blood and milk tests at a farm in avenir. Fat to protein ratio and urea in milk are largely evaluated each month in dairy farms indicating animals at risk of hyperketonemia. At preventive levels, other than periodical evaluation of body condition score and controlling modifiable or identifying non-modifiable risk factors, the ruminatory activity assessment during the peripartum seems to be a valuable tool at farms. We conclude that a technological advance progressively takes place to mitigate the effects of these metabolic diseases, which challenge the high-yielding cows.

Transcription factor EB (TFEB)-mediated autophagy protects bovine mammary epithelial cells against H2O2-induced oxidative damage in vitro

Background

Bovine mammary epithelial cells after calving undergo serious metabolic challenges and oxidative stress both of which could compromise autophagy. Transcription factor EB (TFEB)-mediated autophagy is an important cytoprotective mechanism against oxidative stress. However, effects of TFEB-mediated autophagy on the oxidative stress of bovine mammary epithelial cells remain unknown. Therefore, the main aim of the study was to investigate the role of TFEB-mediated autophagy in bovine mammary epithelial cells experiencing oxidative stress.

Results

H₂O₂ challenge of the bovine mammary epithelial cell MAC-T increased protein abundance of LC3-II, increased number of autophagosomes and autolysosomes while decreased protein abundance of p62. Inhibition of autophagy via bafilomycin A1 aggravated H₂O₂-induced reactive oxygen species (ROS) accumulation and apoptosis in MAC-T cells. Furthermore, H₂O₂ treatment triggered the translocation of TFEB into the nucleus. Knockdown of TFEB by siRNA reversed the effect of H₂O₂ on protein abundance of LC3-II and p62 as well as the number of autophagosomes and autolysosomes. Overexpression of TFEB activated autophagy and attenuated H₂O₂-induced ROS accumulation. Furthermore, TFEB overexpression attenuated H₂O₂-induced apoptosis by downregulating the caspase apoptotic pathway.

Conclusions

Our results indicate that activation of TFEB mediated autophagy alleviates H₂O₂-induced oxidative damage by reducing ROS accumulation and inhibiting caspase-dependent apoptosis.

Effects of a Multicomponent Herbal Extract on the Course of Subclinical Ketosis in Dairy Cows - a Blinded Placebo-controlled Field-study

A blinded placebo-controlled multi-center on-farm trial was conducted in dairy cows with subclinical ketosis to investigate effects of a multicomponent herbal extract. Blood ketone levels were measured weekly in early lactating cows from 16 Swiss herds. Cows were subclassified based on their initial blood-β-hydroxybutyrate levels (≥ 1.0 [KET-low, 84 cows] and > 1.2 mmol/L [KET-high, 39 cows]) and randomly distributed to 3 groups treated orally with herbal extract containing Camellia sinensis, Cichcorium intybus, Gentiana lutea, Glycyrrhiza glabra, Taraxacum officinale, Trigonella foenum-graecum, and Zingiber officinale, sodium propionate, or placebo twice a day for 5 days. Milk yield, milk acetone, blood-β-hydroxybutyrate, glucose, nonesterified fatty acids, gamma-glutamyl transferase, and glutamate dehydrogenase were analyzed over 2 wk. Linear mixed effect models were used for data analysis. No effects were found for nonesterifed fatty acids, gamma-glutamyl transferase, and glucose. Significantly higher glutamate dehydrogenase (29.71 U/L) values were found in herbal extract-treated animals compared to sodium propionate on day 7 (22.33 U/L). By trend, higher blood-β-hydroxybutyrate levels (1.36 mmol/L) were found in the placebo group of KET-high-cows on day 14 compared to the sodium propionate group (0.91 mmol/L). Milk yields of all treatment groups increased. Milking time and treatment showed a significant interaction for milk acetone: sodium propionate led to an immediate decrease, whereas herbal extracts resulted in a milk acetone decrease from day 7 on, reaching significantly lower milk acetone on day 14 (3.17 mg/L) when compared to placebo (4.89 mg/L). In conclusion, herbal extracts and sodium propionate are both likely to improve subclinical ketosis in dairy cows, however, by different modes of action.

Opportunities and limitations of milk mid-infrared spectra-based estimation of acetone and β-hydroxybutyrate for the prediction of metabolic stress and ketosis in dairy cows

Subclinical (SCK) and clinical (CK) ketosis are metabolic disorders responsible for big losses in dairy production. Although Fourier-transform mid-infrared spectrometry (FTIR) to predict ketosis in cows exposed to great metabolic stress was studied extensively, little is known about its suitability in predicting hyperketonemia using individual samples, e.g. in small dairy herds or when only few animals are at risk of ketosis. The objective of the present research was to determine the applicability of milk metabolites predicted by FTIR spectrometry in the individual screening for ketosis. In experiment 1, blood and milk samples were taken every two weeks after calving from Holstein (n = 80), Brown Swiss (n = 72) and Swiss Fleckvieh (n = 58) cows. In experiment 2, cows diagnosed with CK (n = 474) and 420 samples with blood β-hydroxybutyrate [BHB] <1.0 mmol/l were used to investigate if CK could be detected by FTIR-predicted BHB and acetone from a preceding milk control. In experiment 3, correlations between data from an in farm automatic milk analyser and FTIR-predicted BHB and acetone from the monthly milk controls were evaluated. Hyperketonemia occurred in majority during the first eight weeks of lactation. Correlations between blood BHB and FTIR-predicted BHB and acetone were low (r = 0.37 and 0.12, respectively, P < 0.0001), as well as the percentage of true positive values (11.9 and 16.6%, respectively). No association of FTIR predicted ketone bodies with the interval of milk sampling relative to CK diagnosis was found. Data obtained from the automatic milk analyser were moderately correlated with the same day FTIR-predicted BHB analysis (r = 0.61). In conclusion, the low correlations with blood BHB and the small number of true positive samples discourage the use of milk mid-infrared spectrometry analyses as the only method to predict hyperketonemia at the individual cow level.

Metabolic status is associated with the recovery of milk somatic cell count and milk secretion after lipopolysaccharide-induced mastitis in dairy cows

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.

Review: Metabolic challenges in lactating dairy cows and their assessment via established and novel indicators in milk

The increasing lactational performance of dairy cows over the last few decades is closely related to higher nutritional requirements. The decrease in dry matter intake during the peripartal period results in a considerable mobilisation of body tissues (mainly fat reserves and muscle mass) to compensate for the prevailing lack of energy and nutrients. Despite the activation of adaptive mechanisms to mobilise nutrients from body tissues for maintenance and milk production, the increased metabolic load is still a risk factor for animal health. The prevalence of production diseases, particularly subclinical ketosis is high in the early lactation period. Increased β-hydroxybutyrate (BHB) concentrations further depress gluconeogenesis, feed intake and the immune system. Despite a variety of adaptation responses to nutrient and energy deficit that exists among dairy cows, an early and non-invasive detection of developing metabolic disorders in milk samples would be useful. The frequent and regular milking process of dairy cows creates the ability to obtain samples at any stage of lactation. Routine identification of biomarkers accurately characterising the physiological status of an animal is crucial for decisive strategies. The present overview recapitulates established markers measured in milk that are associated with metabolic health of dairy cows. Specifically, measurements of milk fat, protein, lactose and urea concentrations are evaluated. Changes in the ratio of milk fat to protein may indicate an increased risk for rumen acidosis and ketosis. The costly determination of individual fatty acids in milk creates barriers for grouping of fatty acids into saturated, mono- and polyunsaturated fatty acids. Novel approaches include the potential of mid-IR (MIR) based predictions of BHB and acetone in milk, although the latter are not directly measured, but only estimated via indirect associations of concomitantly altered milk composition during (sub)clinical ketosis. Although MIR-based ketone body concentrations in milk are not suitable to monitor the metabolic status of the individual cow, they provide an estimate of the overall herd or specific groups of animals earlier in a particular stage of lactation. Management decisions can be made earlier and animal health status improved by adjusting diet composition.

Intramammary pressure and udder firmness during a 72-h interruption of milking to simulate dry-off, with and without feed restriction

The goal of the present study was to quantify the increase of intramammary pressure (IMP) in dry-off during an extended milking interval of 72 h. In particular, we tested the hypothesis that feed restriction (no concentrate and roughage with reduced energy) causes earlier cessation of milk secretion and a lower IMP than continued feeding of the lactational diet. In addition to repeated IMP measurements, we tested a noninvasive method that records udder firmness (UF) via external application of pressure on the udder. Two experimental groups consisted of 10 Holstein cows each, with a daily milk yield of 20 to 25 kg. The restricted group (RG) was changed to restricted feeding on the afternoon of the final milking (0 h), whereas late-lactation feeding was continued in the control group (CG). Both IMP and UF were measured before and after the final milking immediately before milking was stopped for 72 h. These measurements represented IMP and UF levels at 10 h and 0 h milking intervals, respectively. Further measurements were performed at 18, 24, 30, 36, 42, 48, and 72 h after final milking. Milk samples (2 mL) were taken through the IMP catheter at each sampling event, for analysis of somatic cell count (SCC) and serum albumin (SA). Both IMP and UF increased with time, and both parameters peaked at 30 h in CG and at 24 h in RG. The mean IMP from 18 to 72 h, compared with the 10-h IMP (normal milking interval) was higher in CG than in RG. The duration of elevated IMP and UF was prolonged in CG compared with RG (>36 h vs. 12 h). The Pearson correlation between IMP and UF was r = 0.67. Thus, the noninvasive measurement of UF is suitable to replace invasive IMP measurements. However, due to individual differences in udder shape, the correlation between UF and IMP was too low to predict exact IMP levels using UF. Both SCC (presented as logSCC) and SA increased after the final milking until the end of the experiment. The mean increase from 18 to 72 h, compared with levels immediately after final milking, was higher in CG than in RG for SCC but did not differ between treatments for SA. In conclusion, feed restriction causes a faster cessation of milk secretion and therefore limits the increase of IMP at dry-off.

Invited review: Metabolic challenges and adaptation during different functional stages of the mammary gland in dairy cows: Perspectives for sustainable milk production

Milk production of dairy cows has increased markedly during recent decades and continues to increase further. The evolutionarily conserved direction of nutrients to the mammary gland immediately after calving provided the basis for successful selective breeding toward higher performance. Considerable variation in adaptive responses toward energy and nutrient shortages exists; however, this variation in adaptability recently gained interest for identifying more metabolically robust dairy cows. Metabolic challenges during periods of high milk production considerably affect the immune system, reproductive performance, and product quality as well as animal welfare. Moreover, growing consumer concerns need to be taken into consideration because the public perception of industrialized dairy cow farming, the high dependency on feed sources suitable for human nutrition, and the apparently abundant use of antibiotics may affect the sales of dairy products. Breeding for high yield continues, but the metabolic challenges increasingly come close to the adaptational limits of meeting the mammary gland's requirements. The aim of the present review is to elucidate metabolic challenges and adaptational limitations at different functional stages of the mammary gland in dairy cows. From the challenges and adaptational limitations, we derive perspectives for sustainable milk production. Based on previous research, we highlight the importance of metabolic plasticity in adaptation mechanisms at different functional stages of the mammary gland. Metabolic adaptation and plasticity change among developing, nonlactating, remodeling, and lactational stages of the mammary gland. A higher metabolic plasticity in early-lactating dairy cows could be indicative of resilience, and a high performance level without an extraordinary occurrence of health disorders can be achieved.

Prevalence of subclinical ketosis and production diseases in dairy cows in Central and South America, Africa, Asia, Australia, New Zealand, and Eastern Europe

Subclinical ketosis (SCK) and periparturient diseases considerably account for economic and welfare losses in dairy cows. The majority of scientific reports investigating the prevalence of SCK and production diseases are based on empirical studies conducted in Western Europe and North America. The present study surveyed the prevalence of SCK and production-related clinical diseases in early lactating cows in various countries across the world other than those in North America and Western Europe. Twelve countries of South and Central America (Argentina, Brazil, Chile, Colombia, Mexico), Africa (South Africa), Asia (Thailand, China), Eastern Europe (Russia, Ukraine), Australia, and New Zealand were assessed, and data from a total of 8,902 cows kept at 541 commercial dairy farms were obtained. A minimum of five cows per farm were blood sampled and examined once after parturition up to day 21 of lactation. Blood concentration of β-hydroxybutyrate was measured (threshold for SCK: 1.2 mmol/L), and the presence of production-related diseases such as milk fever, retained placenta, mastitis, metritis, displaced abomasum, lameness, and clinical ketosis was recorded. More than 95% of all cows were examined in their second week of lactation. Across all investigated countries, the SCK prevalence was 24.1%, ranging from 8.3% up to 40.1%. The prevalence of production-related diseases detected during the first 21 d of lactation was relatively low (<5%). Calculated odds ratios did not indicate an elevated risk for production diseases in cows with SCK. Despite differences in production systems across countries and variation between individual farms within a region, the present study data on SCK prevalence align with observations in Western European and North American dairy herds. At the very early stage of sampling and clinical examination for detection of SCK, it cannot be excluded that certain production diseases such as displaced abomasum, lameness, and mastitis have developed later.