Cows In Lactation Research Articles

Transcriptomics reveals the regulatory mechanisms of circRNA in the muscle tissue of cows with ketosis postpartum.

The transition period from late pregnancy to early lactation in dairy cows involves significant metabolic changes to cope with the challenges related to energy metabolism. Muscle tissue, as the largest energy-metabolizing tissue in dairy cows, plays a crucial role in energy metabolism. Furthermore, circular RNAs (circRNAs) have been shown to play key roles in various biological events. However, the regulatory mechanisms of energy metabolism and muscle cells mediated by circRNAs in the muscle tissue of ketotic dairy cows remain unclear. Here, we identified a total of 5103 circRNAs in the muscle tissue of ketosis-affected cows. Among these, compared to healthy cows, 57 circRNAs were differentially expressed in the muscle tissue of ketosis-affected cows, with 39 upregulated and 18 downregulated. Functional enrichment analysis based on the source genes of circRNAs indicated that circ-30,628 is closely related to carbon metabolism, and circ-CoQ2 is associated with mitochondrial energy metabolism. Given the sponge effect of circRNAs on miRNAs, we further predicted the network relationships of downstream miRNAs and mRNAs of circ-30,628 and circ-CoQ2, and found that their downstream target genes are involved in signaling pathways such as MAPK, Wnt, FoxO, and autophagy, which is associated with the proliferation, differentiation, energy metabolism, oxidative stress, and mitochondrial function of muscle cells. In summary, these findings provide a theoretical basis for understanding the functions of circRNAs regulating energy metabolism in the muscle tissue of ketosis-affected cows, thereby reducing the accumulation of ketone bodies to prevent the occurrence of ketosis in dairy cows.

Can fecal characteristics be used to predict the digestibility of certain macro minerals in dry and lactating cows?

This study aims to evaluate the relationship between mineral digestibility and fecal characteristics and compare digestibility in dry and late-lactating cows. A total of 107 multiparous Holstein and Simmental cows were included, with 66 cows in late lactation and 41 cows in the dry period. The apparent digestibility of key macro minerals, dry matter content in feces, dirtiness scores, fecal characteristics, and serum macro mineral levels were determined. Cows consuming the same diet were arranged according to a completely randomized design. Results showed that, compared to the late lactation group, the dry period group had a significantly lower total dirtiness score, higher phosphorus digestibility, and elevated serum calcium levels (p < 0.05). Additionally, fecal consistency and fecal height were greater in the dry period group (p < 0.05). However, the increased phosphorus digestibility observed during the dry period was not significantly associated with fecal consistency (r = +0.225, p < 0.05) or the total contamination score (r = -0.339, p < 0.05). Consequently, this study reveals that understanding the differences in mineral digestibility between different physiological stages can enhance nutritional approaches for better dairy cow management.

Caracterización de unidades de producción pecuaria en Aldama, Tamaulipas, México: productores, hato y alimentación animal

Characterizing livestock production units (LPUs) allows us to suggest technologies that counteract problems and increase productivity. The objective of this study was to characterize the producers, herd and animal feed in LPUs in the municipality of Aldama, Tamaulipas, Mexico, where 49 producers who own LPUs of beef cattle participated. For the analysis of the information, descriptive statistics and Excel (Microsoft®) were used. The average age of the owners was 58 ± 14 years and 85% can read and write. The area dedicated to grazing is 119 ± 51 ha and livestock farming is mainly extensive (55%), where the pastures present are African star grass (Cynodon, 35%), Guinea grass (Megathyrsus, 25%) and hurricane grass (Bothriochloa, 24%). The 64% of the producers mentioned that drought is the main problem. The main bovine genotypes used are crosses of zebu cattle and specialized meat breeds (66%). The herd consists mainly of lactating (calving) and dry (pregnant) cows; 37%. Cattle graze all year round on the pastures, while supplementation and/or supplementation are used during the dry season (December-July). There are few innovations adopted with respect to technified grazing (6 %), forage conservation (5%), and pasture establishment (4%). The drought causes a decrease in the availability of fodder and producers, not having the training or resources to produce fodder, have to resort to the purchase of hay, silage, concentrates and grains, which increases production costs in the LPUs.

Evaluación del bienestar animal en vacas lecheras de una unidad de producción de la Comarca Lagunera, México

The aim of this study was to evaluate the animal welfare status of dairy cows in an intensive production unit, using the Welfare Quality protocol. A total of 315 lactating and dry cows were evaluated, based on four principles: adequate feeding, housing, health and behavior. To achieve this, animal-based, management-based and housing-based measures were recorded. As indicated in the protocol, most of them contain a three-point scale ranging from zero to two, 0: welfare is good, 1: there is some compromise in welfare and 2: welfare is insufficient and unacceptable. The critical variables found for cow welfare were: absence of thirst; cleanliness of quarters (46.62%), udder (13.42%) and flanks (38.34%); time to lie down (5.24 s); dystocia (24%), eye discharge (6.27%) and diarrhea (100%). It is concluded that the production unit has important areas of opportunity to improve the animal welfare of its cows, according to the standards proposed by the Welfare Quality protocol.

Biorefined perennial ryegrass press cake as an alternative feed for dairy cows in late lactation and during the dry period: a demonstration

Abstract To investigate the potential application of replacing a proportion of a perennial ryegrass (PRG) silage diet with press cake on productivity and enteric methane (CH4) emissions in late lactation and non-lactating spring-calving dairy cows, a study was undertaken in which control cows (n = 21) were offered PRG silage, while treatment cows (n = 21) were offered a diet consisting of 60% PRG press cake and 40% of the same PRG silage. Although treatment cows had higher group average dry matter intakes (DMI) and produced more enteric CH4, carbon dioxide (CO2), milk solids, protein, fat- and protein-corrected milk yield (FPCM) in late lactation, the magnitude of the difference between treatment and control cows varied from week to week (P &lt; 0.050). When enteric CH4 per kg of milk yield, milk solids and FPCM were considered, there was no significant difference between treatment and control. Absolute enteric CH4 was higher for cows fed press cake during the non-lactating period but this tended to vary from week to week. Similarly, CO2 (P &lt; 0.001) and hydrogen (H2; P = 0.023) differed from week to week for cows offered press cake, and cows offered PRG silage in the non-lactating period. Although there was no significant effect of diet on body weight (BW) and body condition score (BCS), when enteric CH4 was expressed on a per kg BW basis, cows offered press cake tended to produce more enteric CH4 in both late lactation and during the dry period.

Accuracy and precision of diets fed to close-up cows on dairy farms and its association with early lactation performance

Ensuring a consistent ration is critical for maximizing lactating cow performance, but this is not known for dry cows. The objectives of this cohort observational study were to: 1) characterize close-up dry cow diets fed on commercial farms in Ontario, Canada, 2) describe the accuracy of the nutrient composition between the formulated close-up diet and the diet offered to the cows, 3) describe the precision of the close-up diets across time, and 4) explore potential associations of that accuracy and precision with blood metabolic parameters and milk yield of cows in early lactation. Forty free-stall dairy farms were visited once every 4 wk, for a total of 6 visits to each farm, from April to October 2022. At each visit, samples of the close-up diet were collected and analyzed for dry matter (DM) content and chemical composition. Close-up diet formulations were also obtained by each farm's nutritionists. During each visit, fresh cows (0 to 14 d in milk [DIM]) had blood samples taken for blood metabolites. The same cows were also monitored for milk yield up to 120 DIM. Multivariable models were used to analyze associations between variability (in relation to the formulated diet and across time) of nutrients in the close-up diet, as measured by coefficient of variation (CV), and outcomes in fresh cows. Corn silage (67.6% of farms) and straw (24.3% of farms) were the predominant primary forage sources used in the close-up dry cow diets. Soybean meal (37.8% of farms) and canola meal (18.9% of farms) were the main ingredients used as primary concentrate sources. Overall, the diets offered did not accurately represent the formulated diets. With the exception of net energy for lactation (NEL), the CVs for the other nutrients were all greater than 5%. Diet variability, both between fed and formulated diets and from visit to visit during the close-up period, was associated with metabolic markers and dairy cow production. Lower variability in non-fiber carbohydrates (NFC) between the fed and formulated diets was associated with better liver health index scores. Visit-to-visit variability in fat% and NFC% were associated with blood β-hydroxybutyrate (BHB) concentrations, while NFC% variability was associated with blood glucose levels. Serum nonesterified fatty acids (NEFA) concentrations were associated with visit-to-visit variability in DM% and CP%. These results underscore the importance of maintaining consistency between diet formulations and feeding practices over time to optimize early-lactation dairy herd performance and health, granted that these diets are correctly formulated to meet the nutritional needs of cows in the close-up period and applied with recommended feeding practices.

Genetic parameters for methane production, intensity, and yield predicted from milk mid-infrared spectra throughout lactation in Holstein dairy cows

Genetic selection to reduce methane (CH4) emissions is a promising solution for reducing the environmental impact of dairy cattle production. Before such a selection program can be implemented, however, it is necessary to have a better understanding of the genetic determinism of CH4 emissions and how this might influence other traits of interest. In this study, we performed a genetic analysis of 6 CH4 traits predicted from milk mid-infrared spectra. We predicted 4 CH4 traits in g/d (MeP, calculated using different prediction equations), one in g/kg of fat- and protein-corrected milk (MeI), and one in g/kg of dry matter intake (MeY). Using an external data set, we determined these prediction equations to be applicable in the range of 70 to 200 DIM. We then estimated genetic parameters in this DIM range using random regression models on a large data set of 829,025 spectra collected between January 2013 and February 2023 from 167,514 first- and second-parity Holstein cows. The 6 CH4 traits were found to be genetically stable throughout and across lactations, with average genetic correlations within a lactation ranging from 0.93 to 0.98, and those between lactations ranging from 0.92 to 0.98. All 6 CH4 traits were also found to be heritable, with average heritability ranging from 0.24 to 0.45. The average pairwise genetic correlations between the 6 CH4 traits ranged from -0.15 to 0.77, revealing that they are genetically distinct, including the 4 measurements of MeP. Of the 6 traits, 2 measures of MeP and MeI did not present antagonistic genetic correlations with milk yield, fat and protein contents, and SCS, and can probably be included in breeding goals with limited impact on other traits of interest.

Endocrine adaptations to demanding physiological states in ruminants.

Highly productive ruminants rely on hormonally driven adaptations to prioritize the use of limiting nutrients during the demanding phases of the pregnancy-lactation cycle. Glucose, the predominant oxidative fuel of fetal life and the absolute precursor of mammary lactose synthesis, illustrates the need and benefit of such adaptations. Endocrine mechanisms such as insulin resistance and/or hypoinsulinemia favor the diversion of maternal glucose to the placenta or mammary gland where uptake is independent of insulin. Research in dairy cows in the 1980s and 1990s identified growth hormone as a peripherally acting signal opposing the effects of insulin. The following decades have seen the discovery of a new generation of signals secreted almost exclusively by adipose tissue, skeletal muscle or liver, dynamically regulated by metabolic challenges, and engaged in cross-organ communication. The understanding of these signals in the coordination of metabolism in ruminants has been limited by the availability of assays to measure their circulating concentrations and materials to perform functional studies. Nevertheless, emerging data point to their importance during demanding physiological states in ruminants, including early lactation in dairy cows and late pregnancy in sheep. Examples include modulation of insulin action by liver-derived fibroblast growth factor 21 (FGF21) and regulation of energy allocation among tissues by the action of the adipose-derived hormone leptin via its ability to control the hypothalamic-pituitary-thyroid axis. Recent studies investigating the regulation and action of FGF21 and leptin in dairy cows and sheep will be used to illustrate the potential of recently discovered signals to coordinate metabolism during physiologically demanding states such as early lactation.

Using Milk Urea to Evaluate Production, Efficiency of Nitrogen Utilization and Urinary Nitrogen Excretion During The Lactation In Dairy Cows

Abstract The aim of this study was to use milk urea to evaluate production parameters, efficiency of nitrogen utilization, and urinary nitrogen excretion during lactation in Holstein dairy cows. Cows in the 1st lactation phase compared to the 2nd and 3rd lactation phases showed: increase (P &lt; 0.05) in daily milk yield; decrease (P &lt; 0.05) in fat and protein content in milk; decrease in milk urea content (P &lt; 0.05); with a lower individual number of animals (31% of dairy cows in the 1st stage of lactation, 39 % of dairy cows in the 2nd stage of lactation, and 44 % of dairy cows in the 3rd phase of lactation) with an above-limit milk urea content (35.0 ± 4.7; 34.9 ± 4.1, 34.8 ± 4.1 mg.dl-1); decreased urinary nitrogen excretion (P &lt; 0.05); and efficiency of nitrogen utilization from feed to milk (P &lt; 0.05). According to the phase of lactation, the efficiency of nitrogen utilization decreased and urinary nitrogen excretion increased with increasing milk urea content.

Effects of Moringa oleifera leaf powder supplementation on milk somatic cell scores and the plasma indexes of inflammation and antioxidant activity in dairy cows.

The effects of Moringa oleifera (MO) leaf powder (MOLP) supplementation on milk somatic cell scores (SCS), plasma inflammation markers, and plasma antioxidants were studied in 18 multiparous Holstein cows, 10 in early lactation (days in milk; DIM < 100) and eight in mid- and late-lactation (DIM ≥ 100). Nine of these 18 cows (5 + 4 individuals for each lactation stage, respectively) were placed in the MO group and fed with MOLP at 0.3% of partial mixed ration (PMR) dry matter (DM) for 3 weeks, while the other nine represented the control group and were not fed any MOLP supplementation. Milk, blood, and rumen fluid samples were collected on weeks 0 and 3. The SCS and plasma acute phase protein (APP) concentrations in the early lactation cows in the control group increased markedly (P < 0.05) and milk yield decreased significantly, resulting in a difference (P < 0.05) between groups at the end of the experiment. In mid- and late-lactation cows, MOLP supplementation did not affect SCS, milk yields, and plasma APP concentrations. Plasma superoxide dismutase levels in the MO group at both lactation stages were higher (P < 0.05) than in the control group. In conclusion, feeding MOLP at 0.3% of PMR DM to dairy cows for 3 weeks controlled the increase in SCS in the early lactation individuals and the subsequent decrease in milk production as a response to inflammation. The results also suggested that MOLP supplementation was responsible for the increase in antioxidant activity during lactation.

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.

Fermented soybean meal modified the rumen microbiota and increased the serum prolactin level in lactating Holstein cows.

This study aimed to investigate the effects of fermented soybean meal (FSM) on milk production, blood parameters, and rumen fermentation and microbial community in dairy cows. In this study, 48 healthy Holstein cows (parity, 3.0 ± 0.6; days in milk, 86.0 ± 6.7) were used. Cows were randomly assigned into four groups (CON, T-200, T-400, and T-600) with 12 cows per group. Cows in CON were not supplemented with FSM. Cows in T-200, T-400, and T-600 were supplemented with 200, 400, and 600 g/head/day FSM, respectively. This study lasted 5 weeks (1-week adaptation and 4-week treatment). The results showed that FSM did not affect milk yield and milk components (p > 0.05). In the serum, FSM greatly increased prolactin (p < 0.01), and a dosage effect was observed. Aspartate aminotransferase and total protein were the highest in the T-400 (p < 0.05), and triglycerides was the lowest in T-200 (p < 0.05), and there was no difference for the 3 measurements between the other 3 groups (p > 0.05). In the rumen, FSM did not affect pH, microbial crude protein, acetate, propionate, butyrate, valerate, total volatile fatty acids and the ratio of acetate:propionate (p > 0.05), only changed NH3-N, isobutyrate and isovalerate (p < 0.05). The results of the rumen bacterial 16S rRNA genes sequencing showed that FSM decreased the richness (p < 0.05) and evenness (p < 0.05) of the bacterial communities. PCoA analysis showed that FSH altered the rumen bacterial community (ANOSIM, R = 0.108, p = 0.002). In the relative abundance of phyla, FSM increased Firmicutes (p = 0.015) and Actinobacteriota (p < 0.01) and Patescibacteria (p = 0.012), decreased Bacteroidota (p = 0.024). In the relative abundance of genera, FSM increased Christensenellaceae R-7 group (p = 0.011), Lactococcus (p < 0.01), Candidatus Saccharimonas (p < 0.01), Olsenella (p < 0.01), decreased Muribaculaceae_norank (p < 0.01). Conclusively, supplemented FSM altered the rumen fermentation parameters and bacterial community, and increased serum prolactin level in lactating Holstein cows. These findings may provide an approach to keep the peak of lactation in dairy cows.

Genomic evaluation of residual feed intake in US Holstein cows: insights into lifetime feed efficiency.

Residual feed intake (RFI) is an important trait of feed efficiency that has been increasingly considered in the breeding objectives for dairy cattle. The objectives of this study were to estimate the genetic parameters of RFI and its component traits, namely, dry-matter intake (DMI), body weight (BW), and energy-corrected milk (ECM), in lactating Holstein cows; we thus developed a system for genomic evaluation of RFI in lactating Holstein cows and explored the associations of the RFI of heifers and cows. The RFI values were calculated from 2,538 first (n = 2,118) and second (n = 420) lactation Holsteins cows between 2020 and 2024 as part of the STgenetics EcoFeed® program. Of the animals, 1,516 were heifers from the same research station with previously established RFI values . After quality control, 61,283 single-nucleotide polymorphisms were used for the analyses. Univariate analyses were performed to estimate the heritabilities of RFI and its components in lactating cows; bivariate analyses were then performed to estimate the genetic correlations between the RFI of heifers and lactating cows using the genomic best unbiased linear prediction method. Animals with phenotypes and genotypes were used as the training population, and animals with only genotypes were considered the prediction population. The reliability of breeding values was obtained by approximation based on partitioning a function of the accuracy of the training population's genomic estimated breeding values (GEBVs) and magnitudes of genomic relationships between the individuals in the training and prediction populations. The heritability estimates (mean ± SE) of the RFI, DMI, ECM, and BW were 0.43 ± 0.07, 0.44 ± 0.04, 0.40 ± 0.05, and 0.46 ± 0.04, respectively. The average reliability of the GEBVs for RFI from the training and prediction populations were 44% and 30%, respectively. The genetic correlations for the RFI were 0.42 ± 0.08 between heifers and first lactation cows and 0.34 ± 0.06 between heifers and first and second lactation cows. Our results show that the genetic components of RFI are not fully carried over from heifers to cows and that there is re-ranking of the individuals at different life stages. Selection of animals for feed efficiency on a lifetime basis thus requires accounting for the efficiencies during animal growth and milk production as a lactating cow.

Stage-Specific Milk Yield Losses and Associated Sweating, Respiration, and Rectal Temperature Responses Under Varying THI Thresholds in Lactating and Dry Cows

Heat stress (HS) may result in changes in the behavior, endocrine system, and physiological characteristics of dairy cows, and it may even lead to death in severe cases. As the effects of global warming have become more notable, the prevalence of HS has increased among dairy cows. Therefore, comprehensive strategies, including not only cooling measures but also dietary adjustments and genetic improvements for heat tolerance, are required to help these animals regulate their body temperature and avoid HS. In addition, detecting HS signs is essential for both lactating and dry cows to ensure appropriate interventions. The temperature-humidity index (THI) is a widely used tool for evaluating the effects of HS on livestock. Since the physiological state of cattle significantly influences their responses to HS, it is imperative to establish specific THI thresholds for both lactating and dry cows to implement appropriate cooling regimens and optimize animal welfare. In this study, we used the THI to investigate the relationship between rectal temperature (RT), respiration rate (RR), and sweating rate (SR) in lactating and dry cows. We also explored the relationships between milk yield at different lactation stages and THI thresholds. The results indicated that lactating and dry cows had different THI thresholds based on their immediate physiological responses. Compared with lactating cows, dry cows had higher THI thresholds for RT, RR, and SR. In addition, cows in early-, intermediate-, and late-lactation stages under thermoneutral conditions produced significantly more milk than did those under mild, moderate, and severe HS conditions, indicating that milk yield losses occur under HS conditions. Taken together, these findings provide valuable insights into how HS can be mitigated in subtropical dairy farms. For lactating cows, implementing cooling measures is recommended when the THI reaches 66 to 67, whereas for dry cows, waiting until the THI reaches 73 is recommended. Milk yield losses may occur when lactating cows are under HS conditions. Therefore, appropriate cooling measures should be implemented at accurate THI thresholds to ensure optimal animal welfare for both lactating and dry cows.

Assessing traditional and machine learning methods to smooth and impute device-based body condition score throughout the lactation in dairy cows

Regular monitoring of body condition score (BCS) changes during lactation is an essential management tool in dairy cattle; however, the current BCS measurements are often discontinuous and unevenly spaced in time. The imputation of BCS values is useful for two main reasons: i) achieving completeness of data is necessary to be able to relate BCS to other traits (e.g. milk yield and milk composition) that have been routinely recorded at different times and with a different frequency, and ii) having expected BCS values provides the possibility to trigger early warnings for animals with certain unexpected conditions. The contribution of this study was to propose and evaluate potential methods useful to smooth and impute device-based BCS values recorded during lactation in dairy cattle. In total, 26,207 BCS records were collected from 3,038 cows (9,199 and 14,462 BCS records on 1,546 Holstein and 1,211 Montbéliarde cows respectively, and the rest corresponded to other minority cattle breeds). Six methods were evaluated to predict BCS values: the traditional methods of test interval method (TIM), and multiple-trait procedure (MTP), and the machine learning (ML) methods of multi-layer perceptron (MLP), Elman network (Elman), long-short term memories (LSTM) and bi-directional LSTM (BiLSTM). The performance of each method was evaluated by a hold-out validation approach using statistics of the root mean squared error (RMSE) and Pearson correlation (r). TIM, MTP, MLP, and BiLSTM were assessed for the imputation of intermediate missing values, while MTP, Elman, and LSTM were evaluated for the forecasting of future BCS values. Regarding the machine learning methods, BiLSTM demonstrated the best performance for the intermediate value imputation task (RMSE = 0.295, r = 0.845), while LSTM demonstrated the best performance for the future value forecasting task (RMSE = 0.356, r = 0.751). Among the methods evaluated, MTP showed the best performance for imputation of intermediate missing values in terms of RMSE (0.288) and r (0.856). MTP also achieved the best performance for forecasting of future BCS values in terms of RMSE (0.348) and r (0.760). This study demonstrates the ability of MTP and machine learning methods to impute missing BCS data and provides a cost-effective solution for the application area.

Heifer Fertility Relationship with First Lactation Cow Traits of Friesian Dairy Cattle in Egypt

Heifer Fertility Relationship with First Lactation Cow Traits of Friesian Dairy Cattle in Egypt

Evaluation of Four Different Automated Activity Monitoring Systems to Identify Anovulatory Cows in Early Lactation.

The objective of this study was to evaluate four different automated activity monitoring (AAM) systems to identify anovulatory cows in early lactation. A total of 852 lactating Holstein cows (221 primiparous and 631 multiparous cows) from four commercial dairy herds were enrolled. On each farm, cows were equipped with a respective AAM system (SB: Smartbow; HT: Heatime; DP: Delpro; and CM: CowManager). Each cow was sampled three times within the voluntary waiting period (VWP) in a two-week interval to detect the blood progesterone (P4) concentration. Cows were classified based on the concentration of P4 as follows: (1) none of the three blood P4 concentrations exceeded 1.0 ng/mL (anovulatory); (2) at least one of the three blood P4 concentrations was above 1.0 ng/mL (ovulatory). Cows were classified based on estrus alerts as follows: (1) no estrus alert was detected by an AAM system from 7 to 60 DIM (anestrus); (2) at least one estrus alert was detected by an AAM system from 7 to 60 DIM (estrus). Accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were calculated for each AAM system for anovulatory cows [(SB: 77.6%; 26.8%; 89.3%; 36.7%; and 84.1%); (HT: 79.2%; 63.6%; 83.6%; 52.8%; and 88.9%); (DP: 47.2%; 78.8%; 41.5%; 19.5%; and 91.6%); (CM: 80.5%; 23.7%; 92.7%; 39.1%; and 85.3%)].

Production and metabolic responses of Montbéliarde and Holstein cows during periparturient period and a sequential feed restriction challenge

The objective was to compare the production and metabolic responses of 22 Montbéliarde (MONT) and 18 Holstein (HOLS) multiparous cows during the periparturient period, and during a sequential nutritional challenge (SNC), consisting of 4 successive induced short feed restrictions each separated by a refeeding period, to explore breed differences in robustness (ability to maintain lactation function during successive challenges) and resilience (ability to recover after each challenge). Cows were studied from 4 wk before expected calving until 158 ± 9 DIM (mean ± SD). Milk and ECM yields were greater in HOLS than in MONT during both the early (i.e., from calving to wk 10) and mid-lactation (i.e., from wk 18 to 22) periods, whereas BCS was greater in MONT than HOLS. During early lactation, energy balance was lower (5 vs. 16 MJ/d), plasma NEFA (270 vs 163 µM) were greater, for HOLS than MONT, respectively. Cows in third-and-greater lactation secreted more ECM, and had delayed resumption of luteal activity compared with second lactation cows. The SNC started at 87 ± 9 DIM and consisted of a sequence of 4 4-d periods of feed restriction (FR), during which feed allowance was calculated to meet 50% of individual energy requirements (FR1, FR2, FR3, FR4), each of them being followed by an ad libitum intake period. Cows were allowed 10 d of ad libitum intake between FR1 and FR2 to study the recovery and compare it with the recovery following FR4, and 3 d of ad libitum intake between FR2, FR3 and FR4 to study responses to repeated FR. Feed allowance met 59 to 67% of energy requirements during FR1 through FR4, as milk secretion decreased with successive FR. Breed differences in milk secretion persisted throughout the nutritional challenges, but were more pronounced during the first 2 FR: Uncorrected MY was greater for HOLS throughout the entire SNC, whereas ECM and plasma NEFA concentrations and milk fat yield were greater for HOLS than MONT during FR1 and FR2, but not FR3 and FR4, suggesting a reduced ability of HOLS to mobilize and transfer fatty acids into milk with successive FRs, and indicating altered robustness of HOLS to maintain high milk yield. Resilience for ECM yield did not differ between breeds. Cows were able to respond to and recover from the SNC, by decreasing milk secretion during FR, undergoing acute metabolic adaptations to support lactation, and recovering DMI during each refeeding period. Cow rankings for ECM yield were maintained consistently from early lactation throughout the SNC periods (rs = 0.59 to 0.90), suggesting that dairy potential was a major driver of responses during the SNC for both HOLS and MONT.

A review of extended lactation in dairy cows managed in high-input and pasture-based farming systems

Traditionally the lactation cycle of a dairy cow is based around a 12-month calving interval, allowing for 10 months of lactation, followed by a 2-month dry period. This means that the cow has to conceive within 2–3 months after calving, when she is also at peak lactation and metabolically is in a negative energy balance. Such challenging physiological conditions make it challenging for the cow to conceive at this time and many modern high-producing cows fail to get pregnant within the constraints of a 12-month calving interval. In addition, many cows still produce at a high level at drying-off time, increasing the risk of intramammary infections. Therefore, delaying conception past peak production and, as a result, extending the lactation beyond 10 months may increasingly be necessary. Additionally, extended lactation (EL) may offer other advantages such as fewer calves being born and thus fewer ‘surplus’ calves needing to be culled at a young age, fewer health and welfare issues and improved environmental outcomes (i.e. less greenhouse-gas emission; less antibiotic usage) during the lifetime of the animal. Extending lactation is a straight forward management practice in high-input dairy systems where a consistent supply of feed supplements is readily available, but may be more challenging to implement in low(er)-input pasture-based systems. The latter are much more seasonal, with a 12-month calving interval allowing pasture growth and quality to match the cow’s nutritional demands; cows calve in spring when high-quality pasture is abundant and are dried-off during winter when pasture growth is more limited. In this review, we explored the impact of EL in both high-input systems and pasture-based systems. It covers the effects of EL on milk production, composition and processing, as well as on reproductive performance, health and welfare, and environmental and economic outcomes.

Effects of Oregano on Lactation Performance, Nutrient Digestibility, Ruminal Fermentation Parameters, and Methane Emissions in Dairy Cows: A Meta-Analysis

Growing concerns regarding antibiotic use in livestock, due to antibiotic resistance and potential human transmission, have led to increased interest in herbs and their derivatives, including essential oils, which possess antimicrobial properties that may enhance overall productivity and serve as a strategy for methane mitigation. The objective of this meta-analysis was to investigate the effects of adding oregano to the diet in different forms (essential oils, plant materials, or leaves) on the dry matter intake (DMI), milk yield (MY), milk components, nutrient digestibility, ruminal fermentation parameters, and methane (CH4) emissions of dairy cows. A literature search was conducted to identify papers published from 2000 to 2023. Effect size for all outcomes was reported as a standardized means difference (SMD) and raw means difference with 95% confidence intervals. Heterogeneity was determined using the Q test and I2 statistic. The results of the meta-analysis indicated that adding oregano had no effect on DMI (SMD = 0.081; p = 0.507) and MY (SMD = 0.060; p = 0.665). Milk fat percentage, milk protein percentage, and milk lactose percentage were not affected by oregano. The addition of oregano to the diet significantly decreased dry matter digestibility (SMD = −0.502; p = 0.013), crude protein digestibility (SMD = −0.374; p = 0.040), and neutral detergent fiber digestibility (SMD = −0.505; p = 0.014). Ruminal pH (SMD = −0.122; p = 0.411), total volatile fatty acids concentration (SMD = −0.038; p = 0.798), acetate (SMD = −0.046; p = 0.757), propionate (SMD = 0.007; p = 0.960), and butyrate (SMD = 0.037; p = 0.801) proportion were not affected by oregano. The addition of oregano to the diet tended to decrease CH4/DMI (SMD = −0.275; p = 0.095) but did not affect CH4 production (SMD = −0.156; p = 0.282). Heterogeneity (Q and I2) was non-significant for all parameters. We conclude that the inclusion of oregano in various forms (essential oils, plant materials, or leaves) in the diet of dairy cows reduces nutrient digestibility but does not significantly affect DMI, MY, milk components, ruminal fermentation parameters, or CH4 production. Future research should focus on optimizing the dosage of oregano (both EOs and plant materials) and exploring the impact of its form on lactation, nutrient digestibility, ruminal fermentation, and CH4 emissions in dairy cows.