Cows In Early Lactation Research Articles

Intravenous lipopolysaccharide challenge in early- versus mid-lactation dairy cattle. II: The production and metabolic responses

Most immunometabolic research uses mid-lactation (ML) cows. Cows in early lactation (EL) are in a presumed state of immune suppression/dysregulation and less is known about how they respond to a pathogen. Study objectives were to compare the production and metabolic responses to i.v. LPS and to differentiate between the direct effects of immune activation and the indirect effects of illness-induced hypophagia in EL and ML cows. Cows in EL (n = 11; 20 ± 2 DIM) and ML (n = 12; 131 ± 31 DIM) were enrolled in a 2 × 2 factorial design containing 2 experimental periods (P). During P1 (3 d), cows were fed ad libitum and baseline data were collected. At the initiation of P2 (3 d), cows were randomly assigned to 1 of 2 treatments by lactation stage (LS): (1) EL (EL-LPS; n = 6) or ML (ML-LPS; n = 6) cows administered i.v. a single bolus of 0.09 µg LPS/kg of BW; Escherichia coli O55:B5 or (2) pair-fed (PF) EL (EL-PF; n = 5) or ML (ML-PF; n = 6) cows administered i.v. saline. Administering LPS decreased DMI and this was more severe in EL-LPS than ML-LPS cows (34% and 11% relative to baseline, respectively). By design, P2 DMI patterns were similar in the PF groups compared with their LPS counterparts. Milk yield decreased following LPS (42% on d 1 relative to P1) and despite an exacerbated decrease in EL-LPS cows on d 1 (25% relative to ML-LPS), remained similar between LS from d 2 to 3. The EL-LPS cows had increased milk fat content, but no difference in protein and lactose percentages compared with ML-LPS cows. Further, cumulative ECM yield was increased (21%) in EL-LPS compared with ML-LPS cows. During P2, EL-LPS cows had a more intense increase in MUN and BUN than ML-LPS and EL-PF cows. Administering LPS did not cause hypoglycemia in either EL-LPS or ML-LPS cows, but glucose was increased (33%) in EL-LPS compared with EL-PF. Hyperinsulinemia occurred after LPS, and insulin was further increased in ML-LPS than EL-LPS cows (2.2-fold at 12 h peak). During P2, circulating glucagon increased only in EL-LPS cows (64% relative to all other groups). Both EL groups had increased NEFA at 3 and 6 h after LPS from baseline (56%), but NEFA in EL-LPS cows gradually returned to baseline thereafter and were reduced relative to EL-PF until 36 h (50% from 12 to 24 h). Alterations in BHB did not differ between ML groups, but EL-LPS had reduced BHB compared with EL-PF from 24 to 72 h (51%). Results indicate that there are distinct LS differences in the anorexic and metabolic responses to immune activation. Collectively, EL cows are more sensitive to the catabolic effects of LPS than ML cows, but these exacerbated metabolic responses appear coordinated to fuel an augmented immune system while simultaneously supporting milk synthesis.

The Most Important Metabolic Diseases in Dairy Cattle during the Transition Period.

This review paper provides an in-depth analysis of three critical metabolic diseases affecting dairy cattle such as subacute ruminal acidosis (SARA), ketosis, and hypocalcemia. SARA represents a disorder of ruminal fermentation that is characterized by extended periods of depressed ruminal pH below 5.5-5.6. In the long term, dairy herds experiencing SARA usually exhibit secondary signs of the disease, such as episodes of laminitis, weight loss and poor body condition despite adequate energy intake, and unexplained abscesses usually 3-6 months after an episode of SARA. Depressed milk-fat content is commonly used as a diagnostic tool for SARA. A normal milk-fat test in Holstein dairy cows is >4%, so a milk-fat test of <3% can indicate SARA. However, bulk tank testing of milk fat is inappropriate to diagnose SARA at the herd level, so when >4 cows out of 12 and <60 days in milk are suspected to have SARA it can be considered that the herd has a problem. The rapid or abrupt introduction of fresh cows to high-concentrate diets is the most common cause of SARA. Changes in ruminal bacterial populations when exposed to higher concentrate rations require at least about 3 weeks, and it is recommended that concentrate levels increase by no more than 400 g/day during this period to avoid SARA. Ketosis, a prevalent metabolic disorder in dairy cattle, is scrutinized with a focus on its etiological factors and the physiological changes leading to elevated ketone bodies. In total mix ration-fed herds, an increased risk of mastitis and reduced fertility are usually the first clinical signs of ketosis. All dairy cows in early lactation are at risk of ketosis, with most cases occurring in the first 2-4 weeks of lactation. Cows with a body condition score ≥3.75 on a 5-point scale at calving are at a greater risk of ketosis than those with lower body condition scores. The determination of serum or whole blood acetone, acetoacetate, beta-hydroxybutyrate (BHB) concentration, non-esterified fatty acids (NEFA), and liver biopsies is considered the best way to detect and monitor subclinical ketosis, while urine or milk cowside tests can also be used in on-farm monitoring programs. Concentrations >1.0 mmol/L or 1.4 mmol/L blood or serum BHB are considered diagnostic of subclinical ketosis. The standard threshold used for blood is 1.2 mmol/L, which corresponds to thresholds of 100 mcmol/L for milk and 15 mg/dL for urine. Oral administration of propylene glycol (250-400 g, every 24 h for 3-5 days) is the standard and most efficacious treatment, as well as additional therapy with bolus glucose treatment. Hypocalcemia is a disease of adult dairy cows in which acute hypocalcemia causes acute to peracute, afebrile, flaccid paralysis that occurs most commonly at or soon after parturition. Dairy cows are at considerable risk for hypocalcemia at the onset of lactation, when daily calcium excretion suddenly increases from about 10 g to 30 g per day. Cows with hypocalcemia have a more profound decrease in blood calcium concentration-typically below 5.5 mg/dL. The prevention of parturient paresis has been historically approached by feeding cows low-calcium diets during the dry period. Negative calcium balance triggers calcium mobilization before calving and better equips the cow to respond to the massive calcium needs at the onset of lactation. Calcium intake must be limited to <20 g per day for calcium restriction to be effective. The most practical and proven method for monitoring hypocalcemia is by feeding cows an acidogenic diet for ~3 weeks before calving. Throughout the review, emphasis is placed on the importance of early diagnosis and proactive management strategies to mitigate the impact of these metabolic diseases on dairy cattle health and productivity. The comprehensive nature of this paper aims to serve as a valuable resource for veterinarians, researchers, and dairy farmers seeking a deeper understanding of these prevalent metabolic disorders in dairy cattle.

Investigation of HCAR2 antagonists as a potential strategy to modulate bovine leukocytes

BackgroundDairy cows experiencing ketosis after calving suffer greater disease incidence and are at greater risk of leaving the herd. In vitro administration of beta-hydroxybutyric acid (BHBA; the primary blood ketone) has inhibitory effects on the function of bovine leukocytes. BHBA is a ligand of HCAR2 and the activation of these receptors promotes an anti-inflammatory response which may be related with immunosuppression observed in transition dairy cattle. The objective of this study was to identify and test antagonists for HCAR2 in bovine immune cells cultured with BHBA.ResultsWe observed expression of HCAR2 at the protein level within lymphocytes, monocytes, and granulocytes. The proportion of cells expressing HCAR2 tended to be greater in mid-lactation compared to early lactation cows; the increase was a result of increased proportion of T and B cells expressing HCAR2. Stimulation of HCAR2 with niacin or BHBA promoted Ca2+ mobilization in neutrophils and mononuclear cells. Mononuclear cells treated with BHBA had diminished intracellular Ca2+ responses when HCAR2 was knocked down by siRNA silencing, indicating Ca2+ mobilization was mediated by HCAR2 signaling. Two candidate antagonists for HCAR2, synthesized from niacin (NA-1 and NA-5), were tested; monocytes and neutrophils pre-treated with NA-1 and NA-5 had reduced Ca2+ mobilization after incubation with BHBA. Furthermore, NA-5 but not NA-1 prevented BHBA-associated reductions in cyclic AMP.ConclusionsWe demonstrated that HCAR2 is present on bovine leukocytes and has greater expression later in lactation. We confirmed that BHBA and niacin derived HCAR2 antagonists alter bovine leukocyte activity. Our results demonstrate that both BHBA and niacin affect bovine leukocyte Ca2+ mobilization in a HCAR2-dependent manner.

Intravenous lipopolysaccharide challenge in early- versus mid-lactation dairy cattle. I: The immune and inflammatory responses

Cows in early lactation (EL) are purportedly immune suppressed, which renders them more susceptible to disease. Thus, the study objective was to compare key biomarkers of immune activation from i.v. LPS between EL and mid-lactation (ML) cows. Multiparous EL (20 ± 2 DIM; n = 11) and ML (131 ± 31 DIM; n = 12) cows were enrolled in a 2 × 2 factorial design and assigned to 1 of 2 treatments by lactation stage (LS): (1) EL (EL-LPS; n = 6) or ML (ML-LPS; n = 6) cows administered a single LPS bolus from Escherichia coli O55:B5 (0.09 µg/kg of BW), or (2) pair-fed (PF) EL (EL-PF; n = 5) or ML (ML-PF; n = 6) cows administered i.v. saline. After LPS administration, cows were intensely evaluated for 3 d to analyze their response and recovery to LPS. Rectal temperature increased in LPS relative to PF cows (1.1°C in the first 9 h), and the response was more severe in EL-LPS relative to ML-LPS cows (2.3 vs. 1.3°C increase at 4 h post-LPS; respectively). Respiration rate increased only in EL-LPS cows (47% relative to ML-LPS in the first hour post-LPS). Circulating tumor necrosis factor-α, IL-6, monocyte chemoattractant protein-1, macrophage inflammatory protein (MIP)-1α, MIP-1β, and IFN-γ-inducible protein-10 increased within the first 6 h after LPS and these changes were exacerbated in EL-LPS relative to ML-LPS cows (6.3-fold, 4.8-fold, 57%, 93%, 10%, and 61%, respectively). All cows administered LPS had decreased circulating iCa relative to PF cows (34% at the 6 h nadir), but the hypocalcemia was more severe in EL-LPS than ML-LPS cows (14% at 6 h nadir). In response to LPS, neutrophils decreased regardless of LS, then increased into neutrophilia by 24 h in all LPS relative to PF cows (2-fold); however, the neutrophilic phase was augmented in EL- compared with ML-LPS cows (63% from 24 to 72 h). Lymphocytes and monocytes rapidly decreased then gradually returned to baseline in LPS cows regardless of LS; however, monocytes were increased (57%) at 72 h in EL-LPS relative to ML-LPS cows. Platelets were reduced (46%) in LPS relative to PF cows throughout the 3-d following LPS, and from 24 to 48 h, platelets were further decreased (41%) in EL-LPS compared with ML-LPS. During the 3-d following LPS, serum amyloid A (SAA), LPS-binding protein (LBP), and haptoglobin (Hp) increased in LPS compared with PF groups (9-fold, 72%, and 153-fold, respectively), and the LBP and Hp responses were more exaggerated in EL-LPS than ML-LPS cows (85 and 79%, respectively) whereas the SAA response did not differ by LS. Thus, our data indicates that EL immune function does not appear "suppressed," and in fact many aspects of the immune response are seemingly functionally robust.

Effect of dietary phosphorus deprivation during the dry period on the liver transcriptome of high-yielding periparturient dairy cows

While dietary phosphorus (P) deprivation extending from the dry period into early lactation impairs health and productivity of cows, restricting dietary P supply during the dry period not only appears to be innocuous but rather effectively mitigates hypocalcemia during the first wk of lactation. To investigate possible negative metabolic effects of P deprivation during the dry period, the present study tested the hypothesis that restarted dietary P supply during the dry period alters the liver transcriptome of dairy cows during the periparturient period. Thirty late-pregnant multiparous Holstein-Friesian dairy cows entering their 2nd, 3rd or 4th lactation were assigned to either a dry cow ration with low (LP, 0.16% P in DM) or adequate P content (AP, 0.35% in DM) during the last 4 wk of the dry period (n = 15/group). Liver transcriptomics, which was carried out in a subset of 5 2nd parity cows of each group (n = 5), and determination of selected hormones and metabolites in blood of all cows, was performed approximately one wk before calving and on d 3 postpartum. Liver tissue specimens and blood samples were obtained by a micro-invasive biopsy technique from the right 10th intercostal space and puncture of a jugular vein, respectively. 175 hepatic transcripts were expressed differentially between LP vs. AP cows in late pregnancy, and 165 transcripts differed between LP vs. AP cows in early lactation (Fold change >1.3 and < -1.3, P < 0.05). In late pregnancy, the enriched biological processes of the upregulated and the downregulated transcripts were mainly related to immune processes and signal transduction (P < 0.05), respectively. In early lactation, the enriched biological processes of the upregulated and the downregulated transcripts were involved in mineral transport and biotransformation (P < 0.05), respectively. The plasma concentrations of the hormones and acute phase proteins (progesterone, insulin-like growth factor 1, serum amyloid α, haptoglobin, and 17β-estradiol) determined were not affected by P supply. These results suggest that P deprivation during the dry period moderately affects the liver transcriptome of cows in late pregnancy and early lactation, and causes no effects on important plasma hormones and acute phase proteins indicating no obvious impairment of health or metabolism of the cows.

Role of diacylglycerol O-acyltransferase 1 (DGAT1) in lipolysis and autophagy of adipose tissue from ketotic dairy cows

High-yielding dairy cows in early lactation often encounter difficulties in meeting the energy requirements essential for maintaining milk production. This is primarily attributed to insufficient dry matter intake, which consequently leads to sustained lipolysis of adipose tissue. Fatty acids released by lipolysis can disrupt metabolic homeostasis. Autophagy, an adaptive response to intracellular environmental changes, is considered a crucial mechanism for regulating lipid metabolism and maintaining a proper cellular energy status. Despite its close relationship with aberrant lipid metabolism and cytolipotoxicity in animal models of metabolic disorders, the precise function of diacylglycerol o-acyltransferase 1 (DGAT1) in bovine adipose tissue during periods of negative energy balance is not fully understood, particularly regarding its involvement in lipolysis and autophagy. The objective of the present study was to assess the effect of DGAT1 on both lipolysis and autophagy in bovine adipose tissue and isolated adipocytes. Adipose tissue and blood samples were collected from cows diagnosed as clinically ketotic (n = 15) or healthy (n = 15) following a veterinary evaluation based on clinical symptoms and serum concentrations of BHB, which were 3.19 mM (interquartile range = 0.20) and 0.50 mM (interquartile range = 0.06), respectively. Protein abundance of DGAT1 and phosphorylation levels of unc-51-like kinase 1 (ULK1), were greater in adipose tissue from cows with ketosis, whereas phosphorylation levels of phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), and mammalian target of rapamycin (mTOR) were lower. Furthermore, when adipocytes isolated from the harvested adipose tissue of 15 healthy cows were transfected with DGAT1 overexpression adenovirus or DGAT1 small interfering RNA followed by exposure to epinephrine (EPI), it led to greater ratios and protein abundance of phosphorylated hormone-sensitive triglyceride lipase (LIPE) to total LIPE and adipose triglyceride lipase (ATGL), while inhibiting the protein phosphorylation levels of ULK1, PI3K, AKT, and mTOR. Overexpression of DGAT1 in EPI-treated adipocytes reduced lipolysis and autophagy, whereas silencing DGAT1 further exacerbated EPI-induced lipolysis and autophagy. Taken together, these findings indicate that upregulation of DGAT1 may function as an adaptive response to suppress adipocytes lipolysis, highlighting the significance of maintaining metabolic homeostasis in dairy cows during periods of negative energy balance.

Influence of Heat Stress on Body Surface Temperature and Blood Metabolic, Endocrine, and Inflammatory Parameters and Their Correlation in Cows.

This study aimed to determine whether heat stress affected the values and correlations of metabolic, endocrinological, and inflammatory parameters as well as the rectal and body surface temperature of cows in the early and middle stages of lactation. This experiment was conducted in May (thermoneutral period), June (mild heat stress), and July (moderate to severe heat stress). In each period we included 15 cows in early lactation and 15 in mid-lactation. The increase in rectal and body surface temperatures (°C) in moderate to severe heat stress compared to the thermoneutral period in different regions was significant (p < 0.01) and the results are presented as mean and [95%CI]: rectal + 0.9 [0.81-1.02], eye + 6 [5.74-6.25], ear + 13 [11.9-14.0], nose + 3.5 [3.22-3.71], forehead + 6.6 [6.43-6.75], whole head + 7.5 [7.36-7.68], abdomen + 8.5 [8.25-8.77], udder + 7.5 [7.38-7.65], front limb + 6 [5.89-6.12], hind limb + 3.6 [3.46-3.72], and whole body + 9 [8.80-9.21]. During heat stress (in both mild and moderate to severe stress compared to a thermoneutral period), an increase in the values of extracellular heat shock protein 70 (eHsp70), tumor necrosis factor α (TNFα), cortisol (CORT), insulin (INS), revised quantitative insulin sensitivity check index (RQUICKI), urea, creatinine, total bilirubin, aspartate transpaminase (AST), gamma-glutamyl transferase (GGT), lactate dehydrogenase (LDH), and creatin kinase (CK) occurred, as well as a decrease in the values of triiodothyronine (T3), thyroxine (T4), non-esterified fatty acids (NEFA), glucose (GLU), β-Hydroxybutyrate (BHB), calcium, phosphorus, total protein (TPROT), albumin (ALB), triglycerides (TGCs), and cholesterol (CHOL). In cows in early lactation compared to cows in mid-lactation, there was a significantly larger increase (p < 0.01) in the values of eHsp70, TNFα, GLU, RQUICKI, and GGT, while the INS increase was smaller during the three experimental periods. The decrease in the values of Ca, CHOL, and TGC was more pronounced in cows in early lactation compared to cows in mid-lactation during the three experimental periods. Rectal temperature was related to eHsp70 (r = 0.38, p < 0.001) and TNFα (r = 0.36, p < 0.01) and showed non-significant poor correlations with other blood parameters. Blood parameters correlate with body surface temperature, with the following most common results: eHsp70 and TNFα showed a moderately to strongly significant positive correlation (r = 0.79-0.96, p < 0.001); CORT, INS, and Creat showed fairly to moderately significant positive correlations; T3, T4, NEFA and GLU showed fairly to moderately significant negative correlations (r = 0.3-0.79; p < 0.01); RQUICKI, urea, AST, and GGT showed fairly and significantly positive correlations; and TGC, CHOL, TPROT, and ALB showed fairly and significantly negative correlations (r = 0.3-0.59; p < 0.01). Measuring the surface temperature of the whole body or head can be a useful tool in evaluating the metabolic response of cows because it has demonstrated an association with inflammation (TNFα, eHsp70), endocrine response (CORT, T3, T4), the increased use of glucose and decreased use of lipids for energy purposes (INS, NEFA, GLU, and RQUICKI), and protein catabolism (ALB, TPROT, urea, Creat), which underlies thermolysis and thermogenesis in cows under heat stress. In future research, it is necessary to examine the causality between body surface area and metabolic parameters.

Economic impact of subclinical mastitis treatment in early lactation using intramammary nisin

Treatment of subclinical mastitis (SCM) during lactation is rarely recommended due to concerns related to both antimicrobial usage and costs associated with milk discard. Nisin is a naturally produced antimicrobial peptide with a Gram-positive spectrum that, when given to dairy cows, does not require milk discard. We evaluated the economic impact of treatment of SCM during early lactation using a nisin-based intramammary treatment under different scenarios which included various treatment costs, milk prices, and cure rates. We stochastically simulated the dynamics of SCM detected during the first week of lactation. The net economic impact was expressed in US dollars per case. The probabilities of an event and their related costs were estimated using a model that was based on pathogen-specific assumptions selected from peer-reviewed articles. Nisin cure rates were based on results of pivotal studies included in the FDA approval submission. Based on our model, the average cost of a case of intramammary infection (i.e., only true positive cases) in early lactation was $170 (90th percentage range = $148 to $187), while the cost of a clinical mastitis case was $521 (90th percentage range = $435 to $581). Both estimates varied with etiology, parity, and stage of lactation. When comparing the net cost of SCM cases (i.e., CMT-positive tests) detected during the first week of lactation, nisin treatment generated an average positive economic impact of $19 per CMT-positive case. Use of nisin to treat SCM was beneficial 93% of the time. Based on the sensitivity analysis, treatment would result in an economically beneficial outcome for 95% and 73% of multiparous and primiparous cows, respectively. At the herd level, use of intramammary nisin to treat SCM in cows in early lactation was economically beneficial in most tested scenarios. However, economic impact was highly influenced by factors such as rate of bacteriological cure, cost of treatment, and parity of affected animal. These factors should be considered when deciding to use nisin as a treatment for SCM.

Effects of dietary palmitic acid and oleic acid ratio on milk production, nutrient digestibility, blood metabolites, and milk fatty acid profile of lactating dairy cows

Adequate energy supply is a crucial factor for maintaining the production performance in early lactating cows. Adding fatty acids to diets can improve energy supply, while the effect could be related to the chain length and degree of saturation of fatty acids. This study was conducted to evaluate the effect of different ratios of palmitic acid (C16:0) to oleic acid (cis-9 C18:1) on the production performance, nutrient digestibility, blood metabolites and milk fatty acids profile in early lactating dairy cows. Seventy-two multiparous Holstein cows (63.5 ± 2.61 d in milk) blocked by parity (2.39 ± 0.20), body weight (668.3 ± 20.1 kg), body condition score (3.29 ± 0.06), and milk yield (47.9 ± 1.63 kg) were used in a completely randomized design. Cows were divided into 3 groups with 24 cows in every group. Cows in 3 treatments were provided iso-energy and iso-nitrogen diets, whereas the C16:0 to cis-9 C18:1 ratio was different: (1) 90.9% C16:0 + 9.1% cis-9 C18:1 (90.9:9.1); (2) 79.5% C16:0 + 20.5% cis-9 C18:1 (79.5:20.5); (3) 72.7% C16:0 + 27.3% cis-9 C18:1 (72.7:27.3). Fatty acids were added at 1.3% in dry matter basis. Although the dry matter intake fat-corrected milk yield and energy-corrected milk yield were not affected, the milk yield, milk protein yield and feed efficiency increased linearly with the increasing of cis-9 C18:1 ratio. The milk protein percentage and milk fat yield did not differ among treatments, whereas the milk fat percentage tended to decrease linearly with the increasing of cis-9 C18:1 ratio. The lactose yield increased linearly and lactose percentage tended to increase linearly with increasing cis-9 C18:1 ratio, whereas the percentage of milk total solids and somatic cell count decreased linearly. Though the changes of body condition score were not affected by treatments, the body weight loss decreased linearly with the increasing of cis-9 C18:1 ratio. The effect of treatment on nutrient digestibility was limited, except a linear increase in ether extract and neutral detergent fiber digestibility with the increasing of cis-9 C18:1 ratio. There was a linear increase in the concentrations of plasma glucose, whereas the triglyceride and nonesterified fatty acid concentration decreased linearly with the increasing of cis-9 C18:1 ratio. As the cis-9 C18:1 ratio increased, the concentration of de novo fatty acids decreased quadratically, while the mixed and preformed fatty acids increased linearly. In conclusion, increasing cis-9 C18:1 ratio could increase production performance and decrease body weight loss by increasing nutrient digestibility, and the ratio had the most powerful beneficial effect on early lactating cows suggested by 72.7:27.3.

How Does the Provision of Shade during Grazing Affect Heat Stress Experienced by Dairy Cows in Sweden?

Heat stress in dairy cows can cause an increase in body temperature and respiration rate, and a decreased feed intake leading to reduced production. Dairy cows are better at handling heat when they have access to shade. Therefore, this study aimed to determine the effects of providing shade to high-yielding dairy cattle during the summer in the Swedish climate. Twenty high-yielding Swedish Red dairy cows, held on pasture, were divided into two groups, one with access to shade (S) and one without (NS). Milk production was recorded daily and shade temperature and relative humidity were recorded at 10 min intervals at pasture. A major effect of heat stress was found in cows in early lactation in the NS group. In this group, a high mean temperature two days before and a high THI two days before affected the milk production negatively (p < 0.001), which was the same for the maximum temperature and maximum THI measured on the same day (p < 0.001). Increases in the mean temperature and THI two days before also affected milk production negatively (p < 0.05) for cows in early lactation in the S group, though to a lesser extent. This study suggests that dairy cows in early lactation benefit from access to shade during summer.

Associations of parity and lactation stage with the order cows enter the milking parlor

To explore the effect of lactation stage and parity on the milking order of cows, we collected milking order data of all lactating cows (n = 251) over a period of 12 wk in one commercial Swedish dairy cow herd using a herringbone milking parlor. Cows were kept in 2 housing groups (G1 and G2) and moved from G1 to G2 at approximately mid lactation. Two analyses were conducted to investigate if lactation stage (early: 2–49 d in milk, mid: 50–179 d in milk, and late ≥180 d in milk) and parity are associated with the entrance order to the parlor or a preference of entering a new milking line first. In G1 and G2, cows in first parity entered the milking parlor earlier than cows in higher parities. In addition, in G1 cows in early lactation entered the milking parlor earlier than cows in later lactation. Similar effects were observed for the preference of entering a new milking line first. No effect of mid versus late lactation could be observed in either G1 or G2. The study also found that cows tend to keep their rank within the milking order constant. The results of the study indicate that cows of presumably lower hierarchy (first parity and early lactation) leave the waiting area earlier compared with other cows. This should be considered when planning grouping strategies and preventive measures against mastitis pathogen transmission.

Genetic analysis of milk citrate predicted by milk mid-infrared spectra of Holstein cows in early lactation

Milk citrate is regarded as an early biomarker of negative energy balance in dairy cows during early lactation and serves as a suitable candidate phenotype for genomic selection due to its wide availability across a large number of cows through milk mid-infrared spectra prediction. However, its genetic background is not well known. Therefore, the objectives of this study were to (1) analyze the genetic parameters of milk citrate; (2) identify genomic regions associated with milk citrate; and (3) analyze the functional annotation of candidate genes and quantitative trait loci (QTL) related to milk citrate in Walloon Holstein cows. In total, 134,517 test-day milk-citrate phenotypes (mmol/L) collected within the first 50 d in milk on 52,198 Holstein cows were used. These milk-citrate phenotypes, predicted by milk mid-infrared spectra, were divided into 3 traits according to the first (citrate1), second (citrate2), and third to fifth parity (citrate3+). Genomic information for 566,170 SNPs was available for 4,479 animals. A multiple-trait repeatability model was used to estimate genetic parameters. A single-step GWAS was used to identify candidate genes for citrate and post-GWAS analysis was done to investigate the relationship and function of the identified candidate genes. The heritabilities estimated for citrate1, citrate2, and citrate3+ were 0.40, 0.37, and 0.35, respectively. The genetic correlations among the 3 traits ranged from 0.98 to 0.99. The genomic correlations among the 3 traits were also close to 1.00 across the genomic regions (1 Mb) in the whole genome, which means that citrate can be considered as a single trait in the first 5 parities. In total, 603 significant SNPs located on 3 genomic regions (chromosome 7, 68.569-68.575 Mb; chromosome 14, 0.15-1.90 Mb; and chromosome 20, 54.00-64.28 Mb), were identified to be associated with milk citrate. We identified 89 candidate genes including GPT, ANKH, PPP1R16A, and 32 QTL reported in the literature related to the identified significant SNPs. These identified QTL were mainly reported associated with milk fatty acids and metabolic diseases in dairy cows. This study suggests that milk citrate in Holstein cows is highly heritable and has the potential to be used as an early proxy for the negative energy balance of Holstein cows in a breeding objective.

Near-infrared spectroscopy analysis of blood plasma for predicting nonesterified fatty acid concentrations in dairy cows

During the transition period, dairy cows are often exposed to negative energy balance (NEB), leading to lipid mobilization from adipose tissue into nonesterified fatty acids (NEFA), a common indicator of heightened illness risk. This study aimed to use blood near-infrared (NIR) spectra data to classify NEB into high or low categories, based on early-lactation cow NEFA thresholds. We collected a total of 186 plasma samples from 100 Holstein cows. The samples were categorized into critical thresholds, based on previous literature, of ≥0.60 and ≥0.70 mEq/L for identifying high NEB. Spectral data were preprocessed before the development of the predictive modes, which included the implementation of multiplicative scatter correction, standard normal variate (SNV), and first and second derivatives. The classification was performed using partial least square discriminant analyses (PLS-DA), and predictive performance was assessed using leave-one-out cross-validation. Predictive quality for each class was evaluated through specificity, precision, sensitivity, and F1 score. The study showed promising results, with the SNV technique achieving higher F1 scores. The model found 72.7% specificity, 78.9% precision, 80.8% sensitivity, and 79.8% F1 score to classify animals with NEFA levels of ≥0.60 mEq/L, and 82.1% specificity, 78.7% precision, 80.8% sensitivity, and 79.7% F1 score to classify animals with NEFA levels ≥0.70 mEq/L. These results indicate that NIR spectroscopy could serve as a tool for detecting cows under severe NEB, also showing potential for broader application across the entire transition period, as the spectral signal carried relevant information regarding cow metabolism. Furthermore, the combination of predictors derived from plasma spectra and other cow-level information can lead to more accurate disease alerts, given their relationship with the NEB.

Effect of organic zinc supplementation on hematological, mineral, and metabolic profile in dairy cows in early lactation

Effect of organic zinc supplementation on hematological, mineral, and metabolic profile in dairy cows in early lactation

Comparison of two different anionic supplements and a low calcium diet fed to transition cows prepartum on DM intake, mineral homoeostasis and performance.

This study evaluates the effects of two rations with a positive dietary cation-anion difference (DCAD) and varying Ca content and two anionic diets on mineral homoeostasis and performance in early lactation cows. For this purpose, 48 pregnant dairy cows stratified for mature equivalent milk production, parity, body condition score (BCS), and BW were randomly assigned to four treatment groups and fed the following rations during the last 3weeks of gestation: LC: low Ca (0.24% Ca, 1.14% K, DCAD: +86mEq/kg DM), HC: high Ca (1.23% Ca, 1.17% K, DCAD: +95mEq/kg DM), AS: Anionic salt (1.21% Ca, 1.21% K, DCAD: -112mEq/kg DM, and SC: SoyChlor (1.28% Ca, 1.16% K, DCAD: -115mEq/kg DM). After parturition, all animals were fed a common postpartum diet. Data were collected until 21days in milk. Urinary pH was significantly decreased with the AS and SC treatment in comparison to the LC and HC groups. The highest prepartum DM intake (DMI) was found in the LC group, while DMI in AS cows was lowest. Postpartum, DMI was significantly greater in LC and SC cows than in animals fed the HC and AS rations. Prepartum serum concentrations of Ca, P, and Mg as well as postpartum serum concentrations of P and Mg did not differ, while postpartum Ca was lower in the HC group, especially 24 and 48h after parturition. The greatest energy-corrected milk (ECM) yield was observed in cows fed the LC ration prepartum. Interestingly, milk protein production was lower in SC cows compared to LC, HC and AS. This study indicates that a ration containing a restricted Ca content fed prepartum is as suitable as a low DCAD diet to improve Ca balance without compromising DMI and performance.

Effects of rumen-protective γ-aminobutyric acid additive on lactation performance and serum biochemistry in heat-stressed cows.

In the context of global warming, heat stress has become one of the major stress factors limiting dairy cattle production. Although many methods have been explored to help cows mitigate the negative effects of heat stress during the hot summer months, maintaining the performance of high-yielding cows under heat stress is still a great challenge. The aim of this trial was to investigate the effect of RP-GABA in the diet on milk yield, milk composition and serum biochemical parameters in heat-stressed cows. Twenty Chinese Holstein cows in early lactation (51.00 ± 4.92 kg milk/d, 71 ± 10.94 d in milk and 2.68 ± 0.73 parities) were included in this experiment and randomly divided into four groups (n = 5/group). The four experimental groups consisted of one control group (0 g RP-GABA/d) and three treatment groups, given 5, 7.5 and 10 g RP-GABA/d of dry matter (DM) per cow, respectively. The results showed that supplementing high-yielding cows with 10 g/d of RP-GABA improved milk protein production but had no effect on the improvement of other production performance, the alleviation of heat stress in cows, or the improvement of immune function and antioxidant capacity. Ultimately, we conclude that the supplementation of 10 g/d RP-GABA to heat-stressed, high-yielding dairy cows can provide a degree of performance enhancement. Furthermore, our study provides some reference for nutritional improvement measures for summer heat stress in dairy cows, especially high-yielding cows.

Associations of cow- and herd-level factors during the dry period with indicators of udder health in early-lactation cows milked by automated milking systems

This observational study aimed to determine the association of cow-level factors and herd-level housing and management practices during the dry period with indicators of udder health in early-lactation cows in automated milking system (AMS) herds. Data were collected from 166 commercial AMS dairy farms (mean ± standard deviation = 116 ± 111 milking cows; range = 39 to 1,200) across Canada between October 2018 and September 2020. Information on herd demographics, housing, and management practices was obtained on each farm using 2 surveys. On each farm, we selected all cows that had available Dairy Herd Improvement (DHI) somatic cell count (SCC) data for their last milk test before dry-off (>250 d in milk) and their first milk test after calving (5-45 d in milk). Data from 14,007 cows were included after excluding cows with a dry period of <30 d and >120 d. Using the SCC data, we calculated for each cow the somatic cell score (SCS) for the last milk test before dry-off (PreSCS) and the first milk test after calving (PostSCS), which we then averaged per herd at a test-day level. Intramammary infection (IMI) was estimated using cow SCC data. Each cow was classified as not infected (SCC <200,000 cells/mL) or infected (SCC ≥200,000 cells/mL) at her last milk test before dry-off and her first milk test after calving. Based on this classification, cows were further categorized as never infected, always infected, new IMI, or cured IMI. At the cow level, a higher PostSCS was associated with longer dry periods. The odds of having a new IMI were higher for cows of higher parity and that had lower 305-d milk yield before dry-off. Cows with lower parity were more likely to cure an IMI. At the herd level, a higher 305-d milk yield before dry-off was associated with a lower incidence of new IMI and a higher incidence of cured IMI. Separating cows into a different pen as preparation for dry-off tended to be associated with a lower PostSCS and incidence of new IMI. At dry-off, herds that used teat sealants and blanket antibiotic dry cow therapy also had lower PostSCS. During the dry period, housing cows in different groups was associated with a higher PostSCS and a lower incidence of cured IMI, while housing cows in both pack pens and stalls compared with only pack pens was associated with a lower incidence of new IMI. Finally, placing cows onto the AMS to be milked one or more days after calving tended to be associated with a lower PostSCS compared with placing them in the AMS within the first day postpartum. In summary, indicators of udder health in early-lactation cows in AMS herds were associated with several cow-level factors and herd-level housing and management practices before dry-off, at dry-off, during the dry period, and at the beginning of lactation. Thus, if some of the associations identified are causal, AMS producers may be able to improve udder health through modifications of housing and management practices.

Efecto del clima sobre la respuesta térmica en vacas de diferentes grupos raciales en trópico bajo

Objective. The main idea of this study was to quantify the relationship between climatic variables and tympanic body temperature recorded through the use of wireless sensors in grazing cows located in low tropic. Material and methods. The tympanic temperature of twenty-eight cross breed grazing cows in early lactation was monitored. The sensors were manually installed in the tympanic cavity, recording hourly for 17 days. The climate data was obtained from the network of weather stations of the Centro de Investigación de la Caña de Azúcar “Cenicaña”, which is a research center for sugarcane located in Cali, Colombia, this data was analyzed for the same time interval of the temperature. The information was analyzed using descriptive statistics, correlation matrices and Random Forest models, through the R software. Results. From the physiological data from automatic collection systems, the response variables that would allow the evaluation of thermoregulation processes were analyzed using big data. We find that the variables environmental temperature, relative humidity and, solar radiation were the factors that most influenced the homeothermic adaptation process of the animals. Conclusions. The introduction of remote devices, and the use of a large amount of data for the analysis of physiological indicators, avoid modifying natural animal behavior and emerges as an important diagnostic and management strategy in the livestock farm, helping in the studies of heat stress, physiological adaptation and, prevalence to hemotropic diseases, which reduce the productivity of the systems.

Identification and Classification of Long Non-Coding RNAs in the Mammary Gland of the Holstein Cow.

The mammary glands, responsible for milk secretion, are regulated at a local level by various hormones, growth factors, non-coding RNAs, and other elements. Recent research has discovered the presence of lncRNAs in these glands, with suggestions that they may be essential for the maintenance and function of mammary glands. Besides directly controlling the gene and protein expression, lncRNAs are believed to play a significant part in numerous physiological and pathological processes. This study focused on examining the mammary gland tissues of Chinese Holstein cows, to identify and categorize long non-coding RNAs (lncRNAs). The research intended to distinguish lncRNAs in the mammary tissues of Holstein cows and contrast them between lactation and non-lactation periods. In this study, mammary gland tissues were sampled from three Holstein cows in early lactation (n = 3, 30 days postpartum) and non-lactation (n = 3, 315 days postpartum) on a large dairy farm in Jiangsu province. Mammary tissue samples were collected during early lactation and again during non-lactation. In total, we detected 1905 lncRNAs, with 57.3% being 500 bp and 612 intronic lncRNAs. The exon count for lncRNAs varied from 2 to 10. It was observed that 96 lncRNA expressions markedly differed between the two stages, with 83 genes being upregulated and 53 downregulated. Enrichment analysis results revealed that Gene Ontology (GO) analysis was primarily abundant in cellular processes. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that target genes were predominantly abundant in metabolic pathways, fatty acid biosynthesis, the immune system, and glycosphingolipid biosynthesis. This study analyzed the expression profile and characteristics of lncRNAs in the mammary gland tissues of Holstein cows during both lactation and non-lactation stages, forming a foundation for further investigation into the functional roles of lncRNAs in Holstein cows throughout lactation.

Validating genomic prediction for nitrogen efficiency index and its composition traits of Holstein cows in early lactation.

Nitrogen (N) use efficiency (NUE) is an economically important trait for dairy cows. Recently, we proposed a new N efficiency index (NEI), that simultaneously considers both NUE and N pollution. This study aimed to validate the genomic prediction for NEI and its composition traits and investigate the relationship between SNP effects estimated directly from NEI and indirectly from its composition traits. The NEI composition included genomic estimated breeding value of N intake (NINT), milk true protein N (MTPN) and milk urea N yield. The edited data were 132,899 records on 52,064 cows distributed in 773 herds. The pedigree contained 122,368 animals. Genotypic data of 566,294 SNP was available for 4514 individuals. A total of 4413 cows (including 181 genotyped) and 56 bulls (including 32 genotyped) were selected as the validation populations. The linear regression method was used to validate the genomic prediction of NEI and its composition traits using best linear unbiased prediction (BLUP) and single-step genomic BLUP (ssGBLUP). The mean theoretical accuracies of validation populations obtained from ssGBLUP were higher than those obtained from BLUP for both NEI and its composition traits, ranging from 0.57 (MTPN) to 0.72 (NINT). The highest mean prediction accuracies for NEI and its composition traits were observed for the genotyped cows estimated under ssGBLUP, ranging from 0.48 (MTPN) to 0.66 (NINT). Furthermore, the SNP effects estimated from NEI composition traits, multiplied by the relative weight were the same as those estimated directly from NEI. This study preliminary showed that genomic prediction can be used for NEI, however, we acknowledge the need for further validation of this result in a larger dataset. Moreover, the SNP effects of NEI can be indirectly calculated using the SNP effects estimated from its composition traits. This study provided a basis for adding genomic information to establish NEI as part of future routine genomic evaluation programs.