Influence of clinical mastitis during early lactation on reproductive performance of Jersey cows

Lipopolysaccharide impairs the in vitro growth, steroidogenesis, and maturation of oocyte-cumulus-granulosa cell complexes derived from bovine early antral follicles

In postpartum dairy cows, lipopolysaccharide (LPS) derived from gram-negative bacteria causes uterine or mammary inflammation, resulting in low fertility. The present study aimed to investigate the effect of LPS on the in vitro growth (IVG), steroidogenesis, and maturation of oocyte-cumulus-granulosa cell complexes (OCGCs) derived from bovine early antral follicles. OCGCs were isolated from bovine early antral follicles (0.5-1 mm in diameter) and cultured in vitro for 12 days using media containing 0 (control), 0.01, or 1 μg/mL of LPS. The viability, cavity formation, and oocyte diameter of the OCGCs, as well as the concentrations of estradiol (E2) and progesterone (P4) in the IVG culture media, were determined. After IVG culture, oocytes collected from viable OCGCs were matured in vitro (IVM) in a medium without LPS. The nuclear maturation rate and the mitochondrial membrane potential of oocytes were determined. Bovine oocytes and cumulus-granulosa complexes derived from early antral follicles expressed genes encoding LPS receptor complex, such as toll-like receptor 4 (TLR4). Immunohistochemistry analysis further localized TLR4 expression predominantly in follicular granulosa and theca cells of early antral follicles. The viability of OCGCs and cavity formation in OCGCs were lower in the 0.01 and 1 μg/mL LPS groups than in the control group. No significant difference in oocyte diameter was observed between the treatment groups throughout the culture period. Moreover, E2 production was suppressed in the 0.01 and 1 μg/mL LPS groups from Days 4-8, whereas P4 production increased in the 1 μg/mL LPS group from Days 0-8. The nuclear maturation rate after IVM was lower in the 0.01 and 1 μg/mL LPS groups than in the control group. The mitochondrial membrane potential of post-IVM oocytes was lower in the 0.01 and 1 μg/mL LPS groups than in the control group. Taken together, these results indicate that LPS inhibited the growth and steroidogenesis of OCGCs and the meiosis and mitochondrial function of oocytes derived from early antral follicles. This study suggests that the detrimental effects of LPS on developing oocytes may contribute to long-term decreased fertility in postpartum dairy cows.

Mastitis impact on high-yielding dairy farm's reproduction and net present value

Poor udder health can have a negative impact on milk production and reproductive performance, which reduces the net present value (NPV) of dairy farms. The aim of this study is therefore to investigate the relationship between clinical mastitis and NPV and the financial impact of impaired reproductive function. For this purpose, 473 dairy cows were included in our study, 146 cows with clinical mastitis (CM group) and 327 clinically healthy cows (CH group) from a high-yielding dairy farm in Romania, milking approximately 780 dairy cows with an average milk production of 46 kg milk/day. We found that, in contrast to CH cows, CM cows had a significantly lower conception rate at first service (58.2% vs. 41.7%, p < 0.05), third service (45.3% vs. 30.2%, p < 0.05), and total services (49.2% vs. 36.4%, p < 0.05). However, this positive effect was not observed for the average days open, which were significantly lower in CM cows than in CH cows (112 ± 4.3 days vs. 142 ± 3.1 days, p < 0.05). The fact that the non-pregnant CH cows had higher somatic cell counts (>400,000 SCC/mL) in their milk around artificial insemination (AI) and 1 month earlier than the pregnant cows (<250,000 SCC/ml) supports the idea that poor uterine health affects the reproductive activity of high-yielding cows. However, by using the UW-DairyRepro$ decision support tool, we found that despite the impairment of reproductive function in dairy cows, the largest negative impacts on NPV are still the cost of milk loss (US$14,439.4/farm/year) and treatment costs (US$4,380/farm/year). We considered the costs associated with poor reproductive function in the CM group (US$3,577/farm/year) as an additional cost of mastitis. Finally, it appears that the impact of mastitis on reproduction is associated with a lower chance of conception than it is with a daily risk of services.

The impact of inflammatory stress on hypothalamic kisspeptin neurons: Mechanisms underlying inflammation-associated infertility in humans and domestic animals

Inflammatory diseases attenuate reproductive functions in humans and domestic animals. Lipopolysaccharide (LPS), an endotoxin released by bacteria, is known to disrupt female reproductive functions in various inflammatory diseases. LPS administration has been used to elucidate the impact of pathophysiological activation of the immune system on reproduction. Hypothalamic kisspeptin neurons are the master regulators of mammalian reproduction, mediating direct stimulation of hypothalamic gonadotropin-releasing hormone (GnRH) release and consequent release of gonadotropins, such as luteinizing hormone (LH) and follicle-stimulating hormone from the pituitary. The discovery of kisspeptin neurons in the mammalian hypothalamus has drastically advanced our understanding of how inflammatory stress causes reproductive dysfunction in both humans and domestic animals. Inflammation-induced ovarian dysfunction could be caused, at least partly, by aberrant GnRH and LH secretion, which is regulated by kisspeptin signaling. In this review, we focus on the effects of LPS on hypothalamic kisspeptin neurons to outline the impact of inflammatory stress on neuroendocrine regulation of mammalian reproductive systems. First, we summarize the attenuation of female reproduction by LPS during inflammation and the effects of LPS on ovarian and pituitary function. Second, we outline the inhibitory effects of LPS on pulsatile- and surge-mode GnRH/LH release. Third, we discuss the LPS-responsive hypothalamic-pituitary-adrenal axis and hypothalamic neural systems in terms of the cytokine-mediated pathway and the possible direct action of LPS via its hypothalamic receptors. This article describes the impact of LPS on hypothalamic kisspeptin neurons and the possible mechanisms underlying LPS-mediated disruption of LH pulses/surge via kisspeptin neurons.

Mastitis: What It Is, Current Diagnostics, and the Potential of Metabolomics to Identify New Predictive Biomarkers

Periparturient diseases continue to be the greatest challenge to both farmers and dairy cows. They are associated with a decrease in productivity, lower profitability, and a negative impact on cows’ health as well as public health. This review article discusses the pathophysiology and diagnostic opportunities of mastitis, the most common disease of dairy cows. To better understand the disease, we dive deep into the causative agents, traditional paradigms, and the use of new technologies for diagnosis, treatment, and prevention of mastitis. This paper takes a systems biology approach by highlighting the relationship of mastitis with other diseases and introduces the use of omics sciences, specifically metabolomics and its analytical techniques. Concluding, this review is backed up by multiple studies that show how earlier identification of mastitis through predictive biomarkers can benefit the dairy industry and improve the overall animal health.

Associations of somatic cell count with milk yield and reproductive performance in grazing dairy cows

Poor udder health status can have a detrimental effect on milk yield and reproductive performance, leading to reductions in the dairy farm profit. The objective of this retrospective longitudinal study was to assess the associations of somatic cell count (SCC) with daily milk yield and reproductive performance. A database with 1,930,376 lactations from 867 Argentinean grazing dairy herds records collected for 14 years was used. The association of the evolution of SCC (healthy vs. new case vs. cured vs. chronic; with 150,000 SCC/mL as threshold) and of the severity of SCC [mild (150,000--400,000 SCC/mL) vs. moderate (400,000-1,000,000 SCC/mL) vs. severe (>1,000,000 SCC/mL)] with the odds for conception were estimated. Finally, the associations of the linear score of SCC (LS-SCC) with daily milk yield were estimated depending on parity and milk production quartile. The odds ratios (CI 95%) for conception at first service were 0.921 (0.902-0.941), 0.866 (0.848-0.884), and 0.842 (0.826-0.859) for the new case, cured, and chronic cows compared with healthy cows, respectively. Also, the odds ratios (CI 95%) for conception were 0.902 (0.881-0.925), 0.837 (0.808-0.866) and 0.709 (0.683-0.736) for mild, moderate and severe cases compared with healthy cows, respectively. An increase of one point of LS-SCC was associated with decreases of 0.349, 0.539, and 0.676 kg in daily milk yield for first-, second-, and third-lactation cows, respectively. In conclusion, SCC is negatively associated with the risk for conception and with daily milk yield in grazing dairy cows. This negative relationship with conception is higher when SCC increase occurs after the service date and it is influenced by severity of mastitis, and in the case of milk yield, the negative association is influenced by parity, milk production quartile, and severity of mastitis.

Inhibition of lipopolysaccharide-induced suppression of luteal function in isolated perfused bovine ovaries

Recently, we observed that lipopolysaccharide (LPS) suppresses corpus luteum (CL) function in isolated perfused ovaries. It remained unclear if this suppression was due to increased luteal PGF_2α secretion or LPS-induced apoptosis. Therefore, possible impacts of PGF_2α and LPS were inhibited by a non-steroidal anti-inflammatory drug (flunixin) and an endotoxin-binding agent (polymyxin B), respectively. Bovine ovaries with a mid-cycle CL were collected immediately after slaughter and perfused for 240 min. After 50 min of equilibration, either flunixin or polymyxin B (5 μg/ml of each) were added to the perfusion medium of six ovaries, respectively. All ovaries (n = 12) were treated with E.coli LPS (0.5 μg/ml) 60 min after the onset of perfusion, and received 500 I.U. of hCG after 210 min of perfusion. Progesterone and PGF_2α were measured in the effluent perfusate every 10 and 30 min, respectively. Biopsies of the CL were collected every 60 min to determine the mRNA expression of the cytokine TNFA and factors of apoptosis (CASP3, -8). Flunixin-treatment inhibited the increase of PGF_2α after LPS-challenge that was observed in the polymyxin B-treated (PX-LPS) ovaries. After hCG-stimulation, progesterone secretion increased (P< 0.05) in group PX-LPS but not in the flunixin-treated (F-LPS) ovaries. Compared to initial values before LPS-challenge, luteal mRNA expression of TNFA and CASP3 was increased (P< 0.05) in group F-LPS at 120 and 180 min, respectively, and those of CASP8 was decreased (P< 0.05) in PX-LPS at 60 and 120 min after LPS-treatment. In conclusion, although flunixin managed to inhibit PGF_2α, it did not suffice to successfully prevent LPS-induced apoptosis. However, endotoxin-binding polymyxin B resulted in luteal responsiveness to hCG after LPS-challenge.

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

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

Intergenerational cycle of disease: Maternal mastitis is associated with poorer daughter performance in dairy cattle

Adverse prenatal environments, such as maternal stress and infections, can influence the health and performance of offspring. Mastitis is the most common disease in dairy cattle, yet the intergenerational effects have not been specifically investigated. Therefore, we examined the associations between the dam's mammary gland health and daughter performance using somatic cell score (SCS) as a proxy for mammary health. Using data obtained from Dairy Records Management Systems (Raleigh, NC), we linked daughter records with their dam's records for the lactation in which the daughter was conceived. Linear and quadratic relationships of dam mean SCS with the daughter's age at first calving (AFC; n = 15,992 daughters, 4,366 herds), first- (n = 15,119 daughters, 4,213 herds) and second-lactation SCS (n = 3,570 daughters, 1,554 herds), first- and second-lactation mature-equivalent 305-d milk yield, and milk component yields were assessed using mixed linear regression models. We uncovered a phenomenon similar to those found in human and mouse models examining prenatal inflammation effects, whereby daughters born from dams with elevated SCS had poorer performance. Dam mean SCS was positively associated with daughter's AFC and first- and second-lactation mean SCS. Furthermore, for every 1-unit increase in dam mean SCS, daughter's first- and second-lactation mature-equivalent fat yield declined by 0.34% and 0.91% (-1.6 ± 0.49 kg, -4.0 ± 1.0 kg, respectively), although no effect was found on first- or second-lactation milk or milk protein yield. When accounting for genetics, daughter SCS, and AFC (first lactation only), dam mean SCS was associated with reduced second-lactation milk fat yield (-3.5 ± 1.8 kg/unit SCS), and a tendency was found for first-lactation milk fat yield (-1.9 ± 1.0 kg/unit SCS). Taken together, the association of greater dam mean SCS with lesser daughter milk fat yield is likely due to a few underlying mechanisms, in particular, a predisposition for mastitis and alterations in the epigenome controlling milk fat synthesis. As such, future studies should examine epigenetic mechanisms as a potential underpinning of this phenomenon.

Effect of dry period therapy on prevalence of mastitis in buffaloes in Haryana

The study attempts to compute the effect of dry period therapy on occurrence of mastitis in buffaloes with the help of control (164 buffaloes) and treatment (330 buffaloes) groups at different stages as per disease diagnostic protocol. The data pertains to the year 2018-19. The study concludes overall prevalence of SCM at dry-off was 83.81% and at 5 days postpartum was 38.87% at animal level. In treatment group, prevalence of SCM was 89.70% and 28.48% at dry-off and 5 days postpartum respectively whereas 73.17% and 62.8% in control group. The most prevalent udder pathogens isolated from composite milk samples at dry off were coagulase-negative Staphylococcus, representing 41.29% of all recovered isolates followed by other gram positive, Streptococcus spp. Overall, 63.02% of buffaloes with IMI were cured during the dry period. Buffaloes receiving dry period therapy were 3.85 times more likely to cure.

Effects of clinical mastitis and puerperal diseases on reproductive efficiency of dairy cows

The objective of this study was to evaluate the effects of clinical mastitis (CM) occurring before or after the first AI postpartum, and puerperal diseases (PD) on the pregnancy per artificial insemination (P/AI), number of AI/conception, and days open (DO) of two different dairy herds (Girolando and Holstein). The CM, PD (retained placenta and metritis), and reproductive data were collected from two dairy farms throughout 1 year. Both farms were located in the southern region of Minas Gerais State, Brazil. One herd was composed of Girolando cows and the other of Holstein cows. Cows were inseminated after estrus detection or submitted to timed AI. Only CM cases (clots in milk accompanied or not by udder inflammation) that occurred before or after first AI postpartum (from calving until 35 days after the first AI) were considered. There were no effects of CM, PD, or both diseases on the reproductive efficiency of the Girolando herd. In the Holstein herd, a reduce P/AI and prolonged DO were verified for those affected by ≥ 2 CM cases. Holstein cows with CM also required more inseminations to become pregnant. A decrease in the P/AI and an increase in the number of AI/conception and DO were observed in cows of the Holstein herd that developed only CM, only PD, and for those diagnosed with both diseases. In summary, considering that some management differences exist between the two dairy farms, CM occurrence (before or after the first AI postpartum) and puerperal diseases negatively affected the reproductive efficiency of the Holstein herd. However, these diseases did not compromise the reproductive efficiency of the Girolando herd.

Prevalence of enterotoxins and other virulence genes of Staphylococcus aureus caused subclinical mastitis in dairy cows

BACKGROUND AND AIM

Milk production is one of the main props for the national economy. One of the crucial problems in this industry is subclinical mastitis, which harms this industry that considered the backbone of the economy. It is an infectious and zoonotic disease; the infection can spread between dairy animals through milkers' hands, and milking machines, while the human infection occurs due to the consumption of apparently hygienic milk. Staphylococcus aureus is one of the main causative agents of clinical and subclinical mastitis. It is also considered one of the bacteria incriminated in food intoxication of humans due to its virulence factors as enterotoxins and toxic shock syndrome. The current study was designed to assess the prevalence of S. aureus and its enterotoxins, as well as, its other virulence factors in milk collected from cows that suffer from subclinical mastitis.

MATERIALS AND METHODS

Sixty cows were collected from different dairy farms located in Assiut Governorate, Egypt. These cows were subjected to the clinical examination of the udder and its lymph nodes before sampling. Milk samples were collected from clinically healthy udders. All the milk samples were examined by California mastitis test (CMT), polymerase chain reaction (PCR), and enzyme-linked immunosorbent assay (ELISA) for confirmation subclinical mastitis, presence of S. aureus and its enterotoxins genes and other virulence factors in the examined milk samples.

RESULTS

The cows included in the current study had healthy udders. The sixty collected milk samples were tested by CMT. 48/60 (80.0%) were positive samples; from the 48 positive samples, 46 (95.83%) samples were confirmed positive by S. aureus 16s rRNA PCR assay. Multiplex PCRs confirmed the presence of staphylococcus enterotoxin gene C (sec) in one sample, staphylococcus enterotoxin gene D (sed) in 23 samples, while ELISA assay confirmed the presence of the same enterotoxin in only two samples. On the other hand, other groups of genes responsible for some other virulence factors of S. aureus like the extracellular thermostable nuclease (nuc) gene were found in 33 samples, while toxic shock syndrome (tsst) gene and methicillin restraint S. aureus (mecA) gene were not detected in this study.

CONCLUSION

Subclinical mastitis is one of the hidden factors that adversely affect the health of both animals and humans. The milk is usually appeared good and may be consumed by humans especially children; however, it causes severe public health problems. In addition, the infected animals with this form of mastitis can spread the infection to other dairy animals and may be turned to a clinical case of contagious mastitis that may be ended by animal culling or death. S. aureus is one of the main causes of subclinical mastitis in cattle. In addition to extracellular thermostable nuclease (nuc) gene, staphylococcus enterotoxin gene C (sec) and staphylococcus enterotoxin gene D (sed) are the most common virulence genes confirmed in subclinical mastitis milk. These results highlighted the need to apply more hygienic measures in the dairy farms to avoid spreading the infection between animals to ensure the production of safe and healthy food to humans.

Effects of various mastitis treatments on the reproductive performance of cows

BACKGROUND

The purpose of the study described here was to evaluate the effects of different supportive treatments - such as antioxidants, immunomodulators, and nonsteroidal anti-inflammatory drugs (NSAIDs) - in mastitic cows treated with intramammary antibiotics on the efficacy of mastitis therapy and fertility indices. Fertility indices, including time to first insemination, conception rate, time between calving and conception (open days), and number of services per conception (insemination index), were evaluated for 300 dairy cows. Sixty cows without apparent clinical signs of mastitis were assigned 100 days after calving to a Control group. Another 240 cows with clinical mastitis were systematically divided into four experimental groups (I-IV) of 60 cows each. All mastitic cows were treated with approved intramammary antibiotics in recommended doses. Cows in Group I were treated with intramammary antibiotics only. Cows in Groups II, III, and IV, received intramammary antibiotic therapy and a single injection with antioxidants, an immunomodulator (lysozyme dimer), or an NSAID (flunixin meglumine), respectively.

RESULTS

The lowest treatment efficacy of mastitic quarters and cows was noted in Group I (51.6 and 53.3%; p > 0.05). The best recovery rate was noted in Group II (63.3 and 66.7%; p > 0.05), followed by Group III (58.3 and 60.9%) and Group IV (58.3 and 58.0%; p > 0.05). The above data did not differ statistically (p > 0.05). The animals with mastitis (Groups I-IV) showed prolonged time to first insemination, more open days, higher insemination index, and lower conception rate than the control cows (p <  0.05). The conception rate of healthy cows and of successfully treated cows was insignificantly lower than that of cows required prolonged antibiotic therapy. Supportive treatments improved the mastitis recovery rate compared with intramammary antibiotics only. The efficacy of mastitis treatments affected the reproduction indices: in cows requiring prolonged treatment with antioxidants, a shorter time to first insemination was needed than in other groups (p <  0.05). Fewer days open were observed between the group with antioxidants and the control group (p <  0.05).

CONCLUSIONS

Clinical mastitis negatively affects reproductive indices (days open, pregnancy rate after first AI, NSC) in dairy cows. Different types of supportive medicine, such as antioxidants (vitamin C and E, and β-carotene), lysozyme dimer, or NSAID can be useful in improving fertility in mastitis cows treated with antibiotic only. It has been proven that each supportive treatment improved antibiotics efficiency and the antibiotic combined with the antioxidants was the most effective treatment.

Influence of pathogens causing clinical mastitis on reproductive variables of dairy cows

In dairy cattle, mastitis is a disease of the mammary gland caused by pathogens such as bacteria, viruses, fungi, and algae. Mastitis causes economic losses to dairy farms as well as public health concerns. The reproductive efficiency of commercial dairy herds has important implications for the economic success of dairy operations and is strongly associated with the health status of cows. Mastitis has previously been linked with decreased fertility of dairy cows, but the effect of specific pathogens on the severity of fertility reduction is still unclear. In this study, cows diagnosed with mastitis caused by major pathogens (Staphylococcus aureus, Streptococcus agalactiae, Escherichia coli, Klebsiella spp., Mycoplasma spp., and environmental Streptococcus) needed more artificial inseminations (AI) than did cows with mastitis caused by minor pathogens (coagulase-negative Staphylococcus and Corynebacterium spp.) and healthy cows. Cows diagnosed with mastitis, independent of what pathogen was causing mastitis, had more days open compared with nonmastitic cows. The percentage of cows that successfully established pregnancy at first AI was greater for the control group than for the major pathogens group but not significantly different from the minor pathogens group. Pregnancy loss was lower in the control group than in the major pathogens group; however, there was no difference compared with the minor pathogen group. Mastitis caused by gram-negative bacteria decreased the percentage of pregnancy per first AI and increased days open and pregnancy loss compared with the control group. Cows with mastitis caused by gram-positive bacteria also had increased days open compared with control cows. This study shows that different mastitis-causing bacteria can affect the fertility of cows differently. Mastitis events caused by major pathogens and gram-negative bacteria were associated with the greatest decrease in reproductive efficiency.

Association of lameness and mastitis with return-to-service oestrus detection in the dairy cow

Oestrus detection is an important part of maintaining efficient reproductive performance in dairy herds. Both lameness and mastitis are common diseases of dairy cows that may impact oestrus detection. A set of data from 28 herds identified as having good recording of clinical mastitis and lameness incidents was used for the study. Logistic regression was used to identify associations between disease episodes within 100 days of insemination and changes in the probability of reinsemination at either 18-24 or 19-26 days after an unsuccessful insemination. Population attributable risk was calculated to understand the impact these diseases may have at a herd level. Lameness 0-28 days after the first insemination of the interval decreased the odds of a reinsemination at an appropriate time by approximately 20 per cent. Clinical mastitis 1-28 days prior to the first insemination of the interval increased the odds of reinsemination at the expected time by approximately 20 per cent. The associations were similar for either interservice interval outcome. Population attributable risk suggested that the effect of these diseases on the probability of reinsemination at the expected time at a population level would likely be extremely small.

Quantifying the effects of mastitis on the reproductive performance of dairy cows: A meta-analysis

The objective of this study was to conduct a meta-analysis to quantitatively characterize the effects of mastitis on the reproductive performance of dairy cows as well as to identify factors that interact with this relationship. A total of 29 publications were identified that contributed 24, 41, 27, 38, and 13 trial results to the meta-analysis of how mastitis is related to time to first service (TFS), days open (DO), services per conception (SPC), pregnancies per insemination at first service (FSP/AI) and pregnancy loss (PL), respectively. The meta-analyses were conducted using multilevel linear mixed-effects models. Overall, high levels of heterogeneity were present and meta-regression models only explained a small amount of heterogeneity. Results suggest that cows with mastitis pre-first insemination experience, on average, an additional 13.29 d to first service [95% confidence interval (CI): 6.64, 19.95] when compared with cows with no mastitis in the same time period. Moreover, in relation to cows with no mastitis in the same time period, 22.34 additional DO (95% CI: 12.89, 31.79) were estimated, on average, for cows with clinical mastitis at pre-insemination leading to conception. Additionally, 32.41 added DO (95% CI: 20.58, 44.25) were estimated, on average, for cows with clinical mastitis at pre- or post-insemination leading to conception compared with cows with no mastitis in the same time period. Finally, 20.03 additional DO (95% CI: 3.11, 36.95) were estimated, on average, for cows with subclinical mastitis pre- or post-insemination leading to conception compared with cows with no mastitis in the same time period. Effect size estimates from the meta-regression models for SPC, in relation to cows with no mastitis in the same time period, suggest that, on average, SPC increases by 0.46 inseminations (95% CI: 0.30, 0.62) for a cow experiencing mastitis pre-insemination leading to conception. When mastitis occurs either pre- or post-insemination leading to conception, SPC is expected to increase, on average, by 0.72 inseminations (95% CI: 0.48, 0.95) compared with cows with no mastitis in the same time period. The estimated effect sizes for FSP/AI suggest a risk ratio of conceiving at first insemination of 0.90 (95% CI: 0.82, 0.99) for cows with mastitis diagnosed pre-first insemination with respect to cows with no mastitis in the same time period, and a risk ratio of 0.79 (95% CI: 0.72, 0.86) for cows diagnosed with mastitis either pre- or post-first insemination with respect to cows with no mastitis in the same time period. Publication bias was identified in 4 of the meta-analysis models (TFS, DO, SPC, and FSCR), but no influential trials were identified in any models; the reliability of the meta-analysis results should be interpreted carefully keeping these limitations in mind. Further meta-regression analysis would be valuable as additional studies are published that report other potential sources of heterogeneity.

Effect of repeated intravenous lipopolysaccharide infusions on systemic inflammatory response and endometrium gene expression in Holstein heifers

This study aimed to evaluate the effect of repeated intravenous lipopolysaccharide (LPS) infusions in nonlactating heifers on (1) the systemic proinflammatory state as measured by biomarkers in blood and plasma, and (2) endometrial gene expression of candidate transcripts on d 15 of gestation. Our hypothesis was that target transcripts related to a major functional group would be negatively modified in the preimplantation endometrium by the LPS treatments. In the first experiment (n = 13), a systemic proinflammatory state [defined as increased plasma concentrations of tumor necrosis factor (TNF)-α and haptoglobin for 2 wk] was established using 2 different sequential LPS infusion protocols. In the second experiment, heifers (n = 22; 11 mo of age) had their time of ovulation synchronized by a modified Ovsynch protocol and were enrolled in 1 of 2 treatments: control (CON; n = 11), which received sterile saline solution i.v., and LPS treatment (LPS; n = 11), submitted to repeated i.v. LPS injections (0.10, 0.25, 0.50, 0.75, 1.00, and 1.25 µg/kg) starting 2 d after artificial insemination (AI; d 0) and then every other day until d 15 after AI. At each LPS injection, rectal temperatures were measured hourly for 6 h. Blood samples were collected from d -1 to d 13 for analyses of progesterone, TNF-α, and haptoglobin in plasma, along with white blood cell (WBC) count and differential analysis. On d 15, endometrium tissue biopsies were taken and kept at -80°C until quantitative real-time PCR analysis of 30 target transcripts related to the immune system, adhesion molecules, and endometrium receptivity. Data were checked for normality and analyzed by repeated-measures ANOVA using PROC UNIVARIATE and PROC MIXED of SAS (SAS Institute Inc., Cary, NC). After each LPS injection, temperature was greater in the first 4 h in the LPS group compared with CON. Both TNF-α and haptoglobin increased in the LPS treatment with a significant treatment by day interaction. Total leukocyte count did not differ between treatments, but the differential count increased for neutrophils, band cells, and monocytes, and decreased for lymphocytes and eosinophils in LPS compared with CON. Progesterone concentrations in plasma did not differ between treatments during the experimental period. Out of 30 target genes analyzed, 3 transcripts were differentially expressed: indoleamine 2,3-dioxygenase (IDO; fold-change = 0.48) and pentraxin-3 (PTX3; fold-change = 0.38) were downregulated, whereas myxovirus-resistance protein (MX1; fold-change = 2.85) was upregulated in the LPS group. Sequential LPS injections were able to induce a prolonged systemic proinflammatory state, but effects on gene expression were limited to transcripts associated with the immune system. These results suggest that a mechanism for subfertility is linked to a proinflammatory state in dairy heifers.

An Update on the Effect of Clinical Mastitis on the Welfare of Dairy Cows and Potential Therapies

Despite the widespread implementation of mastitis control programs, mastitis is the most common and one of the costliest diseases in the dairy industry, with broad-ranging impacts and consequences. Recent technological advances have allowed researchers to assess the effects of mastitis on animal behavior and welfare, and the efficacy of mastitis treatments. Several nonsteroidal anti-inflammatory drugs are available as supportive therapies for clinical mastitis. This article focuses on recent advances in the assessment, therapy, and effects of mastitis on cow behavior and welfare.

A 100-Year Review: Mastitis detection, management, and prevention

Mastitis is the most frequent disease of dairy cows and has well-recognized detrimental effects on animal wellbeing and dairy farm profitability. Since the beginning of modern dairy farming, producers have sought effective methods to minimize the occurrence of mastitis in their herds. The objective of this paper is to review and highlight important advances in detection, management, and prevention of mastitis that have occurred since the first volume of the Journal of Dairy Science was published in 1917. Initial research efforts were directed at understanding the nature of pathogenic bacteria that were responsible for most intramammary infections. For decades, researchers worked to identify effective strategies to control mastitis caused by Streptococcus agalactiae and Staphylococcus aureus. To develop successful control programs, mastitis workers first had to identify mechanisms of infection, define the clinical and subclinical states of the disease, discover appropriate screening tests, determine likely points of exposure, identify pathogen-specific characteristics, and develop effective procedures for machine milking. Pioneering researchers eventually recognized that mastitis control was based on preventing new infections from occurring in healthy cows and reducing the duration that cows remained infected. Development of a control program that incorporated post-milking teat dipping, hygienic milking procedures, and strategic use of antibiotic therapy at dry-off resulted in widespread control of contagious pathogens. As herd management changed, researchers were tasked with defining control of mastitis caused by opportunistic pathogens originating from environmental sources. As mastitis pathogens have evolved, researchers have sought to define antimicrobial usage that will maintain animal wellbeing while minimizing unnecessary usage. During the last century, tremendous significant advances in mastitis control have been made but changing herd structure and more rigorous processor standards ensure that mastitis will remain an important subject focus of future research.

Addition of meloxicam to the treatment of bovine clinical mastitis results in a net economic benefit to the dairy farmer

Recently, it has been shown that the addition of meloxicam to standard antimicrobial therapy for clinical mastitis (CM) improves the conception rate of dairy cows contracting CM in the first 120 d in milk. The objective of our study was to assess whether this improved reproduction through additional treatment with meloxicam would result in a positive net economic benefit for the farmer. We developed a stochastic bio-economic simulation model, in which a dairy cow with CM in the first 120 d in milk was simulated. Two scenarios were simulated in which CM cases were treated with meloxicam in conjunction with antimicrobial therapy or with antimicrobial therapy alone. The scenarios differed for conception rates (31% with meloxicam or 21% without meloxicam) and for the cost of CM treatment. Sensitivity analyses were undertaken for the biological and economic components of the model to assess the effects of a wide range of inputs on inferences about the cost effectiveness of meloxicam treatment. Model results showed an average net economic benefit of €42 per CM case per year in favor of the meloxicam scenario. Cows in the no-meloxicam treatment scenario had higher returns on milk production, lower costs upon calving, and reduced costs of treatment. However, these did not outweigh the savings associated with lower feed intake, reduced number of inseminations, and the reduced culling rate. The net economic benefit favoring meloxicam therapy was a consequence of the better reproductive performance in the meloxicam scenario in which cows had a shorter calving to conception interval (132 vs. 143 d), a shorter intercalving interval (405 vs. 416 d), and fewer inseminations per conception (2.9 vs. 3.7) compared with cows in the no-meloxicam treatment scenario. This resulted in a shorter lactation, hence a lower lactational milk production (8,441 vs. 8,517 kg per lactation) with lower feeding costs in the meloxicam group. A lower culling rate (12 vs. 25%) resulted in lower replacement costs in the meloxicam treatment scenario. All of the scenarios evaluated in the sensitivity analyses favored meloxicam treatment over no meloxicam. This study demonstrated that improvements in conception rate achieved by the use of meloxicam, as additional therapy for mild to moderate CM in the first 120 d in milk, have positive economic benefits. This inference remained true over a wide range of technical and economic inputs, demonstrating that use of meloxicam is likely to be cost effective across many production systems.

Somatic cell count and type of intramammary infection impacts fertility from in vitro produced embryo transfer

The objective of this study was to assess the impact of mastitis-causing bacteria and somatic cell count (SCC) on pregnancy per embryo transfer (P/ET) in Holstein-Gir crossbred (Girolando) lactating dairy cows. Cows (n = 1397) were subjected to a timed-embryo transfer protocol. Milk samples were collected two days before embryo transfer for SCC and bacteriological culture analyses. Pregnancy diagnosis was performed on days 31 and 66 after timed-embryo transfer. The animals were grouped according to the National Mastitis Council recommendations: Gram-positive environmental (EV+), Gram-negative environmental (EV-), Gram-positive contagious (C+), coagulase-negative staphylococci (CNS) and control (no bacterial growth). Additional analysis was made by categorizing bacteria based on degree of pathogenicity (Major or Minor). Bacterial growth reduced P/ET (P < .01) at both 31 and 66 days of gestation. The P/ET was lower (P < .05) at 31 days in EV- (30.1%) and EV+ (29.9%) groups and tended (P = .09) to be lower in the C+ group (36.6%) than the control group (44.0%). The P/ET from the Major group at 31 days of gestation was lower (P = .03) compared with the Minor and control groups (32.1 vs 41.1 vs 43.2%, respectively). Cows with SCC > 400,000 cells/mL had lower P/ET (P < .01) than animals with SCC < 200,000 cells/mL at both 31 (30.4% vs 40.8%) and 66 days (24.7% vs 32.2%) of gestation. Pregnancy loss was not different between bacterial isolates and SCC categories. Elevated SCC significantly reduced P/ET, whereas environmental agents and those with Major pathogenicity yielded the greatest reduction in P/ET.

Influence of clinical mastitis and its treatment outcome on reproductive performance in crossbred cows: A retrospective study

Aim:

Evaluation of the effect of clinical mastitis (CM) and its treatment outcome on the reproductive performance in crossbred cows retrospectively.

Materials and Methods:

Datasets of 835 lactating cows affected with CM during a period of 12 years (2001-2012) were considered for this study. Mastitis treatment related data and reproductive parameters such as days to first detected heat (DTFDH), days to first insemination (DTFI), days open (DO), and number of services per conception (SC) were collected from mastitis treatment and artificial insemination registers, respectively. Data were analyzed by ANOVA using SPSS 20 software. The means were compared with the Duncan’s multiple comparison post-hoc test.

Results:

CM affected cows had significantly (p<0.05) higher DTFDH, DTFI, DO and SC compared to clinically healthy cows. Cows diagnosed with a single episode of CM had significantly (p<0.05) delayed DTFDH while, DO and SC were significantly higher (p<0.05) in cows diagnosed by multiple episodes of CM. SC was significantly (p<0.05) higher in cows diagnosed with both relapse and recurrence. Severe CM affected cows had significantly (p<0.05) altered reproductive parameters. The reproductive parameters were altered to high extent when CM occurred during the breeding period.

Conclusion:

CM-affected cows had higher DTFDH, DTFI, DO and SC compared to clinically healthy cows. The negative effects of CM on reproduction parameters were higher when CM occurred during the breeding period.

Postpartum anoestrus in five seasonally-calving dairy farms in Victoria, Australia

OBJECTIVE

A cross-sectional study of seasonally-calving dairy cows in south-western Victoria to quantify the prevalence of anoestrus and to assess the effect of body condition score (BCS), days in milk (DIM) at mating start date (MSD) and age on the likelihood of being diagnosed as anoestrus.

METHODS

Age, DIM and BCS details were collected from 1795 cycling and 1399 cows diagnosed as anoestrus in five seasonally-calving dairy herds in Victoria. Multivariable logistic regression was used to quantify the association between BCS, DIM and age and the probability of being diagnosed as anoestrus.

RESULTS

The apparent prevalence of anoestrus in cows that took part in the study was 44% (95% confidence interval (CI) 42-46%). The risk of anoestrus increased with decreases in DIM and BCS. There was a significant interaction between BCS and DIM. For cows >90 DIM at MSD (the reference category) the odds of anoestrus in cows with BCS <4.00 was 8.05-fold (95% CI 3.2-20.2) that of cows of BCS ≥4.50. The risk of anoestrus decreased with increases in cow age. Cows aged 2 and 3-5 years had 2.4-fold (95% CI 1.79-3.22) and 1.4 (95% CI 1.11-1.77) odds of anoestrus, respectively, compared with cows aged ≥6 years.

CONCLUSION

Reproductive management to maximise the number of days calved at MSD and nutritional management to ensure cows are in BCS >4.5 at mating will reduce the prevalence of anoestrus in Victorian dairy herds.

Effect of mastitis on luteal function and pregnancy rates in buffaloes

The aim of this study was to investigate the effects of mastitis on CL development and function and pregnancy rate in buffaloes. Sixty-six buffaloes (Bubalus bubalus) reared in a commercial farm at El-Beheira governorate, north of Egypt were used in this study. According to the visual observation of milk, physical examination of the udder and actual somatic cell count in milk, buffalo cows were divided into three groups: without mastitis (W), n = 23; subclinical mastitis (SC), n = 18; and clinical mastitis (C), n = 25. All buffalo cows were synchronized by double dose of PGF2α (11-day interval) and inseminated by frozen-thawed semen of fertile bull. Mean CL diameter was ultrasonically examined on Days 5, 9, 12, 16, 21, and 25 after artificial insemination (AI). Blood samples were taken on the days of ultrasonography for progesterone (P4) assay. Results indicated that pregnancy rates were lower (P < 0.05) in C (28.00%) and SC (55.56%) compared with W (69.57%) on Day 25 after first AI. Pregnancy rates reduced to 60.87%, 44.45%, and 16.00% in W, SC, and C, respectively, at Day 45 after insemination. Thus, the embryonic loss was 8.7%, 11.11%, and 12.00 % in W, SC, and C cows, respectively. Pregnancy rates decreased between 44.32% and 50.51% when mastitis occurred during Day -15 before to Day +30 after AI, compared with 59.22% in the uninfected cows. The diameter of CL was greater (P < 0.05) in W than SC and C cows starting at Day 9 postbreeding onward. Likewise, P4 concentrations on Days 9 through 25 after AI were greater (P < 0.05) in W cows as compared to SC and C cows. Positive correlations (P < 0.01) were found on Days 5, 9, 12, 16, 21, and 25 after AI between CL diameter and P4 concentrations. Similar trend was found among CL diameter, P4 concentrations, and pregnancy rate. Accordingly, incidence of mastitis revealed suppression to both CL diameter and function leading to significant reduction in pregnancy outcome of buffalo cows.

Factors in Dry Period Associated with Intramammary Infection and Subsequent Clinical Mastitis in Early Postpartum Cows

The objective of this study was to determine cow characteristics and farm management factors during the dry period associated with early postparturient intramammary infection (IMI) and subsequent clinical mastitis (CM). Data were collected three times: before drying off (P1), during the dry period (P2), and 5 to 14 days after calving (P3), using questionnaires and farm investigation. Milk samples were aseptically collected for bacterial identification at P1 and P3. Factors associated with IMI and CM were analyzed using multiple logistic regression models. The final model showed that IMI in early postpartum was significantly associated with full insertion of dry cow antibiotic, dry cows in barns with a combination of tie and free stalls, body condition score (BCS) in dry period and after calving, and milk yield before drying off. For IMI cows, factors significantly associated with clinical expression of mastitis were having daily barn cleaning, teat disinfected with alcohol before administration of dry cow therapy, BCS before drying off, milk yield before drying off, and days in milk at drying off. In conclusion, both cow and farm management factors are associated with the IMI rate and subsequent expression of clinical signs of mastitis in early postpartum cows.

Lipopolysaccharide enhances apoptosis of corpus luteum in isolated perfused bovine ovaries in vitro

Lipopolysaccharide (LPS), the endotoxin of Gram-negative bacteria, has detrimental effects on the structure and function of bovine corpus luteum (CL)in vivo. The objective was to investigate whether these effects were mediated directly by LPS orviaLPS-induced release of PGF2α. Bovine ovaries with a mid-cycle CL were collected immediately after slaughter and isolated perfused for 240 min. After 60 min of equilibration, LPS (0.5 μg/ml) was added to the medium of five ovaries, whereas an additional six ovaries were not treated with LPS (control). After 210 min of perfusion, all ovaries were treated with 500 iu of hCG. In the effluent perfusate, concentrations of progesterone (P4) and PGF2αwere measured every 10 and 30 min, respectively. Punch biopsies of the CL were collected every 60 min and used for RT-qPCR to evaluate mRNA expression of receptors for LPS (TLR2,-4) and LH (LHCGR); the cytokineTNFA; steroidogenic (STAR,HSD3B), angiogenic (VEGFA121,FGF2), and vasoactive (EDN1) factors; and factors of prostaglandin synthesis (PGES,PGFS,PTGFR) and apoptosis (CASP3,-8,-9). Treatment with LPS abolished the hCG-induced increase in P4(P≤0.05); however, there was a tendency (P=0.10) for increased release of PGF2αat 70 min after LPS challenge. Furthermore, mRNA abundance ofTLR2,TNFA,CASP3,CASP8,PGES,PGFS, andVEGFA121increased (P≤0.05) after LPS treatment, whereas all other factors remained unchanged (P>0.05). In conclusion, reduced P4responsiveness to hCG in LPS-treated ovariesin vitrowas not due to reduced steroidogenesis, but was attributed to enhanced apoptosis. However, an impact of luteal PGF2αcould not be excluded.

Subclinical mastitis disrupts oocyte cytoplasmic maturation in association with reduced developmental competence and impaired gene expression in preimplantation bovine embryos

Subclinical chronic mastitis was induced to examine the effects on oocyte developmental competence. Uninfected Holstein cows were intramammary administrated with serial (every 48h for 20 days) low doses of toxin of Staphylococcus aureus origin (Gram-positive; G+), endotoxin of Escherichia coli origin (Gram-negative; G-) or sterile saline (control). Follicular fluid of toxin- and saline-treated cows was aspirated from preovulatory follicles and used as maturation medium. Oocytes harvested from ovaries collected at the abattoir were matured and then fertilised and cultured for 8 days. The percentage of oocytes undergoing nuclear maturation, determined by meiotic nuclear stages, did not differ between groups. Cytoplasmic maturation, determined by cortical granule distribution, was affected by both toxins (PPPPTGS2) mRNA increased, whereas that of growth differentiation factor 9 (GDF9) decreased in matured oocytes. In addition, PTGS2 expression increased and POU class 5 homeobox 1 (POU5F1) expression decreased in 4-cell embryos developed from both G+ and G- oocytes. Thus, regardless of toxin type, subclinical mastitis disrupts oocyte cytoplasmic maturation and alters gene expression in association with reduced developmental competence.

Metabolic endotoxaemia--a potential novel link between ovarian inflammation and impaired progesterone production

INTRODUCTION

Medical conditions such as obesity and inflammatory bowel disease are associated with impaired luteal function, menstrual disturbance and infertility. It is proposed that the disturbance in gut wall integrity ("leaky gut") seen in these conditions may result in the passage of bacterial endotoxin (LPS) from the colonic lumen into the circulation that may initiate inflammation in the ovary and subsequently impair hormone production.

METHODS

Quantify the association between systemic levels of LBP, a marker of endotoxin exposure, and levels of inflammation in the ovary (follicular fluid IL-6), plus steroid hormone production in 45 women undergoing IVF treatment.

RESULTS

Endotoxaemia (LBP) were positively correlated with plasma CRP and inflammation within the ovary (follicular fluid IL-6). Furthermore, endotoxaemia was negatively correlated with progesterone production.

CONCLUSION

The observed correlations, together with previously published animal studies linking endotoxin exposure to impaired luteal function, suggest that the translocation of bacterial endotoxin from the gut lumen into the circulation has the potential to interfere with progesterone production and result in luteal deficiency.

Effects of physiological and/or disease status on the response of postpartum dairy cows to synchronization of estrus using an intravaginal progesterone device

Progesterone treatments are used to increase submission rates in postpartum dairy cows; however, in many cases the protocol is used as a blanket therapy for all cows without regard for physiological or disease state. The objective of this study was to identify the physiological or disease classes of cows that respond well (or not) to synchronization of estrus via progesterone. Dairy cows (n = 402) were monitored peri and postpartum to establish their physiological or disease status. Animals were classified as having negative energy balance, clinical lameness, uterine infection (UI), anovulatory anestrus, high somatic cell counts, and healthy (H). Blood samples were collected at five different time points and analyzed for metabolites. All animals received an 8-day controlled internal drug release protocol, which included GnRH at insertion and PGF2α the day before removal. Response to the protocol was determined by visual observation of estrus synchronization. Conception rate was determined by ultrasonography between Days 32 and 35 after artificial insemination. Animals without UI were 1.9 times more likely to respond and two times more likely to be confirmed pregnant than those with UI. There was no relationship between negative energy balance and clinical lameness in the visual estrous response, but both conditions were associated with reduced conception rates. Dairy cows in anovulatory anestrus responded successfully to the protocol in both estrous response and conception rates. High glutathione peroxidase concentrations had a positive effect on conception rates, whereas high non-esterified fatty acids and beta-hydroxybutyrate had a negative effect on the estrous response. In conclusion, disease and physiological states of dairy cows determined the response to progesterone-based synchronization. The more disease or physiological problems the cows had, the lower the estrous response and conception rates; cows with these problems were not ideal candidates for synchronization. Both anestrus and healthy dairy cows were good responders to progesterone-based synchronization.

Treatments of clinical mastitis occurring in cows on 51 large dairy herds in Wisconsin

Antimicrobials are frequently used for treatment of bovine mastitis and few studies have examined modern treatment strategies on large US dairy farms. The objective of this study was to describe treatment practices for clinical mastitis occurring in cows on large dairy herds in Wisconsin. Treatments performed on 747 cows experiencing cases of mild, moderate, or severe symptoms of clinical mastitis were recorded on 51 Wisconsin dairy farms. Duplicate milk samples were collected from the affected quarter for microbiological analysis at the onset of clinical mastitis and 14 to 21 d after treatment ended. Cows were treated according to individual farm protocol. Drugs and doses used for treatments were recorded for each case. Among all herds, 5 intramammary (IMM) antimicrobials (amoxicillin, hetacillin, pirlimycin, ceftiofur, and cephapirin) were used to treat cows for clinical mastitis. Of 712 cows with complete treatment data, 71.6% were treated with IMM ceftiofur either solely or combined with other antimicrobials (administered either IMM or systemically). Of cows experiencing severe symptoms of clinical mastitis, 43.8% received IMM treatment concurrent with systemic antimicrobials. Of all cows treated, 23.1% received an additional secondary treatment (either IMM, systemic, or both) because of perceived lack of response to the initial treatment. The majority of IMM treatments were administered to cows with a microbiological diagnosis of no growth (34.9%) or Escherichia coli (27.2%). Half of the cows experiencing cases caused by E. coli were treated using systemic antimicrobials in contrast to only 6.8% of cows experiencing cases caused by coagulase-negative staphylococci. In conflict with FDA regulations, which do not allow extra-label treatments using sulfonamides, a total of 22 cows from 8 farms were treated with systemic sulfadimethoxine either solely or in combination with oxytetracycline. Antimicrobial drugs were used on all herds and many cows received extra-label treatments. Great opportunity exists to improve mastitis therapy on large dairy herds, but use of more diagnostic methodologies is necessary to guide treatments. Farmers and veterinarians should work together to create protocols based on the herd needs considering reduced inappropriate and excessive use of antimicrobials.

Qualidade do leite: utopia sem um programa sério de monitoramento da ocorrência de mastite bovina

As mastites continuam sendo um dos principais problemas a onerar a pecuária leiteira, além dos aspectos de saúde pública, considerando-se a veiculação de patógenos causadores de doença em humanos. Sua múltipla etiologia, com o envolvimento de inúmeros patógenos, requer um programa de controle rigoroso para o seu monitoramento e controle de qualidade do leite, pautado em ações diagnósticas e de vigilância epidemiológica com relação a parâmetros que indiretamente associam-se à ocorrência de mastites nos rebanhos, como California Mastitis Test (CMT) e Contagem de Células Somáticas (CCS/mL de leite), de amostras de leite individuais composta de cada vaca, bem como do tanque de expansão, o que permite ainda o monitoramento da Contagem Bacteriana Total (CBT), que tende a se relacionar com a ocorrência de mastites, principalmente subclínicas. Destacam-se ainda aspectos de exame microbiológico do leite e da importância da ordenha como ponto crucial nas mastites, enfatizando aspectos relevantes do processo de ordenha com fatores de risco para a ocorrência das mastites. Baseando-se nestes aspectos, apresenta-se esta revisão, acreditando-se na possibilidade de obtenção de produtos lácteos de melhor qualidade, com o comprometimento de todos os envolvidos na cadeia produtiva do leite, conscientes de que a qualidade do leite depende de todos, valendo-se também os consumidores, que são os elementos finais da cadeia produtiva do leite.

Events occurring during the previous lactation, the dry period, and peripartum as risk factors for early lactation mastitis in cows receiving 2 different intramammary dry cow therapies

The objective of this study was to investigate the association between mastitis events occurring during the previous lactation, the dry period, and the peripartum period on the incidence of early lactation mastitis in cows receiving ceftiofur hydrochloride or penicillin dihydrostreptomycin as intramammary dry cow antibiotic therapy. Cows (n=402) from 2 large dairy farms in Central Florida were enrolled in the study at the time of dry-off processing and were randomly assigned to 1 of 2 dry cow therapies: ceftiofur hydrochloride or penicillin dihydrostreptomycin. Composite milk samples were collected at dry-off and after calving for bacteriological examination and somatic cell count. Peripartal health disorders were monitored during the first 30 d of lactation and included calving difficulty, metritis, ketosis, and left displaced abomasum. Milk production and individual somatic cell scores (SCS) were recorded monthly by the Dairy Herd Improvement Association. The main outcome variables were the risk of clinical mastitis during the first 30 and 60 d of lactation, and the risk of subclinical mastitis at the first 2 monthly Dairy Herd Improvement Association tests after calving (up to 70 d in milk). Additionally, the SCS and the presence of mastitis pathogens in milk at dry-off and at calving were analyzed. Explanatory variables consisted of events occurring during the previous lactation, at dry-off and during the dry period, at calving, and within the first 30 d after calving. Multiple events occurring during the previous lactation had a significant effect on the incidence of mastitis in the subsequent lactation. These events included low milk yield, intermediate lactation length, clinical mastitis, and lactation SCS average. Similarly, intramammary infections with environmental bacteria at dry-off increased the chances of clinical mastitis the first month after calving. Dry-off therapy had a significant effect on mastitis incidence; cows treated with ceftiofur hydrochloride had lower odds of having clinical and subclinical mastitis in the subsequent early lactation compared with cows treated with penicillin dihydrostreptomycin.

Chronic mastitis is associated with altered ovarian follicle development in dairy cattle

Connection between mastitis and fertility is multifaceted; therefore, several aspects need more elucidation. In particular, the aim was to investigate if naturally occurring chronic mastitis has an effect on ovarian function. At the time of slaughter, a milk sample and both ovaries were collected from 68 cows. The presence and intensity of chronic mastitis was diagnosed by the combined evaluation of bacteriological examination and somatic cell count of the milk of each individual quarter according to the measures of the National Mastitis Council. Animals were divided into 4 groups characterized by a low (n=15), mild (n=14), intense (n=19), or severe (n=16) degree of infection. A count of visible follicles on each ovary was followed by a quantitative analysis of microscopic traits on a selected group of animals (n=16). The latter included the classification and count of the entire preantral follicle population, and the morphometric analysis of the vascular bed extension and connective stroma in the cortical region. Finally, the expression of growth and differentiation factor-9 (GDF-9) was studied. The number of follicles with diameters ranging from 1 to 3 mm and 4 to 7 mm was not affected by the degree of infection. A significant effect of the degree of udder infection was observed on the number of follicles with a diameter larger than 8 mm. Furthermore, the intensity of mastitis had no effect on the number of primordial and primary follicles, but severely affected cows showed a lower number of secondary follicles (0.5±0.1 vs. 0.2±0.03). Quantitative analysis demonstrated a decrease in the density of blood vessels (6.30±1.08 vs. 4.68±0.28) expressed as ratio of vascular bed/total area) and a higher incidence of fibrous stroma (1.60±0.99 vs. 6.04±3.08 expressed as ratio of connective tissue/total area) in the cortical area of the most affected animals. Finally, the level of GDF-9 protein within the oocytes of different follicle size was lower in the animals with the severe form of chronic mastitis (1.34±0.05 vs. 0.78±0.21 expressed as arbitrary units). In conclusion, decreased fertility of cows with chronic mastitis takes place through an effect on the ovary altering the dynamics of folliculogenesis. Within the ovary, this implies a reduction of the vascular bed and an increase in the fibrotic tissue together with a direct effect on oocyte-specific factors as GDF-9, all of which are essential regulatory elements of folliculogenesis.

Relationship between milk somatic cell count and postpartum ovarian cyclicity and fertility in dairy cows

The main objective of the study was to describe the relationship of high somatic cell count (SCC) with the incidence of abnormal postpartum resumption of ovarian cyclicity and reproductive performance in dairy cows. The factors influencing SCC were also investigated. Four hundred and forty-seven cows from six dairy herds in Japan were monitored for SCC and postpartum resumption of ovarian cyclicity. Cows with high SCC (200,000 to 500,000) had a higher incidence of prolonged luteal phase (P < 0.01) than cows with an SCC of 50,000 to 100,000. The high SCC cows (> 500,000) also showed a higher incidence of delayed first ovulation post partum than cows with an SCC ≤500,000 (P < 0.05) during the first month post partum. Cows with an SCC of 200,000 to 500,000 showed lower conception and pregnancy rates, and more days from calving to conception than cows with an SCC of less than 200,000 (P < 0.05). Cows in parity 5 or more had a higher incidence of high SCC than cows in the first and second parities (P < 0.05). It is concluded that cows with a high SCC have a higher incidence of abnormal postpartum resumption of ovarian cyclicity, leading to reduced reproductive performance.