G.M. Pighetti

Novel single nucleotide polymorphisms and haplotypes within the bovine CXCR2 gene

The objectives of this study were to identify single nucleotide polymorphisms (SNPs) and resulting haplotypes in the bovine CXCR2 gene. A 311-bp segment of the bovine CXCR2 gene was amplified and sequenced. Five SNPs at positions 612, 684, 777, 858, and 861 were expressed in both Holstein and Jersey dairy cattle. Four SNPs resulted in synonymous substitutions, while a non-synonymous switch at position 777 (G→C) resulted in a glutamine to histidine substitution at amino acid residue 245. Strong linkage disequilibrium was exhibited for both breeds among all five loci (P<0.001). Both allele and genotype frequencies differed significantly with respect to breed at four of the five loci (P<0.001). The five polymorphisms generated ten distinct haplotypes. Six haplotypes were common between the two breeds, while Holsteins and Jerseys each uniquely expressed two haplotypes. Of the six common haplotypes, two represented 83% of the Jersey population; whereas four of these haplotypes represented 95% of the Holstein population.

Differential calcium signaling in dairy cows with specific CXCR1 genotypes potentially related to interleukin-8 receptor functionality

Neutrophil migration and activation are critical components of innate immunity and are mediated by a variety of inflammatory mediators, which include interleukin-8 (IL-8) and epithelial-derived neutrophil activating peptide-78 (ENA-78). Limited knowledge on the expression of receptors for these inflammatory mediators (CXCR1 and CXCR2) in bovine, in addition to the association of a polymorphism (G→C) in position +777 of the CXCR1 gene with impaired neutrophil function, prompted evaluation of CXCR1 and CXCR2 mRNA and protein expression, ligand binding affinity, and intracellular receptor signaling in neutrophils from cows with different CXCR1 genotypes. Initial observations revealed that overall IL-8 receptor numbers appeared to be lower in cows with a CC genotype compared to cows with a GG genotype. However, in the presence of SB225002, a CXCR2 inhibitor, CXCR1 affinity was about fivefold lower in cows with a CC genotype and may have resulted in an underestimation of receptor numbers in cows with this genotype.In addition, intracellular calcium ([Ca++]i) release was lower in cows with a CC genotype when cells were stimulated with IL-8 but not ENA-78. Furthermore, when neutrophils were stimulated with an optimal dose of IL-8 in the presence of SB225002, [Ca++]i release was lower in cows with a CC genotype, suggesting differential CXCR1 signaling among genotypes. These findings offer knowledge of the role that each of these receptors plays in the inflammatory response in the bovine and provide insight into the potential mechanisms that may be affected in neutrophils of cows with different CXCR1 genotypes.

Gene Polymorphisms: The Keys for Marker Assisted Selection and Unraveling Core Regulatory Pathways for Mastitis Resistance

One of the most frequent mammary diseases impacting lactating animals is mastitis, an inflammation of the mammary gland most commonly caused by bacterial infection. The severity of mastitis is greatly influenced by the invading organism and the subsequent immune response which must recognize the foreign organism, recruit immune cells, eliminate the invading pathogen, and resolve the inflammatory response. The speed, strength, and duration of this response and subsequent disease susceptibility are critically tied to the genetic background of an animal. However, the genetic contribution has been difficult to identify due to the complex interactions that must occur for effective disease resistance. Recent studies have utilized polymorphisms to better define the genes and chromosomal regions that contribute to mastitis resistance. This review will examine these studies with primary emphasis in bovine systems, as the most work regarding mastitis has been conducted in this species.

Quantification of bovine oxylipids during intramammary Streptococcus uberis infection.

Streptococcus uberis mastitis results in severe mammary tissue damage in dairy cows due to uncontrolled inflammation. Oxylipids are potent lipid mediators that orchestrate pathogen-induced inflammatory responses, however, changes in oxylipid biosynthesis during S. uberis mastitis are unknown. Thus, the current objective was to determine how oxylipid concentrations change in milk and mammary tissues during different stages of S. uberis mastitis. Increased arachidonic acid and linoleic acid-derived oxylipids were significantly increased in S. uberis-infected bovine mammary tissue. Linoleic acid metabolites, hydroxyoctadecadienoic acid (HODE) and oxooctadecadienoic acid, predominated in tissue and milk. Furthermore, in vitro exposure of bovine mammary endothelial cells to 13-hydroperoxyoctadecadienoic acid, upstream metabolite of HODE, significantly increased cyclooxygenase-2 expression, but 13-HODE exposure had no effect. The findings in the current study indicate lipidomic profiling may explain some of the dynamics of inflammation during bacterial challenge, however continued research is necessary to determine sample compartments which best reflect disease pathogenesis.

Protective effect of anti-SUAM antibodies on Streptococcus uberis mastitis

In the present study, the effect of anti-recombinant Streptococcus uberis adhesion molecule (SUAM) antibodies against S. uberis intramammary infections (IMI) was evaluated using a passive protection model. Mammary quarters of healthy cows were infused with S. uberis UT888 opsonized with affinity purified anti-rSUAM antibodies or hyperimmune sera. Non-opsonized S. uberis UT888 were used as a control. Mammary quarters infused with opsonized S. uberis showed mild-to undetectable clinical symptoms of mastitis, lower milk bacterial counts, and less infected mammary quarters as compared to mammary quarters infused with non-opsonized S. uberis. These findings suggest that anti-rSUAM antibodies interfered with infection of mammary gland by S. uberis which might be through preventing adherence to and internalization into mammary gland cells, thus facilitating clearance of S. uberis, reducing colonization, and causing less IMI.

Mastitis Pathogens | Environmental Pathogens

Current mastitis control programs are based on milking time hygiene, antibiotic therapy during lactation and at drying off, and culling of chronically infected cows. Application of these measures has led to considerable progress in controlling contagious mastitis pathogens. However, these mastitis control procedures are less effective against environmental mastitis pathogens. Studies have shown that as the prevalence of contagious mastitis pathogens was reduced, the proportion of intramammary infections caused by environmental pathogens increased markedly. Therefore, it is not surprising that environmental mastitis has become a major problem in many well-managed dairy farms. In these herds, environmental mastitis pathogens account for a significant proportion of subclinical and clinical mastitis in both lactating and nonlactating cows. The most frequently isolated environmental pathogens are several species of streptococci collectively referred to as environmental streptococci, and Gram-negative bacteria. Among the environmental streptococci, Streptococcus uberis and Streptococcus dysgalactiae appear to be the most prevalent, infecting mammary glands as favorable conditions arise. The most common Gram-negative pathogens isolated are Escherichia, Klebsiella, and Enterobacter, which form a subgroup of Gram-negative organisms termed coliforms. The purpose of this article is to summarize what is known on the etiology, diagnosis, epidemiology, and pathogenesis of environmental mastitis pathogens.

Short communication: Evaluation of an automated method for assessing white blood cell concentrations in Holstein dairy cows

Assessing white blood cell (WBC) differentials is one way to assess cow health and well-being. The objective of this study was to determine the agreement between WBC populations identified by manual evaluation via microscopy and an automated approach. Data were collected from mid-to-late lactation dairy cows sampled at 6-h intervals starting at 2100 over a 48 period (n = 192). The agreement between the two methods was calculated using a regression model in SAS (v9.4, SAS Institute Inc., Cary, NC) to construct limits of agreement. Data were analyzed by comparing the mean response of the methods for each sample against the difference between the methods The maximum allowable difference (MAD) was set at ±10% for each response variable. Agreement between methods was evident for neutrophils and lymphocytes, but not for monocytes and eosinophils. Agreement for these factors was established from an insignificant P-value, a low R2 value, and concentration of the data within the MAD. This data indicates that the automated method is appropriate for analysis of neutrophil and lymphocyte concentrations. However, accuracy needs to be improved for analysis of monocytes and eosinophils if differentiation of all WBC populations is necessary.

Effects of 2-stage and total versus fenceline weaning on the physiology and performance of beef steers123

Forty-eight steer calves (initial BW = 314 ± 21 kg), housed on pasture with their dams, were used to document changes in growth performance and various physiological measures when fitted with (YD) or without (ND) an antisuckling device for 7 d and weaned (d 0) by fenceline (FS) or total separation (TS). All steers were weighed and bled on d − 7, − 4, 0, 3, 7, 14, and 35. On d 7 the FS group was moved to a pasture lot distant from their dams and adjoining the TS group. Weight gain was similar (P = 0.74) between ND and YD steers between d − 7 and 0. The YD-FS steers lost weight (P = 0.01) by d 3 compared with the YD-TS steers, and from d 14 to 35 the YD-TS steers were heavier (P = 0.02) than the YD-FS steers. Hematocrit (HCT) increased (P = 0.04) in YD but not ND steers by d − 4 and was similar between treatments thereafter. Before weaning, treatment had no effect on neutrophil-to-lymphocyte ratio, plasma cortisol, haptoglobin, ceruloplasmin, or serum interferon-γ (IFN-γ) concentrations. Plasma haptoglobin and ceruloplasmin increased (P < 0.01) in all steers from d − 7 to − 4. Upon weaning, d 3 ceruloplasmin was greater (P < 0.05) in FS vs. TS steers, d 7 plasma cortisol was greater (P < 0.05) in YD-FS vs. YD-TS steers, and d 14 IFN-γ was greater (P < 0.05) in TS vs. FS steers. Lymphocyte percentage tended (P < 0.10) to be lower for YD vs. ND steers on d 0 to 7 regardless of method of separation, resulting in an overall greater (P < 0.05) mean neutrophil-to-lymphocyte ratio for the YD steers. Use of a preweaning anti-suckling device marginally altered growth performance and physiology in beef steers postweaning.