The Role of Innate Immune Response and Microbiome in Resilience of Dairy Cattle to Disease: The Mastitis Model

Abstract

Animal health is affected by many factors such as metabolic stress, the immune system, and epidemiological features that interconnect. The immune system has evolved along with the phylogenetic evolution as a highly refined sensing and response system, poised to react against diverse infectious and non-infectious stressors for better survival and adaptation. It is now known that high genetic merit for milk yield is correlated with a defective control of the inflammatory response, underlying the occurrence of several production diseases. This is evident in the mastitis model where high-yielding dairy cows show high disease prevalence of the mammary gland with reduced effectiveness of the innate immune system and poor control over the inflammatory response to microbial agents. There is growing evidence of epigenetic effects on innate immunity genes underlying the response to common microbial agents. The aforementioned agents, along with other non-infectious stressors, can give rise to abnormal activation of the innate immune system, underlying serious disease conditions, and affecting milk yield. Furthermore, the microbiome also plays a role in shaping immune functions and disease resistance as a whole. Accordingly, proper modulation of the microbiome can be pivotal to successful disease control strategies. These strategies can benefit from a fundamental re-appraisal of native cattle breeds as models of disease resistance based on successful coping of both infectious and non-infectious stressors.

Maintaining Optimal Mammary Gland Health and Prevention of Mastitis

“…Immunocompetence can vary during lactation, showing depression in the peripartum period due to the hormonal and metabolic stress of calving and milk production. Decreased immunity after calving with the negligence in an application of milking hygiene program, housing hygiene, nutrition and breeding work increases transmission of pathogenic microorganisms and the contamination of the mammary quarters ( 39 ). In most cases, mastitis-causing microorganisms enter the MG tissue and milk through the teat duct, from where they are transmitted and spread to remaining structures of the glandular tissue [( 21 ), Figure 2 ].…”

“…Bacteriocins produced by certain non-aureus Staphylococci and Corynebacterium species colonizing the teat apices and teat canals may inhibit growth of major mastitis pathogens. According to Bronzo et al ( 39 ) commensal microbiota of MG can change immune responses through direct and indirect mechanisms, such as through bacterial secretion of antimicrobial compounds or through influencing the expression of genes hosts' immune responses.…”

The Autumn Low Milk Yield Syndrome in High Genetic Merit Dairy Cattle: The Possible Role of a Dysregulated Innate Immune Response

“…It has been observed, for example, that BHB has a harmful action on the antimicrobial mechanisms of leukocytes [ 25 , 26 ], induces oxidative stress, activates the cascade of proinflammatory signals with consequent damage to hepatocytes. Interestingly, NEB does not cause the same harmful effects in more advanced lactation stages, which point at complementation of diverse stressors in the peripartum period [ 1 ].…”

“…Dairy farming activities are presently based on few cosmopolitan cattle breeds [ 1 ] with a high genetic improvement for milk yield. In the presence of large increases in milk yield and substantial improvements of milk production hygiene over some decades [ 2 , 3 ], the health and welfare status of dairy cows still raises serious concerns because of low fertility and life expectancy [ 4 ].…”

“…As for high-yielding dairy cattle, disequilibrium stems from the imbalance between energy needed for lactation and energy provided through dry matter intake, which causes a substantial and prolonged Negative Energy Balance (NEB) [ 10 ]. As explained in a recent review paper [ 1 ], the innate immune system is pivotal to sensing metabolic stress. Accordingly, it can sense changes of cellular energy status (Adenosine triphosphate, ATP/Adenosine monophosphate, AMP ratio), shortage of amino acids, reduced oxygen tension, oxidative stress, as well as high concentrations of metabolites like non-esterified fatty acids (NEFA).…”