Reproductive aspects of subacute ruminal acidosis (SARA)

In the present literature review, the key role of subacute ruminal acidosis (SARA) is discussed in the pathogenesis of reproductive disorders in dairy cows. Following a short introduction regarding the general properties and diagnostic possibilities of SARA, it is described that due to SARA-associated changes of ruminal microflora, lipopolysaccharide (LPS) type endotoxins are released from Gram negative bacteria, causing endotoxaemia after their absorption. Endotoxins and LPS-triggered pro-inflammatory cytokine production disrupt the neuroendocrine regulation of reproduction, causing delayed ovulation and thereby prolong post partum acyctia. Prevalence of claw diseases (such as laminitis) increases due to endotoxaemia, facilitating the development of reproductive disorders. Furthermore, hyper- and parakeratosis of the ruminal epithelium can also be observed in SARA, diminishing the integrity of ruminal wall as a protective barrier, thus leading to potential invasion of pathogens. This haematogen spreading of bacteria can induce inflammation in various organs, as well. Based on the mentioned literature data, the authors declare that special emphasis should be taken on the critical role of reproductive problems in SARA-associated economical losses.