Buffaloes are recognized to have economic significance among livestock animals in terms of milk and meat yields as well as work purposes [1]. Mastitis is an infection of the mammary gland which is usually correlated with physical,...
moreBuffaloes are recognized to have economic significance among livestock animals in terms of milk and meat yields as well as work purposes [1]. Mastitis is an infection of the mammary gland which is usually correlated with physical, chemical and bacteriological changes in the milk and pathological changes in the glandular tissue of the udder [2]. Bovine mastitis is an important and a persistent infection in the buffalo population culminating in economic losses; drop in milk production, increases in the cost of treatment and culling process [3,4]. Buffaloes have some characteristics that may contribute to greater risk of mastitis. For example, the udder is more pendulous and teats are longer in comparison with cattle [5]. Somatic cells count (SCC) is an indicator of both resistance and susceptibility of animals to mastitis and can be used to monitor the level or occurrence of subclinical mastitis in herds or individual cows [6]. The SCC also has been used for buffaloes in mastitis diagnosis, and in fact, it seems probable that a SCC >200,000 cells/ml is an indicator of an udder infection [7,8]. Clinical mastitis is manifested by secretion of abnormal milk (i.e. watery milk, presence of flakes in milk, etc.) and/or inflammation (i.e. redness, swelling, hardness, etc.) of the mammary gland [9]. Subclinical mastitis (i.e. the asymptomatic inflammation of mammary tissue) is the most common form of mastitis representing 15 to 40 times higher incidence than clinical cases [10]. Subclinical mastitis is a bigger concern than clinical mastitis, because it remains undetected without the use of SCC, a measure not available to regular raisers of dairy animals [11].
Luteal size and progesterone (P4) secretion is an important indicator for functional corpus luteum (CL) in buffaloes [12,13]. The development and function of the CL differs between pregnant and non-pregnant buffalo cows [13]. The rate of CL growth between days 5 and 10 after artificial insemination (AI) could be a more accurate indicator of CL function, and a predictor of the likelihood of pregnancy in buffalo cows [14]. Also considered important, was the increase in CL area between day 15 and 20 post breeding in pregnant buffalo cows and the decrease in CL area in non-pregnant buffalo cows during same period [13]. The secretion of P4 during early luteal phase is essential for successful establishment of pregnancy [15]. Low plasma P4 concentration during early luteal phase was shown in non-pregnant buffalo cows compared to their pregnant counterparts [16]. Studies in dairy cattle have revealed associations between clinical mastitis and increased odds of abortion [17], abnormal length inter-service intervals [18], and failure to become pregnant after a service [19]. Other studies have identified associations between subclinical mastitis as measured by increased individual-cow SCC and increased odds of embryonic loss [20], abortion [21] and failure to become pregnant to first service [21]. Several potential mechanisms have been proposed to explain the effect of mastitis on reproductive performance. These are comprehensively reviewed by Hansen et al. [22], but broadly encompass detrimental impact of inflammatory mediators on ovarian follicular function [23], intrauterine embryonic survival [24], decreased luteal phase length [18], and the balance of luteolytic versus luteotrophic prostaglandins post-conception [25,26]. Besides, possible reason that mastitis has an inhibition effect on gonadotropin secretion leading to reduced gonadotropin support for ovulation, oocyte maturation, folliculogenesis and luteal function [22]. Mastitis is associated with increased secretion of cytokines that in turn can inhibits secretion of luteinizing hormone (LH), and reduces circulating concentrations of P4 [22]. However, virtually all of the published information about the risk factors for mastitis refers to dairy breeds of cattle but little information are available for buffaloes. Though a high probability exists that these identified risk factors may also be observed among these species. Therefore, the objectives of this study were to evaluate effects of mastitis on development and functions of the CL and consequently its effect on pregnancy rates in buffaloes. It was hypothesized that both clinical and subclinical mastitis might be associated with a reduction in CL functionality leading to pregnancy reduction in buffaloes.