Effects of Induced Clinical Mastitis During Preovulation on Endocrine and Follicular Function

Abstract

The objective of the study was to determine if experimentally induced clinical mastitis before ovulation resulted in alterations of endocrine function, follicular growth, or ovulation. On d 8 (estrus = d 0), cows were challenged (TRT; n = 19) with Streptococcus uberis or were not challenged (control; n = 14). Forty-eight hours after induction of luteal regression on d 12, blood samples were collected to determine estradiol-17beta, LH pulse frequency, and occurrence of the LH surge. Ovaries were scanned to monitor follicular growth and ovulation. Cows with clinical mastitis (n = 12) had elevated rectal temperatures, somatic cell counts, and mammary scores. Estrus and ovulation occurred in 4 of 12 clinically infected cows and in all control cows. Cows that were challenged but did not develop clinical mastitis (n = 5) displayed estrus and ovulated. Due to differences in expression of estrus, cows were further subdivided for analyses into 4 groups: control, TRT-EST (infected cows that displayed estrus; n = 4), TRT-NOEST (infected cows that did not display estrus; n = 8), and NOMAS (cows that were inoculated but did not develop mastitis; n = 4). Ovulation rate was 100% for CON, NOMAS, and TRT-EST compared with 0% for TRT-NOEST cows. Size of the ovulatory follicle ("presumed" ovulatory follicle in TRT-NOEST cows) was similar for all groups. Frequency of LH pulses was decreased in TRT-NOEST compared with CON, TRT-EST, and NO-MAS. Estradiol-17beta increased over time in CON, NO-MAS, and TRT-EST cows, but did not increase in TRT-NOEST cows. Cows with clinical mastitis may exhibit estrus and ovulate normally or have disruptions in normal physiology including decreased LH pulsatility, absence of an LH surge and estrous behavior, suppressed estradiol-17beta, and failure to ovulate.

Influence of somatic cell count, body condition and lameness on follicular growth and ovulation in dairy cows

“…Per-rectum ultrasonographic measurements of both follicular growth and maximum diameter were similar to other studies in postpartum cows [23–25], and concurred with results after experimentally induced mastitis [26]. Nevertheless, the present study is the first to show that ovulation is detrimentally affected.…”

Effects of pathogen-specific clinical mastitis on probability of conception in Holstein dairy cows

“…This was in close agreement with a study by Wilson et al (2008). Similarly, Hockett et al (2005) found that cows experimentally infected with Strep. uberis were more likely to exhibit signs of impaired reproductive performance, including lack of Table 5.…”

“…When CM occurs before AI, the reproductive system may be too impaired to initiate a pregnancy, due to estrus cycle disruptions (Hockett et al, 2005;Williams et al, 2008;Herath et al, 2009). Alternatively, even if the embryo does successfully implant in the uterus, it may be lost before pregnancy is confirmed (Moore et al, 2005).…”

“…Although several studies have examined the effects of different CM pathogens on various aspects of reproduction in dairy cows (Moore et al, 1991;Hockett et al, 2005;Wilson et al, 2008), to our knowledge none have combined this information with timing of CM cases in specific intervals before or after AI.…”

Effect of mastitis during the first lactation on production and reproduction performance of Holstein cows

“…It was shown that clinical mastitis has multiple actions that hinder normal endocrine function and particularly affecting communication from the pituitary to the ovary (Hockett et al 2005). The onset of clinical mastitis was also important in terms of embryo survival Hertl et al 2010).…”