Ovarian follicular cysts and persistent follicles are follicular pathologies involved in reduced fertility of dairy cows. Two separate experiments were performed on high-yielding Holstein cows to characterize ovarian cyclicity and evaluate the developmental dynamics of follicle pathologies postpartum. In experiment 1, 58 cows were monitored by ultrasonography twice weekly from d 18±1 to 69±2 postpartum. First ovulation occurred 38±3, 27±2, 20±1, and 25±3 d postpartum in cows with 1 cycle (n=11), 2 cycles (n=21), 3 cycles (n=13), and 4 cycles (n=7), respectively. Follicular pathologies were developed in cows that were either acyclic (n=6) or had 1 or 2 cycles, but not in cows with more than 2 cycles. In experiment 2, 47 cows were monitored twice weekly from 10 d postpartum to second ovulation. Follicles ≥17 mm in diameter in 2 consecutive scans were aspirated, and concentrations of various hormones were measured. Cows were defined as cyclic (n=30; 64%) or with the potential to develop follicular pathology (n=17; 36%). Aspirated follicles (n=27) were classified into 3 main groups based on follicular growth rate, follicular diameter, and ovarian activity before and after follicular aspiration. Dominant follicles (n=4) were defined as large follicles (20 mm in diameter) with growth rate ≤1 mm/d and normal ovarian activity. Persistent follicles (n=6) had the same growth rate and diameter as the dominant follicles, but persisted at the same diameter for ≥10 d. Ovarian cysts (n=17) were defined as the largest follicular structures (19 to 32 mm in diameter), with abnormal growth rate (>1 mm/d) and abnormal ovarian activity. Single or turnover cysts did not differ in their growth parameters and were therefore combined and further classified according to follicular-fluid hormone concentrations. Estradiol-dominant cysts (n=7) were characterized by normal estradiol (284 to 659 ng/mL) and progesterone (20 to 113 ng/mL) concentrations, similar to those of the dominant follicle (554 to 993 ng/mL and 44 to 106 ng/mL, respectively). Progesterone-dominant cysts (n=5) were characterized by low estradiol (0.06 to 330 ng/mL) and high progesterone (586 to 3,288 ng/mL) concentrations. Low-steroidogenic active cysts (n=5) were characterized by low concentrations of both estradiol (23 to 61 ng/mL) and progesterone (17 to 205 ng/mL). Characterization of spontaneously forming cysts might enable definition of the formation of ovarian follicular pathologies in postpartum cows.

Abstract. Decreased conception rate of dairy cows in the summer is mainly associated with the deleterious effects of environmental thermal stress on the female reproductive tract. Here, we suggest that decreased reproductive performance might be partially due to inferior-quality semen. Semen from five representative bulls was collected in summer (August to September) and winter (December to January) and evaluated with a computerized sperm-quality analyzer for bulls (SQA-Vb). No seasonal effect was found in fresh ejaculate, but sperm examined post-thawing showed lower velocity, motility and progressive motility (P<0.04) in summer vs. winter samples. Element concentrations in the seminal plasma, determined by inductively coupled plasma-atomic emission spectrometry, differed between seasons, with higher (P<0.01) concentration values of K, Mg, Na and S elements in winter vs. summer samples. Therefore, season-induced alterations in seminal plasma element concentration should be taken into account when using an extender for cryopreservation. Acrosome integrity was assessed by a triple-fluorescence test using Hoechst 33342, fluorescein isothiocyanate-conjugated Pisum sativum agglutinin (FITC-PSA) and propidium iodide. Acrosome reaction was examined by a one-step staining method using FITC-PSA. The proportion of sperm cells with a damaged acrosome post-thawing tended to be higher (P<0.07) in semen collected during the summer vs. winter. Such alterations suggest that seasonal reductions in sperm function might also be involved in the decreased conception rate of dairy cows in summer. Decreased fertility of dairy cows during the summer is mainly associated with the deleterious effects of environmental thermal stress on the female reproductive tract. However, the effects of heat stress on semen quality may also contribute to the phenomenon [1, 2].Mature mammalian spermatozoa are quiescent in the male reproductive tract. Upon ejaculation, they undergo capacitation, develop hyperactive motility and acquire acrosomal ability to react [3]. These events involve sperm membrane hyperpolarization, activation of plasma-membrane ion channels and changes in intracellular Ca 2+ concentration, [Ca 2+ ] i [4,5]. Thus, season-induced alterations in one of these events might compromise spermatozoon fertilization competence.In bovines, the sperm flagellum contains cyclic nucleotidegated (CNG) channels-nonselective cation channels that regulate Na + , Mg 2+ and Ca 2+ influx under cGMP and cAMP control [4][5][6]. CNGA3 (formerly CNGα3) ion channels are expressed along the entire sperm flagellum, whereas CNGB1 (formerly CNGβ1) channels are localized to its principal part [4,7,8]. Activation of CNG channels leads to depolarization of the membrane voltage and a concomitant increase in cytosolic cation concentrations [9]. In addition, calcium flux through sperm inositol 1,4,5-trisphosphate (IP 3 ) receptors (IP 3 Rs) located in the sperm's head and connecting piece plays a pivotal role in acrosomal exocytosis, as binding of IP 3 to IP 3 Rs trig...

Mastitis, particularly in its subclinical form, is a widely spread disease that reduces the fertility of lactating cows. A major cause of poor conception risk has been associated with delayed ovulation of a large subgroup of subclinical mastitic cows. This study examined 2 approaches to improve fertility in this subgroup. Subclinical mastitic cows were defined by somatic cell count elevated above a threshold of 150,000 cells/mL of milk determined in all monthly test day samples collected before AI. Uninfected (control) cows were defined by somatic cell count below threshold. In experiment 1, we examined a hormonal approach aimed to correct the timing of ovulation in mastitic cows in which it would otherwise be delayed. The probability of conception of mastitic and uninfected groups following Ovsynch (OVS) and timed AI versus AI following detected estrus (E) was examined (n=1,553 AI) and analyzed by a multivariable, logistic model statement using the GLIMMIX procedure of SAS. The OVS protocol significantly elevated the probability of conception of mastitic cows to a level similar to that of their uninfected counterparts. Actual mean conception risks for uninfected-E, subclinical-E, uninfected-OVS, and subclinical-OVS groups were 41.8, 26.4, 39.3, and 40.5%, respectively. The OVS protocol did not improve probability of conception in cows diagnosed with uterine disease postpartum. In experiment 2, a management approach aimed to better synchronize timing of ovulation with timing of AI in subclinical mastitic cows was examined. A second AI was added 24h after the first (routine) AI, following detection of natural estrus. Probability of conception did not differ between subclinical mastitic cows inseminated once or twice. Lack of improvement in conception risk might be related to low preovulatory LH surge in mastitic cows, which is likely to induce not only delayed ovulation but also disruption of oocyte maturation. Thus the OVS protocol can improve fertility of subclinical mastitic cows, probably due to "corrected" timing of ovulation in cows in which it would otherwise be delayed.

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