This study aimed to investigate the effects of oxidative stress and antioxidant activity in plasma and uterine fluid during early postpartum on the reproductive performance of Japanese Black cows. A total of 17 Japanese Black cows were included in this study. Plasma and uterine fluid samples were collected at days 7 and 14 of the estrus cycle (n = 17), between 47–67 days postpartum, and diacron-reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) were measured. d-ROMs, BAP, and oxidation stress index (OSI: d-ROMs/BAP × 100) were compared between pregnant and nonpregnant cows at first postpartum artificial insemination (AI), cows pregnant less than 120 days postpartum (<120 days postpartum), and cows pregnant more than 120 days postpartum (≥120 days postpartum) regardless of AI number. The uterine fluid OSI on day 7 of the estrus cycle was significantly higher in cows pregnant ≥ 120 days postpartum (p < 0.05). d-ROMs, BAP, and OSI of uterine fluid during early postpartum were useful indicators for determining the subsequent reproductive performance of Japanese Black cows.

The objectives of this study were to assess the sequential dynamics of the endometrial polymorphonuclear cells (PMN) after calving by endometrial cytology, and clarify the factors that cause prolonged endometrial inflammation in lactating dairy cows. A total of 33 lactating Holstein dairy cows were used from −4 to 8 wk relative to calving (0 wk: the calving week). Endometrial samples were obtained sequentially from 2 to 8 wk. Body condition score and backfat thickness were obtained weekly from −4 to 8 wk. Blood samples collected from −4 to 8 wk were analyzed for indicators of energy status, hepatic function, systemic inflammation, and calcium. Blood amino acids were measured at 2 wk. Daily milk production was determined between 5 and 65 d postpartum. Based on the sequential cytological analysis, the endometrial inflammation threshold was set at ≥5.0% PMN, and the median wk of PMN% lower than 5.0% was 4.5 wk in this study; therefore, we classified the cows into the early group (cows with endometrial inflammation converged within 4 wk: n = 17) and the late group (cows with endometrial inflammation converged at or after 5 wk: n = 16). There were no differences in daily milk production, energy status, hepatic function, blood calcium concentration, and systemic inflammatory response. The late group had lower body condition scores and backfat thickness during the experimental period, and a higher blood concentration of 3-methyl histidine, indicating muscle breakdown, was observed in the late group at 2 wk. Our findings indicated that the lack of body fat reservation during the peripartum period and the increased muscle breakdown after calving were risk factors for prolonged endometrial inflammation.

The recurrence of reduced milk flow is a common sequela after placement of teat inserts in the streak canal as a treatment for teat injury. We evaluated the effects of three types of commercial teat inserts on wound healing. Thirty-two normal streak canals of eight cows were incised longitudinally using a teat knife. Then, a wax-bougie, silicone self-retaining cannula, and catgut teat dilator were placed in each cow for 7 days. No insert was placed on the remaining teat as a control. Histopathological examination revealed that granulation polyps with squamous metaplasia developed in the area around the rosette of Furstenberg in most teats in which silicone cannulas and catgut teat dilators were placed, whereas the controls and the teats with wax-bougies healed with less tissue reaction. This study suggests that the placement of irritating inserts, such as a silicone cannula and catgut teat dilator, interfere with wound healing.

Summary: We compared the fertility of lactating Holstein cows having only 1 large follicle (≥10 mm; 1F) or ≥2 large follicles (2F) and a corpus luteum after short-term ovulation synchronization and timed artificial insemination (AI). The ovulation induction agent, estradiol benzoate (EB) or gonadotropin-releasing hormone (GnRH), was injected after prostaglandin F_2α (PGF_2α) administration. In cows with 1F, which was presumed to be a first-wave dominant follicle, the fertility after AI was lower than in cows with 2F, which were presumed to be second-wave dominant follicles, when GnRH was administered. However, fertility after AI was similar in cows with 1F and 2F when administered EB.

The objectives of this study were (1) to investigate the distribution of large (≥10 mm) follicle numbers during the estrous cycle and (2) to compare the timing of the estrus expression period after the ovarian examination between cows with one large follicle (1F) and two or more large follicles (2F) with functional corpus luteum (CL) at the ovarian examination in lactating Holstein dairy cows. In experiment 1, we performed 393 ovarian examinations by ultrasonography, addressed the existence of CL (≥20 mm) and large follicle numbers, and classified cows into 1F (n = 229) and 2F (n = 164) groups. The 1F appearance rates were beyond 75% each day during 3 to 12 d after estrus. However, 2F appearance rates were beyond 75% each day during 15 to 24 d after estrus. In experiment 2, we performed 302 ovarian examinations by ultrasonography and classified cows into the 1F (n = 168) and 2F (n = 134) groups. Estrus detection was performed for 24 d after the ovarian examination in each cow. In the 2F group, 75% of estrus occurred within 9 d of the ovarian examination. However, 75% of estrus occurred 10 d after the ovarian examination in 1F. Days from the ovarian examination to estrus were significantly shorter in the 2F (6.0 d; median, 7.2 ± 4.0 d; mean ± SD) than in the 1F (13 d, 12.4 ± 4.3 d) group. In conclusion, focusing on ≥10 mm follicle numbers with CL could be useful for predicting the estrus expression period.