Analysis of some factors affecting fertility levels in a high-producing dairy herd in south-western Japan.

The present study aimed to know whether all cows have been showing declining fertility or only a proportion of cows are attributed to the declining fertility, and to describe factors affecting the level of fertility. A total of 131 cows calved from February 2005 to December 2007 in a dairy herd were examined. Fourteen cows were excluded from the study because of early culling. Of the remaining 117 cows, 47 (40%) conceived within 115 days postpartum after 1-3 artificial insemination (AI) (normal fertility cows), 42 (36%) conceived after 115 days postpartum following 1-3 AI or were culled after 1-2 (sub-fertility cows/culled), and 28 (24%) were inseminated more than three times without detectable genital tract abnormalities (repeat breeders). Calving to conception interval in the normal fertility group was 72 + 3 days, while in the sub-fertility/culled and repeat breeding groups the intervals were 170 + 8 and 259 + 16 days, respectively. Endometritis was the risk factor for sub-fertility/culled (odds ratio (OR) = 3.76). Prolonged luteal phase (OR = 4.08), delayed first ovulation (OR = 6.02), and delayed corpus luteum formation after AI (OR = 8.55) were the risk factors for repeat breeding. In conclusion, 60% cows showed reduced fertility in a herd, while the other 40% had normal fertility. Uterine infection and some ovarian disorders contributed to reduced fertility.

Effect of CIDR 12 to 19 days after AI on detection of returning estrus and conception rate in dairy cows.

Detection of returning estrus in dairy cows after AI and re-insemination without delay are important in shortening the calving to conception interval. The objectives of this study were to show the effectiveness of CIDR insertion 12 to 19 days after AI on returning estrus and shortening the calving to conception interval in dairy cows. Seventy-nine dairy cows from two commercial dairy farms were synchronized for first postpartum estrus using a CIDR-Heatsynch protocol, and 76 cows (96.2%) showed estrus signs within 2 days after EB injection and were inseminated. The cows were then divided randomly into two groups. Thirty-seven cows were treated with a CIDR from 12 to 19 days after AI (CIDR group), while the other 39 cows were not treated and served as a control group. Milk samples were collected twice weekly from one week before the commencement of the CIDR-Heatsynch protocol until 7 to 9 days after removal of device. Detection rates of returning estrus 20 to 25 days after AI (within 6 days after removal of the device) were 30.4% in the CIDR group and 47.6% in the control group. According to the progesterone profiles, almost half of the non-pregnant cows that did not show estrus 20 to 25 days after AI had high progesterone concentrations from days 20 to 25, 59.1% in the CIDR group and 50.0% in control group. The calving interval was not significantly different between the CIDR (162 +/- 50 days) and control groups (151 +/- 40 days). In conclusion, CIDR insertion 12 to 19 days after AI did not increase the detection rate of returning estrus. As a consequence, there was no effect of the CIDR treatment on the calving to conception interval.