Urbonas, Saulius

The period between calving and first artificial insemination (AI) is characterised by major metabolic adaptations that may influence subsequent reproductive performance in dairy cows. In this retrospective matched cohort study we examined the association between mineral-vitamin bolus supplementation during the early breeding period, reproductive performance, and blood biochemical parameters under commercial dairy farm conditions. Clinically healthy dairy cows were enrolled in matched pairs based on calving date and lactation number. Within each pair, one cow received the bolus and the other served as a control. Allocation was not randomised. A total of 88 cows were included in the final analysis (45 supplemented and 43 control cows). Cows received two boluses at 51.13 ± 3.15 days in milk (DIM) and two additional boluses 14 days later. Each dose of two boluses provided a declared daily delivery of 2.4 g magnesium, 130 mg zinc, 36 mg copper, 1.5 mg selenium, 132,000 IU vitamin A, 500 IU vitamin E and 300 mg β-carotene over a 10-day release period. Reproductive outcomes included conception at first AI, pregnancy by 150 and 300 days in milk (DIM), time to confirmed pregnancy, days to first oestrus, and days to first AI. Blood samples were collected at enrolment and 14 and 21 days later. After adjustment for baseline metabolic status, parity, and DIM at enrolment, bolus supplementation was associated with higher odds of conception at first AI (OR = 3.45; 95% CI: 1.07–11.11; p = 0.038) and, as an exploratory endpoint, pregnancy by 300 DIM (OR = 3.80; 95% CI: 1.19–12.19; p = 0.025). No differences were observed in pregnancy by 150 DIM or time to confirmed pregnancy. Supplementation was not associated with the resumption of oestrus overall. An earlier resumption in multiparous cows was an exploratory subgroup finding. Supplemented cows had higher serum magnesium concentrations and lower LDH activity than controls (supplementation-by-time interaction, p < 0.001 and p = 0.025, respectively). Bolus supplementation was therefore associated with higher odds of conception and pregnancy and with altered mineral status. The difference in cumulative pregnancy emerged only after 180 DIM, more than 100 days after supplementation ended.

High-yielding dairy cows experience substantial metabolic stress from early lactation, potentially impairing reproductive performance; however, lactation curve characteristics have not been comprehensively evaluated within a single analytical framework as predictors of conception outcomes at first artificial insemination (AI). This study analyzed 270 clinically healthy multiparous Holstein cows managed under a standardized reproductive program on a commercial Lithuanian farm. Peak milk yield, days to peak, and absolute milk yield decline from peak to artificial insemination were derived from DairyPlan C21 records, and pregnancy was diagnosed by transrectal ultrasonography. Associations with conception outcomes at first AI were assessed using multivariable logistic regression and chi-square tests. After adjustment for milk yield at AI, days to peak, and lactation number, peak milk yield was negatively associated in Model A (milk at AI model) with conception outcomes at first AI (OR = 0.88, 95% CI 0.82–0.95, P = 0.001), although this association was not evident in unadjusted analysis (OR = 0.95, P = 0.342). Each additional day to peak was associated with approximately 2.2% lower odds of conception (OR = 0.978, 95% CI 0.961–0.994, P < 0.01). Post-peak decline had the strongest effect, with each 1-kg increase associated with a 12.6% decrease in the odds of conception (OR = 0.87, 95% CI 0.81–0.94, P < 0.001) and conception rates decreasing across decline categories. These findings suggest that lactation curve traits, particularly post-peak decline (ΔMilk), represent the strongest variable associated with conception outcomes at first AI in high-yielding cows and may support exploratory decision-making regarding optimal artificial insemination timing using routinely collected milk data, pending validation in independent multi-herd studies.

Negative energy balance (NEB) provokes oxidative, metabolic, and functional stress in postpartum dairy cows, impairing productive and reproductive functions. To enhance metabolic and antioxidant stability various nutritional supplements are used in the diet of dairy cows. Blood and milk parameters can be used indirectly to evaluate the ability of cows to cope with oxidative and metabolic stress. This study aimed to assess the effect of antioxidant feed supplementation on milk and blood parameters, reproductive disorders, and mastitis as indirect markers of postpartum stress on dairy cows. Clinically healthy Holstein cows instantly after calving, 2–4 lactation, and total milk production of 8,755 kg were selected (n=30). To reduce baseline variability, cows were equally assigned to groups of experimental and control. Both groups were managed simultaneously under identical conditions. Only the experimental group received 200 g/day of a feed supplementation containing plant polyphenol (Ceratonia siliqua L.) until 100 days in milk (DIM). Blood samples were collected at 5, 15, and 100 DIM for aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT) analysis. Milk samples were collected at 30, 60, and 90 DIM for urea, lactose, and somatic cell count (SCC), and milk yield data obtained from the DeLaval DelPro5. Occurrence of reproductive disorders (metritis and endometritis combined), and mastitis were recorded. Data was analyzed using IBM SPSS Statistics 30.0 including ANOVA and chi-square tests with odds ratios calculated. Statistical significance was set at p < 0.05. The experimental group produced 17.5 % more milk than control 40.82 ± 1.55 vs 33.68 ± 1.55 kg/day with the greatest difference at 60 DIM 42.79 ± 1.84 vs 33.19 ± 1.84 kg/day, respectively (p < 0.01). SCC was 55.3 % lower in the experimental group compared with control 439.31 ± 118.52 vs 794.18 ± 118.52 ×10³ cells/cm³, respectively (p < 0.05). No significant supplementation effects were observed for blood AST, GGT, or milk urea, and lactose. The odds of reproductive disorders were 7.43 times higher in control (53.3 %) than in the experimental (13.3 %) group (p < 0.05) while mastitis prevalence was higher in control cows but did not have statistical significance. In conclusion, polyphenol supplementation improved milk yield, reduced somatic cell count and the incidence of reproductive disorders in postpartum dairy cows, but no changes in blood biochemical and milk parameters were observed. These findings suggest that antioxidative supplementation improved metabolic adaptation to lactation stress with variability in response likely related to individual adaptive capacity.

Retained placenta (RP) is a post-partum disorder in dairy cows that poses major challenges to herd management, animal welfare, and farm economics. Early identification of cows at risk can be done using body condition score (BCS). Recent data demonstrated that cows with lower BCS at calving had a significantly higher risk of developing RP, however, this assessment relied on visual scoring which is time- and resourceconsuming. This highlights the need to integrate artificial intelligence (AI) – based precise monitoring methods, such as DeLaval automated BCS camera system, and to determine if it is a significant diagnostic tool before clinical signs occur. The objective of this study was to evaluate the effectiveness of automated and accurate BCS camera system as a predictive tool for RP disorders in dairy cows. This study was conducted on a commercial dairy farm involving 50 selected Holstein cows from 1st to 3rd lactation (herd average 2 lactations) and milk yield ranging from 23 to 37 L/d (herd average 30 L). Animals were divided into groups of control and RP affected cows. DeLaval automated 1–5 point scale BCS camera was used, which utilizes three-dimensional imaging supported by motion sensors and a distance meter, consisting of an infrared camera and a laser projector to create a 3D field around each animal. BCS data were taken 60 days before calving and up to 5 days after calving. RP diagnosed as presence of visible placental tissue protruding from the vulva more than 12–24 hours after parturition. The data received indicates that prior to calving, the average BCS of control cows was 3.40 ± 0.23, while cows affected with RP had a lower average of 3.25 ± 0.29 (p < 0.05). After parturition, the contrast increased: control cows averaged 3.35 ± 0.28, whereas affected cows’ BCS decreased to 3.10 ± 0.45 (p < 0.05). Furthermore, control cows showed only a slight decline between evaluations, while cows with RP experienced 3 times bigger reduction of BCS (p < 0.05). These findings indicate that cows with higher BCS before calving were less prone to experience RP. The analysis revealed that cows without RP consistently had higher BCS compared to affected ones before and after calving. Thus, continuous AI camera-based precise BCS monitoring can serve as a practical tool to identify cows at early risk and support timely preventive management.

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