In presented thesis the chosen parameters of reproduction {--} days to first service, days open, calving interval, insemination index - were evaluated in dairy cattle. There were 222 of dairy cows observed (53 Czech Pied and 169 Holstein cows). The results of reproduction were evaluated as unsatisfactory. Length of calving interval overreached recommended 400 days in 56,25 % of Holstein and in 33,33% of Czech Pied cows. Also the mean value of insemination index 2,39 exceeds the optimum of 1,8-2,0.

Incidences of uterine infections in dairy cattle are high between parturition and Day 21 postpartum. Dairy cows with uterine infections are at risk for prolonged periods of days open and multiple services before becoming pregnant. Neutrophils are the first wave of immune system defense against uterine contamination. Neutrophil function seems to be mediated by reproductive hormones and good uterine health is related to properly functioning neutrophils. To elucidate the interaction between reproductive hormones, neutrophils and uterine health in dairy cows the objectives of this research were to evaluate: 1) changes in circulating white blood cell populations during the estrous cycle, 2) the effects of prostaglandin F₂[subscript α](PGF₂[subscript α]) on circulating white blood cell populations and 3) the effects of a two-injection PGF₂[subscript α] regimen on uterine neutrophil and bacterial populations and numbers of days open and services per conception. In the first experiment, the effect of stage of the estrous cycle on plasma neutrophil numbers was evaluated. Neutrophils were observed throughout the entire estrous cycle and numbers were greatest (P<0.05) on Day 14 (mid-cycle), when the corpus luteum was the dominant ovarian structure and plasma progesterone was at its acme. In the second experiment, plasma neutrophil numbers were examined in cows after injections of saline or the PGF₂[subscript α] pharmaceutical product, Lutalyse. Compared to saline, numbers of neutrophils were greater (P<0.05) 4 and 8 hr after Lutalyse injection. In the third experiment, neutrophil numbers were examined after injections of saline, Lutalyse or the PGF₂[subscript α] analog, Estrumate. Compared to saline, numbers of neutrophils did not differ (P>0.10) from cows injected with Lutalyse or Estrumate. In the fourth experiment, uterine bacterial populations and numbers of neutrophils were quantified in cows treated with Lutalyse or saline on Days 0 and 14 or 14 and 28 postpartum. Compared to saline, Lutalyse treatment decreased (P<0.05) total bacteria present in the uterus and increased (P<0.05) the number of uterine neutrophils. In experiment five, numbers of days open and services per conception were evaluated in cows treated with Lutalyse or saline on Days 0 and 14 or 14 and 28 postpartum. Compared to saline, Lutalyse decreased days open (154.7 ± 14.1 vs. 120.1 ± 7.9 days, respectively; P<0.05) and services per conception (3.0 ± 0.4 vs. 2.3 ± 0.2 services, respectively; P=0.09). These results suggest PGF₂[subscript α] treatment can increase neutrophil and depress bacterial cell populations in favor of the dairy cow's uterine health and may explain why fertility is improved when PGF₂α is administered early in the postpartum period. / Graduation date: 2012

A positive phenotypic correlation between milk protein percentage and reproductive performance in dairy cattle, especially during early lactation has been recently reported. The objective of this study was to quantify the relationship between milk protein percentage and different measures of fertility in Irish, seasonal calving, dairy cattle using data from experiments comparing strains of Holstein-Friesian cows under different feeding systems. The relationships between body condition score, milk production and fertility were also investigated. The data used in this study consisted of 584 lactation records over a 5-yr period. Principal component analysis and logistic regression was used to study the relationship between milk protein percentage and fertility performance of the cow. Greater milk protein percentage during the first 60 days post-calving was associated with better reproductive performance. The probability of a cow being submitted in the first 21 days of the breeding season increased with increased milk protein percentage during early lactation. Similarly, the probability of a cow becoming pregnant to its first service or to the whole breeding season also increased. Cows were classified as either high or low milk protein percentage based on their protein percentage over the whole lactation. Cows in the high milk protein group had a 7% greater conception rate compared to cows in the low protein percentage group. In conclusion, cows with higher protein percentage, especially during early lactation are submitted earlier in the breeding season, and have a higher conception rate. Physiologically, the shortage of glucose caused by negative energy balance restricts the synthesis of milk protein in the udder. On the other side, negative energy balance also causes the reduction of IGF-I, LH and oestradiol, which consequently delay the ovarian follicular development and finally reduces fertility. Therefore, there is a biological explanation for the association between milk protein percentage and fertility performance.