The objective of the present study was to evaluate the effects of clinical mastitis at the beginning of lactation on reproductive performance of dairy cows in Algeria. Calving to first insemination and calving to conception intervals, number of insemination per conception and conception rate at the first artificial insemination were recorded for 432 cows from 16 dairy herds in Algeria. Cows were examined for clinical mastitis during milking by the personnel or the herd manager. A clinical mastitis case was recognized by the presence of modified milk (more watery, presence of lumps, abnormal odor) or by the presence of signs of inflammation in one or all quarters of the udder. Cows were classified according to the time of clinical mastitis occurrence in three groups: cows presenting clinical mastitis before the first artificial insemination (MG1; n = 62 dairy cows), cows presenting clinical mastitis between the first artificial insemination and pregnancy diagnosis (MG2; n = 54 dairy cows), and cows without any signs of clinical mastitis before or after the first insemination (Control - CG; n = 316 dairy cows). Calving to first artificial insemination and calving to conception intervals for cows with signs of clinical mastitis before the first artificial insemination (137.26 ± 7.36 days and 180.48 ± 7.25 days) and in cows with signs of clinical mastitis after the first artificial insemination (190.85 ± 9.23 and 202.51 ± 10.32 days) were significantly (p < 0.05) higher than that of the clinically healthy cows (111.01 ± 5.42 and 147.32 ± 8.44 days), respectively. The number of inseminations per conception in cows that exhibited clinical mastitis before the first artificial insemination (1.94 ± 0.85) and in cows with signs of clinical mastitis after the first artificial insemination (2.4 ± 0.94) was significantly higher compared to that of the control cows (1.61 ± 0.75) (p < 0.05). Conception rate at first artificial insemination in control cows was significantly (p < 0.05) greater than in cows that exhibit clinical mastitis before or after the first artificial insemination (61.39 compared to 38.71 and 33.33% for CG, MG1 and MG2, respectively). The negative effects of clinical mastitis were observed in both primiparous and multiparous cows. In conclusion, results of our study clearly indicate that, clinical mastitis decreases reproductive performance of dairy cows.
Key words: Clinical mastitis, calving to first artificial insemination interval, calving to conception interval, reproduction, dairy cattle.
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