The Hebrew University in Israel evaluated the effects of mastitis, determined by the pattern and level of somatic cell count (SCC) around the first artificial insemination (A.I.) on conception rate (CR). Data was collected from 287,192 A.I. and milk records over a seven-year period and examined based on the probability of conception with SCC elevation relative to timing of A.I.

A SCC threshold of 150,000 cell/mL of milk was set to distinguish between uninfected cows and cows with mastitis. Cows with a high SCC before and low SCC after A.I. were designated cured, those with low SCC before and high SCC after A.I. were declared newly infected, and cows with high SCC before and after A.I. were diagnosed with chronic mastitis. Full data analysis included the following, published in the September 2011 issue of the Journal of Dairy Science:

Compared to uninfected cows, the cured, newly infected and chronic groups had lower CR.

In the chronic, subclinical group, probability of conception was lowered by 14.5 percent in the mid and moderately elevated SCC subgroups and by 20.5 percent in cows with high SCC elevation compared with the uninfected group, obtaining CR of 29.7 and 39.4, respectively.

A single high elevation of SCC lowered the probability of conception by 23.6 percent when it occurred in the 10 days before A.I., but not when it occurred after.

30 days following A.I., the probability of conception for infected cows was lowered by about 23 percent.

The probability of conception was lowered in cows with uterine and foot health problems in second and later lactation and in the summer, even when no mastitis was detected.

Findings indicate that SCC elevation around the time of breeding was associated with a significant reduction in probability of conception. Even a mild spike in SCC was shown to reduce CR.

Source: Dairy Cattle Reproduction Council