|BROWN, JR., A.|
Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/1998
Publication Date: N/A
Interpretive Summary: Mastitis is responsible for substantial losses in the dairy industry through lowered milk production, wasted milk, and decreased animal longevity. There is very little information on mastitis in beef cows, but it is reasonable to hypothesize that similar losses could exist in beef cows. Research at Booneville, AR was performed to evaluate Angus, Brahman, and reciprocal-cross cows for presence of mastitis-causing organisms (MCO's)and the effects of these MCO's on productivity. Results from this research substantiated the presence of MCO's in a large percentage of cows evaluated. There was some evidence of fewer MCO's in crossbred cows, suggesting the possiblity of tolerance or resistance in these cows. There were trends for MCO's to be present at a higher level in cows on endophyte-infected tall fescue as well as a trend for the proportion of MCO's to increase with time of lactation. There was less evidence that the presence of MCO's decreased weaning weights or milk production but a more quantitative evaluation using somatic cell counts suggested lower productivity in cows with higher somatic cell counts. Results from this research suggest that management designed to minimize incidence of mastitis might also prove beneficial in beef cow herds.
Technical Abstract: Angus (A), Brahman (B), and reciprocal cross cows (AB, BA) were sampled in 1994 (67 hd) and 1995 (48 hd) to evaluate the effect of breed and forage on the presence of mastitis-causing organisms (MCO's) . In 1994, cows were managed on either endophyte-infected tall fescue (E+) or common bermudagrass (BG) and milk samples were taken in August, September and October. In 1995, cows were managed on E+, BG, or both forages during the appropriate seasons. Milk samples for 1995 were taken in May, July, and September. In both years, aseptic techniques were used to sample from all four quarters of each cow for diagnostic bacteriology. Any cow having at least one quarter positive for MCO's on a given date was designated positive. In 1994, percent of cows with MCO's was 52.0%, 29.1%, 25.4%, and 40.0% for A, AB, BA, and B, respectively, averaged over month. Heterosis was estimated as -18.7% (P<.11) and there was a trend for MCO's to be higher on E+ (43.0%) than BG (30.2%). In 1995, percent of cows with MCO's was 41.8%, 40.5%, 3.7%, and 42.4% for A, AB, BA, and B, respectively, averaged over month. Heterosis averaged -20.0% (P<.10) and there was a trend for MCO's to be higher on E+ (39.1%) compared to BG (23.1%) or the E+-BG combination (34.1%). There was little evidence that presence of MCO's affected milk yield or calf preweaning performance. However, there was a negative relationship between milk production or calf preweaning performance and milk somatic cell count. These data suggest that favorable heterosis for absence of MCO's is possible and that factors associated with E+ may increase MCO's in cows grazing E+.