Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/1999
Publication Date: 10/1/2000
Citation: Paape, M.J., Duenas, M.I., Wertemann, R., Douglass, L.W. 2000. Effects of intramammary infection and parity on calf weaning weight and milk quality in beef cows. Journal of Animal Science. 78(10):2508-2514.
Interpretive Summary: More than 60% of the 38 million beef cows on pasture in the United States have subclinical mastitis. Of those infections, 15% of all mammary quarters for cows with multiple lactations are infected with Staphylococcus aureus. For beef cows with few lactations only 1 to 4% of the quarters are infected. This organism is highly contageous mastitis pathogen that destroys mammary secretory tissue and results in decreased milk production. It is spread from cow to cow through the transfer of infected milk from one mammary quarter to another by suckling. Weaning weight of calves from cows with subclinical mastitis in four mammary quarters was 5 kg less than herd mates. This represents a loss of $10/calf. A mastitis control program for beef cows will reduce incidence of mastitis, the spread of Staphylococcus aureus and increase calf weaning weight.
Technical Abstract: Effects of number of infected quarters, milk somatic cell counts, milk components, and intramammary infection were studied at weaning on 164 beef cows. Percentage of infected cows ranged from 43% at post-calving to 66% at the first weaning. Cows with 3 or 4 infected quarters had higher milk somatic cell counts than cows with 0, 1, or 2 infected quarters. Among bacterial isolates, Staphylococcus aureus infected quarters had the highes milk somatic cell count. Percentages of butterfat and lactose were lower in milk from infected quarters than from uninfected quarters. Infections by S. aureus and coagulase negative staphylococci were the most common and accounted for 65% to 78% of the infections. Percentages of infected cows and quarters, infections caused by S. aureus and blind quarters increased with parity. Intramammary infections did not affect calf weaning weight.