Every year at "preg" checking time, ranchers evaluate cows and make decisions as which to remove from the herd. This fall will find many producers culling the herd deeper than usual because of very short forage supplies in many areas of Oklahoma. One criteria that should be examined to cull cows is udder quality. Beef cattle producers are not as likely to think about udder health and shape as are dairy producers, but this attribute affects cow productivity and should be considered.
Ranchers may be surprised to find that about 2/3 of the range cows tested experimentally were infected with one or more mastitis-causing bacteria in one or more quarters. Two previous studies (one in 1977 and another in 1983), indicated that the occurrence of clinical mastitis in the beef cows herds were 17.5% and 11.9%, respectively. These caused reduced weaning weights of 12.5% and 7.3%, respectively. A later study (1986) of beef cows found a higher percentage of clinical mastitis of 37%. The weaning weight loss of calves nursing infected cows was 9.6% and these researchers noted an economic loss of $31.43 per calf due to occurrence of mastitis in the dam. The presence of the organisms does not necessarily mean that the cow has clinical mastitis and her milk production will suffer. It is known that the incidence of dry quarters increase with cow age.
An experiment conducted recently at the Range Cow Research Center near Stillwater gives some indication as to the impact of mastitis on beef cow performance. Also the OSU scientists examined the effects of intramuscular treatment with "long-acting" oxytetracycline at weaning time and again at calving on the subsequent milk production and calf weaning weights. They found that cows with one or two dry quarters had calves with severely reduced weaning weights (50 - 60 pounds) compared to cows with no dry quarters. Treatment of cows at the previous weaning and/or after calving with the long-acting oxytetracycline did not influence calf weaning weight. Read the details of this study in the 1996 OSU Animal Science Research Report. Check the "Resources" section for a direct link to that report.
The heritability estimates of udder characteristics are variable. Research with Hereford cattle reported heritability estimates for udder capacity and shape to be relatively low at .12 and .15 respectively. A study done in Brahman cattle for the heritability of udder soundness indicated indicated that progress could be made by selecting for udder soundess. They reported that 25% of the differences in udder soundness was due to genetics.
An evaluation system for udder soundess has been developed and used
by some breeds. Teat shape and udder suspension are the two primary
characteristics evaluated. Below are drawings representing sound
udders on the left and unsound udders on the right.
The first two drawings are teat shape. The very "funnel" shaped
teat may have been mastitic in the past. New born calves will find
it difficult to nurse such a teat.
Teat Shape: Note the large "funnel-shaped" teats on the cow on the right
Udder suspension: Weak udder suspension leads to "pendulous" broken-down udders that also are very difficult for young calves to nurse.
Both cows on the right would be excellent candidates for culling this
fall.