Relationship of herd average somatic cell count and spontaneous Relationship of herd average somatic cell count and spontaneous recovery from subclinical mastitis recovery from subclinical mastitis

The rate of spontaneous recovery from subclinical mastitis was evaluated in 56 Kansas .D~I herds participating in the Somatic Cell Count (SCC) program. Herds were classified as low (000,000) or high (>600,000) based on herd sec average. Comparisons between low and high SCC-herds were made for each cow's ability to recover from a subclinical case of mastitis (>600,000 SCC). Low-SCe herds had a rate of spontaneous recovery that was more than three times greater than that of high-SCe herds. Average SCC of cows with subclinical mastitis was similar in low and high herds J as well as the a verage sec of cows following spontaneous recovery. Results illustrate the importance of monitoring monthly sec reports.


Introduction
The Somatic Cell Count (See) of an individual cow is a good indicator of intramammary infection (subclinical mastitis).As the SCC increases above 200,000, there is an increasing chance that one or more quarters are infected with mastitis causing bacteria.These infections are considered subclinical when there are no signs of abnormal milk.
Subclinical mastitis causes increased SCCs since leucocytes migrate to the mammary system in an attempt to destroy the invading bacteria.If the leucocytes win the battle, as evidenced by a see lower than 200,000, then it is considered that the cow spontaneously recovered from subclinical mastitis.
The Mid-States Dairy Records Processing Center's SCC Report denotes cows with sees greater than 600,000.These cows are considered to be subclinical mastitis cases, although any cow with a SCC higher than 200,000 might be infected.Some of the cows appearing on the high SCC list drop below 200,000 SCC without any treatment, which suggests that the leucocytes cured the infection and thus spontaneous recovery occurred.

Procedure
The rate of spontaneous recovery from subclinical mastitIs in Kansas DHIA herds was evaluated by surveying 56 herds participating in the Kansas DHIA SCC program.The herds were ranked high or low according to the sec average.Those herds averaging more than 600,000 see were summarized in the high group and those averaging less than 300,000 were included in the low group.Each cow was evaluated during the previous six DHI tests.Cows showing see greater than 600,000 were considered subclinical cases.Those cows with sec lower than 200,000 the following month were considered to be spontaneous recovery cases.

Results and Discussion
The survey (Table 1) illustrates that the rate of spontaneous recovery from subclinical mastitis is more than three times higher (43.4% vs 12.1 %) in herds averaging 000,000 see than in herds averaging >600,000 sec.The function of leucocytes, which are the major components of the sec, is to alleviate stress.
Therefore, it appears that milking management results in much less stressful conditions in lower see herds.Another interpretation would be that the leucocytes have a much better opportunity to cure subclinical mastitis in low sce herds.a Any cow with a sec >600,000 is designated as subclinical, haNever, sooe of these cows probably were shaving clinical mastitis.
bSubclinical cows were defined as those cows having one or more see >600,000 during the last six tests.
cPercent cows subclinical is the percentage of cows with at least one see >600,000 dur ing the las t six tes ts.
Table 2 shows that the a verage sec of cows with subclinical mastitis and th~se t.hat recovered was simi1~r.Again., this illustrates that milking management, whIch mc!u~es 1) c~w preparatIon and mIlking techniques, 2) sanitation, 3) housing, and 4) mIlkmg eqU1pm~nt, are such that cows with subclinical mastitius have a much better chance for spon taneous recover y.The much higher incidence of subclinical mastItIs in high sec herds and the low rate of spontaneous recovery should be reason enough for every dairy producer to review milking management.In addition, many studies have shown that milk production is reduced as the sec increases, since there is more subclinical mastitis.
Most authorities do not recommend treating high-SeC cows with antibiotics as an effective means of lowering the sec.Apparently the most effective means of reducing high SCC is to improve milking management, so that the leucocytes have an opportunity to cure subclinical mastitis.

Table 2 .
Somatic Cell Count of cows with subclinical mastitis.