DIURNAL-VARIATION IN THE SOMATIC-CELL COUNT OF EWE MILK

The hourly variation of SCC in milk throughout the period between milk ings was studied in 60 half udders of 30 Manchega ewes (10 each in fir st, second, and third parities) for 2 consecutive d. The interval betw een milkings was 12 h. The effects half udder, sampling time and day, interaction hour by day, and parity were statistically significant and explained 58.9, 11.9, 1.3, .6, and .3%, respectively, of total varian ce. The hourly repeatabilities of SCC and log SCC within each day (.83 and .86, respectively) were high. The SCC increased 70% in the 1st h postmilking and then gradually decreased until the next milking. The v ariations in SCC from 6 h postmilking were statistically significant b ut of less quantitative importance than those from the previous hours. The mean SCC of a.m. and p.m. milkings were very similar on both days (112 and 114 x 10(3) cells/ml). The mean SCC difference of milk betwe en a.m. and p.m. milkings was 14%. This variation could be considered to be normal in the ewe for an interval of 12 h between milkings. Thes e results suggest the standardization of time of sampling to avoid err oneous classifications of sheep based on SCC of milk.