SOMATIC-CELLS IN SHEEP MILK IN RELATION TO MILK-PRODUCTION AND COMPOSITION DURING SUCKING AND MILKING

Negative effects of subclinical mastitis on milk production were descr ibed in dairy cows, goats and partly in lambing ewes. Great changes in milk composition are regularly observed at mastitis. Somatic cell cou nts (SCC) can be an appropriate indicator of subclinical mastitis and milk quality in sheep. The objective of this paper was to determine a relation between SCC and the milk production and quality in lambing ew es of Tsigai (T) and Improved Valachian (IV) breeds during sucking (S) and milking (M) periods. A trial was conducted on lambing ewes of T a nd IV breeds in the Ist to the 3rd lactation in 1993 and in the Ist to 4th lactation in 1994. The lambing ewes were housed and managed under the same conditions over the experimental period. Milk samples for de termination of SCC (Fossomatic 90, mfd, by Foss Electric Co., Denmark) and contents of solids (% S), proteins (% P), fat (% F) and lactose ( % L. Multispec infrared analyzer) were taken by ewe milking in S perio d after intravenous application of oxytocin (5 i.u./ewe) and as part o f milk recording at morning hand milking in M period. Milk samples wer e taken in such a way to be representative ones of the ewe's whole mil k yield. Daily milk production (MP) was also recorded in individual ew es on the day of milk sampling; in S period, it was calculated from a milk quantity produced within a 4-hour interval and milked after the s econd oxytocin application, in M period from the yield obtained at mor ning and evening milk measuring. Calculation of linear phenotype corre lations (r) was used to evaluate the relation between SCC and MP, or t he content of basic components. Transformed SCC data (log(10)SCC) were used for regression analysis. Tab. I shows average values of SCC, mil k production and composition in ewes in S and M periods in relation to the particular control milk measurings (CMM). Analyses of 369 and 497 milk samples in 1993 and 1994, revealed average SCC per lactation (S + M periods) at a level of 364 x 10(3)/ml and 1091 x 10(3)/ml, log(10) (SCC) 2.25 and 2.68, resp.; 18.1% and 19.8% S; 4.98% and 5.33% P; 7.41 % and 8.78% F, and 4.78% and 4.79% I,. Average MP per lactation amount ed to 1,077 mi in 1993 and 987 mi in 1994. There was a significant ind irect relation for T and IV breeds between log(10)(SCC) and MP (Tab. I I) both in S and M periods (P < 0.05 to 0.001). The phenotype correlat ion coefficient ranged from -0.160 to -0.309. The correlation coeffici ent between log(10)(SCC) and MP over the years 1993 and 1994 in aggreg ate (regardless of the breed) amounted to -0.291 in S period and to -0 .192 in M period (P < 0.001, Tab. III, Figs. 1 and 2). According to th e aggregate data over 1993 and 1994 (Tab. III), log(10)(SCC) is statis tically significantly (P < 0.001) directly related to % P (r = 0.431 i n S period - Fig. 5 and r = 0.361 in M period - Fig. 6) and also to %F (0.520 - Fig. 3 and 0.293 - Fig. 4) and indirectly related to % L (-0 .347 - Fig. 2 and -0.314 - Fig. 3). Statistically significant relation s (P < 0.001) between log(10)(SCC) and % S, % P, % F and % L were dete rmined in T and IW breeds, while r values were higher in S period in m ost cases (Tab. II). The results indicate potential differences in the evaluated relations when the years or lactation stages are compared ( S or M period, Tab. III).