WHAT IS THE ECONOMIC IMPLICATIONS OF SOMATIC CELL COUNT?

Milk quality is of major economic importance in dairy production. Low milk quality is associated with dairy products of inferior quality, which translates to economic losses. The concentration of somatic cells, commonly known as somatic cell count (SCC), is the most widely used measure of raw milk quality. Many milk buyers worldwide and also in South Africa, routinely test for SCC of bulk-tank samples of milk from producers. Premium prices are awarded for milk quality that exceeds certain thresholds, and penalties are imposed on milk that falls below minimum quality thresholds, as determined by SCC. Thus, SCC directly affects revenue from the sale of milk. However, the magnitude of the revenue loss has not been studied in depth. As a result, the researchers referenced below carried out a study to determine the economic value of SCC in South African Holstein and Jersey cattle; a second objective being to establish the relative emphasis SCC should be allocated in breeding objectives.

Bulk-tank SCC was calculated from individual cow test-day SCC for 183 Jersey and 209 Holstein herds that participated in the national milk recording scheme in 2012. The herds were separated in TMR and pasture-based production systems. SCC premium schemes of the two major milk buyers in the country were used for the purpose. The economic value of SCC was determined as the simulated change in profit per cow per year, following a 1% increase in individual bulk-tank SCC. The estimated breeding values (EBVs) were based on log10 transformed SCC (somatic cell score, SCS); therefore the final economic value could be expressed in Rand per SCS. Relative economic values, standardized to the value of protein which is the most important trait, were used to compare the relative importance of SCS with other objective traits.

The results showed that an increase in SCS by one unit resulted in decreases in profit ranging from R491 to R1796 per cow per year, depending on the breed, the production system and the payment system. The economic value of SCC was nearly double in Holsteins compared with Jerseys, and in the TMR system compared with the pasture-based system. SCS was among the most important traits in the breeding objective, its value ranging from 26% to 118% compared with the most important trait, protein.

It is clear therefore that a high relative emphasis should be placed on SCS in breeding objectives for Holstein and Jersey cattle.

Reference:

Banga, C.B., Neser, F.W.C.& Garrick, D.J., 2014. The economic value of somatic cell count in South African Holstein and Jersey cattle. S.A. Journal Anim. Sci. 173-177.