New advancements in udder health management


Differential somatic cell count (DSCC) is a new supplementary parameter to SCC for udder health management. Using these two parameters in combination leads to better identification of mastitis at the end of the lactation period and thus can be valuable regarding dry cow therapy decisions.


BY DR DANIEL SCHWARZ, DAIRY FARMING SENIOR SPECIALIST AT FOSS, DR Z. LIPKENS, DR S. PIEPERS AND DR S. DE VLIEGHER, GHENT UNIVERSITY, BELGIUM


S


omatic cell count (SCC) in milk provide an indication of the inflammatory response in the mammary gland thus are a well-established indicator for masti- tis, also at the end of the lactation period. However,


SCC does not distinguish the individual immune cells occur- ring in milk. Besides SCC, the composition of the immune cells changes evidently during mastitis. Changes in the com- position of immune cells have even been described for cases where SCC stayed at low levels. Specifically, macrophages mainly having surveillance functions are the predominant cell population in milk of healthy udder quarters. On the oth- er hand, polymorphonuclear neutrophils (PMN or granulo- cytes) having the main function to phagocytise and thus eliminate bacteria are the predominating cell population in milk of inflamed quarters. The third population of immune cells are lymphocytes regulating the immune response and they occur in fairly low concentrations in milk. The new DSCC parameter represents the combined proportion of granulo- cytes and lymphocytes as a percentage of SCC, and, similarly to SCC, elevated DSCC results can be associated with pres- ence of mastitis. FOSS has developed a new generation of high-throughput milk analysers that allow simultaneous measurement of SCC and DSCC. These instruments are typi- cally applied for analysis of dairy herd improvement (DHI) samples and located in milk-testing laboratories.


Selective dry cow therapy Around 70% to 75% of antimicrobials applied on dairy farms are used in connection with udder health, either in form of treatments or in a preventive manner. Half of all antibiotics are used for dry cow treatment alone. Hence, selective dry cow therapy is a highly valuable tool to reduce the consumption of antimicrobials on dairy farms, as is desired by the general public being concerned about the increasing threat of antimicrobial resistance in human and veterinary medicine. Selective dry cow therapy based on DHI records (mainly SCC) is


▶ COW HEALTH | AUGUST 2020 29


already performed in many countries since several years (e.g. the Netherlands) and has led to an apparent reduction in the use of antimicrobials. This background, the availability of the new DSCC technology and the fact that DHI samples are typically readily available from each lactating cow enrolled to a DHI programme once per month led us to investigate the new DSCC parameter as an additional indicator for mastitis at the end of the lactation period in a specifically designed study.


Testing for the presence of pathogens Ghent University and FOSS collaborated with 15 dairy farms in Flanders, Belgium, having on average 91 cows. During the eight months study period, DHI samples were collected rou- tinely and, in addition, hand-stripped samples (one sample per cow) representing an equal amount of approximately 2.5 mL of milk from each quarter were collected from cows in the period 5 days before dry-off right before attaching the milking clusters at one of the milking’s in that period. Beyond that, aseptic quarter foremilk samples were collected at one of the milking’s in the same period. While the DHI and hand-stripped samples were analysed for SCC and DSCC, the aseptic quarter foremilk


Routine DHI testing is a proven way to improve milk quality and herd efficiency.


PHOTO: DANIEL SCHWARZ


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