Increased stress in animals can lower immune system function and hence decrease resistance to disease. The objectives of the study were to determine the effects of two stressors on lymphocyte function in lactating dairy cows. Jersey cows were allocated to four, 7-day treatments in a 2 x 2 factorial plan. The factors were level of feeding (4% bodyweight vs 3% bodyweight) and lying time (free choice lying vs prevention of lying from 1500 to 0645 h daily). Blood samples collected during the pre-treatment and treatment periods were analysed for in vitro lymphocyte proliferative response and sub-populations. Lymphocyte proliferative response was not affected by feed level or lying time. Only minor changes occurred in lymphocyte sub-populations. Within the fully-fed cows, lying deprivation resulted in a greater proportion of CD8 (suppressor) cells. These data indicate that lymphocyte function in lactating cows may not be compromised by medium term restrictions in feeding and lying, and that any stress-induced decreases in cell-mediated immunity which occur in practice, are the result of more severe, or prolonged, conditions.
Proceedings of the New Zealand Society of Animal Production, Volume 59, , 195-197, 1999
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