Abstract:
The biological cycles of milk production and reproduction determine dairying profitability
thus making management decisions dynamic and time-dependent. Diseases also negatively
impact on net earnings of a dairy enterprise. Transition cows in particular face the challenge
of negative energy balance (NEB) and/or disproportional energy metabolism (fatty
liver, ketosis, subacute, acute ruminal acidosis); disturbed mineral utilization (milk fever,
sub-clinical hypocalcemia); and perturbed immune function (retained placenta, metritis,
mastitis). Consequently NEB and reduced dry matter intake are aggravated. The combined
effects of all these challenges are reduced fertility and milk production resulting in diminishing
profits. Risk factors such as NEB, inflammation and impairment of the immune
response are highly cause-and-effect related. Thus, managing cows during the transition
period should be geared toward reducing NEB or feeding specially formulated diets to
improve immunity. Given that all cows experience a reduced feed intake and body condition,
infection and inflammation of the uterus after calving, there is a need for further
research on the immunology of transition dairy cows. Integrative approaches at the molecular,
cellular and animal level may unravel the complex interactions between disturbed
metabolism and immune function that predispose cows to periparturient diseases.
