The impact of extreme heat or cold can vary widely depending on the stage of life and reproductive status of animals. Housing bulls
in high density situations (1.2 m2 per animal) results in
an acute rise in plasma cortisol concentration that is detrimental to growth. Bulls housed at 4.2 m2 per ani- mal had depressed interferon-gamma production when compared to those housed at 2.7 and 1.2 m2 per animal [10].