Housing and Environment for Dairy Calves

Many cases of poor health in calves have been traced to bad management and inadequate ventilation in the calf nursery. Important management principles for improved calf health include calf housing isolated from the adult herd and periodic depopulation and sanitizing of the calf nursery area. In good weather, low-cost calf rearing portables such as the “calf hutch” can provide alternative housing during the cleanup period.

Calf nursery ventilation systems must have flexibility to give the full winter-to-summer range of controlled ventilation rates and critical air inlet adjustments. Earlier recommendations were for three stepped ventilation rates of 3.3, 6.6 and 24 L/s per calf to cover the range from cold winter to warm summer weather. Later recommendations are for a simpler two stepped fan system starting at 6.7 L/s (continuous winter rate) and increasing to 50 L/s for temperature control in warm to hot weather.

Even with the best insulated construction, increased supplementary heating is required to support this increased continuous winter ventilation. To save energy the heating must be controlled to stop before the higher-rate ventilation starts. Other design features for more uniform temperatures and improved calf nursery ventilation include: 1) preheating the ventilation air before it enters the calf room, 2) distributing air to the ceiling with round holes and adjustable slots adjusted to give at least 4 m/s inlet velocity, 3) using a properly sized centrifugal fan running continuously to exhaust air from near the floor in winter and 4) protecting air intakes and fan openings from the effects of wind. Air recirculation systems and variable-speed fans are not recommended.

     

The pathology of chronic erosive dermatopathy in Murray cod, Maccullochella peelii peelii (Mitchell)

Chronic erosive dermatopathy (CED) is a disease of intensively farmed Murray cod in Australia that has been reported in association with the use of groundwater (mechanically extracted from shallow boreholes) supplies. CED results in focal ulceration of the skin overlying sensory canals of the head and flanks. Trials were conducted at an affected fish farm to study the development of the condition, both in Murray cod and in goldfish, and also to assess the reported recovery of lesions when affected fish were transferred to river water. Grossly, lesions began after 2-3 weeks with degeneration of tissue at the periphery of pores communicating with the sensory canals. Widening of these pores along the axis of the canals resulted from a loss of tissue covering the canal. Histopathologically, hyperplasia of the canal epithelial lining was seen after 3 weeks in borehole water and subsequent necrosis and sloughing of this tissue resulted in the loss of the canal roof. Canal regeneration occurred when fish were transferred from borehole water into river water. The lack of lesions in other organs and the pattern of lesion development support exposure to waterborne factors as the most likely aetiology.