RESUMEN
A 2 x 3 factorial design was used to study the impact of rearing systems, individual (I) versus group (G) and different levels of milk/skim milk feeding (F1, F2 and F3) on hemato-biochemical profile, disease incidence and average daily gain of crossbred (Bos indicus x Bos taurus) calves. Six calves were taken in each group on the basis of their birth weight and housed in individual (2.20 x 1.16 m(2)/calf) or in group pens (2.20 x 1.03 m(2)/calf). After 3 days of colostrum feeding, calves were allocated to one of three different milk feeding schedules: milk fed up to 8 weeks of age (F1), milk up to 4 weeks followed by 50% replacement by skim milk up to 6 weeks and 100% thereafter (F2) and 100% replacement of milk with skim milk after 4 weeks (F3). Calf starter and cereal green fodders were fed ad libitum from the second week of age and continued for 14 weeks. Parameters on health and disease profiles of calves (disease incidence, duration of illness, response to treatment and recovery) and weekly live weight change were recorded. Calf scour predominated (52.8%), followed by joint ill (25.0%) and respiratory infections (19.4%). The disease incidence was greater (P < 0.01) in individually housed calves (94.4 vs. 55.9%). The management of navel ill required longer recovery (7.01 days) followed by joint ill (4.87 days) and respiratory infection (4.86 days). The average daily gain during 0-14 weeks of age was higher (P < 0.01) in group-housed calves (433 +/- 22 vs. 355 +/- 31 g), while the effect of feeding was not significant. Blood samples collected at 4, 8 and 14 weeks of age showed some periodic higher concentrations (but within normal range) of plasma urea and total protein in group housed calves on F2 and F3 feeding schedules in response to high protein intake. Other parameters remained non-significantly different. Thus, group-housed calves can be reared successfully with comparatively better performance and less illness than individually housed ones under the present health care and housing management system. However, the system should not be used as a substitute for good management, and frequent observations of calves should be an integral part of any successful rearing program.