The objective of the study was to investigate the effect of increased volumes of milk feeding as well as the effect different group sizes may have on the growth and health of Jersey calves. One hundred and twenty 3-day old heifer calves were randomly assigned to one of four treatment groups (30 calves each) and calves in groups one and two were assigned into four subgroups (15 calves each). Two groups received unrestricted volumes of milk (HMV), while two groups received restricted volumes of milk (RMV) during the preweaning period. The calves were weaned after 6 weeks. Feed intake, growth rates, health and cross-sucking behaviour of calves were monitored until all the calves in the trial reached at least 60 days of age. The effects of milk volume and group size on growth rates and the risks of diseases were evaluated using multiple linear- and logistic-regression models. During the milk-fed stage, the HMV calves drank 72% more milk than calves fed conventionally. Probably as a result of the much higher intake of milk, the HMV calves gained 154 g/d more weight than the RMV calves before weaning (P < 0.001), resulting in a 6.3 kg weight advantage on d 42. Birth weight of the HMV calves showed a strong linear relationship with milk intake (Pearson’s r = 0.696, P < 0.001) and preweaning ADG (Pearson’s r = 0.426, P < 0.001). Calves that were provided with more milk consumed less calf starter, reflecting effective substitution of milk with concentrate. However, after the calves were weaned, the difference in starter intakes disappeared. This resulted in no treatment differences in weight gains over the postweaning period, and on d 60 the HMV calves maintained an advantage in mean (± SD) body weight (67.6 ± 7.9 kg vs. 60.8 ± 6.6 kg for the HMV vs. RMV calves). With the exception of keratoconjunctivitis, the incidence of disease in milk-fed calves was low and did not differ between HMV and RMV treatment groups. Days of treatment for keratoconjunctivitis (birth to d 42) was significantly higher (P < 0.05) for calves in the large HMV group compared with calves in other groups. Smaller groups showed a higher incidence of diarrhoea during the preweaning period (OR = 3.23; P < 0.01). Over the whole trial period, the gain-to-feed ratio of HMV calves was 9.6% better than calves receiving restricted milk volumes. However, the cost per kg body mass gain was 12% higher for HMV calves. Cross-sucking observations showed that the incidence in the preweaning period differed greatly between the groups (1.7% vs. 75.5% for HMV vs. RMV groups; P < 0.001). During the last 10 days of the trial, this difference decreased, but was still significant (10.0% vs. 19.1% for HMV vs. RMV groups; P < 0.001). The conclusion was that the feeding of high volumes of milk to dairy calves will have a significant positive effect on growth rates, without compromising their health or the intake of solid food after weaning. Additionally it allows calves to be housed in groups with less problems of cross-sucking. Copyright / Dissertation (MSc)--University of Pretoria, 2008. / Production Animal Studies / unrestricted