A comparison of herbage intake between castrated and uncastrated grazing young cattle

Experiments were conducted to investigate the possible differences in dry matter intake, bite weight and bite dimensions between young bulls and steers of similar age and genotype offered pasture over a similar range of sward height. In experiment I (i) and I (ii), 20 cattle of 4 and 5 months old respectively (10 bulls and 10 steers), were divided into 4 groups (2 groups bulls and 2 groups steers). A 0.4 ha paddock with ryegrass (Lolium perenne) and white clover (Trifolium repens L) dominant pasture was used in experiment I and subdivided into 4 plots. The grazing area was reduced daily by 10% per day from day 2 until the end of the experiment (day 12). Each group was randomly assigned to 1 of these 4 plots. In experiment II, 0.8 ha paddock of tall fescue (Festuca arundinacae) dominant pasture was used and divided into 4 plots of each of 0.2 ha. All plots were reduced daily in size by 5% from day 2 until the end of the experiment (day 8). The same animals used in experiment I were reused in experiment II (18 months old) and regrouped same as in experiment I. Each group was randomly assigned to graze 1 of the 4 plots. The age of the animals in this experiment was 18 months old. Daily herbage dry matter intake in experiment I and II was measured by chromic oxide/sesquioxide and agronomic methods. Sward surface height was measured daily as a mean of 40 readings in plots grazed by bulls and steers. Herbage mass (kg DM/ha) was estimated from the relationship between sward surface height and herbage mass within cut quadrats. Mean daily sward surface height, herbage mass, dry matter intake and dry matter digestibility were not significantly different in plots grazed by bulls and steers in either experiments (p>0.05), however they significantly declined (p