The Importance of Stocking Rate to the Uptake of Gastrointestinal Nematodes by Grazing Calves
The effect of three different stocking rates and two grazing methods (3 x 2 factorial experiment) on grass production, grass availability, grazing behaviour, herbage intake, larval infection and weight gain was studied in 36 female calves of the Red Danish Milk breed. The age and the weight at the start of the trial were 6.2 months and 170 kg, respectively.
Six paddocks, two by two of equal size (1.10, 0.70, and 0.57 ha) were established during spring on an old pasture grazed by yearling heifers the previous year. One paddock of each size was grazed by 12 calves from mid-May to mid-July. The other three paddocks were harvested. In mid-July 6 calves from each paddock were moved to the comparable harvested paddock, and the other 6 calves remained in the original paddock.
At increasing stocking rate the growth rate decreased. There was no significant difference in grass production potential, but the herbage availability was decreasing at increasing stocking rate, and simultaneously the grass intake decreased, despite an increased parasitic Zoad as indicated by increasing serum pepsinogen at increasing stocking rate. This was correlated with scarcity of grass, forcing the animals to graze closer to the faecal pats (at high stocking rates).
These effects at increasing stocking rate were less pronounced in all three groups moved from the original to a harvested area in mid-July.
KeywordsGrazing Season Serum Pepsinogen Live Weight Gain Grass Production Larval Count
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