Groei en ontwikkeling van Friesverse

English: The purpose of this research project was to select which of the following grazing systems would result in the highest qrowth performance for Friesian heifers, i.e. 1 day grazing, 14 days rest (15 days system), 2 days grazing 28 days rest (30 days system) and 4 days grazing 56 days rest (60 days system). Holstein-Friesian heifers between the ages of 6 to 12 months were put on summer kikuyu pastures for two seasons, which included a wetter and drier year. The 15 day grazing system gave significantly better mass gains in both the drier and wetter years than the 30 day and 60 day grazing systems (P ≤ 0.01). In the drier year the only tendency shown was that the 30 day grazing system gave better live mass gains than the 60 day grazing system. Differences were not significant. In the wetter year the 30 day grazing system gave significantly higher mass gains compared to the 60 day grazing system (P ≤ 0.01). Results for shoulder height increases, udder size increases, teat length increases and teat diameter increases varied over the two seasons. In the wetter year the following results were found. The dry matter intake of the 15 day grazing system was significantly higher than that of the 60 day grazing system (P ≤ 0,01). Time spent grazing per day for the 60 day grazing system was significantly longer than the 15 day and 60 day grazing systems (P ≤ 0,01). Serum mineral profiles showed no shortages, as well as no significant differences between treatments. Disc meter data showed that enough food was available for the animals, but that no deductions could be made from this as to what the intake of the animals was. Crude fibre results showed no significant differences between treatments. The total nitrogen analysis showed that the protein content of the grazing on the 15 day cycle was significantly higher than that of the 30 day and 60 day cycle. The general conclusion reached was that short graze and short rest grazing systems on kikuyu would give higher mass gains for Friesian heifers between the ages of 6 to 12 months than longer grazing-rest systems. Supplementary feeding on these pastures is however necessary to obtain the necessary average daily gains.