Influence of fertiliser and grazing management on North Island moist hill country 5. Animal production

Abstract

The effects of low (LF) and high (HF) fertiliser and 3 grazing management treatments: rotational grazing with sheep (RGS) or cattle (RGC), and set stocking with sheep (SSS), on animal production from moist North Island hill country were studied for 7 years. Flock and herd sizes were large enough to detect important differences in reproductive performance, and farmlet sizes were sufficient to incorporate slope and aspect effects on pasture productivity. After 7 years the HF treatment farmlets carried 34.2% more sheep than LF at similar per head performance. In all years HF gave a higher wool yield/ha and a greater weaned lamb liveweight (LW)/ha as a result of the higher stocking rate and, in some years, an increased LW also. RGS supported 10.0 and 5.2% more sheep than SSS for the HF and LF treatments respectively, during the first 4 years of the experiment. In 1975-76 SSS gave an increase in weaned LW/ha as a result of increased lamb weaning weight. Grazing management had no effect on wool yield/ha. There was an increase of 2.22% lambs born and 1.59% lambs surviving to docking for each kg increase in April ewe LW over the range 47-57 kg. Lamb death rate from birth to docking was 15.3%. There were more deaths from dystocia and stillbirth on RGS treatments but fewer resulting from starvation-exposure. Increased superphosphate application gave higher animal production because of the increased sustainable stocking rate. Providing that the increase in stocking rate matched increased pasture production there was no decline in per animal performance. SSS gave equal or better animal production in both seasons and years when pasture growth rates exceeded animal requirements. RGS gave increased animal production when pasture growth rates were below animal requirements and animals had minimal body reserves.