The effects on pasture of the winter grazing of dry dairy cows : a thesis presented in partial fulfilment of the requirements for the degree for the degree of Master of Agricultural Science at Massey University
With the demand for higher production, but probably more from economic necessity, stocking rates on New Zealand dairy farms have increased markedly over the past ten years. The average herd size has over this period increased from 57 cows in 1960 to an estimated 98 cows in 1970 (N.Z. Dairy Board, 1970); this figure however takes no account of any increase in farm size over this period. Increased stocking rates on a fixed area of land has not been associated with similar increases in pasture production,indeed, the reverse may be the case (Campbell, 1966; Holmes, 1962; Morley 1966). The increased production has been a function of increased utilization of the pasture grown (Campbell, 1966). With such trends management decisions with regard to pasture and animal become critical, mistakes having long reaching repercussions, A critical period on all seasonal dairy farms is over the winter when management decisions can affect butterfat production for the entire lactation (Wallace 1958), Increased stocking rates have heightened this wintering period as a result of mainly two factors : (i) An increased milking herd means lower pasture surpluses in the spring, hence lower levels of conserved fodder for periods of low pasture production. (ii) It is at this time of the year that damage to pastures through grazing appears most severe.