Post-weaning growth of cattle in northern New South Wales - 1. Grazing value of temperate perennial pasture grazed by cattle

This paper describes the botanical components, seasonal herbage mass, and n utritive value of pastures used for post-weaning growth of CRC cattle at Gl en Innes before their progression to subsequent finishing and meat quality studies. The pastures under study comprised introduced temperate perennial species (tall fescue, Festuca arundinacea; phalaris, Phalaris aquatica; per ennial ryegrass, Lolium perenne; cocksfoot, Dactylis glomerata; white clove r, Trifolium repens; and red clover, Trifolium pratense) grazed by yearling cattle and managed according to local practice to maintain herbage mass be tween pre-determined limits. The study took place on 3 adjacent pasture sys tems (P1, pasture only; P2, pasture plus formulated pellets fed in later wi nter-early spring; P3, pasture plus forage crop grazed in later winter-earl y spring) over the 3 years 1994-96 that included a severe 20-month drought event followed by a drought-recovery phase. Results are discussed in the co ntext of the pasture feed year which was shown to comprise 3 distinct phase s: (i) spring primary growth phase, high availability of green herbage mass (2500-4500 kg DM/ha) of very high digestibility (0.80-0.85) and very high N status (about 30 g N/kg DM); (ii) summer-autumn secondary regrowth, high availability of green herbage mass (2500-4000 kg DM/ha) but with only moder ate nutritive value (0.65-0.70 digestibility, 15-20 g N/kg DM); and (iii) w inter dormancy, low availability of green herbage mass (750-1500 kg DM/ha) but with high nutritive value (0.75-0.80 digestibility, 20-30 g N/kg DM). I t was concluded that the limitations of the feed year for yearling cattle i n this environment include a feed gap in winter-early spring due to low her bage mass associated with winter cold and a feed gap in summer-autumn assoc iated with moderate nutritive value of secondary regrowth pasture.