Herbage production and animal performance on perennial ryegrass/white clover dairy pastures under alternative spring grazing managements

Abstract

Spring grazing managements which allowed some early inflorescence development, followed by hard grazing in order to remove the reproductive stems (designated ‘late control’), were compared with a conventional close grazing strategy (‘early control’) in three paddock-scale complete randomized block studies with dairy cows grazing perennial ryegrass/white clover pastures during consecutive years (1990–1993) in Palmerston North, New Zealand. Experiment 1 was designed to evaluate the timing of late control, Expt 2 to investigate the most suitable intensity of control, and Expt 3 tested different practical approaches to carrying out the late control management.Late control generated an average herbage production increase of 24% (750 kg DM/ha) in October and November (spring) and 22% (950 kg DM/ha) from January to April (summer–autumn) compared with the conventional management. The increase in herbage accumulation during spring was a consequence of greater perennial ryegrass reproductive development. Increased summer–autumn herbage accumulation after late control management was attributed to enhanced tillering activity and accumulation of perennial ryegrass. Effects on white clover production were inconsistent. Experiment 3 compared the effects of two practical late control strategies, involving either a short period of rapid rotational grazing or a simulation of increased stocking rate normally associated with forage conservation, on the milk production and forage intake of groups of cows in self-contained farmlet systems. During the control period, the reproductive state of the sward caused a small decrease in herbage digestibility. However, the extra herbage produced subsequently did not differ in digestibility from that produced on the conventionally managed sward and resulted in an increase of around 11·5% in total milk solids yield (fat, protein and lactose) per cow, particularly towards the end of the season (March and April).The late control spring grazing management strategy is a viable option for dairy farmers. It should coincide with the time of anthesis of ryegrass plants (late November–early December), and is more effectively achieved when forage conservation practices are used to augment grazing pressure in the grazed area of the farm.

Persistence of tall fescue in a subtropical environment: tiller survival over summer in response to flowering control and nitrogen supply

“…Unfortunately, few studies have reported tiller survival and production in temperate grasses – almost none in subtropical environments – which restricts the possibilities for comparisons. In temperate NZ, perennial ryegrass swards showed a high proportion of reproductive tillers (from 25% to 70%), a marked tiller population turnover at flowering, and an overall increase in total tiller density (Matthew et al ., ; Hernández‐Garay et al ., ; Bahmani et al ., ; Da Silva et al ., ), which is consistent with the reproductive perennation pathway being dominant. Although there is evidence that this may differ among cultivars (Bahmani et al ., ) and that tiller density can be manipulated through grazing (Thom, ; Hernández‐Garay et al ., ; Da Silva et al ., ), management appears to have little influence on the persistence strategy of perennial ryegrass (Korte, ; Matthew et al ., ).…”

“…In perennial ryegrass ( Lolium perenne L.) growing in temperate climates, the pathway of perennation has been described as ‘reproductive’ (Matthew et al ., ), which means that persistence relies on the production of daughter tillers from decapitated flowering tillers. The window of opportunity to remove flowering tillers – a management hereby referred to as ‘flowering control’ – ranges from the start of floral induction until anthesis (Korte et al ., ; L'Huillier, ; Da Silva et al ., ). A study conducted at the single tiller level by Matthew et al .…”

Effect of altering the grazing interval on growth and utilization of grass herbage and performance of dairy cows under rotational grazing

“…(1975) was of the same order as in this experiment (13·5 d), their long rotation was 27 d. Consequently, any impact of the reduction in herbage production on performance of cows with the short rotations would most likely have been negated in these two 3‐year studies by the reductions in herbage quality associated with the long regrowths imposed. Da Silva et al. (2004) compared shorter rotations (15 and 10 d) for 1 month with a standard rotation of 20 d, following a period of relatively lax grazing in the early part of the season, and found no difference in milk yield per cow.…”

Recent progress in the study of behavior and management in grazing cattle

“…As another operational rule, the initiation date which was the date when grazing started for a particular season, was very important (Da Silva et al . 2004).…”

“…As another operational rule, the initiation date which was the date when grazing started for a particular season, was very important (Da Silva et al 2004). Under rotational grazing systems, initiation date was shown to have a strong influence on annual herbage utilization ) and on milk production per unit area ).…”