The effect of two contrasting grazing managements and level of concentrate supplementation on the performance of grazing dairy cows

Abstract

-The grazing management of dairy cows is characterised by practices that vary greatly in terms of stocking rate, nitrogen fertilisation and supplementation. The objective of this 6-year experiment was to establish the response by dairy cows to increasing amounts of concentrate supplement under two contrasted rotational grazing systems. Each year, 30 cows were assigned to a Severe grazing system aimed at maximising milk production per hectare with high annual nitrogen input (280 kg N·ha -1 ) and a high stocking rate. Another 30 cows were assigned to a Lax grazing system characterised by a lower input (120 kg N·ha -1 ) and stocking rate aimed at offering a greater quantity of grass per animal per day. From 1995 to 1997, four moderate levels of concentrate supplementation (0, 1.4, 2.8 and 4.0 kg) adjusted according to the milk yield of the cows at turnout were compared. From 1998 to 2000, higher quantities of concentrate (0, 2, 4 and 6 kg) maintained at a flat rate between cows were compared. The Lax grazing system led to a 0.8 to 1.0 kg increase in milk yield (P < 0.0001) per cow per day without any significant modification of milk fat and milk protein content, compared to the Severe grazing system. Compared with the Severe treatment, the Lax treatment reduced cow grazing days by 160 days per ha and milk production by 3225 kg per ha. In both systems, concentrate supplementation made it possible to increase milk yield, with an efficiency of close to 1 kg of milk per kg of concentrate, as well as increasing milk protein content and live weight gain. The milk fat content decreased only in the last three years of the experiment, following an increased concentrate supplementation. All these animal responses remained linear up to the maximum amount of concentrate offered; there was no variation between cows supplemented with the same concentrate level. This multi-annual experiment confirms the importance of making the best possible use of herbage produced by adapting the stocking rate to achieve a post grazing sward height of 5 to 6 cm during the grazing season. With an increased genetic potential of the dairy herd, high individual cow performance at grazing can be attained by the use of concentrate supplementation. dairy cows / grazing management / supplementation / milk production 437 * Corresponding author: luc.delaby@rennes.inra.fr Anim. Res. 52 (2003) 437-460  INRA, EDP Sciences, 2003 DOI: 10.1051/animres:2003030Résumé -Effets des conditions de pâturage et de l'apport de concentré sur les performances des vaches laitières. L'alimentation des vaches laitières au pâturage se caractérise par une grande diversité des pratiques à la fois en terme de chargement, de fertilisation azotée et de complémentation. L'objectif de cette expérience pluriannuelle est de décrire la réponse des vaches laitières à l'apport de doses croissantes de concentré dans deux situations contrastées de pâturage. Chaque année, la moitié des 60 vaches utilisées a été affectée soit à un scénario Severe visant à maximiser les performances...

Effect of increasing pasture allowance and concentrate supplementation on animal performance and microbial protein synthesis in dairy cows

“…The lack of effect of supplementation with concentrate on grazing time could be explained by a social effect, where Phillips (1993) suggests that supplementation also affects non-supplemented cows in cases where they were grazing together, such as decreasing their grazing time or, the intake speed in supplemented cows. Although Delaby et al (2003) agree with this study, a considerable number of authors (Pulido and Leaver 2001, Bargo et al 2003 show decreasing grazing times under conditions of generous pasture availability in spring. The bite rate was not affected by supplementation with concentrate, just like in the reports of Bargo et al (2002) but opposed to that of Pulido and Leaver (2001).…”

Effect of different feeding strategies on lactation performance of Holstein and Normande dairy cows

“…6 UFL: energy feed unit equivalent to 1700 kcal of net energy for lactation. Feeding strategies and dairy cows' performance 893 rotational grazing system (Hoden et al, 1991;Delaby and Peyraud, 2003) based on three to four plots in spring and extended to seven plots in autumn. During each rotation, the same total area was allocated to the two groups to obtain the same average stocking rate of 4.0 cows/ha in spring and 2.2 cows/ha in autumn.…”

“…On the grazed paddocks, the biomass before grazing as well as the sward density (expressed in kg DM/cm per ha) was measured by motor scythe cutting during each rotation according to the methodology specified by Delaby and Peyraud (2003). The sward heights before and after grazing, or after topping, were determined using a plate meter by performing 150 measurements per hectare.…”

“…At pasture, the quantities of herbage removed were estimated from the differences in sward heights measured before and after grazing on the plots, and the sward density measured on each plot according to the methodology suggested by Delaby and Peyraud (2003).…”

Development and evaluation of the herd dynamic milk model with focus on the individual cow component

“…The shape of the equations (6) and (7) has been generated to take into account the fact that the responses are linked to the potential of the animal and to the available energy. Those equations have been validated based on external data from INRA in Le Pin (Delaby et al, 2003;Delaby et al, 2009).…”