Herbage intake and behavioural adaptation of grazing dairy cows by restricting time at pasture under two feeding regimes

Abstract

The time at pasture of dairy cows is often restricted in the context of extending the grazing season in autumn or at the end of winter. The objective of our study was to evaluate the effects of a restriction of time at pasture on milk production, herbage intake and feeding behaviour in dairy cows according to feeding regime. The four treatments consisted of 4 h or 8 h of time at pasture per day tested under two feeding regimes combining rate of supplementation and herbage allowance: either a high rate of supplementation (10 kg dry matter (DM) of a maize silage-soya bean meal mixture in the ratio 87 : 13 on a % DM basis) with a low herbage allowance (6 kg DM/cow per day above 5 cm), or a low rate of supplementation (5 kg DM of the same supplement) with a high herbage allowance (11 kg DM/cow per day). The study was carried out according to a 4 × 4 Latin square design with four 2-week periods, with 48 mid-lactation Holstein cows. The cows in the 4-h treatment had access to pasture from 0900 h to 1300 h and those in the 8-h treatment from 0900 h to 1700 h. The supplement was given at 1830 h. When time at pasture was reduced from 8 h to 4 h per day, herbage intake decreased (9.9 v. 8.1 kg DM, P < 0.001), along with a fall in milk production (22.3 v. 21.2 kg, P < 0.001) and milk protein concentration (30.1 v. 29.6 g/kg, P < 0.001), while milk fat concentration increased (39.4 v. 39.9 g/kg, P < 0.05). The effect of time at pasture on milk production was slightly more marked on the low-supplement feeding regime (interaction P < 0.06). Reducing time at pasture by 4 h led to a sharp decrease in grazing time (327 v. 209 min, P < 0.001), but strongly increased the pasture intake rate (31 v. 39 g DM/min, P < 0.001) and the proportion of time spent grazing (0.68 v. 0.87, P < 0.001). Cows showed a stronger motivation for grazing when receiving the low-supplement feeding regime. In conclusion, we showed that reducing time at pasture from 8 to 4 h for cows receiving 5 to 10 kg DM of a maize silage-based supplement decreased moderately milk production and herbage intake, because of the capacity for behavioural adaptation by the grazing dairy cows.

N-alkanes v. ytterbium/faecal index as two methods for estimating herbage intake of dairy cows fed on diets differing in the herbage : maize silage ratio and feeding level

“…In our study, a highly irregular feeding pattern distribution was deliberately chosen between treatments, herbage being fed in the morning and silage in the evening, with a widely variable amount and thus morning : evening proportions. This feeding pattern is probably close to that of dairy cows grazing during the day and supplemented indoors at night (Pé rez-Ramírez et al, 2008). It is clear that the n-alkanes method is suitable for accurately estimating herbage intake by a twice-daily faecal sampling under very different feeding patterns, type of diet and feeding level.…”

Differential response to stocking rates and feeding by two genotypes of Holstein-Friesian cows in a pasture-based automatic milking system

“…Previous studies showed that cows were able to adjust the grazing behavior at pasture in response to PMR supplementation and/or duration of scheduled pasture allocations (Bargo et al, 2002). Cows increasingly restricted to graze at pasture generally increase the proportion of time spent grazing and/or the intake per bite, two compensatory strategies that maximize the instantaneous intake rate (Pérez-Ramírez et al, 2008;Kennedy et al, 2011). Conversely, increasing silage supplementation on same restricted cows can reduce grazing time and/or the proportion of time spent grazing (Pérez-Ramírez et al, 2008;Kennedy et al, 2011).…”

“…Cows increasingly restricted to graze at pasture generally increase the proportion of time spent grazing and/or the intake per bite, two compensatory strategies that maximize the instantaneous intake rate (Pérez-Ramírez et al, 2008;Kennedy et al, 2011). Conversely, increasing silage supplementation on same restricted cows can reduce grazing time and/or the proportion of time spent grazing (Pérez-Ramírez et al, 2008;Kennedy et al, 2011). Thus, cows of the present study may have adjusted the duration and/or intensity of grazing in response to PMR supplementation and available opportunities to access pasture on a voluntary basis.…”

Milk production, grazing behavior and nutritional status of dairy cows grazing two herbage allowances during winter

“…In the autumn system, extending the grazing season through winter until the beginning of spring provides a useful means of increasing the proportion of grazed herbage in the diet of dairy cows, reducing production cost (Pérez-Ramírez et al, 2008).…”