The timing of pasture allocation and grass silage supplementation affect pasture intake, milk production and nitrogen partitioning of dairy cows

Ignacio Beltrán,Nicolas Von Stillfried,Rubén G Pulido,Oscar Balocchi,Fernando Wittwer,Miguel Ruiz-Albarrán

doi:10.5424/sjar/2021192-16264

Abstract

Aim of study: To evaluate the effect of time of pasture allocation (PA) and grass silage allocations on dry matter (DM) intake, grazing behaviour, milk production, rumen function and N partitioning of grazing dairy cows.Area of study: Valdivia, ChileMaterial and methods: Forty-five Holstein-Friesian cows were selected from the Austral Agricultural Research Station at the Universidad Austral de Chile. Cows were allocated to one of three treatments: MPA: 75% of PA and 25% of the silage allowance allocated in the morning; BPA: 50% of PA and silage allowance allocated in the morning; APA: 25% of the PA and 75% of the silage allowance allocated in the morning. All treatments received the complement of pasture and silage allowance in the afternoon. Cows received a daily PA of 21 kg dry DM, 3 kg DM of grass silage and 3.5 kg DM of concentrate.Main results: Grazing time was not affected by treatments, however, grazing time between afternoon-morning milking was longer for APA. DM intake and milk production were not modified by treatments, averaging 15.6 kg DM/cow and 22.7 kg milk/d, respectively. Rumen propionate was greater for BPA than APA (18.8 and 17.7 mmol/100 mol, respectively). N intake and N excretion throughout milk, urine and feces were not modified by treatments, averaging 458, 119, 195 and 144 g N/d, respectively.Research highlights: The combination of time of pasture and grass silage allocation is not an adequate strategy to modify pasture intake, milk production and N excretion in dairy cows.

Highlights

As in most temperate climates, the predominant dairy systems are those that base their feeding on permanent pastures used mainly by grazing during the spring, summer, and autumn, because they are more cost effective than indoor system based on concentrate feeding (Dillon et al, 2005)
Forty-five multiparous autumn calving Holstein-Friesian cows, including three rumen cannulated cows (milk production 24.5 ± 3.5 kg/d, body weight (BW) 516 ± 71 kg and days in milk 57.3 ± 10.4) were randomly allocated to one of three treatments: 1) MPA: 75% of the daily strip-pasture and 25% of the silage allowance were assigned in the morning; 2) BPA: 50% of the daily strip-pasture and 50% of the daily allowance were assigned in the morning; 3) APA: 25% of the daily strip-pasture and 75% of the daily silage allowance were assigned in the morning
Pasture water-soluble carbohydrates (WSC) intake tended to be greater for APA than other treatments (p=0.1)

Summary

Introduction

As in most temperate climates, the predominant dairy systems are those that base their feeding on permanent pastures used mainly by grazing during the spring, summer, and autumn, because they are more cost effective than indoor system based on concentrate feeding (Dillon et al, 2005). Supplementation of dairy cows on pasture is a strategy to improve milk production in response to increasing total DM intake (DMI), supplying energy and protein at appropriate concentrations to cover animal requirements (Bargo et al, 2003). Grass silage supplementation is amply used during the autumn season in Southern Chile to cover pasture deficit and maintain a high DMI and milk production (Morales et al, 2014; Ruiz-Albarrán et al, 2016). The most important grazing bout in the day (morning and afternoon) can be modified by strategic supplementation at these times and thereby, pasture DMI, milk production (Sheahan et al, 2013; Al-Marashdeh et al, 2016b) and nutrient flow throughout day can be modified (Gregorini et al, 2010). There is not a consensus as to its effect on pasture DMI, grazing behavior and milk production (Sheahan et al, 2013; Al-Marashdeh et al, 2016a; Mattiauda et al, 2018)

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