Weight gain of free-ranging beef cattle grazing in the boreal forest of south-eastern Norway

Morten Tofastrud,Anna Hessle,Yngve Rekdal,Barbara Zimmermann

doi:10.1016/j.livsci.2020.103955

Abstract

Young forest stands and clearcuts in the boreal forest created by modern forestry practices along with meadows of abandoned summer farms may contribute as feeding areas for beef cattle. The patchy distribution and varying quality and diversity of forage on such unimproved lands may affect cattle productivity. Weight gain of 336 beef cows and 270 calves free-ranging during three summer grazing seasons was monitored in boreal forests of south-eastern Norway, stocked at either high (0.16 cows ha-1) and low (0.04 cows ha-1) stocking densities. We used linear mixed effect models for assessing intrinsic correlates of weight gain in cows and calves in the two areas. Habitat use and home range size of a subsample of 53 cows were monitored by using GPS collars programmed to log locations at 5 min. intervals during the grazing season. Additional extrinsic correlates of weight gain for the subsampled cows using a linear mixed model were also tested.Average weight gain of beef cows grazing at the low stocking density was positive among cows of early maturing breeds (represented by Hereford) gaining 24 ± 2.8 kg (± SE), while cows of late maturing breeds (mainly represented by Charolais) had an average weight loss of 9 ± 8.4 kg. The average weight gain was negative for beef cows of both early (Herefords) and late maturing breeds (mainly represented by Charolais but also Limousin and Simmental) at the high stocking density. Within both breed groups, there was a negative relationship between breed-specific average weight of cows at turnout and weight gain during the grazing period, while a prolonged grazing period was slightly positively related to weight gain. There was no relationship between weight gain and home range size and proportion of grazing habitat for the 53 cows fitted with GPS collars.Higher weight gains in calves of the low compared to the high stocking density area was found. However, there was no breed effect of weight gain in calves. Across study areas, spring-born suckler calves gained more weight than autumn-born calves (92 ± 1.7 kg vs. 65 ± 4.4 kg). Also, there were higher weight gains for spring-born bull-calves than spring-born heifers (100 ± 2.4 kg vs. 94 ± 2.2 kg).Overall, the results indicate that it is possible to achieve acceptable weight gains for cattle grazing coniferous forest by finding breeds suitable for these extensive areas and stocking at moderate densities.

Highlights

Human population growth is causing an increase in demand for food that is not expected to be met by maximizing agricultural productivity on arable land alone (Godfray et al, 2010)
Cattle grazing has been associated with damage to young trees by trampling and bedding in areas of regeneration (Hjeljord et al, 2014; Kaufmann et al, 2017) whilst, cattle productivity may be impacted by the forest's heterogeneous environment with a patchy distribution of herbage and quickly declining quality and quantity of forage plants through the grazing season (Garmo, 1986)
The last major research on cattle grazing in boreal forests was performed in the 1950s and focused on cows and heifers of dairy breeds (Bjor and Graffer, 1963). To fill this knowledge gap, we studied the performance of cows and calves of different beef cattle breeds in free-ranging herds in the boreal forests of south-eastern Norway during summer

Summary

Introduction

Human population growth is causing an increase in demand for food that is not expected to be met by maximizing agricultural productivity on arable land alone (Godfray et al, 2010). Sustainable food production should be increased by utilizing natural environments at individual sites and managing resources in a way that benefits biodiversity, ecosystems services, agricultural production and other multiple purposes (Broom et al, 2013). Cattle grazing in forests are utilizing resources that otherwise could not be used as food and are a valuable contribution to global meat and milk production while decreasing the pressure on arable land (Schader et al, 2015). To assess the sustainability of such grazing regimes in this semi-natural environment, it is important to measure the productivity of cattle in relation to breed and stocking density

Methods

Results

Discussion

Conclusion