Performance and meat quality of suckling calves grazing cultivated pasture or free range in mountain

Abstract

The purpose of this study was to compare the effect of grazing on mountain (M) versus cultivated lowland pasture (C) on the performance and meat quality of suckling calves (Experiments 1 and 2). In addition, the effect of finishing on C after M on growth and meat quality was assessed (Experiment 2). Animals on C and M had on average similar live weight gain and carcass weight in the first experiment. However, the performance depended on year as gain and carcass weight was higher on C than on M in the first year and vice versa in the second year. In the second experiment the calves on M had lower gain and carcass weight than on C. Three weeks finishing on C after M compensated to some extent for the lower growth rate on M. Overall, the results indicate that mountain grazing may yield similar growth rates and slaughter weights as improved lowland pasture depending on year. There were only small effects of pasture type on carcass and meat quality traits like conformation, fatness, intramuscular fat and protein content, and fatty acid (FA) composition. The variation in FA composition could to a large extent be explained by difference in fatness with increase in monounsaturated and decrease in polyunsaturated FA with increasing intramuscular fat content, in turn varying between pasture type, experiment and year. There was a tendency that M led to higher proportion of C18:1n-9 and lower proportion of C18:1n-7 than C, which may be due to difference in milk and forage intake. Both pasture types resulted in meat with intramuscular fat with high nutritional value since the n-6/n-3 ratio was low.

Introduction

Historically, cattle was the most important domestic animal species, in terms of feed intake and production, used for free-ranging forest and mountain grazing in Norway (Lunden, 2002). However, during the second half of the 20th century, cattle's share of total free range grazing livestock, calculated as metabolic biomass, dropped from 56% (61.2 kg/km²) in 1949 to 20% (9.4 kg/km²) in 1999 (Austrheim et al., 2008). The contribution of sheep to the grazing biomass increased from 35% to 77% during the same period. Locally, cattle-grazing in forests and mountains is still practised, and the interest in more specialized beef production and niche marketing is increasing. Forest and mountain grazing may be economically attractive due to low feed costs and public support. These subsidies intend to stimulate the utilization of forests and mountains as pasture resources and maintain the valued aesthetics of cultural landscapes (Stortingsmelding nr.19, 1999). Previous research with steers and bulls in Norway has shown on average 56% less live weight gain on mountain than on lowland pastures (Gravir, 1962). Grazing cattle on forest and mountain pastures was still common when Gravir (1962) conducted his study, and the stocking rate of domestic animals in mountains was generally much higher than today. Little is known about the performance of cattle in mountain areas nowadays.

Production of pasture-based calf meat has no tradition in Norway. In areas with access to forests or mountains suitable for grazing, lowland grassland can to some extent be spared from summer grazing and used for winter forage production. The winter forage supply and the number of cows can thereby be increased to produce more offspring if the calves are slaughtered at the end or shortly after the end of mountain grazing period. Another advantage of slaughtering the calves in autumn after one season on pasture is that the cost of housing is significantly lowered compared with the traditional Norwegian system of indoor feeding for one (bulls) or two winters (steers). If meat from calves produced on mountain pasture is of a different quality (e.g. better nutritional value) than meat from calves grazing on lowland pasture, niche marketing may be possible; this in turn may generate a higher price. Meat fatty acid (FA) composition is a specific quality characteristic that is affected by diet and has been extensively studied due to its implication for human health (Scollan et al., 2006). Compared to feeding concentrates, grazing results in higher proportions of n-3 polyunsaturated fatty acids (PUFA), particularly C18:3n-3, and conjugated linoleic acid (CLA), increased PUFA:saturated fatty acid (SFA) ratio (P:S ratio) and decreased n-6:n-3 FA ratio in intramuscular fat (French et al., 2000, Poulson et al., 2004, Nuernberg et al., 2005). This is because fresh pasture is a rich source of C18:3n-3 (Dewhurst et al., 2001, Boufaied et al., 2003). Grazing also enhances the contents of other compounds regarded as beneficial in meat, like carotene and tocopherol, which may improve the shelf life of meat (Simonne et al., 1996, Daly et al., 1999, Yang et al., 2002). However, little is known about the effect of pasture type, e.g. botanical composition, on meat quality. It has been found that cow's milk produced on high altitude grassland has higher content of C18:3n-3 than milk produced on lowland pastures; this has been explained by reduced ruminal biohydrogenation of feed 18:3n-3 (Leiber et al., 2005), likely caused by properties of certain plant species (Collomb et al., 2002). Lambs finished on mountain pasture in Norway had more PUFA than comparable lambs grazing on cultivated lowland pastures (Adnoy et al., 2005). Steers grazing semi-natural grassland in UK had a lower proportion of C16:0 and a higher proportion of PUFA than steers grazing improved permanent pasture (Fraser et al., 2009). These studies indicate that there could be a pasture type effect on meat quality. It is known that both diet forage proportion (French et al., 2000) and length of time on pasture (Noci et al., 2005) affect the composition of fatty acids. Finishing on improved grassland after mountain grazing could also alter meat quality as there is change in forage composition, but the effects need to be studied and quantified.

The objectives of this study were to investigate 1) the effect of forest and mountain free range grazing on growth, and on carcass and meat quality of suckling calves and 2) whether finishing on lowland pasture after mountain grazing affects the meat quality.