Metabolic response of early-lactating cows exposed to transport and high altitude grazing conditions

Abstract

AbstractThe metabolic response of dairy cows to high as opposed to low altitude conditions (2000 m v. 400 m above sea level) was determined. In the first experiment, four cows were subjected to a series of measurements before, during and after transport from lowland to high altitude pasture. During transport, cortisol, l-lactate and non-esterified fatty acids were significantly elevated but decreased within 1 to 3 days to initial levels. After transport, β-hydroxybutyrate and the thyroid hormones immediately increased and returned within 3 weeks to initial levels. Plasma urea increased during transport and subsequently was at an intermediate level due to the different diet. There were no direct carry-over effects of transport on metabolic traits during pasturing.In the second experiment, three groups of six different dairy cows were either grazed in one of two consecutive years or kept inside (2nd year only). Lowland sojourn lasted for 4 weeks, and high altitude period for 8 weeks. At the end of high altitude sojourn, both outside and inside groups were found still to have significantly higher plasma cortisol values than at lowland. Thyroid hormones and ketosis related metabolites sharply increased at the start of the alpine period and were elevated for 1 to 3 weeks thereafter. According to the hormonal and metabolic profiles, the permanently housed cows did not benefit from the less adverse climatic conditions and the lower physical strain. Plasma urea closely reflected dietary changes in the ratio of nitrogen to fermentable organic matter. Plasma protein, albumin, creatinine, and liver enzyme activities were not affected by transport or high altitude sojourn in both experiments. The results indicate that the metabolic response to transport and high altitude conditions can be mostly explained by the efforts to cover the additional energy requirements. Overall the data suggest a wide but nevertheless limited ability of early-lactating cows to adapt to high altitude conditions.