-Alkanes are digesta markers for use as a research tool giving the opportunity to estimate feed intake and digestibility in vivo. The development of intra-ruminal controlled-release capsules (CRC) offers a practical method of dosing even-chain alkanes and may give less diurnal variability of marker excretion improving the validity of grab-faecal sampling. This was tested in the present study by total faeces collection in four cows for 7 days. Dry matter intake was 10.4 kg forages and 10.4 kg concentrate (diet 1) and 15.1 kg forage (diet 2). The recovery (proportion of dosed or dietary alkane intake found in faeces) of C 31 was lower than that of C 32 and consequently underestimated intake. C 33 and C 32 had similar recoveries giving accurate intake estimates from pooled samples from total daily faecal collections and also from grab samples taken at 6.30 a.m. The study confirms that a single injection for gas chromatography is sufficient. Alkane CRC are concluded to be an accurate method for estimating forage intake of cows consuming diets with or without concentrate when spot sampling of faeces is conducted over 7 days and only moderately less precise when sampling over 5 days.alkane / controlled-release capsule / feed intake / forage / cow Résumé -Précision de l'ingestion estimée par des capsules à libération contrôlée d'alcanes chez les vaches à partir d'échantillons de fèces. Les alcanes sont en passe de devenir des marqueurs prometteurs, en tant qu'outil pour estimer l'ingestion in vivo. Des alcanes à chaînes paires administrés dans le rumen sont comparés à des alcanes à chaînes impaires naturellement présents dans la cire cuticulaire des végétaux ingérés par le ruminant. Le développement de capsules intra-ruminales à libé-ration contrôlée (CRC) facilite la distribution à l'animal d'alcanes à chaînes paires et pourrait ainsi diminuer la variation journalière de l'excrétion du marqueur en augmentant la validité des échantillons de fèces. C'est ce qui a été testé ici, en récoltant en totalité les excrétions fécales de 4 vaches pendant une semaine. Les quantités ingérées étaient de 10,4 kg de MS pour le fourrage et de 10,4 kg de MS Ann. Zootech. 49 (2000) 3-13 3

In each of 2 years (years A and B), the effects of three nutritional regimes were examined using 12 cows kept at pasture for 77 days at 2000 m above sea level. Two supplement formulations (1 and 2) were designed, both equally high in readily fermentable energy (14·6 MJ metabolizable energy (ME) per kg dry matter (DM)) but differing in crude protein content (53 and 193 g/kg DM). The treatments imposed were either pasture grass alone (control groups; both seasons) or grass and supplements provided at three levels relative to energy (E) and protein (P) maintenance requirements estimated for lowland conditions. These levels were (i) 1·0 E: 0·8 P provided by 4·6 kg of supplement 1 per day in both years; (ii) 0·5 E: 0·4 P provided by 2·2 kg of supplement 1 per day in year A; (iii) 1·0 E: 2·5 P provided by 4·4 kg of supplement 2 per day in year B. Intensive measurement periods, including food intake estimation by the double alkane technique, were carried out in weeks 3, 7 and 11 on Alpine pasture. Performance data, plasma levels of indicative blood traits and body condition were additionally monitored in the cows at a lowland site for 2 weeks prior to transport. Supplementing with a high energy/low protein concentrate gave no clear benefit in milk yield, which declined proportionately by 0·33 in the 11 weeks under Alpine conditions. Provision of additional supplementary protein (supplement 2) resulted in a proportionate decline in milk yield of only 0·20 over the 11-week period. Cows exhibited high substitution ratios of 1·4 to 2·6 kg herbage DM per kg concentrate DM and cows on all treatments were estimated to consume similar amounts of ME. A combination of reduced fibre intake and lower fibre digestibility with supplementation significantly reduced milk fat contents to low levels. Energy supplementation significantly reduced plasma β-hydroxybutyrate levels. However, live-weight and body tissue loss rates (based on ultrasonic scans of subcutaneous fat layer and longissimus dorsi muscle) were equally great with and without energy supplementation but less severe with extra protein (supplement 2). Adaptation to the high Alpine conditions was achieved in all treatments as indicated by increased blood haemoglobin, accompanied by a lower plasma level of insulin-like growth factor-I. Plasma thyroid hormone levels suggested that adaptation to energy deficiency and possibly to cold was more effective with supplementary energy. Other energy-dependent blood metabolites and insulin responded similarly in all treatments to high altitude grazing. Estimated maintenance energy requirement for Alpine conditions was 0·72 times greater than lowland maintenance requirement.

SU MMARYNutrient intake, digestibility and live-weight changes were compared for groups of grazing cattle on two Swiss Alpine pastures in different regions (R1 and R2 ; both >1500 m above sea level) during 2 years (1997 and 1998). The R1 site was an improved pasture, while R2 was an unimproved pasture of poor nutritional quality. Replicated over 2 years, R1 groups comprised four Scottish Highland suckler cows together with their calves and four Brown Swiss dairy cows (17 . 8 kg/day milk) kept at high stocking rates (approx. 7 cows/ha) in short rotations (intensive management system). R2 groups comprised four Highland cows with calves managed at low density (approx. 0 . 4 cows/ha) and setstocked (extensive management system). Grazing seasons lasted 77 days at R1 and 127 days at R2. Intake, digestibility and faecal excretion were estimated by the slow-release alkane indicator method. Average dry matter intakes in kg/day and g/kg W 0 . 75 /day (in parentheses) were 17 . 4 (151) for dairy cows at R1 and, significantly lower, 12 . 7 (133) and 11 . 1 (111) for beef cows at R1 and R2, respectively. Herbage dry-matter intake of calves was 1 . 2 kg/day at both locations. Calf weight gains measured over 77 days (0 . 69 kg/day) were similar at the two sites and thereafter declined only slightly at R2. The N content of the herbage selected was similar in the two regions, but in other respects the herbage at R2 was of significantly poorer nutritive quality as indicated by the lower digestibility of organic matter and neutral detergent fibre at R2 compared with R1. Through feed selection, nutrient intake by beef cows was sufficient to gain weight. In contrast, dairy cows at R1 lost on average more than 50 kg of weight. Calculations were made and discussed regarding N utilization and urinary N loss, and measured faecal N and mineral excretion to allow a quantitative assessment of nutrient returns to the sward. We conclude that Highland beef cattle make poorer use of improved Alpine pasture than dairy cows though they utilize pastures of poor nutritive quality under extensive management without loss of productivity.

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Jewell P.L., Güsewell S., Berry N.R., Käuferle D., Kreuzer M. and Edwards P.J. 2005. Vegetation patterns maintained by cattle grazing on a degraded mountain pasture. Bot. In southern Switzerland the use of mountain pastures for cattle has been in decline since the 19th century, promoting the dominance of unpalatable grasses and shrubs. In an attempt to improve pasture quality, 80 Scottish Highland cattle were introduced to a 73-ha grazing area on acidic soils at 1400-1800 m a.s.l. To assess how this management might affect the vegetation, we surveyed the plant species composition, soil chemistry and spatial patterns of cattle grazing. Large parts of the pasture were low-productive Nardetum grassland or Callunetum heathland. Patches of more productive and nutrient-rich grassland occurred on less acidic soils with higher total P concentration and lower C:N, C:P and N:P ratios. Grazing by cattle focused on these patches, while N. stricta grasslands and heathlands were hardly used. Historical evidence suggests that these patterns of cattle use are similar to those in the past. We conclude that the current grazing regime is unlikely to produce a significant change in vegetation composition and pasture quality.