Limitations of high Alpine grazing conditions for early-lactation cows: effects of energy and protein supplementation

Abstract

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.

Nutrient and energy conversion of grass-fed dairy and suckler beef cattle kept indoors and on high altitude pasture

“…The results of this CRC test, performed within experiment II and following the principles outlined by Berry et al [2], confirmed its applicability, particularly when based on early-morning faecal samples [in line with 2,19] and on the C 31 :C 32 ratio. Berry et al [2] noted a slightly higher accuracy with the C 33 :C 32 ratio, but subsequently variability between cows was found to be higher than with the C 31 :C 32 ratio [3], as was also true for the present investigation. Furthermore, as in other studies [24,29], the C 33 alkane content of lowland grass was lower than 50 mg·kg -1 considered as threshold value for the use of n-alkanes as marker.…”

“…This study supplements a previous one comparing extremes on the same alpine pasture, namely early-lactating cows and a slow-growing beef breed [40], which were either underfed (dairy) or poorly utilising the feed resources (beef). As expected from the lower level of performance, the average herbage DMI of 16 kg·d -1 (dairy cows) was slightly lower than that found previously in early-lactating dairy cows on the same high-altitude pasture [3,8]. As beef cows had a clearly lower estimated milk yield, their lower intake compared to the dairy cows is reasonable.…”

“…Spot faeces samples were collected rectally or from fresh dungpats at dawn over the 7 days of the measurement period. Handplucked herbage samples were collected by animal category daily for 12 h by two people following and mimicking cow and calf selection from one day prior to the start, to one day before the end of faecal sampling, as suggested by Berry et al [3]. Half of the herbage collected during the sampling period and additional samples taken randomly on the experimental pasture from the standing sward were immediately separated for legume, herb and grass species, dried for 48 h at 60 °C and weighed after cooling.…”

“…Diets consisting exclusively of grass, as used in this study, are common for suckler beef feeding whereas dairy cows typically receive a certain amount of additional concentrate, except on high altitude pasture where supplementary feeding often cannot be practised and is of low efficiency to sustain a high level of performance [3,5]. Therefore, system comparisons are difficult to achieve on the basis of literature data, as the basic system effects cannot be separated from the diet effects.…”

“…The economic sustainability of utilisation of alpine pastures by suckler beef was evaluated by Cayla et al [7] and the farm benefit by Liénard et al [26]. Slow-release capsules containing n-alkanes now offer the opportunity to determine herbage and nutrient intake on pasture [3] although information on the accuracy of these capsules in cows and calves on grass-only diets is lacking. On basis of this technique, one study compared early-lactating dairy cows with extensive suckler beef systems on alpine pastures [40], and revealed clear system differences in productivity and nutrient excretion.…”