Species-rich swards of the Alps: constraints and opportunities for dairy production

The swards of the alpine grasslands represent a unique feed resource that sustains animal agriculture to the present. The complex animal–plant interactions during cattle grazing influence grassland dynamics, which under proper grazing management maintain the sustainability of these alpine swards and thereby the persistence of alpine dairy production systems. However, dairy production on alpine swards is limited by the herbage quality and the physiological impact of alpine summer grazing on dairy cattle. Abandonment of the alpine regions and shifts from milk production towards more extensive livestock systems are trends increasingly seen during recent decades. Current interest in the positive health aspects of animal products, especially in beneficial functional fatty acids in milk, may revive the interest in alpine dairy farming, because high concentrations of beneficial functional fatty acids in the lipid fraction of the milk are found in dairy products of alpine origi

Body composition of cows kept under tropical conditions: Carry-over effects of feed fluctuation

Knowledge of composition of fat, protein and water in the body is indicative for the determination of effects of changes in nutrition in terms of body reserves. Deuterium oxide dilution technique has been proposed as easy, reliable and non-destructive method of determining body composition using the ratios of protein:water and mineral:water to predict fat. Twenty Bos indicus (Boran) and 21 Boran × Holstein have been exposed for 4 years to calculated energy requirements for maintenance (M) (low) or M + 20% (medium) and M + 40% (high). In the third lactation these treatments were sub-divided into either low or high feeding level. Before deuterium application animals were weighed and a blood sample was collected from the jugular vein. Deuterium was slowly administered at 0.3 g/kg fasted body weight, directly into the jugular vein and the syringe was rinsed with refilled blood. Blood samples were taken at 5, 7, and 9 h post infusion and deuterium concentrations in plasma were analysed using isotope mass spectroscopy (3960 nm against water). The gastrointestinal tract (GIT) of the cows was assumed to amount to 0.20 of body weight (BW), and empty body weight (EBW) was described as EBW = BW − GIT. Body composition was estimated in the following equations: Empty body water (kg) = 0.4717 × BW (kg) + 0.1536 × D 2 O-space (kg) – 25.046 Empty body ash (kg) = 0.0363 × BW (kg) + 0.0231 × D 2 O-space (kg) – 5.755 Empty body protein (kg) = 0.1624 × BW (kg) + 0.0165 × D 2 O-space (kg) – 11.488 Empty body fat (kg) = 0.3790 × BW (kg) – 0.2955 × D 2 O-space (kg) – 42.163 Previous feeding level and the genotype explained most of the differences between treat- ment groups. Boran cows showed higher levels of fat, but the difference of 20% and 40% of the previous medium and high treatment was still visible. Fat reserves from the cross- bred cows were strongly influenced by milk production, however, crossbreds previously on low plane of nutrition replenished their fat deposits instead of producing more milk when receiving higher amounts of feed

Evidence for different nutrient partitioning in Boran (Bos indicus) and Boran x Holstein cows when re-allocated from low to high or from high to low feeding level

This study tested the hypothesis that purebred Boran (Bos indicus) cows and crossbreds of Boran and Holstein respond differently to long-term changes of feeding level in nutrient partitioning to milk and body fat stores. A total of 27 cows of these two genotypes were subjected either to a low or a high feeding level from their first oestrus as heifers until birth of their third calf. Half of the cows of each genotype were then switched to the other feeding level during the third reproduction cycle. If at all, Boran cows responded to a change in the feeding level almost exclusively by a corresponding change in body weight but not milk yield. Crossbred cows kept continuously on the low feeding level had a lower milk yield than those continuously fed the high level, but lost similar amounts of body weight. In crossbred cows, changing the feeding level from high to low was accompanied by a mobilization of body reserves, whereas a change from low to high level resulted mostly in an increase in milk yield. Certain other genotype differences in metabolic response were obvious from differences in body composition and from the metabolic profile either reflected in blood (particularly insulin-like growth factor I) or in adipose tissue (lipoprotein lipase). Reproductive performance differed between genotypes, with shorter lactations associated with earlier occurrences of the first oestrus in the Boran cows. Generally, feeding history appeared to have at least as much influence on energy partitioning as the actual feeding level. In conclusion, purebred Boran cows seem to react to long-term food fluctuations mainly by mobilizing and restoring body fat reserves, whereas cows crossbred with Holstein tend to spend extra energy preferentially for milk productio