Contribution of diet type and pasture conditions to the influence of high altitude grazing on intake, performance and composition and renneting properties of the milk of cows

Abstract

-Individual factors contributing to the influence of high altitude grazing on milk synthesis and quality were investigated in three groups of six cows each. After an initial period, where all cows received a silage-concentrate control diet, two groups were offered only grass further on, the third received the control diet and stayed in the barn in the lowlands. Grass-fed cows were either kept on pasture or in barn and were subjected to four experimental periods, two of them at 400 m a.s.l. and two at 2000 m a.s.l. Young and mature swards were grazed consecutively at each altitude. In the lowlands, feeding grass instead of the control diet did not clearly affect intake and performance but increased dietary N conversion ratio into milk protein and casein number. Relative to the control, rennet coagulation properties of the milk were improved on pasture but not with grass fed in barn. At the alpine site, nutrient and energy intake was depressed during the entire alpine period, presumably because of a combination of decrease in intake related to hypoxia and lower digestibility of the grass. Indications for elevated maintenance energy requirements caused by high altitude and, less so, by grazing activity were found. Compared to lowland, milk yield, milk protein content and N utilisation were lower at high altitude. Curd firmness was impaired by high altitude grazing at unchanged rennet coagulation time. The effects of grass maturity remained low at both altitudes despite contrasting digestibilities measured in young and mature swards. The plasminogen-derived activity in the milk declined with increasing sward maturity and with altitude, while plasmin activity was increased by sward maturity. Overall, diet type (control vs. alpine grass) and hypoxia-related factors seem to be more important for the expression of the known effects of alpine summer grazing than grazing activity as such and maturity of the sward. dairy cows / hypoxia / milk protein / plasmin / cheese Résumé -Contribution du type de ration et de la maturité des fourrages à l'influence d'un séjour au pâturage à haute altitude sur les quantités d'aliments ingérées, la quantité de lait produite et sa composition ainsi que ses propriétés de coagulation chez les vaches laitières. Les

Effects of species-diverse high-alpine forage on in vitro ruminal fermentation when used as donor cow's feed or directly incubated

“…Similar observations on alpine forage quality have been made in other studies (e.g. Leiber et al, 2006). In the present investigation, there was a minor increase with time on the alpine pasture, and also some interactions with forage type occurred.…”

“…Leiber et al, 2006). Compared with lowland herbages, alpine pastures have a higher diversity in plant species, especially herbs, and are supposed to be richer in plant secondary compounds (PSC) than intensively managed lowland pastures (Jeangros et al, 1999;Jayanegara et al, 2011a).…”

“…- E-mail: michael.kreuzer@inw.agrl.ethz.ch In addition to that, alpine pasture grass and hay are limited in their energy density and therefore may cause a shortage of energy for the rumen microbes (Leiber et al, 2006 andvan Dorland et al, 2006). These two properties were hypothesized to affect those rumen microbes that are involved in ruminal lipid metabolism and might explain the characteristic fatty acid profile of alpine milk (Leiber et al, 2005).…”

Transhumance of dairy cows to highland summer pastures interacts with breed to influence body condition, milk yield and quality

“…The effects of transhumance to summer farms on the nutritional status of animals and their milk production and quality are important issues, given that the milk is often processed into high-value products, yet so far they have been addressed in few experiments (Bovolenta et al 1998(Bovolenta et al , 2009Leiber et al 2006;Romanzin et al 2013;Farruggia et al 2014). When moved to summer pastures, cows experience a change in diet, an increased energy expenditure due to the movement associated with grazing, new interactions with unknown individuals in the case of mixed herds, and a general need to adapt to a different environment.…”

Colostrum and milk fatty acids of dairy cows as influenced by extruded linseed supplementation during the transition period

“…This may lead to body tissue mobilization (Leiber et al 2005(Leiber et al , 2006, which is expected from the study of Raclot (2003) to result in a preferable release of highly unsaturated FA compared with the saturated ones of the same chain-length.…”