Alpine grasslands: relations among botanical and chemical variables affecting animal product quality
2016
Renna, M | Ravetto Enri, S | Probo, M | Lussiana, C | Malfatto, V | Battaglini, L M | Lonati, M | Lombardi, G
In alpine farms, forage composition is considered as the most important factor influencing the quali- ty of grazing ruminant productions. This study aimed at analysing the complex relationships existing among botanical composition, chemical composition and some plant community variables of different alpine grassland communities. Thirty-nine vegetation surveys were carried out within some of the most common alpine grass- land communities in the western Italian Alps. The botanical composition was determined, and mean values of Landolt’s ecological indicators, biodiversity indices, phenological stage, and pastoral values (PV) were com- puted. Representative samples of grass were collected and analysed for dry matter (DM), crude protein (CP), fibre, and fatty acid (FA) composition. The relationships among the considered variables were assessed com- puting Pearson’s correlation coefficients and performing a canonical correspondence analysis (CCA). A hierar- chical cluster analysis identified two main grassland ecological groups: (i) mesophilic grasslands (MG), including Poa pratensis, Lolium perenne and Festuca nigrescens types; and (ii) dry grasslands (DG), including Bromus erectus, Brachypodium rupestre and Helianthemum nummularium types. Independent sample t-tests showed that MG and DG were comparable (P greater than 0.05) in terms of phenology, biodiversity indices and proportion of botani- cal families. The CCA clearly separated MG and DG along the first axis (32.1% of explained variance): MG species were associated with higher CP, total FA, a-linolenic, linoleic and palmitic acids contents, while DG species were associated with higher DM, fibre and oleic acid contents. Interestingly, the PV (a synthetic vege- tation index) was strictly linked with the plant concentration of a-linolenic acid. These findings highlight that rumi- nants grazing on MG can benefit from forage of higher palatability, nutritive value and concentration of precur- sors for the synthesis of beneficial FA (e.g., rumenic acid and omega-3 fatty acids) in dairy and meat products
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