Administration of olive leaves in the sheep ration improves milk yield for the production of a cheese with exceptional nutritional qualities. The discovery is the result of a recent study carried out by the Special Animal Husbandry research unit of the Department of Agricultural, Food and Environmental Sciences at the University of Perugia. (1)
Long live by-products
The ruminant category (whose main bred representatives are cattle, sheep and goats) has physiological characteristics particularly suitable for the use of by-products derived from agro-industry.
Indeed, ruminants are able to convert fiber sources unsuitable for human consumption into products with high nutritional value, such as meat and milk (2).
The use of by-products can reduce waste management costs, environmental impact and the cost of animal diets, while also improving animal welfare (3).
The study
Olive leaves are suitable for supplementation in the diet of ruminants (sheep, in this case), as well as a source of polyphenols, vitamins and unsaturated fatty acids. The Perugia researchers’ study focused on incorporating this byproduct into the diet of pasture-raised sheep.
The animals, 20 divided into two homogeneous groups, were allowed daytime access to the pasture. The first group was fed a commercial pelleted feed at milking, while the experimental group was given a feed in which 28 percent dried olive leaves had been supplemented.
A cheese was made from the milk produced by the sheep, which was then aged for 60 days. Chemical and sensory analyses were conducted on the cheese, which produced particularly interesting results.
Promising results
Milk yield to cheese increased for the group whose feed was supplemented with dried olive leaves, as a result of the higher protein and fat content.
Regarding the latter component, quality is a key aspect and one that affects human health. The fat composition of the two cheeses was different.
Less saturated fat
Cheese made from milk obtained from animals that received olive leaf supplementation showed a lower percentage of saturated fatty acids.
Certain saturated fatty acids are known to increase the risk of cardiovascular disease, and these are precisely those that were present in lower percentages in the experimental cheese.
In contrast, monounsaturated fatty acids, including oleic acid (characteristic of olive oil), were higher in cheese made from the milk of leaf-fed animals.
Several polyunsaturated fatty acids also showed the same trend, with particular reference to those in the omega-3 series, which are known for their positive effects.
Consequently, the indices related to thrombogenicity and atherogenicity (related to cardiovascular risks) of experimental cheese were lower than those of conventional cheese.
Antioxidant action
Antioxidant capacity was also found to be better for cheese derived from the group of sheep fed olive leaves.
This can present an advantage both for the consumer, who benefits from metabolically available compounds, and for the product, which is defended against the oxidizing action to which polyunsaturated fatty acids are particularly prone, thus improving its shelf-life.
Some bioactive compounds from the olive leaves were then successfully transferred to the cheese, arriving directly on the consumer’s plate.
The panel‘s appreciation
The panel test performed on the cheeses revealed that consumers are aware of the high residual value of olive leaves and tend to attribute added value to them even when used unconventionally.
After a ‘blind’ tasting, in fact, no significant differences had been found in the panel‘s appreciation of the two types of cheese. In contrast, once the differences in the diet provided to the two groups of animals were revealed, the tasters showed greater appreciation for the cheese derived from the olive leaf diet.
This finding could also be directly related to an idea of greater sustainability: consumers value the use of by-products rather than food based solely on raw materials that compete with human food and require additional space and resources to obtain.
Innovation in tradition
In Mediterranean areas, historically devoted to olive and sheep farming, this study could have considerable impact and practical utility, fostering the competitiveness of more sustainable livestock farming conducted in marginal areas and enabling the reduction of feed-to-food competition.
The needs of the modern consumer require more attention from producers and the market in general, and evaluating more “traditional” than “conventional” alternatives could have an interesting economic implication, reducing the food costs of farms on the one hand and increasing the willingness to pay of buyers on the other.
Conclusions
In conclusion, increased consumer and producer awareness can provide a higher quality, healthier product that is economically, environmentally and animal welfare sustainable: information and communication is the best approach to achieve these common goals.
Consumers are increasingly attentive to the quality and sustainability of the products they consume, and animal products are even more subject to the buyer’s critical eye. It is critical that research accompanies new food market needs to provide information to support smart production as sustainable and quality. Recent geopolitical events, moreover, have led to an alarming increase in the cost of grains and soybeans for the livestock sector, which conventionally bases its productions on concentrated feeds derived from these raw materials.
Notes
(1) V. Bolletta, M. Pauselli, C. Pomente, A. Natalello, L. Morbidini, G. Veneziani, V. Granese, B. Valenti, Dietary olive leaves improve the quality and the consumer preferences of a model sheep cheese, International Dairy Journal, Volume 134 (2022)
(2) A. Natalello, A. Priolo, B. Valenti, M. Codini, S. Mattioli, M. Pauselli, et al., Dietary pomegranate by-product improves oxidative stability of lamb meat, Meat Science, 162 (2020), Article 108037
(3) A. Campione, M. Pauselli, A. Natalello, B. Valenti, C. Pomente, M. Avondo, et al., Inclusion of cocoa by-product in the diet of dairy sheep: Effect on the fatty acid profile of ruminal content and on the composition of milk and cheese, Animal, 15 (2021) https://doi.org/10.1016/j.animal.2021.100243
PhD candidate at the University of Perugia
