ETD

• by-products
• lambs
• olive pomace
• sustainability

The use of agro-industrial by-products in ruminant feeding currently represents one of the most promising strategies to reduce production costs while simultaneously lowering the environmental footprint of livestock farming systems. The shift towards a circular economy is widely recognized in the literature as a key step to maximize positive outcomes and minimize negative impacts on land use, water resources, biodiversity, and climate. Nevertheless, despite its potential, the utilization of by-products is not without challenges, particularly due to their seasonal availability and the rapid deterioration for byproducts high in misture content, such as stoned olive pomace . To address these issues, ensiling is considered a practical and effective solution, as it stabilizes and preserves the nutritional value of fresh by-products.

Within this framework, a study was carried out on eighteen growing Appenninica lambs (average body weight 19.0 ± 2.0 kg) during the fattening phase. The animals were randomly assigned to three experimental groups of six subjects each, housed in individual pens, and fed ad libitum different diets. The first group (control, C) received a conventional fattening diet based on corn, barley, soybean meal, and grass hay. The second group (SD) was fed a diet including ensiled stoned olive pomace, wheat bran, sugar beet pulp, and distillers’ residues. The third group (SF) received a diet containing ensiled stoned olive pomace, wheat bran, sugar beet pulp, and faba beans.

Following a two-week adaptation period, data were collected for four weeks. Individual water intake and dry matter intake were recorded daily, while body weight was measured weekly. Statistical analysis was performed using a mixed linear model, with lambs nested within dietary treatments as random effects, and dietary treatment, period and their interaction as fixed effects.
The results showed that, at the end of the fattening phase, no significant differences were observed among groups with respect to final live weight, average daily gain, or average daily dry matter intake. However, lambs receiving diets containing ensiled stoned olive pomace tended to drink more water than those on the control diet (P = 0.001), and water intake per kilogram of dry matter intake was significantly higher (P < 0.05) in the SD and SF groups. This outcome was likely related to the higher polyphenol content of the diets including ensiled olive pomace.
Overall, the inclusion of ensiled stoned olive pomace, in combination with other agro-industrial by-products rich in digestible fiber and protein, proved supported lamb growth performance similarly to the conventional starch-rich diet based on cereals and soybean meal. This suggests that the partial replacement of traditional feed ingredients with local by-products can be a valuable strategy not only to reduce feeding costs, but also to enhance the sustainability of lamb production systems.
In conclusion, the use of ensiled stoned olive pomace in the diet of growing lambs is an effective practice able to promote the circularity of livestock farming systems, to enhance local resources, and to contribute to reduce the overall environmental impact of meat production, although the associated increase in water consumption should be carefully considered.