Replacing the protein source of the diet of goats with Retama monosperma (L.) Boiss. seed: Effect on intake, digestibility, ruminal fermentation, and health status.

Abstract

Current strategies in animal nutrition aim to reduce reliance on conventional protein sources by promoting sustainable alternatives. Retama monosperma (L.) Boiss, an endemic shrub of the Iberian Peninsula and Morocco adapted to harsh dune environments, has been identified as a potential novel protein feed. However, its seeds contain high levels of quinolizidine alkaloids (QA), which may limit their nutritional use. This study evaluates the in vivo effects of partially replacing the conventional protein (peas) in the concentrate of goat diets with raw (20%) or heat-treated (80%) R. monosperma seeds on feed intake, nutrient digestibility, nitrogen and energy utilization, ruminal fermentation, microbial protein synthesis, and animal health. Additionally, various aqueous-thermal treatments (soaking for 24hours, drying at 50 °C-48 hours, and variations in the boiling duration and in the medium and leaching procedures) were evaluated to reduce QA content, with the most effective method selected for the feeding trial. The seeds showed a total QA concentration of 27,189mg/kg, with cytisine accounting for 99.2% of the total alkaloids. Detoxification efficiency varied among treatments, achieving QA reductions from 55.7% to 95.4%. The inclusion of retama seeds modified ruminal fermentation, increasing ammonia concentration and urinary purine derivatives, suggesting enhanced protein degradability and microbial protein synthesis. Nevertheless, no negative effects were observed on feed intake, apparent nutrient digestibility, nitrogen balance, or blood metabolic parameters. In conclusion, partial replacement of conventional protein sources with raw or heat-treated R. monosperma seeds appears feasible in moderate goat production systems without compromising animal performance or health.