Feeding walnut leaf and green tea ethanolic extracts enhances performance and improves plasma metabolites in fat-tailed ewes during the transition period

Abstract

The transition period in ewes, characterized by significant physiological changes, plays a critical role in determining the health and productivity of both the ewe and her offspring. This study explored the effects of leaf extracts of walnut (WLE) and green tea (GTE) on dry matter intake, colostrum and milk production, composition, and plasma metabolites in fat-tailed ewes in the transition period. Forty-eight fat-tailed Makui ewes (58 ± 1.2 kg body weight) were randomly assigned to four treatments (12 ewes per group): a control group (CON) receiving a basal diet and three experimental groups supplemented with 100 mg/kg body weight of WLE, GTE, or a combination (WL + GT), and the extracts were administered orally twice daily. Ewes fed the WL + GT combination had higher (P < 0.05) dry matter intake, body weight, and body condition score both pre- and post-partum than the other groups. The WL + GT ewes also exhibited lower plasma non-esterified fatty acids, reduced insulin levels post-partum, and lower liver enzyme concentrations (aspartate aminotransferase and alanine aminotransferase) versus CON ewes. Additionally, WL + GT supplementation reduced (P < 0.05) plasma monounsaturated fatty acids and increased polyunsaturated fatty acids and Omega-6 levels. Milk yield during the first week of lactation was highest in the WL + GT group, which also showed increased (P < 0.05) milk fat and lactose content. Furthermore, milk from supplemented ewes showed a higher concentration (P < 0.05) of polyunsaturated fatty acids, Omega-6, eicosapentaenoic acid, and docosahexaenoic acid in both WL + GT and WLE ewes than GTE and CON. These findings suggest that the supplementation of WLE and especially the combination of WL + GT positively influences feed intake, body weight, and milk production, while also enhancing the nutritional profile of the milk by increasing beneficial fatty acids such as eicosapentaenoic acid and docosahexaenoic acid. The improvements in metabolic health markers, including reduced (P < 0.05) non-esterified fatty acids and liver enzyme concentrations, indicate a potential role of these extracts in optimizing energy metabolism and reducing metabolic stress during the critical transition period, with potential benefits for sustainable dairy production. Further research is needed to fully elucidate the underlying mechanisms of these effects and their long-term implications for ewe and lamb health.