امیر موسائی

The transition period poses a considerable metabolic challenge for dairy ruminants, primarily due to the heightened energy requirements. This study aimed to assess the effects of varying energy intake (EI) levels on the performance and metabolic status of fat-tailed sheep. A total of 24 single-bearing pregnant ewes were randomly assigned to three experimental groups with eight replications each: (1) a control group with EI in accordance with their estimated energy requirements (CON); (2) a group receiving approximately 60% of the CON intake (0.6CON) and (3) a group provided with 120% of the CON intake (1.2CON). The experimental period spanned from 2 weeks prior to parturition to 2 weeks following parturition. The findings indicated that the 0.6CON group exhibited significantly lower intake levels of metabolizable energy (ME), neutral detergent fibre (NDF) and non fibre carbohydrates (NFC) compared to the other groups (p < 0.05). Additionally, the energy restriction (ER) resulted in a notable reduction in the body weight of ewes at lambing and on postpartum days 7 and 14 (p < 0.05). It is important to highlight that milk production ranged from 660 to 1500 g/day, demonstrating a significant difference between the ER group and those provided with higher energy levels. In addition, the EI had a pronounced positive impact on the production of fat (FCM), energy (ECM) and total solids (TSCM)-corrected milk (p < 0.05). Furthermore, the 0.6CON group showed diminished yields of fat, protein, lactose and solid non-fat (SNF) (p < 0.05), whereas the 1.2CON group displayed enhanced production efficiency (p < 0.05). The ER resulted in a significant reduction in blood glucose and phosphorus levels, while concurrently causing an increase in urea and non-esterified fatty acids (NEFA) concentrations (p < 0.05). However, no significant effects were observed on circulating levels of triglycerides, cholesterol, aspartate transaminase, alanine transaminase, calcium, total protein, globulin or β-hydroxybutyric acid (BHBA). It can be concluded that EI during the transition period has a substantial impact on the lactation performance and metabolic status of fat-tailed ewes.