Short-, Medium- and Long-Term Metabolic Responses of Adult Meat Ewes Subjected to Nutritional and β-Adrenergic Challenges

Abstract

Shortage and refeeding situations lead to switches in metabolic pathways induced by undernutrition and body energy reserve (BR) replenishment cycles. In a 122-d experiment, 36 adult Merinos d’Arles ewes were chosen and first accustomed to diet ingredients (i.e., wheat straw, pelleted alfalfa and sugar beet pulp) and the facility environment for 22 d. Then, ewes were randomly assigned to one of three “diet challenge” treatments during 50 d, (control, underfed and overfed; 12 ewes each) corresponding to 100%, 70% or 160% of energy requirements allowances, respectively. Then, a “refeeding challenge” was applied the last 50 d (i.e., diets adjusted with the same ingredients). An individual monitoring of body weight (BW), body condition score (BCS) and energy metabolism was carried out. The last day, a “ß-adrenergic challenge” was applied. Anabolic or catabolic responses were accompanied by synchronized metabolic regulations, leading to contrasting metabolic and BR profiles. Average BW and BCS were higher and lower in overfed and underfed ewes, respectively, which was proportional to lower and higher BR mobilization dynamics. Higher plasma free fatty acids (FFA) were accompanied by lower blood insulin, leptin and glucose levels. After refeeding, a rebound in BW and BCS were observed, and FFA were drastically reduced in underfed ewes. No differences were detected in plasma FFA at the end of the study, but the lipolytic activity was different and contrasted with the adipose tissue mass.

Short-term responses of meat ewes facing an acute nutritional challenge in early-mid lactation

“…Temporal trends in BW, BCS, and plasma T3 were less sharp. This finding confirms the potential of the aforementioned parameters to be used as reliable biomarkers of the short-term responses of ruminants when facing acute undernutrition events ( Chilliard et al, 1998 ; Ingvarsten and Andersen, 2000 ; González-García et al, 2020a ). Direct effects were not reflected however in the shape of lambs’ BW and ADG curves ( Figure 4 ), demonstrating the capacity of these Romane ewes for responding to the acute CHA without affecting offspring performance in the short-term.…”

“…Temporal patterns in the postchallenge period (ability to revert to the initial status) were well described for DMI, DFT, and plasma NEFA, β-OHB, urea, and T3 which showed return to initial plateau around 4 to 5 d after finishing the CHA ( Figures 2 and 3 ; Supplementary Figures S1 to S11 ). The potential of NEFA, β-OHB, and T3 as good biomarkers of BR mobilization-accretion processes in sheep is well known and has been reported previously with meat and dairy ewes at La Fage with different rearing systems ( González-García et al, 2014 , 2015 ) and beyond (e.g., with Mérinos d’Arles meat ewes; González-García et al, 2020a ). Our results are in agreement with the results from Barrio et al (2023) who found DMI and milk yield values at a steady level of 5 d after the end of the CHA in dairy ewes.…”

“…Those related to the administration of energy body reserves ( BR ) in ruminants (i.e., efficient synchronization of BR mobilization-accretion processes) are well known, mainly in harsh environments ( Bocquier and González-García, 2010 ). Short-term responses include adjustments in intake, digestion, and metabolism ( Chilliard et al, 1998 , 2000 ; González-García et al, 2020a ).…”

Livestock grazing systems and sustainable development in the Mediterranean and Tropical areas

“…It is a component with a direct impact on the overall resilience of the herd under conditions where fluctuation in feed quantity and quality is one of the main constraints. A similar characterization of BR dynamics has been conducted with Arles Merino ewes subjected to varying energy balances (González-García et al, 2020a).…”