Ministerio de Ciencia e Innovación (España), Agencia Estatal de Investigación (España), European Commission, Toral, Pablo G. [0000-0002-1913-7707], Frutos, Pilar [0000-0002-4919-5094], Hervás, Gonzalo [0000-0002-0013-7459], Barrio, Esther [0000-0003-0714-1407], Barrio, Esther, Hervás, Gonzalo, Gindri, Marcelo, Friggens, Nicholas C., Toral, Pablo G., Frutos, Pilar, Ministerio de Ciencia e Innovación (España), Agencia Estatal de Investigación (España), European Commission, Toral, Pablo G. [0000-0002-1913-7707], Frutos, Pilar [0000-0002-4919-5094], Hervás, Gonzalo [0000-0002-0013-7459], Barrio, Esther [0000-0003-0714-1407], Barrio, Esther, Hervás, Gonzalo, Gindri, Marcelo, Friggens, Nicholas C., Toral, Pablo G., and Frutos, Pilar
In the current scenario of climate change and economic instability, it can be expected that livestock will increasingly face nutrition-related challenges. Resilience (understood as the ability of an animal to revert quickly to high production and health status in response to a perturbation) would therefore be of great importance. However, animal breeding is still focused on higher production or, at best, higher feed efficiency (FE). Yet, it is uncertain whether improving FE could detrimentally affect resilience, particularly in small dairy ruminants. This experiment was carried out to examine the relationship between resilience and FE; namely, to compare the variation in some blood metabolites in dairy ewes phenotypically divergent for FE and subjected to an acute nutritional challenge. First, to estimate FE, we used 40 Assaf ewes fed a TMR ad libitum, and measured individual dry matter intake and milk yield daily over 3 weeks. Feed efficiency was calculated as the difference between the actual and predicted intake estimated through net energy requirements for maintenance, production and weight change. Then, after selecting two groups of FE ewes: higher (H-FE; n = 9) and lower (L-FE; n = 9) efficient ewes, they were subjected to a nutritional challenge. The trial consisted of three periods: the pre-challenge (when animals were fed TMR ad libitum), the challenge (lasting for 3 days, when the TMR was withdrawn and the ewes were only fed wheat straw) and the post-challenge (lasting for 10 days, when animals were fed again TMR ad libitum). At the end of each period, blood samples were collected (before milking and feed administration) and the serum was analyzed for glucose, non-esterified fatty acids (NEFA) and b-hydroxybutyrate (BHB) concentrations during the trial. The data were subjected to repeated measurements analysis, with animals nested within the group. The results showed that glucose levels tended to be marginally greater in H-FE than L-FE (P = 0.058), and dro