Interpretive Summary: Performance and milk fatty acid profile of beef cows with a different energy status with short nutrient restriction and refeeding

By: Karina G Orquera-Arguero, Mireia Blanco, Juan R Bertolín, Javier Ferrer, Isabel Casasús

Lactating cows can undergo periods with a negative energy balance due to feed shortages, which trigger metabolic adaptations to support cow maintenance and milk yield. We explored beef cows’ response to a short feed restriction (4 d, 55% of their energy and protein requirements) and subsequent refeeding (4 d, 100% of their energy and protein requirements) in the second month of lactation. We analyzed the effect on their performance and metabolism by placing special emphasis on milk production and milk fatty acid composition in two beef cow groups with a different nutritional status before the challenge. When cows faced a food restriction, both groups had similar changes in productive and metabolic traits. These changes are similar to those occurring in restricted dairy cows, but of lesser magnitude due to the lower milk yield and associated metabolic load of beef cows. The milk fatty acid profile, rarely analyzed in beef cows, proved to be an accurate indicator of their metabolic status.