Precocity, efficiency and resilience of suckler cows Dossier: Feed efficiency of beef cattle

Abstract

In the current economic and environmental context, suckler cattle production is regularly questioned. Precocity (as a means of reducing non-productive periods), feed efficiency and resilience have become of primary importance. To explore these traits and their relationships, a large experimental design was implemented between 2011 and 2021 on the INRAE experimental farms of Bourges and Le Pin-au-Haras. This experiment consisted of three successive parts that the same animals underwent: sexual and growth precocity, feed efficiency using residual feed intake at around two years of age and a feed restriction challenge during lactation. In this article, we sum up the main results obtained from this experiment. Although precocity was largely under the control of environmental factors (management, diet…), and especially the season of birth, a moderate heritability was observed (0.21 ± 0.08). This trait was also genetically correlated to small birth weight and high pre-weaning growth rate. Feed efficiency of two-year old individuals was less heritable (0.09 ± 0.08), but favourably correlated to precocity. When facing feed restriction, lactating cows show a balanced response with a decrease in milk production and a body reserve mobilization of similar intensity. However, this average response hides an important inter-individual variability. A negative influence of heifer feed efficiency on cow milk production was identified (up to – 0.7 kg of milk in middle lactation, which correspond to about 10 % less), with an additional negative effect on cyclicity resumption in case of dietary restriction. These results highlight the importance of considering efficiency on a long-term scale and not only growth feed efficiency in genetic selection.