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COW AGE, RESILIENCE AND PRODUCTIVITY OF COW-CALF SYSTEMS

Amir Sessim, Tamara Oliveira, Gabriel Pereira, Fredy Lopez Gonzalez, Fabiana Maidana, Daniele Zago, Concepta McManus, Júlio Otávio Barcellos

Abstract

Context: The energy availability for cow-calf systems is related to climate disturbances, and its use is influenced by the age of the cows. Both factors determine the productivity and resilience of herds after climate disruption. Aims: Identify the time needed for the herds composed of cows of varying ages to achieve resilience, after energy restriction in the pre and postpartum. Methods: The resilience of systems was compared by deterministic dynamic simulation and were considered herds initially stable and differentiated by: A) energy availability for all herd in the first year of production at 50% (low, L), 75% (medium, M) and 100% (high, H) of the requirements according to the NRC (2006 and 2016), which was restricted to 60 days before and 60 days after birth; and B) the maximum age of the cull cow (lifetime, LT), considered at four (LT4L, LT4M, LT4H), six (LT6L, LT6M, LT6H) and eleven years (LT11L, LT11M, LT11H). From the second year, availability returned to meet the energy requirements of all animals. The availability of energy for the herd was simulated in natural and cultivated pasture. The productivity was determined as the relation between the kilograms of animals sold and the area used for production over a productive cycle. The system model was considered resilient when 95% of the standard productivity was reached (prior to energy restriction). Key results: the time required to return to stability was two years in the LT6 and LT11, while LT4 required three years. Furthermore, LT6 had higher productivity than other herds. The older the cow is culled, the greater the change in the composition of the product commercialized. Conclusions: Cows with an intermediate culling age allow a sustainable intensification of the system, as they show better productivity than older cull cows, furthermore, after climate disturbance, they present less resilience than younger cull cows. The level of energy restriction did not directly influence the time to resilience within each evaluated discard age group. Implications: Herds that culled females before reaching adult age are less resilient after disturbances such as changes in climate or of any nature that interfere with reproductive rates.

AN23419  Accepted 17 April 2024

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