Efficacy of Hormonal Growth Promoter Implants on the Performance of Grazing Steers of Different Breeds in Southern Chile

Abstract

Increasing demands for land is necessitating the optimisation of grazing land used for livestock production. Hormonal growth promoter implants (HGPI) are widely used to improve cattle performance and thus land-use efficiency. However, there is limited information on their efficacy in grazing systems. Forty grazing steers, 10 of each breed (Angus, Hereford, Holstein, Overo Colorado), had growth rates monitored for 85 days after which half received HGPI and half continued as a control. Growth rates were monitored for an additional 61 days and performance between the groups compared. Implants had a significant impact on liveweight gain (LWG; p = 0.013), and whilst breed did not (p = 0.65), there was an interaction effect of breed × treatment (p = 0.029). For three of the four breeds, the LWG was greater in the implant group (mean +14.3%). The exception was for Holstein steers which did not respond to the implant. In general, HGPI were found to be effective in increasing LWG of grazing cattle and thus has the potential to increase yield densities and relieve pressures of land use and competition. The efficacy may be affected by breed and other extraneous factors not covered in this study. Furthermore, the use of HGPI must be carefully considered in a wider context since its use might have secondary impacts.

Implantes promotores de crecimiento en ganado bovino. Efectos y rol en un escenario de mayor demanda y preocupación ambiental

“…Por su parte, Scheffler et al (2003), informaron una GDP superior en novillos Holstein que recibieron dos y tres IAPC, comparado con aquellos implantados una sola vez (120 mg TBA y 24 mg E2 por implante) en una engorda de 291 días. Rivero et al (2021), compararon la ganancia de peso vivo en novillos en etapa de recría-engorda, alimentados en base a pradera en el sur de Chile en distintas razas (Aberdeen Angus, Hereford, Holstein Friesian y Overo Colorado), usando un implante que contenía 40 mg TBA y 8 mg E2. Todas las razas, con la excepción de los Holstein, tuvieron una GDP superior al control en un 14,3%.…”