How over conditioning influences bull fertility

– Pedro Fontes, Ph.D. Assistant Professor, Georgia Extension Specialist

Consider the implications of sire over conditioning on semen quality and fertility.

Sire over-conditioning is a common phenotype observed in the beef industry. Pre- and post-weaning growth are important for profitability; therefore, as an industry, we are interested in identifying bulls with superior genetics for weaning and yearling weights. Nevertheless, young bulls are often not only fed high-energy diets to express their genetic potential at the time of yearling weight collection but also fed these diets to “look good” at sale time. Several Extension programs and bull development stations across the U.S. have reported the general preference of bull buyers for bulls with high rates of average daily gain (ADG) during their growth and development phase. In fact, bull buyers prioritize growth-related traits versus feed efficiency traits such as feed-to-gain ratio (F:G) or residual feed intake (RFI; Oosthuizen et al., 2018).

Another factor that encourages seedstock producers to increase energy intake during sire development is the effect of these dietary strategies on pubertal development. Similar to what has been thoroughly shown in heifers, sires that are exposed to high-energy diets achieve puberty earlier (Cardoso et al., 2018.; Kenny and Byrne, 2018). Yet, most bulls . . .

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