Management considerations in heifer development and puberty

Abstract

Management of replacement beef heifers should focus on factors that enhance physiological processes that promote puberty. Age at puberty is important as a production trait when heifers are bred to calve as 2-yr-olds and in systems that impose restricted breeding periods. Calving by 24 mo of age is necessary to obtain maximum lifetime productivity. Because the reproductive system is the last major organ system to mature, factors that influence puberty are critical. The influence of environment on the sequence of events leading to puberty in the heifer is dictated largely by the nutritional status of the animal and related effects on growth rate and development. Management strategies have been designed to ensure that heifers reach a prebreeding target weight that supports optimum reproductive performance, and consequences of inadequate or excessive development have been evaluated. Those strategies are based on evidence linking postweaning nutritional development with key reproductive events that include age at puberty and first breeding, conception, pregnancy loss, incidence and severity of dystocia, and postpartum interval to estrus. Management alternatives that ultimately affect lifetime productivity and reproductive performance of heifers begin at birth and include decisions that involve growth-promoting implants, creep-feeding, breed type and(or) species, birth date and weaning weight, social interaction, sire selection, and exogenous hormonal treatments to synchronize or induce estrus. Basic and applied future research efforts should converge to match in a realistic manner the production potential of the animal with available resources. Strategies that incorporate consideration of nutrition, genetics, and emerging management techniques will need to be tested to enable producers to make decisions that result in profit. This review evaluates the current status of knowledge relating to management of the replacement beef heifer and serves to stimulate research needed to enhance management techniques to ensure puberty at an optimal age.

Development and reproductive performance of Hereford heifers of different frame sizes up to mating at 14-15 months of age

“…Patterson et al (1992) emphasized the importance of pre-weaning weight gain for puberty onset, considering the harmful effects of poor nutrition on puberty described by Short and Bellows (1971). In the study of Bittencourt et al (2005), the body weight of 14 to 15-month-old heifers in the beginning of the breeding season explained 73.6% of the variation in pregnancy probability and an optimal body weight of 338.8 kg was determined.…”

Estimativa de la edad y peso a la primera monta de novillas en el Pantanal brasileño

“…El peso corporal influencia el aparecimiento del 1 o celo (Patterson et al, 1992), siendo que las novillas deben alcanzar 60% del peso corporal adulto cerca de 60 días antes de entrar en la estación de monta considerando que la fertilidad de las novillas aumenta después del 3 o ó 4 o celos (Kasari & Gleason, 1996). Sin embargo, Faria (1996) demostró que novillas Nelore y productos de cruzamientos industriales tienen edad media a la cubrición fértil a los 24 meses con peso medio de 350 kg, siendo que animales superprecoces, que son…”

Bioeconomic factors of beef heifer maturity to consider when establishing criteria to optimally select and/or retain herd replacements

“…Two systems used to indicate breeding readiness (defined here as maturity), measured by the MI proposed by Stockton et al (2013) and the TW approach as outlined by Patterson et al (1992), are tested as predictors of dystocia. This comparison is a step forward in building a systems model to determine the bioeconomic optimal maturity of heifers.…”

“…Their index values proved to be less than statistically significant. More recently, work by Patterson et al (1992) using target weight (TW) has become a widely accepted method to forecast maturity and initiate heifer breeding. Using the same metric, Feuz (1991) developed a profit function.…”