Nutrition, Growth, and Age at Puberty in Heifers.

Simple Summary: Age at puberty is a main factor affecting reproductive efficiency and, thus, livestock production. Besides species and breed, nutrition during growth plays a crucial role in the attainment of puberty. Controversial results are reported about the critical period during which heifers are more sensitive to the effects of nutrition on pubertal acceleration. Numerous papers are available about such topics, but they are characterized by very different experimental conditions (such as genetics, feeds, planes of nutrition, season and pasture quality, time windows, and parameters considered), making difficult the comparison among inconstant results by various trials. Several indicators during growth have been proposed as predictors of age at puberty, such as body weight gains, body fat reserves, and linear body measurements. Blood concentrations of hormones strictly linked to growth and reproduction have also been considered: higher Insulin-like Growth Factor-1 levels are reported to be related to earlier puberty, while leptin is not. More uniform experimental conditions should be encouraged for future research. Puberty onset and age at first calving have a critical impact on livestock production for good reproductive efficiency of the herd and to reduce the duration of the non-productive stage of the growing heifer. Besides genetic factors, sexual maturation is also affected by environmental factors, such as nutrition, which can account for up to 20% of the observed variability. The rate of body weight gain during growth is considered the main variable influencing the age at puberty, dependent on planes of nutrition in growing animals during the prepubertal-to-pregnancy stage. This paper reviews current knowledge concerning nutrition management and attainment of puberty in heifers, considering the relevance of some indicators such as body measurements and hormones strictly linked to the growth and puberty process. Puberty onset is dependent on the acquisition of adequate subcutaneous adipose tissue mass, as it is the main source of the hormone leptin. Until a certain level, body condition score and age at puberty are negatively correlated, but beyond that, for fatter animals, such correlation is gradually lost. Age at puberty in heifers was reported to be negatively related to IGF-1. Future research should be planned considering the need to standardize the experimental animals and conditions. [ABSTRACT FROM AUTHOR]