Resumen

HERNANDEZ-LOPEZ, Carlos et al. Relationships between seasonality, body characteristics and leptin at the beginning of puberty in Bos taurus taurus and Bos taurus indicus heifers in the Mexican tropics. Rev. mex. de cienc. pecuarias [online]. 2021, vol.12, n.4, pp.1025-1044.  Epub 06-Jun-2022. ISSN 2448-6698.  https://doi.org/10.22319/rmcp.v12i4.5796.

The study analyzed, in two years, the effects of breed [Brahman (BHM; n= 65); Braunvieh (BR; n= 56)], supplementation with Zilpaterol® (ZIL; treated or control), season of birth (spring or autumn) and their interactions on body surface (BS), age (APB), body weight (WPB), body condition (BC), long dorsal muscle (DM) depth, dorsal fat (DF) thickness and serum leptin concentration (LEP) at puberty (PB) of 121 heifers. At PB, BMHs were heavier and older than BRs (376.8 ± 7.4 vs 302.0 ± 6.6 kg; 588.1 ± 14.7 vs 445.5 ± 12.5 days). ZIL increased APB, WPB, BC and DM, but did not affect DF and LEP. BHMs had 18 % more BS than BRs. However, the difference in WPB/BS was only 6.4 %. When metabolic weight (MW) was used as a proportion of BS (MW/BS) instead of WPB, the difference between BHM and BR disappeared (P>0.05). The DF was 63.7 % higher in BHM than in BR. Those born in spring started PB with 24.4 % less DF than those born in autumn. Most of the BHM heifers (73.8 %) started PB in the months when light hours were increasing (P<0.05), while in BRs, the beginning of PB was uniformly distributed throughout the year, regardless of the length of light hours; this effect was present in the two years of study. It is concluded that the establishment of puberty is a multifactorial phenomenon; seasonality affects BHM and BR differently and, apparently, BS is an important factor, probably associated with efficiency in energy use. This paper reiterates the importance of dorsal fat and documents, for the first time, MW/BS and its association with the establishment of puberty.

Palabras llave : Puberty; Body surface; Seasonality; Tropical cattle; Leptin.

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