16 HOURS PHOTOPERIOD IN HOLSTEIN HEIFERS IN THE SUBTROPICS: EFFECTS IN DEVELOPMENT AND AGE TO FIRST ESTRUS

Nicolás Valenzuela-Jiménez, Karla Rodríguez-Hernández, Joel Hernández-Cerón, Héctor Vera-Ávila, Gregorio Núñez-Hernández, Alejandro Villa-Godoy

Abstract


Both growth and milk production in heifer calves are stimulated by a long photoperiod, though this has not been proven yet in subtropical areas. To evaluate the effect of 16 hr of light (L16) on calves suckling (LAC) and/or pre-pubertal stages (PP) in a subtropical area, 325 calves (36 ± 0.4 kg) were randomized into two groups: L16 or natural photoperiod (LNAT). At seven months of age, 198 of these calves (195 ± 2 kg) were randomly assigned to L16 or LNAT. The following were determined at the beginning and end of LAC and PP stages: Weight (PC, kg), height (AC, cm), thickness of back-fat (GG, cm) and of Longissimus dorsi (LD, cm); pelvic area (AP, cm2), body condition (CC), age at first estrus, mammary gland depth (PGM, cm) and width (AGM, cm). The statistical analysis was made using ANOVA for a 2 X 2 factorial arrangement. At the end of LAC, GG was lower and LD greater in L16 animals, while, at the end of PP, L16 heifer calves had a greater PC (260 ± 3 vs 250 ± 3), AP (166 ± 1.2 vs 153 ± 1.2), LD (3.18 ± 0.04 vs 2.90 ± 0.04), and AGM (2.41 ± 0.02 vs 2.21 ± 0.02), but a lower GG (0.114 ± 0.003 vs 0.139 ± 0.003) as compared to LNAT heifer calves. More L16 animals (67 %) presented estrus versus LNAT (38 %)

Keywords


Photoperiod; development; heifers calvez; estrus; subtropical;



DOI: http://dx.doi.org/10.19136/era.a2n4.717

ECOSISTEMAS Y RECURSOS AGROPECUARIOS(ECOSYSTEMS AND AGRICULTURAL RESOURCES), Year 6, Issue 16, January-April 2019, is a triannual journal edited, published and distributed by the Universidad Juárez Autónoma de Tabasco, Av. Universidad s/n, Zona de la Cultura, Col. Magisterial, Villahermosa, Centro, Tabasco, CP. 86040, Tel (993) 358 15 00, www.ujat.mx, era@ujat.mx., era@ujat.mx. Editor-in-chief: Efraín de la Cruz Lázaro. Copyright No. 04-2013-120514213600-203, ISSN: 2007-901X, both granted by the Instituto Nacional del Derecho de Autor (National Institute of Copyright), with certificate of title and content No. 16540 granted by the Secretaría de Gobernación(Ministry of the Interior). Individual responsible for the last update of this issue was journal Editorial Assistant Lic. Misael Hernández Martínez, Av. Universidad s/n, Zona de la Cultura, Col. Magisterial, Vhsa, Centro, Tabasco, Mex. C.P. 86040; date of last modification, December 31, 2018.

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