Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: March 18, 2004
Publication Date: July 25, 2004
Citation: Rius, A.G., Kendall, P.E., Auchtung, T.L., Capuco, A.V., Connor, E.E., Dahl, G.E. 2004. Long days that hasten puberty do not reduce lean body growth in heifers. Abstract. Joint Abstracts of the American Dairy Science and Society of Animal Science, p. 500.
Photoperiod affects growth and development in many species with long day photoperiod (LDPP; 16L:8D) hastening the onset of puberty and enhancing lean growth in cattle. Appropriate body scale is crucial in heifers at first parturition. However, accelerating prepubertal growth may diminish mammary parenchymal growth. Nutritional factors including metabolizable protein also affect the onset of puberty, body and mammary growth in heifers. Our objective was to determine if LDPP hastens the onset of puberty without limiting lean growth. We also sought to determine if the response to LDPP is limited by protein availability. Holstein heifers (n = 32) were assigned to 1 of 4 treatments in a CRD and a 2x2 factorial arrangement to assess the photoperiodic and dietary bypass protein effect on the onset of puberty and body growth. Treatments were LDPP, short day photoperiod (SDPP; 8L:16D), high or low dietary bypass protein. Blood samples were analyzed for PRL concentration to evaluate a photoperiodic response and for progesterone to determine puberty. Body weight (BW), withers height (WH), hip height (HH), and heart girth (HG) were measured every two weeks. After puberty, heifers were housed under natural photoperiod and body measurements were continued to evaluate body growth postpubertally. Heifers exposed to LDPP reached puberty 20 days earlier (P< 0.02) relative to animals on SDPP. Increasing a dietary bypass protein did not affect growth of heifers (BW, WH, HH or HG) on either photoperiod treatment. However, heifers previously exposed to SDPP gained 22 kg more (P< 0.05) of BW after puberty than did heifers previously exposed to LDPP. These data support the use of photoperiod as a non-invasive technique to hasten puberty without limiting lean growth and development in heifers.