Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract only
Publication Acceptance Date: 3/18/2004
Publication Date: 7/25/2004
Citation: Connor, E.E., Rius, A.G., Auchtung, T.L., Wood, D.L., Kendall, P.E., Dahl, G.E., Capuco, A.V. 2004. Long days do not alter mammary growth in prepubertal heifers [abstract]. Journal of Animal Science Supplement. 82(Suppl. 1): 206. Interpretive Summary:
Technical Abstract: Effects of photoperiod on growth and development have been demonstrated in many species. In cattle, long-day photoperiod reduces the age at puberty, increases growth rate and increases milk yield in lactating cows. Reported effects on prepubertal mammary growth are inconsistent. Discrepancies may be the result of separate influences of photoperiod on rate of mammary growth and duration of allometric mammary growth, which terminates peripubertally. Our objective was to evaluate mammary growth after exposure to long-day (16L:8D) or short-day (8L:16D) photoperiods during the prepubertal phase of mammary growth. Calves approximately 3 mo of age were assigned to short- or long-day photoperiods. Three calves were killed prior to treatment and 4 heifers per group were killed after 2 or 4 months of treatment (5 or 7 months of age). Photoperiod did not affect the mass of mammary parenchyma or mammary fat pad (P > 0.05), although both increased with age (P < 0.05). Similarly, total parenchymal DNA and parenchymal lipid content were unaffected by photoperiod (P > 0.05). These data indicate that mammary growth is not influenced by manipulation of day length during the prepubertal period.