title: Effects of biostimulation and nutritional supplementation on pubertal age and pregnancy rates of Nelore heifers (Bos indicus) in a tropical environment.
abstract: To determine effects of biostimulation (BIO) and dietary supplementation (BIO+S) on pubertal age and pregnancy rates, Nelore heifers (n=392) were randomly assigned to one of four treatment groups (n=98/group). All animals were in tropical environmental conditions, in the middle-west region of Brazil, grazing in pastures of Brachiaria brizantha, cv. Marandu; Panicum Maximum, cv. Tanzânia and Brachiaria humidícula. The heifers of the BIO group were kept in the presence of bulls while being maintained on pasture; the animals in the BIO+S group were kept in the presence of bulls while being managed on pasture and were fed a diet with greater energy and protein content to produce 0.49 kg of BW gain/day; the animals in control group (the NBIO) were kept away from bulls and under pasture conditions; and the animals in the NBIO+S group were kept away from bulls, were maintained on pasture, and were fed the same diet as the BIO+S group. Heifers were bred at 22-23 months of age, and pregnancy diagnosis was made 45 days after the end of the breeding season. There were differences (P<0.05) between groups regarding pubertal heifers up to 19 months (NPH), final body weight (FBW) and pregnancy rates (P<0.01), with an advantage for the animals in the BIO and BIO+S groups. Although the effect of a diet with greater protein and energy content was not clear in this experiment, the exposure of heifers to a male during the prepubertal period decreased age at the first breeding season, resulting in a significant reduction in age of first pregnancy in Nelore heifers kept under extensive management systems in a tropical environment.
authors.affiliation: Precoce Veterinary Assesment LTDA, R. Couto Magalhães, 261, Barra do Garças, MT, Brazil.
authors.forename: C M G
authors.initials: CM
authors.lastname: Oliveira
authors.forename: B D
authors.initials: BD
authors.lastname: Oliveira Filho
authors.forename: M L
authors.initials: ML
authors.lastname: Gambarini
authors.forename: M A O
authors.initials: MA
authors.lastname: Viu
authors.forename: D T
authors.initials: DT
authors.lastname: Lopes
authors.forename: A P F
authors.initials: AP
authors.lastname: Sousa
mesh_terms: D000367:Age Factors; D000821:Animal Feed; D000822:Animal Husbandry / Q000379:methods; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D035201:Brachiaria / Q000502:physiology; D001938:Brazil; D002417:Cattle / Q000502:physiology*; D019587:Dietary Supplements; D005260:Female; D008297:Male; D008897:Panicum / Q000502:physiology; D010775:Photic Stimulation; D011247:Pregnancy; D018873:Pregnancy Rate; D014329:Tropical Climate