Beta-carotene supplementation positively affects selected blood metabolites across time around the onset of puberty in goats

Meza-Herrera C.A. , Pacheco-Alvarez P., Castro O.E. , Macias-Cruz U. , Avendaño-Reyes L. , Mellado M. , VelizDeras F.G. , Contreras-Villarreal V. , Abad-Zavaleta J., Rodriguez-Martinez R. , Arellano-Rodriguez G. (2017): Beta-carotene supplementation positively affects selected blood metabolites across time around the onset of puberty in goats. Czech J. Anim. Sci., 62, 22–31. The possible effect of beta-carotene supplementation upon peripubertal changes in serum concentrations across time for total protein (TP), urea (UR), cholesterol (CHOL), and glucose (GLU) around puberty onset was evaluated. The experiment was carried out from June to November and prepubertal goats (n = 17, 3 months old, 7/8 Saanen-Alpine, 1/8 Criollo) were randomly assigned to: (1) beta-carotene group (BC) (n = 9; 17.3 ± 1.0 kg live weight (LW), 3.3 ± 0.12 body condition score (BCS), oral supplementation with 50 mg beta-carotene per day per goat) and (2) control group (CC) (n = 8; 16.1 ± 1.0 kg LW, 3.1 ± 0.12 BCS). Serum blood samples were collected along the experiment to quantify progesterone concentrations (P4) through radioimmunoassay, while TP, UR, CHOL, and GLU through spectrophotometric analyses. No differences (P > 0.05) occurred between treatments regarding LW and BCS, and TP (67.6 ± 2.4 g/l), UR (3.8 ± 0.17 mmol/l), GLU (5.06 ± 0.09 mmol/l), and CHOL (1.62 ± 0.07 mmol/l) concentrations. However, while a treatment × time interaction occurred between treatments for TP, GLU, CHOL (P < 0.05) favouring the BC group, an increased serum UR levels occurred in the CC group. Nonetheless, such general serum metabolite profile was related neither to the age Czech J. Anim. Sci., 62, 2017 (1): 22–31 Original Paper doi: 10.17221/1/2016-CJAS 23 Puberty onset is a complex process regulated by several environmental cues, in which the neuroendocrine system must convey external information to align different internal mechanisms and promote anatomical, physiological, and behavioral changes (Meza-Herrera et al. 2010). The last is accomplished throughout activation of an intricate circuitry which involves diverse endocrinological messengers and neurotransmitters, whose core endeavour is to reinitiate the activation of GnRH neurons at peripubertal stages (Dupont et al. 2014). Chronological age was originally involved as a key modulator of puberty onset (Meza-Herrera et al. 2010). Later on, other internal signals such as the acquisition of a critical body mass, serum increases in various metabolic hormones (e.g. insulin, IGF-1, T3, and leptin) along with augments in some blood analytes (e.g. glucose, cholesterol), have been closely linked to the reactivation of the hypothalamic–pituitary–gonadal (HPG) axis (Meza-Herrera and Tena-Sempere 2012; MezaHerrera et al. 2014). Whereas body energy reserve status has been defined as an important modulator of puberty initiation, other studies highlight the rate of muscle and fat accumulation across time in the activation of GnRH neurons (Rosales-Nieto et al. 2013). Interestingly, both approaches denote the pivotal role that, not only the adipose tissue but also the adipocyte-derived molecules adipokines (e.g. leptin, adiponectin, resistin, omentin, vaspin) may exert upon both energy balance and reproductive function (Meza-Herrera and Tena-Sempere 2012). Beta-carotene (BC), which is present in green plants, has a paramount role in mammals as precursor of vitamin A and retinoid, demonstrating to be a key bioactive micronutrient involved in multiple biological actions while promoting strategic events in a range of physiological processes at cellular and tissue level both in humans and animals (Harrison et al. 2012; Eroglu and Harrison 2013). Although many gene products linked to reproductive performance are known to be modulated by retinoic acid, the product of retinol oxidation (Harrison et al. 2012), other studies have proposed that BC might act in a direct fashion, independently from vitamin A (Kawashima et al. 2010, 2012; Kramer and Aurich 2010). Two different types of BC-metabolizing enzymes have been identified in several tissues from different species: (i) BCMO1 (BC-15',15'-monooxygenase-1) which right through a central cleavage converts BC to all-trans retinal, acting at cytosol level, and (ii) BCDO2 (BC-9',10'-dioxygenase) which throughout an eccentric cleavage generates β-ionone and β-apocarotenal, acting at mitochondrial level (Eroglu and Harrison 2013). Besides liver being the main site of BC accumulation (Eroglu and Harrison 2013), the mRNA expression of both types of BC oxygenases has also been detected at hepatocyte level (von Lintig et al. 2005). Building on such findings and previous studies of our group, we hypothesized that BC supplementation could be associated with changes in the profile of blood metabolites around the onset of puberty in goats. The blood analytes evaluated included total cholesterol (CHOL), glucose (GLU), total protein (TP), and urea (UR). The final seek was to gain insights regarding a possible relationship between BC supplementation and some blood analytes related to lipid, carbohydrate, and protein metabolism. MATERIAL AND METHODS General. All the methods and management of the experimental units used in this study were in strict accordance with accepted guidelines for ethical use, care, and welfare of animals in research at international (FASS 2010), national (NAM 2002), and institutional levels (reference number UACH/ DGIP/URUZA/11-510-405). Location, environmental conditions, animals, feeding, and experimental design. This study was conducted at the Southern Goat Research Unit (26°N latitude, 103°W longitude, 1117 m a.s.l.) of the Regional University Unit of Arid Lands, Chapingo Autonomous University (URUZA-UACH), (215.7 vs 226.5 ± 6.6 days; P > 0.5) nor to the percentage (44.4 vs 25.0 ± 17.0%; P > 0.05) of goats reaching puberty in the BC and CC groups, respectively. Results should help speed-up goat productivity while may also engender key management applications to different animal industries.