Análise bioeconômica do farelo de arroz na recria de bezerras de corte em azevém / Bioeconomics analyses of rice brain use for reaning of beef heifers on Italian ryegrass pasture

Objetivou-se avaliar a economicidade, o desempenho produtivo e o desenvolvimento das estruturas corporais relacionadas ao trato reprodutivo de bezerras de corte mantidas exclusivamente em pastagem de azevém (Lolium multiflorum Lam.) ou em pastagem de azevém recebendo 0,5 e 1,0% do peso corporal (PC) de farelo de arroz integral (FAI) como suplemento. O método de pastejo foi o rotativo, e o intervalo entre pastejos foi estabelecido considerando-se a soma térmica necessária para a emissão de 1,5 folha de azevém (187,5ºC). O delineamento experimental foi o inteiramente ao acaso, com medidas repetidas no tempo. O ganho médio diário das bezerras não diferiu entre os sistemas alimentares. A taxa de lotação e o ganho de peso por área foram maiores quando as bezerras receberam 1,0% do PC de farelo de arroz integral. A maior margem bruta foi observada quando as bezerras receberam 0,5% de FAI. O custo variável obtido para os diferentes sistemas alimentares apresentou comportamento crescente em função dos níveis de FAI, superando o uso exclusivo do azevém em 49,4% e 81,8%. O peso corporal final, o escore de condição corporal e o escore do trato reprodutivo não diferiram entre os sistemas alimentares. Considerando-se um animal adulto com peso corporal médio de 450kg, as bezerras ao início do experimento apresentaram 34% do peso corporal adulto e peso corporal final médio de 56% do peso adulto. A utilização de níveis de farelo de arroz integral (FAI) na recria de bezerras de corte sob pastejo rotativo em azevém não modifica o ganho médio diário e o escore do trato reprodutivo. O fornecimento de 1% de FAI mostrou efeito substitutivo, proporcionando um incremento de 31,2% na taxa de lotação e de 38,3% no ganho por área. O sistema alimentar AZ0,5 permitiu uma maior margem bruta; já o retorno financeiro direto foi positivo em todos os sistemas alimentares, com melhor retorno calculado para o uso exclusivo do azevém.(AU)

The experiment was carried out with the objective of evaluating the gross margin, the productive and reproductive performance of beef heifers kept exclusively on ryegrass pasture (Lolium multiflorum Lam.) or ryegrass receiving 0.5 and 1.0% of body weight (BW) of whole rice bran as supplement. The grazing method was the rotational and the interval between grazings was set by the thermal sum required for the appearing of 1.5 ryegrass leaf (187.5ºC). The experimental design was completely randomized with repeated measures. Heifers average daily gain did not differ between the feeding systems. The stocking rate and weight gain per area were higher when heifers received 1.0% BW of whole rice bran. The higher gross margin was observed when heifers received 0.5% BW. The variable cost obtained for the different feeding systems showed increasing behavior depending on the WRB levels, surpassing the exclusive use of ryegrass in 49.4% and 81.8%. The final body weight, body condition score and reproductive tract score did not differ between the feeding systems. Considering an adult animal with an average body weight of 450kg, the heifers at the beginning of the experiment showed 34% of mature body weight and final average body weight of 56% of adult weight. The use of rice bran levels (FAZ) in the rearing of beef heifers under rotational grazing on ryegrass does not change the average daily gain and the reproductive tract score. The supply of 1% FAI showed substitutive effect, providing an increase in capacity of 31,2% and 38.3% rate of the gain per area. The food system AZ0,5 allowed a higher gross margin, as the economic return was positive in all food systems, with better return calculated for the exclusive use of ryegrass.(AU)

Maternal lactocrine programming of porcine reproductive tract development.

The lactocrine hypothesis for maternal programming of female reproductive tract development is based on the idea that non-nutritive, milk-borne bioactive factors (MbFs), delivered from mother to offspring during nursing, play a role in determining the trajectory of development with long-term consequences in the adult. Porcine female reproductive tract development is completed postnatally, and the period during which maternal support of neonatal growth derives exclusively from colostrum/milk defines a window of opportunity for lactocrine programming of reproductive tissues. Beyond nutrition, milk serves as a delivery system for a variety of bioactive factors. Porcine relaxin is a prototypical MbF. Present in colostrum at highest concentrations at birth, relaxin is transmitted into the circulation of nursing piglets where it can act on Relaxin receptors found in neonatal female reproductive tract tissues. This process is facilitated by the physiology of the maternal-neonatal dyad and the fact that the neonatal gastrointestinal tract is open to absorb macromolecules for a period of time postnatally. Age at first nursing and duration of nursing from birth are also important for porcine female reproductive tract development. These parameters affect both the quality and quantity of colostrum consumed. Disruption of lactocrine signaling by feeding milk replacer from birth altered porcine uterine, cervical, and testicular development by postnatal Day 2. Moreover, insufficient colostrum consumption in nursing piglets can impair uterine capacity to support viable litters of optimal size in adulthood. In the pig, lactocrine signaling supports neonatal organizational events associated with normal reproductive development and may program adult uterine capacity.

Prepubertal exposure to an oestrogenic mycotoxin zearalenone induces central precocious puberty in immature female rats through the mechanism of premature activation of hypothalamic kisspeptin-GPR54 signaling.

Sporadic epidemics and several researches in rodents indicated that zearalenone (ZEA) and its metabolites, the prevailing oestrogenic mycotoxins in foodstuffs, were a triggering factor for true precocious puberty development in girls. Nevertheless, the neuroendocrine mechanism through which ZEA mycoestrogens advance puberty onset is not fully understood. To elucidate this issue, hypothalamic kisspeptin-G-protein coupled receptor-54 (GPR54) signaling pathway that regulates the onset of puberty was focused on in the present study. Immature female SD rats were given a daily intragastric administration of corn oil (vehicle control), 50 µg/kg body weight (bw) of 17ß-estradiol (E2, positive control), and 3 doses (0.2, 1 and 5 mg/kg bw) of ZEA for consecutive 5 days starting from postnatal day 15, respectively. Puberty onset was evaluated by detecting the physiological and hormonal responses, and hypothalamic kisspeptin-GPR54 pathway was determined to reveal the neuroendocrine mechanism. As the markers of puberty onset, vaginal opening was significantly accelerated and uterine weight was increased in both E2 and 5 mg/kg ZEA groups. Serum levels of follicle stimulating hormone, luteinizing hormone and estradiol were also markedly elevated by E2 and 5 mg/kg ZEA, which is compatible with the changes in peripheral reproductive organs. The mRNA and protein expressions of hypothalamic gonadotropin-releasing hormone (GnRH) were both obviously elevated by E2 and 5 mg/kg ZEA. GnRH expression changes occurred in parallel with increased expressions of hypothalamic Kiss1 and its receptor GPR54 at both mRNA and protein levels. Most of these changes were also noted in 1 mg/kg ZEA group, but none in 0.2 mg/kg group. Therefore, within the context of this study, the No Observed Adverse Effect Level (NOAEL) for ZEA in terms of oestrogenic activity and puberty-promoting effect in immature female rats was considered to be 0.2 mg/kg bw per day, and the Lowest Observed Adverse Effect Level (LOAEL) was 1 mg/kg bw per day. In conclusion, prepubertal exposure to dietary relevant levels of ZEA induced central precocious puberty in female rats by premature activation of hypothalamic kisspeptin-GPR54-GnRH signaling pathway, followed by the stimulation of gonadotropins release at an earlier age, resulting in the advancement of vaginal opening and enlargement of uterus at periphery.

Effect of the aqueous extract of Senecio biafrae (Oliv. & Hiern) J. Moore on sexual maturation of immature female rat.

BACKGROUND: Senecio biafrae (Asteraceae) is a medicinal plant widely used by traditional healers in the western region of Cameroon for the treatment of female infertility. This experiment was designed to evaluate the effect of the aqueous extract from leaves and stems of S. biafrae (AESb) on the onset of puberty and some biochemical and physiological parameters of reproduction in immature Wistar female rats. METHODS: Different doses of AESb were daily and orally administered to immature female rats (13 animals/group) for 30 days. At the end of the treatment period, six animal of each experimental group were sacrificed and their body, ovarian, uterus weight; uterine, ovarian protein or cholesterol level as well as data on puberty onset recorded. The remaining animals of each group were used for the fertility test and some gestational parameters recorded. RESULTS: A linear increase in the growth rate of all animals was observed. The body weight gain in animals treated at the dose of 8 mg/kg of AESb significantly increased (p < 0.05) after 25 days of treatment while those receiving the doses of 32 and 64 mg/kg presented a significantly low body weight gain starting from the 19th day till the end of the treatment period. The ages (days) of animals at vaginal opening (VO) was significantly reduced (p < 0.05) in those treated with the doses of 32 (41.25 ± 0.51) and 64 mg/kg (41.42 ± 0.54) as compared to control animals (43.33 ± 0.73). AESb significantly increased (p < 0.05) the ovarian weight and the number of corpora lutea in animals treated with 8 mg/kg as well as the uterine weight and protein levels irrespective of the dose. No significant effect of the extract on various fertility and gestational parameters was registered. CONCLUSION: The overall results of the present study provide evidence on the puberty onset induction and ovarian folliculogenesis effect of AESb in immature female rat.

[The effectiveness of transcranial treatment using the AMO-ATOS-E apparatus for the correction of the reproductive system disorders in adolescent girls].

A combination of transcranial therapy and transcranial electrostimulation based on the use of the AMO-ATOS-E apparatus was applied to elucidate the hormonal status and to study lipid and carbohydrate metabolism in 84 girls of pubertal age. The correction of menstrual cycles in these patients brought about its normalization in 86.3% of the cases with the simultaneous reduction of their body weight by 9.26 +/- 4.28 kg during 3 months.

Distribution of vasopressin in the forebrain of spotted hyenas.

The extreme virilization of the female spotted hyena raises interesting questions with respect to sexual differentiation of the brain and behavior. Females are larger and more aggressive than adult, non-natal males and dominate them in social encounters; their external genitalia also are highly masculinized. In many vertebrates, the arginine vasopressin (VP) innervation of the forebrain, particularly that of the lateral septum, is associated with social behaviors such as aggression and dominance. Here, we used immunohistochemistry to examine the distribution of VP cells and fibers in the forebrains of adult spotted hyenas. We find the expected densely staining VP immunoreactive (VP-ir) neurons in the paraventricular and supraoptic nuclei, as well as an unusually extensive distribution of magnocelluar VP-ir neurons in accessory regions. A small number of VP-ir cell bodies are present in the suprachiasmatic nucleus and bed nucleus of the stria terminalis; however, there are extensive VP-ir fiber networks in presumed projection areas of these nuclei, for example, the subparaventricular zone and lateral septum, respectively. No significant sex differences were detected in the density of VP-ir fibers in any area examined. In the lateral septum, however, marked variability was observed. Intact females exhibited a dense fiber network, as did two of the four males examined; the two other males had almost no VP-ir septal fibers. This contrasts with findings in many other vertebrate species, in which VP innervation of the lateral septum is consistently greater in males than in females.

Effects of low-dose perinatal cadmium exposure on tissue zinc and copper concentrations in neonatal mice and on the reproductive development of female offspring.

It has been suggested that the toxic effects of cadmium (Cd) are the result of interactions with essential metals, such as zinc (Zn) and copper (Cu). Previous studies have shown altered Zn and/or Cu levels in the tissues of rodents that drank water supplemented with >50 ppm Cd. To evaluate the effects of lower level Cd exposure on maternal and neonatal Zn and Cu levels and on the reproductive organs of female offspring, mice were exposed to 0, 1 and 10 ppm Cd in the drinking water from conception to 10 days after birth. The Cd concentrations in the brains of the offspring were higher in the exposed group than in the control group at birth. In the kidneys and livers, the Cd concentrations were higher in the Cd-exposed group 10 days after birth. At birth, increased Zn concentrations were observed in the kidneys and livers of the Cd-exposed offspring, although the Cd concentrations in these tissues did not differ between the exposed and non-exposed groups. The hepatic Cu concentrations of the exposed mice tended to be lower than those of the control mice at birth and were significantly lower 10 days after birth. In addition, Cd exposure tended to delay the timing of vaginal opening and perturbed the estrous cycles of the female offspring. These findings suggest that perinatal Cd exposure, even at low levels, affects the Zn and Cu concentrations of neonates and the reproductive functions of female offspring.

Role of early GnRH administration in sexual behavior disorders of rat pups perinatally exposed to lead.

The effects of maternal exposure to lead (Pb) during the perinatal (1% and 0.1% Pb) periods of sexual brain differentiation were studied in adult male offspring. Maternal Pb levels were measured after treatment. Behavioral (open field and sexual behavior), physical (sexual maturation, body and organ weights), and biochemical (testosterone levels and hypothalamic monoamine and respective metabolite levels) data were assessed in perinatally exposed offspring. The effects of gonadrotopin-releasing hormone (GnRH) administration to pups at birth on puberty and sexual behavior were also investigated in offspring postnatally exposed to the metal. Results showed that perinatal administration of the two Pb concentrations did not modify maternal weight gain; 1% Pb exposure reduced offspring body weight during the 7 days of treatment while no changes were observed after 0.1% Pb exposure; neither Pb concentration altered offspring sexual maturation; the higher Pb concentration improved sexual behavior while the 0.1% concentration reduced it; exposure to 0.1% Pb caused decrease in testis weight, an increase in seminal vesicle weight and no changes in plasma testosterone levels; hypothalamic VMA levels were increased compared to the control group; GnRH administration reversed the effects of 0.1% Pb administration on male sexual behavior. These results show that perinatal exposure to Pb had a dose-dependent effect on the sexual behavior of rats and that a decrease in GnRH source in the offspring was probably involved in the reduction of their sexual performance.

Irreversible effects of neonatal exposure to p-tert-octylphenol on the reproductive tract in female rats.

It has been known for many years that administration of androgens or estrogens at critical periods of development in mammals causes severe long-term effects on the endocrine/genital systems. The environmental pollutant p-tert-octylphenol (OP) possesses a weak but clear estrogen agonist activity in in vitro and in vivo studies. In the present study, effects of neonatal exposure to OP on the reproductive tract of female rats were investigated. Newborn female pups were injected with 100 mg/kg OP subcutaneously within 24 h after birth. Administration was repeated every other day until postnatal day 15 (total of eight doses). Before weaning, serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) remained at low levels during OP exposure, although the serum FSH peak and the high LH level were obvious in the controls. Histologically, inhibition of uterine gland genesis was apparent. The day of vaginal opening was about 4 days earlier in OP-treated animals than in controls. Persistent estrus was consistently observed in OP-treated animals. Atrophic and polycystic ovaries without corpora lutea showed anovulation. In the endometrium, cell-proliferative activity and cell-death were increased and decreased, respectively, and expression of estrogen receptor alpha mRNA was apparent by in situ hybridization. Unexpectedly, endometrial hyperplasias appeared at 8 weeks of age. After ovariectomy, vaginal smears immediately became of castration type and the uterus was atrophied. These results suggested that neonatal exposure to a high dose of OP alters developmental hormonal secretion presumably due to a hypothalamo-pituitary-ovarian disorder, with accelerated vaginal opening, subsequent persistent estrus, and uterine endometrial hyperplasia. The changes in the uterus and vagina are ovary-dependent.

Effects of "products of chicken embryo" on growth and sexual development in rats.

Products of Chicken Embryo (PCE) such as Ji-Pei-Jing is a kind of food for Chinese children prepared from chicken embryo. Female rats on 21 days were administered with aqueous solutions of Ji-Pei-Jing (1.2%, 3%, 12%, and 48%, respectively) by gavage up to their onsets of puberty. The rats in the control group were treated with distilled water. However, Ji-Pei-Jing treatment exerted some effects on sexual maturation in the immature female rats. Essentially, the effects showed a dose-response tendency with an inverted "U" shape. The age of vaginal opening for group treated with Ji-Pei-Jing was significantly earlier than that to the control. Its uterus weight/b.w. ratio also significantly increased on day 30 and at the first estrus. There were significantly increases in the adrenal weight/b.w. ratio of 30-day-old rats that were treated with 3%, 12%, and 48% Ji-Pei-Jing. The rats treated with 48% Ji-Pei-Jing had significantly lesser ovary weight/b.w. ratio on day 30, too. The rats treated with Ji-Pei-Jing could normally ovulate at the first estrus, and no significant differences were observed during estrous cycles. The effects of PCE on serum levels of E2, P, LH in 30-day-old rats and FSH in 28-day-old rats were elevated significantly by 3% Ji-Pei-Jing treatment. It appears that the effects of PCE result from interaction of contained complex physiologically active substances. Steroids, especially estradio-17 beta, possibly play a key role, and polypeptide hormones may also exert important effects.

Steroidogenic factor 1 acts at all levels of the reproductive axis.

The conversion of cholesterol into steroid hormones occurs through the sequential actions of the cytochrome P450 steroid hydroxylases. Attempts to understand the mechanisms responsible for the temporal and spatial expression patterns of these enzymes led to the identification of a shared regulator, termed steroidogenic factor 1 (SF-1). SF-1 coordinately regulates the steroid hydroxylase genes and thus functions as a global mediator of steroidogenesis. Of greater significance, recent studies using a knockout mouse model have further implicated SF-1 in a variety of processes ranging from development of the steroidogenic organs to the normal function of gonadotropes and the development of the ventromedial hypothalamic nucleus. A fundamental aspect of elucidating the role of SF-1 at all levels of the reproductive axis is to identify its cell-specific target genes. The recent purification and cloning of the steroidogenic acute regulatory (StAR) protein has provided an intriguing new candidate through which SF-1 acts to mediate its effects on reproductive competence. These studies yield novel insights into the processes of steroidogenesis, endocrine development, and reproductive function.

Regulation of arcuate nucleus synaptology by estrogen.

Estrogen modulates the synaptology of the hypothalamic arcuate nucleus during sexual differentiation of the rat brain in both males and females. In males, testosterone of gonadal origin is converted to estrogen in the brain by an enzyme, aromatase, which is also present in females. The exposure of the male's hypothalamus to relatively high levels of estrogen (following a perinatal testosterone surge) leads to the development of a pattern of synaptogenesis which does not support an estrogen-induced gonadotrophin surge in the adult. In female rats, hypothalamic development occurs with permissively low levels of estrogen, enabling a midcycle estrogen-induced gonadotrophin surge and ovulation in adulthood. During adult reproductive life in female rats, circulating estrogen modulates the synaptology of the arcuate nucleus. The most physiological example of this is the 30-50% loss of axosomatic synapses following the preovulatory estrogen surge on diestrus-proestrus. Studies on post-synaptic membranes of the arcuate nucleus reveal sex differences in membrane organization and protein content which are estrogen-dependent. Estrogen apparently stimulates endocytosis of areas of post-synaptic membrane that are dense with small intramembranous protein particles, resulting in a reduction in the number of small intramembranous particles. This also appears to be the physiologic mechanism of neuronal changes in females during the estrus cycle. Repeated exposure to preovulatory levels of estrogen may lead to an age-related decline in reproductive capacity in female rats. Aging females lose the estrogen-induced gonadotrophin surge responsible for ovulation. This loss of function may result from a cumulative estrogen effect during the repeated ovarian cycles which results in a reorganization of the synaptology on which regulates the estrogen-induced gonadotrophin surge. The membrane organization of the senescent constant estrus aged female appears indistinguishable from the males. The hypothalamic circuits modulated by estrogen have yet to be delineated. However, recent research has shown that GABA, the monoamines, and several neuropeptides are participants in the estrogen-sensitive network which regulates GNRH secretion. In this regard, present work shows estrogen-induced changes in GABA and dopamine synapses in the arcuate nucleus.

Puberty in the rat: modulation by melatonin and light.

Although a role has been found for melatonin in species which have a seasonal reproductive cycle, very little is known on the role of melatonin in species such as the rat where seasonal cycles are a minor component of reproduction. But the rat is a photosensitive species, because it responds to changes in the lighting environment. Females do not become quiescent but they can have irregular estrous cycles, another way of controlling population dynamics. In this species, exogenous melatonin can exert an antigonadotropic action, providing conditions which apply to other species are also respected for the rat: melatonin must be given at the right time of the day, 9 to 12 hours after the onset of light, and at a given period of life, before the onset of puberty. Melatonin probably acts on the pattern of GnRH pulsatile secretion and the subsequent alterations of the hypothalamic-gonadal axis differ according to the sex of the animal. Endogenous melatonin rhythms are modified by the lighting environment, and results obtained with exogenous melatonin suggest that they could be one of the factors controlling timing of sexual maturation.