The reproductive performance of female goats treated with melatonin is not improved after introduction to bucks displaying springtime sexual activity if these does are experiencing decreasing body weight/condition score

Effect of biostimulation on growth rate and reproductive development of Bos indicus dairy heifers

The present study aimed to compare the growth rate, feeding behavior, reproductive development, and concentrations of GH and leptin in Sahiwal heifers exposed to direct bull contact, bull contact through a fenceline, or isolated from bulls. Overall, 24 heifers were allotted to three treatment groups (n = eight/group) based on birth weight, body weight, and age. Heifers from the non-exposed group (NBE) remained isolated from bulls; heifers stimulated by fenceline bull contact (FBE) remained continuously exposed to bulls through a fenceline, and heifers with direct bull contact (DBE+FBE) had direct contact with a bull during 6 h/day plus continuous fenceline bull exposure for the entire 24 h period. It was considered that heifers attained puberty when progesterone concentration was >1 ng/mL. Biostimulated heifers achieved puberty at both a lower age and body weight (P < 0.05) than NBE heifers. Overall, average daily gain (g/day) was greater in DBE+FBE (516.3 ± 4.5) and FBE (501.6 ± 4.3) than in NBE (441.8 ± 2.9, respectively; P < 0.01). Leptin and growth hormone concentrations were significantly greater in FBE and DBE+FBE than NBE heifers. Both groups of biostimulated heifers devoted more time eating than NBE heifers, P < 0.05). In conclusion, biostimulation of Sahiwal heifers, either by exposing them to bulls through a fenceline or by both fenceline exposure and direct contact, reduced the age of puberty and increased growth performance. Overall, fenceline bull exposure can be recommended as an easy handling management to stimulate reproductive precocity and growth rate in heifers.

The use of photoperiod-treated bucks to induce a "male effect" does not compensate for the negative effects of nutritional restriction of the females in Mediterranean goats

This work examined the effect of acute nutritional restriction or supplementation one week before male introduction on the reproductive performances of the "male effect" when using photostimulated or control males in goats. On 22 March, 84 anoestrous does were placed with photostimulated bucks or with bucks which had received no treatments. One week before male introduction, the females were provided with different nutritional regimes: Supplemented, restricted or control females. The non-esterified fatty acids (NEFAs) and Insulin Growth Factor-1 (IGF-1) concentrations were measured in the same samples. Fecundity, fertility, prolificacy and productivity were also determined. No interaction between both sources of variation was observed in any of the reproductive variables studied. Treatment of the bucks increased the percentage of females expressing behavioural oestrous associated with ovulation (71% vs 90% for Natural and Photo groups, respectively, P < 0.05). The Supplemented females showed higher ovulation rate than Restricted females (1.77 ± 0.13 vs 1.05 ± 0.05, P < 0.001), fecundity (71% vs 43%, P < 0.05); fertility (76% vs 29%, P < 0.05) and productivity (1.00 ± 0.15 vs 0.29 ± 0.11 kids per female, P < 0.01). In the Supplemented females, the higher reproductive results could be due to the lower NEFAs and higher IGF-1 concentrations at ovulation and at the time of oestrus compared to the Restricted females. Thus, the present experiment results demonstrate that nutrition is an important factor in the response to the "male effect" at Mediterranean latitudes, and its negative effect cannot be counterbalanced by using photostimulated bucks.

Photoperiod-Treatment in Mediterranean Bucks Can Improve the Reproductive Performance of the Male Effect Depending on the Extent of Their Seasonality

Simple Summary

On the extensive and semi-extensive goat farms of the Mediterranean region, the induction of the male effect is a common reproductive management practice in spring mating (seasonal anoestrous). The sexual activity displayed by the bucks is one of the main factors that determines the reproductive performance of this practice and, for that reason, it is essential to photostimulate the bucks prior to using it. However, the effectiveness of this photostimulation and the male effect could depend on the seasonality of the breed of buck used. Thus, the present work aimed to compare the efficiency of the male effect, in terms of doe reproductive response and reproductive performance, as induced by bucks made sexually active via photostimulation, from breeds with different reproductive seasonality (Murciano–Granadina, low reproductive seasonality vs. Blanca Andaluza, high reproductive seasonality). The results demonstrated that the Blanca Andaluza bucks subjected to a natural photoperiod and used for the male effect induced a lower percentage of females into oestrus and ovulation, resulting in lower productivity. This suggests that photoperiod-treated bucks efficiently induce the male effect, but photostimulation may be more necessary for breeds with deep seasonality.

Abstract

This study examines the effectiveness of the photoperiod treatment (extra light for 88 days) to render the bucks sexually active during the seasonal anoestrous in order to induce a male effect, depending on the reproductive seasonality of the breed of the bucks used. In April, 57 anoestrous Blanca Andaluza does were distributed into four groups with three males each: 13 were exposed to control Murciano–Granadina bucks (lower seasonality); 15 were exposed to photostimulated Murciano–Granadina bucks; 14 were exposed to control Blanca Andaluza bucks (higher seasonality), and 15 were exposed to photostimulated Blanca Andaluza bucks. After male introduction, the sexual behaviour of the bucks was assessed, and harness marks recorded doe oestrous behaviour. Ovulation was confirmed from plasma progesterone, and the ovulation rate was assessed by transrectal ultrasonography. Fecundity, fertility, prolificacy and productivity were also determined. All of the does in all of the groups showed ovulation. Interaction between both sources of variation was observed: the percentage of females showing oestrous (p < 0.01) and productivity (p < 0.05) was the lowest in the Blanca Andaluza control group (50% and 0.36 ± 0.17 goat kids born/female, respectively). In conclusion, photoperiod-treated bucks efficiently induce a male effect, but photostimulation could be more necessary for breeds with deep seasonality.

Melatonin supplement induced the hair follicle development in offspring rex rabbits

Previous studies have shown that the administration of melatonin (MT) to early post-natal fur-bearing animals increases the numbers of hair follicles (HFs). In this study, the effect of maternal MT supplementation on the HF development in offspring was investigated. To explore the potential underlying mechanisms, the expression of the melatonin receptor 1A (MTNR1A) gene was determined in the offspring. The Rex rabbit was the animal model, and 79 same-day-pregnancy females were randomly assigned to either a control (n = 39) or MT treatment (n = 40) group, and 10 mg MT microcapsules was implanted at the base of the neck of rabbits in the treatment group. Skin, lung, liver, muscle, kidney, heart and duodenum samples were collected from the newborn rabbits. The results showed that MT improved fur quality in the offspring rabbits by reducing the diameter of primary and secondary HFs, and increasing the HF population. MT did not affect the reproductive performance of female rabbits, and it did affect the blood levels of thyroid-stimulating hormone, prolactin and MT. In the offspring rabbits, MT significantly stimulated MTNR1A gene expression in the skin and heart (p < .01), whereas MTNR1A gene expression was significantly suppressed in the liver and kidney (p < .05). These results revealed that maternal MT supplementation increased HF density, reduced hairiness and improved the fur quality in Rex rabbit offspring. Maternal MT supply may modulate the responses of HFs in the offspring by upregulating the expression of MTNR1A in the skin. In this study, implantation of low-dose MT did not affect the reproductive performance of female rabbits or on the growth of their offspring.

Systematic review and meta-analysis of the efficacy of reproductive management practices used to induce resumption of ovarian cyclical activity in anestrous does

Reproductive management practices that use hormones, sociosexual biostimulation, nutritional management, or abiotic factors are used to induce the resumption of reproduction in anestrous does. However, their overall efficacy remains uncertain; therefore, the identification of evidence-based management recommendations to manipulate anestrous in goats is important. Electronic databases were searched to retrieve reports on studies using interventions based on hormonal, sociosexual, nutritional, and abiotic factors. Only experimental studies in which a group of anestrous does was treated and compared against an untreated group were included. Estrus, ovulation, and pregnancy were primary outcomes, whereas the onset of estrus after treatment, the ovulation rate, and the number of anovulatory days were secondary outcomes. Odds ratio (OR) and mean differences were used to synthesize pooled data, and random effects models were used to calculate them. Seventy studies involving 3974 goats met the inclusion criteria. Unclear risk of bias for random sequence generation and allocation concealment predominated across studies. Pooled data for hormonal, sociosexual, and abiotic interventions showed a significant, though variable, increase in estrus (OR range 7.15-144.80), ovulation (OR range 6.08-56.95), and pregnancy (OR range 3.94-30.8). Hormonal treatments significantly reduced the onset of estrus, whereas abiotic interventions failed to reduce the number of anovulatory days. Secondary outcomes were not assessed in trials using sociosexual approaches. Finally, except for pregnancy, no significant efficacy was observed for studies using nutritional management. In conclusion, reproductive management practices using sociosexual approaches showed the highest efficacy for restoring reproductive activity in anestrous does.

Research progress on the role of melatonin and its receptors in animal reproduction: A comprehensive review

Melatonin and its receptors play a crucial role in the regulation of the animal reproductive process, primarily in follicular development. However, the role that melatonin performs in regulating hormones related with reproduction remains unclear. Melatonin and its receptors are present both in female and male animals' organs, such as ovaries, heart, brain and liver. Melatonin regulates ovarian actions and is a key mediator of reproductive actions. Melatonin has numerous effects on animal reproduction, such as protection of gametes and embryos, response to clock genes, immune-neuroendocrine, reconciliation of seasonal variations in immune function, and silence or blockage of genes. The growth ratio of reproductive illnesses in animals has raised a remarkable concern for the government, animal caretakers and farm managers. In order to resolve this challenging issue, it is very necessary to conduct state-of-the-art research on melatonin and its receptors because melatonin has considerable physiognomies. This review article presents a current contemporary research conducted by numerous researchers from the entire world on the role of melatonin and its receptors in animal reproduction, from the year 1985 to the year 2017. Furthermore, this review shows scientific research challenges related to melatonin receptors and their explanations based on the findings of 172 numerous research articles, and also represents significant proficiencies of melatonin in order to show enthusiastic study direction for animal reproduction researchers.

The Hyperglycemic Effect of Melatonin in the Chinese Mitten Crab, Eriocheir sinensis

Melatonin has been identified in a variety of invertebrate species, but its function is not as well understood as in crustaceans. The effects of melatonin on hemolymph glucose levels and tissue carbohydrate metabolism in the Chinese mitten crab, Eriocheir sinensis, were fully investigated in this study. Moreover, whether the eyestalk (an important endocrine center in invertebrate species) involves in this process or not, also were clarified. Analysis revealed that eyestalk ablation, especially bilateral, caused a significant decrease in the hemolymph glucose level. Moreover, injection of melatonin induced hyperglycemia in a dose-dependent manner both in intact and ablated crabs. Based on the expression of CHH mRNA in the 10 different tissues, eyestalk, thoracic ganglion, intestinal tract and hemolymph were selected to estimate the effect of melatonin on the expression of CHH mRNA. Bilateral eyestalk ablation caused a significant increase in the expression of CHH mRNA in the thoracic ganglion, intestinal tract and hemolymph compared with the controls. In addition, injection of melatonin into intact or ablated crabs elevated the CHH mRNA level in the eyestalk, thoracic ganglion and intestinal tract tissues compared with controls. The hemolymph CHH mRNA after melatonin injection was elevated only in ablated crabs. Administration of melatonin resulted in a significant decrease in total carbohydrates and glycogen levels with an increase in phosphorylase activity levels in the hepatopancreas and muscle in intact and ablated crabs. Our findings demonstrated that melatonin can induce hyperglycemic effects in both intact and ablated crabs, suggesting that this effect is probably not mediated solely via eyestalk.