Biological role of melatonin during summer season related heat stress in livestock

Melatonin as a multifunctional modulator: emerging insights into its role in health, reproductive efficiency, and productive performance in livestock

Melatonin, a pleiotropic hormone plays a vital role in enhancing livestock performance not only by regulating circadian rhythms but also by exhibiting antioxidant, immunomodulatory, and metabolic regulatory effects that collectively improve resilience, fertility, and productivity. Melatonin's synthesis is predominantly influenced by light exposure, with increased production in darkness; however, factors such as diet and health status further modulate its levels. By helping animals adapt to environmental stressors, melatonin boosts immune responses, mitigates chronic illnesses, and optimizes production efficiency. Its regulatory influence extends to the hypothalamic-pituitary-gonadal (HPG) axis, enhancing hormone secretion, synchronizing estrous cycles, and improving embryo viability. This results in improved reproductive outcomes through the protection of gametes, increased sperm motility, and enhanced oocyte quality, all of which benefit the fertilization process. Additionally, melatonin positively impacts productive performance, promoting muscle growth, development, and optimizing milk yield and composition through its interaction with metabolic and endocrine systems. As ongoing research continues to uncover its broader physiological effects, melatonin supplementation emerges as a promising approach to improving livestock welfare, productivity, and sustainability in modern animal husbandry.

Identification and Functional Analysis of the Regulatory Elements in the pHSPA6 Promoter

Functional and expressional research of heat shock protein A6 (HSPA6) suggests that the gene is of great value for neurodegenerative diseases, biosensors, cancer, etc. Based on the important value of pigs in agriculture and biomedicine and to advance knowledge of this little-studied HSPA member, the stress-sensitive sites in porcine HSPA6 (pHSPA6) were investigated following different stresses. Here, two heat shock elements (HSEs) and a conserved region (CR) were identified in the pHSPA6 promoter by a CRISPR/Cas9-mediated precise gene editing strategy. Gene expression data showed that sequence disruption of these regions could significantly reduce the expression of pHSPA6 under heat stress. Stimulation studies indicated that these regions responded not only to heat stress but also to copper sulfate, MG132, and curcumin. Further mechanism studies showed that downregulated pHSPA6 could significantly affect some important members of the HSP family that are involved in HSP40, HSP70, and HSP90. Overall, our results provide a new approach for investigating gene expression and regulation that may contribute to gene regulatory mechanisms, drug target selection, and breeding stock selection.

Growth rate, feed intake, physiological responses and hormonal profile of Murrah buffaloes implanted melatonin during summer season

In order to find out the effect of melatonin implantation on physiological responses, hormonal profile, feed intake and growth performance, 12 growing Murrah buffaloes were selected. These animals were further divided equally in two groups i.e. control and treatment (melatonin implantation @ 18 mg/50 kg body wt.). Melatonin was implanted subcutaneously in the thoracic region after every 45 days' interval in treatment group. Body weight and physiological parameters, viz. respiration rate (RR), rectal temperature (RT), pulse rate (PR) were recorded at fortnightly interval. Blood samples were also collected aseptically from both the group of animals at fortnightly intervals and plasma was separated for quantitation of hormones. The physiological responses were found to be significantly lower in treatment group than control group of growing buffaloes. The levels of growth and cortisol hormones were higher in treatment than control group. No significant variation was observed in the IGF-I levels. The melatonin implantation improved the growth rate, ADG and feed intake of growing buffaloes than control group. Based on the results of the present study, it is evident that melatonin implantation to growing buffaloes worked as an antioxidant and lowered the stress levels and enhanced growth rate during heat stress. Higher growth rate in treatment group of growing buffaloes will help in reducing the age of puberty and ultimately increase the total productive life.

Lack of effect of melatonin on ovarian function and response to estrous synchronization and fixed-time AI during the nonbreeding season in lactating dairy buffalo (Bubalus bubalis)

The present study was conducted to examine whether pretreatment with melatonin would enhance ovarian follicular functions and increase response to estrous synchronization and fixed-time AI (TAI) during the nonbreeding season in lactating dairy buffalo. In Experiment 1, buffalo cows without a detectable corpus luteum (CL) were assigned on Day -20 (D-20) to three groups: control (n = 12); melatonin (n = 13); progesterone (P₄) (n = 15). Cows in the melatonin group were implanted with melatonin on D-20. From D0 to D9, there was imposing of an estrous synchronization treatment regimen using either a standard Ovsynch protocol (control, melatonin) or a P₄-based Ovsynch treatment regimen (P₄). There were no differences (P > 0.05) among groups for the presence of a CL at D0, size of the largest follicle at D0, ovulation to GnRH injection at D0 and D9, or the time to ovulation after injection of GnRH at D9. In Experiment 2, there was imposing of the same treatment regimens as in Experiment 1, with inclusion of TAI. Females of the P₄ group had a greater (P = 0.001) pregnancy/AI percentage (60 %) than those in the control (17 %) and melatonin (23 %) groups. Females of the P₄ group also had a larger (P = 0.005) CL at D20 compared with those in the control and melatonin groups. Findings indicate treatment with melatonin for 20 days did not affect ovarian functions or the response to an estrous synchronization treatment regimen and TAI during the nonbreeding season in lactating dairy buffalo.

Effects of photoperiod and light intensity on milk production and milk composition of dairy cows in automatic milking system

The purpose of this study was to determine the effects of photoperiod and light intensity on milk production, milk composition, hormones levels and blood metabolites indices of Korean Holstein dairy cows in automatic milking system (AMS). A total of 24 Holstein dairy cows were selected and used to four subsequent treatments for the experimental periods of 60 days. The light programs consisted of (1) Control: the natural photoperiod with 14.2 h of the light period and 9.4 h of the dark period (below 10 Lux); (2) T1: 16 h of the long day photoperiod (LDPP) with 50 Lux of light; (3) T2: 16 h of LDPP with 100 Lux of light; and (4) T3: 16 h of LDPP with 200 Lux of light, respectively. Importantly, there was a significant difference in the thurl activity of dairy cows between the different light intensity programs (p < 0.05). Milk yield was higher in T1 and T2 (40.80 ± 1.71 and 39.90 ± 2.02 kg/d, respectively) than those of Control and T3 (32.18 ± 1.51 and 35.76 ± 2.80 kg/d, respectively) (p < 0.05), but DMI was lower in T1, T2, and T3 compared to Control (p < 0.05). Also, milk fat percentage, the contents of milk fat and total solids were higher in T2 than those in the others (p < 0.05). The average daily melatonin level in milk was high to T3 (28.20 ± 0.43 pg/mL), T2 (24.62 ± 0.32 pg/mL), T1 (19.78 ± 0.35 pg/mL), and Control (19.36 ± 0.45 pg/mL) in order (p < 0.05). Also, the cortisol levels in milk and blood were lower in treatment groups than in Control (p < 0.05). The results of this study showed that it will be effective to improve the milk yield and milk composition, and to reduce the stress of dairy cows when the light conditions regulate to extend the photoperiod to 16 h at a light emitting diode (LED) intensity of 100 Lux under the AMS in dairy farm.

Dietary supplementation of acetate-conjugated tryptophan alters feed intake, milk yield and composition, blood profile, physiological variables, and heat shock protein gene expression in heat-stressed dairy cows

The purpose of this study was to investigate the effects of dietary supplementation of rumen-protected tryptophan (RPT) at four levels on milk yield, milk composition, blood profile, physiological variables, and heat shock protein gene expression in dairy cows under conditions of moderate-severe heat stress (MSHS, THI = 80~89). Sixteen early-lactating dairy cows (body weight = 719 ± 66.4 kg, days in milk = 74.3 ± 7.1, milk yield = 33.55 ± 3.74 kg, means ± SEM) were randomly assigned in a factorial arrangement to one of the four treatments: control group (n = 4, no RPT supplementation), 15 g/d RPT (n = 4), 30 g/d RPT (n = 4), or 60 g/d RPT group per cow (n = 4) supplemented to the TMR. A higher dry matter intake (DMI) and milk yield were found in the 30 g RPT group compared with the other groups, and the 3.5% fat-corrected milk yield, energy-corrected milk yield, milk fat, protein, β-casein, mono-unsaturated fatty acid, and poly-unsaturated fatty acid contents, and serum glucose content were observed in the 30 g RPT group (p < 0.05). The milk lactose concentration was significantly higher in the 30 g RPT group compared with the control and 60 g RPT groups (p < 0.05). The plasma cortisol level was lower, while the serotonin and melatonin concentrations were higher in the 30 g group compared with the other groups (p < 0.05). Heat shock protein (HSP) 70 expression was downregulated in the control and 15 g RPT groups, whereas the expression of HSP90 and HSPB1 remained unchanged among the groups. In particular, the 30 g RPT group was considered to have an improved DMI, milk yield, and lactose concentration, as well as anti-heat stress effects due to the simulation of serotonin and melatonin during MSHS.