Supplementing Merino ewes with melatonin during the last half of pregnancy improves tolerance of prolonged parturition and survival of second-born twin lambs

Effect of neonatal melatonin administration on behavioral and brain electrophysiological and redox imbalance in rats

Introduction

Melatonin (MLT) reportedly has beneficial effects in neurological disorders involving brain excitability (e.g., Epilepsy and Migraine) and behavioral patterns (e.g., Anxiety and Depression). This study was performed to investigate, in the developing rat brain, the effect of early-in-life administration of two different doses of exogenous MLT on behavioral (anxiety and memory) and electrophysiological (CSD analysis) aspects of brain function. Additionally, brain levels of malondialdehyde (MDA) and superoxide dismutase (SOD), both cellular indicators of redox balance status, were evaluated. We hypothesize that MLT differentially affects the behavioral and CSD parameters as a function of the MLT dose.

Materials and methods

Male Wistar rats received, from the 7th to the 27th postnatal day (PND), on alternate days, vehicle solution, or 10 mg/kg/or 40 mg/kg MLT (MLT-10 and MLT-40 groups), or no treatment (intact group). To perform behavioral and cognition analysis, from PND30 to PND32, they were tested in the open field apparatus, first for anxiety (PND30) and then for object recognition memory tasks: spatial position recognition (PND31) and shape recognition (PND32). On PND34, they were tested in the elevated plus maze. From PND36 to 42, the excitability-related phenomenon known as cortical spreading depression (CSD) was recorded, and its features were analyzed.

Results

Treatment with MLT did not change the animals' body weight or blood glucose levels. The MLT-10 treatment, but not the MLT-40 treatment, was associated with behaviors that suggest less anxiety and improved memory. MLT-10 and MLT-40 treatments, respectively, decelerated and accelerated CSD propagation (speed of 2.86 ± 0.14 mm/min and 3.96 ± 0.16 mm/min), compared with the control groups (3.3 ± 0.10 mm/min and 3.25 ± 0.11 mm/min, for the intact and vehicle groups, respectively; p < 0.01). Cerebral cortex levels of malondialdehyde and superoxide dismutase were, respectively, lower and higher in the MLT-10 group but not in the MLT40 group.

Conclusion

Our findings suggest that MLT intraperitoneal administration during brain development may differentially act as an antioxidant agent when administered at a low dose but not at a high dose, according to behavioral, electrophysiological, and biochemical parameters.

Effects of Implanting Exogenous Melatonin 40 Days before Lambing on Milk and Colostrum Quality

The effects of exogenous melatonin implanted before lambing on the quality of colostrum and milk yield were quantified in 715 ewes. Forty days before lambing, 246 ewes (1M) received a melatonin implant; another 137 ewes (2M) received two implants, and the remaining 332 ewes (C) did not receive an implant (control). Milk analysis was based on individual monthly milk samplings (June, July, and August) after lambing. A colostrum sample was collected from 303 ewes (118 1M; 73 2M; and 112 C), and IgG concentrations were measured. Ewes implanted with melatonin had higher (p < 0.01) daily milk yield (DMY) in the three samplings than the C ewes. On average, 1M ewes produced more milk (p < 0.05) than ewes in the other two groups, and 2M ewes produced significantly (p < 0.05) more milk than C ewes. In the first and third controls, ewes that received two melatonin implants had a lower (p < 0.05) SCC than C and 1M ewes, and in the second sampling, 1M and 2M ewes had a lower (p < 0.01) SCC than C ewes. Ewes that received melatonin implants had a higher (p < 0.01) IgG concentration (21.61 ± 1.03 mg/mL) than non-implanted ewes (16.99 ± 1.13 mg/mL); 2M ewes had the highest IgG levels. In conclusion, ewes that received a melatonin implant 40 d before lambing produced colostrum that had a higher IgG concentration than the colostrum from nonimplanted ewes, and produced more milk, which had a lower SCC. The effect on SCC was prolonged if the sheep received a second melatonin implant.

Melatonin treatment during late gestation of undernourished ewes: lamb body temperature and mother–young behaviours after birth

ContextIn extensive grazing sheep systems, pregnant ewes undergo periods of undernutrition because gestation coincides with winter when natural pasture is of lowest quantity and poorest quality. The lamb’s weight and thermoregulatory capacity, and the ewe–lamb bond at birth, may be compromised. Maternal melatonin treatment during gestation may reverse these effects.AimThe aim was to determine the effects of melatonin treatment of single-lambing, undernourished ewes during the last third of gestation on lamb birthweights and body temperatures, and on ewe–lamb interactive behaviour after birth.MethodsAt Day 100 of gestation, 39 single-bearing ewes received a subcutaneous melatonin implant, and 54 ewes served as controls with no implant. Throughout gestation, the ewes remained under extensive conditions grazing on natural pasture. Measurements were made of lamb birthweight, body temperatures (surface temperature by infrared thermography and rectal temperature), and ewe–lamb behaviours during a handling test at 6–17h after lambing.Key resultsThere was no effect of melatonin treatment on lamb birthweight or rectal temperature, or on ewe–lamb interaction behaviours. Hip minimum surface temperature was greater in lambs from melatonin-treated ewes than lambs from control ewes (21.2°C±0.9°C vs 18.8°C±0.8°C; P=0.05), and there was a similar trend for hip mean surface temperature (24.6°C±0.9°C vs 22.3°C±0.7°C; P=0.06). Rump surface temperatures were greater in male than female lambs: maximum (27.9°C±1.2°C vs 22.9°C±1.2°C; P=0.01), minimum (22.2°C±1.5°C vs 16.7°C±1.5°C; P=0.02) and mean (25.4°C±1.3°C vs 20.5°C±1.3°C; P=0.02).ConclusionMelatonin treatment during the last third of ewe pregnancy slightly enhanced the surface temperature of lambs at birth but did not influence ewe–lamb interaction behaviour after birth (i.e. after establishment of the ewe–lamb bond).ImplicationsFurther study in more depth is warranted into the possible effects of maternal supplementation with commercial melatonin implants on lamb development, thermoregulatory capacity, behaviour and survival rates in extensive grazing systems, including the effect on ewe–lamb behaviours immediately after birth for both singletons and twins.

Implanting melatonin at lambing enhances lamb growth and maintains high fat content in milk

Three experiments were designed to study the effects of melatonin implantation of ewes and lambs after lambing on the growth of lambs and milk quality throughout lactation. In experiment 1, 53 lambs either did (n = 28) or did not (n = 25) receive a subcutaneous 18-mg melatonin implant at the base of the left ear. In experiment 2, 55 lambs and their mothers either did (lambs: n = 28; ewes: n = 15) or did not (lambs: n = 27; ewes: n = 16) receive a melatonin implant. Milk samples were collected at 15, 30, and 45 d after lambing. In experiment 3, 16 lambs were separated from their mothers 24 h after birth, moved to an artificial rearing unit, and either did (n = 9) or did not (n = 7) receive a melatonin implant. In the three experiments, implants were inserted 24 h after lambing, and lambs were weighed (LW) weekly until weaning (for each experiment, 7, 6, and 5 wk., respectively). Average daily gains (ADG) from birth to weaning were calculated. Melatonin treatment of lambs did not have a significant effect on LW at weaning or ADG, but lambs reared by implanted ewes in experiment 2 presented higher (P < 0.05) LW (±S.E.M.) at weaning (implanted: 13.61 ± 0.51; non-implanted: 12.09 ± 0.57 kg) and ADG (implanted: 221.00 ± 10.45; non-implanted: 189.92 ± 12.44 g/d) than did lambs reared by control ewes. At day 45 of lactation, milk fat and total solid content were higher (P < 0.05) in implanted ewes than they were in control ewes. Groups did not differ significantly in the protein and lactose content of their milk. In conclusion, melatonin treatment of ewes at lambing induced a high growth rate of their lambs and increased the fat content of the milk; however, the direct treatment with melatonin of the lambs at birth did not have an effect in their growth rate.

Supplementing pregnant Merino ewes with caffeine to improve neonatal lamb thermoregulation and viability

Percentages of lamb mortalities prior to weaning are a significant and persistent problem for the Australian sheep industry. Maternal caffeine supplementation reduced stillbirths and improved viability in piglets; however, the efficacy of caffeine in enhancing viability and lamb survival is equivocal. The aim of this study was to determine the optimal concentration and duration of maternal caffeine supplementation to improve lamb viability; time to stand and suck with consumption of colostrum occurring, as well as survival to weaning. Multiparous Merino ewes were supplemented with either 0 (CTL), 10 (C10) or 20 mg/kg (C20) body weight (BW) caffeine in feed after day 120 of gestation (dG), or 20 mg/kg BW (LC20) caffeine from dG 142 until parturition. Ewes were housed indoors in individual lambing pens from dG 130 to 72 -h post-partum (pp). Values for pp ewe and lamb variables were analysed using a generalised linear mixed model in IBM SPSS version 25. While ewes within the CTL, C10 and LC20 groups consumed more caffeine compared to C20 ewes (P =  0.001), lambs of C20 ewes had greater rectal temperatures at 20 -h pp (P =  0.021), greater 4 -h serum IgG concentrations (P =  0.041), a longer latency to first sucking bout (P =  0.030), and a greater number of sucking attempts (P =  0.044) compared to lambs from CTL, C10 and LC20 ewes. These results indicate that caffeine supplementation during late-gestation stimulates neonatal lambs as a result of increased sucking (4 -h serum IgG) and increased temperatures within the first 24 -h.