Role of Melatonin and the Biological Clock in Regulating Lactation in Seasonal Sheep

Impact of light on animal behavior has been known for a long time—from 1925, Rowan [30] showed that lighting conditions influence gonad activity in birds and the related processes are controlled not only by means of intraorganic signals. Studies carried out in subsequent years have established that, also in mammals, the gland reacting to changes in light conditions is the pineal gland, producing a substance called melatonin. Biosynthesis of melatonin in most animals studied to date occurs at a rhythm dependent on the photocycle. The highest concentrations of this hormone—often called “the hormone of darkness”—are recorded at night. Seasonal changes in melatonin secretion conditioned by activity of the biological clock, known also as “biochemical calendar”, are the key signals in the annual reproductive cycles of animals exhibiting seasonality of reproduction. Seasonality in sheep refers not only to the reproduction itself but also to lactation. One of the main hormones conditioning initiation and maintenance of lactation, synthesis of milk proteins, fat and immunoglobulins is prolactin (PRL), secreted primarily by lactotrophic cells in the adenohypophysis. Prolactin is also produced locally by the mammary gland—the hormone of this origin is identical to prolactin secreted by the pituitary gland. Until now, it was considered that the level of milk production in mammals is determined by both genetic and environmental factors. However, in recent years, many studies focused on the role of light as a modulator of prolactin levels. In livestock, changes in light-period length play a very important role as this determines their productivity and milk yield. Photoperiod is particularly important in short-day breeder animals (sheep), for which the length of light period is associated with changes in melatonin level. The modulating effect of melatonin on secretion of prolactin may take place via two different mechanisms. One is associated with the circadian rhythm, wherein—directly or through the medium of a factor popularly termed “tuberalin”—melatonin stimulates the release of prolactin. However, this effect is short-lived and is most likely applicable only to prolactin stored in lactotrophic cells of the pituitary. The second mechanism regulating the secretion of melatonin and prolactin is associated with the annual rhythms of secretion—melatonin, due to its lipophilic characteristics, has a direct effect on the secretion of prolactin. Under natural conditions, the maximum concentration of prolactin in the blood of sheep is observed over the long-day period, during which the melatonin level decreases. The lowest prolactin concentration is observed over the short-day period, where melatonin levels are at their highest. Changes in secretion of prolactin during lactation in sheep undoubtedly affect the amount of milk produced

Comparative typology in six european low-intensity systems of grassland management

European biodiversity significantly depends on large-scale livestock systems with low input levels. In most countries forms of grazing are organized in permanent or seasonal cooperations (land-owner/land-user agents) and covers different landscape such as alpine areas, forest, grasslands, mires, and even arable land. Today, the existence of these structures is threatened due to changes in agricultural land use practices and erratic governmental policies. The present chapter investigates six low-input livestock systems of grassland management with varying degrees of arrangements in different European countries and landscapes. These large-scale grazing systems (LSGS) are reindeer husbandry in Northern Sapmi (Fennoscandia), sheep grazing in the Polish Tatra mountains, cattle grazing in the Swiss and German Alps, cattle, sheep, and pig grazing in Baixo Alentejo, Southern Portugal, and sedentary sheep grazing in Central Spain. These systems showed very heterogeneous organizational patterns in their way of exploiting the pastoral resources. At the same time, these LSGS showed at least some of the following weaknesses such as poor economic performance, social fragility, and structural shortcomings for proper grazing management. Lack of proper mobility of herds/flocks or accession to specific grazing grounds can be a cause of environmental hazards. The surveyed LSGS are mostly dependent on public handouts for survival, but successive policy schemes have only showed mixed effects and, in particular study areas, clear inconsistencies in their aim to stop the general declining trend of LSGS

Impact of Photoperiod Length and Treatment with Exogenous Melatonin during Pregnancy on Chemical Composition of Sheep’s Milk

The aim of the study was to determine the effect of photoperiod and exogenous melatonin on milk yield and chemical composition of sheep’s milk. Sheep (n = 60) were randomly divided into three groups: lambing in February (Group 1—n = 20), lambing in June (Group 2—n = 20), and lambing in June and treated with subcutaneous melatonin implants (Group 3—n = 20). Milk yield was higher for Group 1 and Group 2 than for Group 3 (p < 0.01). The milk of ewes of Groups 2 and 3 had a significantly (p < 0.01) higher content of dry matter, protein, and fat. Group 3 sheep’s milk contained significantly more (p < 0.01) of SFA (Saturated Fatty Acids). The highest content of MUFA (Monounsaturated Fatty Acids) and PUFA (Polyunsaturated Fatty Acids) was found in the samples collected from Group 1, the lowest was in the milk of Group 3 animals. The highest (p < 0.01) CLA, content was identified in the milk of Group 1, while the lowest was recorded for the milk obtained from sheep treated with exogenous melatonin (Group 3). The experiment carried out has shown that day length and treatment with exogenous melatonin modulate the chemical composition of milk

The Improved Method for Determination of Orotic Acid in Milk by Ultra-Fast Liquid Chromatography with Optimized Photodiode Array Detection

Ultra-fast liquid chromatography (UFLC) with a photodiode array detector (DAD) for simple and rapid determination of orotic acid (OAc) in milk of sheep and cows is described. Milk samples are treated with acetonitrile (1:1, v/v) and then centrifuged at 4 °C. To 1 mL of the obtained supernatant 9 mL of ultrapure water was added. Subsequently, 0.5–6 µL of the resulting solution was injected into the UFLC-DAD system. Separation and quantification of OAc in milk samples was achieved using two Kinetex C18 columns (1.7 µm, 150 mm × 2.1 mm, i.d., 100 Å; Phenomenex) fitted with a pre-column of 4 mm × 2 mm, i.d. (Phenomenex) containing C18 packing material. All separations were performed at a column temperature of 35 °C while the ambient temperature was 21–24 °C. Satisfactory separation of OAc from endogenous species of milk can be achieved using the binary gradient elution program and UV detection at wavelengths 278 nm. Our original procedure resulted in suitable separation and quantification of OAc in milk samples; OAc eluted at 6.44 ± 0.03 min. The total run time of OAc analysis (including re-equilibration) was 27 min. As expected, the OAc peak was absent from the blank when the proposed gradient elution program and UV detection at 278 nm was used. The average recoveries of OAc standards added to milk samples were satisfactory (96.7–105.3%). The low inter-and intra-assay coefficient of variation derived from the measurements of OAc in cow and ovine milk samples (i.e., 0.784%, 1.283% and 0.710%, 1.221%, respectively) and in O-Ac standards (i.e., 0.377% and 0.294%, respectively), as well as high recoveries of OAc added to ovine and cows’ milk (~100%) and the low detection (0.04 ng) and quantification (0.12 ng) limits point to satisfactory accuracy, precision and sensitivity of the reported method. OAc concentrations in ovine milk samples were within the range from 25 to 36 mg/L, while OAc levels in cows’ milk samples was found in the range of 32–36 mg/L. Our original procedure is suitable for routine quantification of OAc in milk of ewes and cows

Identification and mapping of a new recessive dwarfing gene dw9 on the 6RL rye chromosome and its phenotypic effects.

The introduction of high-yielding semi-dwarf varieties of wheat into cultivation has led to a "green revolution." This has required intensive research into various sources of dwarfism in wheat. However, there has been very little advancement in research on dwarfing genes in rye in comparison to wheat or barley. So far, three dominant dwarfing genes (Ddw1, Ddw3, and Ddw4) and three recessive genes (ct1, ct2, and np) have been characterized and precisely mapped in rye. There is no complete catalog of dwarfing genes available in rye. This paper presents an identification of the source of dwarfism and preliminary characterization of the new recessive gene dw9 from the BK-1 line. The gene was mapped on the long arm of the 6R chromosome and belongs to the GA-insensitive group. The initial characterization of the influence of this gene on morphological traits shows that it significantly affects the decrease of yielding trait parameters. A full evaluation can be performed after detailed breeding studies