Long-day Period Research Articles

Effect of photoperiod on the DNA, RNA and protein concentration in the silkgland of tasar silkworm, Antheraea mylitta (D) (Lepidoptera, Saturniidae)

In Antheraea mylitta (D) (Lepidoptera, Saturniidae), the effect of photoperiod on total DNA, RNA, and protein concentration in the middle silk gland (MSG) and posterior silk gland (PSG) was studied. The photoperiod caused enhancement in the secretory activity and stimulates the sericogenesis process in MSG and PSG. The total nucleic acids and protein concentration of MSG and PSG under 24L:00D condition reached maximum level and then it decreased. Maximum nucleic acids and protein concentration were observed during long-day period and the minimum during short-day period. The photoperiod activated or inhibited the biological clock which acted upon the respective endocrine glands accordingly and control the process of sericogenesis. The larvae underwent significant changes with high DNA, RNA and protein concentration under 24L:00D, which is highly suitable for the silk protein synthesis.

Reproductive Seasonality, Estrous Cycle, Pregnancy, and the Recurrence of Postpartum Estrus Based on Long-Term Profiles of Fecal Sex Steroid Hormone Metabolites regarding Zoo-Housed Female Golden Takins (Budorcas taxicolor bedfordi).

This study investigates the non-invasive monitoring of the endocrine ovarian activities of captive female golden takins (Budorcas taxicolor bedfordi) based on long-term fecal sex steroid hormone metabolite dynamics. Fecal progesterone (P4) metabolite dynamics were monitored in nine females for 0.5-15 years between 2004 and 2022. Fecal estradiol-17β (E2) and estrone (E1) metabolites were measured during certain estrous cycles, and fecal E1 metabolite concentrations were measured during all gestation periods. The breeding season of the captive animals was mainly between May and December, and they were polyestrous animals whose breeding season begins during the long-day period. The onset of the breeding season occurred slightly earlier as age increased. The mean age (±SD) at puberty based on fecal P4 metabolite dynamics was 4.1 ± 2.9 years. The first conception ages ranged from 2.3-10.2 years. The mean estrous cycle period (±SEM) was 25.4 ± 1.1 days, and mounting and mating occurred in periods of low fecal P4 metabolite levels during the breeding season. The mean gestation period (±SD) from the estimated mating date to the calving date was 253.9 ± 5.7 days, and the fecal P4 metabolite distribution during pregnancy was bimodal. Fecal estrone metabolite levels gradually increased 21 weeks before delivery, peaked during the week of delivery, and then markedly decreased in the first week after delivery. Estrus resumed in the first April-August period after delivery (mean ± SD; 103.5 ± 40.9 days) or in May of the year after delivery (421.0 ± 16.5 days). This study revealed that the estrous cycle and pregnancy of female golden takins can be determined by fecal progesterone metabolite dynamics and that fecal estrone metabolite dynamics increases toward parturition and are useful for predicting the date of delivery. This endocrinological information is important for planned breeding efforts for the golden takins.

Size-driven parr-smolt transformation in masu salmon (Oncorhynchus masou)

Anadromous salmonids exhibit partial migration, where some individuals within a population migrate down to the ocean through complex interactions between body size and photoperiod. This study aimed to integrate the ontogenetic and seasonal patterns of smoltification, a series of changes for future marine life, in a strain of masu salmon (Oncorhynchus masou). Spring smoltification, as evidenced by the activation of gill Na+,K+-ATPase (NKA), was induced during winter under an advanced photoperiod. In addition, juveniles showed an additional peak in gill NKA activity in August regardless of the photoperiod. When juvenile masu salmon were subjected to feeding manipulations during the first spring/summer, only fish exceeding a fork length of 12 cm exhibited an increased gill NKA activity. We tested whether size-driven smoltification required a long-day period by exposing juveniles to a constant short-day length (9-h light and 15-h dark) from January to November. Juveniles under short-day conditions exceeded 12 cm in June but showed no signs of smoltification. Thus, masu salmon undergo photoperiod-limited, size-driven smoltification during the first summer and size-limited, photoperiod-driven smoltification the following spring. The findings of the present study provide a framework for further elucidation of the physiological mechanisms underlying partial migration in salmonids.

Moving Away from 12:12; the Effect of Different Photoperiods on Biomass Yield and Cannabinoids in Medicinal Cannabis

The standard practice to initiate flowering in medicinal cannabis involves reducing the photoperiod from a long-day period to an equal duration cycle of 12 h light (12L)/12 h dark (12D). This method reflects the short-day flowering dependence of many cannabis varieties but may not be optimal for all. We sought to identify the effect of nine different flowering photoperiod treatments on the biomass yield and cannabinoid concentration of three medicinal cannabis varieties. The first, "Cannatonic", was a high cannabidiol (CBD)-accumulating line, whereas the other two, "Northern Lights" and "Hindu Kush", were high Δ9-tetrahydrocannabinol (THC) accumulators. The nine treatments tested, following 18 days under 18 h light/6 h dark following cloning and propagation included a standard 12L:12D period, a shortened period of 10L:14D, and a lengthened period of 14L:10D. The other six treatments started in one of the aforementioned and then 28 days later (mid-way through flowering) were switched to one of the other treatments, thus causing either an increase of 2 or 4 h, or a decrease of 2 or 4 h. Measured parameters included the timing of reproductive development; the dry weight flower yield; and the % dry weight of the main target cannabinoids, CBD and THC, from which the total g cannabinoid per plant was calculated. Flower biomass yields were highest for all lines when treatments started with 14L:10D; however, in the two THC lines, a static 14L:10D photoperiod caused a significant decline in THC concentration. Conversely, in Cannatonic, all treatments starting with 14L:10D led to a significant increase in the CBD concentration, which led to a 50-100% increase in total CBD yield. The results show that the assumption that a 12L:12D photoperiod is optimal for all lines is incorrect as, in some lines, yields can be greatly increased by a lengthened light period during flowering.

Rams sexually activated in spring by light treatment stimulate social and sexual activities in non-activated rams

Twelve rams were used to confirm whether rams sexually activated in spring by light treatment increase social and sexual activities of non-treated rams in the presence of ewes. Males were divided into 2 groups: light-treated rams (group L, n = 6), which were exposed to artificial long days (16 h light) for 2 months (1 Nov-31 Dec), or non-exposed, control rams (group C, n = 6), exposed to the natural photoperiod. At the end of the long-day period, light-treated rams were returned to the natural photoperiod, groups isolated from each other. In mid-Feb, 3 rams from each group were put together such that 4 experimental groups were created: the remaining light-treated rams (L, n = 3), the remaining control rams (C, n = 3), and the other treated (L-mixed n = 3) and non-treated (C-mixed, n = 3) rams, exposed to 30, 30, and 60 ewes, respectively, in 3 separate paddocks. To identify each ram, large (30-cm-high) numbers were painted on the sides and rump of the males with washable sheep spray paint. Behaviors were documented by 4 video cameras using 6 30-minute segments from 1600 to 1800 h the following day (27 hours). C rams presented the lowest proportion of activities (P < 0.01), and C-mixed rams exhibited proportions similar to L and L-mixed rams. C rams exhibited the fewest fight attempts (P < 0.001), fighting (P < 0.05), pushing (P < 0.001), and sniffing another ram. The groups differed significantly (P < 0.001) in pushing, pawing, flehmen, and attempt mounting, and C rams had the fewest interactions. In conclusion, rams exposed to 2 months of long days at late-autumn early-winter increased social and sexual activities of unexposed rams. These observations can be explained by a “ram-to-ram effect”, which can enhance the endocrine activity of rams in sexual rest if they are joined with rams who have been made sexually active by a photoperiodic treatment. These findings suggest that socio-sexual interactions could be used to restrict out-of-season reproduction in this species.

Blue Light Supplemented at Intervals in Long-Day Conditions Intervenes in Photoperiodic Flowering, Photosynthesis, and Antioxidant Properties in Chrysanthemums.

The flowering of chrysanthemum (Chrysanthemum morifolium Ramat.), inhibited by long-day lighting, can be reversed with a short period of low supplemental blue light (S-BL). Both flowering and the reactive oxygen species (ROS) scavenging processes are primarily driven by sugars created by photosynthetic carbon assimilation. In addition, the antioxidant ability potentially affects flowering in photoperiod- and/or circadian rhythm-dependent manners. This indicates that there is an interactive relationship among blue (B) light, photosynthetic efficiency, sugar accumulation, and antioxidant ability in flowering regulation. Here, 4 h of 30 μmol·m-2·s-1 photosynthetic photon flux density (PPFD) S-BL was applied at the end of a 13-h long-day period (LD13 + 4B) at different intervals during 60 days of experimental duration. The five experimental groups were named according to the actual number of days of S-BL and their intervals: applied once every day, "60 days-(LD13 + 4B) (100.0%)"; once every other day, "30 days-(LD13 + 4B) (50.0%)"; once every three days, "15 days-(LD13 + 4B) (25.0%)"; once every five days, "10 days-(LD13 + 4B) (16.7%)"; and once every seven days, "7 days-(LD13 + 4B) (11.7%)". Two non-S-BL control groups were also included: 60 10-h short days (60 days-SD10) and 13-h long days (60 days-LD13). At the harvest stage, varying degrees of flowering were observed except in "60 days-LD13" and "7 days-(LD13 + 4B) (11.7%)". The number of flowers increased and the flower buds appeared earlier as the proportion of S-BL days increased in LD13 conditions, although the "60 days-SD10" gave the earliest flowering. The proportion of initial, pivotal, and optimal flowering was 16.7% ("10 days-(LD13 + 4B)"), 50.0% ("30 days-(LD13 + 4B)"), and 100.0% ("60 days-(LD13 + 4B)"), respectively. Meanwhile, a series of physiological parameters such as the production of enzymatic or non-enzymatic antioxidants, chlorophyll content, photosynthetic efficiency, enzyme activities, and carbohydrate accumulation were significantly improved by "30 days-(LD13 + 4B) (50.0%)" as a turning point until the peaks appeared in "60 days-(LD13 + 4B) (100.0%)", as well as the expression of florigenic or anti-florigenic and some antioxidant-synthetic genes. Furthermore, the results of principal component analysis (PCA) indicated that S-BL days positively regulated flowering, photosynthesis, carbohydrate accumulation, and antioxidant production. In aggregate, the pivotal and optimal proportions of S-BL days to reconcile the relationship among flowering, photosynthetic carbon assimilation, and antioxidant ability were 50.0% and 100.0%, respectively. However, there are still significant gaps to be filled in order to determine the specific involvement of blue light and antioxidant abilities in flowering regulation.

Exposure of rams in sexual rest to sexually activated males in spring increases plasma LH and testosterone concentrations

Eight stimulating rams, and twelve stimulated rams, were used to determine whether a similar endocrine response to the introduction of sexually active males in spring in a flock of ewes is observed in a flock of rams. The stimulating rams (n = 4) were induced into a sexually active state by exposure to 2 months of long days (16 h light/d) (15 December-15 February). At the end of the long-day period, rams were returned to the natural photoperiod. Control-stimulating rams (n = 4) were kept under the natural photoperiod. On April 20, stimulated rams were divided into 2 groups, and joined with activated (ACT; n = 6) or control stimulating rams (C; n = 6). On the day of ram introduction, stimulated rams were blood sampled for 8 h at 20-min intervals, from 4 h before to 4 h after ram introduction, and next day from 24 to 28 h after ram introduction, and analyzed for plasma LH concentrations, and 10, 20 and 30 days after ram introduction to measure plasma testosterone levels. Mean (±SEM) plasma LH concentrations (ng/ml) of stimulated rams were similar during the 4 h before stimulating-ram introduction (ACT: 0.59 ± 0.03; C: 0.53 ± 0.04; P > 0.05). The introduction of the photoperiod-treated stimulating rams increased LH concentrations of stimulated rams during the 4 h after their introduction (1.14 ± 0.37) compared with the C group (0.51 ± 0.03; P < 0.05), especially during the first hour (ACT: 0.93 ± 0.16; C: 0.49 ± 0.03; P < 0.05), and during the blood sampling period 24–28 h after ram introduction (0.75 ± 0.07 vs. 0.58 ± 0.04; P < 0.05). Before the introduction of stimulating rams, the LH pulse frequencies and amplitudes did not differ between groups; however, LH pulsatility was higher at 4 h (0.58 ± 0.11 pulses/h; P < 0.05), and had trend to be higher 24 h (0.50 ± 0.06) (P = 0.10) after the introduction of the photoperiod-treated stimulating rams compared with the control-stimulating rams (0.29 ± 0.08 and 0.29 ± 0.10, respectively). As for LH pulses, there was an effect of group (P < 0.05) on LH amplitude, which presented a trend to be higher in ACT rams 4 h after ram introduction (1.68 ± 0.30; P < 0.10) and higher 24 h (1.07 ± 0.08; P < 0.05) after ram introduction, compared with LH amplitudes of C rams (0.71 ± 0.06 and 0.82 ± 0.07, respectively). Plasma testosterone concentrations of rams exposed to photoperiod-treated activated rams were higher than those of rams exposed to control-stimulating rams, at 4 h, 20 and 30 days after ram introduction (P < 0.05). In conclusion, sexually active rams in spring are able to stimulate LH and testosterone secretion of other rams in sexual rest, a phenomenon we called “ram-to-ram effect".

Role of Internal Variability of Climate System in Increase of Air Temperature in Wrocław (Poland) in the Years 1951–2018

Abstract In the course of analysing the annual air temperature in Wrocław (TWr), a rapid change of the thermal regime was found between 1987 and 1989. TWr increased by &gt;1°C, a strong, statistically significant positive trend emerged. The analysis of processes showed that strong warming in the cold season of the year (December–March) occurred as a result of an increase in the NAO intensity and warming in the warm season because of increased sunshine duration in Wrocław (ShWr). Multiple regression analysis has shown that the winter NAO Hurrell's index explains 15% of TWr variance, and the ShWr of the long-day (April–August) period 49%, whereas radiative forcing 5.9%. This indicates that the factors incidental to the internal variability of the climate system explain 64% of the TWr variability and the effect of increased CO2 concentration only ~6%. The reason for this rapid change of the thermal regime was a radical change in macro-circulation conditions in the Atlantic-European circular sector, which took place between 1988 and 1989. The heat, which is the cause of warming in Wrocław, comes from an increase in solar energy inflow (April–August) and also is transported to Europe from the North Atlantic surface by atmospheric circulation (NAO). These results indicate that the role of CO2 in shaping the contemporary temperature increase is overestimated, whereas the internal variability of the climate system is underestimated.

Daily roosting behaviour of the critically endangered White-bellied Heron Ardea insignis as a function of day length

ABSTRACT The White-bellied Heron (Ardea insignis) is listed as a critically endangered bird species by BirdLife International due to the rapid population decline. Before this study, nothing was known about the night roosting behaviour of this imperiled species. Here, we report on the night roosting behaviour of the White-bellied Herons in Punatsangchhu and Mangdechhu river basins of Bhutan. There was a significant difference in landing and takeoff flights between the short- and long-day periods (P <0.05). Overall, the night roosting behaviour was dominated by sleeping (65 ± 11 min). We also documented two prominent behaviours that were thermoregulatory in function. The White-bellied Herons roosts solitarily on the tree branches in the night and makes extensive use of the night roosting trees. Therefore, night roosting trees are essential for consideration while assessing the home range size of the White-bellied Herons for their better conservation and management.

Light-induced sexually active rams provoke LH preovulatory surges and enhances LH concentrations in ewes after progestagen treatment.

The effect of the introduction of sexually active rams in spring on LH secretion in ewes after progestagen treatment has been studied. Two rams were induced into a sexually active state by exposure to 2 months of long days (16 h of light/d) from 1 January (SAR), and another 2 rams were exposed to the natural photoperiod, so that they were not sexually activated in spring (control; C). At the end of the long-day period, rams were returned to natural photoperiod conditions. Fifteen ewes synchronized in estrus by intravaginal sponges were assigned to three groups at sponge withdrawal (hour 0): SAR (n = 5), exposed to SAR rams; C (n = 5), exposed to C rams, and ISO (n = 5), kept isolated from rams. Twenty-four hours after pessary removal (hour 0), rams were introduced into the SAR and C groups. Three SAR ewes presented preovulatory LH surges; the proportion was significantly (P < 0.05) higher in this group (3/5) than in the others (C: 0/5, ISO: 0/5). SAR introduction induced a more marked (P < 0.05) increase in mean LH plasma concentrations (before rams: 1.34 ± 0.19; after rams: 6.94 ± 2.66 ng/ml) than C (before: 0.96 ± 0.29; after: 3.60 ± 1.44) or ISO (before: 1.26 ± 0.42; after: 2.14 ± 1.36) groups, and significantly (P < 0.05) higher plasma LH levels after ram introduction. In conclusion, only light-treated sexually activated rams induced LH preovulatory surges in ewes in the seasonal anestrus, when ewes are synchronized with progestagen treatment in the absence of eCG.

Yield stability and adaptability of kenaf (Hibiscus cannabinus L.) genotypes at different kenaf growing regions in Indonesia

Stability and adaptability analysis is a very important tool for breeders to find out the potentiality of a genotype in various environments. Twenty kenaf genotypes were evaluated in 6 locations, namely Asembagus (Situbondo Regency), Muktiharjo (Pati Regency), Sumberrejo (Bojonegoro Regency), Laren (Lamongan Regency), Wanareja (Cilacap Regency), and Sukolilo (Pati Regency). For Asembagus, Muktiharjo, and Sumberrejo testing was carried out in 2013 for 2 seasons, namely longday and shortday period, while testing in Laren, Wanareja, and Sukolilo carried out in 2014 for one season on a longday period. The study is to determine the effect of the environment on the fiber yield of kenaf genotypes and their adaptation in various environments. The results of variance analysis showed that genotypes, environment, and genotype by environment interactions had a very significant effect on the fiber yield of kenaf. The average fiber yield of kenaf ranges from 0.846 to 3.758 tons per ha. Regression coefficients and mean square of deviation from regressions differ from each other indicating that there are variations in stability and adaptability between genotypes tested.

Role of melatonin and circadian rhythms in seasonal reproduction in rams

In the ram, changes in daylength influence testicular activity by modifying the release of luteinizing hormone-releasing hormone (LH-RH) and thus the gonadotrophins. To investigate the nature of this response the hourly fluctuations in the circulating levels of prolactin, luteinizing hormone (LH) and melatonin were measured in rams kept under various artificial lighting conditions. In Exp. 1, 8 Soay rams (4 control and 4 from which the superior cervical ganglia had been removed) were exposed to alternating 16-week periods of short days (8L: 16D) and long days (16L: 8D) for over 2 years, and blood samples were collected hourly for 25 h on two occasions. The lighting regimen resulted in marked testicular and endocrine changes in the controls but not in the ganglionectomized rams which had low or undetectable levels of melatonin (less than or equal to 33 pg/ml) and an unusual diurnal rhythm in prolactin. In Exp. 2, 8 intact Soay rams were exposed to an ahemeral lighting regimen of 8L: 28D for 16 weeks; at the end of this period blood samples were collected hourly for 52 h and assayed for prolactin. During the pretreatment period of long days (16L: 8D), the testes became fully regressed. During the 16 weeks of 8L: 28D, redevelopment occurred, but the growth of the testes was slow compared to that normally occurring under short days of 8L: 16D. The prolactin profiles showed evidence of circadian rhythm in hormone secretion, with a correlation between the timing and duration of the rhythm and the degree of testicular development. These combined results support the idea that the photoperiodic response in the ram involves an interplay between the secretory activity of the pineal gland, and a light/dark entrained circadian mechanism in the brain.

A chronological assessment of foraging activities of the Cotton Pigmy Goose, Nettapus coromandelianus Gmelin, 1789 at Dulahara pond, Ratanpur, Chhattisgarh, India

ABSTRACTThis study was planned to assess the foraging activity of ecological important avian species the N. coromandelianus at Dulahara pond of Ratanpur, Chhattisgarh. In present work we observed the effect of “time of the day” and “photoperiod” on daytime foraging activities of N. coromandelianus. The most applied foraging skills of N. coromandelianus were documented for two repetitive days each for the period of long days (March and April 2015) and short days (December 2015 and January 2016). One-way ANOVA (by SPSS 16.0) was employed to observe the effects of “photoperiod” and “time of the day” on daytime foraging pattern in order to the frequency of foraging techniques. The rhythms in daytime foraging movement were estimated by means of Cosinor rhythmometry at 24 h and 12 h. The current study clarified that the N. coromandelianus mostly applied three main techniques viz., head and neck dipping, diving and striking on which both the diving and striking were the most employed technique while the head and neck dipping was less employed technique during foraging. Moreover, the N. coromandelianus maximally involved for foraging activities during the short day than long day.

Extended day length in late winter/early spring, with a return to natural day length of shorter duration, increased plasma testosterone and sexual performance in rams with or without melatonin implants.

Sixteen rams were used to quantify the effects of long days, imposed during late winter/early spring, with or without exogenous melatonin, on plasma testosterone concentrations and ram serving capacity. Rams were assigned to two groups: photoperiod-treated rams (Artificial Photoperiod, AP; n=8), exposed to 2months of long days (16hr of light/day) between 22 December and 22 February, and control rams (Natural Photoperiod, NP; n=8). At the end of the long-day period, AP rams were returned to the natural photoperiod, and each ram in the two groups either did (+M) or did not (-M) receive three subcutaneous melatonin implants. Four groups were created as follows: AP+M (n=4), AP-M (n=4), NP+M (n=4) and NP-M (n=4). Thirty days after of the onset of photoperiodic treatment, AP rams (13.5±2.8ng/ml) had significantly (p<.05) lower testosterone levels than NP rams (36.7±1.0), and similar differences were not apparent at the end of the photoperiod treatment. A month later, AP rams (24.3±7.9) had higher (p<.10) testosterone levels than NP rams (13.1±5.0), with no effect of melatonin treatment. Fifty days after melatonin implantations, rams were exposed for 20min to three oestrous ewes. AP rams (2.50±0.42) exhibited significantly (p<.05) more serves than did NP rams (1.11±0.39), and melatonin treatment had no significant effect; however, the interaction between treatments was significant. Time to first serve was significantly (p<.05) shorter in AP (2.30±1.20min) than it was in NP rams (5.58±0.68min). In conclusion, exposure to 2months of long days in late winter/early spring, with a return to natural day length of shorter duration, increased plasma testosterone concentrations and sexual performance in rams with or without exogenous melatonin. This particular management is an option if a non-hormonal reproductive strategy is scheduled; yet, if the use of exogenous hormones is feasible, melatonin implants increase the mating efficiency of rams.

Regulation of growth and development in phytochrome mutants of Arabidopsis thaliana by solar UV

Phytochrome mutants (phyA, phyB and phyAB) of Arabidopsis thaliana were grown under ambient and UV-excluded sunlight to understand their influence on growth and development by mutual exclusion. Phytochrome A and B played a complementary role in the regulation of germination. Suppression of hypocotyl length was predominantly under the control of phytochrome B; UV photoreceptors were active in suppression of hypocotyl growth only in phyB and phyAB mutants. Exclusion of UV promoted the number and the area of rosette leaves only in presence of phytochrome A and B. Phytochrome mutation reduced petiole length, whereas UV exclusion led to an increase. Requirement of long-day period for flowering was removed in the mutants. Under short-day conditions, flowering was predominantly under the control of phytochrome B, since phyB mutants flowered earlier than phyA mutants. Solar UV regulates the number of boltings and number of siliques per plant. Overall biomass of the plants is enhanced by the exclusion of UV only in the wild type. The interaction of phytochromes with UV photoreceptors is discussed in the paper.

Effets des conduites d’élevage sur la production de lait, las taux butyreux et protéique et la composition en acides gras du lait de vache...

Les facteurs de variation de la composition en Acides Gras (AG) du lait ont été évalués en 2010 dans 1 528 élevages bovins, caprins et ovins laitiers. Le stade de lactation influe sur la proportion d’AG Saturés (AGS) avec une augmentation jusqu’à 4 mois, forte en bovins, plus modérée en caprins et ovins. La part des AG MonoInsaturés (AGMI) évolue inversement, alors que celle des AG PolyInsaturés (AGPI) reste relativement stable tout au long de la lactation. L’âge à la première mise bas affecte peu la composition en AG chez les bovins et les caprins, mais davantage chez les ovins pour lesquels la part des AGS augmente avec l’âge. Chez les bovins, la période de vêlage a peu d’effet sur le profil en AG, mais la saison de production influence notablement le pourcentage des AGS du lait, dans le même sens que le taux butyreux du lait qui est minimal en période de jours longs. Cette saisonnalité est moins importante en caprins, elle est confondue avec la saison de pâturage en ovins. Les régimes alimentaires ont davantage d’influence sur la composition du lait chez les bovins que chez les petits ruminants. Seule la présence du pâturage influence les grandes familles d’AG du lait, dans le même sens pour les 3 espèces, avec une diminution systématique et d’ampleur modérée (petits ruminants) à forte (bovins) de la part des AGS par rapport au régime de référence. En contrepartie, les pourcentages des AGMI et AGPI ont tendance à augmenter avec l’herbe jeune fraîche. L’effet des autres régimes alimentaires, contenant des fourrages conservés, sur les principales familles d’AG du lait est moins net.

Study the Effect of Photoperiod Duration on Dynamic Carbohydrates Composition and Enzymes Activity in Soybean Leaves

This study was conducted to investigate the correlation and dynamics of carbohydrate content over diurnal photoperiodic cycle and sucrose-phosphate synthase activity, amylase and invertase in leaves isogenics at EE genes short day and photoperiodically neutral lines of soybean in view of paces of development over different duration period of the day. In short-day photoperiodic cycle disposition of dynamics of sugar and starch content over a day-light period, their runoff over a moon-light period and also activity of enzymes of photoperiodically neutral lines change similar to it of short-day lines. At short day neutral lines more intensively accumulate monosugar and sucrose. At long day, amylose is accumulated in content of starch comparing to short-day lines. Runoff tenseness over night period of short-day photoperiodic cycle in both groups is higher than over the same period of long-day cycle. Capability of photoperiodically neutral lines to change disposition of carbohydrate exchange over a short-day period similar to its disposition of short-day lines is one of the considerable factors in favor of the fact that under the given conditions process of growth and development, this is provided with sufficient amount of substance and energy. As a result morphogenetic processes run at the same speed over both short-day and long-day periods. It allows photoperiodically neutral lines to transit to blooming at the same term over different duration period of the day.

Short-day and melatonin effects on milking parameters, prolactin profiles and growth-hormone secretion in lactating sheep

We tested the hypothesis that elevated levels of melatonin in lactating sheep, simulated either by short-day conditions or by melatonin implants, would decrease milk yield while disturbing the rhythm of prolactin (PRL) and growth-hormone (GH) secretion. Eight weeks after lambing, lambs were weaned, and the ewes were subsequently used for milking. The ewes were divided into three groups: (i) long-day control group (LDC, n=20); (ii) long-day melatonin-treated group (LDM, n=20) and (iii) artificial short-day group (ASD, n=20). Milk yields were recorded individually at 10-day intervals from day 57 of lactation. Blood samples were drawn from the sheep every 28 days to monitor the changes in PRL and GH secretion. On each sampling date, blood samples were collected at 20-min intervals over a 6-h period beginning at 12:00p.m. The plasma concentrations of PRL and GH were measured using radioimmunoassay. The longest duration of lactation was found in LDC sheep, and the shortest duration was found in LDM and ASD sheep (p<0.05). The highest milk yield was found in the LDC group. Significantly (p≤0.01) less milk was obtained from the ASD group. The highest PRL concentration was found during the long-day period (from May to July) in LDC sheep. Prolactin concentration decreased with increasing duration of lactation and decreasing day length. The use of melatonin implants (LDM group) or artificial short-day conditions (ASD group) significantly (p≤0.01) decreased PRL secretion and reduced milk yield as early as the beginning of milking. Growth-hormone concentrations were significantly (p≤0.001) higher in LDC ewes than in LDM and ASD ewes. In contrast to the temporal profile of PRL secretion, GH concentrations decreased during the long-day period but increased as lactation progressed and day length shortened. Despite the considerable reduction in GH concentrations, the GH-secretion profile retained its characteristic seasonal rhythm. Therefore, we conclude that exogenous melatonin (from implants or induced by artificial photoperiod manipulation) decreases milk yield primarily through its effect on PRL concentrations in lactating ewes.

The effect of nutrition on the neural mechanisms potentially involved in melatonin-stimulated LH secretion in female Mediterranean goats

This research examines which neural mechanisms among the endogenous opioid, dopaminergic, serotonergic and excitatory amino acid systems are involved in the stimulation of LH secretion by melatonin implantation and their modulation by nutritional level. Female goats were distributed to two experimental groups that received either 1.1 (group H; n=24) or 0.7 (group L; n=24) times their nutritional maintenance requirements. Half of each group was implanted with melatonin after a long-day period. Plasma LH concentrations were measured twice per week. The effects of i.v. injections of naloxone, pimozide, cyproheptadine and N-methyl-d,l-aspartate (NMDA) on LH secretion were assessed the day before melatonin implantation and again on days 30 and 45. The functioning of all but the dopaminergic systems was clearly modified by the level of nutrition, melatonin implantation and time elapsed since implantation. Thirty days after implantation, naloxone increased LH concentrations irrespective of the level of nutrition (P<0.05), similar to NMDA in the melatonin-implanted H goats (HM; P<0.01). On day 45, naloxone increased LH concentrations in the HM animals (P<0.05), similar to cyproheptadine in both the non-implanted H (HC) and the HM animals (P<0.01). Finally, at 45 days, NMDA increased the LH concentration in all subgroups (P<0.01). These results provide evidence that the effects of different neural systems on LH secretion are modified by nutritional level and melatonin implantation. Endogenous opioids seem to be most strongly involved in the inhibition of LH secretion on days 30 and 45 after melatonin implantation. However, the serotonergic mechanism appears to be most influenced by nutritional level.

The effect of melatonin treatment in rams on seasonal variation of testicular size and semen production parameters

The administration of exogenous melatonin can mimic the stimulatory effect of short days in advancing the onset of maximum reproductive parameters in seasonal rams. However, the animals need to be previously exposed to natural or artificial long days before responding to the melatonin treatment. The objective of this study was to test the effect of melatonin treatment on rams, initiated in mid May (end of spring) – when rams have already been exposed to some months of increasing day length, but not to artificial long day treatment on testicular size and semen characteristics. Sixteen rams (8 Texel and 8 Charollais) were treated with melatonin subcutaneous implants (REGULIN®) on 22 May and 20 June (spring/summer) (n=8) or remained untreated (n=8). Blood samples were taken from all rams over a 24-h period to determine the plasma melatonin concentration profile. The ram's testes were all measured four times at 2-week intervals, and testicular volume and scrotal circumference determined. Semen was collected using the artificial vagina at two occasions (end of June and end of August), when 5 ejaculates were obtained from each ram and analysed for semen volume and sperm concentration. The plasma melatonin levels in the melatonin-treated rams were significantly higher than for the untreated rams (P<0.01). During the dark phase of the day, the plasma melatonin concentrations were elevated (P<0.01) in the control, but not in the melatonin-treated rams. Scrotal circumference and testicular volume increased (P<0.001) from May to July (late spring to mid-summer) in both groups of rams, with no significant difference being detected between groups. Semen volume and sperm concentration increased (P<0.01) from June (summer) to July/September (summer/autumn) in both treatment groups. Melatonin treatment of the rams did not affect the semen volume or sperm concentration during any of the collection periods. Data suggest that the treatment of rams with melatonin implants initiated in late spring, without a priming period of long days preceding the treatment, is not sufficient stimulus to increase testis growth and sperm production.