Post-Diapause DNA Replication during Oogenesis in a Capital-Breeding Copepod.

In high-latitude environments where seasonal changes include periods of harsh conditions, many arthropods enter diapause, a period of dormancy that is hormonally regulated. Diapause is characterized by very low metabolism, resistance to environmental stress, and developmental arrest. It allows an organism to optimize the timing of reproduction by synchronizing offspring growth and development with periods of high food availability. In species that enter dormancy as pre-adults or adults, termination of diapause is marked by the resumption of physiological processes, an increase in metabolic rates and once transitioned into adulthood for females, the initiation of oogenesis. In many cases, individuals start feeding again and newly acquired resources become available to fuel egg production. However, in the subarctic capital-breeding copepod Neocalanus flemingeri, feeding is decoupled from oogenesis. Thus, optimizing reproduction limited by fixed resources such that all eggs are of high quality and fully-provisioned, requires regulation of the number of oocytes. However, it is unknown if and how this copepod limits oocyte formation. In this study, the phase in oocyte production by post-diapause females that involved DNA replication in the ovary and oviducts was examined using incubation in 5-Ethynyl-2'-deoxyuridine (EdU). Both oogonia and oocytes incorporated EdU, with the number of EdU-labeled cells peaking at 72 hours following diapause termination. Cell labeling with EdU remained high for two weeks, decreasing thereafter with no labeling detected by four weeks post diapause, and three to four weeks before spawning of the first clutch of eggs. The results suggest that oogenesis is sequential in N. flemingeri with formation of new oocytes starting within 24 hours of diapause termination and limited to the first few weeks. Lipid consumption during diapause was minimal and relatively modest initially. This early phase in the reproductive program precedes mid-oogenesis and vitellogenesis 2, when oocytes increase in size and accumulate yolk and lipid reserves. By limiting DNA replication to the initial phase, the females effectively separate oocyte production from oocyte provisioning. A sequential oogenesis is unlike the income-breeder strategy of most copepods in which oocytes at all stages of maturation are found concurrently in the reproductive structures.

Em ambientes de alta latitude, onde as mudanças sazonais incluem períodos de condições adversas, muitos artrópodes entram em diapausa, um período de dormência regulado por hormônios. A diapausa é caracterizada por metabolismo muito baixo, resistência ao estresse ambiental e interrupção do desenvolvimento. Ele permite que um organismo otimize a reprodução sincronizando o crescimento e desenvolvimento da prole com períodos de alta disponibilidade de alimentos. Em espécies que entram em dormência como pré-adultos ou adultos, o término da diapausa é marcado pela retomada dos processos fisiológicos, um aumento nas taxas metabólicas e o início da oogênese. Em muitos casos, os indivíduos começam a se alimentar novamente e os recursos recém-adquiridos ficam disponíveis para abastecer a produção de ovos. No oceano subártico, a alimentação do copépode Neocalanus flemingeri é dissociada da oogênese e a reprodução é limitada por recursos fixos obtidos durante a pré-diapausa. No entanto, não se sabe como este copépode regula a formação de ovócitos para garantir que todos os óvulos sejam de alta qualidade e bem fornecidos. Neste estudo, a fase de produção de oócitos por fêmeas pós-diapausa foi examinada usando incubação em 5-Etinil-2'-desoxiuridina (EdU) para caraterizar a replicação do DNA no ovário e nos ovidutos. Tanto as oogônias quanto os oócitos incorporaram EdU, com o número de células marcadas atingindo o pico 72 horas após o término da diapausa. A marcação das células com EdU permaneceu alta por duas semanas, diminuindo na terceira e cessando na quarta semana. Desova da primeira ninhada de ovos ocorre três a quatro semanas depois. Os resultados sugerem que a oogênese é sequencial em N. flemingeri com a formação de novos oócitos começando dentro de 24 horas após o término da diapausa e limitado às primeiras semanas. O consumo de lipídios durante a diapausa foi mínima e relativamente modesto inicialmente. Essa fase inicial do programa reprodutivo precede a vitelogênese 2, quando os ovócitos aumentam de tamanho e acumulam reservas de vitelo e lipídios. Ao limitar a replicação do DNA à fase inicial, as fêmeas efetivamente separam a produção de oócitos do seu fornecimento. Uma oogênese sequencial é diferente da estratégia de reprodução da maioria dos copépodes que mantem oócitos em todos estágios de maturação nas estruturas reprodutivas.

Non-starch polysaccharide degradation in the gastrointestinal tract of broiler chickens fed commercial-type diets supplemented with either a single dose of xylanase, a double dose of xylanase, or a cocktail of non-starch polysaccharide-degrading enzymes.

The aim of this study was to examine non-starch polysaccharide (NSP) degradation in the gastrointestinal tract of chickens fed a range of commercial-type diets supplemented with a commercial dose of xylanase, a double dose of xylanase or a cocktail of NSP - degrading enzymes. Cobb 500 broilers (n = 1,080) were fed 12 dietary treatments; 4 diets with differing primary grain sources (barley, corn, sorghum, and wheat) and three different enzyme treatments (commercial recommended dose of xylanase (16,000 BXU/kg), a double dose of xylanase (32,000 BXU/kg) or an NSP-degrading enzyme cocktail (xylanase, ß-glucanase, cellulase, pectinase, mannanase, galactanase, and arabinofuranosidase at recommended commercial levels). There were 108 pens, approximately 10 birds per pen, 9 replicates per dietary treatment. The diets were fed as 3 phases, starter (d 0-12), grower (d 12-23), and finisher (d 23-35). On bird age d 12, 23, and 35, performance (total pen body weight, feed intake, and feed conversion ratio corrected for mortality [cFCR]), litter and excreta dry matter content, and ileal and total tract soluble and insoluble NSP degradability and free oligosaccharide digestibility was determined. On d 35, the quantity of NSP in the gizzard, jejunum, ileum and excreta was determined. Results from this study showed that the double xylanase dose and NSP-ase cocktail had positive impacts on starter phase performance in birds fed the corn- and wheat-based diets. In the grower phase in birds fed the barley-based diet, these enzyme treatments improved cFCR and increased litter dry matter content. The NSP-ase cocktail had a negative impact on finisher phase cFCR in birds fed the sorghum-based diet. The double xylanase dose induced a positive impact on NSP degradability and free oligosaccharide digestibility. In conclusion, there appears to be advantages to feeding broilers a double xylanase dose, but lack of consistency when using an NSP-ase cocktail containing many enzymes.

Dietary soluble non-starch polysaccharide level and composition influences grower and finisher phase performance, excreta moisture content and total tract nutrient digestibility in broilers.

1. The aim of this study was to examine the impact of dietary soluble non-starch polysaccharide (sNSP) level and composition on grower and finisher phase performance, total tract nutrient digestibility and excreta moisture content in broiler chickens.2. Cobb 500 broilers (n = 1080) were fed 12 dietary treatments; four diets with differing primary grain sources (barley, corn, sorghum and wheat) and three different sNSP levels (low, medium and high). Diets were formulated to have similar protein and energy levels but differing sNSP levels, induced by manipulating the quantity of the ingredients in the diet. The diets were fed in three phases, starter (d 0-12), grower (d 12-23) and finisher (d 23-31).3. For birds aged d 23 and 31, total pen body weight and feed intake were determined, and fresh excreta and litter samples were collected per pen. Dry matter (DM) content was measured in the excreta and litter samples. Total tract DM digestibility, apparent metabolisable energy corrected to nitrogen (AMEn), and soluble and insoluble NSP and free oligosaccharide degradability were evaluated.4. In birds fed the sorghum- and corn-based diets, feeding high sNSP resulted in a lower cFCR at d 0-23 compared to low sNSP (P = 0.004 and P = 0.044, respectively). In birds fed the corn-based diet, feeding low sNSP resulted in the lowest litter DM but highest DM digestibility at d 23 (P = 0.045 and P < 0.001) and d 31 (P = 0.022 and P = 0.008). For all diets, degradability of sNSP was higher and insoluble NSP was lower when feeding low compared to high sNSP (P < 0.001). In birds fed the barley- and sorghum-based diets, AMEn was lower when feeding the low compared to high sNSP level (P < 0.001 and P = 0.016, respectively).6. Results from this study showed that level of dietary sNSP impacts broiler productive performance and nutrient utilisation.

Changes to Cobb 500 chick characteristics, bone ash, and residual yolk mineral reserves during time spent in the hatcher.

Previous work has identified an effect of hatch time on chick femur mineralization. This experiment assessed the impact of hatch time and a 24-h post-hatch unfed time period on chick bone mineralization and yolk mineral utilization. In early hatching chicks, yolk Mg, Zn, K, P, Fe, and Cu decreased by 40 to 50% over the 24-h post-hatch unfed time period, whereas yolk Ca and Na decreased by 25 to 40% (P = 0.026). Yolk Sr was intermediate, decreasing by 37%. Late hatching chicks which had been hatched for no more than 30 h had a higher femur bone ash percentage compared to early hatching chicks which had spent over a 30-hour sojourn unfed in the incubator (P = 0.013). These results indicate that removing chicks from the incubator within 30 h of their hatch is likely to benefit their femoral mineralization.

Changes to mineral levels in the yolk of meat chicken embryos during incubation.

A total of 864 settable Cobb 500 eggs were used to explore changes in yolk mineral content during incubation. Eggs were individually weighed and then placed in a commercial incubator. On embryonic day (ED) 0, 6.5, 13.5, and 17.5, 36 eggs were sampled and yolk weight and mineral content were determined. The concentration of iron (Fe), phosphorus (P), and zinc (Zn) declined (P < 0.05) from ED0 to ED17.5. The concentration of calcium (Ca), magnesium (Mg), and strontium (Sr) increased (P < 0.05) from ED0 to ED17.5. The concentration of copper (Cu), potassium (K), and sodium (Na) increased initially (ED0 to ED6.5) but declined thereafter. There was no change (P > 0.05) in the concentration of yolk manganese (Mn) from ED0 to ED17.5. Substantial changes in yolk mineral concentration occur during incubation and are presumably associated with mobilization of shell reserves and flux between albumen and yolk. These data may be useful in designing in ovo interventions, optimizing meat chicken breeder premix formulation or assembly of suitable neonatal or pre-starter diets for meat chicken chicks.

Why did severe feather pecking and cannibalism outbreaks occur? An unintended case study while investigating the effects of forage and stress on pullets during rearing.

This 2 × 2 factorial experiment aimed to investigate the effects of stimulating foraging behavior from wk 6 and imposed stress at wk 16 on the development of severe feather pecking (SFP) in chickens reared for free-range egg production. Non-beak-trimmed ISA Brown chicks were purchased at one day old and floor-reared on wood shavings. From wk 6, straw was provided daily in dispensers (Forage vs. No forage) to stimulate foraging. At wk 15, there were 16 pens of 50 pullets. "Stressors" were applied to half the pens in wk 16 via combined transport, relocation, and mixing (TRM) of pullets, simulating activities around transfer from the rearing to egg-laying farm (TRM vs. Not TRM). Range access was permitted from wk 21. Behavior, plumage damage (PD), growth, egg production, feed use, injuries, and mortalities were recorded, along with litter moisture and pH. In wk 26, an SFP outbreak commenced. By wk 34, PD was worse in south- than north-aspect pens (P < 0.001). Further, PD was more affected by side of the shed than the experimental treatments. In wk 30, an outbreak of injurious pecking (IP) commenced in the 4 TRM-treatment pens on the south side, with IP deaths almost 3 times more common in the Forage+TRM than No forage+TRM treatment. We suggest factors associated with a 13-day rainfall event that occurred in late winter predisposed the flock to SFP. While multiple factors such as winter cold, muddy ranges, damp floor litter with elevated pH, among others coincided, hens were clearly more impacted in south- than north-aspect pens. Once initiated, SFP possibly spread via social learning, and by wk 40, ∼98% of hens had PD. Interestingly, the IP outbreak was related to a combination of factors (stressors?), such as being housed in colder, damper south-aspect pens (note: southern hemisphere), having added Forage, and TRM. These unexpected relationships could help direct future research to identify the specific factors involved in the causation of SFP and IP/cannibalism outbreaks.

The contribution of metabolites to the rapid and potent down-regulation of rat cortical beta-adrenoceptors by the putative antidepressant sibutramine hydrochloride.

Sibutramine HCl is an inhibitor of the reuptake of monoamines with a pharmacological profile in rodents indicative of antidepressant activity. The secondary (BTS 54 354) and primary (BTS 54 505) amine metabolites of the tertiary amine sibutramine HCl exhibit similar in vivo pharmacological activity to the parent compound. Thus, each compound displays potent activity in acute behavioural models predictive of antidepressant effects and a comparable ability to inhibit the uptake of monoamines in vivo. In addition, BTS 54 354 and BTS 54 505 induce an equally rapid and potent down-regulation of cortical beta-adrenoceptors in the rat as sibutramine HCl. The secondary and primary amines are, however, considerably more active than sibutramine HCl as inhibitors of the uptake of noradrenaline, dopamine and 5-hydroxytryptamine in vitro. The potent inhibition of the reuptake of noradrenaline by the secondary and primary amine metabolites probably contributes to the rapid and potent down-regulation of beta-adrenoceptors in the rat, induced by the putative antidepressant sibutramine HCl.

Effects of various diuretic agents in the mouse.

Diuretic effects of seven orally-acting diuretic agents have been examined in the mouse. The following compounds, examples of various types of orally active compound available, produced their characteristic diuretic effects: bendrofluazide, frusemide, ethacrynic acid, acetazolamide, triamterene, aminophylline and Su 15049A. The diuretic effects of the various agents were demonstrated under both water and saline-loading conditions. After allowing for differences in baseline sodium excretion, all diuretics except acetazolamide caused a further enhancement of sodium excretion after saline-loading compared with water-loading tests. The mouse possesses several advantages over the more commonly used rat since the range of diuretic responsiveness is greater. These results suggest that the mouse is a suitable species for diuretic testing.