Effect of Light Duration and Variation on the Growth and Reproductive Performance in Breeder Geese.

This study was conducted to investigate the influence of different lighting regime on reproductive and growth performance of the pearl Guinea fowl (Numida meleagris) in Ghana. A total of five hundred (500) eggs were collected from an ongoing photoperiod experiment which were hatched and used for the study. The experimental birds were randomly assigned to a lighting programme of 12 hours of light: 12 hours of darkness (12L: 12D), 14 hours of light: 10 hours of darkness (14L: 10D), 16 hours of light: 8 hours of darkness (16L: 8D), and 18 hours of light: 6 hours of darkness (18L: 6D). A total of two-hundred and forty (240) day one old keets were divided into four treatment groups and each treatment was replicated three times in a Completely Randomize Design (CRD). The data collected were subjected to analysis of variance (ANOVA) using GenStat version 11.1 (2008). Least significant difference (LSD) at 5 % was used to separate the means. Results from the study revealed that, Percentage fertility, hatchability and hen-day egg production was highest (P

The desert locust, Schistocerca gregaria, plastically manipulates egg size by regulating both egg numbers and production rate according to population density

Egg and faecal pellet production rates, and their functional response to food and temperature, were measured for the Antarctic copepod Metridia gerlachei during January 1996. The study area comprised the Gerlache and Bransfield Straits and Drake Passage. The highest rates of “in situ” egg and faecal pellet production were observed in Gerlache stations, coinciding with chlorophyll a concentrations approaching food saturation levels. In the Bransfield and Drake stations, with very low chlorophyll concentrations, the rates of egg production were either very low, or no eggs were produced. Egg production rates, although well correlated with “in situ” chlorophyll values, appeared to be independent of food concentration on a short time-scale (24-h incubations), while the production of faecal pellets was closely related to food abundance in the same experiments. In general, the rates of egg production were low, even at food saturation, with a very high individual variability. Although in the majority of Gerlache stations about 50% of total chlorophyll a corresponded to the phytoplankton size-fraction >10 μm, M. gerlachei feeds preferentially on the <10-μm fraction. Temperature had no clear effects on egg production rate but had a significant effect on pellet production rates, with maximum values at 2.5°C. These features appear to agree with the reproductive strategy attributed to the species, based on a relatively low rate of egg production extended over a long reproductive period.

Measurements of hydrography, water transparency, chlorophyll (Chl)<it>a</it> and egg production rates (EPRs) by females of<it>Calanus marshallae</it> Frost, <it>Calanus pacificus</it> Brodsky, <it>Eucalanus californicus</it> Johnson, <it>Epilabidocera longipedata</it> Sato,<it>Pseudocalanus mimus</it> Frost, <it>Centropages abdominalis</it> Sato, <it>Acartia longiremis</it> Lilljerborg and <it>Paracalanus parvus</it> (Claus) were estimated at weekly intervals between 17 July and 2 September 1997. Production of eggs was determined in 24 h incubations to examine the effects of environmental variability on EPR, to detect the possibility of food limitation of EPR, and to evaluate the hypothesis that growth rates of females are size dependent. During the study, an anomalous downwelling event occurred, possibly in response to the 1997 El Ni&ntilde;o, which allowed us to determine how El Ni&ntilde;o events affect EPRs of coastal copepods. The larger copepods <it>Calanus marshallae, Calanus pacificus</it> and <it>Centropages abdominalis</it> showed the highest egg production and specific growth rates during the period of active upwelling (18 July-13 August, water temperatures 8-13<IMG SRC="/math/deg.gif">C, Chl <it>a</it> concentration 4.7-16.2 <IMG SRC="/math/mu.gif"> l^-1 and water transparency 3-5 m). After 27 August, the 1997-98 El Ni&ntilde;o arrived off Oregon, creating a downwelling situation. Upwelling winds ceased, the thermocline intensified, temperature and transparency increased (to &gt;18&deg;C and 16 m), and Chl<it>a</it> declined to &lt;2 &mgr;g l^-1. Densities of the common coastal species declined greatly as well. <it>Paracalanus parvus</it> became the dominant species, and <it>Eucalanus californicus, Epilabidocera longipedata</it> and <it>Corycaeus anglicus</it> became common in our samples. EPRs for the larger boreal copepods (<it>Calanus</it> and <it>Centropages</it>) declined greatly during El Ni&ntilde;o;; the smaller copepods,<it>Pseudocalanus mimus, A.longiremis</it> and<it>Paracalanus parvus</it>, showed low but relatively constant egg production and specific growth rates during both upwelling and downwelling events. Over the entire study period, only three species produced eggs at its maximum rate (24-28 eggs female^-1 day^-1),<it>Pseudocalanus mimus</it> which averaged 4 eggs day^-1. All other species had EPRs that were two or five times below their maximum EPR. Thus, EPRs were not related to body size, contrary to our expectations. Hatching success was variable among species. Values as low as 20-40% were found for all species at least once during the study period, suggesting that occasionally a substantial portion of egg production may not be viable.

1. Four Japanese quail lines were developed using 13 generations of reciprocal recurrent (lines AA and BB) or within-line selection (lines DD and EE) for high egg number until 98 d of age. In these lines and their reciprocal crosses, egg production, egg weight and mortality were monitored for up to 21 months to evaluate the impact of selection method and line origin on long-term production and heterosis. 2. Both hen-housed total egg number (EN) and hen-day egg laying rate (ELR) were consistently lower in recurrent lines than in lines under within-line selection: after 13 months of test, the difference was ‐47.1 eggs for EN and ‐20% for ELR%, whereas mortality was similar at around 20%. 3. Line EE was the best pure line for early egg production (55.2 eggs at 98 d of age) and also gave eggs which were consistently about 2 g larger than those from line DD but it had the highest overall mortality (78.5%) of all lines. On average, line DD laid 399 eggs (EN) over the whole experiment, 84 more than Line EE. 4. Crossbreds from the 2 types of pure lines and line DD had similar patterns and rates of egg production during the whole experiment, as indicated by the similarity of the curves adjusted for those lines by using the monomolecular model for EN and the modified compartmental model for ELR. 5. However, heterosis was higher from recurrent selection lines and it increased more with time than did heterosis from within-line selection lines.

Omnivory in the calanoid copepod Temora longicornis: feeding, egg production and egg hatching rates

The effect of photo-induced changes on egg production and reproductive performance of female guinea fowl was studied by exposing the birds to three photo-regimens, namely natural daylight all day for 12 weeks (NDL), 8 hours of light per day for 8 weeks (8L-16D) plus supplementary light for 16 hours per day for 4 weeks (16L-8D) (RSL), and provided natural daylight all day for 8 weeks plus supplementary light at 16 hours per day for 4 weeks (SL). Weight gain during the pre-laying period was similar (P&gt;0.05) in all the treatment groups between 20-36 weeks of age. The reverse was the case during the laying period between 36-52 weeks, which coincided with the age at sexual maturity. Feed intake was similar (P&gt;0.05) for the NDL and SL groups during the pre-laying period but the RSL group had significantly lower (P&lt;0.05) feed intake than the others. Overall laying mortality was lowest in the RSL birds. There was no significant difference (P&gt;0.05) in body weight for all the groups. Age at first egg was significantly lower (P&lt;0.05) in the RSL (207 d) than in the NDL (249 d) and SL (235 d) birds which were similar (P&gt;0.05). The guinea fowls which received 8 weeks of restricted light (RSL) responded more rapidly in terms of day-to-first-egg after exposure to 16 hours of light and achieved significantly higher (P&lt;0.05) level of egg production than the other two groups. The overall economy of production, in terms of cost, revealed that RSL birds performed better than the NDL and SL, in that it cost N36.58 and 127.05 more to produce each NDL and SL guinea fowl at point of lay respectively. The results indicate that different light regimes altered the time during which egg production response took place and apparently affected the genetic potentials of the groups with regard to egg mass and total number of eggs laid during the period covered by this trial.

The rates of egg production of individually reared females of Centropages typicus have been observed from the moulting C5-adult to death under constant conditions of food (10 000 cells mh1 of Hymenomonas elongatd) and temperature (15 and 20°C). Preliminary experiments showed that virgin females could produce unfecunded eggs, but that the distinctive spines of the eggs of Ctypicus were only obtained after fecundation occurred. High and continuous egg production needs several matings, and the following experiments were run with a couple. In all experiments, both males and females fed and produced faecal pellets. The females show a high variability in spawning life periods, in spawning rhythms, in daily rates and, consequently, in cumulated numbers of eggs spawned during their life. The highest daily rates of egg production were obtained in the first half of the female's life, and were as high at 20°C as at 15°C. Nevertheless, the females survived longer at 15°C than at 20°C, and finally produced 47.6% more eggs during their whole life at 15°C than at 20°C, which can be partially due to the difference in size (almost 10% bigger at 15°C than at 20°C). The production of faecal pellets occurred during the whole of life and was more regular than egg production, with a maximum daily rate in the first part of life, and showed a decrease until death. The decline in daily egg production with age was parallel to the decrease in daily faecal pellet production. The daily pro- duction of faecal pellets was higher at 15°C than at 20°C. At 20°C, a good correlation was observed between the total egg production per female and the total faecal pellet production per female. The individual-based egg production rates of our experiments have been compared with rates obtained in different conditions by several authors, and were lower than in other published studies, probably due to the food offered. We emphasize the difficulties of comparing results which have been obtained for the entire life of the females with those based on daily egg production. The total egg production of a female is an important parameter in regard to the population dynamics because it fixes the maximal rate of losses (mortality plus dispersion) for which a population can continue to develop.

The hypothalamic-pituitary-ovarian (HPO) axis regulates the breeding process cycle of laying hens. However, the key regulatory genes of the HPO axis and pathways that drive chicken egg laying performance remain elusive. A total of 856 Chinese Luhua chicken was raised and the highest two hundred and the lowest two hundred chicken egg production were considered as high egg production (HEP) and low egg production (LEP) according to the total egg number at 300 days of age, respectively. RNA-seq sequencing (RNA-Seq) was conducted to explore the chicken transcriptome from the hypothalamus, pituitary gland and ovary tissue of 6 Chinese Luhua chicken with 3 high and low-rate egg production. In total, 76.09 Gb RNA-seq sequences were generated from 15 libraries with an average of 5.07 Gb for each library. Further analysis showed that 414, 356 and 10 differentially expressed genes (DEGs) were identified in pituitary gland, ovary and hypothalamus between HEP and LEP chickens, respectively. In pituitary gland, DEGs were involve in regulation of cellular glucose homeostasis, Ras protein signal transduction, negative regulation of hormone secretion. In Ovary DEGs were mainly involved in embryonic organ development, regulation of canonical Wnt signaling, response to peptide hormone. Our study identified DEGs that regulate mTOR signaling pathway, Jak-STAT signaling pathway, Tryptophan metabolism and PI3K-Akt signaling pathways at HPO-axis in laying hens. These important data contribute to improve our understanding of reproductive biology of chicken and isolating effective molecular markers that can be used for genetic selection in Chinese domestic Luhua chicken.

Egg production and development rates of Centropages typicus (Kroyer) were studied in the laboratory under carying food and temperature conditions. Egg production rates in the laboratory ranged from 0 to 124 eggs female-1 d-1 and increased with food concentration up to a critical food concentration (Pc) above which egg production was constant. Egg production rates were influenced by temperature, with more eggs being produced at 15°C than at 10°C. Thalassiosira weisflogii and Prorocentrum micans were determined to be equally capable of supporting egg production at concentrations above Pc at 15°C. Rate of egg production was independent of adult female size when food and temperature were constant. Egg production rates of freshly captured females ranged from 0 to 188 eggs female-1 d-1 and were higher in April and May than in June or July. Hatching rates of eggs increased with increased temperature; 95% of the eggs at 15°C hatched within 48 h, while only 8% of the eggs at 10°C hatched within 48 h. Development rates, determined at 10°C in excess concentrations of T. weisflogii, were 23.0 d from egg release to copepodid state I, 27.0 d to stage II, 29.5 d to stage III, 32.2 d to stage IV, 38.5 d to stage V and 49 d to adulthood based on the average time required for 50% of the organisms in an experiment to attain a given stage. Adult males were usually observed 2 to 4 d before adult females, and therefore have a slightly faster rate of development. The effects of temperature, food type and food concentration on egg production and the seasonal appearances of diatoms in the New York Bight may account for the observed seasonal cycles in abundance of C. typicus in these coastal waters.

We studied the allocation of total egg mass to size and number in the carabid beetle Notiophilus biguttatus F. at several temperature and day length regimes. Eggs increase in number and decrease in size with increasing (constant) temperature. Day length interacts with temperature: at short day the effect of temperature on size and number of eggs is weaker than at long day. In diurnally fluctuating temperature regimes, egg size is affected disproportionately by the high temperature period. All treatments, however, are similar in affecting number and size of eggs in an opposite direction. Consequently, egg size is explained to a high degree by egg production rate. The relationship between size and number of eggs among treatments is furthermore characterized by a decrease in egg size with an increase in total egg mass production. Within treatments, rate of egg production and egg size are negatively correlated among females in the low-temperature groups but not in the high-temperature groups; the correlations among females are also characterized by a decrease in egg size, with an increase in total egg mass production. Hence, possible trade-offs between size and number of eggs are masked by phenotypic variation in reproductive effort. The observations enable us to propose a simple conceptual model that explains the within-treatment correlation by the same causal factor as the negative relationship among treatment means.

We studied the allocation of total egg mass to size and number in the carabid beetle Notiophilus biguttatus F. at several temperature and day length regimes. Eggs increase in number and decrease in size with increasing (constant) temperature. Day length interacts with temperature: at short day the effect of temperature on size and number of eggs is weaker than at long day. In diurnally fluctuating temperature regimes, egg size is affected disproportionately by the high temperature period. All treatments, however, are similar in affecting number and size of eggs in an opposite direction. Consequently, egg size is explained to a high degree by egg production rate. The relationship between size and number of eggs among treatments is furthermore characterized by a decrease in egg size with an increase in total egg mass production. Within treatments, rate of egg production and egg size are negatively correlated among females in the low‐temperature groups but not in the high‐temperature groups; the correlations among females are also characterized by a decrease in egg size, with an increase in total egg mass production. Hence, possible trade‐offs between size and number of eggs are masked by phenotypic variation in reproductive effort. The observations enable us to propose a simple conceptual model that explains the within‐treatment correlation by the same causal factor as the negative relationship among treatment means.

This study evaluated effects of photoperiod treatments on slaughter and carcass traits, meat quality, indicators of oxidative stress, and heat shock protein 70 (Hsp70) levels of lung and heart tissues in broilers. Five hundred Ross 308 broiler chicks were used. The treatments consisted of 23 hours of continuous light and one hour of darkness (23L1D), four hours of light followed by two hours of darkness (4L2D), eight hours of light and four hours of darkness (8L4D), and 16 hours of light and eight hours of darkness (16L8D). After 42 days, two birds from each replicate were slaughtered. Birds that had been subjected to 16L8D had lower slaughter, carcass, and breast weights than the other treatments. Significant correlations were observed for slaughter, carcass and breast weights and white stripe. At 10 min post mortem, the pH of the breast was the highest in 23L1D. Breasts from birds subjected to 23L1D and 16L8D had most fat and least protein, while white striping was not different among treatments. The 4L2D treatment resulted in the highest lung glutathione (GSH) concentration. Malondialdehyde (MDA) and GSH concentrations in the heart tissues of broilers from 8L4D and 4L2D were greater than those from 23L1D and 16:8. Glutathione peroxidase (GSH-Px) and superoxide dismutase concentrations were greatest for birds subjected to 16L8D. Heat shock protein 70 was lowest in lung and heart from birds subjected to 8L4D. Thus, shorter and more frequent periods of darkness can be recommended for welfare with little compromise in performance. Keywords: carcass quality, heat shock protein 70, oxidative stress, white stripe

Effects of short light regimes and lower dietary protein content on the reproductive performance of White Roman geese in an environment-controlled house

Species belonging to the same guild (i.e. sharing the same resources) can reduce the negative effects of resource competition through niche partitioning. Coexisting species may differ in their resource exploitation and in the associated allocation of nutrients, depending on their resource niche. Trade-offs in nutrient allocation, such as between reproduction and survival, or between early and late reproduction, are moderated by the abundance and distribution of resources. In this study we investigate differences in larval resource exploitation and adult reproductive strategy of two sympatric aphid parasitoids sharing a common host. The habitat specialist Aphidius rhopalosiphi and the generalist Aphidius avenae occur in cereal crops of Western Europe, where both species attack the major host resource: the grain aphid Sitobion avenae. For this purpose, we measured their acquisition of capital lipid resources, their age-specific fecundity and reproductive effort, their life span and their metabolic rate. We found that these species do not differ neither in larval lipid accumulation nor in the number of eggs at emergence and the timing of egg production, but diverge in other adult reproductive strategies. The rate of adult egg production was higher in A. rhopalosiphi than A. avenae, but at the expense of producing smaller eggs. Throughout adult life, reproductive effort was higher in A. avenae, perhaps facilitated by its higher metabolic rate than A. rhopalosiphi. The divergence between species in life history syndromes likely reflects their adaptations to their resource niche. A high egg production probably allows the specialist A. rhopalosiphi to exploit more S. avenae individuals in cereal crops, while the generalist A. avenae because of its variety of hosts, maximizes the investment per egg but at the expense of a lower lifespan. Our results suggest that differential resource allocation may be a more common pattern that promotes coexistence of species within a guild.