Growth Rate Of Chicks Research Articles

The metabolic rate of cultured muscle cells from hybrid Coturnix quail is intermediate to that of muscle cells from fast-growing and slow-growing Coturnix quail.

Growth rate is a fundamental parameter of an organism's life history and varies 30-fold across bird species. To explore how whole-organism growth rate and the metabolic rate of cultured muscle cells are connected, two lines of Japanese quail (Coturnix coturnix japonica), one that had been artificially selected for fast growth for over 60 generations and a control line were used to culture myoblasts. In line with previous work, myoblasts from the fast growth line had significantly higher rates of oxygen consumption, glycolytic flux, and higher mitochondrial volume than myoblasts from the control line, indicating that an increase in growth rate is associated with a concomitant increase in cellular metabolic rates and that mitochondrial density contributes to the differences in rates of metabolism between the lines. We reared chicks from two hybrid lines with reciprocal parental configurations for growth rate to explore the effect of maternally inherited mitochondrial DNA on rates of growth and metabolism. Growth rates of chicks, cellular basal oxygen consumption, glycolytic flux, and mitochondrial volume in myoblasts from chicks from both reciprocal crosses were intermediate to the fast and control lines. This indicates that genes in the nucleus have a strong influence on metabolic rates at the cellular level, compared with maternally inherited mitochondrial DNA.

Parental Nesting Behavior, Chick Growth and Breeding Success of Shoebills(Balaeniceps rex)in the Bangweulu Wetlands, Zambia

Shoebills (Balaeniceps rex) breed in central-eastern Africa with a world population of only 5,000-8,000 individuals. To provide protection to this threatened species, conservationists need a better understanding about Shoebill foraging and breeding ecology, their habitat use and their distribution. For this study, nest attendance and prey provisioning were recorded with nest cameras for Shoebills in the Bangweulu Wetlands in Zambia in 2012 and 2013. Chick growth and breeding success were monitored at the same time. Parental attendance was constant in the first 40 days of chick rearing, with attending parents only leaving the nest briefly to collect water for cooling the chicks or to collect material to maintain the nest. Attendance decreased as chicks aged, but prey provisioning remained constant throughout the nestling stage at 1.2 deliveries per day. Feeding peaked during the early and late morning. Chick growth rates were as expected given the size of the species, and chicks reached a fledging mass of approximately 5.7 kg. During 2011, breeding success was particularly low (20%, n = 10 nests) due to high levels of human disturbance, with chicks being removed from nests. Parents fledged 0.89 chicks per nest (n = 11 nests) when nests were actively protected from human disturbance and theft in 2012–2013. These findings could be useful for formulating guidelines for sustainable tourism to minimize disturbance and optimize breeding success in Shoebill populations.

Immunoreactive cortisone in droppings reflect stress levels, diet and growth rate of gull-billed tern chicks

Blood levels of corticosterone have been traditionally analyzed to assess stress levels in birds; however, measuring steroid hormone metabolites in feces and droppings has gained much interest as a noninvasive technique successfully used for such purposed in vertebrates. Diet may affect these fecal metabolite levels (e.g., due to nutritional stress), however, this variable has not been taken into account in studies with chicks despite the great dietary flexibility of many avian species. In this study, we addressed for the first time this key issue and validated the technique in wild gull-billed tern chicks (Gelochelidon nilotica). Several enzyme immunoassays were used to determine the most appropriate test to measure the stress response. Subsequently, we performed an experiment in captivity to assess adrenocortical activity in gull-billed tern chicks fed with two diets: piscivorous vs. insectivorous. Finally, the relation between the chicks’ growth rate and excreted immunoreactive glucocorticoid metabolites (EGMs) was also evaluated. We found the immunoreactive cortisone metabolites to be a good index of stress (as being an index of adrenocortical reactivity) in chicks of this species. Fish-fed chicks had higher levels of cortisone metabolites when comparing both concentration and total daily excreted metabolites. Within each treatment diet, cortisone metabolite levels and growth rates were negatively correlated. These findings suggest that the diet should be considered when using this technique for comparative purposes and highlight the trade-off between stress levels and chicks growth rates.

Nutritive effect of cabbage (<i>Brassica oleracea</i>) on growth, obesity, lipidaemia and haematology in broiler and pullet chickens

Efficacy of cabbage (Brassica oleracea) for ameliorating the adverse metabolic syndrome side-effects of genetically improved growth rate in chickens was examined. Sixty-four (64) day-old birds (32 Marshall Broilers and 32 Harco Black Pullets) were randomly assigned to groups of eight genotype-matched birds in a 2-factor layout within a Completely Randomized Design (CRD). Within genotype, each group was randomly assigned one of four diets (basal/control diet containing 0% cabbage, and, basal diet supplemented with 3%, 6% or 12% cabbage) for 4 weeks. All birds were fed an un-supplemented Broiler finisher diet from week 4 - 8. Bodyweight and Body Mass Index (BMI) were determined weekly. Blood Packed Cell Volume (PCV), Haemoglobin (Hb), White Blood Cells (WBC), Red Blood Cells (RBC), neutrophils, lymphocytes, monocytes, basophils and eosinophils), Total serum Cholesterol (TC), High Density Lipoprotein (HDL) and Low Density Lipoprotein (LDL) were determined at age 4 weeks. Irrespective of diet or age, Broilers exhibited significantly greater (p<0.05) body weight, adiposity, and lipidaemia than Pullets, and no interactions between cabbage and genotype were observed for the same traits. Dietary cabbage at 3%, irrespective of genotype significantly (p<0.05) improved body weight beyond week 5 while no significant effect was observed on body fatness as measured by BMI. Cabbage supplementation suppressed broiler eosinophil levels, indicating effects on mediators of innate immune surveillance, but did not influence any other blood haematological parameter, though Broilers exhibited higher (p<0.05) total WBC count and proportion (%) of WBC represented by neutrophils, basophils and eosinophils. In Contrast, Pullets exhibited higher RBC, PCV, and Hb, and lymphocyte and monocyte differential counts. Dietary Cabbage had a nutrigenetic effect on cholesterol: Reduced TC and LDL in Broilers in contrast to its effect in increasing the same lipids in Pullets. Cabbage however lowered HDL Cholesterol (p<0.05) in both genotypes, though the threshold of effect was higher (12%) in Pullets (3%). Thus Cabbage is effective in lowering heart disease risk through lowering of lipidaemia in Broilers, and improves bodyweight at market age (7-8 weeks) at 3% dietary supplementation level.KEYWORDS: Cabbage, Broiler, Pullet, Nutritive, Metabolic syndrome.

Effect of feed type on performance of pullet chicks in Nsukka local government area of Enugu state, Nigeria

A five-week study was conducted to determine the effect of feed type on performance of pullet chicks in Nsukka Local Government Area of Enugu State, Nigeria. One hundred and twenty 4-week old pullet chicks (ISA Brown strain) averaging 100.03g body weight were randomly divided into 4 groups of 30 birds each. Each group was randomly assigned to one of four experimental diets (self-compounded starter diet (C) and three commercial starter diets-A, B and D, respectively), using a completely randomized design (CRD). Each diet constituted a treatment. Each treatment was replicated 2 times with 15 birds per replicate. Feed and water were supplied ad libitum. There were significant (P<0.05) differences among treatments in average daily weight gain, average daily feed intake, feed conversion ratio, protein intake, protein efficiency ratio and final body weight. Birds on treatment C (self-compounded feed) had significantly (P<0.05) higher final body weight and average daily weight gain than those on treatments A, B and D (commercial feeds), while birds on treatment A had significantly (P<0.05) higher average daily feed intake than birds on other treatments. Birds on treatment C had the least FCR value and higher (P<0.05) protein efficiency ratio (PER) value. Birds on treatment C had the least (P<0.05) cost of daily feed intake and total feed intake and cost of feed per kg weight gain. It was concluded that diet C (self-compounded feed) was superior to the commercial feeds because it supported the highest growth rate of chicks and its use resulted in drastic reduction in feed cost per kg weight gain.Keywords: Feed type, growth performance, pullet chicks, Nsukka Local Government Area, Enugu State, Nigeria

Arctic warming: nonlinear impacts of sea-ice and glacier melt on seabird foraging.

Arctic climate change has profound impacts on the cryosphere, notably via shrinking sea-ice cover and retreating glaciers, and it is essential to evaluate and forecast the ecological consequences of such changes. We studied zooplankton-feeding little auks (Alle alle), a key sentinel species of the Arctic, at their northernmost breeding site in Franz-Josef Land (80°N), Russian Arctic. We tested the hypothesis that little auks still benefit from pristine arctic environmental conditions in this remote area. To this end, we analysed remote sensing data on sea-ice and coastal glacier dynamics collected in our study area across 1979-2013. Further, we recorded little auk foraging behaviour using miniature electronic tags attached to the birds in the summer of 2013, and compared it with similar data collected at three localities across the Atlantic Arctic. We also compared current and historical data on Franz-Josef Land little auk diet, morphometrics and chick growth curves. Our analyses reveal that summer sea-ice retreated markedly during the last decade, leaving the Franz-Josef Land archipelago virtually sea-ice free each summer since 2005. This had a profound impact on little auk foraging, which lost their sea-ice-associated prey. Concomitantly, large coastal glaciers retreated rapidly, releasing large volumes of melt water. Zooplankton is stunned by cold and osmotic shock at the boundary between glacier melt and coastal waters, creating new foraging hotspots for little auks. Birds therefore switched from foraging at distant ice-edge localities, to highly profitable feeding at glacier melt-water fronts within <5km of their breeding site. Through this behavioural plasticity, little auks maintained their chick growth rates, but showed a 4% decrease in adult body mass. Our study demonstrates that arctic cryosphere changes may have antagonistic ecological consequences on coastal trophic flow. Such nonlinear responses complicate modelling exercises of current and future polar ecosystem dynamics.

Atlantic Puffin Fratercula arctica chick growth in relation to food load composition

Despite a long-term (1989-2013) reduction in size of fish brought to Atlantic Puffin Fratercula arctica chicks and a parallel increase in numbers of fish in the food loads, there was no evidence of changes in chick growth rates at Hornøya, NE Norway. Recent declines in chick survival and cessation in population growth suggest, however, that environmental conditions have changed to an extent that breeding success is now compromised.

Comparative osteohistology of Hesperornis with reference to pygoscelid penguins: the effects of climate and behaviour on avian bone microstructure.

The broad biogeographic distribution of Hesperornis fossils in Late Cretaceous Western Interior Seaway deposits has prompted questions about whether they endured polar winters or migrated between mid- and high latitudes. Here, we compare microstructures of hesperornithiform long bones from Kansas and the Arctic to investigate whether migration or Late Cretaceous polar climate affected bone growth. We also examine modern penguin bones to determine how migration and climate may influence bone growth in birds with known behaviours. Histological analysis of hesperornithiform samples reveals continuous bone deposition throughout the cortex, plus an outer circumferential layer in adults. No cyclic growth marks, zonation or differences in vasculature are apparent in the Hesperornis specimens. Comparatively, migratory Adélie and chinstrap penguin bones show no zonation or changes in microstructure, suggesting that migration is not necessarily recorded in avian bone microstructure. Non-migratory gentoos show evidence of rapid bone growth possibly associated with increased chick growth rates in high-latitude populations and large body size. The absence of histological evidence for migration in extinct Hesperornis and extant pygoscelid penguins may reflect that these birds reached skeletal maturity before migration or overwintering. This underscores the challenges of using bone microstructure to infer the effects of behaviour and climate on avian growth.

Seabird diet changes in northern Hudson Bay, 1981-2013, reflect the availability of schooling prey

Ongoing climate change is altering Arctic marine ecosystems with major conse- quences for food-webs. Seabirds, by foraging over large marine areas but returning regularly to their breeding colonies, provide a good medium for tracking such changes. We studied the prey delivered to nestling thick-billed murres Uria lomvia at a colony in northern Hudson Bay, Canada, over the period 1981−2013. During that period, ice conditions in the region altered substantially, with earlier break-up and clearance. This change was not gradual but mainly occurred in the mid- 1990s. Breeding chronology also advanced, but not as fast as early summer ice clearance advanced. Ice conditions strongly affected diet, presumably reflecting the change in the timing of breeding relative to ice clearance. Of the dominant species in the diet, the proportion of Arctic cod Boreogadus saida decreased and the proportion of capelin Mallotus villosus increased over the 33 yr period, even after ice effects were taken into account, suggesting a progressive and cumu- lative effect of environmental change on the marine community. Those cumulative changes were manifested primarily in the diet representation of the most frequent taxa (cod and capelin), with variation in secondary diet components being driven by the availability of the dominant taxa. Diet diversity, representing an increase in the proportion of benthic fish (stichaeids, zoarcids, pholids and sculpins) and invertebrates (squid, amphipods and crustaceans), increased when ice cover was low, and hatching was late relative to ice break-up. Chick growth rates were low when the proportion of benthic fish was high. Hence, although it appears that growth rates are influenced by diet composition, it is more likely that they reflect the availability of the dominant schooling prey species, rather than any nutritional deficiency in benthic species.

Windscapes shape seabird instantaneous energy costs but adult behavior buffers impact on offspring.

BackgroundWindscapes affect energy costs for flying animals, but animals can adjust their behavior to accommodate wind-induced energy costs. Theory predicts that flying animals should decrease air speed to compensate for increased tailwind speed and increase air speed to compensate for increased crosswind speed. In addition, animals are expected to vary their foraging effort in time and space to maximize energy efficiency across variable windscapes.ResultsWe examined the influence of wind on seabird (thick-billed murre Uria lomvia and black-legged kittiwake Rissa tridactyla) foraging behavior. Airspeed and mechanical flight costs (dynamic body acceleration and wing beat frequency) increased with headwind speed during commuting flights. As predicted, birds adjusted their airspeed to compensate for crosswinds and to reduce the effect of a headwind, but they could not completely compensate for the latter. As we were able to account for the effect of sampling frequency and wind speed, we accurately estimated commuting flight speed with no wind as 16.6 ms?1 (murres) and 10.6 ms?1 (kittiwakes). High winds decreased delivery rates of schooling fish (murres), energy (murres) and food (kittiwakes) but did not impact daily energy expenditure or chick growth rates. During high winds, murres switched from feeding their offspring with schooling fish, which required substantial above-water searching, to amphipods, which required less above-water searching.ConclusionsAdults buffered the adverse effect of high winds on chick growth rates by switching to other food sources during windy days or increasing food delivery rates when weather improved.

Productivity and Chick Growth Rates of Royal Tern (Thalasseus maximus) and Sandwich Tern (Thalasseus sandvicensis) on the Isles Dernieres Barrier Island Refuge, Louisiana

Abstract. Barrier islands in Louisiana and elsewhere in the northern Gulf of Mexico region provide valuable breeding habitat for numerous waterbird species; however, these islands are also deteriorating at an alarming rate. Management and conservation of waterbird species in these dynamic environments require a better understanding of the breeding biology for northern Gulf of Mexico populations. Productivity parameters were investigated for Royal (Thalasseus maximus) and Sandwich (T. sandvicensis) terns at the Isles Dernieres Barrier Island Refuge in Terrebonne Parish, Louisiana, during the 2009 and 2010 breeding seasons. Mean hatching success for Royal Tern was 77% (n = 169 nests), while Sandwich Tern hatching success was 75% (n = 130 nests). For both Royal and Sandwich terns, the estimated probability that a chick survived from hatching to fledging age was 55% (n = 630 nestlings). Overall, estimated breeding success for Royal and Sandwich terns was 42.3% and 41%, respectively. Chick growth rates were si...

The effect of parental age, experience and historical reproductive success on wandering albatross (Diomedea exulans) chick growth and survival

Growth and survival of altricial young are influenced by their parents’ abilities to invest in a breeding attempt. As a result, chick growth and survival in one breeding season may be indicative of their parents’ long-term reproductive potential. To determine whether variation in long-term reproductive success is driven by differential breeding investment, parental care and chick growth in wandering albatrosses (Diomedea exulans) were correlated with parental historical reproductive success. Effects of age and breeding experience (determined from past breeding attempts) and pre-laying body condition (mass–size indices) on chick growth and survival also were tested. Longer brooding of chicks increased their survival, but length of chick brooding did not differ between historically unproductive and successful breeders. Past reproductive success also was not correlated with chick growth rates or fledging mass or size. Chick brooding period, chick growth rates, final mass and size were independent of parental body condition. Older and more experienced parents brooded chicks for longer and their chicks grew faster, supporting previous findings that breeding competence is a learnt skill. Chick care and growth characteristics differed more between than within pairs, suggesting that differences in these characteristics are driven by variation among pairs.

Maternal effects underlie ageing costs of growth in the zebra finch (Taeniopygia guttata).

Maternal effects provide a mechanism to adapt offspring phenotype and optimize the mother’s fitness to current environmental conditions. Transferring steroids to the yolk is one way mothers can translate environmental information into potential adaptive signals for offspring. However, maternally-derived hormones might also have adverse effects for offspring. For example, recent data in zebra finch chicks suggested that ageing related-processes (i.e. oxidative stress and telomere loss) were increased after egg-injection of corticosterone (CORT). Still, we have few experimental data describing the effect of maternal effects on the growth-ageing trade-off in offspring. Here, we chronically treated pre-laying zebra finch females (Taeniopygia guttata) with 17-β-estradiol (E2) or CORT, and followed offspring growth and cellular ageing rates (oxidative stress and telomere loss). CORT treatment decreased growth rate in male chicks and increased rate of telomere loss in mothers and female offspring. E2 increased body mass gain in male offspring, while reducing oxidative stress in both sexes but without affecting telomere loss. Since shorter telomeres were previously found to be a proxy of individual lifespan in zebra finches, maternal effects may, through pleiotropic effects, be important determinants of offspring life-expectancy by modulating ageing rate during embryo and post-natal growth.

Elevation impacts the balance between growth and oxidative stress in coal tits.

The short favorable period of time available for the growth in seasonal environments could constrain the resources allocation between growth and other life-history traits, and the short-term fitness benefits of increased growth rate may prevail over other functions. Accelerated growth rates have been associated with long-term deleterious consequences (e.g., decreased lifespan), and recently oxidative stress (the imbalance between pro-oxidants generation and antioxidant defenses) has been suggested as a mediator of these effects. Here, we examined the impact of elevation on growth rate and self-maintenance parameters (resting metabolism, oxidative damage, and antioxidant defenses) of coal tit chicks (Periparus ater). We predicted that the shorter favorable season at the higher-elevation site could lead to a reallocation of resources towards growth at the expense of self-maintenance processes. We found that chicks at high elevation grew significantly faster in terms of body mass and body size. Chicks from the high-elevation site presented higher resting metabolism, higher oxidative damage level, but similar antioxidant defenses, compared to low-elevation chicks. Interestingly, the chicks exhibiting the better antioxidant defenses at 7 days were also those with the highest resting metabolic rate, and the chicks that grew at the faster rate within the high-elevation site were those with the highest levels of oxidative damage on DNA. Our study supports the idea that increasing elevation leads to a higher growth rate in coal tit chicks, possibly in response to a shorter favorable season. In accordance with life-history theory, a bigger investment in growth was done at the expense of body maintenance, at least in terms of oxidative stress.

Effects of dietary clays on performance and intestinal mucus barrier of broiler chicks challenged with Salmonella enterica serovar Typhimurium and on goblet cell function in vitro

In vivo and in vitro experiments were conducted to test for beneficial effects of dietary clays on broiler chicks challenged with Salmonella enterica serovar Typhimurium and to explore potential mechanisms. First, two hundred forty 1-d-old male broilers (initial BW: 41.6 ± 0.4 g) were allotted in a 2 × 4 factorial arrangement in a randomized complete block design. There were 2 infection treatments (with or without Salmonella) and 4 diets: basal (BAS), 0.3% smectite A (SMA), 0.3% smectite B, and 0.3% zeolite. The Salmonella reduced (P < 0.05) the growth rate of chicks fed the BAS, and feeding clay largely restored it (challenge × diet interaction, P < 0.05). Goblet cell number and size were increased (P < 0.05) by Salmonella in chicks fed the BAS and were reduced (P < 0.05) in Salmonella- challenged chicks by feeding SMA. Villus height was reduced by the Salmonella challenge in the chicks fed dietary clays (P < 0.01) but not in chicks fed the BAS (interaction P < 0.05). A human adenocarcinoma cell line (LS174T) was cultured in vitro in 3 separate experiments in the absence or presence of 3 concentrations (0.05, 0.10, and 0.50%) of SMA. Expression of mucin 2 (MUC2), resistin-like molecule β (RELMß), and trefoil factor 3 (TFF3) were determined by real-time reverse-transcription PCR. The expression of RELMβ was increased and expression of MUC2 was reduced (P < 0.05) by 0.10% SMA. Also, LS174T cells were cultured without or with SMA (0.05 and 0.10%) and the medium and cell lysate were analyzed for RELMβ using an immunoblot assay. Protein expression of RELMß in the cell lysate was reduced (P < 0.05) by SMA addition but increased in the medium, indicating that SMA increased secretion of RELMß, thus depleting the cell and concentrating this protein in the medium. In conclusion, the dietary clays restored the growth depression caused by Salmonella, and changes in goblet cell function may contribute to the benefits of one of the clays, specifically SMA.

An experimental study measuring the effects of a tarsus-mounted tracking device on the behaviour of a small pursuit-diving seabird

Miniaturized tracking devices are taking a rapidly increasing role in studies measuring animal movement and other aspects of behaviour, especially for wide-ranging species such as seabirds that are difficult to observe otherwise. A crucial, but questionable criterion of such migration research is assuming that effects of tracking devices on animal behaviour are negligible, to ensure results of tracking studies are biologically relevant. To address this concern, we experimentally quantified effects of a 2 g (ca. 1.1% of body mass) geolocation device on crested auklet (Aethia cristatella) behaviour, including return rate, activity on the colony surface, and measures of reproductive performance in a two-year, two-part field study. In experiment 1, we fitted tracking devices (or identical dummy devices) to one mate of a breeding pair in nesting crevices, to quantify effects on reproductive performance and nest fidelity. In experiment 2, we assigned dummy devices to birds captured at the colony site surface, to quantify effects on social activity, return rate and provisioning behaviour. For birds tagged in crevices, we detected no effect on fledging success, or chick growth rate (mass and wing length). However, mass at fledging age of chicks provisioned with one tagged parent was significantly lower than control, and low nest site fidelity (compared to control birds) was observed for tagged birds. Individuals tagged on the colony surface showed significantly reduced colony surface activity, return rates and provisioning behaviour. This study shows strong ‘observer effects’ of an attached device well below the recommended size limit for wildlife tagging. Future studies should both quantify effects of attached devices and consider the biological relevance of measures of the behaviour of interest.

The role of landscape features and density dependence in growth and fledging rates of Piping Plovers in North Dakota, USA

ABSTRACT For species with precocial young, survival from hatching to fledging is a key factor influencing recruitment. Furthermore, growth rates of precocial chicks are an indicator of forage quality and habitat suitability of brood-rearing areas. We examined how growth and fledging rates of Piping Plover (Charadrius melodus) chicks were influenced by landscape features, such as hatchling density (hatchlings per hectare of remotely sensed habitat [H ha−1]), island vs. mainland, and wind fetch (exposure to waves) at 2-km segments (n = 15) of Lake Sakakawea, North Dakota, during 2007–2008. Hatchling growth was comparable with published estimates for other habitats. Models for fledging rate (fledged young per segment) assuming density dependence had more support (wi = 96%) than those assuming density independence (wi = 4%). Density-dependent processes appeared to influence fledging rate only at densities >5 H ha−1, which occurred in 19% of the segments we sampled. When areas with densities >5 H ha−1 were exc...

Adjacent SNPs in the transcriptional regulatory region of the FADS2 gene associated with fatty acid and growth traits in chickens.

Delta-6 fatty acid desaturases are rate-limiting desaturases involved in metabolic processes of fatty acids, and they are encoded by the FADS2 gene. In the current study, an F2 resource population of Gushi chickens crossed with Anak broilers was used to investigate the genetic effects of the chicken FADS2. Two adjacent single nucleotide polymorphisms (SNPs) (g.4290C>G and g.4291C>A) were identified in the transcriptional regulatory region of the FADS2 gene by means of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and created restriction site-PCR-RFLP. Associations between the two SNPs with chicken fatty acid contents and growth traits were determined using linkage disequilibrium, haplotype construction, and association analysis. The two SNPs and their haplotype combinations were significantly associated with linoleic acid (C18:2), α-linolenic acid (C18:3), arachidonic acid (C20:4), body weight (BW)2, BW4, BW6, shank girth (SG)4, and breast bone length 4 (P<0.05). These results suggested that the SNPs of the FADS2 gene affected the content of essential fatty acid in muscle, and played a role in the early-stage growth rate of chickens.

Investigating the loss of recruitment potential in red grouse (Lagopus lagopus scoticus): the relative importance of hen mortality, food supply, tick infestation and louping-ill

Ticks and their pathogens cause significant disease and economic loss in many animal populations. Despite this, experiments that test the impact of ticks and tick-borne diseases on wild animal populations are rare. Here, we report on an experiment assessing the effect of ticks on red grouse productivity and chick growth in relation to other causes of poor recruitment at two sites in the Scottish uplands during 2005. Treated hens received two leg bands impregnated with the acaricide permethrin, while controls hens were untreated. Chicks were captured at c.2 weeks of age and fitted with a metal patagial tag, and chicks from treated hens also received a permethrin-impregnated strip. Mean tick burdens in treated chicks were close to zero compared with a mean of around 12 in the control group. Although treatment reduced tick infestations, it did not increase brood size. Growth rates in chicks from control and treated hens were similar during the first 10 days and comparable with chicks fed an ad-lib invertebrate-based diet. These results suggest that in this case, neither ticks (and the tick transmitted louping-ill virus) nor food shortages was the main cause of chick mortality. However, mortality in the adult hens was around 35 %, and predation accounted for 62 % of these losses before broods fledged. Our results indicate that on our study sites, predation may have a more important impact on grouse population dynamics than ticks and tick-borne disease. We suggest that it may be more cost effective to determine the causes of poor grouse population performance before implementing popular but expensive tick control measures such as the culling of alternative hosts and running acaracide treated sheep ‘tick-mop’ flocks.

Protective Oral Vaccination against Infectious bursal disease virus Using the Major Viral Antigenic Protein VP2 Produced in Pichia pastoris

Infectious bursal disease virus (IBDV) causes economically important immunosuppressive disease in young chickens. The self-assembling capsid protein (VP2) from IBDV strain IR01 was expressed in Pichia pastoris resulting in the formation of homomeric, 23-nm infectious bursal disease subviral particles (IBD-SVPs) with a yield of 76 mg/l before and 38 mg/l after purification. Anti-IBDV antibodies were detected in chickens injected with purified IBD-SVPs or fed with either purified IBD-SVPs or inactivated P. pastoris cells containing IBD-VP2 (cell-encapsulated). Challenge studies using the heterologous classical IBDV strain (MB3) showed that intramuscular vaccination with 20 µg purified IBD-SVPs conferred full protection, achieved complete virus clearance and prevented bursal damage and atrophy, compared with only 40% protection, 0–10% virus clearance accompanied by severe atrophy and substantial bursal damage in mock-vaccinated and challenge controls. The commercial IBDV vaccine also conferred full protection and achieved complete virus clearance, albeit with partial bursal atrophy. Oral administration of 500 µg purified IBD-SVPs with and without adjuvant conferred 100% protection but achieved only 60% virus clearance with adjuvant and none without it. Moderate bursal damage was observed in both cases but the inclusion of adjuvant resulted in bursal atrophy similar to that observed with live-attenuated vaccine and parenteral administration of 20 µg purified IBD-SVPs. The oral administration of 250 mg P. pastoris cells containing IBD-VP2 resulted in 100% protection with adjuvant and 60% without, accompanied by moderate bursal damage and atrophy in both groups, whereas 25 mg P. pastoris cells containing IBD-VP2 resulted in 90–100% protection with moderate bursal lesions and severe atrophy. Finally, the oral delivery of 50 µg purified IBD-SVPs achieved 40–60% protection with severe bursal lesions and atrophy. Both oral and parenteral administration of yeast-derived IBD-VP2 can therefore induce a specific and protective immune response against IBDV without affecting the growth rate of chickens.