Open Pens Research Articles

Assessing supplementing strategies for beef cattle in a bale grazing system using grass hay during variable winter conditions

IntroductionBeef cattle in the Northern Great Plains of the United States of America are normally kept in open dry lot pens in winter. Practices such as bale grazing, swath grazing, stockpiling, and corn residue grazing, can be used to extend the grazing season and minimize dry lot use. Extending the grazing season has several advantages over dry lot use but arguably the most important benefit is cost savings due to lower labor and input costs. Strategies selected to supplement cattle in extended grazing systems should maintain cost savings while providing required nutrients to cattle. This study was conducted to evaluate supplementing strategies for beef cattle in a bale grazing system using grass hay during variable winter conditions. The study was conducted across variable winter conditions that are encountered in winters in the US Northern Great Plains.MethodsThe study extended over four years. Each year, non-lactating pregnant beef cows (n = 64, year 1; n = 80, year 2, 3, 4) were divided into eight groups of similar average body weight and randomly assigned to one of four bale grazing treatments as follows: a) bale grazing grass hay, b) bale grazing grass hay treated with a liquid supplement, c) bale grazing grass hay and alfalfa hay, and d) bale grazing grass hay and plus 1.8 kg corn DDGS/head/day. Animal performance was assessed from two-day body weights and body condition scores taken at the start and end of the study. Data analysis considered the fixed effects of treatment, year, and treatment x year interaction.ResultsFinal BW tended (P = 0.09) to be greatest following corn DDGS supplementation and lowest when grass hay was offered. The treatment strategy x year interaction (P = 0.026) for ADG showed that corn DDGS supplementation resulted in positive ADG across the years regardless of environmental conditions. Liquid or alfalfa hay supplementation resulted in positive ADG when environmental conditions were favorable. Final BCS (P = 0.005) and BCS change (P = 0.004) were greater following corn DDGS supplementation, intermediate following alfalfa hay or liquid supplementation and lowest when grass hay was fed. Supplementation costs ranged from $1.33 to $1.90/head/day, the highest cost occurred with corn DDGS supplementation mainly due to cost of corn DDGS and labor required to deliver corn DDGS to cattle on pasture.DiscussionAlfalfa hay or molasses-based liquids increased diet CP content but did not supply adequate energy in severely cold winters. Despite relatively higher supplement costs, high energy supplements such as corn DDGS may be required in severely cold winters where cattle require extra energy. Supplement selection should consider supplement effectiveness to meet animal nutrient requirements particularly in adverse winter conditions such as those encountered in the US Northern Great Plains.

Low-cost uncrewed aerial vehicles (UAVs) as a novel tool for welfare assessments on open pen commercial crocodile farms.

The welfare of crocodiles on commercial farms in southern Africa requires precise assessment, focusing on stocking densities and pen conditions. However, disputes between animal welfare groups and farm owners persist due to inadequate methodologies for quantifying these factors. This study aimed to address these disputes and enhance crocodile welfare assessment by introducing a novel technique using a low-cost consumer uncrewed aerial vehicle (UAV) and open-source photogrammetry software. The objective was to quantify key welfare parameters accurately and efficiently. The study involved applying the UAV-based technique to two large Nile crocodile (Crocodylus niloticus) farms in South Africa. The approach enabled the mapping and surveying of crocodile pens, facilitating the determination of stocking densities, biomass indicators, and other pen-related attributes. Comparisons were made between UAV-derived crocodile counts and farmer estimates. The UAV-based crocodile counts significantly differed from the estimates provided by farmers, underscoring the need for a more precise assessment method. The technique's cost-effectiveness was evident, with implementation expenses totalling less than R10 000, a fraction of the cost associated with commercial UAV surveys. The introduced UAV-based technique offers a valuable solution to the ongoing debates regarding crocodile welfare on commercial farms. By quantifying key parameters accurately and economically, it empowers farmers and animal welfare groups to make informed decisions. The method's ease of adoption, demonstrated through its use by some Southern African crocodile farmers, signifies its potential for widespread application, ultimately contributing to improved crocodile welfare.

71 Growth and reproductive responses to gonadotropins in gilts fed on ad libitum (AD) or restricted (RS) bases using an electronic sow feeder (ESF)

Abstract Previous work in our laboratory showed that age at puberty was similar for replacement gilts fed on either RS or AD bases using an ESF. The objective of this investigation was to determine the effects of feeding (RS vs. AD) on growth and sexual development in gilts treated with gonadotropins (P.G. 600; Merck Animal Health, Rahway, NJ). Prepubertal crossbred gilts were moved at 150 d of age to an open pen with an ESF (ACCUTEAM, Osborne Industries, Osborne, KS) located in an environmentally controlled, curtain-sided building. A 10-d training period to the ESF ensued, during which all gilts received feed on AD basis. At 160 d of age, gilts were allocated to treatments in a 2-by-2 factorial design. Treatments were RS plus P.G. 600 (n = 9), RS without P.G. 600 (n = 10), AD plus P.G. 600 (n = 8), or AD without P.G. 600 (n = 8). The P.G. 600 treatment was administered at 170 d of age. Estrus detection commenced at d 171 and continued for 32 d. Puberty onset was not affected by feeding basis (P = 0.85), P.G. 600 (P = 0.56), or feeding basis x P.G. 600 (P = 0.25). Time in estrus and body weight (BW) at puberty were also similar between treatments. Estrous cycle length was shorter (P < 0.01, 20.0 vs. 21.2 d, SE = 0.54) for RS compared with AD gilts. Bodyweights throughout the trial were similar between treatments but were affected by day (P < 0.01), typical of growing gilts. Feed disappearance was affected by feeding basis (P < 0.01, 2.30 vs. 4.54 kg/d, SE = 0.03 for RS and AD, respectively) and day (P < 0.01). For pubertal gilts, gain to feed ratio was improved (P < 0.01, 0.29 vs. 0.21, SE = 0.03) in RS compared with AD gilts, but average daily gain (ADG) was greater in AD gilts (P = 0.05, 0.75 vs 0.88 kg/d, SE = 0.09). Data were normalized for the 20-d period before second estrus. Feed disappearance was affected by feeding basis x day, and decreased in AD, but not RS gilts, as gilts approached estrus (P = 0.04). Feeding visits (P < 0.01) and feeding visit duration (P < 0.01) were affected by feeding basis with AD gilts consuming feed more frequently and spending less time eating per visit. In this study, RS feeding did not delay, and P.G. 600 did not hasten puberty onset. Moreover, RS gilts grew slower but were more feed efficient than AD gilts. We continue to find that employment of an ESF may support current estrus detection methods by monitoring feeding behavior in AD-fed gilts.

Gilts prefer an open pen to a stall

Stalls or crates are a very common type of housing used on pig farms that restrict an animal’s movement. How this confinement impacts the animal’s affective states is seldom investigated. We conducted a preference test over 7 days where trios of gilts (n = 10 trios, 27.4 ± 1.5 weeks old) had free access between individual self-locking stalls (~ 1.2 m2) and a shared open area allowing 2.8 m2/animal (71% of total area). Gilts had access to ad libitum feed and water both inside the crates and in the open area. After 7 days, personality traits of the animals were assessed with open field (OF) and novel object (NO) tests. Principal Component Analysis (PCA) yielded two main components, which we defined as Passivity and Engagement. The median time spent outside the crate was 95.2% as 21/29 of the gilts exhibited a significant preference for pen over crate during the 7-day trial (p < 0.05). Passivity had no relationship with time spent in the open area, but engagement during OF/NO was associated with less use of the open area (OR = 0.39, 95CI = [0.25, 0.60]). Interestingly, gilts were likely to spend less time in the open area at nighttime compared to daytime (Odds Ratio = 0.49, 95CI = [0.40, 0.60]), as well as experimental days passed (OR = 0.70, 95CI = [0.66, 0.73]). During the first daytime and nighttime, 1/29 and 2/29 animals preferred the crate respectively, whereas by the last daytime and nighttime 5 and 9 gilts preferred the crate respectively (p < 0.05). While both intrinsic (personality) and extrinsic (time of day, experimental day) factors appear to influence the gilt’s housing preferences, most gilts significantly prefer an open area to a crate when free access is provided between the two. A smaller subpopulation of animals developed a preference for stalls but still utilize both the stall and the pen throughout the day.

Effects of regional coordination of salmon louse control in reducing negative impacts of salmonid aquaculture on wild salmonids

Parasitic salmon lice (Lepeophtheirus salmonis) are a constraint to the sustainable growth of salmonids in open net pens, and this issue has caused production to level off in recent years in the most aquaculture-intensive areas of Norway. The maximum allowed biomass at a regional level is regulated by using the so-called “traffic light” system, where salmon louse-induced mortality of migrating wild salmon post-smolts is evaluated against set targets. As a case study, we have investigated how a specific aquaculture-intensive area can reduce its louse levels sufficiently to achieve a low impact on wild salmon. Analyses of the output from a virtual post-smolt model that uses data on the reported number of salmon lice in fish farms as key input data and estimates the salmon louse-induced mortality of wild out-migrating Atlantic salmon post-smolts, suggested that female louse abundance on the local farms must be halved in spring to reach the goal implied by the traffic light system. The outcome of a modelling scenario simulating a proposed new plan for coordinated production and fallowing proved beneficial, with an overall reduction in louse infestations and treatment efforts. The interannual variability in louse abundance in spring, however, increased for this scenario, implying unacceptably high louse abundance when many farms were in their second production year. We then combined the scenario with coordinated production with other louse control measures. Only measures that reduced the density of farmed salmonids in open cages in the study area resulted in reductions in salmon louse infestations to acceptable levels. This could be achieved either by stocking with larger fish to reduce exposure time or by reducing fish numbers, e.g. by producing in closed units.

Ecological interactions between farmed Atlantic salmon and wild Atlantic cod populations in Norway: A review of risk sources and knowledge gaps

AbstractAquaculture provides an important and expanding source of protein rich and healthy food to the world. However, to minimize environmental harm from aquaculture, interactions with wild fish communities need to be thoroughly assessed. Here, we characterize the existing knowledge pertaining to such interactions, exemplified with Atlantic salmon (Salmo salar) farming in open net pens along the Norwegian coast and potential consequences for wild Atlantic cod (Gadus morhua) populations. Importantly, the wild cod fishery also provides a protein rich, high quality food source with high economic value. We identify seven risk sources that may affect behaviour, physiology, and survival in wild cod. Of particular importance is the large amount of waste feed that causes wild fish to aggregate around farms, thereby altering a multitude of ecological interactions including predation and disease transmission. Moreover, altered food quality in pellets may alter physiological processes and cause mortality to vulnerable life‐stages in wild cod. More research is needed on mechanisms and thresholds for harm. As the most important cod fisheries are found in northern Norway, where climate change also is rapid, we expect stronger and potentially more harmful interactions between fish farming and wild cod fisheries as aquaculture continues to expand. We hope that our analysis will inspire further research, on farmed salmon and wild cod interactions, but also on aquaculture and wild fish interactions in general. Such research is fundamental for the development of management systems that can reduce the impact of aquaculture on fisheries and the environment.

A gap analysis on modelling of sea lice infection pressure from salmonid farms. I. A structured knowledge review

Sustainability of aquaculture, an important component of the blue economy, relies in part on ensuring assessment of environmental impact and interactions relating to sea lice dispersing from open pen salmon and trout farms. We review research underpinning the key stages in the sea lice infection process to support modelling of lice on wild salmon in relation to those on farms. The review is split into 5 stages: larval production; larval transport and survival; exposure and infestation of new hosts; development and survival of the attached stages; and impact on host populations. This modular structure allows the existing published data to be reviewed and assessed to identify data gaps in modelling sea lice impacts in a systematic way. Model parameterisation and parameter variation is discussed for each stage, providing an overview of knowledge strength and gaps. We conclude that a combination of literature review, empirical data collection and modelling studies are required on an iterative basis to ensure best practice is applied for sustainable aquaculture. The knowledge gained can then be optimised and applied at regional scales, with the most suitable modelling frameworks applied for the system, given regional limitations.

Evaluation of Non-Contact Device to Measure Body Temperature in Sheep.

Non-contact devices have been used in the measurement of body temperature in livestock production as a tool for testing disease in different species. However, there are few studies about the variation and correlations in body temperature between rectal temperature (RT) and non-contact devices such as non-contact infrared thermometers (NCIT) and thermal imaging/infrared thermography (IRT). The objective of this work was to evaluate the accuracy of non-contact devices to measure the body temperature in sheep, considering six body regions and the possibility of implementing these systems in herd management. The experiment was carried out at the experimental farm of the Catholic University of Valencia, located in the municipality of Massanassa in July of 2021, with 72 dry manchega ewes, and we compared the rectal temperature with two types of non-contact infrared devices for the assessment of body temperature in healthy sheep. Except for the temperature taken by NCIT at the muzzle, the correlation between RT vs. NCIT or IRT showed a low significance or was difficult to use for practical flock management purposes. In addition, the variability between devices was high, which implies that measurements should be interpreted with caution in warm climates and open pens, such as most sheep farms in the Spanish Mediterranean area. The use of infrared cameras devices to assess body temperature may have a promising future, but in order to be widely applied as a routine management method on farms, the system needs to become cheaper, simpler in terms of measurements and quicker in terms of analyzing results.

PSXI-13 Growth and Onset of Puberty in Replacement Gilts Fed on Ad Libitum Or Restricted Bases Using an Electronic Sow Feeder

Abstract Replacement gilts are typically fed on an ad libitum basis until approximately 135 kg BW at approximately 200 d of age and are bred between 135 and 160 kg BW during their second estrus. The shift to group-housing of the breeding herd makes it difficult to manage animals individually. Thus, utilization of an electronic sow feeder (ESF) enables caretakers to manage animals individually in group-housing situations, by allotting predetermined amounts of feed. The objective was to determine the effect of feeding level on growth and sexual development in gilts. Crossbred gilts, assumed prepubertal, were moved at 150 d of age to an open pen measuring 44.3 m2 located in a curtain-sided building with partially slatted concrete floors and an ESF (ACCUTEAM, Osborne Industries, Osborne, KS). Gilts were acclimated to the ESF during a 10-d period, during which they received feed on an ad libitum basis. At 160 d of age, gilts were randomly assigned to receive feed on either an ad libitum (AD, n = 18) or restricted (2.73 kg/d; RS, n = 19) basis. Estrus detection was performed for 42 d. Feeding level had no effect on age at puberty (P = 0.23). The pubertal estrus length was similar between treatments (P = 0.23); however, AD gilts exhibited a longer second estrus period (P = 0.05) compared with RS gilts (37.6 vs 30.8 h, SE = 3.6). Estrous cycle length was not affected (P = 0.72) by feeding level. There were no effects of feeding level (P = 0.36) or feeding level x day (P = 0.53) on BW; however, there was an effect of day (P &amp;lt; 0.01), indicative of growing gilts. Feed disappearance was affected by feeding level (P &amp;lt; 0.01, 4.25 vs. 2.68 kg/d, SE = 0.05 for AD and RS, respectively), day (P &amp;lt; 0.01) and feeding level x day (P &amp;lt; 0.01). Total station visits were affected by feeding level x day (P = 0.05). Non-feeding visits were affected by feeding level (P &amp;lt; 0.01, 1.0 vs. 3.7, SE = 0.22) and day (P &amp;lt; 0.01) but not feeding level x day (P = 0.20). Feeding visits were affected by feeding level x day (P &amp;lt; 0.01). Data were then normalized to the 20-d period before second estrus. Feed disappearance was affected by feeding level x day (P &amp;lt; 0.01), with feed disappearance decreasing in AD, but not RS, gilts as they approached estrus. During this 20-d period, BW was affected by feeding level x day (P &amp;lt; 0.01), with AD gilts having improved growth compared with RS gilts. In this study, feeding level did not affect age at puberty; however, utilizing an ESF may augment current estrus detection methods by monitoring feeding behavior.

Sea lice management measures for farmed Atlantic salmon (Salmo salar) in Scotland: Costs and effectiveness

Cultured and wild Atlantic salmon around the world are affected by sea lice. Salmon culturing countries have policies in place to minimize sea lice abundance on cultured salmon in open net pens in the marine environment. To adhere to these policies, salmon producers deploy a range of management measures against sea lice throughout the production cycle. The cost effectiveness of these sea lice management measures is not well quantified. This study provides estimates for cost effectiveness in Scotland of (1) individual sea lice management measures and (2) integrated management strategies that span an entire production cycle. Estimates were based on the cost-effectiveness ratio, in which costs consist of those associated with equipment, implementation, environment and side effects (mortality). Effectiveness was based on interviews and expert opinions. For single measures, skirts and the use of in-feed medicines had the best cost-effectiveness. Cleaner fish, fresh or brackish water baths, the physical removal measures (thermolicer and hydrolicer) and medicinal baths were among the next most cost-effective measures, followed by hydrogen peroxide baths. Tarpaulins were more cost-effective than well boats due to lower costs under the assumption of equal effectiveness. Direct comparison of cost effectiveness among measures may not always be constructive as they are deployed at different times in the production cycle and their functionality is different. A holistic approach to sea lice management, a common practice in industry as shown by the integrated management strategies, may reduce risk of developing resistance. For the single measures, carbon costs were insignificant compared to other costs. If measures would have a lasting effect on production through to harvest, such as ongoing increased mortality as a result of a management measure, carbon costs may become significant. Better quantification of effectiveness is important because the scarcity of data led to uncertainty that had a large impact on cost-effectiveness estimates. Generally, this study demonstrated a lack of reliable publicly available data and lack of standardization of data, which constrains research. Highlighted gaps in knowledge can serve as a guide to improve further understanding.

First molecular detection of influenza D virus in cattle from commercial farm in Nigeria, Sub-Saharan Africa

Objective: To carrry out molecular surveillance of influenza D virus (IDV) in cattle in Lagos, Nigeria. Methods: Prospective epidemiological investigation was initiated in a large commercial farm market where animals in open pens were reared, sold, and butchered under poor hygienic conditions without adequate biosecurity measures. A total of 80 nasopharyngeal swabs were collected from cattle between October and November 2021. The samples were extracted using an RNA purification kit (NIMR). RNA extracts were amplified following a two-step PCR using FIREScript RT cDNA synthesis kit (Solis Biodyne, Estonia), followed by PCR OneTaq Quick-load 2X master-mix (NEB, UK) in a Rotor-Gene thermocycler (Qiagen, Germany). Amplicons were detected using a 1.5% Gel electrophoresis. Results: In total, 32.5% (26/80) IDV was detected in cattle. Sick animals showed higher burden of IDV with 65.4% (17/26) than 34.6% (9/26) in a healthy population, including 88.2% (15/17) cattle with diarrhoea and 11.8% (2/17) with nausea having IDV. An incidence of 69.2% (18/26) by sex was recorded in bull, which was more than twice compared to 30.7% (8/26) in cow. Age prevalence showed 62.2% (18/26), the highest detection in cattle of four years old, followed by 23.1% (6/26) in five years old, while the lowest 7.7% (2/26) was recorded in three years old. Conclusions: To the best of our knowledge, this study presents the first molecular detection of IDV in Nigeria and West Africa sub-region. It underscores the need for continuous surveillance of IDV at the animal-human interface.

Prepared for the worst? Emergency preparedness in Norwegian fish farming – Status and further improvements

Norwegian fish farming has traditionally taken place in open net pens at the coast and in the fjords. With the aim of utilising new areas, innovative farm designs for open ocean locations have emerged in recent years. The government is developing a regulatory framework for operating in these areas. Increased distance to shore will require a robust emergency preparedness for personnel, fish, environment, food safety and material assets.This article provides new knowledge regarding the status of emergency preparedness in the Norwegian salmon fish farming industry, describes the risk picture for coastal versus offshore production sites and suggests improvements for establishing emergency preparedness.Methods include document studies, interviews, workshops and dialogue meetings with fish farmers, suppliers and authorities.Findings support that preventive work and learning from accidents are seen as important, but also that emergency response plans may become too extensive and that more can be done when it comes to cooperation across companies. Key improvements include performing systematic emergency preparedness analysis, standardizing emergency preparedness performance requirements, and working together across companies. For offshore fish farming, synergies with other industries are key for the quality of emergency preparedness in the future.

Gait analysis in swine, sheep, and goats after neurologic injury: a literature review.

Medical research on neurologic ailments requires representative animal models to validate treatments before they are translated to human clinical trials. Rodents are the predominant animal model used in neurological research despite limited anatomic and physiologic similarities to humans. As a result, functional testing designed to assess locomotor recovery after neurologic impairment is well established in rodent models. Comparatively, larger, more clinically relevant models have not been as well studied. To achieve similar locomotor testing standardization in larger animals, the models must be accessible to a wide array of researchers. Non-human primates are the most relevant animal model for translational research, however ethical and financial barriers limit their accessibility. This review focuses on swine, sheep, and goats as large animal alternatives for transitional studies between rodents and non-human primates. The objective of this review is to compare motor testing and data collection methods used in swine, sheep, and goats to encourage testing standardization in these larger animal models. The PubMed database was analyzed by searching combinations of swine, sheep, and goats, neurologic injuries, and functional assessments. Findings were categorized by animal model, data collection method, and assessment design. Swine and sheep were used in the majority of the studies, while only two studies were found using goats. The functional assessments included open pen analysis, treadmill walking, and guided free walking. Data collection methods included subjective behavioral rating scales and objective tools such as pressure-sensitive mats and image-based analysis software. Overall, swine and sheep were well-suited for a variety of assessment designs, with treadmill walking and guided free walking offering the most consistency across multiple trials. Data collection methods varied, but image-based gait analysis software provided the most robust analysis. Future studies should be conducted to standardize functional testing methods after neurologic impairment in large animals.

Ileal and cecal microbiota response to Salmonella Typhimurium challenge in conventional and slow-growing broilers.

Despite the negative impacts of Salmonella intestinal colonization on human health, Salmonella is a natural colonizer of the gastrointestinal tract and is not overtly pathogenic to the avian host. It is of interest to understand the impacts and colonization rates of Salmonella across selected genetic lines such as slow-growing (SG) and conventional (CONV) broilers. The objective of this study was to characterize the relationship between Salmonella enterica serovar Typhimurium challenge and selected broiler genetic lines on the ileal and cecal microbiome. Male chicks of two broiler breeds (n = 156/breed) were cohoused in an open floor pen until day 7. On day 13, the chicks were then separated into 12 isolators per breed (4 rooms, 6 isolators/room, 11 chicks/isolator). On day 14, chicks in the 12 treatment isolators (6 isolators/breed, 108 total) were challenged with Salmonella Typhimurium (ST) (1 × CFU/ml) via oral gavage while the remaining chicks (n = 108) were given an oral gavage of sterile tryptic soy broth control (C). Ileal and cecal contents were collected on day 7 from 24 chicks of each breed, and on days 13, 17, 21, and 24 from two chicks per isolator. Samples underwent DNA extraction and PCR amplification to obtain 16S rRNA amplicons that were sequenced with Illumina MiSeq. Salmonella Typhimurium colonization in the cecum was not different in the two broiler breeds. The main effect of breed had the greatest impact on the ileum microbiota of broilers 7 days of age where SG broilers had significantly lower diversity and richness compared to CONV broilers (p < 0.05). Salmonella Typhimurium challenge consistently caused a change in beta diversity. Regardless of day or intestinal location, challenged broilers had many amplicon sequence variants (ASVs) with decreased abundance of likely beneficial bacteria such as Mollicutes RF39, Shuttleworthia, Flavonifractor, and Oscillibacter compared to broilers that were unchallenged with Salmonella Typhimurium (p < 0.05). Additionally, there was a difference in the timing of when the microbiota alpha and beta diversity of each breed responded to Salmonella Typhimurium challenge. Thus, both broiler breed and Salmonella Typhimurium can impact the intestinal microbiota.

Oxygenation effects on temperature and dissolved oxygen at a commercial Atlantic salmon farm

As climate change continues to warm oceans and exacerbate deoxygenation, coastal ecosystems and anthropogenic activities that occur there are left vulnerable. Fish cultured in ocean net pens are increasingly subjected to oxygen stress. Aeration and oxygenation have been utilized to improve oxygen conditions in pond aquaculture; however, their use in open ocean net pens is still in its infancy. In this study, liquid oxygen was distributed through the NetOx Net system within sea cages in a commercial Atlantic salmon (Salmo salar) farm located off Saddle Island, Nova Scotia (Canada). Real-time sensors were used to measure temperature and oxygen before oxygenation, between oxygenation and the onset of de-stratification due to mixing, and after mixing had resulted in full de-stratification. Oxygenation likely resulted in the upwelling of cold deep water, lowering the cage temperature by ∼4 ℃ which in turn increased oxygen solubility and decreased fish metabolism (though no significant change in growth was observed); these factors resulted in an overall increase in oxygen concentrations by ∼1.5 mgL−1. Following de-stratification, the effects of the oxygenation system were diluted, and mixing due to oceanographic processes dominated the system. As climate change increases hypoxia in coastal regions, where aquaculture practices continue to expand, oxygenation systems will become commonplace. Therefore, it is important to understand whether they will work in an environment that is open to other elements.

Investigation of growth performance of post‐smolt Atlantic salmon ( Salmo salar L.) in semi closed containment system: A big‐scale benchmark study

The Norwegian salmon industry faces challenges related to sea lice (Lepeophtheirus salmonis) infestations, escapees, diseases and environmental impact. Semi-closed containment systems (S-CCS) have been proposed to abate these challenges. In the S-CCS, cultured fish are separated from the natural environment by a physical barrier, reducing the time fish spend in open sea cages. Production data from six cohorts of salmon were used to compare growth and performance of fish raised in S-CCS and in open sea cages (control group) incorporating different seasons. The study was carried out in two phases. Phase one used post-smolts from approximately 100 to 800 g in seawater, and fish in S-CCS were compared with a reference group from an open sea cage. The second, grow-out phase covered the size range from approximately 800 to 5000 g in open sea cages; here fish previously reared in S-CCS were compared with fish from a control group. The study showed a significantly lower infestation of sea lice in S-CCS (0.02–0.04) fish compared with the control group (0.18–0.62) during the post-smolt phase. Furthermore, in the grow-out phase the S-CCS group showed higher growth rate and higher final weight (4680 g [spring], 4890 g [fall]) for the S-CCS group compared with the control group (3800 g [spring] and 4080 g [fall]). Salmon raised in S-CCS showed significantly higher survival compared with the control group in open pens, indicating increased resilience in fish raised in S-CCS when transferred to open net pens in sea. It is concluded that S-CCS have advantages compared with exposure to the natural environment in open pens in western Norway.

Influence of Excitability Rate on Physiological Responses to Stress in Goats.

Simple SummaryIndividual differences in excitable temperament and its effects on physiological stress responses are not adequately studied in goats. This experiment was conducted to determine if the temperament of goats affects their physiological responses when exposed to stress. Intact male Spanish goats were rated for excitability based on a three-point scoring system with a higher score (excitability score, ES) representing a more excitable temperament. Goats were then subjected to one of three treatments (TRT) for 90 min: (i) isolated in an open pen with metal grill panels, (ii) isolated in a pen with side panels covered using tarp sheets, or (iii) maintained as controls with no isolation. Overall plasma cortisol concentrations were the highest in goats with ES 3. Goats with ES 1 had the lowest plasma glucose and non-esterified fatty acid concentrations. Neutrophil–lymphocyte ratio was also the highest in the ES 3 goats. There is evidence that calm goats had lower physiological stress responses compared to goats with excitable temperament.This study was conducted to determine if excitability score (ES) in goats can influence their physiological responses when subjected to stress. Thirty-six intact male Spanish goats (8-mo-old) were individually weighed and scored for excitability: 1 for calm (13 goats), 2 for moderately excitable (11 goats), and 3 for highly excitable (12 goats). To impose stress, goats were assigned to one of three treatments (TRT) for 90 min: (i) isolation in an open pen with metal grill panels, (ii) isolation in a pen with side panels covered using tarp sheets, and (iii) no isolation (control). Blood samples were collected at 0, 30, 60, and 90 min of isolation and physiological data were analyzed using MIXED procedures in SAS. The data from the two isolation treatments were pooled and compared with that of the control group. Plasma cortisol and non-esterified fatty acid concentrations were the lowest in goats with ES 1 (p < 0.05). Neutrophil–lymphocyte ratios were also the lowest in goats with a calm temperament (p < 0.01). Application of full quadratic model using response surface methodology (PROC RSREG) in SAS revealed that the influence of ES on physiological stress responses over time was not the same between the TRT groups. The results indicate that physiological stress responses are greater in goats with an excitable temperament compared to goats with a calm temperament.

Modelling salmon lice-induced mortality of wild salmon post-smolts is highly sensitive to calibration data

Salmon lice from fish farms in open net pens pose a threat to the survival of wild salmon post-smolts migrating through areas with high farm and lice densities. Reliable estimation of this mortality is fundamental for the sustainable management of aquaculture in such areas but is challenged by considerable uncertainty about several of the processes that link reported lice numbers in fish farms to post-smolt mortality. Utilising recent access to lice data from post-smolt trawling, we revised a virtual post-smolt model that estimates salmon lice-induced mortality of seaward-migrating wild salmon post-smolts. We also assessed the sensitivity of model results to model assumptions that differ among the virtual post-smolt models currently being used as management support in Norway. The spatiotemporal variation in infestation pressure along the entire Norwegian coast was calculated based on monitoring data for salmon lice, temperature and fish abundance in all Norwegian salmonid farm locations. The revised model integrates lice data from sentinel cage experiments and post-smolt trawling to quantify the spatiotemporal variation in infestation rate of wild post-smolts from the spatiotemporal infestation pressure, while also estimating the effect of calibration data type on infestation rate. Results show 10 times higher infestation rate in trawl-caught post-smolts than in post-smolts from sentinel cage experiments. Mortality estimates calibrated to trawl data are more sensitive to assumptions about possible density dependence in lice infestation rate than to assumptions about migration speed. These findings contribute to explaining why different virtual post-smolt models provide different estimates of salmon lice-induced mortality.

Behavioural responses of wild Pacific salmon and herring to boat noise

There is growing concern about impacts of ship and small boat noise on marine wildlife. Few studies have quantified impacts of anthropogenic noise on ecologically, economically, and culturally important fish. We conducted open net pen experiments to measure Pacific herring (Clupea pallasii) and juvenile salmon (pink, Oncorhynchus gorbuscha, and chum, Oncorhynchus keta) behavioural response to noise generated by three boats travelling at different speeds. Dose-response curves for herring and salmon estimated 50% probability of eliciting a response at broadband received levels of 123 and 140 dB (re 1 μPa), respectively. Composite responses (yes/no behaviour change) were evaluated. Both genera spent more time exhibiting behaviours consistent with anti-predator response during boat passings. Repeated elicitation of vigilance or anti-predatory responses could result in increased energy expenditure or decreased foraging. These experiments form an important step toward assessing population-level consequences of noise, and its ecological costs and benefits to predators and prey.

Salmon louse infestation levels on sea trout can be predicted from a hydrodynamic lice dispersal model

AbstractThe abundance of the parasitic salmon louse has increased with the growth in aquaculture of salmonids in open net pens. This represents a threat to wild salmonid populations as well as a key limiting factor for salmon farming. The Norwegian ‘traffic light’ management system for salmon farming aims to increase aquaculture production while securing sustainable wild salmonid populations. However, this system is at present solely focusing on mortality in wild Atlantic salmon, while the responses of sea trout with different ecological characteristics are not included.We analyse lice counts on sea trout from surveillance data and use Bayesian statistical models to relate observed lice infestations to the environmental lice infestation pressure, salinity and current speed. These models can be used in risk assessment to predict when and where lice numbers surpass threshold levels for expected serious health effects in wild sea trout.We find that in production areas with the highest density of salmon farms (West coast), more than 50% of the sea trout experienced lice infestations above the levels of expected serious health effects.We also observed high lice infestations on sea trout in areas with salinities below louse tolerance levels, indicating that fish had been infested elsewhere but were returning to low‐saline waters to delouse. This behavioural response may over time disrupt anadromy in sea trout.The observed infestations on sea trout can be explained by the hydrodynamic lice dispersal model, which provides continuous estimates of lice exposure along the whole Norwegian coast. These estimates, which are used in Atlantic salmon research and management, can also be used for sea trout.Synthesis and applications. Wild sea trout, spending its entire feeding migration in fjords and coastal areas, is at higher risk than wild Atlantic salmon to lice infestations from industrial salmon farming. The high levels of lice infestation we observed on sea trout question the environmental sustainability of the current aquaculture industry in areas with intensive farming. We discuss the complex responses of sea trout to salmon lice and how the Norwegian ‘traffic light’ management system may include data on sea trout.