The interrelation between temperature regimes and fish size in juvenile Atlantic cod (Gadus morhua): effects on growth and feed conversion efficiency

The present paper describes the growth properties of juvenile Atlantic cod (Gadus morhua) reared at 7, 10, 13 and 16 °C, and a group reared under “temperature steps” i.e. with temperature reduced successively from 16 to 13 and 10 °C. Growth rate and feed conversion efficiency of juvenile Atlantic cod were significantly influenced by the interaction of temperature and fish size. Overall growth was highest in the 13 °C and the T-step groups but for different reasons, as the fish at 13 °C had 10% higher overall feeding intake compared to the T-step group, whereas the T-step had 8% higher feeding efficiency. After termination of the laboratory study the fish were reared in sea pens at ambient conditions for 17 months. The groups performed differently when reared at ambient conditions in the sea as the T-step group was 11.6, 11.5, 5.3 and 7.5% larger than 7, 10, 13 and 16 °C, respectively in June 2005. Optimal temperature for growth and feed conversion efficiency decreased with size, indicating an ontogenetic reduction in optimum temperature for growth with increasing size. The results suggest an optimum temperature for growth of juvenile Atlantic cod in the size range 5–50 g dropping from 14.7 °C for 5–10 g juvenile to 12.4 °C for 40–50 g juvenile. Moreover, a broader parabolic regression curve between growth, feed conversion efficiency and temperature as size increases, indicate increased temperature tolerance with size. The study confirms that juvenile cod exhibits ontogenetic variation in temperature optimum, which might partly explain different spatial distribution of juvenile and adult cod in ocean waters. Our study also indicates a physiological mechanism that might be linked to cod migrations as cod may maximize their feeding efficiency by active thermoregulation

Global age-sex-specific fertility, mortality, healthy life expectancy (HALE), and population estimates in 204 countries and territories, 1950–2019: a comprehensive demographic analysis for the Global Burden of Disease Study 2019

Background: Accurate and up-to-date assessment of demographic metrics is crucial for understanding a wide range of social, economic, and public health issues that affect populations worldwide. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 produced updated and comprehensive demographic assessments of the key indicators of fertility, mortality, migration, and population for 204 countries and territories and selected subnational locations from 1950 to 2019. Methods: 8078 country-years of vital registration and sample registration data, 938 surveys, 349 censuses, and 238 other sources were identified and used to estimate age-specific fertility. Spatiotemporal Gaussian process regression (ST-GPR) was used to generate age-specific fertility rates for 5-year age groups between ages 15 and 49 years. With extensions to age groups 10–14 and 50–54 years, the total fertility rate (TFR) was then aggregated using the estimated age-specific fertility between ages 10 and 54 years. 7417 sources were used for under-5 mortality estimation and 7355 for adult mortality. ST-GPR was used to synthesise data sources after correction for known biases. Adult mortality was measured as the probability of death between ages 15 and 60 years based on vital registration, sample registration, and sibling histories, and was also estimated using ST-GPR. HIV-free life tables were then estimated using estimates of under-5 and adult mortality rates using a relational model life table system created for GBD, which closely tracks observed age-specific mortality rates from complete vital registration when available. Independent estimates of HIV-specific mortality generated by an epidemiological analysis of HIV prevalence surveys and antenatal clinic serosurveillance and other sources were incorporated into the estimates in countries with large epidemics. Annual and single-year age estimates of net migration and population for each country and territory were generated using a Bayesian hierarchical cohort component model that analysed estimated age-specific fertility and mortality rates along with 1250 censuses and 747 population registry years. We classified location-years into seven categories on the basis of the natural rate of increase in population (calculated by subtracting the crude death rate from the crude birth rate) and the net migration rate. We computed healthy life expectancy (HALE) using years lived with disability (YLDs) per capita, life tables, and standard demographic methods. Uncertainty was propagated throughout the demographic estimation process, including fertility, mortality, and population, with 1000 draw-level estimates produced for each metric. Findings: The global TFR decreased from 2•72 (95% uncertainty interval [UI] 2•66–2•79) in 2000 to 2•31 (2•17–2•46) in 2019. Global annual livebirths increased from 134•5 million (131•5–137•8) in 2000 to a peak of 139•6 million (133•0–146•9) in 2016. Global livebirths then declined to 135•3 million (127•2–144•1) in 2019. Of the 204 countries and territories included in this study, in 2019, 102 had a TFR lower than 2•1, which is considered a good approximation of replacement-level fertility. All countries in sub-Saharan Africa had TFRs above replacement level in 2019 and accounted for 27•1% (95% UI 26•4–27•8) of global livebirths. Global life expectancy at birth increased from 67•2 years (95% UI 66•8–67•6) in 2000 to 73•5 years (72•8–74•3) in 2019. The total number of deaths increased from 50•7 million (49•5–51•9) in 2000 to 56•5 million (53•7–59•2) in 2019. Under-5 deaths declined from 9•6 million (9•1–10•3) in 2000 to 5•0 million (4•3–6•0) in 2019. Global population increased by 25•7%, from 6•2 billion (6•0–6•3) in 2000 to 7•7 billion (7•5–8•0) in 2019. In 2019, 34 countries had negative natural rates of increase; in 17 of these, the population declined because immigration was not sufficient to counteract the negative rate of decline. Globally, HALE increased from 58•6 years (56•1–60•8) in 2000 to 63•5 years (60•8–66•1) in 2019. HALE increased in 202 of 204 countries and territories between 2000 and 2019. Interpretation: Over the past 20 years, fertility rates have been dropping steadily and life expectancy has been increasing, with few exceptions. Much of this change follows historical patterns linking social and economic determinants, such as those captured by the GBD Socio-demographic Index, with demographic outcomes. More recently, several countries have experienced a combination of low fertility and stagnating improvement in mortality rates, pushing more populations into the late stages of the demographic transition. Tracking demographic change and the emergence of new patterns will be essential for global health monitoring. Funding: Bill & Melinda Gates Foundation. © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licens

Global burden of 87 risk factors in 204 countries and territories, 1990�2019: a systematic analysis for the Global Burden of Disease Study 2019

Background: Rigorous analysis of levels and trends in exposure to leading risk factors and quantification of their effect on human health are important to identify where public health is making progress and in which cases current efforts are inadequate. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 provides a standardised and comprehensive assessment of the magnitude of risk factor exposure, relative risk, and attributable burden of disease. Methods: GBD 2019 estimated attributable mortality, years of life lost (YLLs), years of life lived with disability (YLDs), and disability-adjusted life-years (DALYs) for 87 risk factors and combinations of risk factors, at the global level, regionally, and for 204 countries and territories. GBD uses a hierarchical list of risk factors so that specific risk factors (eg, sodium intake), and related aggregates (eg, diet quality), are both evaluated. This method has six analytical steps. (1) We included 560 risk�outcome pairs that met criteria for convincing or probable evidence on the basis of research studies. 12 risk�outcome pairs included in GBD 2017 no longer met inclusion criteria and 47 risk�outcome pairs for risks already included in GBD 2017 were added based on new evidence. (2) Relative risks were estimated as a function of exposure based on published systematic reviews, 81 systematic reviews done for GBD 2019, and meta-regression. (3) Levels of exposure in each age-sex-location-year included in the study were estimated based on all available data sources using spatiotemporal Gaussian process regression, DisMod-MR 2.1, a Bayesian meta-regression method, or alternative methods. (4) We determined, from published trials or cohort studies, the level of exposure associated with minimum risk, called the theoretical minimum risk exposure level. (5) Attributable deaths, YLLs, YLDs, and DALYs were computed by multiplying population attributable fractions (PAFs) by the relevant outcome quantity for each age-sex-location-year. (6) PAFs and attributable burden for combinations of risk factors were estimated taking into account mediation of different risk factors through other risk factors. Across all six analytical steps, 30 652 distinct data sources were used in the analysis. Uncertainty in each step of the analysis was propagated into the final estimates of attributable burden. Exposure levels for dichotomous, polytomous, and continuous risk factors were summarised with use of the summary exposure value to facilitate comparisons over time, across location, and across risks. Because the entire time series from 1990 to 2019 has been re-estimated with use of consistent data and methods, these results supersede previously published GBD estimates of attributable burden. Findings: The largest declines in risk exposure from 2010 to 2019 were among a set of risks that are strongly linked to social and economic development, including household air pollution; unsafe water, sanitation, and handwashing; and child growth failure. Global declines also occurred for tobacco smoking and lead exposure. The largest increases in risk exposure were for ambient particulate matter pollution, drug use, high fasting plasma glucose, and high body-mass index. In 2019, the leading Level 2 risk factor globally for attributable deaths was high systolic blood pressure, which accounted for 10·8 million (95 uncertainty interval UI 9·51�12·1) deaths (19·2% 16·9�21·3 of all deaths in 2019), followed by tobacco (smoked, second-hand, and chewing), which accounted for 8·71 million (8·12�9·31) deaths (15·4% 14·6�16·2 of all deaths in 2019). The leading Level 2 risk factor for attributable DALYs globally in 2019 was child and maternal malnutrition, which largely affects health in the youngest age groups and accounted for 295 million (253�350) DALYs (11·6% 10·3�13·1 of all global DALYs that year). The risk factor burden varied considerably in 2019 between age groups and locations. Among children aged 0�9 years, the three leading detailed risk factors for attributable DALYs were all related to malnutrition. Iron deficiency was the leading risk factor for those aged 10�24 years, alcohol use for those aged 25�49 years, and high systolic blood pressure for those aged 50�74 years and 75 years and older. Interpretation: Overall, the record for reducing exposure to harmful risks over the past three decades is poor. Success with reducing smoking and lead exposure through regulatory policy might point the way for a stronger role for public policy on other risks in addition to continued efforts to provide information on risk factor harm to the general public. Funding: Bill & Melinda Gates Foundation. © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licens

Managing rhodes grass (Chloris gayana) cv. Callide to improve diet quality. 2. Effects of stocking rate and irrigation frequency

The effects of stocking rate and irrigation frequency on the milk production of cows grazing nitrogen-fertilised Callide rhodes grass pastures was studied in south-east Queensland. Pastures were stocked at 3.5, 5.25 and 6.1 cows/ha from January-May inclusive, and irrigated at fortnightly or monthly intervals. Yields on offer pregrazing and pasture, leaf and stem residues after grazing decreased at the higher stocking rates. Consumption of grass leaf averaged 10.6, 7.7 and 6.5 kg DM/cow/d for cows grazed at 3.5, 5.25 and 6.1 cows/ha, respectively (P0.05). Milk yields averaged 16.6 kg/cow/d for Weeks 7-18 and were unaffected by treatment. Liveweight loss in the first 15 weeks of the experiment averaged 15, 28 and 43 kg at 3.5, 5.25 and 6.1 cows/ha, respectively (P<0.05). Cows stocked at 3.5/ha recovered liveweight during the experiment, but liveweight losses continued for cows at 5.25 and 6.1 cows/ha. Rhodes grass management should aim to harvest a high proportion of leaf, a result which was achieved under a wide range of stocking rates in this experiment. Reducing the frequency and total volume of irrigation resulted in reduced levels of soil water and pasture yield, but did not affect milk production until the final 3 weeks of the experiment (May). The stocking rate of 3.5 cows/ha allowed cows to maintain body weight and appears optimal for these pastures. The ability of the pastures to maintain DM yield with half the applied water input demonstrates that efficiencies may be gained by closer monitoring of soil and pasture production in autumn rather than the normal practice of fortnightly watering. This, combined with the longer grazing interval of 6 weeks and a stocking rate of 3.5 cows/ha, provided the most efficient use of the tropical grass pasture resource in late summer and autumn

Managing rhodes grass (Chloris gayana) cv. Callide to improve diet quality. 1. Effects of age of regrowth, strip grazing and mulching

Two experiments assessed grazing management strategies for irrigated and nitrogen-fertilised rhodes grass (Chloris gayana) cv. Callide pasture. In Experiment 1, the 4 treatments were: (i) open grazing of the entire paddock on a 2-week cycle (Open); (ii) grazing on a 2-week, daily strip-grazing rotation (2); (iii) a 4-week, daily strip-grazing rotation (4); and (iv) a 6-week, daily strip-grazing rotation (6). For treatments (ii), (iii) and (iv), pasture was allocated at 15 kg green leaf dry matter (DM)/cow/d and grass was mulched to a stubble height of 10 cm after grazing. Stocking rates attained were 1.7, 3.7, 3.5 and 3.4 cows/ha for Treatments (i), (ii), (iii) and (iv), respectively. In Experiment 2, pastures were grazed on a 2-paddock 2-weekly rotation [Open (O) and Open+mulching (OM)] or 28-day rotational cycle without mulching (28) or with mulching (28M) after grazing. There were substantial differences in yield of pasture on offer to cows with different grazing management, but total leaf yield appeared similar, with a mean growth rate of 42 kgDM/ha/d. There were small, but significant differences in pasture quality between treatments, though pastures in unmulched paddocks had lower crude protein and higher NDF levels than those in mulched paddocks. Animals selected strongly for leaf (78%) across all treatments, though stem content increased from 13% in February to 25% in April. Milk yield was not altered by age of regrowth or open grazing, but was reduced (P<0.05) where rotationally grazed pastures were not mulched. This was attributed to the presence of stem impeding access to leaf when pastures were grazed in narrow strips. The results demonstrate that intensive management of Callide rhodes grass pastures can support a stocking rate up to 3.7 cows/ha, but there are only small animal production differences associated with radically different grazing management routines. Additional operational costs associated with more intensive management of pastures ranged from AUD30 to AUD80/hafor the 18 weeks of the experiment compared with open grazing. In Experiment 2, net marginal returns were AUD0, -38, -145 and 66/ha for the four treatments O, OM, 28 and 28M, respectively

Managing rhodes grass (Chloris gayana) cv. Callide to improve diet quality. 1. Effects of age of regrowth, strip grazing and mulching

Two experiments assessed grazing management strategies for irrigated and nitrogen-fertilised rhodes grass (Chloris gayana) cv. Callide pasture. In Experiment 1, the 4 treatments were: (i) open grazing of the entire paddock on a 2-week cycle (Open); (ii) grazing on a 2-week, daily strip-grazing rotation (2); (iii) a 4-week, daily strip-grazing rotation (4); and (iv) a 6-week, daily strip-grazing rotation (6). For treatments (ii), (iii) and (iv), pasture was allocated at 15 kg green leaf dry matter (DM)/cow/d and grass was mulched to a stubble height of 10 cm after grazing. Stocking rates attained were 1.7, 3.7, 3.5 and 3.4 cows/ha for Treatments (i), (ii), (iii) and (iv), respectively. In Experiment 2, pastures were grazed on a 2-paddock 2-weekly rotation [Open (O) and Open+mulching (OM)] or 28-day rotational cycle without mulching (28) or with mulching (28M) after grazing. There were substantial differences in yield of pasture on offer to cows with different grazing management, but total leaf yield appeared similar, with a mean growth rate of 42 kgDM/ha/d. There were small, but significant differences in pasture quality between treatments, though pastures in unmulched paddocks had lower crude protein and higher NDF levels than those in mulched paddocks. Animals selected strongly for leaf (78%) across all treatments, though stem content increased from 13% in February to 25% in April. Milk yield was not altered by age of regrowth or open grazing, but was reduced (P<0.05) where rotationally grazed pastures were not mulched. This was attributed to the presence of stem impeding access to leaf when pastures were grazed in narrow strips. The results demonstrate that intensive management of Callide rhodes grass pastures can support a stocking rate up to 3.7 cows/ha, but there are only small animal production differences associated with radically different grazing management routines. Additional operational costs associated with more intensive management of pastures ranged from AUD30 to AUD80/hafor the 18 weeks of the experiment compared with open grazing. In Experiment 2, net marginal returns were AUD0, -38, -145 and 66/ha for the four treatments O, OM, 28 and 28M, respectively

Managing rhodes grass (Chloris gayana) cv. Callide to improve diet quality. 2. Effects of stocking rate and irrigation frequency

The effects of stocking rate and irrigation frequency on the milk production of cows grazing nitrogen-fertilised Callide rhodes grass pastures was studied in south-east Queensland. Pastures were stocked at 3.5, 5.25 and 6.1 cows/ha from January-May inclusive, and irrigated at fortnightly or monthly intervals. Yields on offer pregrazing and pasture, leaf and stem residues after grazing decreased at the higher stocking rates. Consumption of grass leaf averaged 10.6, 7.7 and 6.5 kg DM/cow/d for cows grazed at 3.5, 5.25 and 6.1 cows/ha, respectively (P0.05). Milk yields averaged 16.6 kg/cow/d for Weeks 7-18 and were unaffected by treatment. Liveweight loss in the first 15 weeks of the experiment averaged 15, 28 and 43 kg at 3.5, 5.25 and 6.1 cows/ha, respectively (P<0.05). Cows stocked at 3.5/ha recovered liveweight during the experiment, but liveweight losses continued for cows at 5.25 and 6.1 cows/ha. Rhodes grass management should aim to harvest a high proportion of leaf, a result which was achieved under a wide range of stocking rates in this experiment. Reducing the frequency and total volume of irrigation resulted in reduced levels of soil water and pasture yield, but did not affect milk production until the final 3 weeks of the experiment (May). The stocking rate of 3.5 cows/ha allowed cows to maintain body weight and appears optimal for these pastures. The ability of the pastures to maintain DM yield with half the applied water input demonstrates that efficiencies may be gained by closer monitoring of soil and pasture production in autumn rather than the normal practice of fortnightly watering. This, combined with the longer grazing interval of 6 weeks and a stocking rate of 3.5 cows/ha, provided the most efficient use of the tropical grass pasture resource in late summer and autumn