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This study investigated cow-calf productivity in a 10-week, pasture-based, extended suckling system featuring part-time cow-calf contact and once-a-day milking. A total of 30 dairy cows and their calves were assigned to two treatments: (1) cow and calf managed in an extended suckling system; or (2) cow and calf separated at birth and managed as usual. Cow-calf pairs grazed together during the day and spent the night separated by fence-line contact. The dams were reunited with the calves after once-a-day milking every morning. The commercial treatment pairs were separated after birth, and cows were milked twice a day and managed within the farm herd. Commercial calves were reared and managed as per commercial Australian practices. Cow-calf dams yielded 9 L/cow/day less saleable milk (p < 0.001), and their milk had lower fat (p = 0.04) but a higher protein percentage (p < 0.001) than commercial cows during pre-weaning. However, milk yield and composition were comparable post-weaning. Dam-suckled calves gained weight faster and were therefore weaned 2 weeks earlier than commercial calves, which were offered 8 L/day milk. This study has demonstrated a novel system of extended cow-calf suckling that could be practical to implement in pasture-based dairies. The long-term effects and scalability of the extended suckling system described here require further validation.

Many lineages of parthenogenetic organisms have persisted through significant environmental change despite the constraints imposed by their fixed genotype and limited evolutionary potential. The ability of parthenogens to occur sympatrically with sexual relatives may in part be due to phenotypic plasticity in their responses to their environment, especially with respect to incubation temperature—a maternally selected trait. Here we measured the incubation temperatures selected by two lineages of triploid parthenogenic geckos in theHeteronotia binoeicomplex by allowing them to deposit clutches along a thermal gradient. The average nest temperature selected was 28.4°C, with no significant differences between parthenogenic races or individual clones. To investigate the effect of nest‐temperature variability on physiological and morphological traits, we incubated eggs from different races at one of four incubation regimes ( \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $32^{\\circ }\\pm 0^{\\circ }$ \\end{document} , ±3°, ±5°, or ±9°C). Embryos incubated at constant 32°C developed faster than embryos reared under increasing extremes of diel temperature fluctuation (±3°, ±5°C), and incubation at \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $32^{\\circ }\\pm 9^{\\circ }$ \\end{document} C was unsuccessful. Incubation regime had no effect on the body size, preferred substrate temperature, or mass‐specific \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $\\dot{\\mathrm{V}}\\textsc{$o$}_{2}$ \\end{document} of hatchlings. However, parthenogenic race had a significant effect on egg mass, tail length, snout‐to‐vent length, total length, and \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $\\dot{\\mathrm{V}}\\textsc{$o$}_{2}$ \\end{document} . We conclude that developmental traits are strongly influenced by clonal genotypes in this parthenogenic complex but are well buffered against fluctuations in incubation temperature.

Oxygen availability is highly variable during salmonid incubation in natural redds and also in aquaculture incubation systems. Hypoxia generally decreases growth and aerobic metabolism prior to hatching, in parallel with eliciting physiological modifications that enhance oxygen delivery. However, it is less-well known whether developmental hyperoxia can drive the opposite effect. Moreover, there is insufficient understanding of stage-specific developmental windows during which ambient oxygen availability may be of greater or lesser impact to incubating embryos. Here, we tested the effects of hypoxia (50% dissolved oxygen: DO, % air saturation) and hyperoxia (150% DO) on the growth, routine aerobic metabolism (\\[\\dot {M}{{\\text{O}}_{{\\text{2rout}}}\\]) and hypoxia tolerance (O2crit) of Atlantic salmon (Salmo salar) during seven developmental windows throughout incubation. Embryos exposed to hyperoxia (150% DO) did not differ from the normoxic group in growth, \\[\\dot {M}{{\\text{O}}_{{\\text{2rout}}}\\] or O2crit at any developmental window. In contrast, embryos exposed to hypoxia grew slower and had a lower \\[\\dot {M}{{\\text{O}}_{{\\text{2rout}}}\\], but had higher hypoxia tolerance (lower O2crit) than normoxic and hyperoxic counterparts. Interestingly, these differences were only apparent when the embryos were measured prior to hatching. Larvae (alevins) incubated in hypoxia following hatching grew similarly to normoxia-incubated alevins. Our results provide evidence that Atlantic salmon embryos are most sensitive to hypoxia prior to hatching, probably due to increasing (absolute) oxygen requirements concurrent with restricted oxygen diffusion through the egg. Moreover, the similarities between normoxia- and hyperoxia-incubated salmon demonstrate that embryos are not oxygen-limited under normoxic conditions.

Exposure to developmental hypoxia can have long-term impacts on the physiological performance of fish because of irreversible plasticity. Wild and captive-reared Atlantic salmon (Salmo salar) can be exposed to hypoxic conditions during development and continue to experience fluctuating oxygen levels as juveniles and adults. Here, we examine whether developmental hypoxia impacts subsequent hypoxia tolerance and aerobic performance of Atlantic salmon. Individuals at 8°C were exposed to 50% (hypoxia) or 100% (normoxia) dissolved oxygen (DO) saturation (as percent of air saturation) from fertilization for ∼100 d (800 degree days) and then raised in normoxic conditions for a further 15 mo. At 18 mo after fertilization, aerobic scope was calculated in normoxia (100% DO) and acute (18 h) hypoxia (50% DO) from the difference between the minimum and maximum oxygen consumption rates (Mo2 min and Mo2 max, respectively) at 10°C. Hypoxia tolerance was determined as the DO at which loss of equilibrium (LOE) occurred in a constantly decreasing DO environment. There was no difference in Mo2 min, Mo2 max, or aerobic scope between fish raised in hypoxia or normoxia. There was some evidence that hypoxia tolerance was lower (higher DO at LOE) in hypoxia-raised fish compared with those raised in normoxia, but the magnitude of the effect was small (12.52% DO vs. 11.73% DO at LOE). Acute hypoxia significantly reduced aerobic scope by reducing Mo2 max, while Mo2 min remained unchanged. Interestingly, acute hypoxia uncovered individual-level relationships between DO at LOE and Mo2 min, Mo2 max, and aerobic scope. We discuss our findings in the context of developmental trajectories and the role of aerobic performance in hypoxia tolerance.

Hypoxic stress can alter conspecific phenotype and additionally alter phenotypes of the filial generation, for example, via maternal or epigenetic processes. Lasting effects can also be seen across development and generations even after stressors have been removed. This study utilized the model of rapidly developing, parthenogenetic Daphnia to examine the intraspecific variability of response of exposure of a parental generation to hypoxia (4 kPa) within a single clone line across development, across broods, and across generations. Body mass across development and reproductive output were monitored in the parental generation and the first three broods of the first filial generation (which were not directly exposed to hypoxia). O2 consumption across a wide Po2 range (normoxia to anoxia) was assessed to determine whether exposure of the parental generation to hypoxia conferred hypoxia tolerance on the offspring and whether this transgenerational, epigenetic phenomenon varied intraspecifically. Differences in mass occurred in both the parental generation (hypoxia-exposed smaller during brood 1 and brood 2 neonate production) and the filial generation (e.g., brood 1 and 2 neonates from hypoxic mothers were initially smaller than control neonates). However, differences in mass were not accompanied by changes in reproductive output (assessed by brood number and neonate size). At day 0, first filial generation brood 1 neonates from hypoxia-exposed mothers had a higher metabolic rate than control neonates. However, this effect, like that of body mass, dissipated with development within a brood but also with subsequent broods. An isometric scaling exponent for was repeatedly observed across a wide Po2 range (21-2 kPa) throughout neonatal development.

Hemoglobin concentration is commonly measured by point-of-care systems for many animal studies. The HemoCue Hb 201+ overestimated hemoglobin in blue-tongued skinks and diploid and triploid Atlantic salmon. The overestimation was systematic in both species, and therefore hemoglobin determined by the HemoCue can be corrected using appropriate calibration equations.AbstractHaemoglobin concentration ([Hb]) is measured for a wide variety of animal studies. The use of point-of-care devices, such as the HemoCue, is becoming increasingly common because of their portability, relative ease of use and low cost. In this study, we aimed to determine whether the [Hb] of blue-tongued skink (Tiliqua nigrolutea) blood can be determined accurately using the HemoCue and whether the HemoCue overestimates the [Hb] of reptile blood in a similar manner to fish blood. Additionally, we aimed to test whether ploidy affected [Hb] determined by the HemoCue using blood from diploid and triploid Atlantic salmon (Salmo salar). The HemoCue Hb 201+ systematically overestimated [Hb] in both blue-tongued skinks and Atlantic salmon, and there was no difference between calibration equations determined for diploid or triploid salmon. The overestimation was systematic in both species and, as such, [Hb] determined by the HemoCue can be corrected using appropriate calibration equations.

Hypoxia in aquatic ecosystems is becoming increasingly prevalent, potentially reducing fish performance and survival by limiting the oxygen available for aerobic activities. Hypoxia is a challenge for conserving and managing fish populations and demands a better understanding of the short- and long-term impacts of hypoxic environments on fish performance. Fish acclimate to hypoxia via a variety of short- and long-term physiological modifications in an attempt to maintain aerobic performance. In particular, hypoxia exposure during early development may result in enduring cardio-respiratory modifications that affect future hypoxia acclimation capacity, yet this possibility remains poorly investigated. We incubated Atlantic salmon (Salmo salar) in normoxia (~100% dissolved oxygen [DO, as percent air saturation]), moderate hypoxia (~63% DO) or cyclical hypoxia (100–25% DO daily) from fertilization until 113 days post-fertilization prior to rearing all groups in normoxia for a further 8 months. At ~11 months of age, subsets of each group were acclimated to hypoxia (50% DO) for up to 44 days prior to haematology, aerobic metabolic rate and hypoxia tolerance measurements. Hypoxia exposure during incubation (fertilization to 113 days post-fertilization) did not affect the haematology, aerobic performance or hypoxia tolerance of juvenile salmon in later life. Juveniles acclimated to hypoxia increased maximum aerobic metabolic rate and aerobic scope by ~23 and ~52%, respectively, when measured at 50% DO but not at 100% DO. Hypoxia-incubated juveniles also increased haematocrit and haemoglobin concentration but did not affect acute hypoxia tolerance (critical oxygen level and DO at LOE). Thus, while Atlantic salmon possess a considerable capacity to physiologically acclimate to hypoxia by improving aerobic performance in low oxygen conditions, we found no evidence that this capacity is influenced by early-life hypoxia exposure.

Hypoxia in aquatic ecosystems is becoming increasingly prevalent, potentially reducing fish performance and survival by limiting the oxygen available for aerobic activities. Hypoxia is a challenge for conserving and managing fish populations and demands a better understanding of the short- and long-term impacts of hypoxic environments on fish performance. Fish acclimate to hypoxia via a variety of short- and long-term physiological modifications in an attempt to maintain aerobic performance. In particular, hypoxia exposure during early development may result in enduring cardio-respiratory modifications that affect future hypoxia acclimation capacity, yet this possibility remains poorly investigated. We incubated Atlantic salmon (Salmo salar) in normoxia ( 100% dissolved oxygen [DO, as percent air saturation]), moderate hypoxia ( 63% DO) or cyclical hypoxia (100-25% DO daily) from fertilization until 113 days post-fertilization prior to rearing all groups in normoxia for a further 8 months. At 11 months of age, subsets of each group were acclimated to hypoxia (50% DO) for up to 44 days prior to haematology, aerobic metabolic rate and hypoxia tolerance measurements. Hypoxia exposure during incubation (fertilization to 113 days post-fertilization) did not affect the haematology, aerobic performance or hypoxia tolerance of juvenile salmon in later life. Juveniles acclimated to hypoxia increased maximum aerobic metabolic rate and aerobic scope by 23 and 52%, respectively, when measured at 50% DO but not at 100% DO. Hypoxia-incubated juveniles also increased haematocrit and haemoglobin concentration but did not affect acute hypoxia tolerance (critical oxygen level and DO at LOE). Thus, while Atlantic salmon possess a considerable capacity to physiologically acclimate to hypoxia by improving aerobic performance in low oxygen conditions, we found no evidence that this capacity is influenced by early-life hypoxia exposure.

Hypoxic stress can alter conspecific phenotype and additionally alter phenotypes of the filial generation, for example, via maternal or epigenetic processes. Lasting effects can also be seen across development and generations even after stressors have been removed. This study utilized the model of rapidly developing, parthenogeneticDaphniato examine the intraspecific variability of response of exposure of a parental generation to hypoxia (4 kPa) within a single clone line across development, across broods, and across generations. Body mass across development and reproductive output were monitored in the parental generation and the first three broods of the first filial generation (which were not directly exposed to hypoxia). O2consumption across a wide Po 2range (normoxia to anoxia) was assessed to determine whether exposure of the parental generation to hypoxia conferred hypoxia tolerance on the offspring and whether this transgenerational, epigenetic phenomenon varied intraspecifically. Differences in mass occurred in both the parental generation (hypoxia-exposed smaller during brood 1 and brood 2 neonate production) and the filial generation (e.g., brood 1 and 2 neonates from hypoxic mothers were initially smaller than control neonates). However, differences in mass were not accompanied by changes in reproductive output (assessed by brood number and neonate size). At day 0, first filial generation brood 1 neonates from hypoxia-exposed mothers had a higher metabolic rate than control neonates. However, this effect, like that of body mass, dissipated with development within a brood but also with subsequent broods. An isometric scaling exponent for was repeatedly observed across a wide Po 2range (21–2 kPa) throughout neonatal development.