Showing papers on "Compensatory growth (organism) published in 2017"

Molecular Physiology of Feed Efficiency in Beef Cattle

Abstract: This chapter reviews the molecular physiology of feed efficiency in beef cattle and highlights significant variation across a variety of metabolic organs and constituent biochemical processes amongst animals of contrasting feed efficiency phenotype. It discusses the main biological processes that govern feed efficiency and nutrient utilisation of cattle and the observed variation cited in the published literature to-date. The chapter focuses on both inherent inter-animal variation in situations where feed is available on an ad libitum basis as well as where feed nutrient supply is managed, that is, to exploit compensatory growth. The voluntary feed intake of cattle is regulated by a combination of physical and metabolic mechanisms, with the relative importance of these two processes dependent on prevailing dietary characteristics. Variation in nutrient partitioning and subsequent implications for differences in body composition between cattle divergent for feed efficiency may be influenced through differing intermediary metabolism.

Regional asymmetry of metabolic and antioxidant profile in the sciaenid fish shi drum (Umbrina cirrosa) white muscle. Response to starvation and refeeding.

Abstract: The objective of the present study is to characterize the metabolic and antioxidant profile of white muscle of shi drum in two sites of the body, anterior dorsal (AM) and posterior dorsal (PM) portions. In addition, it will be analyzed the possible effect of starvation and a subsequent refeeding, with two different protocols, pair feeding and ad libitum. Activities of key enzymes of intermediary metabolism and of antioxidant enzymes, as well as lipid peroxidation, as an index of oxidative stress, were evaluated. The results indicate the existence of a regional asymmetry of the metabolic capacities of the white muscle of shi drum, which is likely related to the different contribution to swimming of the body regions examined. Starvation induces a metabolic depression that is more marked in those activities that support burst swimming in PM, while those activities supporting maintenance requirements are conserved. The greatest energy demands during starvation appear to lie in AM, which showed the highest oxidative metabolism rate. The increased use of fatty acids as energy source for AM leads to oxidative stress. A period of more than four weeks of refeeding for full restoration of metabolic capacities in AM is needed, probably related to the higher muscle mass located in this region. On the contrary, all enzyme activities in PM returned to control levels in both refeeding protocols, but pair feeding seems to be advantageous since compensatory growth has been taking place without signs of oxidative stress. This work was addressed to gain knowledge on the physiology of a promising fish species in aquaculture like shi drum. The results displayed here show how the starving and further re-feeding events could generate oxidative stress situations characterized by high lipid peroxidation levels which may influence negatively on the quality of the edible part of the fish. This study opens an interesting field on this fish species which deserves being investigated in the future.

Intraspecific priority effects modify compensatory responses to changes in hatching phenology in an amphibian

Abstract: In seasonal environments, modifications in the phenology of life-history events can alter the strength of time constraints experienced by organisms. Offspring can compensate for a change in timing of hatching by modifying their growth and development trajectories. However, intra- and interspecific interactions may affect these compensatory responses, in particular if differences in phenology between cohorts lead to significant priority effects (i.e. the competitive advantage that early-hatching individuals have over late-hatching ones). Here, we conducted a factorial experiment to determine whether intraspecific priority effects can alter compensatory phenotypic responses to hatching delay in a synchronic breeder by rearing moor frog (Rana arvalis) tadpoles in different combinations of phenological delay and food abundance. Tadpoles compensated for the hatching delay by speeding up their development, but only when reared in groups of individuals with identical hatching phenology. In mixed phenology groups, strong competitive effects by non-delayed tadpoles prevented the compensatory responses and delayed larvae metamorphosed later than in single phenology treatments. Non-delayed individuals gained advantage from developing with delayed larvae by increasing their developmental and growth rates as compared to single phenology groups. Food shortage prolonged larval period and reduced mass at metamorphosis in all treatments, but it did not prevent compensatory developmental responses in larvae reared in single phenology groups. This study demonstrates that strong intraspecific priority effects can constrain the compensatory growth and developmental responses to phenological change, and that priority effects can be an important factor explaining the maintenance of synchronic life histories (i.e. explosive breeding) in seasonal environments.

Effects of starving and re-feeding strategies on the growth performance and physiological characteristics of the juvenile tongue sole (Cynoglossus semilaevis)

Abstract: Starving and re-feeding trials were conducted to evaluate the effects of starvation duration and recovery times on the growth performance and physiological characteristics of juvenile tongue sole Cynoglossus semilaevis, which included growth, body composition, intestinal morphology and digestive enzymes activities. The fish starved for one (D1), two (D2) and four (D4) days, respectively, were recovered for three (R3, R6, R12), seven (R7, R14, R28) and eleven (R11, R22, R44) folds of starvation days while the control fish were fed constantly. The experiment was conducted for 96 days. The fish individuals in D1R11, D2R14 and D2R22 caught up in weight with the control, indicating that complete compensatory growth existed in these fish individuals. The highest body weight gain and total specific growth rates were observed in D2R22. Food intake increased significantly in most treatments in comparison with that of the control except for D1R7 and D2R22 (P < 0.05). Food conversion efficiency and apparent digest coefficient in D2R22 were significantly promoted, being higher than that of the control (P < 0.05). The activities of trypsin and lipase were found to be closely related to the growth performance. The activities of liver and hindgut trypsin, also midgut and hindgut lipase in D2R22 were significantly higher than those of the control (P < 0.05). The fold height (HF) of foregut and midgut increased significantly in D2R22, and HF decreased significantly in D1R3, D2R6 and D4R12 (P < 0.05). On our findings, we may conclude that the optimum starving and re-feeding strategy is starving for 2 days and re-feeding for 22 days. And in this starving and re-feeding strategy, the compensatory growth could be mostly attributed to the promotion of food conversion efficiency and digestibility coefficiency.

The role of microbiota in compensatory growth of protein-restricted rats

Abstract: Summary Compensatory growth is a physiological phenomenon found in both humans and animals. However, the underlying mechanisms are unclear. In this study, for the first time, we investigated the role of microbiota in compensatory growth induced by protein restriction using a rat model. Weaned Sprague-Dawley rats were fed a low protein diet (L group), a normal protein diet (N group) and a low protein diet for 2 weeks followed by a normal protein diet (LN group). The results showed that in contrast with the inhibited growth of rats in the L group, compensatory growth was observed in the LN group. Meanwhile, rats in the LN group had increased concentrations of total short chain fatty acids, particularly butyrate, and an altered bacterial composition with modified abundances of Peptostreptococcaceae, Bifidobacteriaceae, Porphyromonadaceae and Prevotellaceae in the colonic content. Furthermore, gene expression analysis indicated that the rats that experienced compensatory growth had improved barrier function and innate immune function in the colon. Our data revealed the importance of colonic microbiota in achieving compensatory growth.

Organizing effects of adverse early-life condition on body mass, compensatory growth and reproduction: experimental studies in rock pigeons

Abstract: Early-life food conditions can have profound impact on adult behavioural performance. In song birds, early-life food conditions affect adult physiology and cognitive performance such as song learning and spatial learning. However, effects on reproductive behaviour other than song, such as visual courtship display, pair formation, and egg laying, which are all important determinants of fitness, received hardly any attention. In this study, rock pigeons Columba livia were raised either in a food ad-libitum or at impoverished (quality) and restricted (quantity) food conditions, in which the latter was applied for either 26 or 8 d after hatching and in slightly different severity. Their growth and reproductive behaviour in adulthood was analysed under semi-natural conditions. Impoverished and restricted food (IRF) negatively affected adult body mass, pair-bonding behaviour, courtship (males) and being courted (females), and induced incomplete compensatory growth. Further analyses suggest that the effects of IRF on behaviour could result from the strong effects on body mass, and perhaps also from detrimental effects of compensatory growth. These results provide evidence that adverse early-life condition can negatively impact on reproductive success, as suggested by the significant effect on egg production, which will very likely lead to a lower life-time fitness. The detrimental effects on male courtship indicate that IRF can affect sexual displays via other pathways than by impaired cognition as has been suggested for bird song, since courtship in the pigeons is not learned.

Compensatory growth of juvenile brown flounder Paralichthys olivaceus following low temperature treatment for different periods

Abstract: We investigated the effects of low temperature (8.5°C) on the growth and feeding rates and feed conversion efficiency of juvenile P. olivaceus with an average initial weight of 3.87 ± 0.06 g (mean ± SE). Fish were exposed to 8.5°C for 0 (control), 1, 2, 3 and 4 weeks, and then to 20°C for 10, 9, 8, 7 and 6 weeks, respectively. Low temperature clearly led to growth depression. The weight of fish exposed to low temperature for 1 week was restored to that of control, while that of fish exposed to low temperature longer was significantly decreased (P 0.05). Feeding rate and feed conversion efficiency were reduced at low temperature in juvenile P. olivaceus. The compensatory growth of juvenile P. olivaceus may therefore be attributed to the improvement of feeding rate. Our results suggested that growth depression occurs when juvenile P. olivaceus are exposed to low temperature for more than one week.

Performance of wild brown trout in relation to energetic state and lab-scored activity during the early-life survival bottleneck

Abstract: The early life stage is typically a selective bottleneck during which individual performance is important for survival. We investigated size, energetic state, and activity, in relation to recapture probability in the youngest free-swimming stage of a territorial fish, the brown trout. In two experiments, we induced compensatory growth in wild-caught brown trout fry, using a restriction-refeeding protocol. Upon refeeding in the laboratory, the restricted trout showed compensatory growth in mass, but not in length. During this compensatory growth phase, we released the fish into their native stream habitat and then recaptured them after 1 month to assess survival and growth. Despite not having fully compensated body size at release, restricted fish did not show continued growth compensation in the stream, indicating that the natural environment limits growth capacity during early life. Individual baseline activity was scored in open-field tests before and after food restriction and was found repeatable but not significantly affected by growth manipulations. Under natural conditions, we found a positive association between open-field activity and survival (as indicated by recapture probability), but no significant differences between food-restricted and control fish. Initial body length positively influenced survival in the first experiment (early summer), but not in the second (late summer). These results contrast with the assumption that high baseline activity should be riskier in natural environments. For territorial animals, we hypothesize that activity is associated with high aggression and territoriality, which facilitates access to high-quality territories providing both shelter from predation and reduced starvation risk, which reduces mortality risk. In the early critical life stage, more active brown trout are better survivors. This finding, which contradicts general assumptions about the balance between predator exposure and food intake, could possibly be due to trout being highly territorial species in which active individuals can claim the best territories. We also find that young trout are likely limited in growth rate by environmental conditions in the wild, as growth compensation following food restriction is possible in the lab, but not realized in natural streams.

Fitness implications of sex-specific catch-up growth in Nephila senegalensis, a spider with extreme reversed SSD

Abstract: Background Animal growth is often constrained by unfavourable conditions and divergences from optimal body size can be detrimental to an individual's fitness, particularly in species with determinate growth and a narrow time-frame for life-time reproduction. Growth restriction in early juvenile stages can later be compensated by means of plastic developmental responses, such as adaptive catch-up growth (the compensation of growth deficits through delayed development). Although sex differences regarding the mode and degree of growth compensation have been coherently predicted from sex-specific fitness payoffs, inconsistent results imply a need for further research. We used the African Nephila senegalensis, representing an extreme case of female-biased sexual size dimorphism (SSD), to study fitness implications of sex-specific growth compensation. We predicted effective catch-up growth in early food-restricted females to result in full compensation of growth deficits and a life-time fecundity (LTF) equivalent to unrestricted females. Based on a stronger trade-off between size-related benefits and costs of a delayed maturation, we expected less effective catch-up growth in males. Methods We tracked the development of over one thousand spiders in different feeding treatments, e.g., comprising a fixed period of early low feeding conditions followed by unrestricted feeding conditions, permanent unrestricted feeding conditions, or permanent low feeding conditions as a control. In a second experimental section, we assessed female fitness by measuring LTF in a subset of females. In addition, we tested whether compensatory development affected the reproductive lifespan in both sexes and analysed genotype-by-treatment interactions as a potential cause of variation in life-history traits. Results Both sexes delayed maturation to counteract early growth restriction, but only females achieved full compensation of adult body size. Female catch-up growth resulted in equivalent LTF compared to unrestricted females. We found significant interactions between experimental treatments and sex as well as between treatments and family lineage, suggesting that family-specific responses contribute to the unusually large variation of life-history traits in Nephila spiders. Our feeding treatments had no effect on the reproductive lifespan in either sex. Discussion Our findings are in line with predictions of life-history theory and corroborate strong fecundity selection to result in full female growth compensation. Males showed incomplete growth compensation despite a delayed development, indicating relaxed selection on large size and a stronger trade-off between late maturation and size-related benefits. We suggest that moderate catch-up growth in males is still adaptive as a 'bet-hedging' strategy to disperse unavoidable costs between life-history traits affected by early growth restriction (the duration of development and adult size).

Cyclic feed restriction on growth compensation of Penaeus monodon (Fabricius): science meets practice

Abstract: Effects of cyclic feed restriction on compensatory growth (CG) performance of Penaeus monodon, sediment loading and water productivity in a grow-out production system were examined in 119 days of culture duration. Among different feed management protocols (T1: Regular feeding, 4-times a day; T2: 2-weeks feeding followed by 1-week no feed; T34-weeks feeding followed by 1-week no feed), overall crop performance was in the similar line in both T1 and T2 except significantly (P<0.05) low AFCR and higher FE in T2. This was probably due to the prevailing optimal salinity (19.1 ± 1.8 psu), DO (6.1±0.7 ppm) and water pH (7.54±0.13). Among T2 and T3, there was no significant (P<0.05) variation in overall crop performance except in SGR and MBW. This was probably due to the longer refeeding periods after cyclic food deprivation that successfully triggered full CG response in T3(CGI, 98-105%) and partial CG in T2 (89-96%).Shrimp on the cyclic feed restriction may have better used pond resources by increasing the consumption of natural productivity that increased the feed efficiency (71.6-73.5).

Preliminary investigations of the physiological adjustments associated with compensatory growth in juvenile brook charr (Salvelinus fontinalis).

Abstract: Various physiological factors suspected to govern or be influenced by growth or feed intake of brook charr (80–120 g) were examined under long and short fasting periods during the year. A control (fed to satiation) was included. During winter, fasting (14 and 28 days) followed by refeeding led to a complete compensation. In summer, longer fasting (39 and 61 days) was applied to exacerbate the physiological response. Compensatory growth was observed in the restricted groups, and overall, adjustments/variations in growth and physiological indicators (feed conversion ratio, organosomatic index, enzymatic activities [CS, TRY, CHY]) were more pronounced. Degree of compensation reached was positively related to the deprivation duration. The summer experiment clearly suggests that compensatory growth takes place in two stages after a long starvation period (61 days): (1) restoration of the digestive system (PSI) followed by enzyme activities (trypsin and chymotrypsin) and (2) rebuilding of somatic tissues.

Alteration in expression of atrogenes and IGF-1 induced by fasting in Nile tilapia Oreochromis niloticus juveniles

Abstract: The growth rate of farmed fish is an important factor regarding aquaculture success. An understanding of the cellular events that occur in skeletal muscle when fish undergo periods of fasting and refeeding provides information useful in developing alternative feeding strategies for improving muscle growth in commercially cultivated species. To evaluate the effect of 1–3 weeks of fasting and 10 weeks of refeeding in Nile tilapia juveniles, we analyzed the growth performance and changes in muscle cellularity and the expression of the following growth and muscle related genes: MyoD, myogenin, IGF-1, IGF-1 receptor, MuRF-1, atrogin-1 and myostatin. Reduced body mass was observed in all three groups of fasted fish during their time off feed, and 10 weeks of refeeding resulted in partial compensatory growth of body mass. No differences in the frequency of white muscle fiber diameters were observed between fasted and fed control fish treatments. However, changes in gene expression induced by fasting and refeeding were found. IGF-1 receptor, ubiquitin ligases MuRF1 and atrogin-1 expression increased during the 1–3 weeks of fasting, while IGF-1 levels dropped significantly (P < 0.001) compared to the control treatment. Furthermore, myogenin mRNA level in fish submitted to 3 weeks of fasting was higher in comparison to the control treatment (P < 0.05). Overall, our results showed that 1–3 weeks of fasting can induce muscle atrophy activation in Nile tilapia juveniles, and 10 weeks of refeeding is enough to induce only partial compensatory growth.

227 Compensatory body protein gain in newly weaned pigs.

Abstract: Hannah Golightly Good afternoon and thank you for joining us for the fourth presentation in a multi-part webinar series by The Ontario Swine Research Network. My name is Hannah Golightly, and I'm a second-year veterinary student here at the Ontario Veterinary College, who has been assisting with the OSRN activities. For those of you who haven't participated in a previous webinar in the series, the OSRN has been formed by faculty at the University of Guelph and representatives from Ontario Pork, OMAFRA and the Swine Veterinary Community. The goal of the network is to enhance and improve the timeliness and accuracy of the U of G swine research results and activities to end-users.

Compensatory growth in Nile tilápia (Oreochromis niloticus).

Abstract: The Nile tilapia (Oreochromis niloticus) has good characteristics for production among the fish species grown in Brazil, due to numerous productive qualities and that its production is increasing every year. This study aimed to evaluate the compensatory growth in the strain of Nile tilapia Genomar Supreme generation 14. Fish approximately 380 g were cultivated in two re-circulating water systems. In one treatment, tilapias stayed feeding restriction for 7 days, and after this period were re-feeding until 21 days of treatment; while the other system were fed daily with a common commercial feed the crude protein content 28%. At 0, 7 and 21 days was done the sampling 12 fish per treatment. The water parameters were considered ideal for the cultivation of the species. The standard length, body size and perimeter peduncle showed no difference in the different ages and in different treatments. After 7 days (after the fasting period) is consisted that the weight (333,8g) restriction group was lower compared to the control group (393,1g), but at 21 days the weight of 407.1 and Tilapia 402.4 (control and restriction respectively) in both treatments showed no difference, indicating a total compensation. The

Effect of early feed restriction on body weight and compensatory growth in Label Rouge broiler chickens

Abstract: This research was conducted to assess the compensatory gain in birds that have suffered severe food restriction and a reduced growth in its initial phase. A total of 144 birds were used in the Label Rouge lineage with average initial weight 239.90 ± 76.80 g, from 28 to 49 days. The experimental design used was a completely randomized design, where the birds were distributed in 18 boxes, containing 3 treatments and 6 replicates of 8 birds per cage. The treatments were as follows: birds with body weight of 150.73 ± 12.62 g, between weighing from 239.79 ± 13.14 g and heavy weight of 329.17 ± 24.89 g in different periods, from 28 to 35, 35 to 42 and 42 to 49 days of age, respectively. In relation to weight gain, the heavy birds, obtained better results when compared to the other. The feed consumption has changed in the three periods and, in the period of 42 to 49 days, the treatments did not differ among themselves. Feed conversion rates (p = 0.127) and feasibility (p = 0.6163) of birds do not differ in different periods.

Potential of Leucaena (Leucaena leucocephala) for Compensatory Growth on Anglo-Nubian Crossbred Male Goats

Abstract: This study was carried out to evaluate the potential of leucaena ( Leucaena leucocephala ) as the sole diet after restriction of feeding in order to elevate compensatory growth during re-alimentation. Twelve Anglo-Nubian crossbred male goats, with an average body weight of 17.50 kg, were assigned to 3 treatments, with 4 replicates, in a completely randomized design (CRD), where all treatments were under 3 feeding regimes, viz . pre-feed restriction, feed restriction, and re-alimentation. All animals were allotted to normal feeding and fed with Pangola hay and meal concentrate to promote an average daily gain (ADG) of 100 g in the initial period for 3 weeks. During the feed restriction period, animals in Treatment 1 were continuously fed at the same level as in the pre-restriction (normal growth/control group), while the animals in Treatments 2 and 3 (restricted groups) were kept at feeding levels of 47.5 and 67.5 % below maintenance, based on NRC (2007), for 4 weeks. In the final period of re-alimentation (7 weeks), the normal growth group was given Pangola hay and meal concentrate at the same level as in the pre-restriction period while restricted groups were subjected to ad libitum sole leucaena feeding until the end of the trial. The results showed that average daily gain (ADG) and feed intake did not differ among the treatments during the pre-feed restriction while, in the restriction feeding period, the restricted groups had lower means (P < 0.01) than the normal growth group. In the re-alimentation period, total dry matter intake was not significantly different among treatments. It is pointed that there were 2 sub-periods during the re-alimentation period where total dry matter intake during the compensatory growth and the normal growth were not significantly different. However, the compensatory growth had been achieved within 2 weeks, indicating a higher ADG of 141.25 and 158.57 g in the restricted groups, compared to 106 g in the control group. Afterwards, the sub-period of normal growth (5 weeks) was followed with a lower ADG in the restricted groups than that in the control group. It can be concluded that the potential of single leucaena feeding for compensatory growth after restriction feeding can be achieved within a short period during re-alimentation, due to the limitation of fiber enrichment in leucaena.

COMPENSATORY GROWTH OF Oreochromis niloticus SELECTED STRAIN FROM BOGOR, WEST JAVA

Abstract: Inefficient feed management strategy in aquaculture will increase the fish production cost. One of the most effective strategies to solve this problem is through a better understanding of the compensatory growth of cultured fish. O. niloticus BEST tilapia strain (total length: 7.23 ± 0.11 cm mean ± SD; Body weight: 7.04 ± 0.08 g mean ± SD) were reared in aquariums at 26.3 ± 1.4oC for 10 weeks. During the experiment, the control group was fed twice a day. The other two groups were deprived of food for one and two weeks and then fed twice a day during refeeding period. At the end of the experiment, the fish deprived for one week had a body weight, biomass and specific growth rate that were not significantly different from the control group. The body weight, biomass and specific growth rate of fish deprived for two weeks were significantly lower than the other groups. This study revealed that concentrations of ash and lower concentrations of protein and lipid on the deprived groups were higher compared to those without feed deprivation. Mortality of fish was lower than 9% and not significantly different among the treatments. Fish aggressive behavior was the main reason for injuries and death. Given the results, BEST tilapia strain was only able to reach complete growth compensation not longer than one week deprivation period. The results of the present study could be applied as basic information for further research on feeding management of BEST tilapia strain.

A Compensatory Growth like Analysis of Common Carp Cyprinus carpio L. among Different Combinations in Full Diallel Crossing

Abstract: Supplementary Fig. S1. The compensatory index, a method to measure the catch-up growth: A is the difference of body weight during first growth stage (catch-up group influenced by restricted factor and control group with no influence by such factor), B is the difference of body weight during second growth stage where the catch-up group were feed as control group. Supplementary Table S1.YN effect of different combinations observed.

Compensatory and catch-up growth in cattle

Abstract: Variation in nutrition leads to periods of restricted and accelerated changes in the liveweight of cattle, but less is known about the effect of level of nutrition and/or specific nutrients on skeletal growth. The endochondral ossification process at the epiphyseal growth plate drives longitudinal bone growth and by inference sets growth in skeletal muscle via a passive stretch mechanism. The physiological and morphological mechanism behind animal growth that drives adaptation of mammals during the transition from a low to high plane of nutrition remains a major biological question. Two experiments examined the effect of protein and energy on skeletal growth the perspective of the dimensional changes, trabecular bone remodelling (histology and bone biomarkers) and hormone. Data was then collated from these and other experiments conducted within this laboratory to develop a growth curve in liveweight-for-hip height of well-fed cattle and to identify deviations from this “normal” growth relationship. In the first experiment (Chapter 4), the effects of low and high crude protein (CP) content diets during metabolizable energy (ME) restriction on subsequent re-alimentation in Bos indicus and Bos taurus cattle were evaluated. Three treatment diets were applied; a control diet (High CP-High ME) and two restricted pair-fed ME intake diets differing in CP content (Low CP–Low ME and High CP-Low ME) for 93 days followed by re-alimentation of all treatment groups offered ad libitum access to the High CP-High ME diet for 103 days. In the second experiment (Chapter 5), a 2 x 5 factorial design was used to determine the effect of supplementation (0, 1, 2.5, 5, 10 g protein meal/kg LW.day) of a low CP hay during the first dry season (169 days) and weaning weight [Early (118 kg) vs. Normal (183 kg)] on long-term (~2 years) growth in liveweight and the skeleton and reproduction of replacement heifers in northern Australia. After the first dry season all treatment groups were subjected to the same level of nutrition by grazing the same pasture together. Across both experiments, higher plane of nutrition increased liveweight gain and skeletal elongation growth. Increases in ME and CP intake in cattle were positively associated with the height of proliferative and hypertrophic zones as well as with the diameter of terminal hypertrophic chondrocytes measured in growth plate biopsies of the tuber coxae. In addition, the diameter of terminal hypertrophic chondrocytes showed significant correlation with the broader measure of hip height gain in both experiments. Plasma bone-specific alkaline phosphatase and pyridinoline appeared to be effective bone biomarkers of formation and resorption in growing cattle respectively. Low ME intake severely reduced the plasma insulin and insulin-like growth factor 1 concentration in cattle, independent of CP intake. Cattle with the higher CP intake during ME restriction had higher concentration of triiodothyronine in the plasma and this was correlated with larger terminal hypertrophic chondrocytes at the tuber coxae growth plate as well as increased hip height gain. After nutritional restriction, cattle showed an increase in dry matter intake and liveweight gain for approximately 40 to 60 days after commencement of the re-alimentation phase followed by a subsequent decrease to values similar to unrestricted counterparts. Skeletal growth of previously restricted cattle was greater than unrestricted counterparts at the same age and was associated with increased proliferative and hypertrophic zones heights without differences in any measured plasma hormone concentration. Nutritional restriction at the early weaning weight did not cause permanent stunting, however it increased the time frame necessary to achieve reproductive target liveweights for satisfactory pregnancy rates (>80%) of replacement heifers in northern Australia. In Chapter 7, a “normal” liveweight-for-hip height relationship model was generated for well-fed Bos indicus cattle using data from the two experiments in this thesis as well as results from 4 other studies by our reseach group and a groups of mature fistulated steers. A decrease from the normal liveweight-for-hip height relationship was observed during nutritional restriction. The difference between the actual liveweight of an animal and the expected liveweight based on its hip height was identified as the “Liveweight gap”. A significant relationship was found between liveweight gain during compensatory growth and the Liveweight gap. The return to the normal liveweight-for-hip height relationship was associated with the decrease in dry matter intake during compensatory growth. It is concluded that cattle can exhibit catch-up growth in skeletal growth and compensatory growth in liveweight after a period of nutritional restriction. The results support the concept that catch-up growth in the skeleton is caused by a delay in growth plate senescence during nutritional restriction and that compensatory growth in weight is caused by a deviation from the liveweight-for-hip height relationship probably related to the passive stretch mechanism of bone length on skeletal muscle.

Spatial and temporal availability of Pacific salmon mediate compensatory growth in coastrange sculpin and sex-age specific spatial habitat use in brown bears

Abstract: Pacific salmon bring marine nutrients into freshwater ecosystems and provide food for countless species. Two major consumers of salmon along the Pacific coast are Coastrange Sculpin Cottus aleuticus and brown bears IIrsus arctos. I examined the effects of salmon temporal availability on the growth rate of sculpin and the spatial use of habitat by brown bears. In a study on Coastrange Sculpin I found that treatment groups denied food, in the form of salmon eggs, for two or three weeks exhibited compensatory growth following resumption of feeding in the laboratory and field respectively. The compensatory growth response was mediated by stream of origin and temperature, controlled in the laboratory. Sculpin groups from different streams of origin had different overall growth rates in the laboratory despite being housed under identical conditions. At the end of the food-deprivation period, sculpin housed at 20°C exhibited a 5% greater weight loss compared to sculpin housed at 10°C. High temperatures (20°C) prevented compensatory growth in one treatment group and lengthened the catch up period for other treatment groups compared to those housed at moderate temperatures (10°C). In a study on brown bear spatial and temporal use of habitat in Berners Bay, Alaska, I found that brown bears use salmon when they are available and reproductive status of adult female bears affects use of this resource. Brown bears used space within 250 meters of salmon spawning reaches 50% more when salmon were present (69%) than when salmon were not present (19%) at spawning reaches. However, sex, age, and reproductive status all affected the use of space near spawning reaches. When salmon were available, adult females without cubs used space similarly to dominant adult males, while females with cubs used space similarly to subdominant juveniles. Adult females without cubs used space within 100 meters of spawning reaches 13% more than females accompanied by cubs. Salmon runs in Southeast Alaska are exhibiting reduced duration and earlier arrival of migration timing, reducing their temporal availability to consumers. Additionally, climate change is projected to increase temperatures throughout Southeast Alaska. Warmer temperatures resulting from climate change may improve digestion and growth for sculpin in colder streams, but could negatively affect the ability of sculpin to exhibit compensatory growth. Reduced salmon availability and increased human activity might lead to changes in behavior and dominance among brown bears feeding on salmon.