Granulomatous enteritis in rainbow trout (Oncorhynchus mykiss) associated with soya bean meal regardless of water dissolved oxygen level.

This study investigated morphological changes associated with soya bean meal-induced enteritis (SBMIE) in distal intestine (DI) of rainbow trout (Oncorhynchus mykiss) fed a soya bean meal (SBM)-based diet and exposed to normoxia or hypoxia created by optimal and low water flow rates, respectively. A 28-day adaption period was followed by a 42-day challenge period where 600 fish were subjected to dietary challenge and/or hypoxia. Twelve tanks each containing 50 juvenile trout were assigned randomly in triplicate to each treatment. Histopathological and immunohistochemical evaluation revealed pathological features that have not previously been described in association with SBMIE. Vacuolar degeneration of epithelial cells mainly at the base of mucosal folds, epithelial cysts, epithelial dysplasia, necrosis, shedding of necrotic cells, and granulomatous inflammation including infiltration of enlarged, sometimes finely vacuolated or "foamy" macrophages, multinucleated giant cells and increased proliferation of fibroblasts were observed. Acid-fast bacteria were not detected in enlarged macrophages; however, these cells contained AB-PAS- and sometimes cytokeratin-positive material, which was interpreted to be of epithelial/goblet cell origin. Hypoxia did not affect the morphological changes in DI. These results suggest that SBM was associated with a granulomatous form of enteritis in DI of rainbow trout regardless of water oxygen level.

Comparison of endogenous loss and maintenance need for minerals in rainbow trout (Oncorhynchus mykiss) fed fishmeal or plant ingredient-based diets.

Mineral needs as affected by changes in dietary protein and oil sources were studied in rainbow trout. Duplicate groups (n = 30 fish per replicate) of rainbow trout (initial BW: 37 g) were fed either a fish meal/fish oil-based (M) or a complete plant ingredient (V)-based diet at four graded ration (R) levels [apparent satiation (AS), R75, R50 and R25 % of AS]; one treatment group was maintained under starvation. The feeding trial lasted 12 weeks at a water temperature of 17 °C. Dietary intake, apparent digestibility and initial and final whole-body composition data were used to calculate mineral gain which was regressed against digestible mineral intake (both expressed as mg or µg kg(-0.8) day(-1)). Starvation loss (SL), endogenous loss of fed fish (ELF, y-intercept at x = 0) and point of intake for zero balance (PZB, x-intercept at y = 0) were used as estimates of maintenance requirements. SL provided the lowest estimate, ELF provided the net requirement of a mineral for maintenance and PZB provided the digestible dietary intake required to meet maintenance (SL < ELF < PZB). Dietary ingredient composition did not significantly affect the digestible mineral supply required for maintenance (PZB) for any of the minerals (P, Mg, K, Cu and Zn) studied. However, ELF of micro-minerals such as Cu and Zn were significantly affected. The ELF of Cu was significantly lower and that of Zn was significantly higher in V group compared with M-fed fish. Further studies on the effects of such changes in dietary formulations on micro-mineral metabolism are warranted.

Dietary electrolyte balance affects the nutrient digestibility and maintenance energy expenditure of Nile tilapia.

Acid-base disturbances caused by environmental factors and physiological events including feeding have been well documented in several fish species, but little is known about the impact of dietary electrolyte balance (dEB). In the present study, we investigated the effect of feeding diets differing in dEB (-100, 200, 500 or 800 mEq/kg diet) on the growth, nutrient digestibility and energy balance of Nile tilapia. After 5 weeks on the test diet, the growth of the fish was linearly affected by the dEB levels (P< 0·001), with the lowest growth being observed in the fish fed the 800 dEB diet. The apparent digestibility coefficient (ADC) of fat was unaffected by dEB, whereas the ADC of DM and protein were curvilinearly related to the dEB levels, being lowest and highest in the 200 and 800 dEB diets, respectively. Stomach chyme pH at 3 h after feeding was linearly related to the dEB levels (P< 0·05). At the same time, blood pH of the heart (P< 0·05) and caudal vein (P< 0·01) was curvilinearly related to the dEB levels, suggesting the influence of dEB on postprandial metabolic alkalosis. Consequently, maintenance energy expenditure (MEm) was curvilinearly related to the dEB levels (P< 0·001), being 54 % higher in the 800 dEB group (88 kJ/kg(0·8) per d) than in the 200 dEB group (57 kJ/kg(0·8) per d). These results suggest that varying dEB levels in a diet have both positive and negative effects on fish. On the one hand, they improve nutrient digestibility; on the other hand, they challenge the acid-base homeostasis (pH) of fish, causing an increase in MEm, and thereby reduce the energy required for growth.

Dietary nutrient composition affects digestible energy utilisation for growth: a study on Nile tilapia (Oreochromis niloticus) and a literature comparison across fish species.

The effect of the type of non-protein energy (NPE) on energy utilisation in Nile tilapia was studied, focusing on digestible energy utilisation for growth (k(gDE)). Furthermore, literature data on k(gDE) across fish species were analysed in order to evaluate the effect of dietary macronutrient composition. A total of twelve groups of fish were assigned in a 2 × 2 factorial design: two diets ('fat' v. 'starch') and two feeding levels ('low' v. 'high'). In the 'fat'-diet, 125 g fish oil and in the 'starch'-diet 300 g maize starch were added to 875 g of an identical basal mixture. Fish were fed restrictively one of two ration levels ('low' or 'high') for estimating k(gDE). Nutrient digestibility, N and energy balances were measured. For estimating k(gDE), data of the present study were combined with previous data of Nile tilapia fed similar diets to satiation. The type of NPE affected k(gDE) (0.561 and 0.663 with the 'starch' and 'fat'-diets, respectively; P < 0.001). Across fish species, literature values of k(gDE) range from 0.31 to 0.82. Variability in k(gDE) was related to dietary macronutrient composition, the trophic level of the fish species and the composition of growth (fat:protein gain ratio). The across-species comparison suggested that the relationships of k(gDE) with trophic level and with growth composition were predominantly induced by dietary macronutrient composition. Reported k(gDE) values increased linearly with increasing dietary fat content and decreasing dietary carbohydrate content. In contrast, k(gDE) related curvilinearly to dietary crude protein content. In conclusion, energy utilisation for growth is influenced by dietary macronutrient composition.

Control of voluntary feed intake in fish: a role for dietary oxygen demand in Nile tilapia (Oreochromis niloticus) fed diets with different macronutrient profiles.

It has been hypothesised that, at non-limiting water oxygen conditions, voluntary feed intake (FI) in fish is limited by the maximal physiological capacity of oxygen use (i.e. an 'oxystatic control of FI in fish'). This implies that fish will adjust FI when fed diets differing in oxygen demand, resulting in identical oxygen consumption. Therefore, FI, digestible energy (DE) intake, energy balance and oxygen consumption were monitored at non-limiting water oxygen conditions in Nile tilapia fed diets with contrasting macronutrient composition. Diets were formulated in a 2 × 2 factorial design in order to create contrasts in oxygen demand: two ratios of digestible protein (DP):DE ('high' v. 'low'); and a contrast in the type of non-protein energy source ('starch' v. 'fat'). Triplicate groups of tilapia were fed each diet twice daily to satiation for 48 d. FI (g DM/kg(0·8) per d) was significantly lower (9·5%) in tilapia fed the starch diets relative to the fat diets. The DP:DE ratio affected DE intakes (P < 0·05), being 11% lower with 'high' than with 'low' DP:DE ratio diets, which was in line with the 11·9% higher oxygen demand of these diets. Indeed, DE intakes of fish showed an inverse linear relationship with dietary oxygen demand (DOD; R 2 0·81, P < 0·001). As hypothesised ('oxystatic' theory), oxygen consumption of fish was identical among three out of the four diets. Altogether, these results demonstrate the involvement of metabolic oxygen use and DOD in the control of FI in tilapia.

Interactive effects of protein and energy intake on nutrient partitioning and growth in Nile tilapia.

Studies of fish growth response to changes in dietary protein and energy content are often conducted with fish fed to apparent satiation or at fixed percentages of their body mass. Such designs result in simultaneous changes in protein and non-protein energy intake, thereby failing to distinguish their separate effects on nutrient partitioning and growth. The present study was designed to address this limitation and test the existence of distinct protein- and non-protein energy-dependent growth phases in Nile tilapia (Oreochromis niloticus). All-male Nile tilapia (63 g, SD = 1.3) were subjected to an 8 × 2 factorial design consisting of eight levels of digestible protein (DP) intake (0.44-1.25 g/day) and two levels of non-protein digestible energy (NPDE) intake (16.0 and 22.4 kJ/day). Fish (n = 960) were housed in 60-litre tanks with two replicates per treatment and hand-fed twice a day for 42 days. Nutrient balances were calculated from changes in body mass, analysed body composition and digestible nutrient intake. Linear regression models were compared to linear-plateau regression models to determine whether protein gain followed distinct protein- and non-protein energy-dependent phases or not. Body mass gain increased linearly with increasing DP intake and was significantly higher (2.6 vs 2.3 g/d, P < 0.05) in fish receiving a high NPDE intake. This increase mainly reflected a higher mean fat gain (0.29 vs 0.20 g/d) rather than a higher protein gain (0.42 vs 0.39 g/d) in fish fed a high vs low level of NPDE intake. The comparison of linear and linear-plateau models did not give clear support for the presence of distinct protein and non-protein energy-dependent phases in protein gain. These results indicate that non-protein energy intake has a modest protein-sparing potential, and that protein gain is simultaneously limited by protein and energy intake in Nile tilapia.

Coping strategies in farmed African catfish Clarias gariepinus. Does it affect their welfare?

The objective of this study was to assess whether and how coping strategies affect the welfare of African catfish Clarias gariepinus housed at low and high densities. Group composition influenced feed intake; re-active groups (comprised of 100% re-active fish) had a lower specific growth rate (G) and feed intake and a higher feed conversion ratio (R(FC)) than pro-active groups. Furthermore, re-active groups had a lower energy retention than pro-active groups. The latter was fully due to differences in feed intake, since energy partitioning (on % total gross energy intake basis) was similar among the group composition treatments. Fish held at high stocking density showed a higher R(FC) and feeding speed and a lower energy retention and agonistic behaviour. None of the measured variables was influenced by the interaction effect. In mixed groups, G and number of skin lesions seemed to be affected by different behavioural phenotypes at low stocking density, but not at high density. These results indicate that both stocking density and group composition affect physical and behavioural responses of C. gariepinus. Furthermore, physical and behavioural data of individual fish housed in mixed groups suggest that coping strategy affects the fitness of different behavioural phenotypes at low, but not at high, stocking density.

Kinetics of Lactobacillus plantarum 44a in the faeces of tilapia (Oreochromis niloticus) after its intake in feed.

AIMS: To study the kinetic passage of Lactobacillus plantarum 44a from feed to faeces of tilapia in order to calculate the number of Lactobacillus excreted. METHODS AND RESULTS: In a single-dose experiment, duplicate lots of 26 fish devoid of intestinal lactobacilli were fed with diets containing c. 4.5 x 10(11), 6.3 x 10(8), 6.0 x 10(5) and 0 CFU of Lact. plantarum 44a per single feed ration. In the multiple-dose experiment, duplicate lots of 30 fish each were supplied with a diet containing 1 x l0(11) CFU of Lact. plantarum 44a as follows: 14 times in 14 days, five times in 14 days, once in 14 days and zero times in 14 days. Faeces were periodically collected and analysed for their lactobacilli content by using a selective media. The kinetics of Lactobacillus in the faeces was described as a pulse signal defined by three parameters: theta, A(o) and the time. theta, was identified as the time to reach the peak (x axis) and A(o) was a constant. A(o) divided by e, was identified as the height of the peak (y axis). The area below the curve A(o)theta allowed the calculation of the total number of lactobacilli excreted. The ability of the mathematical model to describe the actual values was tested by a linear regression analysis. In most of the cases, the equations showed an intercept close to zero (P > 0.05) and angular coefficients near one. CONCLUSIONS: Lactobacillus plantarum 44a was excreted in short pulse signals described by a mathematical model which allowed calculating the area below the curve and consequently the survival rate. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides a quantitative method to study the kinetics of excretion of a probiotic bacterium in the faeces.

Time-related changes of the intestinal morphology of Atlantic salmon, Salmo salar L., at two different soybean meal inclusion levels.

Abstract Soybean meal (SBM) induces enteritis in the distal intestine of Atlantic salmon. The present study assesses the effects of SBM concentrations on the kinetics of the enteritis process. Fish of 300 g, kept at 12 degrees C, were fed diets with different SBM inclusions: 0%, 10% and 20% SBM for 57 days. Samples of the distal intestine of five fish per treatment were taken for histological and electron microscopical analysis. A semi-quantitative scoring system was used to assess the degree of the morphological changes induced by SBM feeding in the distal intestinal epithelium. The first signs of enteritis appeared earlier in the salmon fed the 20SBM diet than in those fed the 10SBM diet. Thereafter, the condition increased steadily, displaying no signs of recovery. Furthermore, at the lower concentration, the process marking the onset of enteritis began more gradually than at the higher concentration and it displayed a tendency to stabilize after 13-20 days of continuous feeding. Electron microscopy indicated that the endocytosis process was hampered at day 3 of 20SBM and at 7 days of 10SBM. Furthermore, a strong reduction of microvilli was already evident after 7 days of 20SBM feeding, thus indicating a decreased uptake capacity of the distal enterocytes. In addition, transformation and migration of eosinophilic granulocytes was observed, which, in combination with the lysozyme C immunoreactivity supports their protective role during the inflammatory process in the distal gut of Atlantic salmon. It can be concluded that the severity of enteritis and its kinetics are concentration-dependent, showing no signs of recovery during feeding with diets containing SBM.

Responses to apomorphine of pigs with different coping characteristics.

RATIONALE: Classification of pigs based on the degree of resistance they display in a so-called "backtest" seems, to a certain extent, predictive for their coping strategy. OBJECTIVE: The present study examined whether, as found in rodents, the behavioral response to apomorphine of pigs relates to individual coping characteristics. METHODS: During the suckling period pigs were subjected to the backtest. In this test, each pig is restrained on its back for 1 min and the resistance (i.e. number of escape attempts) is scored. Pigs classified as low-resisting (LR, n=10) or high-resisting (HR, n=10) were selected. At 17-18 weeks of age they received a saline and an apomorphine injection (0.2 mg/kg SC) on 2 consecutive days in a balanced design. Behavior was recorded until 120 min after injection. RESULTS: Apomorphine increased locomotion in all pigs and reduced standing, standing alert and defecating. In addition, apomorphine induced the occurrence of some peculiar activities, rarely seen in saline-treated pigs, which seemed to represent either a transition between different postures or a conflict between hind- and forelimb activities. Apomorphine-treated LR pigs performed significantly more of these activities than HR pigs. However, snout contact with the floor, an oral stereotypy, was significantly increased in apomorphine-treated HR pigs, but not in apomorphine-treated LR pigs. CONCLUSIONS: In conclusion, the response to apomorphine of pigs relates to their behavioral response, high-resisting (HR) versus low-resisting (LR), in the backtest. The contrasts in behavioral response to apomorphine suggest a difference in the dopaminergic system between HR and LR pigs.

Effect of temperature and food intake on metabolic rate and posture of preruminant calves.

Influence of feeding level and temperature on posture and posture-related heat production was studied in preruminant calves. Twenty-four young calves were assigned in a 2 x 2 factorial design to one of two feeding levels [high (FH) or low (FL)] and to one of two temperature (7.5 degrees C or 19 degrees C). Heat production (HP) and posture were measured per calf every 9 min, during 3 days. HP was dependent on feeding level and temperature. Energy expenditure related to standing was higher at 7.5 degrees C than at 19 degrees C. Time spent standing was higher at FL than at FH, and at 7.5 degrees C than at 19 degrees C. On the contrary, the number of standing periods was lower at 7.5 degrees C than at 19 degrees C. Consequently, the duration of a standing period was higher at 7.5 degrees C than at 19 degrees C. Within a standing period, HP decreased with time. This decline was largest at 7.5 degrees C. Thus, energy cost of standing was lower in treatments with a longer duration of a standing period. These results demonstrated that the effect of temperature on energy cost of standing is influenced by the number of standing periods.

Divergent antibody responses to vaccines and divergent body weights of chicken lines selected for high and low humoral responsiveness to sheep red blood cells.

Primary and secondary antibody responses to intramuscularly administered proteins of Eschericia coli (F11), Newcastle disease virus (NCD), infectious bronchitis virus (IB), and infectious bursal disease virus (IBD), respectively, were measured at weekly intervals in two chicken lines. The latter had been divergently selected for high and low antibody responses to sheep red blood cells (SRBC), and in a random-bred control line. An oil-based adjuvant was required to induce primary and secondary antibody responses to NCD, IB, and IBD. With respect to F11, elevated antibody responses were found in birds sensitized and boosted to F11 with and without adjuvant. The humoral response to F11 and to all viral antigens was significantly higher in the high (H) line than in the low (L) line, whereas the control (C) line showed intermediate titers. At 5 and 17 weeks of age, L line birds were significantly heavier than birds of the H and the C lines. A negative phenotypic correlation within lines between body weight at 17 weeks of age and antibody titers at 1 week after sensitization was found, but no further correlations between humoral responses and body weight or growth could be established. The present results suggest that selection for enhanced humoral responsiveness to SRBC resulted in enhanced responsiveness to components of several vaccines. Mechanisms underlying the relationship between divergent selection for immune responsiveness and body weight are discussed.

Changes in energy metabolism in relation to physical activity due to fermentable carbohydrates in group-housed growing pigs.

Fermentable nonstarch polysaccharides (dietary fiber) affect energy retention in group-housed growing pigs by reducing physical activity. This study assessed the effects of fermentation and bulkiness of dietary carbohydrates on physical activity in relation to energy metabolism. Eight clusters of 14 pigs were fed one of four diets in a 2x2 factorial arrangement. Factors included 1) gastrointestinal fermentation and 2) dietary bulkiness. Contrasts in fermentation were created by exchanging gelatinized maize starch with raw potato starch on a volume basis. Bulkiness was altered by adding 15% milled wheat straw to the diets. Apart from these differences, amounts of other dietary ingredients fed to the pigs were similar. Pigs were housed in groups. Nitrogen and energy balances were measured per cluster during a 14-d period. Dietary bulkiness did not affect ME intake, heat production, or energy retention. Metabolizability decreased when maize starch was replaced with raw potato starch (P< .01), resulting in a lower energy retention on the potato starch diets (P<.01). However, the lower ME intake on the potato diets was partially compensated by a reduced energy expenditure on physical activity (P< .01), which was 17.6% lower than that of pigs fed the maize starch diets. Dietary bulkiness did not affect physical activity. The effect of fiber-rich diets (nonstarch polysaccharides) on activity in growing group-housed pigs seems to be related to fermentation in the gastrointestinal tract, and not to bulkiness (volume).

Effect of protein and protein-free energy intake on myofibrillar protein degradation in preruminant calves of 120 and 200 kilograms of live weight.

We studied the effect of protein and protein-free energy intake on the degradation rate of myofibrillar protein in preruminant calves in two experiments. Both experiments were similar in design but were performed with two live weight ranges: 80 to 160 kg (Exp. 1) and 160 to 240 kg (Exp. 2). In each experiment, calves were allocated to either an initial slaughter group or to one of 12 treatments (three calves per treatment), which consisted of six protein intake levels at each of two protein-free energy intake levels. Calves were slaughtered and analyzed for body composition when they had reached the target weight. A balance trial was performed when calves had reached 120 and 200 kg BW in Exp. 1 and 2, respectively. Myofibrillar protein degradation rate was measured by the urinary excretion of 3-methylhistidine. Correction of 3-methylhistidine excretion for myofibrillar protein mass was performed based either on the urinary creatinine excretion rate or on estimated body composition during the balance trial. In both experiments, fractional rates of myofibrillar protein degradation increased with increasing protein intake (P < .01). Fractional degradation rates increased with increasing protein-free energy intake in Exp. 1 (P < .10) and in Exp. 2 (P < .05). We conclude that the increased protein deposition rates, reported earlier, induced by nutrient intake are accompanied by increased myofibrillar protein degradation rates. Furthermore, we consider urinary creatinine excretion to be unreliable as an estimator of myofibrillar protein mass in experiments in which a large range of nutrient intakes is applied.

Thermal requirements of young calves during standing and lying.

A study of 23, 6-d-old Holstein-Friesian male calves was conducted to evaluate the thermal requirements of young calves in relation to their posture (standing or lying). Calves were housed individually and were assigned to one of four ambient temperatures: 5, 9, 13, or 18 degrees C. Heat production of each calf was measured continuously every 9 min by indirect calorimetry for 5 d. The posture during these 9-min periods was derived from the continuous measurement of physical activity. For both standing and lying, heat production was increased at 5 and 9 degrees C compared with 13 and 18 degrees C. This increase in heat production was larger during standing than during lying. Consequently, the energy cost of standing was affected by ambient temperature (173, 189, 144, and 114 kJ.kg-.75 x d-1 at 5, 9, 13, and 18 degrees C, respectively). The time spent standing was not affected by ambient temperature. The thermal requirements of the calves were dependent on the posture. Lower critical temperature was 13.5 degrees C during lying and 17.0 degrees C during standing. The rate of increase in heat production below the lower critical temperature was 7.47 kJ.kg-.75 x d-1 x Co-1 during lying and 11.24 kJ.kg-.75 x d-1 x Co-1 during standing. These results indicate that the increase in heat loss upon standing in the cold is greater than the increase in heat production upon standing at thermoneutrality. Consequently, young calves require increased cold-induced thermogenesis when they are standing.

Alteration of heat production in young calves in relation to posture.

The effects of feeding level and ambient temperature on time-related alterations of heat production in relation to physical activity (posture) were studied in young calves after transportation. Twenty-four 6-d-old Holstein-Friesian male calves were assigned in a 2 x 2 factorial design to one of two feeding levels (high or low) and one of two ambient temperatures (7.5 degrees C or 19 degrees C). Heat production was measured per calf continuously every 9 min by indirect calorimetry for a 2-wk period. Calf's posture during these 9-min periods was measured with a photoelectric cell. After arrival, heat production of calves decreased with time (days). The amount of decline in heat production depended on feeding level and ambient temperature. This decline with time was largest at the low feeding level at 19 degrees C. Six to 12 d after arrival, heat production reached steady-state levels. A steady-state level of heat production was reached first at the high feeding level at 19 degrees C. Averaged over treatments, heat production during standing was 132 kJ.kg-.75.d-1 higher than during lying. Time spent standing by calves increased over time. This indicated that alteration in time spent standing did not account for the time-related changes in heat production. On the contrary, physical activity (posture) partly masked the alterations in metabolic rate of calves after arrival. However, differences in physical activity (posture) accounted for differences in both time to reach steady-state levels and linear decline in heat production over time between treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of atrophic rhinitis induced by Pasteurella multocida toxin on heat production and activity of pigs kept under different climatic conditions.

Effects of moderate, artificially induced atrophic rhinitis symptoms on level and changes in heat production and activity were determined in pigs kept under different climatic conditions. Eight groups of 30 pigs each, housed in one of two climatically controlled respiration chambers, were exposed to a 2 x 2 factorial arrangement of treatments: challenged with 0 or 13 micrograms of Pasteurella multocida toxin (Pm-T)/mL, and two climatic environments (good: 25 degrees C, or adverse: 15 degrees C with draught periods). The Pm-T challenge reduced (P < .05) day averages of total (HP) and activity-related heat production (Har). The response to Pm-T treatment was similar in both climatic environments. Differences in the heat production and activity caused by the climatic treatment declined (P < .001) with time and acclimation to the environment. Analyses of HP, Har, and activity-free heat production in 12 2-h periods showed a biphasic activity rhythm. Both treatments affected (P < .05) level of HP and Har in several of the 2-h periods, but the biphasic rhythm was not altered. Day averages of Har showed a disposition to be differently affected (P < .068) by Pm-T challenge in the climatic treatments dependent on duration of exposure. This interaction effect (P < .001) seemed to originate from the periods between 1500 and 2100. Therefore, it might be wise to distinguish between overall effects (day means) on total, activity-related, and activity-free heat production and effects within a day (e.g., 2-h means). Treatment with Pm-T seemed to suppress the general well-being of pigs, reducing pigs' activity and food intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence of increasing thermal requirement in young, unadapted calves during 6 to 11 days of age.

Changes in thermal demand in restrictively fed, unadapted, young calves were studied during the first days after transportation. Twenty-three 6-d-old Holstein-Friesian male calves were assigned to one of four ambient temperature treatments: 5, 9, 13, or 18 degrees C. Calves were fed at a constant level below the maintenance requirement (300 kJ of ME.kg-.75.d-1). After arrival, heat production (HP) and energy and nitrogen balance were measured for each calf for 5.5 d. At ambient temperatures of 5 and 9 degrees C, HP was increased compared with temperatures of 13 and 18 degrees C (P < .001). As a consequence, energy retention was decreased at low ambient temperatures (P < .05). At temperatures of 5 and 9 degrees C, body fat mobilization was increased compared with that at temperatures of 13 and 18 degrees C (P < .001). Energy retained as protein was not affected by ambient temperature. During the experimental period, HP decreased with time. Ambient temperature affected this decrease (P < .001), indicating that the relationship between HP and ambient temperature changed with time. The rate of increase in HP below the lower critical temperature was not affected by time, averaging 9.5 kJ.kg-.75.d-1.C degrees-1. Lower critical temperature, however, increased with time by .89 C degrees/d (P < .05). The changing relation between HP and ambient temperature with time in young, unadapted calves after transportation is thus reflected in an alteration in thermal requirement with time.

Energy metabolism in relation to physical activity in growing pigs as affected by type of dietary carbohydrate.

The effect of dietary carbohydrate source on physical activity in relation to metabolic rate in pigs was studied. Six groups of 12 pigs (50-kg, castrated males) were fed one of two diets: a starch diet or a non-starch polysaccharide (NSP) diet. Both diets had a similar calculated net energy content. The starch diet contained 13% tapioca, and the NSP diet contained 17% sugar beet pulp silage. Pigs were housed in groups and fed at approximately two times maintenance (approximately 900 kJ ME.kg-.75.d-1). Nitrogen and energy balances were measured per group during a 7-d experimental period, which was preceded by a 2-wk adaptation period. Heat production and physical activity were measured during successive discrete 9-min intervals. Metabolizability of gross energy was 79.4% and 78.2% for the starch-fed and NSP-fed pigs, respectively (P < .10). Activity differed between treatments. Activity-related heat production tended to be higher for the starch-fed pigs than for those fed the NSP diet (P < .10); 118 and 90 kJ.kg-.75.d-1, respectively. During the dark phase of the day (from 2000 to 0800) activity-related heat production was 8 kJ.kg-.75.d-1 higher for the starch fed pigs than for those fed the NSP diet (P > .1) whereas during the light phase, this difference was 48 kJ.kg-.75.d-1 (P < .10). Retained energy was similar for both treatments. These results show that dietary composition can change physical activity of pigs and thereby affect their energy utilization.

Dietary betaine supplementation affects energy metabolism of pigs.

The effect of dietary betaine supplementation on energy partitioning in growing pigs under energy-restricted dietary conditions was assessed. The effect of betaine on the adaptation in energy metabolism of pigs over time after a change in diet and housing also was studied. Six groups of 14 group-housed barrows were assigned to one of two experimental diets: control or betaine-supplemented (0 or 1.29 g/kg of feed). Diets were corn- and soybean meal-based and were formulated to be limiting in energy content but sufficient in amino acids. The experiment comprised a 3-wk adaptation and a 3-wk experimental period. At the start of the experimental period, initial BW was 46 kg, each group of pigs was housed in a climate-controlled respiration chamber, and all pigs were subjected to a change in diet. During the experimental period, diets were diluted with 10% oat hulls. Pigs were fed at 2.5 times the energy requirements for maintenance, and during the experimental period, heat production, energy, and nitrogen balances were measured weekly. Metabolizibility of energy did not differ (P > 0.10) between diets. Averaged over the experimental period, betaine reduced heat production (P < 0.05) and energy requirements for maintenance (P < 0.10) and consequently increased energy retention (P < 0.10). Moreover, the difference in heat production between diets increased with time (P < 0.05). Similarly, the effect of betaine on the energy requirements for maintenance changed with time (P < 0.05). Maintenance requirements were similar in wk 1 and were decreased by betaine supplementation by 5.5% during wk 3 (477 vs. 452 kJ/[kg(0.75) x d]). Results of this study show that dietary betaine supplementation affects energy partitioning by growing pigs. However, based on the observed time-related changes in energy partitioning, it was concluded that dietary betaine supplementation did not influence adaptation by pigs to a change in housing and diet.