Effects of fermentable starch and straw-enriched housing on energy partitioning of growing pigs

Both dietary fermentable carbohydrates and the availability of straw bedding potentially affect activity patterns and energy utilisation in pigs. The present study aimed to investigate the combined effects of straw bedding and fermentable carbohydrates (native potato starch) on energy partitioning in growing pigs. In a 2 × 2 factorial arrangement, 16 groups of 12 pigs (approximately 25 kg) were assigned to either barren housing or housing on straw bedding, and to native or pregelatinised potato starch included in the diet. Pigs were fed at approximately 2.5 times maintenance. Nitrogen and energy balances were measured per group during a 7-day experimental period, which was preceded by a 30-day adaptation period. Heat production and physical activity were measured during 9-min intervals. The availability of straw bedding increased both metabolisable energy (ME) intake and total heat production (P <0.001). Housing conditions did not affect total energy retention, but pigs on straw bedding retained more energy as protein (P <0.01) and less as fat (P <0.05) than barren-housed pigs. Average daily gain (P <0.001), ME intake (P <0.001) and energy retention (P <0.01) were lower in pigs on the native potato starch diet compared to those on the pregelatinised potato starch diet. Pigs on the pregelatinised potato starch diet showed larger fluctuations in heat production and respiration quotient over the 24-h cycle than pigs on the native potato starch diet, and a higher activity-related energy expenditure. The effect of dietary starch type on activity-related heat production depended, however, on housing type (P <0.05). In barren housing, activity-related heat production was less affected by starch type (16.1% and 13.7% of total heat production on the pregelatinised and native potato starch diet, respectively) than in straw-enriched housing (21.1% and 15.0% of the total heat production on the pregelatinised and native potato starch diet, respectively). In conclusion, the present study shows that the availability both of straw bedding and of dietary starch type, fermentable or digestible, affects energy utilisation and physical activity of pigs. The effects of housing condition on protein and fat deposition suggest that environmental enrichment with long straw may result in leaner pigs. The lower energy expenditure on the physical activity of pigs on the native potato starch diet, which was the most obvious in straw-housed pigs, likely reflects a decrease in foraging behaviour related to a more gradual supply of energy from fermentation processes

Computing energy expenditure from indirect calorimetry data: a calculation exercise

Energy expenditure (Q) can be accurately derived from the volume of O2 consumed (VO2), and the volume of CO2 (VCO2) and CH4 (VCH4) produced. When the measurements are performed using a respiration chamber, VO2, VCO2 and VCH4 are calculated by the difference between the inflow (l/h) and outflow rates (l/h), plus the change in volume of gas in the chamber between successive measurements. There are many steps involved in the calculation of Q from raw data. These steps are rarely published in full detail, nor are they well documented for the training of students, researchers or technical staff. The objective of this chapter is to provide a complete calculation exercise for students at MSc level and researchers or technicians with little background in indirect calorimetry. Based on an example dataset and using a stepwise approach, the calculations used for calibrations, volumes of gas, Q, the respiratory quotient and activity related Q are explained and illustrated

Moving from a complete energy balance towards substrate oxidation: use of stable isotopes

Substrate oxidation can be estimated from gas exchange in combination with urinary nitrogen excretion measurements. The estimates are net rates of oxidation, because several metabolic processes, such as lipogenesis and gluconeogenesis, may affect the respiratory quotient, resulting in under- or overestimation of absolute rates of substrate oxidation. If these limitations, as well as accumulation of ketone bodies, lactate and urea, are taken into consideration, indirect calorimetry can be an effective method to quantify substrate oxidation in animals and humans. Methane should be excluded from the equations for calculating oxidation rates. Using 13C labelled substrates provides additional possibilities in oxidation studies. Whole body nutrient oxidation can be measured when tracer amounts of the nutrient of interest are continuously infused and when 13CO2 expiration and 13C enrichment of the precursor for oxidation are measured in blood plasma. Oxidation of exogenous substrates can be distinguished from that of endogenous substrates by using 13C enriched (or depleted) nutrients in the diet. In addition, labelling of individual monosaccharides, fatty acids or amino acids can provide insight in the metabolic fate of the tracee irrespective of availability of other substrates from the same macronutrient class (i.e. carbohydrate, fat, protein). Finally, selection of appropriate isotopomers may allow quantification of pre-identified metabolic processes (e.g. lipogenesis). Fluctuations in background enrichment, isotope administration strategy, sequestration of CO2 and isotopic gradient in the body are among the factors that should be considered when designing and interpreting oxidation studies with labelled nutrients. Modelling approaches should be in place or be developed to maximise the learnings from these studies. This appears especially challenging when animals are studied in a non-steady physiological state. In conclusion, using 13C labelling in combination with indirect calorimetry provides unique opportunities to quantify the contribution of individual substrates (endogenous as well as exogenous) to whole body energy metabolism

Moving from a complete energy balance towards substrate oxidation: use of stable isotopes

Substrate oxidation can be estimated from gas exchange in combination with urinary nitrogen excretion measurements. The estimates are net rates of oxidation, because several metabolic processes, such as lipogenesis and gluconeogenesis, may affect the respiratory quotient, resulting in under- or overestimation of absolute rates of substrate oxidation. If these limitations, as well as accumulation of ketone bodies, lactate and urea, are taken into consideration, indirect calorimetry can be an effective method to quantify substrate oxidation in animals and humans. Methane should be excluded from the equations for calculating oxidation rates. Using 13C labelled substrates provides additional possibilities in oxidation studies. Whole body nutrient oxidation can be measured when tracer amounts of the nutrient of interest are continuously infused and when 13CO2 expiration and 13C enrichment of the precursor for oxidation are measured in blood plasma. Oxidation of exogenous substrates can be distinguished from that of endogenous substrates by using 13C enriched (or depleted) nutrients in the diet. In addition, labelling of individual monosaccharides, fatty acids or amino acids can provide insight in the metabolic fate of the tracee irrespective of availability of other substrates from the same macronutrient class (i.e. carbohydrate, fat, protein). Finally, selection of appropriate isotopomers may allow quantification of pre-identified metabolic processes (e.g. lipogenesis). Fluctuations in background enrichment, isotope administration strategy, sequestration of CO2 and isotopic gradient in the body are among the factors that should be considered when designing and interpreting oxidation studies with labelled nutrients. Modelling approaches should be in place or be developed to maximise the learnings from these studies. This appears especially challenging when animals are studied in a non-steady physiological state. In conclusion, using 13C labelling in combination with indirect calorimetry provides unique opportunities to quantify the contribution of individual substrates (endogenous as well as exogenous) to whole body energy metabolism

Asynchronous Supply of Indispensable Amino Acids Reduces Protein Deposition in Milk-Fed Calves

A balanced supply of indispensable amino acids (AA) is required for efficient protein synthesis. Different absorption kinetics (e.g., free vs. protein-bound AA) may, however, create asynchrony in postabsorptive availability of individual AA, thereby reducing the efficiency of protein deposition. We studied the effects of AA asynchrony on protein metabolism in growing, milk-fed calves. In 2 experiments, each with a change-over design including 8 calves, a milk replacer deficient in Lys and Thr was used. In Expt. 1, l-Lys and l-Thr were parenterally supplemented, either in synchrony (SYN), asynchrony (ASYN), or partial asynchrony (PART) with dietary AA. In Expt. 2, l-Lys and l-Thr were orally supplemented, either in SYN or ASYN with dietary AA. In Expt. 1, digested protein was used less efficiently for growth for ASYN (31.0%) than for SYN (37.7%), with PART being intermediate (36.0%). Indicator AA oxidation tended (P = 0.06) to be higher for ASYN. In Expt. 2, the efficiency of protein utilization was lower for ASYN (34.9%) than for SYN (46.6%). Calves spared AA from oxidation when the limiting AA were provided in excess after a short period

Body Fat Deposition Does Not Originate from Carbohydrates in Milk-Fed Calves

Milk-fed heavy calves utilize dietary protein with a low efficiency and often develop hyperglycemia and insulin resistance. Distributing the daily nutrient intake over an increasing number of meals increases protein deposition and improves glucose homeostasis. Therefore, we examined effects of feeding frequency (FF) and feeding level (FL) on the diurnal pattern of substrate oxidation and on the fate of dietary carbohydrates in milk-fed heavy calves. Eighteen milk-fed calves weighing 136 ± 3 kg were assigned to FF (1, 2, or 4 meals daily) at each of 2 FL (1.5 or 2.5 times maintenance), except for calves at FF1 (only at a low FL). Urea, leucine, and glucose kinetics were assessed for each treatment by use of [13C]urea, [1-13C]leucine, [U-13C], and [2-13C]glucose, respectively. FF altered the diurnal pattern, but not the total, of urea production production. Although urea production correlated well with nitrogen retention, oxidation of oral L-[1-13C]leucine did not. Dietary glucose was almost completely oxidized (80% based on [13C]glucose and 94% from indirect calorimetry measurements) regardless of FL. Fatty acid synthesis from glucose appeared to be negligible based on similar recoveries of 13CO2 from orally supplied [U-13C]glucose and [2-13C]glucose. The increased fat deposition at the higher FL originated almost exclusively from greater transfer of fatty acids to body lipid stores. These findings contrast with both glucose and lipid metabolism in growing pigs and indicate that alternative adaptive mechanisms operate in heavy milk-fed calves

Design of climate respiration chambers, adjustable to the metabolic mass of subjects

Open-circuit respiration chambers can be used to measure gas exchange and to calculate heat production (Q) of humans and animals. When studying short-term changes in Q, the size of the respiration chamber in relation to the subject of study is a point of concern. The washout time of a chamber, defined as the proportion of the chamber size to the rate of ventilation, needs to be minimised for accurate measurement of short term changes in Q. To date, most respiration chambers have a fixed size, limiting their use for different species, sizes and number of subjects, thus hampering studying the short term dynamics of Q. This chapter presents various approaches to the design, construction and testing of respiration chambers, adjustable to the metabolic mass inside. As investment costs for constructing respiration chambers are high, flexibility in the use of chambers can contribute substantially to an efficient use of resources. Furthermore, an outline is given to sensor criteria and calibration and finally, the validation of a whole indirect-calorimetric system is described. Air leak tolerance is defined and attention is paid to caretaking of animals, excreta collection and animal and personnel welfare and safety. Respiration facilities, recently constructed at Wageningen University are presented as an example. Briefly, four 45 m2 climate chambers can be used, e.g. for heat or cold stress experiments, to incubate eggs or as a hygiene barrier. Within each chamber, one or two smaller airtight, size adaptable respiration rooms, can be built in where ambient temperature, humidity and ventilation rate can be controlled independently. In each respiration room a wide range of ventilation flow rates can be accomplished and both hypobaric and hyperbaric air pressure control can be established, allowing energy metabolism experiments with specific pathogen free animals (hyperbaric) or trials with infectious agents (hypobaric)