Downloaded from British Journril of' Nutrition (1993), 69, 333-343 333 https://www.cambridge.org/core The respiratory quotient in relation to fat deposition in fattening-growing pigs BY KIRSTEN JAKOBSEN* AND GRETE THORBEKt Nationul Institute of Animal Science, Department of Animal Physiology and Biochemistry, Foulum, PO Box 39, DK-8830 Tjele, Denmark . IP address: (Received 21 February 1991 - Accepted 8 May 1992) 170.106.202.58 The relationship between non-protein respiratory quotient (RQ,,,) and total fat retention (RFAT) or fat retained from synthesized carbohydrates (RFAT(CH0)) was evaluated from experiments with fattening-growing pigs in the live weight (LW) range from 45 to 120 kg. A commercial feed compound , on (31 g fat/kg) was fed at low (LI) or high (HI) feed intake in Expt 1, while a semi-purified diet (9.5 g 29 Sep 2021 at 08:16:21 fat/kg) was given without (LO) or with (HO) supplement of 90 g soya-bean oil/kg in Expt 2. RQ,, was calculated from 24 h measurements of the gas exchange, RFAT from 7 d N and C balances and RFAT(CH0) from differences between RFAT and digested fat. The measurements showed that about 85 % of the total gas exchange was caused by oxidation of non-protein nutrients and the RQ,, varied from 1.00 to 1.34. In Expt 1 RFAT increased with LW from 46 to 141 and from 199 to 335 g/d on LI and HI respectively, whilst in Expt 2 RFAT increased from 191 to 377 and from 267 to 511 g/d on LO , subject to the Cambridge Core terms of use, available at and HO respectively. A pronounced Linearity was found between RQ,, and RFAT for all diets, but the curve for Expt 2 on HO had a lower position than the common curve for the other diets. By relating RQ,, to RFAT(CH0) a common linear curve and regression equation could be established in spite of the great variation in dietary composition, intake of fat and fat deposition. 24 h gas exchange: Respiratory quotient: Fat retention: Lipogenesis: Pigs In recent papers the theoretical basis of indirect calorimetry in research with humans in health and disease has been discussed (Elia & Livesey, 1988; Ferrannini, 1988; Livesey & Elia, 1988). By indirect calorimetry the heat production (HE) can be calculated either by the respiratory quotient (RQ) method (HE, RQ) or by the C-N-balance method (HE, CN). Both methods are reliable and can be carried out with high accuracy, as discussed by Christensen et a/. (1988). The RQ method is based on measurements of 0, consumption, CO, and CH, production https://www.cambridge.org/core/terms and the amount of N excreted in the urine. The HE from oxidation of non-protein materials (glucose and triacylglycerol) is based on their respective RQ values ( co2/Po,) and the heat released during complete oxidation. The validity of indirect calorimetry when RQ is above 1.0, associated with lipogenesis, has been demonstrated by Elia & Livesey (1988). In humans RQ values above 1.0 have been obtained during infusion of glucose (Askanazi et a/. 1980) and intake of high-carbohydrate meals (Acheson et a/. 1984). In animals RQ values above 1.0 were measured in dogs by overfeeding with glucose over a 4 h period (Lusk, 1928) and in geese by overfeeding with carbohydrates (Benedict & Lee, 1937). In growing-fattening pigs on high feed intake RQ values, measured in 24 h periods, were constantly above 1.0 (Thorbek et al. 1984; Christensen, 1985). https://doi.org/10.1079/BJN19930037 HE, CN is calculated as the difference between metabolizable energy (ME) and energy retained in fat +protein (RE), measured by C-N balances. In measuring the C-N balances * Previously Kirsten Christensen. 7 Present address: Hegnskrogen 12, DK-2800 Lyngby, Denmark. 13 NUT 69 Downloaded from 334 K. JAKOBSEN AND G. THORBEK the amount of total fat retention can be calculated directly (Christensen et al. 1988), while https://www.cambridge.org/core fat retention by the RQ method is calculated indirectly as the difference between retained energy (determined as RE = ME-HE, RQ) and energy retained in protein. Both methods are used in our laboratory. We observed that the non-protein RQ (RQ,,) was linearly related to the amount of fat retention measured by the C-N balances, but also that a high intake of fat depressed the RQ values in spite of a high fat retention. As the fat intake is high in human diets compared with conventional swine diets, we thought that our observations on pigs receiving different amounts of dietary fat might contribute to further discussion about the relationship between RQ,, and fat retention caused by directly . IP address: deposited dietary fat and fat synthesized from carbohydrates. The results from measurements of 24 h gas exchange in fattening-growing pigs in relation to fat deposition will be presented in the present paper. 170.106.202.58 MATERIALS AND METHODS Animals and diets , on The findings examined were taken from publications concerning measurements of energy 29 Sep 2021 at 08:16:21 metabolism by indirect calorimetry in growing pigs (Thorbek et al. 1984; Christensen, 1985). The material included twenty-two castrated male Danish Landrace pigs in the growing-fattening period from 45 to 120 kg live weight (LW) in which the RQ values were above 1.0. A commercial pelleted feed compound was fed at low (LI) and high (HI) feed intake to fourteen pigs in Expt 1 (Thorbek et al. 1984), while a semi-purified basal diet was given to , subject to the Cambridge Core terms of use, available at eight pigs in Expt 2 (Christensen, 1985). In this experiment four pigs received a basal diet (LO) and four were given a supplement of 90 g soya-bean oil/kg (HO). The components applied in the different diets are shown in Table 1 together with the mean values for the chemical composition determined for eight samples from each diet during the two experiments. Minerals and vitamins were included according to Danish standards. The fat content was 31 g fat/kg in the commercial diet (Expt l), while it was 9.5 and 99-5 g fat/kg in Expt 2 on LO and HO respectively. The total duration of Expts 1 and 2 was 110 and 56 d respectively. Experimental procedure Digestibility, C-N balances and gas exchange were measured individually in four LW ranges from 50 to 120 kg in Expt 1 and from 45 to 95 kg in Expt 2. All measurements were carried out with a 7 d preliminary period with the pigs in individual pens followed by a 7 d period of collection in metabolism crates, including a 24 h measurement of gas exchange https://www.cambridge.org/core/terms in the middle of the period. An open-air-circuit respiration unit with two chambers (Thorbek, 1969) was used for determination of 0, consumption and CO, production. The temperature in the pens, as in the respiration unit, was kept at 18". All pigs were fed twice daily and received water ad lib. The pigs in Expt 1 were kept in their pens and fed on the commercial diet on high feed intake until they reached the LW range planned for the balance experiments. Each pig was assessed on LI and HI, and no pigs were assessed in more than two consecutive LW ranges. The distribution of pigs in the different groups is demonstrated in Table 2. A total of fifty balance periods was planned, but four periods were omitted for the reasons indicated. A . total of thirty-two balance periods was planned in Expt 2, but only twenty-nine were https://doi.org/10.1079/BJN19930037 completed due to the death of one pig on treatment HO. The fat analyses in feed and faeces were carried out with HC1-hydrolysis before diethyl ether extraction in accordance with the Stoldt (1952) method. C in feed, faeces and urine Downloaded from RESPIRATORY QUOTIENT AND FAT DEPOSITION 335 https://www.cambridge.org/core Table 1. Expts 1 and 2. Composition of experimental diets (glkg) Expt 1 Expt 2 (Basal diet)* Components Components Barley I10 Maize starch 292 Oats 50 Cassava meal 185 Soya-bean meal 140 Glucose 65 Meat-and-bone meal 20 Sucrose 65 Mineral and vitamin mix 20 Cellulose 33 . IP address: Analysis Skim-milk powder 160 Dry matter 892 Soya-bean meal 80 Crude protein (N x 6.25) 165 Casein 80 Crude fat 31 Mineral and vitamin mix 40 170.106.202.58 NFE 621 Analysis Gross energy (MJ/kg) 16.5 Dry matter 900 Crude protein 183 Crude fat 9.5 , on NFE 614 Gross energy (MJ/kg) 15.8 29 Sep 2021 at 08:16:21 NFE, N-free extracts. * Basal diet (LO) and diet supplemented with 90 g soya-bean oil/kg (HO). Table 2. Distribution of animals on balance experiments in diflerent live-weight (Lw) ranges on low (LI)and high (HI)feed intake , subject to the Cambridge Core terms of use, available at LW range (kg) .._ 5G60 6WO 8G100 lOG120 Feed intake ... LI HI LI HI LI HI LI HI Animal no. 1,4,6,7 x x* xx 13, 14, 15, 16 xx xt x 21,23, 24 xx 25, 21, 28 xx Xt x* * Pigs nos. 1 and 28 omitted; feed residuals. t Pigs nos. 15 and 28 omitted; technical errors. was measured by means of a Carmograph (Wosthoff, Bochum, Germany), working with high precision on the electric conductivity principle (Neergaard et al. 1969). The standard https://www.cambridge.org/core/terms procedure for balance experiments at this Institute, as described by Thorbek (1975) and Christensen (1985), was followed.