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Two experiments with sows were performed to investigate the effect of isoenergetic replacement of starch by fish oil or olive oil on concentrations of lipids in plasma and lipoproteins. The first experiment was based on a cross-over design with three periods, each lasting 16 days. Each sow was fed during one of the periods a basal ration with isoenergetic addition of (1) starch (495 g/d), (2) olive oil (221 g/d), or (3) fish oil (223 g/d) based on energetic requirement for maintainance. The second experiment was based on a cross-over design with eight periods, each lasting 16 days. In the first and in the last periods, each sow was fed the basal ration. In the other six periods, each sow was fed the basal ration with addition of two different amounts of (1) starch (284/568 g/d), (2) olive oil (140/281 g/d), or (3) fish oil (141/282 g/d). The two different amounts of addition were selected to exceed the energetic requirement for maintainance by 25% or 50%. In both experiments blood samples were taken before each change of the ration. In both experiments olive oil elevated the concentration of cholesterol in plasma in comparison with starch. This elevation was due to a large elevation in high-density lipoproteins (HDL), and a slight elevation in low-density lipoproteins (LDL) and very-low density lipoproteins (VLDL). The ratio between HDL and LDL cholesterol was increased by feeding olive oil. The effect of olive oil on concentrations of cholesterol in plasma and lipoproteins was dose-dependent. In both experiments none of the two dietary oils significantly changed concentrations of triglycerides in plasma and lipoproteins. Concentrations of phospholipids in plasma, HDL, and LDL were elevated by olive oil. In both experiments addition of fish oil elevated concentration of cholesterol in plasma due to elevated cholesterol concentration in LDL. Concentration of HDL cholesterol was not changed by fish oil. Thus, the ratio between HDL cholesterol and LDL cholesterol was lowered by fish oil. The effect of fish oil on concentration of cholesterol in plasma and lipoproteins was also dose-dependent. Fish oil had no significant effect on phospholipid concentrations in plasma and lipoproteins. In conclusion, in the present experiment olive oil caused antiatherogenic changes of the lipoprotein profile, whereas fish oil caused proatherogenic changes of the lipoprotein profile.

An animal model experiment was conducted with nine adult sows to study the effects of long-chain fatty acids on thermogenesis when different fatty acids were replaced for 30% of the energy of a basal diet based on cereals and soybean meal. The acids were fed as commercial products containing as main constituent either palmitic acid, oleic acid, or linoleic acid, according to a latin square design in experimental periods 2 to 4. In periods 1 and 5 the sows were submitted to basal diet alone. Digestibility of palmitic acid was only 36%, whereas the unsaturated fatty acids were highly absorbed (90%). Interaction effects of the undigested proportion of the long-chain fatty acids with the basal diet in hindgut fermentation could be ruled out since a supplementary experiment on three sows showed no influence of infusion of oleic or linoleic acid into the caecum on the energy utilization of the basal diet. There was no significant differences in thermogenesis among the fatty acids. Heat production in the treatment periods averaged -1.2% as compared to the basal diet periods. This result was in accordance with the value -1.0% calculated theoretically for the reduction in heat production in the treatment periods. Thus, the data did not indicate any stimulating effect of long-chain fatty acids on heat production, and utilization of energy of fatty acids occurred within the obligatory thermogenesis.

In a model experiment eight adult sows were used to examine the effect of successive periods of under- and oversupply of energy (MUMU) on thermogenesis and efficiency of energy utilization in comparison to a constant maintenance supply (NNNN). Each treatment sequence was assigned to each animal according to a change-over design over 8 weeks. Before and after the treatment periods all the animals were fed at maintenance level (N). Energy deficiency (M) was performed by use of a basal diet with 45% of maintenance energy requirements and values for all the other nutrients sufficient for requirements. Normal (N) and excessive (U) intakes of energy was provided with supplements of starch. The total inake of gross energy during the periods MUMU was exactly the same as during NNNN. Complete energy balances were performed for each animal and period as well as during the pre- and post-experimental phase. There was no or little response of altered energy intake on carbon and energy excretion in faeces, urine and methane. However, heat production was significantly decreased by 4.1% on energy deficiency, and increased by 15.1% during energy oversupply. Summed up over the total sequence the animals produced 5.4% more heat on MUMU than during NNNN. This response was associated with a mobilization of 1.1 MJ/d tissue energy and a decrease in body weight by 2.0 kg. The efficiency of utilization of ME was 88% with energy undersupply and 75% during overnutrition. Criteria of energy balance did not differ between the pre- and post-treatment periods. It could be demonstrated that the increase in energy expenditure at oversupply was entirely explainable by the so-called obligatory thermogenesis. At the energy deficiency periods the efficiency of energy utilization reflected both energy costs of ingestion and processing of nutrients as well as a slight reduction in metabolic rate. Finally, there were no residual effects of the treatment on the energy expenditure of the animals at the end of the experiment.

A respiration calorimetry experiment with 10 matures sows was conducted to study the effect of a ketogenic diet on heat production and energy utilization. The ketogenic diet contained no carbohydrates and 85% of its energy as fat. The control diet was a mixed diet with most of its energy as carbohydrates. Both diets provided the same daily protein intake, which was slightly below the calculated protein requirement. The level of energy intake was adjusted to a moderate positive energy balance. Both diets were allocated to the same animal for three weeks each according to a crossover design. Seven-day collection periods and 48-hours measurements of the gaseous exchange (carbon-nitrogen balance method) were conducted on individual sows per diet. The ketogenic diet substantially increased the energy losses in faeces, which resulted in a energy digestibility of 75% compared to 93% with the mixed diet. The methane production was also significantly depressed. In contrast, the urine energy excretion was not influenced by the extremely high fat diet. The nitrogen balance showed lower faecal nitrogen losses and a higher urine nitrogen excretion in the animals with the high fat diet. Because of this compensative response no difference in nitrogen retention was observed between the two dietary treatments. The ketogenic diet caused no detrimental effects on thermogenesis or energy utilization. The results of both criteria could be fully explained by the well accepted ideas of the efficiency of utilization of the energy from fat under balanced nutrition conditions. Overall the results demonstrate that a high fat diet has no regulatory effect on the usually diet-induced thermogenesis.

The effect of a carbohydrate-free protein-fat (PF) diet compared with a mixed diet (CPF diet) on the energy metabolism was studied in a changeover trial with mature sows. The PF diet contained two thirds of its metabolizable energy as protein and one third as fat; in the CPF diet the relationship was 3.5 carbohydrate: 1 protein: 0.2 fat. Under the conditions of undernutrition and neutral temperature nitrogen, carbon and energy balance were assessed as parameters according to the procedures of indirect calorimetry in four 24-hour measurements each for the gaseous exchange of the animals. At isocaloric supply of metabolizable energy, no differences were found in the N, C and energy retention. The mean heat production amounted to 23.6 MJ/day in both dietary groups. Also, no dietary influence could be observed with regards to the daily time pattern of heat production nor to the physical activity of the animals. Computation of the nutrient utilization on the basis of potential ATP formation resulted in a turnover of 304 mol ATP/day for the mixed diet and in 275 mol ATP for the carbohydrate-free diet. The discrepancy is discussed. Overall, the results show that an increased heat production, providing the possibility of an augmented loss of body energy, could not be induced by the carbohydrate-free protein-fat diet in the course of undernutrition.

In a respiration trial with 12 nongravid, nonlactating sows, the effect of supplying energy at greatly discrepant levels for 2 days (18, 45, 4.5 and 4.5 g feed/kg 0.75 per meal) on parameters of energy metabolism was studied in comparison with a consistent feed intake (18 g feed/kg 0.75 per meal). The trial was conducted as a change-over design (AB - BA) and included a total of 24 balance periods. The isoenergetic nutrition was aimed at the maintenance energy level. Digestion coefficients for dry matter, nitrogen, carbon and energy were not affected by the inconsistent distribution of the feed supply. Similarly, all parameters of energy metabolism in the sum of the 2-day periods were not different between the two treatments. The maintenance energy exchange averaged 49.1 MJ/2 . days when the energy supply was inconsistent and 48.4 MJ/2 . days in the control group. In the course of the 48-hour measurements, heat production during inconsistent energy supply was higher by 1.8 MJ on the 1st day and 1.2 MJ lower on the 2nd day than in the control group. The additional energy of 17 MJ (75%) supplied in treatment B on the 1st day above that in the control did not seem to have been stored by fat synthesis within this time.

A respiration trial with 12 adult sows was conducted as a balanced incomplete block design to study the effect of Palatinit on energy and nitrogen balance. The treatments were the basal diet fed at maintenance level alone or with the addition of sucrose and Palatinit, respectively. The apparent digestibility of the energy of Palatinit was 91.0%, whereas sucrose was completely digested. The fecal excretion of nitrogen after feeding of Palatinit increased about 50% as compared to the group's basal diet and basal diet plus sucrose. The urine energy excretion and the methane losses amounted to 1% of the ingested energy of Palatinit. The efficiency of utilization of metabolizable energy was 68.9% for Palatinit and 75.3% for sucrose. Altogether, the results show that 62% of the Palatinit energy and 74.5% of the sucrose energy were retained as body energy.