J. Noblet

Effect of dietary fibre on the energy value of feeds for pigs

Abstract Dietary fibre (DF) is an inevitable component of organic matter in pig feeds since it is present in most ingredients and to a high extent in by-products (wheat bran or corn gluten feed, for instance) or forages which are more commonly used. In growing pigs, digestibility coefficients of DF average 0.40–0.50 but they range from around zero in high lignin and water-insoluble DF sources (e.g. wheat straw) to 0.80–0.90 in fibre sources with high pectin or water-soluble DF levels (e.g. sugar beet pulp or soybean hulls). This also means that components of DF are digested differently by pigs: lignin is undigested while pectins are almost totally digested; hemicellulose tends to be more digested than cellulose, although both are partly digested. However, even if it is partly digested, DF provides negligible amounts of digestible or metabolisable energy to the growing pig due to increased endogenous protein and fat losses and negative interactions between DF and other dietary components. Digestive utilisation of DF improves with body weight of the pig with the highest values obtained in adult sows. However, this improvement is dependent on the botanical origin of DF. Consequently, DF makes a positive contribution to energy supply in adult sows and it is therefore recommended to give at least two energy values for pig feeds: one for growing pigs and one for adult sows. Digestion of DF is also associated with energy losses as methane. The efficiency of utilisation of metabolisable energy for net energy is poorer when it originates from DF (0.50–0.60 versus 0.80 for starch). Finally, the actual contribution of dietary fibre to energy balance of the pig can be affected by climatic conditions (heat increment of DF is used for thermoregulation) or changes in behaviour of pigs (lower physical activity with higher DF supply).

Voluntary feed intake and feeding behaviour of group-housed growing pigs are affected by ambient temperature and body weight.

Abstract The effect of ambient temperature on individual feeding behaviour was studied in six groups of Pietrain×Large White barrows. In experiment 1 (two groups), ambient temperature varied in a cyclic way from 22 to 12°C and 12 to 22°C with three or four consecutive days at each of the following temperatures: 22, 19, 16, 14 or 12°C. Similarly, in experiment 2 (two groups), temperature varied from 19 to 29°C and 29 to 19°C with three or four consecutive days at 19, 22, 25, 27 or 29°C. In both experiments, each group was used over two successive cycles with an initial body weight (BW) of 37 kg at cycle 1 (four pigs per group) and 63 kg at cycle 2 (three pigs per group). During experiment 3, groups of four pigs were exposed to varying temperatures over one cycle either as in experiment 1 (one group) or as in experiment 2 (one group); their initial BW was 45 kg. Photoperiod was fixed to 12 h of light. In experiments 1 and 2, neither the daily number of meals (11) nor the rate of feed intake (37 g/min) were affected by temperature. The daily number of meals was lower at cycle 2 (9 vs. 12 at cycle 1 on average) but their size was higher (305 vs. 181 g/meal at cycle 1). The feeding pattern was mainly diurnal (62%). From individual data obtained at each temperature level and each stage of growth in this study ( N =296), an equation to predict the voluntary feed intake (VFI) from temperature ( T , ranging between 12 and 29°C) and body weight (BW, ranging between 30 and 90 kg) is proposed: VFI (g/d)=−1264+117 T −2.40 T 2 +73.6BW−0.26BW 2 −0.95 T ×BW (RSD=329). The present relationship indicates that VFI depends on temperature and body weight with a marked negative effect of high ambient temperatures in heavier pigs.

The effect of energy and protein intake of sows on their longevity: a review☆

Abstract The characterization of the effects of protein and energy intake of sows on their longevity requires long-term experiments involving large numbers of females. Results from the studies available show that sows are culled mainly for reasons involving reproductive failure, locomotion problems or poor lactation performance. Energy under-feeding during gestation is associated with lower body fat reserves at farrowing or at weaning and generally return to oestrus is delayed and conception rate is lower. On the contrary, over-feeding during gestation increases weight and condition of the sow at the end of pregnancy and this can affect the occurrence of farrowing and lactation problems and culling for poor lactation performance or locomotion problems. During lactation, it seems that there are critical levels for energy and for protein below which weaning to oestrus interval, rate of return to oestrus and pregnancy rate are affected, especially in primiparous sows. This is the main reason for early culling of sows. The mechanisms are not yet elucidated, but the metabolic status or the status of body reserves of the sows at weaning seem to be involved. It is thus necessary to apply a feeding strategy adapted to each sow, in relation to its own level of production, its behaviour and the housing conditions, in order to maintain body reserves within an optimal zone all along the reproductive life and to maximize its longevity.

Influence of dietary fibre on digestive utilization and rate of passage in growing pigs, finishing pigs and adult sows

Four experimental diets differing in the level and the origin of dietary fibre (DF) were studied : a control, low DF diet (diet C, 100 g total dietary fibre (TDF) per kg dry matter (DM)) and three fibre-rich diets (200 g TDF per kg DM) which corresponded to a combination of diet C and maize bran (diet MB), or wheat bran (diet WB), or sugarbeet pulp (diet SBP). During two successive experimental periods, each diet was offered to five pigs at a growing stage (35 kg body weight (BW)) and at a finishing stage (75 kg BW). In addition, four adult ovariectomized sows received successively one of the four diets according to a 4 ✕ 4 Latin-square design. Digestive utilization of energy and nutrients of diets and rate of passage parameters were determined using a pulse dose of ytterbium oxide followed by total faecal collection. Faecal marker excretion was quantified using an age-dependent, onecompartment model, from which the mean retention time in the gastro-intestinal tract of pigs (MRT) was obtained. The digestibility of dietary energy and nutrients, especially the DF fraction, increased with the increase in BW from growing to finishing pigs ( P < 0·01) and was still higher in adult sows; the difference between pig stages was more pronounced for diet MB. At each stage, the digestibility of energy or nutrients was lower ( P < 0·01) for diets MB or WB than for diet SBP. Accordingly, the energy and DF digestibility of sugar-beet pulp was higher and increased much less with BW. The MRT was shorter for diets MB and WB in growing pigs and in sows. Sows had a longer MRT (81 h) than finishing pigs (37 h) and growing pigs (33 h); however, MRT was highly variable between sows. It is concluded that the degree to which different types of DF are digested depends, in part, on the botanical origin, and it may be improved by a longer MRT in the gastro-intestinal tract of pigs. Some fibrous foodstuffs (such as maize-by products) will benefit more from a longer MRT than others.

Performance and utilization of dietary energy and amino acids in piglets fed low protein diets

A total of 32 Pietrain×(Landrace×Large White) barrows were used to test the effect of reducing the dietary crude protein (CP) level on performance and composition of gain in piglets from 12 to 27 kg. Four diets based on corn, wheat, barley and soybean meal providing 1.01 g of ileal digestible lysine per MJ of NE (net energy) were prepared. Diet 1 was formulated without free amino acids (AA), while in diets 2–4, CP level was progressively reduced and free AA were supplemented according to the ideal protein concept. The CP levels were 224, 204, 184, 169 g/kg for diets 1, 2, 3 and 4, respectively. Piglets were housed individually and had free access to feed and water. The feed intake was measured daily. At the end of the experiment, animals were slaughtered and body composition was measured. The 12 control piglets were slaughtered at the beginning of the experiment and the composition of gain (water, ash, protein lipid, AA and energy) was calculated according to the comparative slaughter technique. Feed intake was the lowest (P<0.05) with diet 1 (959 g/day) and similar for diets 2–4 (1049 g/day, on average). Nevertheless, average daily gain of the animals did not differ between treatments (666 g/day, on average). Reducing CP level resulted in a numerically reduced water consumption and urine production, but no effect on the occurrence of diarrhea was observed. The N excretion over the total experiment was reduced by 42% from diet 1 to diet 4. At identical ME (metabolizable energy) intakes (2.52 MJ/day per kg BW0.60), protein and lipid composition of gain (18.9 and 13.0 g/day per kg BW0.60, on average) were not affected by the diet. Energy gain (0.94 MJ/day per kg BW0.60) and heat production (1.58 MJ/day per kg BW0.60) were also not different between treatments. The amino acid pattern of deposited protein was not affected by dietary CP level, except that histidine deposition was significantly smaller with diets 3 and 4. These results indicate that a reduction of dietary CP level by up to 55 g/kg in association with adequate AA supplementation does not affect the level of performance and body composition of piglets and contributes to lower N excretion.

Digestion of plant cell walls from four different sources in growing pigs

Abstract Large White pigs of about 40 kg were grown on six diets (4 pigs per diet) that contained 40% wheat and soya bean protein as protein source. In the control diet (W) the only added carbohydrate source was starch; in the five other diets this was partly replaced by 22% wheat bran (WB), 44% wheat bran (2WB), 16% sugar beet pulp (SBP), 19% soya bean hulls (SBH) or 22% wheat straw (WS). The animals were given similar amounts of digestible energy. The apparent digestibility (AD) of dry matter (DM), nitrogen (N), energy (E), neutral detergent fibre (NDF), acid detergent fibre (ADF) and non-starch polysaccharides (NSP) of the diets was determined. Whatever the fibre source added to the diets, the AD of N and E was significantly reduced relative to the control diet. In diets with similar NSP contents (2WB, SBP, SBH, WS diets), the AD of E was higher in SBP and SBH diets (0.841 and 0.834 for E, respectively) and lower in the WS diet (0.736). No significant change in AD of N (0.810 on average) was observed. The AD of NDF varied with that of total NSP (WS

Effect of energy intake on the performance of different types of pig from 45 to 100 kg body weight. 1. Protein and lipid deposition

Between 45 and 100 kg body weight, Large White castrated males (cLW), and crossbred Pietrain × Large White castrated males fcPP×) and boars (bPP×) were either given food ad libitum in experiment 1 or allocated to four energy levels (0·70, 0·80, 0·90, 1·00 ad libitum) in experiment 2. Daily protein and amino acid supplies were calculated to be non-limiting for growth. Protein (PD) and lipid (LD) deposition rates were measured according to the comparative slaughter technique over the whole experimental period (experiments 1 and 2) and according to the nitrogen and energy balance technique at four stages of growth: 48, 64, 79 and 94 kg mean body weight (experiment 2). Average daily gain increased linearly with metabolizable energy (ME) intake, the slope of the relationship being significantly different between types of pig (from −28 to +36 g per additional MJ ME). Daily PD increased with ME intake above maintenance (MEp) according to a linear-plateau relationship in the three types of pig: the slope was significantly affected by type of pig (from +3·4 to 6·0 g per extra MJ MEp) but not by stage of growth. Daily LD increased linearly with MEp intake; neither the type of pig nor the stage of growth affected its slope (+13-5 g per extra MJ MEp). The LD/PD ratio in the extra body-weight gain associated with increased energy intake was affected only by the type of pig.

Comparative digestibility of energy and nutrients in growing pigs fed ad libitum and adults sows fed at maintenance

Abstract Fourteen diets which differed widely in their chemical composition were fed to adult sows at a maintenance energy level (390 KJ ME/kg BW 0.75 ) and to 43 kg BW growing pigs at a feeding level close to their ad lib. intake (1930 KJ ME/kg BW 0.60 ). These two groups of animals and the corresponding nutritional conditions represent two extreme situations in which digestibility of nutrients should be maximum and minimum, respectively. The results showed that the sows had superior capacity to digest energy or nutrients. The digestibility coefficients of energy, crude protein, ether extract and NDF were 84.7, 85.2, 69.1 and 70.9% for sows and 75.8, 74.8, 55.5 and 50.2% for growing pigs, respectively. On the other hand, the ME: DE ratio was lower in sows (92.4 vs. 96.5%) in connection with higher energy losses in the urine (6.4 vs. 3.1 % of DE intake) and as methane (1.34 vs. 0.44% of DE intake). The difference in DE values (on average, 1.6 MJ per kg dry matter) or ME values (on average, 0.9 MJ per kg dry matter) between sows and growing pigs was not constant but increased with dietary NDF content. The greater depressive effect of NDF on energy digestibility in growing pigs was related to their lower ability to digest cell wall fractions and to the more negative effect of NDF on apparent digestibility of other dietary nutrients (crude protein and crude fat). Equations for predicting nutritive values of sow diets from those measured in growing pigs are given.

Energy utilization in pigs selected for high and low residual feed intake.

Genetic selection on residual feed intake (RFI) can be used as an alternative method to G:F to improve feed efficiency in pigs. The objective of this study was to determine the effects of selection for RFI on digestive and metabolic utilization of energy in 2 lines of purebred French Large White castrated male pigs obtained from a divergent selection experiment over 6 generations. The RFI(+) (high RFI) line consumed more feed than predicted from performance compared with the RFI(-) (low RFI) line. Digestibility of energy and nutrients, total heat production (HP), HP related to physical activity, and energy and N balance were measured in respiration chambers for a 6-d period in pigs offered feed ad libitum. Pigs remained in the chamber for an additional day and did not receive any feed to estimate the fasting HP and calculate the thermic effect of feeding. Five pairs of 2 littermates from the same farrowing batch were used in each line. Because 2 respiration chambers were available for the trial, pigs were measured regularly during the 25- to 95-kg growing period. Two pigs per chamber were used until pigs reached 45 kg of BW, and 1 pig per chamber was used thereafter. Individual feed intake and BW gain were measured continuously from weaning to the end of the trial. Pigs were fed 3 diets with decreasing CP contents during the 25 to 45 (period 1), 45 to 65 (period 2), and 65 to 95 (period 3) kg of BW periods. Average daily feed intake was greater in RFI(+) pigs than in RFI(-) pigs between 25 and 65 kg of BW (2,128 vs. 1,891 g/d; P < 0.01) and G:F was 8% greater in RFI(-) pigs compared with RFI(+) pigs (P < 0.01). There was no line effect on digestibility coefficients or N retention, irrespective of the experimental period studied. Nitrogen retention was 31.2, 28.7, and 20.8 g/d at periods 1, 2, and 3, respectively (P < 0.001). The HP was greater in RFI(+) pigs than in RFI(-) pigs (1,497 vs. 1,383 kJ.kg of BW(-0.60).d(-1); P < 0.01), with no subsequent line effect on energy retention. The activity-related HP tended to be greater in RFI(+) pigs than in RFI(-) pigs (250 vs. 218 kJ.kg of BW(-0.60).d(-1); P = 0.09), and the fasting HP was 10% greater (P = 0.04) in RFI(+) pigs than in RFI(-) pigs (846 vs. 771 kJ.kg of BW(-0.60).d(-1)). The thermic effect of feeding, expressed as a percentage of ME intake, was the same for both lines of pigs (average, 14.7%). In conclusion, the RFI(+) pigs are energetically less efficient because of their greater HP related to physical activity and basal metabolic rate.

Digesta transit in different segments of the gastrointestinal tract of pigs as affected by insoluble fibre supplied by wheat bran

Digestibility is the result of two competing processes: digestion and digesta transit. To develop or parameterise mechanistic models of digestion, both processes have to be quantified. The aim of this study was to determine the effect of insoluble dietary fibre on the transit in the gastrointestinal tract of pigs. Six barrows (33 kg initial body weight and fitted with two simple T-cannulas at the proximal duodenum and distal ileum) were used in a double 3 x 3 Latin square design. Pigs were offered diets differing in total dietary fibre content (170, 220 and 270 g/kg DM) at 4 h intervals. A single meal marked with YbO2 and Cr-EDTA was used to determine the kinetics of markers concentrations of the solid and liquid phases, respectively. The mean retention time (MRT), calculated by the method of the moments, averaged 1, 4 and 38 h in the stomach, small intestine and large intestine, respectively. Increasing the insoluble fibre content in the diet had no effect on MRT in the stomach and decreased the MRT of both phases in the small intestine (P < 0.05). In the large intestine, increasing the insoluble fibre content decreased the MRT of the liquid phase (P = 0.02) and tended to decrease the MRT of the solid phase (P = 0.06). Transit of the solid phase in the large intestine was 4-8 h slower than transit of the liquid phase. Analysis of marker excretion curves indicated that the small and large intestine should be represented mathematically to have both a tubular (propulsion) and compartmental (mixing) structure.