Myofibre composition in longissimus dorsi (LD) muscle of Erhualian (EHL) and Large White (LW) pigs was investigated by determining the ratios of mRNA abundances of four myosin heavy chain (MyHC) isoforms (MyHC I, MyHC 2a, MyHC 2x and MyHC 2b) using multiplex RT-PCR. The relationship between expression of growth hormone receptor (GHR) and peroxisome proliferator-activated receptor α coactivator-lα (PGC-lα) mRNAs and changes ofmyofibre type composition during postnatal growth from 3 to 180 days of age were analysed. At 3 days of age, proportions of MyHC I, 2a and 2x fibres were high while only a few MyHC 2b fibres were differentiated. Dramatic changes were observed from day 3 to day 20 with significantly decreased MyHC I, 2a and 2x fibres but abrupt increases in MyHC 2b fibres in both breeds of pigs. Breed difference was exhibited only from day 90, with higher MyHC 2b but less MyHC I and 2a expression in LW pigs. Developmental pattern of GHR mRNA expression in LD muscle coincided with that of MyHC 2b, with LW pigs expressing higher abundance of GHR mRNA. PGC-lα mRNA expression followed distinct patterns in the two breeds of pigs, a higher level of PGC-lα mRNA being expressed in LD muscle of EHL pigs, the breed that possessed more oxidative fibres (MyHC I and MyHC 2a).

The stomach and small intestine manifest a myoelectric activity pattern called the migrating myoelectric complex (MMC), which is controlled by both environmental and intrinsic factors. The daily MMC pattern has been little investigated, therefore the purpose of the present study was to study it, in weaned pigs given food twice a day. A wireless telemetric recording system was used for 24-h electromyography of the antrum and duodenum. The activity of the antrum showed little change if any, whereas the myoelectric activity of the duodenum significantly changed with respect to the time of day and feeding in conscious pigs. Namely, there were more frequent and regular MMC cycles occurring in the duodenum at night as compared with that during daytime. This change was due to the shortening of phase II of the MMC cycles that were registered at night. Phase I of the MMC showed transient variability in relation to feeding with no impact on the day/night differences. Phase III of the duodenal MMC cycle as well as the ‘feeding pattern’ did not change along with the time of day and feeding regime. In conclusion, daily variation in the duodenum may provide different conditions for digestive processes in the day and night.

Data from the F2 generation of a Large White (LW) ✕ Meishan (MS) crossbred population were analysed to detect quantitative trait loci (QTL) for leg and gait scores, osteochondrosis and physis scores. Legs, feet and gait score were assessed in 308 F2 animals at 85 ( + 5) kg and osteochondrosis and physis scores were recorded for the right foreleg after slaughter. A genome scan was performed using 111 genetic markers chosen to span the genome that were genotyped on the F2 animals and their F1 parents and purebred grandparents. A QTL on chromosome 1 affecting gait score was significant at the genome-wide significance level. Additional QTL significant at the chromosome-wide 5% threshold level (approx. equivalent to the genome-wide suggestive level) were detected on chromosome 1 for front feet and back legs scores, on chromosome 13 for front legs and front feet scores, on chromosome 14 for front legs, front feet and back legs scores and on chromosome 15 for back feet score. None of the QTL for osteochondrosis score exceeded the chromosome-wide suggestive level, but one chromosome-wide QTL for physis score was found on chromosome 7. On chromosome 1, gait and front feet scores mapped to the middle of the chromosome and showed additive effects in favour of the LW alleles and no dominance effects. The QTL for back legs score mapped to the distal end of the chromosome and showed a dominant effect and no additive effect. On chromosomes 14 and 15, the LW allele was again superior to the MS allele. On chromosome 13, there were both additive and dominance effects in favour of the MS allele. The MS alleles on chromosome 13 may have potential for introgression into a commercial LW population. The other putative QTLs identified may have value in marker-assisted selection in LW or MS-synthetic populations.

The objective of this study was to assess the effect of feeding steam flaked wheat and maize in diets with high and low levels of dairy products and to examine the effect of sequence of feeding the processed cereals in diets for newly weaned pigs. In experiment 1, 96 pigs were weaned at 27 days of age, blocked on sex and weight and assigned as individually penned pigs to four dietary treatments as follows: (a) high dairy product diet (6 kg of starter diet containing 230 g/kg milk powder followed by a link diet containing 125 g/kg milk powder to 26 days) with uncooked cereal (HDP), (b) high dairy product diet with steam flaked cereal (HDPC), (c) low dairy product diet (6 kg of starter diet containing 125 g/kg milk powder followed by a link diet containing no milk powder to 26 days) with uncooked cereal (LDP) and (d) low dairy product diet with steam flaked cereal (LDPC). In experiment 2, 96 pigs were weaned at 19 to 24 days of age, blocked on sex and weight and assigned as individually penned pigs to four dietary treatments containing: (a) uncooked cereal for 26 days, (b) uncooked cereal for 14 days followed by cooked cereal to 26 days post weaning, (c) cooked cereal for 26 days and (d) cooked cereal for 14 days followed by uncooked cereal to 26 days post weaning. Steaming and flaking of wheat and maize did not significantly affect pig performance during the experimental period or at any subsequent period up to slaughter. Daily gain from day 0 to 26 post weaning was 415 and 453 g/day (s.e.13•5; P < 0•05) for low and high dairy product diets, respectively. Food conversion efficiency (FCE) from day 0 to 14 post weaning on the low and high dairy product diets was 1•86 and 1•33 g/g (s.e. 0•14; P < 0•05), respectively. Pigs given the high dairy product diets during the experimental post-weaning period reached final carcass weight 5 days earlier than pigs given the low dairy product post-weaning diets (P < 0•05). In experiment 2, treatment did not affect food intake (mean = 450 s.e. 13•2 g; P > 0•05), daily gain (mean = 382 s.e. 12•5 g; P > 0•05) or FCE (mean = 1•19 s.e. 0•02 g/g; P > 0•05). In conclusion, feeding steamed flaked wheat and maize in post-weaning diets failed to improve pig performance irrespective of dairy product or sequence of feeding cooked cereals.

The effect of partial replacement of poly- (PUFA) with monounsaturated (MUFA) fatty acids in pig diets on fatty acid composition of subcutaneous and intramuscular fat and on fat and lean firmness was studied. No effect of dietary fat was observed on total saturated fatty acid concentration in any of the backfat layers or intramuscular lipid fractions. No significant effect of dietary fat was observed for the MUFA concentration in the outer layer, but a marked effect was evident for the inner layer (P < 0·001). A linear effect of dietary MUFA was observed for MUFA (P < 0·001) and PUFA (P < 0·001) in polar lipids. No significant effect of dietary treatment was observed on total concentration of n-3 fatty acids in any lipid location but a marked effect was observed for total n-6 fatty acid concentration. The response of pig fatty acid n-6 concentration was different depending on the lipid location. The neutral lipid fraction showed significantly lower n-6/n-3 fatty acid ratio than the subcutaneous fat. Intramuscular polar lipids showed no significant response of n-6/n-3 ratio. A linear effect of dietary MUFA concentration was observed on the melting point on the inner backfat layer (MP = 34·4 (s.e. 2·51) + 0·15 (s.e. 0·07) ✕ dietary MUFA (g/kg dry matter) (R2 = 0·24, P < 0·05)), indicating that the partial substitution of dietary PUFA by MUFA produced a fat of higher consistency. No response of the melting point of the outer layer to dietary treatment was observed. A marked effect of dietary fat was shown for backfat hardness (P < 0·001), gumminess (P < 0·001) and chewiness (P < 0·001). No effect of dietary fat was observed on the rheological properties of longissimus lumborum muscle.

Seventy-two entire male pigs (initially 28 kg body weight) were used to study the effects of by-product (pollard, rapeseed meal, peas and copra meal combined) inclusion level with or without expander processing, on growth performance and nutrient digestibility in a 3 ✕ 2 factorial arrangement of treatments. Productive performance and nutrient digestibility coefficients (no. = 6) were determined in individually fed pigs offered pelleted diets ad libitum containing a low by-product diet (350 g/kg), medium by-product diet (520 g/kg) and high by-product diet (752 g/ kg). The expanded diets were processed at 105ºC for 5 s at 35 bar pressure having been previously conditioned at 85ºC for 5 s. All diets were formulated using standard values for ingredients to have similar concentrations of digestible energy (DE) and ideal protein. Starch contents of 437, 401 and 314 g/kg and crude fibre contents of 48, 58 and 74 g/kg were recorded for the low, medium and high by-product diets respectively. No by-product level ✕ expander processing interactions (P > 0·05) were observed in growth criteria, carcass characteristics or nutrient digestibility. Expander processing decreased (P < 0·05) the apparent organic matter (OM), ash and energy digestibility of the diets, as well as the digestible energy content of the diets. The level of by-product in the diet had no statistically significant effect on the OM, protein and energy digestibility or the DE content of the diets. The increase in by-product inclusion levels decreased (P < 0·05) average daily gain (ADG) (0·899 v. 0·888 v. 0·854 (s.e. 0·014) kg/day) from 28 kg to slaughter and food intake (1·62 v 1·48 v 1·48 (s.e. 0·028) kg/day) in the 28 to 55 kg weight range. Expander processing had no effect on ADG, food intake or food conversion ratio. The increase in byproduct level decreased (P < 0·01) killing-out proportion (723 v 705 v 710 (s.e. 3·94) g/kg) and carcass ADG (0·684 v 0·651 v. 0·635 (s.e. 0·012) kg/day) (P < 0·05). Expander processing decreased (P < 0·05) killing out proportion (707 v. 718 (s.e. 3·22) g/kg). In conclusion, increasing the by-product content of the diet decreased ADG while expander processing had no effect on growth performance.

The objective of this study was to test that genetic variation for resistance to clinical and subclinical diseases exists in growing pigs. A total of 13 551 male growing pigs were assessed for resistance to five categories of clinical and subclinical disease: (i) any clinical or subclinical disease, (ii) lameness, (iii) respiratory diseases, (iv) diarrhoea, and (v) other diseases (i.e. any clinical or subclinical disease with the exception of (ii), (iii), and (iv)). Additive genetic variation for resistance to each disease category was estimated by fitting a Weibull, sire-dam frailty model to time until the pigs were first diagnosed with a disease from that category. Genetic correlations among the resistances to each disease category were approximated as product-moment correlations among predicted breeding values of the sires. Additive genetic variation was detected for resistance to (i) any clinical or subclinical disease (additive genetic variance for log-frailty (± s.e.) = 0·18 ± 0·05, heritability on the logarithmic-time scale = 0·10), (ii) lameness (0·29 ± 0·11, 0·16), (iii) respiratory diseases (0·24 ± 0·16, 0·12), (iv) diarrhoea (0·30 ± 0·27, 0·16), and (v) the other diseases (0·34 ± 0·15, 0·19) and there were generally positive and low-to-moderate correlations among the predicted breeding values (-0·03 to + 0·65). These results demonstrate that additive genetic variation for resistance to clinical and subclinical diseases does exist in growing pigs, and suggests that selective breeding for resistance could be successful.

An experiment was conducted to measure the effects of stocking density (increased number of pigs per pen) on lysine requirements of pigs grown from 25 to 60 kg live weight. Two hundred and sixty-four female Large White ✕ Landrace pigs were assigned at 25 kg to one of four dietary lysine treatments (13·3 (L1); 11·4 (L2); 9·5 (L3) and 7·6 (L4) g/kg) and either seven or 13 pigs per pen (or 1 0 and 0·5 m2 per pig, respectively). An additional treatment of one pig per pen (20 m2 per pig) was included to compare the responses of solitary- versus group-penned pigs. Animals were given ad libitum access to dietary treatments from a mean pen starting weight of 261 (s.e. 0·35) kg to a mean pen finishing weight of 63·4 (s.e. 0·61) kg live weight. There were no significant interactions between dietary lysine content and floor space per pig on food intake (FI), average daily growth rate (ADG), the amount of food per unit of gain (FCR) and the rate of protein retention (PR). Significant interactions were evident for body composition and the rate of lipid retention (LR). Over the weight range 25 to 40 kg there were significant differences in FI (P < 0·05) and FCR (P < 0·001) between dietary lysine treatments but most of these differences had disappeared over the 40 to 60 kg live weight. Individually penned animals had significantly higher (P < 0·05) FI and ADG than group-penned animals. However, there were no differences between seven and 13 pig per pen treatments. Stocking density had no effect on LR or body protein content but did cause a significant reduction in PR (P < 0·001) and an increase in body lipid content (P < 0·05) as the number of pigs per pen increased from seven to 13. Lysine requirements (expressed in g/day) therefore could be seen to be reduced with increasing stocking density. However, as lysine intake was reduced in group-penned animals, the reduced daily requirement does not necessarily warrant a reduction in the lysine content of the food. Feeding according to the requirements for maximum PR will still produce the best carcass and growth performance irrespective of the group size. The improvement in PR associated with higher dietary nutrient levels did not completely offset the adverse physiological effects of higher stocking density but may partly counteract the effect of reduced lysine intake. However, there were indications that feeding crowded pigs a lower dietary lysine concentration may not further reduce the already diminished protein (lysine) growth rate. An additional experiment was performed to test whether the number of feeder bins may have constrained food intake and therefore growth in group-penned animals. The results of this experiment showed that the number of bins had no significant effect on FI, ADG and FCR in group-penned pigs, and therefore a single feeder bin was not considered a constraining factor in pigs housed with limited floor space.

A comparison of in vitro microbial activity was made between inocula from faeces of adult and unweaned pigs, using a range of carbohydrate-rich substrates. The substrates tested were classified into groups (fibre-rich, grains, gums, pectin, saccharides, storage carbohydrates, and miscellaneous). Proximate and fibre analyses were determined for all substrates tested. Fermentation kinetics were measured according to the cumulative gas production technique. End-point products such as gas, volatile fatty acids and ammonia were also determined. The faeces from the adult pigs (ATF) were collected from four castrated finisher pigs (Dutch Landrace × Great Yorkshire). These were offered a diet based on highly digestible maize starch and fish meal, so as to be as free as possible of fermentable carbohydrates. The unweaned piglet faeces were collected from 19 unweaned piglets (male and female) which were 27 to 30 days old. The parameters were tested for significance by an analysis of variance using the Tukey's studentized range test of multiple comparisons. There were significant differences in the fermentation patterns both due to source of substrate and inoculum. It would appear that the metabolic activity of the microflora does differ significantly between adult and weanling pigs, though this varied for the different carbohydrates tested. Suggestions are made as to how to select potential carbohydrate ingredients for an in vivo experiment, based on their in vitro fermentation characteristics.

Food intake in pigs is highly variable across different production circumstances. This report concludes from a critical review of published observations that it was unrealistic to expect from the scientific literature purporting to express nutrient requirement any reasonable prediction of the particular food intake of groups of pigs. None the less, such knowledge is essential for the practical purposes of their day-to-day nutrition. The literature does however yield general principles from which may be derived: (a) the likely forms (but not the parameter values) of intake functions relating food intake to pig live weight; and (b) the likely factors involved in the modulation of food intake at any given live weight. Using these principles two methods for determining on-farm food intake from the use of simple and available records were proposed. The first requires knowledge only of start and final weight, the time elapsed, and total food intake: it involves two steps, the determination of a suitable growth curve followed by the fitting of a suitable food intake curve. The second method is appropriate in the absence of information on total food intake, and requires a minimum number of spot measurements through the growth period. Different functions were tested for the curve of best fit. As a further benefit it appeared that models could be constructed from the information presented that would speculate for diagnostic purposes upon the likely modulators of food intake. Such models could explore the constraints of gut capacity, the energetic requirements of maintenance and potential growth, the influence of excessive or inadequate environmental temperature, the quality of housing and stocking density.

This study investigated the effect of chromium picolinate supplementation on growth performance, carcass characteristics and lipid metabolism of growing-finishing pigs. Sixty Landrace ✕ Yorkshire ✕ Duroc (LYD) pigs with a mean initial body weight of 46·65 (s.e. 6·72) kg were randomly allocated into three groups with two replicates. They were supplemented with 0 , 200, or 400 μg/kg (ppb) chromium in the organic form of chromium picolinate for 90 days. Supplementation with chromium picolinate in the pigs’ ration improved their growth performance, enhanced average daily gain (P < 0·05), and increased their food consumption, especially in the 200 ppb group ( P > 0·05). Chromium picolinate supplementation also improved carcass characteristics, as the average back fat thickness was reduced and the loin-eye area was enhanced ( P < 0·05). The serum chromium concentration in the chromium picolinate supplemented groups was approximately twice that of the controls ( P < 0·05). Supplementation with chromium also markedly reduced serum total cholesterol, triacylglycerol (TG) and urea concentrations in the pig serum ( P < 0·05). Serum insulin was significantly decreased in the 400 ppb group, while serum glucose was decreased in the 200 ppb group ( P < 0·05). Very low density lipoprotein (VLDL) was reduced and low density lipoprotein (LDL) was increased in the chromium supplementation group. Meanwhile, the high density lipoprotein-cholesterol and VLDL-cholesterol were markedly increased, while LDL-cholesterol was significantly diminished ( P < 0·05) in the 200 ppb group. The adipocyte diameter and volume in the chromium-supplemented groups tended to be larger than in the control ( P = 0·07). In vitro studies indicated that incorporation of [u, 14C]glucose into total lipids (P < 0·05) was increased by chromium supplementation. However, there were no lipolysis differences among the groups (P > 0·05). The carcasses of the pigs that received the chromium supplemented ration contained less oleic acid (C18 : 1) and total unsaturated fatty acids (P < 0·05). On the other hand, the total saturated fatty acid content was higher than that of the controls (P < 0·05). Results in this study demonstrate that chromium picolinate supplementation in pigs has several beneficial effects.

The effect of a period of feeding on a high bulk food, upon the subsequent intake of foods of differing bulk content, was investigated in two experiments of the same design. The intention was to provide a severe test of the two current conceptual frameworks available for the prediction and understanding of food intake. In each experiment 40 male Manor Meishan pigs were randomly allocated to one of four treatment groups at weaning. Each experiment was split into two periods, P1 (12 to 18 kg) and P2 (18 to 32 kg). The treatments, all with ad libitum feeding, were: a control food (C) given throughout (treatment CC); a medium bulk food (M) given throughout (treatment MM); a high bulk food (H) given in P1 and then C in P2 (treatment HC); H given in P1 and M in P2 (treatment HM). C was based on micronized wheat with 13·4 MJ digestible energy and 243 g crude protein per kg fresh food. In experiment 1 M contained 350 g/kg and H 560 g/kg of unmolassed sugar-beet pulp and in experiment 2 M contained 500 g/kg and H 700 g/kg of unmolassed sugar-beet pulp. Framework 1 predicted that food intake on the medium bulk food (M) would not be increased, whereas framework 2 predicted that intake on M would be increased after a period of feeding on H, compared with when M was offered continuously.

In P1, both food intake (P < 0·01) and growth (P < 0·001) were severely limited on H compared with C. In experiment 1 growth was limited on M compared with C during the first 7 days of P1 (P < 0·01) only. In experiment 2 intake (P < 0·001) and growth (P < 0·001) on M were limited throughout P1, compared with C but not thereafter. Therefore, in neither experiment did M cause a lower growth rate than C from 18 to 32 kg. In experiment 1 there was full adaptation to M after about 10 days from 12 kg. In experiment 2 adaptation was complete by the end of the first 7 days from 18 kg.

In P2, food intake (P < 0·001) and live-weight gain (P < 0·05 and P < 0·001 in experiments 1 and 2, respectively) were increased on HC compared with CC. By the last 7 days of P2 intake was still higher (P < 0·01) but growth rate was no longer different to CC. Intake and gain were increased in P2 on HM compared with MM but, in general, these differences were small and not significant. In the first 7 days of P2, in experiment 1 pigs on HM had higher intakes (P < 0·001) and gains (P < 0·05) than those on MM, but in experiment 2 only intake was higher (P < 0·01) with no difference in gain. By the last 7 days of P2 there was no difference in either intake or gain between these two groups in either experiment. Pigs on HC increased intake by more than those on HM. There was, therefore, a significant interaction for food intake (P < 0·05, in experiment 1 and P < 0·001, in experiment 2) between prior and present food.

The unexpected failure of either M food to limit growth throughout the experimental period meant that the results of these experiments could not be used as a strong test to reject either one of the frameworks. However, the ability of the pigs to compensate on M was less than that on C. The data provide some evidence that under conditions of compensation foods such as M may be limiting. This is in closer agreement with the framework that predicted that consumption of a limiting food will not increase after a period of feeding on a high bulk food (framework 1).

When compared with other menadione derivatives such as menadione sodium bisulphite (MSB), menadione nicotinamide bisulphite (MNB), an organic salt combining menadione and nicotinamide, shows better stability towards physical and chemical factors once it is added to pre-mixes or foods. The present work evaluates the bioavailability of the two vitamins present in this compound and toxicity in the pig. To assess vitamin bioavailability, pigs were given small amounts of food containing MNB or equivalent amounts of MSB and nicotinamide in the free form. Menadione and nicotinamide concentrations in blood samples drawn at set times after the diets were given did not reveal any significant differences between the two modes of administration. Haematic levels of both vitamins in animals receiving MNB, or MSB and nicotinamide, were after 2, 4, 8 and 12 h higher (P < 0·001) than those of untreated animals. The tolerance level to MNB was evaluated in pigs given diets containing graded amounts of MNB (100, 500, 2500 mg/kg) for 28 days. No significant (P > 0·05) differences were recorded in live weight, food intake and gain/food ratio in pigs given these diets when compared with those given an unsupplemented diet. Haemoglobin and bilirubin levels did not differ between animals given various amounts of MNB and control animals. Plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities in pigs given 100 mg/kg of MNB did not show significant differences when compared with those observed in pigs given an unsupplemented control diet. In pigs on the diets supplemented with 500 and 2500 mg/kg of MNB there was a significant increase in the two enzymatic activities as compared with controls (P < 0·001 and P < 0·01). In the case of ALT this had disappeared by 28 weeks. MNB is a good source of vitamin K for the pig and does not appear to have any adverse effects, even when administered at levels higher than those normally used in pig food supplementation.

Pigs with inbreeding coefficients, ranging from 0·125 to 0·375 were analysed for effect of inbreeding on daily carcass gain, body length and meat proportion in the carcass. The foundation animals were back crosses of a Landrace boar of his daughters which were Yorkshire Landrace hybrids. The statistical model included effect of sex and slaughter weight in addition to the effect of inbreeding. A statistically significant effect of inbreeding on daily carcass gain was found with a linear decline of 1·6 g for 0·1 increase in inbreeding coefficient. There was no effect of inbreeding on body length and meat proportion. Carcass weight had a highly significant effect on body length and daily carcass gain. Effect of sex was statistically significant for meat proportion only.