Performance and individual feed intake characteristics of group-housed sows fed a nonstarch polysaccharides diet ad libitum during gestation over three parities

Review: Targeted nutrition in gestating sows: opportunities to enhance sow performance and piglet vitality

Birth weight is a key factor for piglet survival, and therefore, there is ongoing interest in how nutrition during gestation can influence birth weight. Interestingly, sows are generally fed one single diet throughout gestation. This paper reviews past attempts to increase foetal growth to term and discusses opportunities to target nutritional manipulations at specific windows of gestation where key developmental events occur. Birth weight limits chances to survive mainly in piglets with birth weight below 1 kg. These piglets represent around 16% of the population. Given the normal distribution of birth weight, the mean birth weight needs to be increased by at least 50-100 g to have a meaningful impact on this proportion of the population and on perinatal survival. Based on existing variation in reported mean birth weight across a number of studies, it is argued that it is unrealistic to expect an increase in mean birth weight of more than 100 g. Attempts in the past to increase birth weight have focussed on the last trimester of gestation, when foetal growth is accelerated. Increase in feed allowance or nutritional concepts that target placenta vascularisation have not been successful. It is argued that nutritional manipulations should rather focus on the middle of gestation, since in that period, placenta growth occurs and since placenta size limits the foetal size. Alternatively, nutritional manipulations can target placentation during the embryonic phase.

Evaluation of multienzyme supplementation and fiber levels on nutrient and energy digestibility of diets fed to gestating sows and growing pigs

The objective was to investigate the effect of a multienzyme blend (MEblend) and inclusion level on apparent total tract digestibility (ATTD) of energy and nutrients, as well as ileal digestibility of crude protein (CP) and amino acids (AA) in gestation diets with low (LF) or high-dietary fiber (HF) fed to gestation sows. For comparison, growing pigs were fed the same HF diets to directly compare ATTD values with the gestating sows. In experiment 1, 45 gestating sows (parity 0 to 5; 187 ± 28 kg bodyweight; BW) were blocked by parity in a 2 × 3 factorial arrangement and fed 2.2 kg/d of the HF (17.5% neutral detergent fiber; NDF) or LF (13% NDF) diet and one of three levels of MEblend (0.0%, 0.08%, and 0.1%) to determine impacts of MEblend on ATTD. Twenty-seven growing pigs (initial 35.7 ± 3.32 kg BW) were fed the same HF diet (5% of BW) and one of three MEblend inclusions. The MEblend at both 0.08% and 0.1% increased ATTD of energy, NDF, and acid detergent fiber (ADF) (P < 0.05) in gestating sows but ATTD of total non-starch polysaccharides (NSP) and its residues were not affected. Sows fed HF, regardless of MEblend, had greater ATTD of NDF, xylose, and total NSP (P < 0.05) in comparison to grower pigs. In experiment 2, ileal cannulas were placed in 12 gestating sows (parity 0 to 2; BW 159 ± 12 kg) to determine apparent and standardized ileal digestibility (AID and SID) of AA and NSP. In a crossover design, sows were fed the same six diets, as in experiment 1, and a nitrogen-free diet during five periods of seven days each to achieve eight replicates per diet. There was no interaction between diet fiber level and MEblend inclusion. Supplementation of MEblend to gestating sow diets did not impact SID of CP and AA regardless of dietary fiber level. The SID of His, Ile, Lys, Phe, Thr, Trp, and Val were 3% to 6% lower (P < 0.09) in HF than LF independent of MEblend. Supplementation of MEblend did not impact AID of NSP components, but sows fed HF had higher AID of arabinose (LF: 26.5% vs. HF: 40.6%), xylose (LF: 3.5% vs. HF: 40.9%), and total NSP (LF: 25.9% vs. HF: 40.0%) compared to sows fed LF (P < 0.05). Dietary supplementation of MEblend increased ATTD of nutrients, NSP, and energy in diets fed to gestating sows regardless of inclusion level, with MEblend having a greater incremental increase in diets with lower NDF levels. Inclusion of MEblend impacted neither SID of AA nor AID of NSP in low- or high-fiber gestation diets, but high-fiber diet, negatively affected SID of AA.

Dietary fiber in a low-protein diet during gestation affects nitrogen excretion in primiparous gilts, with possible influences from the gut microbiota

We investigated the effects of dietary fiber (DF) supplementation in normal or low crude protein (CP) diets on reproductive performance and nitrogen (N) utilization in primiparous gilts. In total, 77 Landrace × Yorkshire pregnant gilts were randomly allocated to four dietary treatments in a 2 × 2 factorial design. The groups comprised 1) equal intake of normal CP (12.82% and 0.61% total lysine), 2) low CP (LP) (10.53% and 0.61% total lysine), and 3) with or 4) without DF supplementation (cellulose, inulin, and pectin in a 34:10:1 ratio). A low-protein diet during gestation significantly reduced daily weight gain from days 91 to 110 of pregnancy (-162.5 g/d, P = 0.004). From N balance trials conducted at days 35 to 38, 65 to 68, and 95 to 98 of pregnancy, DF addition increased fecal N excretion at days 65 to 68 (+24.1%) and 95 to 98 (+13.8%) of pregnancy (P < 0.05) but reduced urinary N excretion (P < 0.05), resulting in greater N retention at each gestational stage. DF increased fecal microbial protein levels and excretion during gestation. An LP diet also reduced urinary N excretion at different gestational stages. An in vitro fermentation trial on culture media with nonprotein N urea and ammonium bicarbonate (NH4HCO3) as the only N sources revealed that microbiota derived from feces of gestating gilts fed the high DF diet exhibited a greater capacity to convert nonprotein N to microbial protein. Microbial fecal diversity, as measured by 16S rRNA sequencing, revealed significant changes from DF but not CP diets. Gilts fed an LP diet had a higher number of stillbirths (+0.83 per litter, P = 0.046) and a lower piglet birth weight (1.52 vs. 1.37 kg, P = 0.006), regardless of DF levels. Collectively, DF supplementation to gestation diets shifted N excretion from urine to feces in the form of microbial protein, suggesting that the microbiota had a putative role in controlling N utilization from DF. Additionally, a low-protein diet during gestation negatively affected the litter performance of gilts.

The Effect of Increasing Neutral Detergent Fiber Level through Different Fiber Feed Ingredients throughout the Gestation of Sows

Simple Summary

To reduce feed costs, the exploration of feed resources is currently the main research direction. In the past, fiber feed was generally regarded as anti-nutritional factors. Recently, fiber has received special attention due to its many beneficial effects. Therefore, this study selected five common household and production wastes as fiber sources and added them to the diet of pregnant sows to explore the impact on sows and piglets. The results of this study indicated that adding corn gluten feed (CG) significantly improved the digestibility of sows and body weight (BW) of piglets, which provide evidence and insight for the application of corn gluten feed in gestation sow diets.

Abstract

The purpose of this study was to determine the effect of increasing dietary neutral detergent fiber (NDF) levels on pregnant sows, and to select the best feed ingredients based on reproductive performance, plasma biochemistry parameters, colostrum and milk composition, and nutrient digestibility. Seventy-two multiparous sows were randomly allotted to six dietary treatment groups (n = 12). The feeding of chicory meal (CM), wheat bran (WB), corn gluten, and rice bran meal (RBM) increased the average weaning weight of piglets compared with the control (CON) group (p < 0.05). Supplementation with CG diet increased the sow BW, weight gain, and back fat thickness compared with WB and RBM on day 107 of gestation (p < 0.05). Furthermore, Supplementation with CG diet resulted in lower plasma urea nitrogen (PUN) and higher total protein (TP) concentrations in plasma (p < 0.05). Feeding CM diet and soybean curd residue (SCR) diet reduced the total protein and globulin, and supplementation with CM diet significantly increased the PUN (p < 0.05). The apparent total tract digestibility (ATTD) of crude protein (CP), crude fat (EE), calcium (Ca), phosphorus (P), neutral detergent fiber (NDF), and acid detergent fiber (ADF) were decreased following the addition of CM, WB, or SCR to the diets (p < 0.05). The ATTD of NDF and ADF were significantly increased in the CG group (p < 0.05). In conclusion, the feeding of CG diet to sows have an excellent effect.

Effects of dietary isomaltooligosaccharide and Bacillus spp. supplementation during perinatal period on lactational performance, blood metabolites, and milk composition of sows

BACKGROUND

In this study, we evaluated the effects of isomaltooligosaccharide (IMO) and Bacillus spp. in perinatal diets on lactational performance, blood metabolites, and milk composition of sows. Multiparous gestating sows (N = 130) with similar body conditions were fed diets without containing IMO (control, CON group), IMO (IMO group), IMO and Bacillus subtilis (IMO + S group), IMO and Bacillus licheniformis (IMO + L group), and IMO and both B. subtilis and B. licheniformis (IMO + S + L group).

RESULTS

The average daily feed intake of lactating sows in the IMO + S group (P < 0.05) and the average litter gain and total milk yield in the IMO + S + L group (P < 0.01) were significantly higher than those of the sows in the other treatment groups. In addition, the serum alanine aminotransferase and alkaline phosphatase concentrations in all treatment groups were lower than those in the CON group (P < 0.05). Furthermore, the highest proportion of fat in colostrum (0.05 < P < 0.1) and lowest proportion of lactose in milk were observed in the IMO + L group (P < 0.05). The concentrations of growth hormone and immunoglobulins A and G in milk were higher in sows supplemented with IMO, IMO + S, IMO + L, or IMO + S + L (P < 0.05).

CONCLUSION

IMO and Bacillus spp. supplementation during the perinatal period improved the sows' lactational performance by affecting their metabolism and milk quality. Sows in the IMO + S and IMO + S + L treatment groups exhibited the best performance. © 2019 Society of Chemical Industry.

Body condition, live weight and success in agonistic encounters in mixed parity groups of sows during gestation

Group housing of gestating sows benefits their welfare by allowing them freedom of movement and the opportunity for social interaction. However, social life could also bring disadvantages for individuals who receive direct aggression or are displaced from the feeder. The aim of this study was to investigate associations between social behaviour, body condition and live weight. Gestating sows (n=298) were investigated on a commercial farm. Sows were housed in mixed parity groups where two single space, ad libitum trough feeders served 12 animals. Sows were weighed, body condition scored and had their back fat layer measured at mixing, 4 weeks after insemination and again before farrowing. Social status was estimated based on the numbers of won and lost agonistic interactions at mixing and at the end of gestation. In addition, tear staining was scored before the farrowing and reproductive performance data were collected. With the aid of video recordings, 100 to 150 interactions per group were observed. Winning percentage at mixing and at the end of gestation were associated (P&lt;0.05) and appeared relatively stable within individuals. Tear staining scores and litter sizes were not associated with winning percentage at the end of gestation. However, live weight, relative weight, body condition and back fat thickness were associated with winning percentage (P&lt;0.05), giving heavier animals an advantage. Low winning percentage related to lower live weight gain, probably due to poorer success in competition for feed. Live weight within a mixed parity group could be used as a proxy measure for social status. Sows with low body condition score and submissive sows might need special attention with regard to group dynamics and housing to alleviate the effects of competition in group housing.

Effects of different levels of feed intake during four short periods of gestation and housing systems on sows and litter performance

The current study investigated the effects of different levels of feed intake during 4 short periods of gestation and of housing systems on sow and litter performance. A total of 255 multiparous sows were allotted to 1-4 dietary treatments using a randomized complete block design blocking by initial body weight (BW), backfat (BF) and parity. Sows were housed either in individual stalls (n=129) or group pens (n=126) with 55 sows in each pen with electronic sow feeder during gestation. All sows were fed one common corn-soybean meal-based diet with the amount of 1.0×maintenance energy level of feed intake (106×BW^0.75) throughout gestation except 4 periods of 7 d when dietary treatments were imposed on day 27, 55, 83 and 97 of gestation. During the 4 periods, sows were fed 1 of 4 different levels of feed intake: 0.5, 1.0, 1.5 and 2.0×maintenance energy level (0.5M, 1.0M, 1.5M and 2.0M, respectively). Results showed that both BW gain and BF change during gestation for sows on 1.5M (49.7kg and 3.1mm, respectively) and 2.0M (52.5kg and 3.7mm, respectively) levels of feed intake were significantly (P<0.01) greater than sows on 0.5M (26.1kg and -0.1mm, respectively) and 1.0M (35.6kg and 0.1, respectively) levels of feed intake. In contrast, lactation weight gain for sows on 1.5M (3.3kg) and 2.0M (3.4kg) levels of feed intake during 4 short periods of gestation were significantly (P<0.01) less than sows on 0.5M (18.4kg) and 1.0M (11.4kg) levels of feed intake during 4 short periods of gestation, whereas BF loss during lactation for sows on 1.5M (-3.6mm) level of feed intake during 4 short periods of gestation were significantly (P=0.03) higher than sows on 1.0M (-2.1mm) level of feed intake during 4 short periods of gestation. Additionally, average daily feed intake during lactation for sows on 0.5M (6.6kg/d) level of feed intake during gestation tended (P=0.06) to be greater than sows on 2.0M (5.9kg/d) level of feed intake. There were no differences (P>0.1) among 4 levels of feed intake in terms of numbers of total born and weaning piglets. However, both piglet weight at birth (1.46, 1.52, 1.53 and 1.51kg for piglets from sows on 0.5M, 1.0M, 1.5M and 2.0M levels of feed intake during gestation, respectively) and at weaning (6.37, 6.55, 6.64 and 6.38kg for piglets from sows on 0.5M, 1.0M, 1.5M and 2.0M levels of feed intake during gestation, respectively) were maximized at 1.5M level of feed intake. Sows housed in group pens had greater (P<0.01) net BW gain (24.7 vs. 19.2kg) from day 27 of gestation to weaning compared with sows housed in individual stalls. However, there were no differences (P>0.1) between the 2 housing systems in terms of litter size and piglet weight at birth and at weaning. In conclusion, increasing levels of feed intake during 4 short periods of gestation increased BW and BF gain during gestation and led to less BW gain and more BF loss during lactation. Piglet weight at birth and at weaning was maximized at 1.5M level of feed intake. However, housing systems did not affect reproductive performance. Group pen housing system may be beneficial in terms of increased overall BW gain during gestation and lactation.

In vitro physiological and antibacterial characterization of ZnO nanoparticle composites in simulated porcine gastric and enteric fluids

Background

Diarrhea in piglets is one of the main causes of animal death after weaning; zinc oxide (ZnO) has been used in high doses for the control of this sickness. The aim of this study was to determine the physicochemical properties of ZnO nanoparticles synthesized and immobilized on a chitosan/alginate (CH/SA) complex and investigate the antimicrobial activity and in vitro release profile of zinc (Zn²⁺) from these new compounds. The ZnO nanoparticles composites were prepared and combined with CH/SA or CH/SA and sodium tripolyphosphate (TPP). The structure and morphology of the composites were analyzed by characterization methods such as X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis, atomic absorption spectrophotometry and scanning electron microscopy.

Results

The crystallite size of ZnO nano was 17 nm and the novel ZnO composites were effective in protecting ZnO in simulated gastric fluid, where Zn²⁺ reached a concentration six-fold higher than the levels obtained with the unprotected commercial-zinc oxide. In addition, the novel composites suggest effective antimicrobial activity against Escherichia coli and Staphylococcus aureus.

Conclusions

The results described herein suggest that the novel nano composites may work as an alternative product for pig feeding as verified by the in vitro assays, and may also contribute to lower the zinc released in the environment by fecal excretion in animals waste.

High environmental temperature around farrowing induced heat stress in crated sows

The aim of the experiment was to study the impact of high ambient temperature (25°C) around farrowing on crated sows unable to perform thermoregulatory behavior. Twenty sows were housed in 2 farrowing rooms in conventional farrowing crates. In 1 room (CONTROL) temperature was kept at 20°C. In the other room (HEAT) temperature was initially kept at 20°C and gradually raised until it reached 25°C from d 112 to 115 of gestation. Then the temperature was gradually lowered to 20°C. Sows were continuously video recorded for behavior recording. Sows' respiration rates were recorded from d 3 before farrowing to d 5 after farrowing. Sows' rectal temperatures were recorded from d 1 before farrowing to d 8 after farrowing, and sows' udder surface temperatures were recorded from the day of farrowing to d 3 after farrowing. All measures were recorded daily. Sows' BW were recorded at d 108 of gestation and at weaning. Sows' back fat was recorded on farrowing day, when room temperature was set again at 20°C, and at weaning. Piglets were weighed at d 1, 14, and 21. The HEAT sows spent a higher proportion of time lying in the lateral position than CONTROL sows, both during the 16 h before farrowing and the 24 h after the start of farrowing ( < 0.05), but with no difference in the amount of time spent lying down between groups ( > 0.10). The HEAT sows had higher rectal temperature on d 1 after farrowing ( < 0.05) and had udder surface temperature 0.9°C higher than that of CONTROL sows during the recording period ( < 0.05). The HEAT sows also tended to have longer farrowing duration ( < 0.10). Respiration rate was higher in HEAT sows on d 1 before farrowing and on the day of farrowing. On d 7, 8, and 9, CONTROL sows had higher feed intake ( < 0.05), and piglets from CONTROL sows were heavier at d 21 after farrowing ( < 0.05). High ambient temperature around farrowing altered sows' postural behavior. Sows reacted to the thermal challenge with higher respiration rate around farrowing, but both their rectal and udder temperatures were elevated, indicating that they were not able to compensate for the higher ambient temperature. High ambient temperature negatively influenced sows' feed intake, with negative impact on piglets' weaning weight. High temperatures around farrowing (25°C) compromise crated sows' welfare, with a potential negative impact on offspring performance.

Inclusion of Konjac Flour in the Gestation Diet Changes the Gut Microbiota, Alleviates Oxidative Stress, and Improves Insulin Sensitivity in Sows

Although dietary fibers contribute to health and physiology primarily via the fermentative actions of the gut microbiota of the hosts, few studies have focused on how these interactions influence the metabolic status of sows. Here, the effects of inclusion of konjac flour (KF) in a gestation diet on oxidative stress status, insulin sensitivity, and gut microbiota were investigated to elucidate the correlation between the microbiota and metabolic changes in sows. Sows were assigned to either control or 2.2% KF dietary treatment during gestation. The gut microbiota population in sows during gestation and lactation was assessed by 16S rRNA gene sequencing. The oxidative stress parameters, homeostasis model assessment (HOMA) values, and fatty acids in the blood of sows were also assessed. Compared to the control diet group, KF significantly reduced the serum levels of reactive oxygen species (ROS) and 8-hydroxy-deoxyguanosine (8-OHdG) but increased the serum concentrations of glutathione peroxidase (GSH-Px) in sows on day 1 in lactation. Additionally, sows in the KF group had a lower HOMA insulin resistance value but a higher HOMA insulin sensitivity (HOMA-IS) value. KF induced changes in the gut microbial composition at the phylum and genus levels. The increased relative abundances of Akkermansia and Roseburia in the KF group were positively correlated with the HOMA-IS. Overall, dietary KF alleviated oxidative stress and improved insulin sensitivity of sows, and the changes in the gut microbiota in response to KF may have been correlated with the host metabolism response.

IMPORTANCE

To date, the effect of dietary fiber on metabolism responses and gut microbiota in sows has not been investigated. Here, KF supplementation of a gestation diet in sows was found to alleviate oxidative stress and to improve insulin sensitivity. Pyrosequencing analysis revealed that KF treatment induces changes in the gut microbiota composition at the phylum and genus levels. Moreover, the changes of gut microbiota in response to KF may be correlated with the host metabolism response.

Reproduction of group-housed sows

The sow is a social animal in her behavior throughout the reproductive cycle. An exception to her preference for being a part of a social group occurs one to two1–2 d days prior to farrowing, when she separates from her group and seeks for isolation in order to build up a nest. She then spends the first week or two with her piglets, mainly in the nest. After this short period of separation of 1–2 weeks, she brings her litter with her and rejoins the group. In modern intensive pig production, the sow is often restricted to an individual cage for lactation and, in many European countries, she may still spend additional periods in stalls during pregnancy. In the intensive production, isolation of the sow from the rest of the group is therefore a relatively long period of six to ten6-10 weeks, which creates a challenge for the social memory of the sow. While grouping of sows during lactation is an interesting option, until now this is encountered mostly in organic or otherwise extensive farming systems, such as outdoor farming. However, the present society is asking for more animal friendly models of production and there appears to be more need for studies of group housing issues during lactation. Grouping of sows after weaning causes stress, which imposes risks for fertility. Thus, timing of grouping is probably very critical. It is well documented that the embryonic period of the pregnancy, lasting up to Day 35, is more vulnerable for loss of pregnancy than the subsequent fetal period. There are indications that stress of grouping may cause some harm to vitality parameters of blastocysts already while at the site of fertilization in the oviduct. Later on, during the critical periods of maternal recognition of pregnancy, endocrinological models testing maintenance of pregnancy suggest that chronic stress lasting for more than two2 days may cause abortion and loss of the whole litter. However, the sow may be resistant, in terms of her reproductive function, to acute stress lasting for hours or up to a day. In conclusion, grouping of sows during lactation may be of interest in the future. At present, issues of group housed sows after weaning and early pregnancy seem to be of most practical relevance. Chronic stress of sows lasting for more than two2 days may lead to loss of the whole litter.

Fertility of sows fed ad libitum with a high fibre diet during pregnancy

The effect of ad libitum (ADLIB) feeding strategy on the fertility of the group housed sow was studied in a prospective field trial during 1.5 years. All study animals farrowed under standard farrowing circumstances in crates, and they were provided with an ad libitum feeding throughout the 30-day lactation. After weaning, animals were randomly allocated to one of the two dry sow feeding strategies (AD LIB or CONT). After oestrus detection in groups, they were artificially inseminated and moved into pregnancy pens with partially slatted floor, in groups of 40 sows each. The ADLIB sows (n = 447) were loose housed and provided with ad libitum access to 7.7 MJ/kg feed high in fibre from two feeders per group. The control sows (n = 479; CONT) were also loose housed and given a standard dry sow feed in feeding stalls once a day (2.5 kg/day. The energy content of the feed was 9.3 MJ/kg NE). The feeding strategy (ADLIB vs CONT) had no effect on pregnancy rate (85.8 vs 90.9, p > 0.05), weaning to oestrus interval (7.7 vs 7.3 days, p > 0.05), piglets born alive (11.5 ± 3.5 vs 11.6 ± 3.3, p > 0.05), stillborn piglets (1.2 ± 1.8 vs 0.9 ± 1.5, p > 0.05) nor on progesterone concentration (p > 0.05). CONT sows weaned more piglets (9.7 ± 2.2 vs 9.4 ± 2.0, p < 0.01), whereas the piglets of AD LIB sows were heavier at weaning (8.8 ± 0.9 vs 8.0 ± 1.3 kg, p < 0.05). In conclusion, ad libitum feeding with a high in fibre diet during pregnancy did not affect the reproductive performance.

Effects of dietary fibre on behaviour and satiety in pigs

During the past decades there has been considerable interest in the use of dietary fibre in both animal and human nutrition. In human subjects dietary fibre has been studied intensively for possible effects on body-weight management and health. In animal nutrition the interest in dietary fibre has increased because it can be used as a cheap source of energy and because of its potential to improve animal welfare and reduce abnormal (mainly stereotypic) behaviour. Animal welfare is impaired if the diet does not provide sufficient satiety, combined with an environment that does not meet specific behavioural requirements related to natural feeding habits (e.g. rooting in pigs). A considerable proportion of the behavioural effects of dietary fibre are thought to be related to reduced feeding motivation. It has been hypothesized that: (1) bulky fibres increase satiety and thereby decrease physical activity and stereotypic behaviours immediately following a meal in pigs; (2) fermentable fibres prolong postprandial satiety and thereby reduce physical activity and appetitive behaviours for many hours after a meal. The validity of these hypotheses is examined by considering published data. In sows dietary fibres (irrespective of source) reduce stereotypic self-directed behaviours and substrate-directed behaviours, and to a lesser extent overall physical activity, indicating enhanced satiety shortly after a meal. Furthermore, fermentable dietary fibre reduces substrate-directed behaviour in sows and physical activity in sows and growing pigs for many hours after a meal. Evidence of long-term effects of poorly-fermentable fibre sources is inconclusive. The findings suggest that highly-fermentable dietary fibres have a higher potential to prolong postprandial satiety.

Effect of alterations in the quantity and composition of the pre-mating diet on embryo survival and foetal growth in the pig

This trial examined the effects of feeding six diets, which varied in either amount or composition, during the oestrous cycle prior to insemination on embryo survival and foetal development on day 27+/-2 of pregnancy in gilts. Ten or 11 gilts per group received either a maintenance (M) diet, 1.8 x M, 2.6 x M or nutritionally balanced diets in which the content of fibre, protein or starch was increased. Of the six diets tested, only the high fibre diet significantly increased embryo survival when compared to its 1.8 x M isoenergetic control (88.20+/-1.96% versus 81.25+/-2.67%; P<0.05). More litters from gilts fed the 1.8 x M and the starch diets had foetuses defined as intra-uterine growth retarded (IUGR; 50% and 62.5 of litters, respectively), compared to the other four groups in which 0-12.5% of litters contained IUGR foetuses (P<0.05). There was no effect of dietary treatment on foetal or placental size or on the within-litter variability in foetal and placental size. Plasma concentrations of oestradiol and progesterone on days 4-8 of the oestrous cycle and on day 27+/-2 of pregnancy were unaffected by treatment. Feed intake was positively related to mean plasma IGF-1 concentrations on days 4-8 of the cycle (P<0.01) and to mean leptin concentrations on days 4 and 5 (P<0.001). Leptin concentrations were unaffected by alterations in the composition of the diet, whereas IGF-1 concentrations were higher in gilts fed the starch diet compared to the M control (159+/-9.52 versus 127+/-7.65 ng/ml; P<0.05). These data demonstrate that alteration to the composition of the feed consumed during the cycle before insemination can affect both embryo survival and the distribution of foetal size within the litter. The underlying mechanism(s) remain to be determined, but probably involve dietary-induced changes in concentrations of reproductive hormones and/or intermediary metabolites that in turn affect ovarian follicular and oocyte development.