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Selection for hyperprolific sows, as a means of increasing litter size and profit, has resulted in an increased number of low-birthweight ( LBW) piglets. These LBW piglets might suffer from increased morbidity and mortality during the early neonatal period. In addition, they show reduced growth performance, meat and carcass quality, which leads to an important economic loss for the farmer in the post-natal period. Therefore, nutritional interventions can be undertaken to prevent and rear LBW piglets. In the first part of this review, the preventive strategies at the sow level will be discussed. Approaches in preventing LBW piglets are to optimize the intrauterine environment via supplementing the sow during gestation. In the second part of this review, the interventions at the piglet level will be described. To increase the survival and growth rates of LBW piglets, one must focus on ensuring adequate colostrum and milk intake. Interventions include supplementing piglets, split nursing, split weaning and cross-fostering. Additional interventions increasing the probability of optimal post-natal food intake will be discussed. [ABSTRACT FROM AUTHOR]

A mature enteric nervous system (ENS) is required to ensure a normal pattern of intestinal motility in order to regulate digestion after birth. We hypothesized that neuronal and glial components of the ENS would mature during the first postnatal days in preterm pigs that are a sensitive animal model of food intolerance and necrotizing enterocolitis (NEC). Stereological volume densities of the general neuronal population [assessed by βIII-tubulin immunoreactivity (IR)] and subsets of neuronal (VIP-IR and nitrergic IR) and glial cells (GFAP-IR and S100-IR) were determined in the small intestine of newborn preterm piglets (93% gestation), after 3 days of receiving total parenteral nutrition (TPN) and after 3 days of TPN plus 2 days of enteral feeding with sow’s colostrum or milk formula. Following TPN, VIP in the myenteric and inner submucous plexus and GFAP in the inner submucous plexus increased, while the relative volume of the total neuronal population remained constant. Introduction of enteral food induced variable degrees of food intolerance and NEC, especially after formula feeding, a diet that gave rise to a higher myenteric VIP and GFAP content in the inner submucous plexus than colostrum feeding. However, the ENS seemed unaffected by the presence of NEC-like intestinal lesions. Nevertheless, this study shows that the ENS is highly plastic during the first days after premature birth and adapts in an age- and diet-dependent manner. The observed postnatal adaptation in enteric VIP and GFAP may help to maintain intestinal homeostasis during suboptimal feeding regimens in preterm neonates. [ABSTRACT FROM AUTHOR]

In term neonates, total parenteral nutrition (TPN) induces mucosal atrophy, whereas the first intake of milk is followed by intestinal growth. This may be explained in part by an NO-mediated increased blood flow. We hypothesized that the immature gut has an altered response to TPN and enteral nutrition. In Expt. 1, preterm caesarean-delivered pigs were administered elemental nutrients for 3 d, infused parenterally (TPN, n = 7) or enterally (TENT, n = 7). In Expt. 2, preterm pigs were fed sow's colostrum, cow's colostrum, or infant formula for 2 d after a 3-d TPN period (TPN-SOW, TPN-COW, TPN-FORM, n = 8-11). Intestinal morphology and the number of enteric neurons containing nitric oxide synthase-1 (NOS-1) were quantified. Both the TPN and TENT groups had increases in intestinal mass, circumference, and mucosal mass, volume, and surface density, relative to values at birth (+30-50%, P < 0.05). In Expt. 2, the magnitudes of the intestinal trophic responses to feeding were similar to those in Expt. 1, but were also associated with an increased number of nitrergic myenteric neurons and some mucosal damage, most frequently observed for the formula group. We conclude that 1) a short period of TPN does not induce mucosal atrophy in preterm pigs, whereas elemental nutrients infused luminally do not mimic the trophic response seen with milk diets, 2) enteral feeding of preterm pigs after a short period of TPN is associated with a modest, diet-dependent trophic response that may be related in part to the actions of an increased population of enteric NOS-1 neurons. [ABSTRACT FROM AUTHOR]

• Co-mingling resulted in an improved average daily gain the first 2 weeks. • Feed familiarity temporarily improved average daily gain and feed intake at weaning. • Co-mingling combined with feed familiarity did not further improve the weaning response. • Co-mingling impacted on the hematological status at weaning. This study investigated how co-mingling of non-littermates before weaning and feed familiarity at weaning in a 2 × 2 factorial design can minimize the adverse effects related to conventional weaning. Before weaning, piglets were either conventionally reared or co-mingled by grouping piglets from 3 litters during 10 days before weaning. At weaning, piglets from 3 litters were distributed over 3 pens in the nursery. Conventionally reared piglets from 3 litters were mixed, whereas the co-mingled piglets were housed with those they were co-mingled with before weaning. At weaning, piglets were either or not provided with 0.538 kg creep feed per piglet in creep feeders, next to the weaner diet. Creep feed was the same provided the last 4 days before weaning. Hence, the treatment groups were conventional with (n = 9) or without creep feed (n = 9), and co-mingling with (n = 9) or without creep feed (n = 9). Co-mingling non-littermate piglets did not affect weaning weight, daily weight gain and creep feed intake during d -10-d0 before weaning. Co-mingling resulted in higher skin lesion scores of head and ears in piglets at d1 before weaning (P < 0.05), but in lower skin lesion scores at the snout, shoulders and flanks at d2 post-weaning compared to conventionally reared piglets (P < 0.05). Co-mingling did not affect salivary cortisol at d1 post-weaning. Hematocrit, hemoglobin, mean corpuscular volume and mean corpuscular hemoglobin were higher in the co-mingled piglets at d2 post-weaning (P < 0.05). Co-mingling resulted in higher glucose concentrations in blood (P < 0.05) and in a tendency for lower NEFA concentration in serum at d2 post-weaning (P < 0.10). Feed familiarity at weaning increased average daily feed intake and weight gain during the first 5 days post-weaning (P < 0.05). During d5–14 post-weaning average daily feed intake tended to be lower (P < 01.0) and daily gain was lower (P < 0.05) in creep feed fed piglets compared to no creep feed fed piglets. Nevertheless, feed familiarity did not affect overall piglet performance during the first 2 weeks after weaning. Feed familiarity did not affect blood hematology and biochemical blood parameters, except the level of basophils at d2 post-weaning. Neither housing nor feeding strategy affected piglet performance between d14–42 post-weaning and ear and tail damage at d42 post-weaning. In conclusion, pre-weaning co-mingling of piglets and feed familiarity at weaning each contributed to a better adaptation of the weaning process but did not affect long-term piglet performance. [ABSTRACT FROM AUTHOR]

The high prolificacy of modern hybrid sows has increased the mean litter size during the last decades. However, rearing large litters is challenging and has increased the use of alternative management strategies such as euthanasia of weak piglets, cross-fostering, supplementing piglets with milk, split-nursing and split-weaning. The latter includes artificial rearing on brooders where piglets have ad libitum access to milk replacer. The effect of this artificial rearing on the immune system of the piglet is the subject of various studies. The present study focused on the M cells in the tonsil of the soft palate and in the ileal Peyer's patch (iPP). These epithelial cells are specialized in antigen sampling and play a pivotal role in the induction of adaptive immune responses. The volume densities of the M cells were assessed by stereological analysis of tissue samples from piglets of 0, 3, 8 and 19 days of age. During the first three days, piglets suckled the sow, permitting them to ingest colostrum. At the third day, the piglets were either allowed to continue to suckle the sow or were transferred to brooders. The six experimental groups, each containing six piglets, thus consisted of newborn piglets, 3-day-old sow-suckled piglets, and conventionally and artificially reared piglets of 8 and 19 days of age. To identify M cells, tissue samples were immersed in 4% phosphate-buffered paraformaldehyde and paraffin sections were immunohistochemically stained against cytokeratin 18. The volume densities of M cells in both the crypt epithelium of the tonsils of the soft palate and the follicle-associated epithelium of the iPPs did not show any difference between the various age groups of conventionally reared piglets. However, values were twice as high in the iPPs compared to the tonsils of the soft palate. In contrast, a decrease in volume densities of M cells was observed in the iPPs of piglets after they had been transferred to commercial brooders ( P = 0.05), resulting in significantly lower values ( P = 0.04) in comparison with the age-matched sow-suckled groups. However, this observation did not translate to values of the tonsils where M cell volume densities remained the same in all age and rearing groups. Based on these results, it appears that antigen sampling is possible from birth onwards and is more advanced in the small intestine than in the oropharynx, but possibly lags behind in artificially reared piglets. [ABSTRACT FROM AUTHOR]

• Co-mingling non-littermates before weaning did not affect sow's body condition. • Overall pre-weaning performance was not affected by co-mingling. • Co-mingled piglets had less skin lesions immediately after weaning. • Overall post-weaning piglet performance was not improved by co-mingling. • Timing of co-mingling non-littermates before weaning seemed not crucial. The natural weaning process of piglets is a gradual event, whereas in current commercial pig production weaning is a sudden, stressful phase in the pigs' life. Management strategies such as co-mingling of non-littermates before weaning aim to mimic (semi)natural conditions and to stimulate social skills in piglets in order to minimize the adverse effects of stress around weaning. The present study investigated in which way timing of co-mingling non-littermate piglets during lactation in conventional farrowing units had implications for the sow and affected the performance and behaviour of piglets before and after weaning. In the experimental treatments, 3 litters were co-mingled either at day 16 before weaning (n = 27 sows and their litters), day 11 before weaning (n = 27) or day 6 before weaning (n = 27). In the control treatment, piglets were not grouped before weaning (n = 27). In total, 1294 piglets were weaned at 21 days of age. At weaning, piglets from 3 litters within each treatment were mixed. Piglets from the co-mingling system were housed with those they were co-mingled with during lactation, whereas control piglets were mixed with unfamiliar piglets. Co-mingling of non-littermate piglets did not affect sow body condition and lesion scores of udder and teats during lactation. Piglets co-mingled 6 days before weaning tended to gain less weight during d-6 – d-1 before weaning (P = 0.082), but piglet growth was not affected during d-16 – d-1. After weaning, the feed to gain ratio in piglets which were co-mingled 6 days before weaning tended to be lowest during the first week after weaning (P = 0.086), but no other treatment effects were observed in the post-weaning phase. Skin lesion score of the shoulders and flanks tended to be higher at day 11 before weaning in piglets co-mingled 16 days before weaning (P = 0.051) and was highest at day 6 before weaning in piglets co-mingled 11 days before weaning (P < 0.001). However, 1 day before weaning no differences in skin lesions were observed. After weaning, the socialized piglets had less skin lesions at the shoulders and flanks compared to control piglets (P < 0.001). In conclusion, pre-weaning co-mingling of non-littermates resulted in less aggression (i.e. lesions) at weaning, suggesting better social skills and a reduction of stress, consistent with a tendency for improved feed to gain ratio in the first week after weaning. Time of co-mingling seemed not crucial. [ABSTRACT FROM AUTHOR]

• Split-suckling did not favour colostrum intake of the smallest piglets. • When applied daily in first three lifedays, growth of isolated piglets was lower. • When applied only in first lifeday, piglets' growth was restored. • Higher mortality was seen when split-suckled for three days, yet litter size was higher. The objective was to investigate the effect of split-suckling on the performance of piglets during the first three days of life. Split-suckling implies that not all piglets have access to the udder at all times; i.e. the litter is split-in two or more groups being nursed in alternating order, or only the heaviest piglets are enclosed temporarily; in order to benefit colostrum consumption and survival of disadvantaged neonates. The experiment included three treatments: no split-suckling (CON) (n = 111), split-suckling was applied only in the first day of life (SS1d) (n = 174), and split-suckling was applied during the first three days of life (SS3d) (n = 184). Split-suckling involved alternated nursing of two groups every three hours in order to privilege nursing of the third group for 12 h per day. The two groups which were removed from the sow included the heavier piglets either born in first part or second part of parturition. Group sizes of these two groups were equal and depended on the litter size and the criterion that at least 10 piglets remained with the sow during split-suckling. Split-suckling started after farrowing was completed. In total, 469 piglets from 28 litters were followed for colostrum intake, growth and mortality. Colostrum intake did not differ between treatments. However, colostrum intake of heavy piglets in SS1d and SS3d were lower when compared to CON (P < 0.05). Growth at 24 h post-farrowing was lower in SS3d (51 ± 5 g) as compared to CON (82 ± 7 g) (P = 0.001), and intermediate in SS1d (65 ± 6 g). Further, growth at 72 h post-farrowing was lower in SS3d (82 ± 4 g/d) as compared to CON (110 ± 6 g/d) and SS1d (101 ± 4 g/d) (P < 0.001). Thus, heavier piglets in SS1d were able to catch up growth loss, contracted during first day of life, by the third day of life. When piglets were split-suckled for three days, growth continued to be impaired. Furthermore, mortality at 72 h post-farrowing did not differ between treatments but was higher amongst the non-isolated piglets within SS3d compared to those within SS1d (P = 0.007). In conclusion, piglet performances were not improved nor impaired when split-suckling was applied during the first day of life. However and on the contrary, growth was impaired when litters were intensively split-suckled during first three days of life. [ABSTRACT FROM AUTHOR]

• Stressed piglets gained significantly less weight than controls between 7 and 28 days of age. • Hair from the stressed group contained significantly higher concentrations of cortisol than hair from controls. • Salivary cortisol concentrations did not differ significantly between stressed and control groups at Day 28. • Weight gain was significantly and negatively correlated with hair cortisol concentrations in the stressed group after 3 weeks. • Weight gain and hair cortisol concentrations did not correlate with salivary cortisol concentrations at Day 28. Hair cortisol might better represent chronic stress than salivary cortisol in piglets. To test this hypothesis, 24 female, 7-day old piglets were allocated to two groups and artificially reared. The piglets in the stressed group were exposed to overcrowding (0.10 m2/piglet) and frequent mixing with unfamiliar piglets until the age of 28 days. The control group remained in an unchanging group at a density of 0.29 m2/piglet. After 3 weeks, stressed animals had gained significantly less weight (median, here and throughout, 7.58 kg) than the control animals (6.43 kg; P = 0.021). Additionally, hair from the stressed group contained significantly higher cortisol concentrations (87.29 vs. 75.60 pg/mg hair; P = 0.005), whereas salivary cortisol concentrations did not significantly differ between groups (0.30 vs. 0.25 μg/dL saliva; P = 0.447). Weight gain and hair cortisol concentrations were significantly correlated (P = 0.036, r = −0.430), but neither of these parameters were correlated with salivary cortisol concentrations (P = 0.929, r = 0.019 and P = 0.904, r = 0.026, respectively). [ABSTRACT FROM AUTHOR]