A 2 × 2 factorial experiment was conducted to investigate the effect of maternal supplementation from day 83 of gestation and/or direct supplementation from weaning of a bovine casein hydrolysate plus a yeast β‑glucan (CH-YBG) on pig performance and intestinal health on day ten post‑weaning. Twenty cross bred gilts (Large White × Landrace) were randomly assigned to one of two dietary groups (n = 10 gilts/group): basal diet (basal sows) and basal diet supplemented with CH‑YBG (supplemented sows) from day 83 of gestation until weaning (2g/sow/day). At weaning, 120 pigs (6 pigs/sow) were selected. The two dam groups were further divided, resulting in four experimental groups (10 replicates/group; 3 pigs/pen) as follows: 1) BB (basal sows + basal pigs); 2) BS (basal sows + supplemented pigs); 3) SB (supplemented sows + basal pigs); 4) SS (supplemented sows + supplemented pigs). Supplemented pigs were offered 0.5g CH‑YBG/kg of feed for 10 days post-weaning. On day 10 post‑weaning, 1 pig/pen was humanely sacrificed and samples were taken from the gastrointestinal tract for analysis. Pigs weaned from supplemented sows (SS, SB) had reduced faecal scores and incidence of diarrhoea (P<0.05) compared to pigs weaned from basal sows (BB, BS), with SS pigs not displaying the transient rise in faecal scores seen in the other three groups from day 3 to day 10 post‑weaning (P<0.05). Pigs weaned from supplemented sows had reduced feed intake (P<0.05), improved feed efficiency (P<0.05), increased butyrate concentrations (P<0.05), increased abundance of Lactobacillus (P<0.05) and decreased abundance of Enterobacteriaceae and Campylobacteraceae (P<0.05) compared to pigs weaned from basal sows. In conclusion, maternal supplementation increased the abundance of Lactobacillus and decreased the abundance of Enterobacteriaceae and Campylobacteraceae while also increasing butyrate concentrations. The combination of maternal and direct supplementation led to pigs having the lowest faecal scores compared to all other groups.

A total of 20 pregnant gilts (Large White × Landrace genetic lines) were blocked according to live weight and backfat and randomly assigned to one of two dietary groups (n = 10 gilts/group): D1) basal gestation/lactation diet (basal sows) and D2) basal gestation/lactation diet plus CH‑YBG (supplemented sows) from day 83 of gestation until weaning (day 28). The CH‑YBG supplement (2.0 g/sow/d) contained 1.0g CH and 1.0g yeast β‑glucan. The ingredient composition of the lactation and gestation diets are presented in Table 1. The gestation diet contained 140 g/kg crude protein, 13.5 MJ/kg of digestible energy and 4.4 g/kg of standardized ileal digestible lysine. The lactation diet contained 190 g/kg of crude protein, 14.5 MJ/kg of digestible energy and 8.5 g/kg of standardized ileal digestible lysine. The amino acid requirements were met relative to lysine.

From day 83 of gestation to day 110, gilts were housed in groups of 10 according to their allocated treatment and were allowed into individual feeding crates at feeding times. On day 110, gilts were moved to individual farrowing pens (2.2m × 2.4m) with crates, slatted floors and heat pads for the piglets.  The gestation house and farrowing room temperature was maintained at 20°C throughout the experiment. The experimental supplement (CH‑YBG) was top-dressed on the gestation diet and added to the trough prior to feeding the lactation diet each morning (9am) to ensure consumption. The dams received specific amounts of feed in the following quantities: 2.5 kg/d of gestation diet from day 83 until day 110 of gestation. They were fed 2.0 kg/d of lactation diet from day 111 of gestation until the day of farrowing and then the feed supply increased by 1.0 kg/d until day 3 post‑farrowing and by 0.5 kg/d until day 6 post‑farrowing. Afterwards, the sows were allowed semi-ad libitum of the diet, which was adjusted for each sow depending on daily intake. The sows were fed in 2 equal meals provided at 9am and 3pm. The sows had ad libitum access to drinking water throughout the experimental period. 

On the expected farrowing date, fresh sow faecal samples, which did not come in contact with the floor, (approximately 10 g, (SD=1.0)) were collected from each sow into sterile containers and stored at -20°C for microbial analysis. Farrowing was not induced but all were supervised to ensure that there was no difficulty while farrowing. At parturition, each piglet was individually weighed, and the number of live born piglets were recorded. Six piglets of average birth weight (3 boars and 3 gilts) were selected from each litter and ear-tagged shortly after birth. Litter size was adjusted shortly after birth by cross-fostering piglets within dietary groups to ensure that sows nursed a similar number of piglets (12 per sow), and this was maintained throughout the suckling period. No creep feed was offered to the piglets throughout the lactation period, and piglets had no access to the sow’s feed. Piglets received an intramuscular injection of Fe-dextran (Ferdex 100; Medion Farma Jaja, Indonesia) on day 7 after birth.

At weaning, the 120 previously selected pigs (6 pigs/sow) remained in the same group defined by their dams and subdivided into two groups of 3 pigs, resulting in four experimental groups. The two factors, lactation diet and post-weaning diet, were arranged in a 2 × 2 factorial to provide the four experimental groups that were randomly assigned to replicate pens (3 pigs/pen) as follows: T1) - BB (basal sows + basal pigs); T2) - BS (basal sows + supplemented pigs); T3) - SB (supplemented sows + basal pigs); T4) - SS (supplemented sows + supplemented pigs). The current experimental design is presented in Fig 1.  Pigs from the BS and SS groups were offered the CH‑YBG supplement post-weaning at a rate of 0.5 g/kg of feed.

The starter pig performance study measured performance between day 0 and 10 post-weaning, where pigs were supplemented with or without the supplement depending on the experimental group, as described previously. The pigs were housed in groups of 3 (from original sow litter) on fully slatted pens (1.7m × 1.2m). The post‑weaning diet contained 210.6 g/kg crude protein, 15.0 MJ/kg digestible energy and 12.5 g/kg standardized ileal digestible lysine. All amino acid requirements were met relative to lysine. The diets used were formulated to create the greatest nutritional challenge possible to the post-weaned pig in the absence of in-feed medication. These diets contained a high crude protein level, high level of soya bean meal and low level of lactose. All diets were milled on site and fed in meal form for 10 days’ post‑weaning. No medication, zinc oxide or other growth-promoting agents were included in the starter diet. The ingredient composition of the post‑weaning diet is presented in Table 1. Feed and water were available ad libitum throughout the experimental period. The ambient environmental temperature within the houses was thermostatically controlled. The temperature was maintained at 30°C for the first week and was reduced by 2°C the following week. The pigs were weighed individually on the day of weaning and day 10 post-weaning. Feed intake was recorded per pen to calculate average daily feed intake.

On day 10 post‑weaning, one pig per pen (selected at birth) was sacrificed following a lethal injection of pentobarbitone sodium (Euthatal Soluion, 200mg/ml; Merial Animal Health, Essex, UK) at a rate of 0.71 ml/kg body weight to the cranial vena cava to humanely euthanise the animals. Euthanasia was completed by a competent person in a separate room away from sight and sound of the other pigs. Following this, the entire digestive tract was surgically removed. Sections from the duodenum (10cm from the stomach), the jejunum (60cm from the stomach) and the ileum (15cm from the caecum) were excised and fixed in 10% neutral-buffered formalin. tissue samples were taken from the jejunum, ileum and colon to measure the gene expression of cytokines, digestive enzymes, nutrient transporters, mucins, tight junction and appetite regulators using QPCR. Tissue sections of 1 cm² from the duodenum, jejunum, ileum and colon were cut out, emptied by dissecting them along the mesentery and rinsed using sterile phosphate buffer saline (PBS) (Oxoid, Hampshire, UK). The tissue sections were stripped of the overlying smooth tissue before storage in 5ml RNAlater® solution (Applied Biosystems, Foster City, CA, USA) overnight at 4°C. The RNAlater® was removed before storing the samples at -80°C. Digesta samples (approximately 10g) from the caecum and colon were aseptically collected into sterile containers (Sarstedt, Wexford, Ireland) and immediately frozen for subsequent 16s rRNA sequencing and VFA analysis.