Effects of dietary xylanase supplementation on growth performance, intestinal health, and immune response of nursery pigs fed diets with reduced metabolizable energy.

ABSTRACT

This study aimed to investigate the effects of xylanase on growth performance and intestinal health of nursery pigs fed diets with reduced metabolizable energy (ME). One hundred ninety-two pigs at 8.7 kg ±â€…0.7 body weight (BW) after 7 d of weaning were allotted in a randomized complete block design with initial BW and sex as blocks. Eight dietary treatments consisted of 5 ME levels (3,400, 3,375, 3,350, 3,325, and 3,300 kcal ME/kg) below the NRC (2012) requirement and 4 levels of xylanase (0, 1,200, 2,400, and 3,600 XU/kg) to a diet with 3,300 kcal ME/kg. All pigs received their respective treatments for 35 d in 2 phases, pre-starter (14 d) and starter (21 d). On day 35, eight pigs in 3,400 kcal/kg (CON), 3,300 kcal/kg (LE), and 3,300 kcal/kg + 3,600 XU xylanase/kg (LEX) were euthanized to collect jejunal tissues and digesta for the evaluation of mucosa-associated microbiota, intestinal immune response, oxidative stress status, intestinal morphology, crypt cell proliferation, and digesta viscosity as well as ileal digesta to measure apparent ileal digestibility. Data were analyzed using the MIXED procedure on SAS 9.4. The LE increased (P < 0.05) jejunal digesta viscosity, tended to have decreased (P = 0.053) relative abundance of Prevotella, and tended to increase (P = 0.055) Lactobacillus. The LE also increased (P < 0.05) the concentration of protein carbonyl whereas malondialdehyde, villus height (VH), villus height to crypt depth ratio (VHCD), apparent ileal digestibility (AID) of nutrients, and finally average daily feed intake were decreased (P < 0.05). The LE did not affect average daily gain (ADG). The LEX decreased (P < 0.05) digesta viscosity, increased (P < 0.05) the relative abundance of Prevotella, decreased (P < 0.05) Helicobacter, decreased (P < 0.05) the concentration of protein carbonyl, tended to increase (P = 0.065) VH, and decreased (P < 0.05) VHCD and crypt cell proliferation. Moreover, LEX increased (P < 0.05) the AID of dry matter and gross energy and tended to increase (P = 0.099; P = 0.076) AID of crude protein, and ether extract. The LEX did not affect ADG but did tend to decrease (P = 0.070) fecal score during the starter phase. Overall, reducing ME negatively affected intestinal health parameters and nutrient digestibility without affecting growth. Supplementation of xylanase mitigated some of the negative effects observed by ME reduction on intestinal health and digestibility of nutrients without affecting growth.

Dietary inclusion of fats in the feeds of nursery pigs allows nutritionists to increase the energy density of the feed. Some researchers believe the value of adding fat in nursery feeds goes beyond meeting the energy specification of the feed but rather as a supply of fatty acids that can regulate various bodily processes. Volatility in feedstuff prices has resulted in increased inclusion of coproducts rich in nonstarch polysaccharides (NSP) and a decrease in dietary fat in nursery pig diets in an effort to boost economic sustainability with minimal compromise of growth. Common feedstuffs of plant origin possess an inherent amount of NSP that can elicit negative effects on the digesta viscosity, intestinal microbiota, and digestibility of nutrients. Supplemental enzymes such as xylanase target specific NSP components within the feed to alleviate some of these negative effects and may release otherwise indigestible nutrients for absorption. The aim of this study was to investigate the impact of reducing metabolizable energy (ME) of the feed up to 100 kcal ME/kg on growth performance, intestinal health, immune status, and the composition of the mucosa-associated microbiota as well as the ability of xylanase to mediate the negative effects imposed by a reduction in supplemental fat to lower ME.