Yeast extract could be used as a partial substitute for spray-dried porcine plasma in diets for weaned pigs

Highlights

• Weaning diets supplemented with yeast extract (YE) and spray-dried porcine plasma (SDPP) could improve growth performance (ADG, feed efficiency and ATTD of CP) of piglets compared with control diet.

• YE as a partial replacement of SDPP in diet could stimulate the immune responses by improving IgG and IgM content and decreasing TNF-α and IL-6 concentration in serum.

• Yeast extract could be a partial substitute for spray-dried porcine plasma in diets for weaned pigs in terms of positive growth performance and immune function.

Abstract

The previous study has been identified that yeast extract (YE) could be a potential substitute for spray-dried porcine plasma (SDPP) as a superior protein ingredient in diets for pigs in terms of the available energy and AA digestibility. This experiment was conducted to test the hypothesis that YE as a partial substitute for SDPP in diet could stimulate the immune responses and improve the performance and nutrient digestibility in weaned pigs. A total of 90 healthy pigs weaned at 28 d of age (8.5 ± 1.2 kg) were assigned into 3 treatments according to sex and weight in a randomized complete block design. The dietary treatments consisted of a negative control diet without YE and SDPP supplementation (NCD), NCD supplemented with 40 g/kg SDPP at the expense of soybean meal (SDPPD) or SDPPD supplemented with 20 g/kg YE at the expense of SDPP (YED). During the 28-d experimental periods, pigs fed YED and SDPPD improved average daily gain (P < 0.05) and feed efficiency (P < 0.05) compared with pigs fed NCD. No statistical differences in performance were observed between YED and SDPPD. The apparent total tract digestibility of crude protein was greater in pigs fed SDPPD and YED than those fed NCD (P < 0.05). Compared with pigs fed NCD, pigs fed YED decreased (P < 0.05) or tended to decrease (P = 0.09) urea nitrogen and diamine oxidase contents in serum. The serum IgG and IgM content was greater in pigs fed SDPPD and YED than those fed NCD (P < 0.05). The SDPPD and YED decreased serum tumor necrosis factor-α in comparison with NCD (P < 0.05). The YED decreased serum interleukin-6 (P < 0.05), and SDPPD increased serum interleukin-10 compared with NCD (P < 0.05). No statistical differences in small intestinal morphology or hindgut volatile fatty acids were detected among the treatments. Accordingly, YE could be a partial substitute for SDPP in diets for weaned pigs in terms of positive growth performance and immune function.

Introduction

Weaning stress could result in numerous challenges for pigs, including diarrhea, impaired performance, and increased mortality (Pluske et al., 1996, Pan et al., 2017a2017c). One effective approach to relieve weaning stress is to supplement appropriate animal protein sources in the weaned diets (Tokach et al., 2003, Pan et al., 2016a). Animal protein sources are especially significant for weaning pigs and provide nutritional advantages over plant protein sources (Maxwell and Carter, 2001). Spray-dried porcine plasma (SDPP) as high-quality animal protein is commonly used in early weaned diets to improve performance (Pierce et al., 2005, Song et al., 2012) and to enhance immune function of weaned pigs (Bosi et al., 2004, Corl et al., 2007). However, conventional animal protein resources such as SDPP are in short supply (Zhang et al., 2015a, Pan et al., 2016a), and the use of SDPP in pig industry has been inhibited in many countries for its potential bio-security risk and high cost (Van Dijk et al., 2001, Che et al., 2012). Thus, there is an increasing interest in recent years to find new potential protein source supplements to replace SDPP in weaned diets.

Yeast extract (YE) separated from inner yeast cell could be a functional source of nutrients, since it is rich in peptides and nucleotides (Pereira et al., 2012). Dietary nucleotides as one group of bioactive agents are supposed to diminish challenges of pigs related to weaning by stimulating the immune system and maintaining a beneficial intestinal environment (Andre´s-Elias et al., 2007, Sauer et al., 2011). Numerous studies have been reported that YE as a superior protein ingredient to substitute SDPP for weaned pigs had beneficial effects on the performance, immune function and intestinal health (Carlson et al., 2005, Pereira et al., 2012, Hu et al., 2014). Additionally, our team have identified YE could be a potential substitute for SDPP as a superior protein ingredient in diets for pigs in terms of the available energy and apparent and standardized ileal digestibility of amino acid (Wu et al., 2017a). Based on our previous studies, we hypothesized that YE could replace SDPP partially to improve growth performance of weaned pigs by stimulating the immune responses. Therefore, the objective of the experiments is to evaluate the effects of YE as a partial substitute for SDPP on growth performance, immune function and intestinal health in weaned pigs.