Effect of whole wheat feeding on gastrointestinal tract development and performance of growing turkeys

Abstract

The objective of this study, performed on 350 four-wk-old heavy-type Hybrid Converter male turkeys, was to assess the effect of increasing dietary levels of whole grain wheat (W) applied at the expense of ground-pelleted wheat (GW) on intestinal development and morphological indices, cecal microbiota, and the growth performance of birds. The basal diet was composed of ground-pelleted wheat and pelleted protein–fat–mineral–vitamin concentrate mixed at the proportion of 50:50 and 60:40 (w/w) in 5–8 and 9–12 wk of feeding, respectively (W₀ diet). In the diets denoted as W₂₅, W₅₀, W₇₅ and W₁₀₀, whole grain was added at the expense of 25, 50, 75 and 100% of the total dietary content of wheat, respectively. In 9–12 wk, daily feed intake tended to decrease with an increase in the W content of diets (linear contrast, P=0.073). Over the entire experiment, an increase in W inclusion levels was followed by a linear decrease in the body weight gains and feed conversion ratio of turkeys (P<0.001 in both cases). The viscosity of small intestinal digesta as well as the relative weight of gizzard tissue and cecal digesta increased linearly with elevated dietary levels of whole grain wheat. At the same time, the digesta pH, ammonia concentrations and total short-chain fatty acid concentrations in the ceca decreased linearly in the treatments with increased amounts of whole wheat. An increase in dietary W levels was accompanied by a tendency toward a linear increase in the thickness of muscularis externa and a decrease in crypt depth in the duodenum (P=0.096 and P=0.097, respectively), and a linear decrease in cecal villus height (P=0.030). Increasing W levels in diets had no influence on total bacterial counts per g of cecal digesta, including Bacteria, Lactobacillus, Enterococcus, Bifidobacterium, Salmonella and Bacteroides, whereas a linear decrease was observed in the counts of Escherichia coli (P=0.001), Clostridiaceae (P=0.023) and Clostridium perfringens (P=0.001). The replacement of GW with higher levels of W linearly increased excreta dry matter concentrations (P=0.003) and alleviated the symptoms of footpad dermatitis in turkeys (P=0.011).

Introduction

Feeding whole grains to poultry is associated with numerous benefits, including reduced costs of feed production and transport (Svihus, 2001), positive effects on morphology of the gastrointestinal tract (GIT) through increased peristaltic movement (Taylor and Jones, 2004), promotion of gizzard development that can prevent potentially pathogenic bacteria from entering the intestine (Engberg et al., 2004), and improved bird performance and feed efficiency (Biggs and Parsons, 2009). Such positive effects have been observed in numerous experiments on broilers chickens fed whole grains at 10–20% and 20–40% of the daily ration (Amerah and Ravindran, 2008, Gabriel et al., 2008, respectively). In other experiments on broilers, however, no advantages followed the dietary inclusion of whole grain wheat (Uddin et al., 1996, Jones and Taylor, 2001).

The effect of feeding whole wheat grain (W) to poultry has been evaluated by nutritionists mainly on broilers using two models of nutrition: feeding whole grain either through mixed feeding where W was added as a partial substitute for ground wheat in a complete diet or free choice feeding where W and protein concentrate were offered in separate feeders (Amerah and Ravindran, 2008). In free choice feeding, the nutritive value of a daily ingested diet containing intact grain, mainly due to the protein content, is lower than upon intake of the complete diet (Erener et al., 2003), which may result in diminished weight gain and worsen feed efficiency ratio (Amerah and Ravindran, 2008). However, the scope of research into feeding whole grain wheat to turkeys remains scarce.

A decrease in protein concentrations in the daily ration is also observed when standard diets which meet the nutrient requirements of birds are diluted with W. According to Bennett and Classen (2003), at the highest level of dilution, when W substituted 50% of commercial turkey rations, body weight (BW) and the weight of breast muscle per bird were reduced by 15% and 20%, respectively. The results of our earlier study (Jankowski et al., 2012) indicate that moderate dilution of standard turkey diets with wheat (18% on average during feeding between 4 and 18 wk of age) has no effect on the final BW of birds or muscle yield, and improves feed utilization, in particular when W is fed instead of ground pelleted grain. It was also found that supplementation of turkey diets with W improved feed conversion ratio (FCR) as a result of improved gastrointestinal tract (GIT) function, lower pH of gizzard digesta, increased crypt depth in the jejunum, lower ammonia concentrations and lower pH of intestinal digesta, a higher proportion of eubacteria and Bifidobacterium sp. and lower Salmonella sp. counts in intestinal microflora, increased concentrations of butyric acid and total SCFAs in cecal digesta (Zdunczyk et al., 2013).

The objective of the present study was to determine turkey performance and the physiological effects of diets containing increasing levels of W supplied at the expense of GW. It was hypothesized that the consumption of W would be associated with some beneficial physiological changes, including intestinal architecture, cecal microbiota and fermentation processes.