Reducing protein and supplementing crystalline amino acids, to alter dietary amino acid profiles in birds challenged for subclinical necrotic enteritis

Abstract

Necrotic enteritis (NE) is an infection of the gastrointestinal tract and is estimated to cost the global poultry industry billions of dollars annually. A study was conducted to examine whether reducing the crude protein might offset the severity of NE in broilers experimentally challenged with Eimeria spp. on day 9 and Clostridium perfringens on days 14 and 15. Furthermore, increasing the dietary amino acid (AA) density of the diet was also examined owing to identified benefits of improving performance compromised from low protein (LP) diets or NE. A 2 × 2 × 3 factorial arrangement of treatments at 6 replicates per treatment was used with 972 Ross 308 cockerels fed wheat-sorghum-soy-based diets to 35 D. Factors were NE challenge: no or yes; protein: standard (SP) or LP; and AA density: 100% AA, 115% with only essential AA (115% EAA) increased, and 115% AA with both essential and nonessential AA (115% AA) increased. The performance was measured in grower (days 7-21), finisher (days 21-35), and overall (day 7-35) periods. In addition, on day 16, intestinal lesion score and cecal short-chain fatty acids were measured. Only in nonchallenged birds fed LP diets, 115% AA increased grower feed intake (P < 0.01) and body weight gain (P < 0.05) compared to 115% EAA treatments. Challenge increased jejunal lesions (P < 0.001) with no difference between dietary treatments. Finisher body weight gain was greater in nonchallenged birds fed the 115% AA diets than in challenged birds (P < 0.05). Feeding diets with higher nonessential AA encouraged faster recovery from NE challenge. When fed the SP diets, NE challenge increased cecal butyric acid (P < 0.01) and total short-chain fatty acids (P < 0.05). The nutrient matrix used in LP diets does not favor beneficial butyric acid-producing bacteria. Using LP diets to mitigate NE severity does not offset the predisposing effect of E. spp. when attacking the gastrointestinal tract, and NE recovery is favored when feeding SP diets or additional AA.

Keywords: amino acid densities; broiler chicken; low protein; necrotic enteritis; poultry nutrition.

Figure 1

Finisher performance data two-way interactions: (A) Crude protein × amino acid density two-way interactions for finisher (day 21–35) feed intake (P < 0.01). (B) Challenge × amino acid density two-way interactions for finisher (day 21–35) body weight gain (P < 0.05). (C) Protein × amino acid density interactions for finisher (day 21–35) body weight gain (P < 0.05). (D) Challenge × amino acid density interactions for finisher (day 21–35) feed conversion ratio (P < 0.01). ^a,b,c,dDiffering superscripts indicate significant differences between means by general linear model with post hoc Tukey test (P < 0.05). Abbreviations: SP, standard protein; LP, low protein; AA, amino acids; EAA, essential amino acids.

Figure 2

Protein × amino acid density two-way interactions for overall (day 7–35) feed conversion ratio (P < 0.01). ^a,b,cDiffering superscripts indicate significant differences between means by general linear model with post hoc Tukey test (P < 0.05). Abbreviations: AA, amino acids; EAA, essential amino acids.

Figure 3

Challenge, protein, and amino acid main effects and treatment means for jejunal lesion scores. ^a,bDiffering superscripts indicate significant differences between means by Kruskal–Wallis nonparametric test (P < 0.05). Abbreviations: SP, standard protein; LP, low protein; AA, amino acids; EAA, essential amino acids.

Figure 4

Challenge × crude protein two-way interactions for (A) proximal ileal pH (P < 0.05), (B) cecal butyric acid (P < 0.01), and (C) cecal total short-chain fatty acids (P < 0.05). ^a,bDiffering superscripts indicate significant differences between means by general linear model with post hoc Tukey test (P < 0.05). Abbreviations: SP, standard protein; LP, low protein.