Effect of dietary threonine on laying performance and intestinal immunity of laying hens fed low‐crude‐protein diets during the peak production period

Abstract

Threonine (Thr) may be a limiting amino acid for laying hens fed diets with lowered protein level. An experiment was conducted to examine laying performance, and the intestinal immune function of laying hens provided diets varying in digestible Thr levels. Lohmann Brown laying hens (n = 480), 28 weeks of age, were allocated to six dietary treatments, each of which included five replicates of 16 hens. Dietary crude protein (CP) 16.18% diet was offered as the positive control diet. L-Thr was added to the negative diet (14.16% CP) by 0, 1.0, 2.0, 3.0 and 4.0 g/kg, corresponding 0.44%, 0.43%, 0.49%, 0.57%, 0.66% and 0.74% digestible Thr. At 40 weeks, a reduction in CP level decreased laying performance (p < 0.05). In the low CP, increasing dietary Thr increased (p < 0.05) egg production and egg mass and rose to a plateau between 0.57% and 0.66%. The hens fed 0.66% Thr showed the lowest value (p < 0.05) of feed conversion ratio (FCR). Serum level of uric acid showed the lowest values (p < 0.05) at 0.57-0.66%. In addition, serum-free Thr maximized (p < 0.05) between 0.66% and 0.74%. Digestive trypsin activity decreased (p < 0.05) when hens fed the low-CP diet compared with hens fed CP (16.18%) and hens fed 0.57-0.66%. Expressions of ileal MUC2 mRNA maximized (p < 0.05) at 0.66% Thr. Occludin mRNA increased with increasing Thr level (p < 0.05). sIgA mRNA reached to the maximum level (p < 0.05) at 0.66% and 0.74% Thr. INF-γ mRNA reached to the lowest level (p < 0.05) at 0.65%. Expressions of ileal IL-2, IL-6, IL-1β mRNA decreased with increasing Thr level (p < 0.05). In conclusion, Thr supplementation resulting in optimal laying performance and stimulated the mucosal immune system, suggesting that it is a limiting amino acid in the low-crude-protein diet of laying hens during the peak production period.

A deficient or an excess of dietary threonine level affects intestinal mucosal integrity and barrier function in broiler chickens

“…The function of sIgA is to prevent the penetration of micro‐organisms by blocking the adherence to mucous membranes, improving bactericidal function and neutralizing bacterial toxins (Bai, Liu, & Su, ). In the present study, the mRNA expression of sIgA and intestinal sIgA content in the jejunum and ileum increased linearly and quadratically with increasing Thr and reached to the highest level at 125% Thr level, and it was consistent with the results of Azzam et al () who reported that the mRNA expression of sIgA in the ileum increased with increasing Thr and reached to the highest level at 0.65% and 0.74% digestible Thr. Azzam et al () also found that dietary Thr linearly increased ileal sIgA content in laying hens.…”

“…In early age broilers (0–14 days), LPS‐induced alterations in the intestinal mRNA abundances of genes related to intestinal inflammation and barrier function (jejunal TLR4, IFN‐γ and claudin‐3, and ileal IL‐1 β and ZO‐1) were normalized with l ‐Thr administration (Chen et al, ). In laying hens, Azzam et al () showed that the expression levels of occludin in the ileum increased with increasing digestible Thr level form 0.44% to 0.74%. Additionally, it has been reported that piglets fed the low Thr diet exhibited increased ileal expression of ZO‐1 compared with control well‐balanced Thr diet (Hamard et al, ).…”

Effect of supplemental serine-protease from Bacillus licheniformis on growth performance and physiological change of broiler chickens

“…Therefore, protease supplementation could increase the concentration of free amino acids in breast muscle. It has been reported that the levels of total amino acids in serum, liver, feather, and carcass can reflect the amino acids utilization (Kaczmarek et al 2014;Azzam et al 2015Azzam et al , 2017Dong et al 2016;Morales et al 2017;Wecke et al 2018;Middendorf et al 2019). In addition, amino acids concentrations in carcass could be used to determine amino acid requirements accurately in broiler diets (Stilborn et al 2010;Abd El-Moneim et al 2019;Saleh et al 2019b).…”

Paternal weight of ducks may have an influence on offspring’ small intestinal function and cecal microorganisms

“…In the poultry industry, appropriate intestinal function is of great importance to achieve target growth rates and feed efficiency [2]. It has been shown that dietary threonine (Thr) affects the Bifidobacterium abundance in laying hens and thus improves their gut function and further increases their laying performance [3]. Moreover, Thr availability is closely related to the function of gut barriers, which further contributes to body weight gain [4].…”

“…Moreover, Thr availability is closely related to the function of gut barriers, which further contributes to body weight gain [4]. In addition to its effect on production performance, the intestinal mucosal barrier is also the first line of defence against hostile luminal environments, and it is therefore central for organic health [3].…”