Precision intestinal nutrition: knowledge and gaps regarding the role of amino acids during an enteric challenge

Poultry nutritionists continually strive for more “precision” nutritional programs that provide the exact balance of nutrients that maximize broiler growth performance without economically and environmentally costly excesses. Many factors affect the precise amount and balance of nutrients needed by the broiler, including genetics, age, sex, and environment. Furthermore, broilers in intensive rearing environments will almost always be subjected to some degree of enteric stress that can alter nutrient needs. Exposure to enteric pathogens such as Eimeria spp., the intestinal parasites that cause avian coccidiosis, induces physical damage to the intestinal epithelium and activates immune responses, ultimately resulting in the repartitioning of amino acids (AA) in response to these prioritized demands. Even without any pathogenic challenge, the intestine has an already high demand for many AA, with 30 to 100% of dietary AA extracted during first pass intestinal metabolism. In many cases, increasing dietary protein from intact proteins has been shown to be a viable option to ameliorate impaired AA digestion and absorption and heightened need for certain AA of birds under an enteric stress. However, increasing dietary protein often results in concomitant increases in indigestible protein and carbohydrates that can stimulate the overgrowth of pathogenic bacteria (i.e., Clostridium perfringens). Alternative options to increase dietary AA levels are to increase all feed-grade, free AA (e.g., Met, Lys, Thr, Val), or specific individual feed-grade AA. Therefore, the objectives of this paper are to discuss precision nutrition, the dietary AA demands of the intestine, consequences of coccidiosis on AA needs of the intestine, and formulation approaches to meet these altered needs. In summary, increased dietary protein met by intact proteins has consistently demonstrated its benefits during an Eimeria spp. infection; however, to further the goal of precision nutritional programs, feeding higher levels of a specific AA to support desired functions such as intestinal recovery or immune function for birds experiencing an enteric stress still require further evaluation.

Dietary probiotics as a strategy for improving growth performance, intestinal efficacy, immunity, and antioxidant capacity of white Pekin ducks fed with different levels of CP

The potential impacts of probiotics on the performance and health status of white Pekin ducks fed with optimal or suboptimal dietary CP were evaluated during the growing period. A total of 180 male white Pekin ducks (14-day-old ducks with an initial weight of 415.65 ± 2.20 g) were randomly divided into 4 experimental groups (45 in each group of 5 replicates) in a 2 × 2 factorial design. The main factors included 2 dietary CP levels (18 or 14%) and dietary probiotic addition (with or without probiotics). The probiotic source was supplemented at 0.2 g per kilogram of diet from a blend of Lactobacillus acidophilus and Lactobacillus casei. The results showed that the diet containing 18% CP and probiotics significantly increases the final and total weight gain. Activities of intestinal enzymes (amylase, lipase, and protease), morphometrics (villus length, goblet cell count, and cryptal depth), and carcass percentage were also increased significantly. Total protein content, lysozyme activity, bactericidal activity, nitro blue tetrazolium levels, alternative complement pathway, superoxide dismutase activity, and catalase activity were significantly increased, whereas glucose, cortisol, and total cholesterol levels were decreased when treated with diet containing 18% CP and probiotics. Conversely, the group treated with diet containing 14% CP without probiotics showed the poorest performance, carcass properties, immune response, and antioxidant potential. In conclusion, probiotic addition to the 14% CP diet improved the performance of white Pekin ducks caused by reduced CP diet to performance due to the 18% CP diet without probiotic supplementation.

Effects of dietary amino acid density and feed allocation during the starter period on 41 days of age growth performance and processing characteristics of broiler chickens given coccidiosis vaccination at hatch1

A study was conducted to determine if increasing digestible (dig) amino acid (AA) density or feed allocation of starter diets fed to broilers receiving coccidiosis vaccination can ameliorate poor cumulative growth performance and reduce meat yield. A total of 1,600 Yield Plus Ross × Ross 708 male broilers were assigned to a 2 × 3 factorial arrangement of dig AA density [moderate (1.15% dig Lys) and high (1.25% dig Lys)] and feed allotment (0.45, 0.73, and 1.00 kg/bird) with 2 positive control treatments during the starter period. Diets were formulated to essential AA ratios relative to dig Lys. Vaccinated birds received a 1x dosage of Coccivac- B52 prior to placement, whereas non-vaccinated birds in the positive control groups were fed diets containing diclazuril. Following consumption of the starter diets, birds were provided common grower and finisher diets. Broilers fed the high AA density diet during the starter period had higher cumulative BW gain and lower cumulative feed conversion ratios (P < 0.05) than those fed the moderate AA density diet. Broilers fed the high AA density diet had heavier (P ≤ 0.005) carcass and total breast weights than birds fed the moderate AA density diet. Broilers fed a starter allotment of 1.00 kg/bird produced heavier carcass weights (P ≤ 0.006) than did birds provided lower allotments. Additionally, broilers fed the high AA density diet had a greater percentage of 0 scores (P = 0.005) for the upper intestinal region during scoring. Results from this study indicated that feeding the high AA density diet at higher feed allotments during the starter period resulted in increased AA intake, which supported the bird through the vaccine challenge and enhanced the cumulative growth and meat yield.

The sub-inhibitory theory for antibiotic growth promoters

Antibiotics have played a critical role in the prevention, control, and treatment of bacterial diseases in humans and animals, and as growth promoters (AGPs) when used at sub-therapeutic concentrations in animal production. Numerous hypotheses have been proposed for the effectiveness of AGPs, which have largely centered on the beneficial modulation of the intestinal microbiota. However, these hypotheses have been doubted by some researchers, as AGPs are fed at concentrations that would typically be below minimum inhibitory concentrations (sub-MIC) for the antibiotic used. More recently, pro-inflammatory immune responses have been associated with poor growth performance, and this, along with reported direct, anti-inflammatory effects of some antibiotics, have led to suggestions that reducing the nutrient cost of (intestinal) inflammation may explain the growth promoting or permitting effect of AGPs. However, doubts about antibacterial effects of AGPs, and the search for alternative explanations, overlook the sub-MIC effects of antibiotics. This paper summarizes some of the reported sub-MIC effects of antibiotics and considers these in the context of helping to explain the mode of action of AGPs and effects seen in studies in vivo. This leads to suggestions for the features that alternatives to AGPs could exhibit to achieve similar performance efficacy as AGPs.