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Simple Summary: There is a distinct possibility that synthetic and crystalline, or non-bound, amino acids will partially replace soybean meal in diets for broiler chickens and reduce the dependency of the chicken-meat industry on soybean meal as its principal source of protein.The genesis of this partial replacement will be the successful development of reduced-crude protein diets. A reduced-crude protein diet contains less soybean meal, and therefore less crude protein, but an increased array of essential and even non-essential non-bound amino acids so that requirements are met. There are, however, several challenges to be overcome if reduced-crude protein diets are to be successfully developed and adopted.Abstract: This review explores the premise that non-bound (synthetic and crystalline) amino acids are alternatives to soybean meal, the dominant source of protein, in diets for broiler chickens. Non-bound essential and non-essential amino acids can partially replace soybean meal so that requirements are still met but dietary crude protein levels are reduced. This review considers the production of non-bound amino acids, soybeans, and soybean meal and discusses the concept of reduced-crude protein diets. There is a focus on specific amino acids, including glycine, serine, threonine, and branched-chain amino acids, because they may be pivotal to the successful development of reduced-crude protein diets. Presently, moderate dietary crude protein reductions of approximately 30 g/kg are feasible, but more radical reductions compromise broiler performance. In theory, an 'ideal' amino acid profile would prevent this, but this is not necessarily the case in practice. The dependence of the chicken-meat industry on soybean meal will be halved if crude protein reductions in the order of 50 g/kg are attained without compromising the growth performance of broiler chickens. In this event, synthetic and crystalline, or non-bound, amino acids will become viable alternatives to soybean meal in chicken-meat production.Animals 2020, 10, 729 2 of 20 generates 1.1 kg CO 2 equivalents, which is considerably less than that of pork (3.8 kg CO 2 equivalents) or beef (14.8 kg CO 2 equivalents) production [2]. Moreover, it has been predicted that chicken-meat production will contribute 7.1% of greenhouse gas emissions compared to 29.8% and 63.1% for pork and beef, respectively [2]. However, diets for broiler chickens may contain more than 200 g/kg protein, the majority of which is derived from soybean meal; consequently, the chicken-meat industry has a huge demand for soybean meal. The production of 1 kg of chicken meat will require an input in the order of 560 g soybean meal given a conservative 250 g/kg dietary inclusion of soybean meal and a 2.25:1 conversion of feed into carcass weight. Importantly, this demand can be diminished by inclusions of non-bound (synthetic and crystalline) amino acids in broiler diets at the expense of soybean meal via the successful development of reduced-crude protein (CP) diets [3]. Therefore, synthetic...

The objective of this study was to evaluate the effects of the dietary supplementation of Bacillus subtilis DSM 32315 (probiotic) on the performance and intestinal microbiota of broiler chickens infected with Clostridium perfringens (CP). One-day-old broiler chickens were assigned to 3 treatments with 8 replicate pens (50 birds/pen). The treatments were: non-infected control; infected control; and infected supplemented with probiotic (1 × 106 CFU/g of feed). On day of hatch, all birds were sprayed with a coccidia vaccine based on the manufacturer recommended dosage. On d 18–20 the infected birds were inoculated with CP via feed. Necrotic enteritis (NE) lesion score was performed on d 21. Digestive tract of 2 birds/pen was collected on d 21 to analyze the ileal and cecal microbiota by 16S rRNA sequencing. Performance was evaluated on d 28 and 42. On d 21, probiotic supplementation reduced (p < 0.001) the severity of NE related lesion versus infected control birds. On d 28, feed efficiency was improved (p < 0.001) in birds supplemented with probiotic versus infected control birds. On d 42, body weight gain (BW gain) and feed conversion ratio (FCR) were improved (p < 0.001) in probiotic supplemented birds versus infected control birds. The diversity, composition and predictive function of the intestinal microbial digesta changed with the infection but the supplementation of probiotic reduced these variations. Therefore, dietary supplementation of Bacillus subtilis DSM 32315 was beneficial in attenuating the negative effects of CP challenge on the performance and intestinal microbiota of broilers chickens.

A study was conducted to investigate the effects of Bacillus amyloliquefaciens CECT 5940 as a direct-fed microbial (DFM) alone or in association with bacitracin methylene disalicylate (BMD) in broilers under enteric pathogen challenge. A total of 1,530-day-old male Cobb500 chicks were randomly assigned to 5 treatments, with 9 replicate pens with 34 birds each. Treatments included positive control (PC, basal diet without additives or challenge); negative control (NC, basal diet without additive and challenged birds); NC + 0.05 g/kg BMD; NC + 1 g/kg DFM (106 CFU B. amyloliquefaciens CECT 5940/g of feed); and NC + 0.05 g/kg BMD + 1 g/kg DFM. The challenge consisted of oral gavage with Eimeria maxima and Clostridium perfringens inoculum. Body weight gain (BWG), feed intake (FI), and feed conversion ratio (FCR) were evaluated on days 21, 35, and 42. Ileal and cecal content were collected on days 21 and 28 for C. perfringens enumeration by real-time PCR assay and the intestinal health was evaluated by scores. Uniformity (UN), carcass (CY), and breast meat yields (BMY) were evaluated on day 42. After 14 and 21 d post-inoculation, birds in the challenged groups had significant lower FI and BWG compared to the PC group (P < 0.05). However, the groups receiving DFM, BMD, or its combination presented better FCR, CY, BMY, UN, and lower incidence of footpad lesion and litter quality visual scores, compared to the NC group without feed additives (P < 0.05). Mortality was not affected by treatments (P > 0.05). Broilers fed DFM, BMD, or its combination presented lower C. perfringens in ileal content at 21 and 28 d compared to NC group without additives (P < 0.05) and also maintained gut health by keeping the frequency of ballooning, abnormal content, and swollen mucosa comparable to the PC group (P > 0.05). The study indicates that Bacillus amyloliquefaciens CECT 5940 is effective as BMD to provide similar performance and gut health in challenged broilers.

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