Broiler embryonic development depends on the nutrients that are available in the egg, which includes mostly water, lipids, and proteins. Carbohydrates represent less than 1%, and free glucose only 0.3%, of the total nutrients. Considering that energy requirements increase during incubation and metabolism is shifted toward the use of glycogen stores and gluconeogenesis from amino acids, extensive muscle protein degradation in the end of incubation can compromise chick development in the initial days after hatch. Significant prehatch changes occur in embryonic metabolism to parallel the rapid embryonic development. Oral consumption of the amniotic fluid begins around 17 d of incubation and promotes rapid development of the intestinal mucosa, which is characterized by morphological changes and increased expression and activity of enzymes and transporters. Furthermore, ingested substrates are stored as nutritional reserves to be used during hatching and in the first week after hatch. At hatch, this limited-nutrient store is directed to the functional development of the gastrointestinal tract to enable assimilation of exogenous nutrients. In ovo feeding is an alternative to deliver essential nutrients to chick embryos at this critical and challenging phase. The improved nutritional status and physiological changes triggered by in ovo feeding can resonate throughout the entire rearing period with significant health and economic gains. The present review addresses the main changes in metabolism and intestinal development throughout incubation, and also addresses scientific advances, limitations and future perspectives associated with the use of in ovo feeding that has been regarded as an important technology by the poultry industry.

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This study assessed the effect of both embryonic thermal manipulation and dietary threonine level on the response of broilers inoculated with Salmonella Enteritidis, considering bacterial counts in the cecal contents, intestinal morphology, mucin and heat shock protein 70 gene expression, body weight and weight gain. Thermal manipulation was used from 11 days of incubation until hatch, defining three treatments: standard (37.7°C), continuous high temperature (38.7°C) and continuous low temperature (36.7°C). After hatch, chicks were distributed according to a 3x2+1 factorial arrangement (three temperatures and two threonine levels and one sham-inoculated control). At two days of age, all chicks were inoculated with Salmonella Enteritidis, except for the sham-inoculated control group. There was no interaction between the factors on any analyses. High temperature during incubation was able to reduce colonization by Salmonella Enteritidis in the first days, reducing both Salmonella counts and the number of positive birds. It also increased mucin expression and decreased Hsp70 expression compared with other inoculated groups. High temperature during incubation and high threonine level act independently to reduce the negative effects associated to Salmonella Enteritidis infection on intestinal morphology and performance, with results similar to sham-inoculated birds. The findings open new perspectives for practical strategies towards the pre-harvest Salmonella control in the poultry industry.

This study assessed the effect of in ovo threonine supplementation on the response of broiler chicks challenged with Salmonella Enteritidis, considering bacterial counts in cecal contents, intestinal morphology, body weight, and weight gain. Fertilized eggs were inoculated in the amniotic fluid with saline (NT) or 3.5% threonine (T) solution at day 17.5 of incubation. At hatch, chicks were individually weighed and cloacal swabs were screened for Salmonella. At 2 days of age, half of the birds from each in ovo treatment were given either 0.5 mL of nutrient broth (sham-inoculated) or nalidixic acid-resistant Salmonella Enteritidis (SE NalR) in nutrient broth (8.3 × 107 colony forming units (CFU) SE NalR/mL). The birds were distributed using a completely randomized design with four treatments after the Salmonella challenge: no in ovo Thr supplementation and sham-inoculated in the posthatch challenge (NT-SHAM), in ovo Thr supplementation and sham-inoculated (T-SHAM), no in ovo Thr supplementation and SE NalR-challenged (NT-SE), and in ovo Thr supplementation and SE NalR-challenged (T-SE). In ovo threonine supplementation reduced Salmonella Enteritidis colonization 168-hour postinoculation and reduced the negative effects associated with Salmonella infection on intestinal morphology and performance, with results similar to those of the sham-inoculated birds. In ovo Thr supplementation increased the expression of MUC2 at hatch and the expression of MUC2 and IgA at 2 days of age and 168-hour postinoculation. Our results suggest that providing in ovo threonine promotes intestinal health in broilers challenged with Salmonella Enteritidis in the first days of life.

This trial was designed to evaluate the off-label use of ceftiofur with Marek’s vaccine in one-day-old broiler chicks, a prophylactic treatment that has been done in some commercial hatcheries, on the emergence of extended-spectrum beta-lactamase producing Escherichia coli (ESBL-E. coli). A total of 168 chicks (Cobb500®) were used in a completely randomized design. Birds were assigned to two treatments (Marek’s vaccine plus saline vs Marek’s vaccine plus ceftiofur) and six repetitions, with 14 animals each. Cloacal swabs were collected from 1 to 14 days post-hatch. The majority (86%; p<0.0001) of the ESBL-producing isolates harboring blaCTX-M and blaSHV genes originated from animals receiving the antimicrobial. None of the isolates were positive for plasmid-mediated AmpC betalactamase genes (blaACC, blaCMY-2, blaDHA, blaFOX, blaMOX and blaMIR). These findings indicate that the off-label use of ceftiofur with Marek’s vaccine is associated with the short-term increase in ESBL-producing Escherichia coli in the gut of chicks.