Effects of early growth rate and fat soluble vitamins on glucose tolerance, feed transit time, certain liver and pancreas related parameters and their share in intra-flock variation in performance indices in broiler chicken

Assessing the impact of hatching system and body weight on the growth performance, caecal short-chain fatty acids, and microbiota composition and functionality in broilers

BACKGROUND

Variations in body weight (BW) remain a significant challenge within broiler flocks, despite uniform management practices. Chicken growth traits are influenced by gut microbiota, which are in turn shaped by early-life events like different hatching environments and timing of first feeding. Chicks hatched in hatcheries (HH) experience prolonged feed deprivation, which could adversely impact early microbiota colonization. Conversely, hatching on-farm (HOF) allows early feeding, potentially fostering a more favorable gut environment for beneficial microbial establishment. This study investigates whether BW differences among broilers are linked to the disparities in gut microbiota characteristics and whether hatching systems (HS) impact the initial microbial colonization of broilers differing in BW, which in turn affects their growth patterns. Male Ross-308 chicks, either hatched in a hatchery or on-farm, were categorized into low (LBW) and high (HBW) BW groups on day 7, making a two-factorial design (HS × BW). Production parameters were recorded periodically. On days 7, 14, and 38, cecal volatile fatty acid (VFA) and microbiota composition and function (using 16 S rRNA gene sequencing and PICRUSt2) were examined.

RESULTS

HOF chicks had higher day 1 BW, but HH chicks caught up within first week, with no further HS-related performance differences. The HBW chicks remained heavier attributed to higher feed intake rather than improved feed efficiency. HBW group had higher acetate concentration on day 14, while LBW group exhibited higher isocaproate on day 7 and isobutyrate on days 14 and 38. Microbiota analyses revealed diversity and composition were primarily influenced by BW than by HS, with HS having minimal impact on BW-related microbiota. The HBW group on various growth stages was enriched in VFA-producing bacteria like unclassified Lachnospiraceae, Alistipes and Faecalibacterium, while the LBW group had higher abundances of Lactobacillus, Akkermansia and Escherichia-Shigella. HBW microbiota presented higher predicted functional potential compared to the LBW group, with early colonizers exhibiting greater metabolic activity than late colonizers.

CONCLUSIONS

Despite differences in hatching conditions, the effects of HS on broiler performance were transient, and barely impacting BW-related microbiota. BW variations among broilers are likely linked to differences in feed intake, VFA profiles, and distinct microbiota compositions and functions.

Impact of early posthatch feeding on the immune system and selected hematological, biochemical, and hormonal parameters in broiler chickens

Under commercial conditions, chicks hatch within a 24 to 48 h window, a period known as the hatching window. Subsequently, they undergo various treatments before finally being transported to the broiler farm. These procedures may delay the chicks' access to food and water, sometimes receiving them as late as 72 h after hatching. Previous studies have indicated that fasting during this initial period is detrimental, leading to impaired body growth, compromised immune system response, and hindered muscle development. The objective of this study was to assess the impact of early posthatch feeding on immune system organs and selected hematological, biochemical, and hormonal parameters. The experiment utilized Ross 308 broiler eggs incubated under typical commercial hatchery conditions. The experimental group's eggs were hatched in HatchCare hatchers (HC) with immediate access to feed and water, while the control group's eggs were hatched under standard conditions (ST). Thirty chickens from each group were assessed on the 1st (D1), 7th (D7), 21st (D21), and 35th (D35) day after hatching. On D1, the HC group exhibited lower hemoglobin, hematocrit, and total serum protein values, suggesting that early access to water prevents initial dehydration in newborn chicks. Conversely, the ST group showed a stress reaction on D1 due to feed deprivation, leading to an almost 2-fold higher serum corticosterone concentration compared to the HC group. However, this increase did not result in a significant change in the heterophil/lymphocyte ratio. Furthermore, the HC group displayed an increase in triglyceride concentration and a decrease in HDL concentration on D1. On D7, the HC group exhibited an increased relative weight of the bursa and a higher CD4+ cell number in the cecal tonsil (CT), indicating a more rapid development of these organs resulting from early stimulation of the gastrointestinal tract. However, early feeding did not influence the numbers of Bu-1+, CD4+, and CD8+ cells or the germinal center (GC) areas in the spleen. In conclusion, early feeding contributes to the welfare of newborn chicks by reducing dehydration and stress levels and stimulating the development of gut-associated lymphoid tissue.