Abstract
The digestive tract development in goat kids around weaning is vital to the establishment of digestion and absorption function, growth, and health of adults. The objective was to explore the effects of age and solid feed on the anatomical and morphological development of the gastrointestinal tract of Laiwu Black goat kids. Forty-eight female Laiwu Black goats at 8 ages (1, 7, 14, 28, 42, 56, 70, and 84 d; 6 goats per group) were selected and killed for anatomical and morphological analysis. The goats experienced the following 4 diet phases: maternal colostrum (MC; d 1, d 7), maternal milk (MM; d 14, d 28), maternal milk plus solid diet (MMSD; d 42, d 56) and only solid diet (OSD; d 70, d 84). The body and carcass weights were not significantly changed during MC and MM phases but changed during the MMSD phase. The absolute growth of body and carcass weights were higher in the MMSD phase than in MM phase. In addition, the dressing percentage was the highest in the MMSD phase. The body size indices evolved progressively and increased over time. The percentage of internal and external organs to body weight decreased over time, whereas the percentage to complex stomach percentage increased. The rumen and omasum weight experienced synchronous absolute growth over time, especially in the OSD phase. In contrast, the absolute growth of the reticulum and abomasum was the highest in MMSD and MC phases, respectively. After weaning, the goats showed the highest papillae height, lamina propria, muscle layer thickness, and epithelial thickness. The OSD phase showed the highest colonic mucosa thickness, ileal villus height, and ileal muscle layer thickness. The crypt depth was higher in the MMSD phase than in the MM phase. Moreover, the crypt depth and muscle layer thickness of jejunum increased over time. Furthermore, duodenal crypt depth, muscle layer thickness, and epithelial thickness increased in the OSD phase compared with other stages. In conclusion, the histological investigation supports the improvement of the morphological development of the digestive tract and the growth performance in the solid feed phase. It is recommended to add solid food as early as 4 wk old.
Highlights
Goats (Capra hircus) are a global livestock species because they provide essential products, such as milk, meat, and skin (Wang et al, 2021)
The improvement of body size indices was slow in the milk phase, whereas it was remarkable in the maternal milk plus solid diet (MMSD) phase
The absolute growth of carcass and the dressing percentage was lower at the post- than the preweaning stage, indicating weaning stress
Summary
Goats (Capra hircus) are a global livestock species because they provide essential products, such as milk, meat, and skin (Wang et al, 2021). The rapid economic growth increased the demand for improving the quality and productivity of goats. The digestive tract development in goat kids has a long-term effect on the establishment of digestion and absorption function, production performance, and health status (Jiao et al, 2016; Diao et al, 2019). It is vital to master the rules of anatomical and morphological development of the gastrointestinal tract to tap the growth potential of goats and promote industrial development (Jin et al, 2018). The knowledge about the longitudinal effects of gastrointestinal physiology, especially in the transition weaning stage, could be helpful to increase our understanding of the anatomical and morphological development of the digestive tract to control stress after weaning, to avoid challenges in livestock production
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