Ear differentiation, grain development and their interaction with factors in the growing environment, such as temperature, solar radiation and precipitation, greatly influence grain number and grain weight, and ultimately affect summer maize production.  In this study, field experiments involving different sowing dates were conducted over three years to evaluate the effects of temperature factors, average solar radiation and total precipitation on the growth process, ear differentiation, fertilization characteristics, grain filling and yield of summer maize varieties with different growth durations.  Four hybrids were evaluated in Huang-Huai-Hai Plain (HHHP), China from 2018 to 2020 with five different sowing dates.  The results showed that the grain yield formation of summer maize was strongly impacted by the environment from the silking (R1) to milking (R3) stage.  Average minimum temperature (AT_min) was the key environmental factor that determined yield.  Reductions in the length of the growing season (r=–0.556, P<0.01) and the total floret number on ear (R²=0.200, P<0.001) were found when AT_min was elevated from the emerging (VE) to R1 stage.  Both grain-filling rate (R²=0.520, P<0.001) and the floret abortion rate on ear (R²=0.437, P<0.001) showed quadratic relationships with AT_min from the R1 to physiological maturity (R6) stage, while the number of days after the R1 stage (r=–0.756, P<0.01) was negatively correlated with AT_min.  An increase in AT_min was beneficial for the promotion of yield when it did not exceeded a certain level (above 23°C during the R1–R3 stage and 20–21°C during the R1-R6 stage).  Enhanced solar radiation and precipitation during R1–R6 increased the grain-filling rate (R²=0.562, P<0.001 and R²=0.229, P<0.05, respectively).  Compared with short-season hybrids, full-season hybrids showed much greater suitability for a critical environment.  The coordinated regulation of AT_min, ear differentiation and grain development at the pre- and post-silking stages improved maize yield by increasing total floret number and grain-filling rate, and by reducing the floret abortion rate on ear. 

Fasting is typically used before feeding metabolizable energy assessment in broilers.  Previous studies have shown that fasting cause atrophy of the intestinal villus.  Whether fasting affects intestinal permeability during refeeding by altering barrier function and nutrient absorption is of concern.  Here, 23-d-old broilers were randomly assigned to 5 treatments, fasted for 0, 12, 24, 36, and 48 h, respectively, and then refed for 2 d, to study the impact of different duration of fasting on the intestinal regeneration and barrier function during refeeding.  Results showed that the intestinal morphology in fasted birds was recovered in 2 d of refeeding at most.  As fasting durations increased, enterocytes per intestinal villus were linearly and quadratically increased (both P<0.05), whereas goblet cells per intestinal villus was linearly decreased (both P<0.05).  Besides, the mRNA level of lysozyme was linearly decreased as fasting durations increased during refeeding (both P<0.05), while quadratically increased mucin 2 was observed only after 1 d of refeeding (P<0.05).  Linear increase effects were observed for claudin 2 and zonula occludens-1 with increased fasting durations after 1 d of refeeding (all P<0.05), and linear and quadratical effects were observed for claudin 2 at 2 d of refeeding (both P<0.05).  Besides, we found that intestinal permeability to creatinine, 4 and 70 kD dextran were linearly and quadratically decreased with increased fasting durations at 6 h and 1 d of refeeding (all P<0.05).  Furthermore, jejunum proteomic from birds refed for 6 h showed that birds fasted for 36 h showed increased antimicrobial peptides and upregulated retinol metabolism when compared to the nonfasted birds (P<0.05).  Further study showed that retinyl ester catabolism was inhibited during fasting and enhanced during refeeding.  Results of intestinal organoid culture showed that retinol benefits the cell proliferation and enterocyte differentiation.  In conclusion, the intestinal permeability to small and large molecules was decreased during refeeding by strengthening the intestinal barrier function, and the activated retinol metabolism during refeeding is involved in the intestinal regeneration and strengthens the intestinal barrier.