Effects of nutrient restriction followed by realimentation on growth, visceral organ mass, cellularity, and jejunal morphology in lambs

• Restriction of protein, energy or both, retards the growth performance of lambs.
• Nutrition restriction decreases cell cellularity and jejunal morphometry of lambs.
• Protein or energy restricted lambs achieve compensatory growth after realimentation.
• Retard growth of protein and energy restricted lambs is evident after realimentation.
• Cellularity of protein and energy restricted lambs is recovered after realimentation.

Effects of nutrient restriction and realimentation on growth, cellularity of visceral organs and jejunal morphology in lambs were investigated. Forty Wu Zhu Mu Qin lambs were divided into control group (CG), moderately protein-restricted group (PR), moderately energy-restricted group (ER) or severely protein- and energy-restricted group (PER). The experiment included an adaptation period (0–30 days), nutritional restriction period (31–90 days), and realimentation period (91–180 days). Weight of lambs was measured weekly. Four lambs of each group were slaughtered at 90 days and 180 days. After slaughter, visceral organs were weighed, and subsamples were obtained to evaluate visceral DNA and protein contents, and jejunal morphology. Final body weight (BW), dry matter intake (DMI) and average daily gain (ADG) of lambs in PR, ER and PER were significantly less (P<0.01) than those of CG lambs during the restriction period. On d 180, no significant difference was observed for BW among PR, ER and CG, however, BW of lambs in PER was still less (P<0.01) than that of CG, PR and ER; ADG of nutrition restricted lambs was significantly greater than (P<0.01) that of CG. Visceral organ weight, on wet tissue basis, decreased with nutrition restriction (P<0.05); there was no difference (P>0.05) of visceral organ weights among treatments on d 180. As compared with CG, PR had decreased DNA concentration of the liver (P<0.05), DNA and protein concentration of the pancreas (P<0.05), protein concentration and protein:DNA of kidney and omasum (P<0.05) on d 90; ER had decreased DNA concentration of the heart (P<0.05); and PER had decreased DNA concentration of the liver (P<0.01). Intestinal cellularity was not affected by treatment on d 90. Except for DNA concentration of the duodenum of lambs in ER, and DNA concentration of the jejunum of lambs in PR and ER, no significant differences were observed among treatments in cellularity of visceral organs on d 180. Compared with CG, crypt depth and muscle thickness of the jejunum were decreased (P<0.01) in lambs of PR, ER and PER on d 90. Villus height, crypt depth, muscle thickness and mucosa thickness of lambs in PR and ER were similar to CG lambs on d 180. Results indicate that nutritional restriction of 60 days can retard the growth, cellularity of visceral organs and jejunal morphological development of lambs, and retarded cellularity achieves complete compensatory growth after realimentation of 90 days.