An experiment was conducted to examine the effect of the nursery feeding program on subsequent growth performance, carcass quality, meat quality, and physical and chemical body composition of growing-finishing pigs. Four dietary treatments were used in a 2 × 2 factorial arrangement of treatments based on diet complexity (Complex vs. Simple) and in-feed antibiotics (2,730 [+AB] vs. 0 [-AB] mg of chlortetracycline /kg].A total of 552 pigs, in 5 blocks, were weaned at 21 ± 2 d of age with an initial BW of 7.03 ± 0.07 kg. Each experimental block had 3 pens per treatment, with 8 pigs per pen in blocks 1 and 2, and 10 pigs per pen in the remaining 3 blocks. Nursery diets were fed in a 3-phase feeding program (Phase I, II, and III diets fed for 1, 2, and 3 wk, respectively). All pigs were fed common grower-finisher diets thereafter. Six pigs per treatment were slaughtered for chemical body composition analysis at wk 2, 8, 12, and 17 postweaning. An additional 11 pigs per treatment were slaughtered at wk 17 postweaning (approximately 115 kg BW or market weight) for analysis of carcass characteristics, chemical and physical body composition, and meat quality. During the nursery phase, ADG was lower (P < 0.05) for pigs fed the Simple diet than those fed the Complex diet (491 vs. 528 g/d). Antibiotic usage improved (P < 0.05) ADG in Phases II (408 vs. 438 g/d) and III (689 vs. 720 g/d). In Phase I and II, G:F was lower (P < 0.05) for pigs fed the Simple diet than those fed the Complex diet (0.46 vs. 0.58 and 0.75 vs. 0.78 in Phases I and II, respectively). During the grower phase, pigs previously fed -AB diets grew faster than pigs fed +AB diets (P < 0.05; 1,009 vs. 971 g/d). There were no treatment effects on overall ADG or G:F from weaning to finishing. Nursery feeding program did not affect carcass quality characteristics. However, pigs previously fed +AB diets tended (P = 0.07) to have increased LM depth. Nursery feeding program had no effect on objective or subjective meat quality measures, chemical body composition, or the weight of primal and retail carcass cuts at wk 17 postweaning, with the exception of primal belly weight. These results indicate that feeding simple nursery diets, or nursery diets without antibiotics, compromises growth performance during the nursery period but does not affect overall growth performance between weaning and market BW, carcass characteristics, and meat quality. Thus, feed costs for nursery pigs can be reduced by feeding simple diets without compromising market BW and carcass and meat quality.

We have previously demonstrated that feeding low complexity diets (LOW) compromises growth performance of pigs during the first 3 wk after weaning and induces compensatory growth and improved feed efficiency thereafter. A study was undertaken to explore physiological mechanisms involved in compensatory growth following a nutritional insult. Fifty-six pigs were weaned at 21 ± 2 d of age and fed high complexity diets (HIGH) for 6 wk. All pigs received the same grower diet thereafter. Pigs were killed at weeks 2, 4, and 8 after weaning and proximal jejunum and distal ileum were sampled for evaluation of histology and enzyme activity. In the proximal jejunum, villus height was lower (P = 0.03) at week 2 in pigs on LOW than HIGH but not different at week 4. There was no effect of diet on crypt depth; villus height:crypt depth ratio increased (P = 0.02) from week 2 to week 4 in pigs on LOW but was not changed in pigs on HIGH. Diet did not impact gut morphology at the distal ileum. Enzyme activity was lowest (P < 0.05) at week 2 for sucrase and aminopeptidase N (APN) and lowest (P < 0.06) at week 8 for lactase. Sucrase activity was numerically higher at week 4 in pigs fed LOW but numerically higher at week 8 in pigs fed HIGH. Lactase and APN activity were not affected by diet. Compensatory growth observed in pigs following a nutritional insult after weaning may be due in part to improved digestive capability.

Forty pigs were used to evaluate the long‐term effect of nutritional insult on measures of intestinal development in weanling pigs. Pigs were weaned at 21±2 days of age and fed diets ad libitum containing either high (H) or low (L) quality protein sources for 6 wks. Growth performance was monitored weekly. Pigs were killed at wk 2 and 4. Sections of proximal jejunum and distal ileum were taken for histology and ileal digesta was sampled. Pigs on L had lower (P = 0.002) daily gain in wks 1–3 but not different in wks 4–6 compared to H pigs. Similarly, feed efficiency in pigs on L was lower (P< 0.05) during wks 2–3 but not different in wks 4–6. In the proximal jejunum, villus height was lower (P = 0.03) at wk 2 in pigs on L (356 vs 427 μm) but not different at wk 4 (527 vs 492 μm). There was no difference in crypt depth but villus height:crypt depth ratio increased (P = 0.04) from wk 2 to wk 4 (1.7 vs 2.2) in pigs on L and did not change in pigs on H (2.3 vs 2.5). Pigs on H tended to have a greater (P < 0.17) proportion of proliferating cells in the jejunum at wk 2 and 4. In wk 2, digesta amine concentration was higher (P = 0.06) in pigs on L. Diet quality did not impact gut morphology or cell proliferation at the distal ileum. Low quality protein sources reduced overall growth performance in weanling pigs but the negative effect of protein quality on gut morphology was transient. Recovery in feed utilization in pigs on L was likely due to rapid recovery of intestinal function.