Effect Of Weaning Age On The Growth Performance And Development Of The Gastrointestinal Tract In Lambs

This research was conducted to investigate the effects of weaning age on the growth performance and development of the gastrointestinal tract in lambs for assessing the best weaning age and providing the scientific basis of lamb fostering. Body weight, average daily gain and creep feed intake were determined to study the effects of weaning age on growth performance of lambs. Nutrient digestion and metabolism were measured to estimate the apparent digestibility within 10, 50-60 and 80-90 days of post-weaning. The serological indicators were detected using the methods of full automatic biochemical analys is and radioactive immunity test. The development of tissue, organs, alimentary canal and meat quality were researched to investigate the lambs’ body development by the slaughter method. Rumen fermentation parameters were study, and the variation of rumen microorganism community was evaluated by using the high-throughput sequencing. The present research included 3 trails which were described as follows. Experiment 1: Effect of weaning age on growth performance, nutrient digestion and metabolism and serum parameters in lambsThis experiment was aimed to study the effect of weaning age on growth performance, nutrient digestion and metabolism and the serum parameters in lambs. Seventy-two newly born Hu lambs(birth weight, 2.53±0.14kg; 24 males and 24 females), were randomly divided into four groups. The lambs in control group(ER) with 6 replicates and 4 lambs per replicate were suckled by their dams until d 60. The early-weaned lambs in three experimental groups were respectively weaned at 10, 20, or 30 days(EW10, EW20, and EW30) post birth and each group with 4 replicates and 4 lambs per replicate contain 16 lambs. The early weaned lambs were fed a milk replacer artificially until d 60. All lambs were supplement creep feed ad libitum from d 15 to d 90. The lambs were weighed every 10 days before morning feeding. Four lambs of the experimental groups were selected to conduct the digestibility test at post-weaned 10 days, d 50-60 and d 80-90. At the same time, ER group was conduct as a control. Blood samples were collected at 10, 20, 30, 40 and 90 days of age prior to morning feeding. The results showed that early weaning lambs, especially EW10 group, had heavier(P<0.05) body weight(BW) than ER lambs at d 90. In the whole period, the average daily gain( ADG) of early-weaned lambs in EW10, EW20 and EW30 was respectively increased 39.55%、31.78% and 19.44% compared with ER group and EW10 had a greater(P<0.05) ADG than that in ER group. The BW of early-weaning lambs was decreased within 10 days of post-weaned and EW30 group had a lower(P<0.05) BW compared with ER, and the ADG of EW10 and EW30 was reduced(P<0.05) at the same age. During the period of 10-20 days after weaning, EW10, EW20 and EW30 had a similar(P>0.05) ADG to ER group. After 20 days after weaning, the ADG of weaned lambs had a higher(P<0.05) value than ER groups, and BW of weaned lambs was high(P<0.05) than that in ER. The creep feed intake was improved by early-weaning and feeding the milk replacer, thus EW10, EW20 and EW30 group had a higher creep feed intake(P<0.05) than that in ER group and EW10 had a higher value(P<0.05) than EW20 and EW30 group. In nutrient utilization, the nutrient apparent digestibility and deposition in experimental group were decreased(P<0.05) within 10 days of post-weaning; the nutrient metabolism had no difference(P>0.05) among groups during d 50-60; EW20 and EW30 were high than ER and EW10 in the apparently digestion of DM, OM, GE and N during d 80-90. At the d 10 of post-weaned, serum concentration of total protein(TP), albumin(ALB), globulin(GLB), total cholesterol(CHO), triglyceride(TG), non-esterified fatty acid(NEFA), growth hormone(GH), insulin-like Growth Factor Ⅰ(IGF-Ⅰ)and alkaline phosphatase(ALP) in EW30 group had a lower(P<0.05) concentration than those in ER group, and serum immunoglobulin A(Ig A), immunoglobulin G(Ig G), immunoglobulin M(Ig M), cortisol(CORT), creatine phosphate kinase(CK) and lactic dehydrogenase(LDH) were higher in EW10 and EW30 group than those in ER group. Experiment 2: Effect of weaning age on rumen fermentation and microorganism community in lambsThis trial investigated the effect of weaning age on rumen fermentation and microorganism community in lambs. The experiment design and animals were the same as Experiment 1. The early-weaning lambs were selected 4 lambs at 10 days of post-weaned and d 90 to collect the rumen fluid and ER group was conducted at the same day as a control, which was used to measure rumen fermentation parameters, diversity and community of microorganism. The results were as follows. EW10 and EW30 had no difference with ER group in rumen fermentation parameters at d 20 and d 40 respectively. EW20 group had a low er(P<0.05) p H, isobutyrte, isovalerate and the ratio of acetate and propionate than those in ER group at d 30, while it had a higher(P<0.05) level of NH3-N and propionate compared with ER. At the end of the experiment, the NH3-N concentration of EW20 and EW30 was higher(P<0.05) than that in EW10 and ER; EW10 had a higher butyrate than EW20, EW30 and ER(P<0.05) and EW20 was higher(P<0.05) than EW30 and ER. According the high-throughput sequencing result, at the 10 th d after weaning, the index of shannon and simpson in EW20 group were higher(P<0.05) than that in ER group, shannon index of EW30 group was higher(P<0.05) than that in ER group, and the chao1 and ACE index in early-weaned lambs was high than ER lambs but no different at the same days of age; at d 90, the microorganism diversity was no difference between 4 groups, however, the chao1, ACE and PD_whole_tree index in ear ly-weaned lambs was higher than ER lambs. Experiment 3: Effect of weaning age on the development of tissues, organs and the gastrointestinal tract, and meat quality in lambsThis trial was aimed to investigate the effect of weaning age on the development of tissues, organs the gastrointestinal tract and meat quality in lambs. The experiment design and animals were the same as Experiment 1.Four lambs(2 males and 2 females) were selected and slaughtered at 10 days of post-weaned and d 90 to slaughter and ER group was conducted at the same day as a control, which was used to measure the weight of tissues, organs, alimentary canal and the slaughter performance and meat quality. At 10 th day after weaning, the EW10, EW20 and EW30 groups were no difference(P>0.05) in organ proportion of lambs compared with ER group. At d 90, there had no different(P>0.05) between 4 groups in the weight of head, skin and wool; weight of visceral organs had no difference(P>0.05) among 4 groups. In the aspect of development of gastrointestinal tract, EW10 group had a greater value(P<0.05) in the ratio of rumen weight and whole stomach weight than ER group at d 10 of post-weaning; at d 90, the rumen weight EW10, EW20 and EW30 groups(593.13, 593.38 and 579.08g) was higher(P<0.05) than in ER group(428.98g), meanwhile the percentage of the weight of the rumen and whole stomach in EW20 and EW30 groups was higher(P<0.05) than that in EW10 and ER groups. The live body weight before slaughter, empty body weigh and carcass weight of EW10, EW20 and EW30 was higher(P<0.05) than those in ER group. The longissimus thoracis of early-weaned lambs had a higher(P<0.05) L*, b*, and ether extract content than ER lambs. The proportion of unsaturated fatty acid and polyunsaturated fatty acid in the longissimus thoracis of EW10 and EW20 groups was higher(P<0.05) than that in ER group, while the content of saturated fatty acid in meat from EW10 and EW20 was lower(P<0.05) compared with ER group, and the composition of monounsaturated fatty acids was no difference(P>0.05) among 4 groups. In the amino acid content of longissimus thoracis, EW10 had greater(P<0.05) leucine(Leu) content than other groups and the profiles of alanine( Ala) and proline(Pro) in EW10, EW20 and EW30 groups was higher(P<0.05) compared with ER group.In conclusion, early weaning improved the creep feed intake and nutrient digestibility in lambs, increased rumen fermentation function, promoted the development of alimentary canal and then improved the growth performance and meat quality. In addition, taken into account the minimum weaning stress, growth performance, nutrient utilization and rumen development, the 20 days after birth was the best weaning age for lambs.