This experiment was conducted to investigate the effects of different dietary energy levels on growth performance, slaughter traits, meat quality and blood biochemical parameters in fattening male Hu lambs. Sixty lambs were fed five iso‐protein diets which contained different levels of metabolizable energy in a completely randomized design for 70 days. At the end of study, fifteen lambs were harvested for further study. With the increase in dietary energy level, the daily weight gain and dry matter intake extremely increased (p < .001), and feed conversion ratio decreased significantly (p < .01). The live weight before slaughter (LWBS) and carcass weight had a significant increase (p < .05), non‐carcass fat ratio and routine indexes of meat quality had no significant difference. Almost no effect was observed for the amino acid profile except for glycine concentration decreased (p < .05) in longissimus dorsi (LD) muscle. The concentrations of C17:0, C18:3n‐3 and n‐3 PUFA (p < .01) significantly decreased with the increasing dietary energy levels, and the ratio of ∑n‐6/∑n‐3 (p < .01) increased, whereas the concentrations of C18:1n‐9t (p < .05) decreased in LD muscle and C18:1 (p < .01) increased in biceps femoris (BF) muscle. There were no obviously differences for diameter, area and density of muscle fibres. The relative expression of MyHC‐IIa and MyHC‐IIx decreased significantly (p < .05) in BF muscle, and the relative expression of MyHC‐IIa displayed an obviously decreasing trend (p < .10) in LD muscle. These results suggest that increasing the dietary energy level can improve the growth performance and slaughter traits, and influence meat quality and fatty acid profiles in different muscle tissues of fattening male Hu lambs. These results provide a theoretical basis for developing Hu sheep nutritional standards and designing feed formulations.

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This study evaluated the effects of dietary energy levels on growth performance, carcass traits, meat quality, and serum biochemical of female Hu lambs. Seventy female Hu lambs (aged 4 months) were randomly allotted to 5 dietary treatments. Lambs were fed diets with 5 levels of metabolizable energy (ME): 9.17 (E1), 9.59 (E2), 10.00 (E3), 10.41 (E4), and 10.82 MJ/kg (E5). The lambs were adapted to the experimental diets for 10 d and the experiment period lasted for 60 d. Dry matter intake and feed conversion ratio linearly ( P < 0.001) increased and decreased ( P < 0.001), respectively, with increasing dietary ME levels. Average daily gain (ADG) linearly ( P < 0.001) increased with increasing dietary ME levels, with the highest final body weight ( P = 0.041) observed in E4 group. Moreover, dietary energy level was associated with linear increases in serum total protein (TP) ( P < 0.001), albumin (ALB) ( P = 0.017), glucose (GLU) ( P = 0.004), and low-density lipoprotein cholesterol (LDLC) ( P = 0.006) concentrations, and it was associated with a quadratic decrease in serum triglyceride (TG) concentration ( P = 0.002). Serum ammonia concentration, which was firstly decreased and then increased, was quadratically affected by dietary ME levels ( P = 0.013). Compared with E1 group, lambs in E4 group had higher ( P < 0.05) live weights, carcass weights, mesenteric fat ratio, non-carcass fat ratio, and larger loin muscle area, but lower ( P < 0.05) meat colour a∗ and b∗ values, and lesser ( P < 0.05) C17:0, C20:0, C18:1n-9t, C18:3n-3, and n-3 polyunsaturated fatty acids (PUFA), but greater ( P < 0.05) C18:3n-6 and n-6:n-3 ratios in longissimus dorsi (LD) muscle tissue, and lesser ( P < 0.05) C17:0, C18:3n-3, C22:6n-3, and n-3 PUFA in the biceps femoris (BF) muscle tissue. The results demonstrated that increasing dietary energy level improved the growth performance and affected carcass traits, serum biochemical indexes, and fatty acid profiles in different muscles of female Hu lambs. For 4-month-old female Hu lambs, the recommended fattening energy level is 10.41 MJ/kg.

This study investigated rumen fermentation and histological and microbial diversity in male Hu lamb fed diets with different metabolizable energy (ME) levels (MEA, 9.17 MJ/kg, MEB, 10.00 MJ/kg, and MEC, 10.82 MJ/kg). Thirty-six male Hu lambs were randomly allotted to three treatments, and the feeding trial lasted for 67 days. Rumen fermentation results suggest that the iso-valerate had a significant effect on dietary energy level. The papillary height (PH) of rumen was the highest in the MEB group, the crypt depth (CD) was significantly increased in the duodenum and jejunum, and the villus height (VH)-to-CD ratio (VH/CD) was significantly decreased in the duodenum by increasing dietary energy levels; the VH, villus width (VW), and VH/CD also had significant differences in the ileum. 16S rRNA sequencing results showed that the operational taxonomic units (OTUs) number, the ACE, and Chao1 indices were linearly decreased by increasing dietary energy level; 24 phyla including 124 genera were identified, and the relative abundance of Papillibacter and Quinella linearly decreased by increasing the dietary energy level. Compared to MEA and MEB groups, the relative abundance of unidentified_Veillonellaceae and Anaerovibrio was significantly increased in the MEC group at the genus level. The relative abundance of the carbohydrate metabolism pathway predicted by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was linearly increased by increasing the dietary energy levels. Three metabolic pathways identified in Kyoto Encyclopedia of Genes and Genomes (KEGG) level 3 were significantly influenced as the dietary energy level increased. In summary, these results demonstrated that the dietary energy levels affected the rumen fermentation parameters, morphological structures of the gastrointestinal tract (GIT), and the composition and function of rumen microflora in male Hu sheep.

The purpose of this study was to explore the effects of ewe growth performance, serum biochemical indicators and lamb growth and development at different protein levels in late pregnancy. A total of 15 pregnant ewes (46.4 ± 1.38kg initial BW) were assigned to 3 groups with 5 ewes in each group in a randomized block design. P1, P2 and P3 of three groups were fed diets with different levels of crude protein at 11.25%, 12.5% and 13.75% (low, medium and high) respectively, while the dietary energy levels remained unchanged. Choose ewes with the same body condition from 90 days of pregnancy to different protein diets during delivery, and feed the same diets during lactation. New-born lambs were left to suckle their dams freely for the first three days and were kept with their dams till weaning at 60 days of age. Dietary protein levels during late gestation showed no significant effect on the weight gain of ewes and their offspring in the late pregnancy (P > 0.05) but had significant effects on blood urea nitrogen (BUN), glucose (GLU), C-reactive protein (CRPL3) and ammonia nitrogen (NH3L) before parturition, and on triglyceride (TG) in lactating ewes. Dietary protein levels during late gestation had significant effects on birth height, body length, chest depth, chest circumference, straight crown hip length and curved crown hip length of lambs (P < 0.05) as well as on weaning body length, chest circumference, head width and head length (P < 0.05). The results showed that although different dietary protein levels during late gestation have no significant effects on growth performance of ewes, singleton, twins and triplets, it affects lambs' body shape and ewes' metabolism.Therefore, the optimum protein concentration for the growth of ewes and subsequent lambs in this experiment is 11.25%.