Comparative Study Of Performance,Rumen Fermentation And Blood Biochemical Indices Of Tibetan Sheep (Ovis Aries) And Goat Under Moist-Heat Stress

The present study was conducted to investigate the variation of the performance, rumen fermentation, blood biochemical indices and nutrient apparent digestibility of both Tibetan sheep with living in high altitude plateau and goats with living in lower plain in the same nutritional condition and moist-heat environment, aiming at revealing the different adaptations of the two breeds that living in different altitude. The paper consisted of two trials:Trial 1:The influence of moist-heat stress on performance and blood biochemistry indices of Tibetan sheep and goats.Six individuals of Tibetan sheep and goats were selected based on similar mean body weight (46.08±4.02kg and 45.58±3.37kg respectively), raised from April to September in 2015. The entire experimental operation period consisted of preliminary feeding period (15d) and formal feeding trial (150d). Temperature humidity index (THI) was measured daily. Body weight were measured and jugular blood samples were collected during the formal test. The result showed as follows:1) The THI of the barn in May was under 72, and THI were above 72 from June to September, the value of THI in September was lower than June to August (P<0.05). Respiratory frequency and rectal temperature of Tibetan sheep and goats were all significantly increased (P<0.05) with THI increased. Tibetan sheep had higher Respiratory frequency and rectal temperature (P<0.05), and the increased range as well.2) Dry matter intake (DMI) and average daily gain (ADG) of both Tibetan sheep and goats decreased (P<0.05) accompanied with increasing THI during whole experiment, while the feed-gain ratio all raised. The decreased extent of ADG of Tibetan sheep was much larger but feed-gain ratio presented a less increased range than that of goats (P<0.05).3) The concentrations of serum glucose (GLU) and non-esterified fatty acid (NEFA) were reduced significantly (P<0.05) in both Tibetan sheep and goats under moist-heat stress, while the triglyceride (TG) and BUN concentrations were increased (P<0.05).4) With the raising of THI, adrenocorticotropic hormone (ACTH) concentrations were first increased and then decreased in both sheep and goats (P<0.05), and cortisol (COR) concentrations were increased (P<0.05). ACTH amplification was higher in Tibetan sheep, while COR amplification was higher in goats than that of Tibetan sheep. Serum triiodothyronine (T3) and thyroxine (T4) concentrations were significantly decreased (P<0.05) with the increasing THI in both Tibetan sheep and goats. The reduction of T4 in Tibetan sheep was greater than that of goats but the converse result for T3 was observed. With the THI raised, growth hormone (GH) and insulin-like growth factors-1 (IGF-1) concentrations were all decreased (P<0.05) in both Tibetan sheep and goats, the decreased range of GH in Tibetan sheep were larger than that of goats.5) With the increasing THI, the serum Heat shock protein-70 (HSP-70) and malondialdehyde (MDA) concentrations were extremely significantly increased in both Tibetan sheep and goat (P<0.05), while the concentrations of superoxide dismutase (SOD), glutathione peroxidase (GSH-px) and T-AOC were significantly decreased (P<0.05). The decreased extent of SOD and T-AOC and the increased extent of MDA of goats were larger than those of Tibetan sheep. The concentration of IgA, IgM and IgG were significantly decreased (P<0.05), while the concentration of tumor necrosis factor-a (TNF-a) was increased (P<0.05) by moist-heat stress. The decreased extent of IgA, IgM and IgG and increased extent of TNF-a of Tibetan sheep were larger than those of goats.Trial 2:The effect of moist-heat stress on nutrient apparent digestibility, rumen environment and rumen bacteria of Tibetan sheep and goats.Four animals were chosen from each breed, and raised in metabolic cages. The ration and fecal samples were taken in non-stressed period (THI:67.24±0.25) and moist-heat stress period (THI:79.60±2.65), respectively. Nutrients apparent digestibility were investigated by endogenous indicator (Acid insoluble ash), and rumen fluid was taken by oral sampler to investigate rumen fermentation and microorganisms. The result shows as follows:1) Decreased apparent digestibility of the CP and NDF in both Tibetan sheep and goats were observed when they were suffered in moist-heat stress (P<0.05). The large decreasing proportion of NDF apparent digestibility in Tibetan sheep observed.2) Moist-heat stress significantly increased the rumen pH and NH3-N concentrations, while the TVFA and MCP concentrations were decreased in both breeds (P<0.05). Rumen NH3-N concentrations of Tibetan sheep was larger than that of goats. (P<0.05).3) Moist-heat stress had a negative influence in the populations of R.albus, R.amylophilus and P.ruminicola of both breeds (P<0.05), and the populations of bacteria above were lager in goats than Tibetan sheep (P<0.05).Above all, the results showed that moist-heat stress increased the respiratory rate and rectal temperature, decreased the performance of Tibetan sheep and goats, while the Tibetan sheep suffered more deeply than goats under moist-heat stress. Moist-heat stress changed the endocrine hormone levels and altered the energy and protein metabolism in both of Tibetan sheep and goats, so that Tibetan sheep and goats could adapt to the moist-heat environment. The decreased oxidation resistance and immunity in both Tibetan sheep and goats were observed under moist-heat stress. Moreover, the Tibetan sheep had a severe influence of moist-heat stress on immunity while the oxidation resistance in goats was serious effected by moist-heat stress. The apparent digestibility of CP and NDF were decreased when Tibetan sheep and goats were suffered in moist-heat stress, and the NDF digestibility of Tibetan sheep had a larger decreasing amount than that of goats. Rumen cellulolytic bacteria and amylolysis bacteria were decreased in both Tibetan sheep and goats under moist-heat stress, as well as TVFA and MCP concentrations decreased. In conclusion, the moist-heat stress had a greater influence on Tibetan sheep than goats according to the variation of respiratory rate, rectal temperature and the ADG reduced rate.