| The experiment was conducted to investigate the effects of three kinds ofadditives in cow feed, in order to study the best methed for controlling heat stress ofdariy cow. Twenty lactating Holsteins cows, fed with the same basal diet, were chosenby weight, age, and days in parity and randomly allocated to4groups, namely, GroupA (control) supplemented with none, Group B supplemented with GABA (10g/d),Group C supplemented with Chinese herbal drugs (150g/d), Group D supplementedwith Chinese herbal drugs (150g/d) and GABA (10g/d) together. The cows wereraised for7days of pretreating time and30days of experimental time. The resultswere as follows:1. During the test, the mean air temperature in cowhouse ranged from27.4degree to34.8degree, the humidity ranged from62.5percent to79percent, the meantemperature-humidity index (THI) was between77.86and86.77, which indicated thatduring most of the trial time, cows experienced a moderate heat stress.Compared to control group, three groups of medicinal additives decreased therectal temperature and respiration rate of the cows, in which, the respiration rate ofdairy cows in Group B on d10was significantly lower (P<0.05), and the rectaltemperature was not significant changed(P>0.05); the rectal temperature of dairycows in Group C on d10was significantly lower (P<0.05), but not for respiration rate;both the rectal temperature and respiration rate of the cows in Group D weresignificantly decreased (P<0.05).3. Compared to control group, the milk yield of dairy cows in Group B, C and Dwere scaled up by6.6%,4.1%and11.9%respectively, in which Group B and Cindicated no significant difference compared with group A, whereas milk yield,lactoprotein and total milk solid of dairy cows in Group D were all significantly raised(P<0.05).4. Compared to Group A, the blood glucose and serum Na+concentrations ofdairy cows in Group D were significantly increased (P<0.05), and serum Cl-concentrations were significantly raised (P<0.01); the serum Cl-concentrations ofdairy cows in Group C were significantly increased (P<0.05).5. Compared to Group A, MDA levels in sera of three test groups of dairy cowswere significantly decreased (P<0.05), the activities of GSH-Px in Group B and Cwere significantly increased (P<0.05). Meanwhile, the activities of SOD and GSH-Px in Group D were significantly enhanced (P<0.05).6. Compared to Group A, the concentrations of IgG and IL-2in sera of dairycows in Group D were significantly raised (P<0.01), the concentrations of IgG inGroup C was significantly incresed (P<0.05); the concentrations of IgG and IL-2inGroup B were significantly raised (P<0.05); whereas, IgA and IgM in all of the testgroups had no significant change (P>0.05).7. Compared to Group A, Cor levels in sera of dairy cows in Group D weresignificantly decreased (P<0.01), ACTH, CRH and INS levels were significantlylowered (P<0.05), GH and T3levels were significantly increased (P<0.05) on d15.ACTH and INS levels in sera of dairy cows in Group D were lower (P<0.05), but T3levels was significantly higher (P<0.05) on d30; Cor levels in sera of dairy cows inGroup C were significant decreased (P<0.01), and T3levels were significant increased(P<0.05) on d30. Cor and INS levels in sera of dairy cows in Group B weredecreased, while T3and GH levels were significantly rasied (P<0.05) on d15.The results demonstrated that Chinese herbal drugs in conjunction with GABArasied the milk yeild and quality of dariy cows in high temperature environment,enhanced the immunity and antioxygenic property, promoted the secretion of T3, andinhibted the secretion of Cor and INS, thus effectively alleviated the HS-relateddepression of cows. |
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