热应激奶牛血清NO浓度和NOS活力的变化

为探索不同品种奶牛血清中一氧化氮合成酶（NOS）的活力以及一氧化氮（NO）浓度变化与热应激的关系。此实验在热应激期（THI 82.61±0.60）和非热应激期（THI 47.42±0.51）对荷斯坦牛（n=20）和娟-荷F1牛（n=20）血清NOS活力及NO浓度水平进行测定。结果表明：荷斯坦牛和娟-荷F1牛在热应激期血清NOS的活力均显著低于非热应激期（P〈0.01）;热应激期娟-荷F1牛血清NOS的活力显著低于荷斯坦牛（P〈0.01）,非热应激期二者差异不显著（P〉0.05）;热应激期荷斯坦牛血清NO浓度较非热应激期显著降低（P〈0.05）,娟-荷F1牛有降低趋势,但差异不显著（P〉0.05）;非热应激期荷斯坦牛血清中NO浓度显著高于娟-荷F1牛（P〈0.05）,热应激期二者差异不显著（P〉0.05）。

Effect of heat stress on NO and NOS levels in the serum of dairy cows

In order to explore the relationship between heat stress and nitric oxide synthase (NOS) and nitric oxide (NO) in the serum of Holstein and Jersey×Holstein dairy cows. Serum was collected from Holstein (n=20) and Jersey×Holstein F1 dairy cows (n=20) in heat stress (THI 82.61±0.60) and no heat stress period (THI 47.42±0.51). The levels of NOS and NO were measured. The result show that: the levels of NOS in serum in heat stress period were significant lower than those in no heat stress period both in Holstein and Jersey×Holstein F1 dairy cows (P<0.01). In heat stress period, levels of NOS of Jersey×Holstein F1 dairy cow were significant lower than those of Holstein dairy cow (P<0.01); but were no significant difference between Holstein and Jersey×Holstein F1 dairy cow (P>0.05) in no heat stress period. The levels of NO in serum in heat stress period were significantly lower than those in no heat stress period in Holstein dairy cow (P<0.05); but were no significant difference between heat stress period and no heat stress period (P>0.05) in Jersey×Holstein F1 dairy cow. In no heat stress period, the levels of NO of Holstein dairy cow in serum were higher than that of Jersey×Holstein F1 dairy cow (P<0.05), but in heat stress period there is no significant difference(P>0.05).