Webb Edward Cottington, de Bruyn Elandri
Production Animal Physiology Research Group, Department of Animal Science, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
Animals (Basel). 2021 Oct 27;11(11):3068. doi: 10.3390/ani11113068.
This study investigated the effects of MUN and climatological factors on the inter calving period (ICP), reproductive performance (RP%), and reproductive index (RI) in Holstein Friesian ( = 1177) and Jersey cows ( = 3305) in different seasons in the subtropics. Threshold values for MUN on the reproduction of dairy cows in the subtropics remain controversial due to complex environmental interactions, especially with high environmental temperatures. A retrospective analysis was conducted of data obtained from the National Milk Recording scheme of the Agricultural Research Council (ARC) in South Africa. The results confirm that MUN influences the reproduction of dairy cows in the subtropics. MUN concentrations exceeding 18.1 ± 4.28 mg/dL in Holstein Friesian cows and 13.0 ± 4.70 mg/dL in Jersey cows extended the inter calving period (ICP), and decreased RP% and RI. Jersey cows have a lower threshold MUN concentration compared to Holstein Friesian cows, but they are not adversely affected by high humidity or temperatures, while Holstein Friesian cows are.
本研究调查了在亚热带不同季节里，代谢尿素氮（MUN）和气候因素对荷斯坦奶牛（n = 1177）和泽西奶牛（n = 3305）产犊间隔期（ICP）、繁殖性能（RP%）及繁殖指数（RI）的影响。由于存在复杂的环境相互作用，尤其是与高温环境的相互作用，亚热带地区奶牛繁殖方面的MUN阈值仍存在争议。本研究对从南非农业研究理事会（ARC）的国家牛奶记录计划中获得的数据进行了回顾性分析。结果证实，MUN会影响亚热带地区奶牛的繁殖。荷斯坦奶牛的MUN浓度超过18.1±4.28毫克/分升，泽西奶牛的MUN浓度超过13.0±4.70毫克/分升时，会延长产犊间隔期（ICP），并降低RP%和RI。与荷斯坦奶牛相比，泽西奶牛的MUN阈值浓度较低，但它们不受高湿度或高温的不利影响，而荷斯坦奶牛则会受到影响。
