Pereira Fabiellen C, Kumara Sagara, Fleming Anita, Lai Shu Zhan, Wilson Ella, Gregorini Pablo
Department of Agricultural Sciences, Faculty of Agricultural and Life Sciences, Lincoln University, Lincoln, P.O. Box 85084, Christchurch 7647, New Zealand.
Animals (Basel). 2024 Dec 26;15(1):32. doi: 10.3390/ani15010032.
The societal pressure on intensive pastoral dairying demands the search for strategies to reduce the amount of N flowing through and excreted by dairy cows. One of the strategies that is being currently explored focuses on the animal as a solution, as there are differences in N metabolism between cows even within the same herd. This work was conducted to explore such an approach in A1PF herds in New Zealand and the possibility of identifying A1PF cows that are divergent for milk urea nitrogen (MUN) concentration through phenotyping as a potential viable strategy to reduce N leaching and emissions from temperate dairy systems. Three herd tests were conducted to select a population sample of 200 cows (exhibiting the lowest 100 and highest 100 MUN concentrations). Milk samples were collected from the 200 cows during mid and late lactation to test for milk solids content and MUN. From the 200 cows, urine for urinary N concentration (UN), blood for plasma urea N, total antioxidants (TAS), and glutathione peroxidase (GPx) were collected from the 20 extremes (the lowest 10 and highest 10 MUN concentrations). Milk urea N was greater in cows selected as high-MUN cows (16.2 vs. 14.32 ± 0.23 mg/dL) and greater during late lactation (16.9 vs. 13.0 ± 0.19 mg/dL). Milk solids and fat content were 38% and 20% greater in cows selected as low-MUN cows than in high-MUN cows during mid lactation ( < 0.001). Low-MUN cows had lower UN than high-MUN cows during mid lactation (0.64 vs. 0.88 ± 0.11%). The N concentration in the plasma ( = 0.01) and Tas ( = 0.06) were greater during late lactation. There was a positive relationship between the MUN concentration phenotype used for selection and the MUN concentration for the trial period and MUN concentration and UN concentration during mid and late lactation ( < 0.001). Our results suggest that A1PF cows within a commercial herd can be phenotyped and selected for low-MUN, which may be potentially a viable strategy to reduce N losses to the environment and create healthier systems. Following genetic tracking, those cows can be bred to further promote low-MUN A1PF herds.
集约化牧场式奶牛养殖面临的社会压力要求寻找策略来减少奶牛体内流动和排泄的氮量。目前正在探索的一种策略是以动物本身作为解决方案，因为即使在同一牛群中，奶牛的氮代谢也存在差异。开展这项工作是为了在新西兰的A1PF牛群中探索这种方法，并通过表型分析来识别牛奶尿素氮（MUN）浓度存在差异的A1PF奶牛，以此作为减少温带奶牛养殖系统中氮淋失和排放的一种潜在可行策略。进行了三次牛群测试，以选取200头奶牛的群体样本（表现出最低100个和最高100个MUN浓度）。在泌乳中期和后期从这200头奶牛采集牛奶样本，检测乳固体含量和MUN。从这200头奶牛中，从20头极端个体（最低10个和最高10个MUN浓度）采集尿液用于检测尿氮浓度（UN），采集血液用于检测血浆尿素氮、总抗氧化剂（TAS）和谷胱甘肽过氧化物酶（GPx）。被选为高MUN奶牛的奶牛，其牛奶尿素氮含量更高（16.2对14.32±0.23毫克/分升），且在泌乳后期更高（16.9对13.0±0.19毫克/分升）。在泌乳中期，被选为低MUN奶牛的奶牛，其乳固体和脂肪含量比高MUN奶牛分别高约38%和20%（<0.001）。在泌乳中期，低MUN奶牛的UN低于高MUN奶牛（0.64对0.88±0.11%）。在泌乳后期，血浆中的氮浓度（=0.01）和Tas（=0.06）更高。用于选择的MUN浓度表型与试验期的MUN浓度以及泌乳中期和后期的MUN浓度与UN浓度之间存在正相关关系（<0.001）。我们的结果表明，商业牛群中的A1PF奶牛可以通过表型分析来选择低MUN奶牛，这可能是减少向环境中氮损失并创建更健康养殖系统的一种可行策略。经过基因追踪后，可以繁育这些奶牛以进一步推广低MUN的A1PF牛群。
