Veterinary Medicine Teaching and Research Center, 18830 Road 112, Tulare, CA 93274; Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis 95616.
Veterinary Medicine Teaching and Research Center, 18830 Road 112, Tulare, CA 93274; Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis 95616.
J Dairy Sci. 2017 Jul;100(7):5774-5781. doi: 10.3168/jds.2016-12394. Epub 2017 May 3.
The objective of this study was to evaluate colostrum IgG concentration harvested at first and second milking from multiparous Jersey cows, the dam's lactation number, colostrum yield, and time of first milking. In addition, we validated the use of a Brix refractometer to estimate IgG concentration in colostrum from multiparous Jersey cows using radial immunodiffusion as the reference method. Colostrum samples and total weight of colostrum harvested at first (n = 134) and second (n = 68) milking were collected from 134 multiparous Jersey cows housed in a California herd. Fresh colostrum samples were analyzed for IgG concentration with Brix refractometry and frozen samples by radial immunodiffusion. A total of 90.4 and 42.7% of the samples from first and second milking met industry standards of quality for IgG concentration (>50 g/L). Second and third lactation cows had similar colostrum IgG concentration but lower than cows on their fourth and greater lactation. At second milking, 56.4% of cows on their fourth or greater lactation had colostrum IgG concentrations >50 g/L. When colostrum yield increased from low (<3 kg), medium (3 to 6 kg), to high (>6 kg), IgG concentration decreased. Higher IgG concentration was observed on colostrum harvested at <6 h (short) versus 6 to 11 h (medium) after calving. However, IgG concentration in colostrum harvested after 11 h (long) was similar to that harvested at short and medium time. Readings of %Brix were highly correlated with IgG at first (r = 0.81) and second (r = 0.77) milking. The best Brix threshold to identify colostrum from first milking with >50 IgG g/L was 20.9% based on logit equations with Youden's index criterion and 18.0% based on accuracy criterion. For colostrum harvested at second milking, similar Brix thresholds were obtained, 19.2 and 19.0%, regardless of whether Youden's index or accuracy was used as the selection criterion. Our results indicate that the dam's lactation number, colostrum yield, and time of first milking relative to calving are associated with IgG concentration in colostrum from multiparous Jersey cows. Second milking colostrum from mature Jersey cows should be evaluated to extend colostrum supply on dairies especially during times of shortage. Readings of %Brix can be used to rapidly estimate IgG concentration in Jersey colostrum harvested at first and second milking.
本研究旨在评估经产荷斯坦奶牛的初乳和第二次挤奶时的 IgG 浓度、奶牛的泌乳次数、初乳产量和首次挤奶时间。此外，我们还使用折射仪（Brix refractometer）验证了利用放射免疫扩散法（radial immunodiffusion）作为参考方法来估计经产荷斯坦奶牛初乳 IgG 浓度的方法。我们从加利福尼亚的一个牛群中采集了 134 头经产荷斯坦奶牛的初乳（n = 134）和第二次挤奶（n = 68）的样本和总重量。采集新鲜初乳样本，用折射仪（Brix refractometer）分析 IgG 浓度，用冷冻样本进行放射免疫扩散。初乳和第二次挤奶的 IgG 浓度均有 90.4%和 42.7%的样本达到行业标准（>50 g/L）。处于第二泌乳期和第三泌乳期的奶牛的初乳 IgG 浓度相似，但低于处于第四泌乳期及以上的奶牛。第二次挤奶时，4 胎及以上的奶牛中有 56.4%的初乳 IgG 浓度>50 g/L。随着初乳产量从低（<3 kg）、中（3-6 kg）到高（>6 kg）增加，IgG 浓度下降。在产后 6 小时内（短时间）采集的初乳中观察到较高的 IgG 浓度，而在产后 6-11 小时（中等时间）采集的初乳中 IgG 浓度较低。然而，在产后 11 小时（长时间）采集的初乳中的 IgG 浓度与在短时间和中等时间采集的初乳中的 IgG 浓度相似。Brix 读数与第一次（r = 0.81）和第二次（r = 0.77）挤奶时的 IgG 高度相关。基于逻辑方程和尤登指数标准，确定第一次挤奶时可以将 20.9%的 Brix 读数作为识别>50 IgG g/L 初乳的最佳阈值，而基于准确性标准，确定 18.0%的 Brix 读数作为识别>50 IgG g/L 初乳的最佳阈值。对于第二次挤奶采集的初乳，无论使用尤登指数还是准确性作为选择标准，都可以获得类似的 Brix 阈值，为 19.2%和 19.0%。这些结果表明，奶牛的泌乳次数、初乳产量和首次挤奶时间与经产荷斯坦奶牛的初乳 IgG 浓度有关。成熟荷斯坦奶牛的第二次挤奶初乳应进行评估，以延长奶牛场的初乳供应，尤其是在短缺时期。Brix 读数可以快速估计经产荷斯坦奶牛初乳和第二次挤奶的 IgG 浓度。
