Hamon A, Dufour S, Kurban D, Lemosquet S, Gervais R, Guinard-Flament J
PEGASE, INRAE, Institut Agro, 35042 Rennes, France.
Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, QC, J2S 2M2 Canada.
J Dairy Sci. 2024 Jul;107(7):5041-5053. doi: 10.3168/jds.2023-24134. Epub 2024 Feb 29.
Several studies have described variations in lactose content (LC) in dairy cows during udder quarter health disorder or negative energy balance (NEB). However, their joint effects on LC have never been described. This was the aim of a longitudinal observational study performed on 5 Quebec dairy farms using automatic milking systems. Quarter milk samples were collected every 14 d from 5 to 300 DIM. Quarter health status was described by combining SCC level (SCC or SCC: < or ≥100,000 cells/mL, respectively) and infectious status (Patho or Patho: absence or presence of pathogens on a milk culture, respectively). Cows with NEB in early lactation (DIM <70) were identified using milk BHB content: <0.15 mM = BHB-; 0.15 to 0.19 mM = BHB+; >0.19 mM = BHB++. A total of 14,505 quarter cisternal milk samples were collected from 380 lactating cows. The quarter LC was analyzed using a mixed linear regression model with the following fixed effects: quarter health status, parity, time interval between last milking and sampling, quarter milk yield (in kg/d), DIM, and herd. A random quarter intercept with a repeated measures correlation structure and a cow random intercept were also specified. The LC of SCC quarters was lower (-0.17 ± 0.013 percentage points) compared with LC of SCC quarters for both primiparous and multiparous cows. Of the 162 bacterial species identified, only 8 species had a prevalence greater than 4.0%, and just 5 of them were associated with a reduction in LC: Staphylococcus aureus, Staphylococcus chromogenes, Streptococcus dysgalactiae, Staphylococcus epidermidis, and Staphylococcus simulans. Cows identified as BHB+ and BHB++ in early lactation had a lower LC (-0.05 ± 0.019 and -0.13 ± 0.020 percentage points, respectively) compared with BHB- cows. For BHB++ cows, in both parity groups the decrease in LC (-0.20 ± 0.025 percentage points) was higher in SCC quarters compared with SCC quarters. Moreover, the additive effect of the quarter health status and NEB on milk LC was greater with larger increases in BHB. Our findings highlight the necessity to jointly take into consideration both quarter health status and milk BHB concentration when using LC as a biomarker for NEB.
多项研究描述了奶牛在乳房象限健康紊乱或负能量平衡（NEB）期间乳糖含量（LC）的变化。然而，它们对LC的联合影响从未被描述过。这就是在魁北克的5个使用自动挤奶系统的奶牛场进行的一项纵向观察研究的目的。在产奶5至300天期间，每14天采集一次乳房象限的牛奶样本。通过结合体细胞计数水平（SCC或SCC：分别为<或≥100,000个细胞/毫升）和感染状态（Patho或Patho：分别为牛奶培养物中无或有病原菌）来描述乳房象限的健康状况。使用牛奶β-羟基丁酸（BHB）含量来识别早期泌乳期（产奶天数<DIM 70）患有NEB的奶牛：<0.15毫摩尔=BHB-；0.15至0.19毫摩尔=BHB+；>0.19毫摩尔=BHB++。从380头泌乳奶牛中总共采集了14,505份乳房象限乳池牛奶样本。使用混合线性回归模型分析乳房象限LC，该模型具有以下固定效应：乳房象限健康状况、胎次、上次挤奶与采样之间的时间间隔、乳房象限产奶量（千克/天）、产奶天数和牛群。还指定了具有重复测量相关结构的随机乳房象限截距和奶牛随机截距。对于初产和经产奶牛，SCC乳房象限的LC均低于SCC乳房象限的LC（-0.17±0.013个百分点）。在鉴定出的162种细菌中，只有8种的流行率大于4.0%，其中只有5种与LC降低有关：金黄色葡萄球菌、产色葡萄球菌、乳房链球菌、表皮葡萄球菌和模仿葡萄球菌。与BHB-奶牛相比，早期泌乳期被鉴定为BHB+和BHB++的奶牛的LC较低（分别为-0.05±0.019和-0.13±0.020个百分点）。对于BHB++奶牛，在两个胎次组中，SCC乳房象限的LC下降幅度（-0.20±0.025个百分点）均高于SCC乳房象限。此外，随着BHB的大幅增加，乳房象限健康状况和NEB对牛奶LC的累加效应更大。我们的研究结果强调，在将LC用作NEB的生物标志物时，有必要同时考虑乳房象限健康状况和牛奶BHB浓度。
