Cognosco, Anexa, Morrinsville, New Zealand.
N Z Vet J. 2021 Sep;69(5):285-293. doi: 10.1080/00480169.2021.1924091. Epub 2021 Jun 9.
To assess the effect of oral supplementation with fully oxidised β-carotene (OxBC) on bacteriological cure, the incidence of clinical mastitis, and somatic cell counts (SCC) in pasture-fed cows with subclinical intramammary infection.
Cows from four dairy herds were enrolled in early lactation if they had quarter-level SCC >200,000 cells/mL and they had a recognised bacterial intramammary pathogen in one or more quarters. They were randomly assigned to be individually fed from Day 0, for a mean of 40 days, with 0.5 kg of a cereal-based supplementary feed that either contained 300 mg of OxBC (treatment; n = 129 quarters) or did not (control; n = 135 quarters). Quarter-milk samples were collected on Days 21 and 42 for microbiology and SCC assessment. Bacteriological cure was defined as having occurred when the bacteria present on Day 0 were not isolated from samples collected on Days 21 or 42. A new intramammary infection was defined as a bacterial species isolated either on Day 21 or 42 differing from that isolated on Day 0. Clinical mastitis was diagnosed and recorded by herdowners up to Day 42.
The bacteriological cure rate was greater for quarters from cows in the treatment group (13.9 (95% CI = 4.1-23.7)%) than for cows in the control group (6.9 (95% CI = 4.8-9.1)%; p = 0.02). The percentage of quarters that developed a new intramammary infection at Day 21 or 42 was greater for cows in the treatment group (17.9 (95% CI = 6.7-29.1)%) than for cows in the control group (13.0 (95% CI = 4.3-21.8)%; p < 0.01). The prevalence of quarters that were infected on Day 42 was less in cows in the treatment group (79.9 (95% CI = 62.3-97.6)%) than the control group (88.2 (95% CI = 78.4-97.9)%; p = 0.009). The incidence of quarters diagnosed with clinical mastitis by Day 42 was lower in cows from the treatment group (1/129 (0.78 (95% CI = 0.02-4.24)%)) than in cows from the control group (6/135 (4.44 (95% CI = 1.65-9.42)%; p = 0.03)). Mean quarter-level SCC was not statistically different between treatment groups (p = 0.34).
Feeding 300 mg/cow/day of OxBC resulted in a higher bacteriological cure rate, a lower prevalence of intramammary infection, and a lower incidence of clinical mastitis compared to untreated controls. However new intramammary infections increased in treated cows, and the magnitude of the increased bacteriological cure was low, resulting in 80% of cows remaining infected at Day 42. Therefore treatment with OxBC should be considered as an adjunct to other mastitis control measures.
评估口服全氧化β-胡萝卜素（OxBC）对亚临床型乳腺炎奶牛的细菌学治愈率、临床乳腺炎发病率和体细胞计数（SCC）的影响。
如果奶牛在产犊后早期的每季度 SCC ＞20 万细胞/ml，并且在一个或多个乳区中存在公认的细菌型乳腺炎病原体，则将其纳入研究。这些奶牛随机分配，从第 0 天开始，每天单独喂养含有 300mg OxBC 的谷物基础补充饲料（处理组；n=129 个乳区）或不添加（对照组；n=135 个乳区），持续 40 天。在第 21 天和第 42 天采集乳区奶样进行微生物学和 SCC 评估。细菌学治愈率定义为在第 0 天存在的细菌在第 21 天或第 42 天的样本中未被分离。新的乳腺炎定义为在第 21 天或第 42 天分离的细菌与第 0 天分离的细菌不同。临床乳腺炎由牧场工人在第 42 天之前进行诊断和记录。
与对照组（6.9%（95%CI=4.8-9.1%））相比，治疗组（13.9%（95%CI=4.1-23.7%））的奶牛的细菌学治愈率更高（p=0.02）。在第 21 天或第 42 天发生新乳腺炎的乳区比例，治疗组（17.9%（95%CI=6.7-29.1%））高于对照组（13.0%（95%CI=4.3-21.8%））（p＜0.01）。治疗组第 42 天感染乳区的患病率（79.9%（95%CI=62.3-97.6%））低于对照组（88.2%（95%CI=78.4-97.9%））（p=0.009）。在第 42 天，治疗组的奶牛被诊断为临床乳腺炎的乳区比例（1/129（0.78%（95%CI=0.02-4.24%）））低于对照组（6/135（4.44%（95%CI=1.65-9.42%）））（p=0.03）。治疗组和对照组之间的平均乳区 SCC 无统计学差异（p=0.34）。
与未治疗的对照组相比，每天给 OxBC 300mg/牛可提高细菌学治愈率，降低乳腺炎的发生率和临床乳腺炎的发病率。然而，治疗奶牛的新乳腺炎发病率增加，增加的细菌学治愈率较低，导致 80%的奶牛在第 42 天仍处于感染状态。因此，OxBC 的治疗应被视为乳腺炎控制措施的辅助手段。
