McDougall S, Malcolm D, Prosser Cg
a Cognosco, Animal Health Centre , Morrinsville , New Zealand.
N Z Vet J. 2014 May;62(3):136-45. doi: 10.1080/00480169.2013.865294. Epub 2014 Jan 8.
To determine the prevalence of intramammary infection (IMI) of lactating dairy goats between 0 and 4 days postpartum, the prevalence and incidence rate of new IMI at Weeks 2, 14 and 27 of lactation, and the relationship between herd-level prevalence of IMI and bulk tank somatic cell count (BTSCC).
Milk samples were collected from 8% of a herd (total 624 does) from 18 dairy goat herds in the Waikato region of New Zealand, for bacteriology and somatic cell count (SCC) determination, from both glands within 4 days of kidding (Week 0) and again at Weeks 2, 14 and 27. Prevalence of IMI was determined at each time point and incidence rate calculated for Weeks 0-2, 2-14, and 14-27. Greenwood and Reed-Frost models were compared for estimation of the transmission parameter for all pathogens, and for Staphylococcus aureus, coagulase negative staphylococci (CNS) and Corynebacterium spp. separately.
Bacteria were isolated from 1,122/4,814 (23.3%) glands, with CNS (13.4%) and Corynebacterium spp. (7.3%) being the most common isolates. Prevalence of any IMI increased with stage of lactation, varied among herds, and increased with age (all p<0.05). Incidence rate was 80, 24 and 7 new IMI/10,000 gland days for Weeks 0-2, 2-14 and 14-27, respectively. Incidence rate for any IMI increased with age and with the presence of an IMI in the contralateral gland, and varied among herds (p<0.001). The transmission of each pathogen was better modelled assuming contagiousness (Reed-Frost models), than not (Greenwood models). At gland level, IMI increased SCC at all stages of lactation (p<0.001). The gland prevalence of IMI within herds was positively associated with ln BTSCC at Week 2 (p=0.02), but not Weeks 14 or 27 (p>0.05).
Prevalence of IMI increased with stage of lactation, but the highest incidence rate of new IMI occurred in early lactation. Models accounting for the contagious nature of infection fitted better than those not accounting for contagiousness. BTSCC was only associated with prevalence of IMI in early lactation.
Reduction of BTSCC in dairy goats may be best achieved by minimising the prevalence and incidence of new IMI in early lactation. Further studies are required to define management factors associated with the between herd, and stage of lactation, effects on prevalence and incidence rate in order to reduce BTSCC throughout lactation.
确定产后0至4天泌乳期奶山羊乳房内感染（IMI）的患病率、泌乳第2、14和27周新IMI的患病率和发病率，以及IMI的畜群水平患病率与奶罐体细胞计数（BTSCC）之间的关系。
从新西兰怀卡托地区18个奶山羊群中抽取8%的畜群（共624只母羊）采集奶样，用于细菌学和体细胞计数（SCC）测定，在产羔后4天内（第0周）从两侧乳腺采集，在第2、14和27周再次采集。在每个时间点确定IMI的患病率，并计算第0 - 2周、2 - 14周和14 - 27周的发病率。比较格林伍德模型和里德 - 弗罗斯特模型对所有病原体以及分别对金黄色葡萄球菌、凝固酶阴性葡萄球菌（CNS）和棒状杆菌属的传播参数进行估计。
从4814个乳腺中的1122个（23.3%）分离出细菌，其中CNS（13.4%）和棒状杆菌属（7.3%）是最常见的分离菌。任何IMI的患病率随泌乳阶段增加，在不同畜群间有所差异，并随年龄增长而增加（所有p<0.05）。第0 - 2周、2 - 14周和14 - 27周新IMI的发病率分别为每10000个乳腺日80、24和7例。任何IMI的发病率随年龄和对侧乳腺存在IMI而增加，且在不同畜群间有所差异（p<0.001）。假设具有传染性（里德 - 弗罗斯特模型）比不具有传染性（格林伍德模型）能更好地模拟每种病原体的传播。在乳腺水平，IMI在泌乳的所有阶段均增加SCC（p<0.001）。畜群内IMI的乳腺患病率在第2周与ln BTSCC呈正相关（p = 0.02），但在第14周或27周无相关性（p>0.05）。
IMI的患病率随泌乳阶段增加，但新IMI的最高发病率出现在泌乳早期。考虑感染传染性的模型比不考虑传染性的模型拟合得更好。BTSCC仅与泌乳早期IMI的患病率相关。
通过尽量减少泌乳早期新IMI的患病率和发病率，可能是降低奶山羊BTSCC的最佳方法。需要进一步研究确定与畜群间以及泌乳阶段相关的管理因素，这些因素对患病率和发病率的影响，以便在整个泌乳期降低BTSCC。
