Differentially expressed genes associated with Staphylococcus aureus mastitis of Canadian Holstein cows

To study pathway specific gene expression within the immune-endocrine axis of dairy cows with Staphylococcus aureus mastitis, mRNA was collected from blood mononuclear cells (BMCs) and milk somatic cells (MSCs) of cows (n = 7) identified as culture positive for S. aureus and their matched negative control cows (n = 7) with no evidence of S. aureus mastitis. Labeled cDNA probes derived from BMCs and MSCs of infected and healthy cows were applied to a bovine immune-endocrine cDNA array containing 167 genes. Genes with a log₂ ratio ≥ 0.5 were considered to be up-regulated and genes with a log₂ ratio ≤ −0.5 to be down-regulated. In total, 22 genes were differentially displayed in BMCs and 16 genes in MSCs of case versus controls. Expression of selected genes in BMCs and MSCs were confirmed by real-time PCR. The RT-PCR results were highly correlated with microarray measurements. Some of these genes, such as interleukin (IL)-8 have been previously implicated in other bacterial diseases, and are known to regulate immune responses; whereas, others may reflect novel pathways or genes involved in progressive mammary gland disease. For example, IL-18 was up-regulated in BMCs but not MSCs of mastitic quarters, while IL-17 was more highly expressed in MSCs compared to BMCs. This study identified a number of differentially expressed genes associated with bovine S. aureus mastitis and demonstrates the intricacy of the patterns of gene expression that influence host response to a complex pathogen of significant relevance to both human and veterinary medicine.     

Effect of photoperiod on milk yield and quality, and reproduction in dairy goats

The objective of this study was to examine the effect of long day photoperiod (LDPP) on milk production and reproduction in milk goats. A total of 79 goats were randomly assigned to three treatment groups blocked by day of kidding. Group 1 (Gr1, n = 26) was subjected to natural photoperiod from January 6 to December 5. Group 2 (Gr2, n = 24) was subjected to LDPP (20 h light, 4 h dark) from June 22 to December 5. Group 3 (Gr3, n = 29) was subjected to LDPP from January 6 to December 6. Weekly milk weights and samples were collected for fat, protein and somatic cell count (SCC) determinations. Blood serum was harvested for progesterone (P4) determination. Results indicated a significant effect (p < 0.001) between treatments for body weight changes, feed intake and milk yield. Both light treated groups had a significantly higher (p < 0.001) average daily milk output for the entire lactation period than the control group (G1, 2.193 kg/day; G2, 2.517 kg/day; G3, 2.305 kg/day). Milk fat for the overall lactation was significantly higher in Gr3 (+ 0.19 g/100 ml) than for Gr2 (+ 0.06 g/100 ml) when compared to the control group (x g/100 ml) under natural photoperiod. Somatic cell counts throughout lactation were significantly (p < 0.001) lower for Gr2 (1.70 million/ml) and higher for Gr3 (2.03 million/ml), with the control group (Gr1) having an intermediate level (1.96 million/ml). Progesterone levels between June 9 and August 30 indicated that 27%, 48% and 63% of the animals had P4 levels in excess of 1.0 ng/ml serum for Gr1, Gr2 and Gr3, respectively. Pregnancy diagnosis by ultrasound in December revealed that a high number of does in the light treated groups (10 of 37) were pseudo-pregnant when compared with the control group (1 of 21). Although light appeared to be effective in increasing milk production, further investigations are needed to evaluate the effect of LDPP on pseudo-pregnancy in dairy goats.     

Effects of Saccharomyces cerevisiae on in vivo organic matter digestibility and milk yield in buffalo cows

The influence of a dietary supplementation with Saccharomyces cerevisiae (SC) during the first and the second phase of lactation on dry matter (DM) intake, organic matter digestibility, milk yield and quality and haematological profile was evaluated in buffalo cows. Lactating buffaloes (n = 190), 118.7 days in milk (DIM), were randomly divided into Group C (control, n = 95) and Group T (fed diet supplemented with 98 billion CFU of S. cerevisiae, n = 95). Eight buffaloes for each group (Groups T1 and C1), 85.4 DIM, were used to study the in vivo digestibility and the haematological profile. No differences were found for DM intake (16.5 kg·day^− 1) and haematological profile. The SC supplementation increased milk yield (7.9 ± 0.2 vs. 7.4 ± 0.2; P < 0.01) but did not affect milk fat and protein. SC supplementation increased OM digestibility, mainly, in the first phase of lactation (< 135 days), thus allowing a higher energy availability for milk yield and reduced fat mobilization.     

新疆部分地区生乳中金黄色葡萄球菌的分离鉴定及耐药性分析

【目的】探明新疆部分地区生乳中金黄色葡萄球菌流行情况及耐药性,为该地区生乳中金黄色葡萄球菌的监测及保障生乳质量安全提供理论依据。【方法】试验随机从南北疆规模化奶牛场采集110份生乳样品。采用增菌培养、分离纯化、革兰氏染色、生化鉴定及PCR法对奶样中金黄色葡萄球菌进行分离鉴定,并利用微量肉汤稀释法及PCR方法对金黄色葡萄球菌进行16种抗菌药物的耐药表型及耐药基因分析。【结果】从110份奶样中分离出18株金黄色葡萄球菌,分离株呈浅黄色、光滑凸起的圆形菌落,革兰氏染色镜检呈紫色、短链状排列的革兰氏阳性菌,生化试验结果符合金黄色葡萄球菌生化特点,经16S rDNA及nuc基因PCR扩增鉴定为金黄色葡萄球菌,分离率为16.36%(18/110)。药敏试验结果显示,金黄色葡萄球菌分离株对氨苄西林、青霉素及磺胺异噁唑具有较高的耐药性,耐药率分别为100%、83.33%和77.78%,而对万古霉素、复方新诺明、苯唑西林、头孢噻吩、头孢噻呋、利福昔明及环丙沙星7种抗菌药物高度敏感,敏感率分别为100%、100%、94.44%、94.44%、94.44%、94.44%和94.44%。其中有14株金黄色葡萄球菌为多重耐药菌,多重耐药率为77.78%。耐药基因检测结果显示,大环内酯类耐药基因ermB检出率最高,为50.00%,其次为β-内酰胺类耐药基因mecA,检出率为27.28%,磺胺类耐药基因Sul1的检出率为22.22%。【结论】新疆奶牛场生乳中分离的金黄色葡萄球菌的流行及耐药情况仍较严重,且存在多重耐药现象,因此,对生乳中金黄色葡萄球菌耐药性的监测有重要意义。     

Impacts of a modified farrowing pen design on sow and litter performances and air quality during two seasons

The impacts of using a modified farrowing pen (MOD) on the performance of sows and their litters and on ambient air quality over a hot and a cool season were evaluated. Primiparous Yorkshire × Landrace sows farrowed either during the months of February and March (thermoneutralily, TN) or June and July (heat-stress, HS). Temperatures within each season were controlled to 21 and 29 °C, respectively, for TN and HS. Animals from each group were assigned to a standard farrowing crate (STD; TN, n = 17; HS, n = 16) or a MOD pen (TN, n = 19; HS, n = 19). The MOD pen consisted of a STD crate with a 1.5 × 1.6-m comfort zone in the back, equipped with rubber floor mats, a feeder and a nipple waterer. Litter size was standardized to 10 or 11. No creep feed was provided and piglets were weighed weekly. Sows were weighed on days 2 and 22. Feed intake of sows was monitored daily, a milk sample was obtained on day 21 for compositional analyses and jugular blood samples were collected on days 2 and 21 to measure prolactin, IGF-I and urea. Sows consumed less feed (3.4 vs. 4.7 ± 0.1 kg/day, P < 0.001) in a hot than in a cool season and, at 29 °C, sows in MOD pens consumed more feed (3.9 vs. 3.0 ± 0.2 kg/day, P < 0.01) than sows in STD pens. Sow lactation weight loss was greater (− 26.4 vs. − 19.1 ± 1.9 kg, P < 0.05) for sows in STD than MOD pens in a hot season. The reduction in prolactin concentrations from days 2 to 22 of lactation tended to be greater (P = 0.08) in a hot season for sows in STD pens. Concentrations of urea and IGF-I increased as lactation advanced (P < 0.01) and IGF-I was lower for HS compared to TN sows on both days (P < 0.01), whereas urea was greater for HS sows on day 2 only (P < 0.01). Milk DM was less in a hot than in a cool season (P < 0.01). Average piglet weight gain was reduced in a hot compared to a cool season during the second week of lactation (P < 0.05) and this reduction was less in MOD than STD pens during the third week of lactation (P < 0.01). During a hot season, even though not significant, average weight gain of piglets from days 2 to 21 of lactation was reduced by 6.0% in MOD pens compared to 9.7% in STD pens.     

Phenotypic and genotypic traits of Staphylococcus aureus strains isolated from pig carcasses

A total of 142 S. aureus strains isolated from pig carcasses from abattoirs A (n = 98) and B (n = 44) were characterized by phenotypic and genotypic traits. Phenotypically, 96% showed yellow-pigmented colonies, 63% β/δ hemolysis, 85% were egg yolk-positive and 99% were positive for clumping factor/protein A. Only 25% of the strains were resistant to the antimicrobials tested (abattoir A: 19%; abattoir B: 39%), especially to penicillin and ampicillin. None of the strains harbored the mecA gene, which is conserved in methicillin-resistant S. aureus. The biofilm associated genes icaA, icaD and bap were present in 100%, 100% and 0% of the strains. Genes for staphylococcal enterotoxin (SE) were detected in 51% (abattoir A) and 14% of the strains (abattoir B). Among strains harboring SE genes (n = 56), 63%, 31%, 4% and 2% tested positive for seg/sei, seg, sei and sec, respectively. The amplification of the 3′ end of the coagulase gene (coa) yielded amplicons of 400, 436, 602, 682 or 776 bp. Coa restriction profile (CRP) analysis using HaeIII resulted in seven patterns (a–d, e1–e3). CRP (c) was detected most frequently at both abattoirs, whereas CRP (a) was restricted to abattoir A and CRP (e3) to abattoir B. In the slaughter process (abattoir B), (i) two CRPs (b and d) were only found before dehairing/singeing, and (ii) four CRPs (c, e1–e3) were identified throughout the process. The genotyping revealed a remarkable homogeneity in S. aureus strains from the two different abattoirs and the slaughter process stages. These results may be explained by the distribution of a limited number of S. aureus genotypes in the pig population. Moreover, as the predominant CRPs (c, e1–e3) persisted throughout the slaughter process in abattoir B, it may be hypothesized that these types are characterized by colonization advantages.     

Studies on vertical transmission of Trichinella spp. in experimentally infected ferrets (Mustela putorius furo), foxes (Vulpes vulpes), pigs, guinea pigs and mice

Vertical transmission of Trichinella spiralis was evaluated in ferrets (n = 21), foxes (n = 11), pigs (n = 12), guinea pigs (n = 16), and mice (n = 41). The placental barrier to be crossed by migratory Trichinella larvae varies structurally in different animal species. Ferrets and foxes have an endotheliochorial placenta structure, guinea pigs and mice a haemochorial, and pigs an epitheliochorial placenta. The non-encapsulating Trichinella pseudospiralis larvae have an extended muscle migration prior to entering a muscle cell. To evaluate if T. pseudospiralis was more likely to be transmitted to offspring, an additional group of foxes (n = 11) infected with T. pseudospiralis was included. Two different dose levels were used for ferrets, pigs, guinea pigs, and mice. In pigs and guinea pigs, infection was given at different times of the gestation period. Vertical transmission, measured as recovery of muscle larvae in the offspring, was demonstrated in both ferrets groups, in all four guinea pig groups, and in the high dose mouse group, but not in any fox or pig groups.     

内蒙古地区乳房炎奶样与环境中细菌的分离鉴定及耐药性分析

【目的】研究内蒙古地区部分奶牛养殖场乳房炎生鲜乳样本及环境样本致病菌种类和耐药性,为乳房炎的防控提供临床用药指导和参考。【方法】采用平板划线法对内蒙古地区4个规模化养殖场468份(乳房炎生鲜乳样本199份,乳房炎奶牛饲养环境样本269份)样本进行细菌分离培养,采用形态学观察、革兰氏染色镜检以及16S rDNA测序对分离出的细菌进行鉴定,且对引发乳房炎的主要致病菌进行药敏性试验。【结果】高盐甘露醇培养基上呈现出小、白且偏黄色的菌落,经16S rDNA测序比对,与金黄色葡萄球菌高度相似的菌株共56株,分离率为11.97%;在伊红-美蓝培养基上呈现出黑紫色泛有金属光泽的菌落,经16S rDNA测序比对,与大肠杆菌高度相似的菌株共44株,分离率为9.40%。在199份生鲜乳样本中,金黄色葡萄球菌和大肠杆菌的分离率最高,分别为21.11%和17.09%;在269份环境样本中,金黄色葡萄球菌和大肠杆菌的分离率分别为5.20%和3.72%。药敏试验结果显示,金黄色葡萄球菌对青霉素、磺胺异噁唑、氨苄西林、阿莫西林/克拉维酸的耐药性相对较高,耐药率分别为90.63%、78.13%、75.00%、68.75%;对庆大霉素、环丙沙星、复方新诺明的敏感性较高。大肠杆菌对氨苄西林、头孢噻吩、磺胺异噁唑存在明显耐药性,耐药率分别为100%、94.29%、45.71%;对链霉素、卡那霉素、庆大霉素、多粘菌素E、美罗培南、阿莫西林/克拉维酸以及利福昔明表现出较高敏感性。【结论】内蒙古地区引发奶牛乳房炎的主要致病菌为金黄色葡萄球菌、大肠杆菌;金黄色葡萄球菌对青霉素、磺胺异噁唑、氨苄西林、阿莫西林/克拉维酸的耐药性相对较高;大肠杆菌对氨苄西林、头孢噻吩、磺胺异噁唑存在明显的耐药性。     

Bacterial flora and risk of infection of the ovine teat duct and mammary gland throughout lactation

We collected samples of teat duct material and mammary secretion from ewes in three farms (flock A, polyparous n = 7; flock B, polyparous n = 6, primiparous n = 4; flock C, polyparous n = 4): 14 samples immediately after lambing (before sucking of lambs), 244 samples during the suckling period and 156 samples during the milking period. Conventional bacteriological techniques were used. The results were modeled using survival analysis, initially by the Kaplan–Meier method and then by the Cox Proportional Hazards method. Then, we calculated the minimum true risk of an “at-risk” teat or mammary gland being infected and analyzed these data with STATA using the GLLAMM program for Generalised Linear Latent and Mixed Models. During the suckling period, bacteria were isolated from 52 (21%) duct material and 19 (8%) secretion samples; respective results for the milking period were 20 (13%) and 9 (6%). There was an increased risk of duct rather than secretion samples being infected (P < 0.001). There was a significant difference among flocks in isolating bacteria from duct (P < 0.01) or secretion (P < 0.001) samples during suckling period, but not during hand-milking period (P > 0.4 and 0.1, respectively). There were no differences between isolation of bacteria from duct (P > 0.5) or secretion (P > 0.7) samples among primiparous and polyparous animals. Most bacterial isolates were staphylococci. Persistent isolation of the same bacterial species from duct material samples obtained from a particular ewe was recorded with five Staphylococcus spp. and two Mannheimia haemolytica isolates. The results indicate that infections of the teat duct can take place easily; however, not all infections result to infection of the mammary gland. The results support experimental evidence that defence mechanisms of the healthy teat are able to limit the infection. Maintenance of healthy teats contributes to effective defence mechanisms, and coupled with minimal infections of the teat duct, would contribute to the prevention of mastitis in ewes.     

The utilisation of a high level energy/protein diet for lactating Mediterranean buffaloes: Intake capacity and effects on quanti–qualitative milk parameters

The trial was carried out using 14 multiparous buffaloes divided into two groups according to yield in the previous lactation (2653 vs. 2625 kg), number of lactations (4.8 vs. 4.1), live weight (670.6 vs. 657.1 kg), days post-calving (21.6 vs. 23.6 days) and average yield at the on-set of the trial (11.18 vs. 10.90 kg/day). The effects of both feed intake and the quanti–qualitative parameters of the milk yield were evaluated following the ad libitum administration of two diets containing two different forage/concentrate ratios, diet 1 = 48 : 52 (0.94 Milk FU/kg DM, 158.3 g/kg DM of crude protein); diet 2 = 55 : 45 (0.85 Milk FU/kg DM, 144.4 g/kg DM of crude protein). The trial lasted for 114 days, on average from day 23 to 137 of lactation. The dry matter intake for diet 1 was 16.37 kg/day, for diet 2 it was 16.53 kg/day. No significant differences were found with live weight of the animals; however, the buffaloes in group 1 showed gains of 35.0 kg compared to 54.2 kg of those in group 2. A significant difference (P < 0.05) in milk yield favouring group 1 (11.66 vs. 9.42 kg/day) was observed while fat (73.20 vs. 80.08 g/kg) and protein content (43.24 vs. 46.41 g/kg) was higher for group 2. Coagulation data indicated that the milk yield of group 2 showed better coagulation properties (r = 18.35 min, K₂₀ = 3.88 min, A₃₀ = 47.00 mm), than group 1.     

Prevalence of antimicrobial resistance among Salmonella on midwest and northeast USA dairy farms

The objective of this study was to determine the prevalence of antimicrobial resistance among Salmonella isolated from dairy herds in New York, Minnesota, Michigan, and Wisconsin, USA. Serogroup and antimicrobial susceptibility characteristics were determined for Salmonella from cattle and environmental samples collected during August 2000–October 2001 as part of a longitudinal study where 129 herds were visited at 2-month intervals. Salmonella isolates were tested (using a broth microdilution method) for susceptibility to amoxicillin/clavulanic acid, ampicillin, ceftiofur, ceftriaxone, cephalothin, chloramphenicol, ciprofloxacin, gentamicin, kanamycin, nalidixic acid, streptomycin, sulfamethoxazole, tetracycline, and trimethoprim/sulfamethoxazole. Of the 1506 isolates tested for minimum inhibitory concentrations to these 14 antimicrobial agents, 81.2% were pan-susceptible and for most herds (81.6%) the predominant antimicrobial resistance pattern was pan-susceptible. At least 1 Salmonella isolate resistant to 5 or more antimicrobial agents was found on 23.6% of herds. This resistance phenotype was most common among serogroups B and E1 and among samples from calves and farmer-designated sick cows. Resistant samples most frequently exhibited resistance to tetracycline, streptomycin, and/or ampicillin. No samples were resistant to ceftriaxone (though 13 were in the intermediate range), and very few samples were resistant to ciprofloxacin (n = 1), nalidixic acid (n = 5), or trimethoprim/sulfamethoxazole (n = 7).     

Supplementation of dietary enzymes has varying effects on apparent protein and amino acid digestibility in reproducing sows

The effects of two enzyme (Enz) products on ileal and total tract digestibility (ID and TTD) were evaluated in sows (n = 8) fed corn–soybean meal diets. Treatments were: 1) control diet; 2) control + Enz 1 (protease and cellulase activity); and 3) control + Enz 2 (xylanase activity). Ileal and fecal samples were collected at week 6–7 and 12–13 of gestation and week 2–3 of lactation. There were no improvements in digestibility during gestation. The ID% of dry matter (DM: 77.3, 79.3, 81.7) and N (81.2, 82.5, 84.3) as well as TTD% of DM (89.8, 90.7, 90.8) and N (89.0, 90.0, 90.6) during lactation were affected to varying degrees by the enzymes. The TTD of DM (P = 0.05) and N (P = 0.10) were positively affected by Enz 1. The ID of DM (P = 0.01) and N (P = 0.02) as well as TTD of DM (P = 0.05) and N (P = 0.02) were improved by Enz 2. The improvement in ID of N was not associated with any particular amino acids (AA) but represented small increases in ID of 8 of 10 essential AA with Enz 1 (P = 0.04) and 10 of 10 for Enz 2 (P = 0.01). The product containing xylanase activity, in particular, appears to have potential to increase digestibility of nutrients during lactation in sows.     

Postnatal changes in electromyographic signals during piglet growth, and in relation to muscle fibre types

This study uses non-invasive evoked surface electromyography (SEMG) to investigate postnatal muscle development in pigs, and to assess any correlation between recorded signal parameters and muscle fibre types in two different skeletal muscles. Four litters (n = 43) of Large White × Landrace pigs were used. Evoked SEMG measurements were taken on days 2, 5, 14, 26, 60 and 151 post partum from m. Longissimus dorsi (LD) and on days 14, 26, 60 and 151 post partum from m. Biceps femoris (BF). A third of each litter was slaughtered at days 27, 61 and 153 post partum. Biopsy samples for LD and BF were taken to categorize muscle fibre types. For LD there was a significant increase in compound muscle action potential (CMAP) parameters from day 2 to day 5 post partum, whilst for BF significant increases occurred from days 14 to 26 post partum. Fibre type development in both muscles showed a significant decrease in type IIA fibre number (P < 0.001) and an increase in type IIB fibre number (P < 0.001). Analysis of CMAP parameters in relation to fibre type percentages showed significant positive correlations between percentage of type I fibres in BF and CMAP Area (r = 0.71; P = 0.05), SlopeL (r = 0.79; P = 0.02) and Corr Peak (r = 0.78; P = 0.02) and a negative correlation with SlopeT (r = 0.89; P = 0.003) at day 151. A greater CMAP Area and Corr Peak as well as steeper leading and trailing slopes were on the other hand correlated to fewer type IIB fibres.

It is concluded that 1) changes in the evoked CMAP are muscle-specific during early postnatal development in the pig, and 2) in spite of a small sample size, the correlations between CMAP signal parameters and fibre type percentages warrant further investigation.     

金黄色葡萄球菌小菌落突变株感染小鼠乳房炎模型的建立

为了建立由金黄色葡萄球菌小菌落突变株(small colony variants,SCVs)诱发感染乳房炎动物模型,本试验取40只分娩6~8 d的BALB/c小鼠,随机分成8组(n=5),分别为阴性对照、生理盐水组和不同剂量金黄色葡萄球菌SCVs及金黄色葡萄球菌质控菌株(1.0×10³、1.0×10⁴、1.0×10⁵ CFU/mL)试验组,对生理盐水组及各试验组小鼠第4对乳腺注射生理盐水和对应剂量的菌液(50 mL/只),注射后24 h解剖观察病理变化,一侧乳头制作石蜡切片,另一侧研磨后用ELISA检测试剂盒检测组织匀浆上清中的TNF-α含量。结果显示,注射菌液的试验组,小鼠均出现不同程度的临床症状,乳腺出现不同程度的炎性症状和病理变化。同一注射剂量下,金黄色葡萄球菌质控菌株较金黄色葡萄球菌 SCVs病理变化严重,通过SPSS等软件对试验数据进行统计分析后得出,高浓度处理组金黄色葡萄球菌质控菌株的TNF-α表达量极显著高于金黄色葡萄球菌SCVs(P<0.01)。结果表明,金黄色葡萄球菌及其SCVs均可用来建立小鼠乳房炎模型,且金黄色葡萄球菌SCVs引起的情况较其正常株轻微,这一结果为由金黄色葡萄球菌SCVs引起的奶牛慢性乳房炎的预防和控制及其致病机制的研究提供了新的材料和有益的探索,为SCVs与慢性乳房炎更深层次关系的研究奠定基础。     

Estabishment of Mastitis Model in Mouse by Artificial Infection of Staphylococcus aureus Small Colony Variants

In order to establish the mouse mastitis model induced by Staphylococcus aureus small colony variants (SCVs),40 BALB/c mice 6 to 8 days postpartum were randomly divided into eight groups,negative control group,physiologic saline group and six treated groups with different doses (1.0×10³,1.0×10⁴ and 1.0×10⁵ CFU/mL) of Staphylococcus aureus SCVs or Staphylococcus aureus quality control strains.50 μL physiologic saline and Staphylococcus aureus liquid were injected into the forth mammary glands in physiologic saline group and the six treated groups,respectively.All the mice were sacrificed 24 h after treatment.One side of the forth mammary glands was used to make pathological section,the other side was used to detect the concentration of TNF-α in the supernatant.The results showed that mice had different degrees of clinical symptoms in the treated groups,their mammary glands appeared different degrees of inflammatory symptoms and pathological changes.Under the same injected dose,the Staphylococcus aureus quality control strains group pathologic changed more severe than the Staphylococcus aureus SCVs group.The experimental data had been statistically analyzed by using SPSS software,the result showed that the expression of TNF-α of the Staphylococcus aureus quality control strains group were extremely significantly higher than that of Staphylococcus aureus SCVs group with high dose (P<0.01).The results indicated that Staphylococcus aureus and its SCVs could be used to establish the mice mastitis model,and Staphylococcus aureus SCVs caused relatively minor inflammation than the normal strains.The results provided a new research materials and meaningful exploration to research the prevention and control of chronic mastitis cows and its pathogenic mechanism caused by Staphylococcus aureus SCVs,and laid the foundation for studying the deeper relationship between Staphylococcus aureus SCVs and chronic mastitis.     

A model to determine sampling strategies and milk inoculum volume for detection of intramammary Staphylococcus aureus infections in dairy cattle by bacteriological culture

A model was developed to evaluate the effects that methods of obtaining milk samples and culture inoculum volumes had on the sensitivity of microbiological culture to detect Staphylococcus aureus intramammary infections (IMI). An assumption was made that milk from mammary quarters infected with S. aureus only contains bacteria intermittently. A modified sine wave function was used to model this intermittent shedding pattern. Specifications for the components of the shedding cycle used in this function were based on quantitative culture results from 54 experimentally infected S. aureus quarters, sampled daily for a period of 30–49 days. The components of the shedding cycle were length in days, peak number of CFU shed per milliliter of milk, and length of time in the cycle when no shedding occurred. These components were used to estimate the model's predicted distribution of S. aureus CFU ml⁻¹ milk when individual quarter milk samples were cultured for S. aureus. The sensitivity of culture for several sampling methods was then calculated. The model predicted that culture of a single quarter milk sample had a sensitivity ranging from 60 to 87% for detection of S. aureus IMI depending on inoculum volume. Quarter milk samples taken on day 1 and repeated either on day 3 or day 4, and cultured separately using 0.1 ml of milk for culture inoculum, were predicted to have sensitivities of 90–95% and 94–99%, respectively. Other milk-sampling strategies examined included culture of a composite milk sample (equal-volume mixture of milk from four separate mammary quarters ) and pooled milk samples in which samples from different milkings (either quarter or composite samples) were mixed together and then cultured. The range of predicted sensitivities of these other sampling strategies was 30–97%. Factors having the greatest impact on the sensitivity of culture, in order of importance were: the type of milk sample, the volume of milk cultured, and the time interval between repeated milk sample collection strategies.     

The use of purine derivatives/creatinine ratio in spot urine samples as an index of microbial protein supply in Yerli Kara crossbred cattle

Three experiments were conducted to evaluate the use of purine derivatives (PD)/creatinine ratio in spot urine samples as an index of microbial protein supply in Yerli Kara crossbred cattle (YK-C). In Experiment I, response of daily PD excretion to feed intake in YK-C at state farm was measured. In Experiment II, spot urine sampling techniques was applied at state farm and four YK-C bulls were used. In Experiment III, spot urine sampling technique was applied at small-holder farms. There were significant correlations (R² = 0.99) between PD excretion (mmol/day) and digestible organic matter intake (DOMI) (kg/day) in Experiment I, Y = 12.5 (± 0.5) + 19.7 (± 3.5)X (R² = 0.99, n = 16). The equation obtained from Experiment I could be expressed as: Y = − 2.3 (± 0.3) + 0.953 (± 0.06)X, (R² = 0.99, n = 49) where Y is PD excretion (mmol/day) and X is the PDC index. The PDC index was calculated as the molar concentration ratio of PD to creatinine times the metabolic body weight (kg). The corresponding microbial-N values to PDC index of groups I, II and III in developed banding system are 15–25 g/day. Experimentally estimated DOMI was 2.21 ± 0.15 kg/day. Estimated DOMI of groups I, II, and III were 2.8 ± 0.6, 2.6 ± 0.7 and 2.7 ± 0.7 kg/day, respectively. In conclusion, the PDC index in spot urine samples could be used under similar farm condition as an indicator of microbial protein supply in YK-C cattle. Estimated DOMI from PDC index in spot urine samples under defined field conditions may help the development of feeding strategies for YK-C cattle held by small holders.     

Intermittent suckling improves post-weaning feed uptake but does not change functional gut characteristics of piglets

Suckling pigs were separated from their dam for 24 h on day 21 (1 × 24 h fasting, n = 10) or day 21 and 24 (2 × 24 h fasting, n = 10). Pigs in the control group (n = 10) were not fasted before weaning. All pigs were weaned on day 28 postpartum. Feed intake during the first 4 days post-weaning was higher (P < 0.05) for pigs exposed to 1 × 24 h fasting compared with controls. Water consumption was not affected by fasting prior to weaning. The difference in post-weaning feed uptake was not reflected in any clinical traits, intestinal morphology, or activity of digestive enzymes (maltase, dipeptidylpeptidase IV, aminopeptidases A and N; P > 0.15). In conclusion, a short period of fasting prior to weaning can increase post-weaning feed uptake, although this had no clinical impact under the present experimental conditions.     

Pattern of change in the concentration of milk acetone and its association with ovarian activity for pasture-based cows in early lactation

The variation in milk acetone concentration between cows and the resumption of ovarian activity was determined in 68 Holstein–Friesian cows grazing pasture. Cows calved in two groups approximately three weeks apart and were assessed over the first 60 d of lactation.

The largest coefficient of variation (152%) for milk acetone concentration between cows was found in the first week of lactation. This variability in milk acetone concentration was largely explained by a consistent cyclic pattern, in relation to the day of the study, with regular peaks at 21–26 d intervals. These peaks were synchronised between cows, and cows in the second group synchronised with cows in the first group.

Milk acetone peaks greater than 0.4 mmol/L were associated with a significant drop in milk yield, possibly due to energy deprivation around this time. In this respect, liveweight change over the first 60 d of lactation was significantly negatively correlated (r = − 0.29, p < 0.05) with the mean milk acetone concentration taken over the same period. However, there was no significant relationship (p > 0.05) between mean or maximal milk acetone concentration and the resumption of ovarian activity for the cows that resumed ovarian activity in the first 9-weeks post-partum.

The results of this study suggest that the use of milk acetone as a practical indicator of energy balance is limited due to its variability over time. Milk acetone concentration may be useful in experimental situations or when regular milk samples can be obtained in the field, such as in-line analysis. There is a need to undertake more research to elucidate the implications of the cyclic pattern of acetone concentration in milk on reproductive performance.     

Udder health and risk factors for subclinical mastitis in organic dairy farms in Switzerland

A study was performed in 1997 to estimate the prevalence and to investigate the etiology of subclinical mastitis in Swiss dairy herds managed under guidelines of controlled organic farming. It was planned as a longitudinal study over a period of 1 year and included a stratified random sample of 152 certified organic farms and 1907 cows. Two farm visits (the first from June to October when cows were on pasture, the second from January to March when cows were confined to barns) were performed on each farm. At each visit, farm management and individual-cow data (with emphasis on milking procedures and udder sanitation) were recorded. California mastitis tests (CMTs) were performed on each udder quarter of all cows in lactation. Milk samples with CMT >1+ were submitted for somatic cell counting (SCC), bacteriological examination and to test for antibiotic susceptibility. The SCC and germ-cell counts of monthly bulk-tank milk samples were available through Dairy Inspection and Advisory Services and milk production data of 567 herd-book cows were available from breeding associations. Possible individual and environmental predictors of subclinical mastitis were identified using logistic models adjusted for clustering of the data at herd and cow levels. Data were analyzed separately for cows from 7 to 100 and from 101 to 305 days post partum. Prevalences of subclinical mastitis at the quarter level were 21.2% for lactation period 7–100 days and 34.5% for 101–305 days post partum. The geometric mean SCC in bulk-tank milk samples was 85.6×10³ cells/ml. Samples at 7–100 and 101–305 days post partum were positive for Staphylococcus aureus in 16.0 and 7.4%, for coagulase-negative Staphylococci in 51.5 and 50.6%, for Streptococcus agalactiae in 0.0 and 0.8%, for other Streptococci in 19.4 and 15.6%, for E. coli in 1.0 and 0.4%, and for Corynebacterium bovis in 25.7 and 45.1%, respectively. Risks of subclinical mastitis increased significantly with increasing days post partum and advancing age of cow. Cows that were sampled when staying in alpine dairies had considerably higher risks of subclinical mastitis than cows staying in home barns. Significantly lower risks of subclinical mastitis were observed in farms where CMT was performed regularly as a control measure. Bacteria in milk from cows with mastitis exhibited antibiotic resistance at a comparable frequency as found previously in conventional farms.