Associations between management practices and colostrum quality on New Zealand dairy farms

Abstract

AIMS: To describe colostrum quality in spring-calving dairy herds in New Zealand, in terms of Brix, pH and total and coliform bacterial counts and to investigate associations between farm management practices and these measures of colostrum quality.

METHODS: In June 2015, commercial dairy farms (n=105), located in North and South Islands of New Zealand, were visited shortly after the first cows had calved, and when approximately 50% and 80% of the herd had calved (early, middle and late visits). One litre of pooled colostrum that was being fed to newborn calves was collected at each visit and used to determine Brix, pH, total bacterial and coliform counts. A survey of calf management practices was conducted with the herd manager or calf rearer after the final visit.

RESULTS: Of 298 pooled colostrum samples tested 29/298 (9.7%) had Brix >22%. Brix was higher on farms where calves were picked up twice daily compared with once daily (18.2 (95% CI=16.5–19.9)% vs. 15.9% (95% CI=15.2–16.6)%; p=0.012), and was lower where first milking colostrum was combined with colostrum obtained at later milkings (15.0 (95% CI=13.9–16.1)%) compared with where it was not (16.9 (95% CI=16.3–17.6)%; p=0.002). Vaccination of all cows against calf diarrhoeal pathogens was associated with increased Brix compared with no vaccination (18.1 (95% CI=16.6–19.6)% vs. 16.3 (95% CI=15.6–17.0)%; p=0.033). Mean pH of samples tested decreased from 5.97 (95% CI=5.84–6.09) to 5.58 (95% CI=5.45–5.71) for early and late-season visits, respectively (p<0.001). Of 268 samples tested, 23 (8.6%) had bacterial counts below the recommended threshold of 1.00×10⁵ cfu/mL. Mean bacterial counts increased from 2.75 (95% CI=1.80–3.70)×10⁸ to 4.99 (95% CI=3.95–6.03)×10⁸ cfu/mL for early and late-season visits, respectively (p<0.001). Of 259 samples tested, 23 (8.9%) had coliform counts below the recommended threshold of 1.00×10⁴ cfu/mL.

CONCLUSIONS AND CLINICAL RELEVANCE: On a large majority of dairy farms included in this study the pooled colostrum fed to newborn calves had sub-optimal Brix and excessive bacterial counts. Farm-level risk factors such as twice daily pick up of calves from the paddocks, herd vaccination and feeding pooled colostrum that did not combine colostrum obtained at later milkings with first milking colostrum were associated with colostrum quality measures.     

Factors associated with colostrum quality in individual cows from dairy herds in the Waikato region of New Zealand

AIMS: To examine associations between various cow-level factors and quality of first-milking colostrum (measured as Brix), and to evaluate herd-level associations between vaccination against calf diarrhoea and colostrum quality, in cows from dairy herds in the Waikato region of New Zealand.

METHODS: A single colostrum sample was collected, by complete udder evacuation, from each of 20 cows from 29 dairy herds in the Waikato region of New Zealand during the 2016 spring calving period. Vaccination pre-partum with a calf diarrhoea vaccine was used in 15 herds. Each colostrum sample was tested using a digital Brix refractometer. The body condition score of each cow was recorded at the time of sample collection and farmers provided records of clinical mastitis and facial eczema from the previous 12 months, as well as the age and breed of cows. Associations between cow-level variables in non-vaccinated herds and Brix were examined using a multivariable linear mixed model and estimated marginal means obtained for different categories.

RESULTS: Mean Brix of 281 samples from cows in non-vaccinated herds was 18.7 (SD 0.26)%; 63/281 (22.4%) samples had Brix ≥22% and 152/281 (54.1%) had Brix ≥18%. Mean Brix of colostrum samples from cows aged ≥6 years (20.2 (95% CI=19.1–21.2)%) was higher than for samples from 2-year-old cows (18.6 (95% CI=17.3–19.9)%) (p=0.005). Colostrum that was collected at the first milking on the day of calving had higher Brix (20.0 (95% CI=19.1–20.9)%) than colostrum collected from cows that calved the previous day (17.5 (95% CI=16.5–18.4)%) (p<0.001). Mean Brix of colostrum samples from cows which produced ≥8?L (18.2 (95% CI=17.1–19.2)%) tended to be lower than from cows which produced <8?L first-milking colostrum (19.1 (95% CI=18.3–20.0)%) (p=0.08). Among vaccinating herds, 9/15 (60%) had ≥60% colostrum samples with Brix ≥18% compared with 4/14 (29%) of non-vaccinating herds (p=0.04).

CONCLUSIONS AND CLINICAL RELEVANCE: Colostrum quality, as measured by Brix, was associated with the total volume of first-milking colostrum, interval from calving to colostrum collection and cow age. Vaccination against calf diarrhoea was associated with a higher proportion of colostrum samples with adequate Brix. Careful selection of colostrum donor cows should ensure newborn calves are fed adequate quality colostrum which should be beneficial in preventing failure of passive transfer of IgG. Testing of colostrum from individual cows with a Brix refractometer is advocated for the selection of colostrum for feeding newborn calves.     

Calf and colostrum management practices on New Zealand dairy farms and their associations with concentrations of total protein in calf serum

AIMS: To gather information on management practices and farmer attitudes to management of cows and calves during the immediate post-partum period on dairy farms in New Zealand, and to assess these practices for associations with concentrations of total protein (TP) in serum of calves 1–8 days-old.

METHOD: Between July and September 2015 blood samples were collected from calves aged between 24 hours and 7 days, from dairy farms (n=105) in nine areas in New Zealand, on three occasions throughout the calving period. Concentrations of TP were determined in all serum samples. At each visit technicians collected 1?L of the pooled colostrum that was intended for feeding to newborn calves that day. These samples were assessed for Brix, coliform and total bacterial counts. After the last sampling visit, the calf rearer or farm manager were asked to complete a questionnaire describing calf and colostrum management practices on the farm. Potential farm-level variables associated with concentrations of TP in serum of sampled calves were identified using univariable and multivariable linear mixed models.

RESULTS: Mean concentration of TP in serum of calves across all farms was 59.8 (95% CI=59.4–60.2) g/L, and was associated with region and herd size in the final multivariable model. Concentrations of TP were lower in calves from farms in Otago (56.2 (95% CI=53.4–58.9) g/L) and Southland (56.9 (95% CI=54.1–59.7) g/L) compared to calves on farms in the Far North (62.6 (95% CI=59.8–65.3) g/L), and were lower in calves from farms with a herd size >600 (58.3 (95% CI=56.7–59.8) g/L) than ≤600 (61.3 (95% CI=60.1–62.5) g/L) cows. After accounting for fixed effects, farm accounted for only 8.4% of the unexplained variation. There was no association between any of the measures of colostrum quality and concentrations of TP in serum (p>0.2).

CONCLUSION AND CLINICAL RELEVANCE: Very few herd-level variables were associated with concentrations of TP in serum. Risk factors that have been shown to be of importance in previous studies outside New Zealand were not identified as important in the current study. It is possible that, in the situation where calves are kept at pasture with their dams for prolonged periods, variables which influence how well a cow can feed its calf in the first 12–24 hours have a larger influence on concentrations of TP in serum than the collection and management of calves once they reach the rearing shed.     

Effect of oral administration of colostrum on inflammation in the udders of dairy cows suffering from mastitis

The present study was undertaken to examine whether oral administration of colostrum to mastitic cows reduced inflammation in the udder. Fifty milliliters of a colostrum whey product was administered orally daily for 3 days to cows suffering from mastitis. Milk was collected on day 0 and 7 of colostrum administration. For Experiment 1, milk from 11 udder quarters with high somatic cell counts (SCC) in four cows was used. SCC in milk decreased significantly after colostrum administration, whereas colostrum administration increased sodium and IgA concentrations significantly compared with those before administration. In Experiment 2, cows with clinical mastitis were divided into two groups, with and without colostrum administration, whereas all cows with subclinical mastitis were administered colostrum. Antibiotics were infused into the mammary gland from the first day of colostrum administration for 2–4 days. There was no significant decrease in SCC after colostrum administration in any group. However, udder firmness in both clinical mastitis groups was reduced after administration regardless of colostrum administration. IgA concentration in both clinical mastitis groups was significantly increased after colostrum administration compared to that before administration, although there was no significant difference between them. These results suggest the possibility that oral administration of colostrum attenuates inflammation of the mammary gland. Further studies are required to examine the effect of colostrum more precisely using cows with subclinical and chronic mastitis and longer duration of colostrum administration.     

Risk factors for and reproductive outcomes of phantom cows on New Zealand dairy farms

AIMS: To determine some of the risk factors for cows not observed in oestrus within 35–42 days of an unsuccessful artificial insemination (AI; phantom cows), and the reproductive outcomes and effect of treatment of phantom cows.

MATERIALS AND METHODS: Over 2 years, in dairy herds from the Waikato (n=10) and Canterbury (n=4) regions of New Zealand, pregnancy diagnosis was carried out 35–42 days after AI on cows that had been inseminated in the first 3 weeks after the start of mating (PSM) but had not been seen returning to oestrus. Risk factors for phantom cows were analysed using a generalised linear mixed effect model.

In Year 1, all phantom cows were left untreated. In Year 2, phantom cows were categorised as having a corpus luteum (CL) (CL+ n=120), or having ovarian follicles ≥10 (n=101) or <10 (n=40)?mm in diameter. Cows with a CL were treated with cloprostenol or untreated and placed with bulls. Cows with no CL received intravaginal progesterone (P4) for 7 days, with injection of gonadotrophin-releasing hormone (GnRH) on Days 0 and 9, and cloprostenol on Day 7 followed by AI. Pregnancy diagnosis of all cows took place 100–120 days after PSM and interval to conception and final pregnancy rate determined.

RESULTS: Overall, of cows inseminated in the first 3 weeks after PSM that did not return to oestrus, 610/6,734 (9.1%) were phantom cows. From the final multivariable analysis, treatment for anoestrus, BCS ≤4.0 at mating, being 2 or >6 years of age, and pure-bred, and decreasing interval between calving and mating, until 98 days post calving, were associated with increased odds of being a phantom cow. Compared to all other groups of cows, phantom cows had a longer interval to conception (p<0.001) and a lower final pregnancy rate (p<0.001).

Treatment of CL+ cows or cows with follicles ≥10?mm did not affect reproductive outcomes (p>0.3). For cows with follicles <10?mm treatment decreased the final percentage not pregnant (3/27; 11%; p=0.01) and interval to conception (21 days; p=0.02) compared with controls (7/13; 54% and 37 days, respectively).

CONCLUSIONS AND CLINICAL RELEVANCE: Risk factors for phantom cows were identified that could be manipulated to reduce the number of phantom cows in a herd, in particular increasing BCS. Treatment of the majority of phantom cows did not improve reproductive performance.     

Evaluation of the transfer of immunoglobulin from colostrum anaerobic fermentation (colostrum silage) to newborn calves

Colostrum silage is an anaerobic fermentation methodology of excess farm colostrum used to conserve and provide as milk replacement for calves. The present study aimed to evaluate the levels of immunoglobulins present in bovine colostrum silage and its absorption by newborn calves. The concentration of immunoglobulins was determined in fresh colostrum and colostrum silage stored for 12 months. The absorption of immunoglobulins by calves was assessed immediately after birth and 24 h after colostrum silage intake. The immunoglobulin levels were evaluated by ELISA. The results highlighted that colostrum silage kept similar levels of immunoglobulins as the ones in colostrum in natura, and can be transferred to newborn calves with similar amounts to calves fed with colostrum in natura. It is concluded that colostrum silage keeps viable immunoglobulins, and is able to transfer passive immunity to newborn calves.     

The impact of direct‐fed microbials and enzymes on the health and performance of dairy cows with emphasis on colostrum quality and serum immunoglobulin concentrations in calves

Thirty‐six cows were blocked by calving date and randomly assigned to one of three treatments. Cows were on treatments 3 weeks prepartum through 8 weeks post‐partum. Treatments were as follows: (i) no direct‐fed microbial (DFM) or cellulase and amylase enzymes (C), (ii) 45.4 g/day of DFM (D) or (iii) 45.4 g/day of DFM and 18.2 g/day of enzyme (DE). Total mixed ration fed and refused were measured daily to determine dry matter intake (DMI). Blood samples were taken three times weekly and analysed for β‐hydroxybutyrate, glucose and non‐esterified fatty acids. Body weight (BW) was measured weekly. Colostrum was weighed and analysed for IgA and IgG concentration. Calves were fed 4 L of colostrum within 2 hr of birth. Calf blood samples were taken at 0 and 24 hr for analysis of IgA and IgG concentrations and apparent efficiency of absorption. Milk yield was measured daily and samples collected weekly. Initial BW was different among treatments with D being lesser than C or DE treatments. Body weight, weight gain, efficiency of gain, DMI and blood parameters were unaffected. Treatment did not affect colostrum yield. Ash percentage of colostrum tended to increase with D and DE, while IgA and total solids yield decreased with D. Colostrum fat yield was decreased in D and DE. Treatments did not impact BW, serum IgA and IgG concentrations or apparent efficiency of absorption of calves. Post‐partum BW, DMI, blood parameters, milk production and composition were unaffected by treatment. However, cows on D gained more BW and tended to have greater efficiency of gain compared to those on DE, but were similar to C. Somatic cell scores were greatest for D. Results indicate that DFM and enzyme supplementation did not improve health and performance of dairy cattle during the pre‐ and post‐partum periods under conditions of this study.     

Effects of Rosmarinus officinalis L. essential oils supplementation on digestion,colostrum production of dairy ewes and lamb mortality and growth

The aim of this study was to evaluate the effect of rosemary essential oils (REO) and the forage nature on ewes' performances, immune response and lambs' growth and mortality. Forty‐eight dairy ewes (Sicilo‐Sarde) were fed oat‐hay or oat‐silage supplemented with 400 g of concentrate during pregnancy and 600 g during postpartum. The experimental concentrate contained the same mixture as the control (barley, soybean meal and mineral vitamin supplement) more 0.6 g/kg of REO. Two groups were obtained with each forage (Hay groups: H‐C and H‐REO; Silage groups: S‐C and S‐REO). REO increased the dry matter (DM) intake, the nitrogen intake and retention being higher with the silage groups (P < 0.05). REO increased solid non‐fat (P = 0.004) and fat contents of colostrum which was higher with hay (P = 0.002). REO decreased lamb mortality (P < 0.05) which averaged 21% for control groups and 6% for H‐REO, while no mortality was recorded with S‐REO. REO dietary supply improved forage intake and tended to ameliorate colostrum production; it could be a natural additive to improve ewes' performances.     

Blood metabolites and body temperature of single calves between 1 and 4 days of age in a dairy herd in New Zealand

AIM: Using specified indices, to determine the nutritional and thermal status of calves between 1 and 4 days of age.

METHODS: After birth, calves (n=106) were collected daily, according to farm practice. Over the following 4 days a jugular blood sample and rectal temperature were taken twice daily before feeding. Plasma concentrations of glucose, beta-hydroxybutyrate and urea, and gamma-glutamyl transferase (GGT) activities were determined. The significance of differences in plasma composition and rectal temperature between calves whose birth had been assisted or unassisted, and between calves with low and high plasma GGT activities 24 h after birth, was determined using repeated measures analysis of varianc

RESULTS: There were no marked differences in plasma metabolite levels or body temperature of assisted and unassisted calves. Calves that had high plasma GGT activities 24 h after birth had higher plasma glucose concentrations over the 4 days than calves that had low plasma GGT activities (p<0.001). Overall, compared to published data on poorly-fed and hypothermic calves, calves in this study were normoglycaemic, their plasma beta-hydroxybutyrate and urea concentrations were low and their rectal temperatures were normal, indicating that they were well fed and did not become hypothermic.

CONCLUSIONS: The nutritional and thermal status of at least 90% of the calves was compatible with good health and survival during the first 4 days after birth.     

The transmission of thermotolerant Campylobacter spp. to people living or working on dairy farms in New Zealand

New Zealand has one of the highest rates of campylobacteriosis in the developed world with an incidence rate of 383.5 cases per 100,000 in 2006. Dairy farming has been suggested as a potential source of campylobacteriosis. To explore this connection, seven farm investigations were undertaken at dairy farms on which a campylobacteriosis case had been notified. Campylobacter spp. were isolated from a range of sources on the farm (including 66% of bovine faecal samples) and genotypes compared with that of the clinical isolate of the index case. In depth, epidemiological questionnaires were also administered to determine exposure risks from a wide range of possible sources. Contact with dairy cow faeces was the most likely source of infection in four of the seven cases investigated, and occurred exclusively in new farm workers and children. In one of the cases investigated, infection was likely to have been acquired from non-dairy related sources, and in two cases the source could not be determined. The relative risk of dairy farm worker being notified with campylobacteriosis was estimated to be 1.88 (95% confidence interval=1.6-2.2).     

Influence of colostral quality on serum proteins in dairy calves raised in smallholder farms in Thailand

The objective of this study was to analyze the influence of colostral quality on serum proteins in calves. Samples were collected from visited farms in Kasetsart University Veterinary Teaching Hospital at Kamphaeng Saen and Nong Pho Animal Hospital. In total, 35 dairy farms contributed 80 dams and calves’ samples. Colostrum samples from 80 dairy cows and blood samples from their calves were taken to evaluate colostral immunoglobulins (Ig) and immunoglobulin G (IgG), and calf serum protein and IgG. Total colostral Ig, colostral and serum IgG, and serum protein were measured by a colostrometer, single radial immunodiffusion, and refractrometer, respectively. Immunoglobulin G and serum protein concentrations increased in the 1st day after birth, and maximum concentrations were seen in the 2nd day and then decreased in the 7th and 14th days. Average?±?SD total colostral IgG concentrations at calving date and at 1 and 2 days after calving were 93.85?±?33.89, 37.11?±?23.51, and 17.23?±?9.4 mg/mL, respectively. The profile of total Ig and IgG concentrations in colostrum had a similar pattern, with the maximum concentrations obtained in calving date and rapidly decreased thereafter. Low IgG concentrations were seen in the 7th and 14th day after calving. The calves that were fed with high quality colostrum had higher serum protein at 1 day of age, 7.49?±?1.01 g/dL, than calves fed with low quality colostrum, 6.40?±?0.86 g/dL (P?<?0.01). The increase in serum protein after first colostrum feeding of high and low quality colostrum was 1.55?±?1.07 and 0.81?±?0.69 g/dL, respectively (P?=?0.02).     

Applying animal-based welfare assessments on New Zealand dairy farms: feasibility and a comparison with United Kingdom data

AIMS: To assess the feasibility of applying animal-based welfare assessments developed for use in Europe on New Zealand dairy farms; in particular, to identify measures which could be evaluated during a single visit at milking time alongside whole herd locomotion scoring.

METHODS: A protocol for animal welfare assessment, developed in the United Kingdom (UK), was evaluated. Measures that were suitable for use on pasture-based dairy farms in New Zealand were then assessed for practicability on 59 farms across New Zealand, during and immediately after milking, alongside whole herd locomotion scoring. Where data were collected the results were compared to those from a UK study of 53 dairy farms.

RESULTS: Thirteen observations of the physical condition of cows were considered suitable for measurement, excluding observations related to hock lesions as they are rarely observed on pasture-based farms. Five of these measures were not assessed as there was not time to do so during milking alongside whole herd locomotion scoring. Thus, the prevalence of dirty flanks, hind limbs and udders, dull coat, thick hairy coat, significant hair loss, very fat cows (body condition score (BCS) ≥7 on 1–10 scale) and very thin cows (BCS≤3), were recorded. Three measures of behaviour were considered suitable for measurement on-farm, but only locomotion score was practicable and was measured. Farmer-estimates for the incidence of mastitis, lameness, sudden death, milk fever and other diseases were also obtained.Overall, dirty flanks, dirty udders and estimated milk fever incidence were more prevalent in this study than in the UK. The prevalence of thin and fat cows, lame cows and estimated mastitis incidence were much lower in the present study than on UK farms.

CONCLUSIONS AND CLINICAL RELEVANCE: Animal-based assessments can be used on dairy farms in New Zealand, but need to be modified from those developed for housed cows.Welfare on these farms was generally good compared to those in the UK, but these results need to be confirmed on more farms using a wider range of assessments than proved practicable in this study.     

Effect of quality of colostrum on health,growth and immunoglobulin G concentration in Holstein calves in a hot environment

The aim of this study was to determine the effect of ingestion of pasteurized and subsequently frozen–thawed pooled colostrum (≥50 mg Ig/mL) with different bacterial counts and immunoglobulin concentration (IgC) on the occurrence of diarrhea and pneumonia in 306 neonatal Holstein calves in a hot environment. Calves were assigned to be fed colostrum with total bacterial counts (TBC) lower or greater than 100 000 colony‐forming units (cfu)/mL, total coliform counts (TCC) greater or lower than 10 000 cfu/mL, and IgC lower or higher than 85 mg Ig/mL. Calves fed colostrum with TBC ≥100 000 cfu/mL were more likely (risk ratio 1.34, confidence interval 1.05–1.71; P < 0.05) to present pneumonia than calves receiving colostrum with lower TBC (incidence 53.2 vs. 39.8%). Calves fed colostrum with high TCC had increased chances of suffering pneumonia (51.4 vs. 42.1%; P < 0.05) than calves fed colostrum with lower TCC. Calves fed colostrum with ≥85 mg Ig/mL tended to present higher daily weight gain (505 ± 113 vs. 484 ± 126 g; P = 0.09). TBC and TCC in colostrum did not influence the incidence rate of diarrhea. It was concluded that under the conditions of the present study, heavy contamination of on‐farm pasteurized frozen–thawed colostrum is seemingly unavoidable and this contamination poses a threat for pneumonia, but not for diarrhea.     

Prevalence of anthelmintic resistance on sheep farms in New Zealand

AIM: To establish the prevalence of anthelmintic resistance in parasitic nematodes on sheep farms in New Zealand.

METHODS: A cross-sectional prevalence study was conducted, using a standardised faecal nematode egg count (FEC) reduction (FECR) test (FECRT) for ivermectin, at a full (0.2 mg/kg) and half (0.1 mg/kg) dose rate, and albendazole, levamisole and albendazole-levamisole in combination, on 60 lambs (n=10 per group) on farms selected from throughout New Zealand. Farms that conformed with selection criteria were chosen at random (n=80) or with a history of suspected resistance to macrocy- clic lactone (ML) anthelmintics (n=32). Resistance to an an- thelmintic was inferred when there was <95% reduction in FEC 7-10 days after treatment. Larval cultures were performed for all control groups and for treated groups for which resistance was evident.

RESULTS: Of the farms randomly selected, 36% showed ≥95% FECR for all anthelmintics tested; resistance to ivermectin at 0.1 and 0.2 mg/kg liveweight was evident on 36% and 25% of these farms, respectively. Resistance to both ivermectin (0.2 mg/kg) and levamisole was evident on 8/80 (10%) farms, to ivermectin and albendazole on 10/80 (13%) farms, and to iver- mectin, levamisole and albendazole on 6/80 (8%) farms. The prevalence of resistance to a half dose of ivermectin tended to be more prevalent on farms with a history of suspected ML resistance (p=0.06). Resistance to albendazole was seen across all the main parasite genera, and to levamisole in Nematodirus, Ostertagia (= Teladorsagia) and Trichostrongylus species. Resistance to ivermectin was dominated by Ostertagia spp, although Cooperia, Nematodirus and Trichostrongylus species were also implicated.

CONCLUSION: Anthelmintic resistance in parasitic nema-todes of sheep is common in New Zealand. Not only was resistance to albendazole and levamisole common, but resistance to the ML, ivermectin, was at a higher prevalence than expected. Sheep farmers and advisors in New Zealand need to re-evaluate the way they manage parasites, and more research is urgently needed if the steady decline in anthelmintic susceptibility is to be halted.     

Reduction of the prevalence of footrot on New Zealand farms by vaccination

AIM: To compare serum analyses of vitamin B₁₂ and methylmalonic acid (MMA) as indices of cobalt/vitamin B₁₂ deficiency in lambs around weaning.

METHODS: Lambs on five properties, considered to be cobalt- deficient, were supplemented with either cobalt bullets, or short- or long-acting vitamin B₁₂ preparations. Blood samples, and in some cases liver biopsies, and liveweights were obtained at monthly intervals. Serum samples were assayed for vitamin B₁₂ and MMA and liver for vitamin B₁₂ concentrations. Pasture cobalt concentrations were measured on three of the properties.

RESULTS: Pasture cobalt concentrations were generally maintained below 0.07 μg/g dry matter (DM) on the properties sampled. Growth responses to supplementation were observed on only 2/5 properties, despite serum vitamin B12 concentrations being within the currently used ’marginal‘ reference range (336–499 pmol/L) for at least 3 months on all properties and in the deficient reference range (0–335 pmol/L) for at least 2 months on all farms except one. Serum MMA concentrations in supplemented lambs were <2 μmol/L, except in those animals sampled 1 month after receiving treatment with a short-acting vitamin B12 injection. Serum MMA concentrations in unsupplemented animals on properties on which no growth response to supplementation occurred generally reached peak levels of between 4 and 7 μmol/L at the nadir of serum vitamin B12 concentration. When a growth response was observed, differences in weight gain between supplemented and unsupplemented lambs occurred as mean serum MMA concentrations increased from 9 to 14 μmol/L. On one property where supplementation commenced before weaning, normal growth rates were maintained despite serum vitamin B12 concentrations of 140 pmol/L and serum MMA concentrations in excess of 40 μmol/L serum.

CONCLUSIONS: The possibility that current serum vitamin B₁₂ references ranges for diagnosis of cobalt deficiency are set too high and lead to over-diagnosis of responsiveness to cobalt/ vitamin B₁₂ supplementation is discussed. The suggestion is made that serum MMA concentrations in excess of 9–14 μmol/L will provide a more reliable diagnostic test for cobalt deficiency. However, there was sufficient variation between properties in the relationships between cobalt concentrations of pasture and serum vitamin B₁₂ or MMA concentrations to require more rigorous testing of the reliability of using serum MMA concentration for this purpose. The possibility that differences in rumen fermentation and therefore propionate and vitamin B₁₂ production could be involved is discussed. The measurement of serum MMA and vitamin B₁₂ appears to be of little value whilst the lamb is still suckling.

CLINICAL SIGNIFICANCE: Serum MMA concentration may offer advantages over serum vitamin B₁₂ concentrations in the diagnosis of a cobalt/vitamin B₁₂ responsiveness in weaned lambs.     

Detection of Fusobacterium necrophorum and Dichelobacter nodosus in lame cattle on dairy farms in New Zealand

Lameness in the dairy industry in New Zealand causes a problem in lost production, animal welfare and associated costs. To understand what bacteria may be present on the hooves of lame dairy cattle in this grass-fed system, samples were scraped from lame dairy cows and examined for the presence of Fusobacterium necrophorum (F. necrophorum) and Dichelobacter nodosus (D. nodosus) using the polymerase chain reaction (PCR). The PCR primers were designed to detect the presence of the lktA gene, which encodes a leukotoxin unique to F. necrophorum, and the fimA gene of D. nodosus. A total of 148 hoof scrapings were collected by farm staff over the period September 2005 to May 2006. F. necrophorum was detected in 79/148 of the samples, while D. nodosus was detected in 7/148 of the samples. The frequent finding of F. necrophorum within dairy herds in New Zealand is noteworthy and the occasional finding of D. nodosus on some dairy cattle suggests a possible role in both ovine and bovine hoof pathology.