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Palmerston North, New Zealand

Grace N.D.,26 Williams Road | Knowles S.O.,Agresearch Ltd. | West D.M.,Massey University | Smith S.L.,Massey University
New Zealand Veterinary Journal | Year: 2012

AIM: To determine how the concentration of Cu in liver affects the rate of depletion of that Cu when cows are fed a Cu-deficient diet under experimental conditions, and to mathematically model the rate of depletion of Cu over time.METHODS: In June 2010, 25 non-lactating Friesian cows were assigned to three groups such that initial mean concentrations of Cu in liver were 265, 534 and 1,486 μmol Cu/kg fresh tissue (Day 0). All cows were managed as a single group and fed a Cu-deficient diet of primarily baled silage. No mineral Cu supplements were given. Liver biopsies were collected from cows on Days 0, 53, 98 and 161 to determine concentrations of Cu. At about the same time, samples of silage and pasture herbage were collected to determine Cu, Mo and S concentrations.RESULTS: Median concentration of Cu in silage was 6.5 (min 6, max 9) mg/kg DM. Concentration of Cu in liver decreased in all groups (p<0.001), over the duration of the study. The amount of Cu depleted from liver was greater in groups that started the study with higher initial concentrations of Cu in liver. The rate of decline followed exponential first-order kinetics with an elimination rate constant k of 0.0057 (CI 95%=0.0039-0.0074), meaning that about 0.57% of liver Cu reserves were depleted each day. For individual cows this loss amounted to 0.1-14 μmol Cu/kg liver/day. CONCLUSIONS AND CLINICAL RELEVANCE: Depletion of Cu from liver was dependent on initial concentration of Cu. These results can be used to predict how long an unsupplemented herd will remain in adequate Cu status, which adds confidence to decisions about when Cu supplementation should be withdrawn or reinstated. Cows with high concentrations of Cu in liver can maintain adequate Cu status for months without supplements. Intake of less Cu and more Mo would increase the rate of depletion, and seasonal factors would also have some influence. © 2012 Copyright Taylor and Francis Group, LLC. Source


Grace N.D.,26 Williams Road | Knowles S.O.,Agresearch Ltd.
New Zealand Veterinary Journal | Year: 2012

AIM: To determine the concentrations of vitamin B 12 in serum, liver and milk that identify adequate vitamin B 12 status in grazing lactating cows, based on no change in milk production in response to supplementation with vitamin B 12.METHODS: In October 2005, in early lactation, Friesian cows from one herd were injected S/C with 60 or 90 mg long-acting vitamin B 12, or no injection (Control; n=39 per group, Day0). Pasture samples were collected for Co determination at monthly intervals over 82 days. Concentrations of vitamin B 12 in milk and serum (n=10 per group) and in liver (n=5 per group) were assessed over 124 days. Milk production and composition were determined on four occasions for all cows.RESULTS: Mean concentrations of Co in pasture ranged from 0.11 to 0.34 mg/kg dry matter (DM). Mean initial concentrations of vitamin B 12 in milk, serum and liver were 1,520, 128 pmol/L and 1,092 nmol/kg fresh tissue, respectively. Administration of 60 and 90 mg vitamin B 12 had similar effects and increased concentrations of vitamin B 12 in milk by 3-fold over controls on Day 50 (7,410 vs. 2,350 pmol/L; p<0.001) and 1.6-fold on Day 124 (3,470 vs. 2,210 pmol/L; p=0.011). Treatment with 60 and 90 mg vitamin B 12 increased concentrations of vitamin B 12 in serum, by at least 5-fold over controls on Day 50 (880 and 1,040 vs. 160 pmol/L; p<0.001). The two treatments increased concentrations of vitamin B 12 inliver by only 1.5 fold over controls on Day 50 (1,660 and 1,900 vs. 1,200 nmol/kg fresh tissue; p<0.005). Treatment had no effect at any sampling time on daily milk volume or milk solids, fat or protein percentages.CONCLUSIONS: Concentrations of vitamin B 12 in serum >128 pmol/L indicated adequate vitamin B 12 status in grazing lactating cows. Supplementation with 60 or 90 mg vitamin B 12 increased and maintained concentrations of vitamin B 12 in serum for up to 124 days, but there was no effect on milk production. Milk was enriched in its vitamin B 12 content, which would provide enhanced nutrition for calves or humans. Compared with 60 mg, the larger dose provided little additional benefit.CLINICAL RELEVANCE: Long-acting injectable vitamin B 12 used to treat and prevent vitamin B 12 deficiency is unlikely to improve the milk production of grazing cows when concentrations of vitamin B 12 in serum are >128 pmol/L. © 2012 Copyright Taylor and Francis Group, LLC. Source


Hittmann A.R.,VetFocus | Grace N.D.,26 Williams Road | Knowles S.O.,Agresearch Ltd.
New Zealand Veterinary Journal | Year: 2012

AIM: To monitor the consequences of withdrawing mineral Cu supplements from two dairy herds with initially high concentrations of Cu in liver.METHODS: Two herds were selected from dairy farms in the Waikato region of New Zealand that participated in an earlier survey of Cu supplementation practices and Cu status of dairy cows. The herds were fed pasture, grass and maize silage, plus palm kernel expeller (PKE) containing 25-30 mg Cu/kg dry matter (DM) fed at 2-4 kg/cow/day. No mineral Cu supplements were supplied from January 2009. Pasture samples were collected for mineral analysis in September 2008 and April 2009. Concentration of Cu in liver biopsies from the same 9-10 cows per herd was measured on three occasions between April 2009 and May 2010.RESULTS: Pastures on both farms contained 10 mg Cu/kg DM, 0.1-0.5 mg Mo/kg DM and 3.5-4.0 g S/kg DM. The initial herd mean concentrations of Cu in liver were 1,500 (SD 590) and 1,250 (SD 640) μmol Cu/kg fresh tissue. In the absence of mineral Cu supplements, those mean concentrations decreased over 12 months to 705 (SD 370) and 1,120 (SD 560) μmol Cu/kg fresh tissue, respectively. For cows in the first herd, the rate of depletion of liver Cu reserves was influenced by initial concentration of Cu, such that high concentration led to faster loss according to first-order kinetics.CONCLUSIONS: Mineral Cu supplementation was not necessary over 12 months for two dairy herds with mean concentrations of Cu in liver >1,250 μmol Cu/kg fresh tissue, grazing pastures containing 10 mg Cu/kg DM and concentrations of Mo <1 mg/kg DM. The quantity and particularly the duration of feeding PKE appeared to be a factor in whether or not the herd lost substantial reserves of Cu in liver during the year. However, the Cu status of both herds in this study was more than adequate to support late pregnancy and mating.CLINICAL REVELANCE: Copper status of the herd should be monitored and on-farm management of Cu nutrition should take into account all sources contributing to daily intake of Cu. Where Cu supplementation has been excessive and there is risk of chronic Cu toxicity, mineral Cu supplements may be withdrawn for a period commensurate with the expected rate of liver Cu depletion. © 2012 Copyright Taylor and Francis Group, LLC. Source


Morgan P.L.,Okato Veterinary Clinic | Grace N.D.,26 Williams Road | Lilley D.P.,Okato Veterinary Clinic
New Zealand Veterinary Journal | Year: 2014

CASE HISTORY: A Jersey herd of 350 cows and 70 heifers located in the Taranaki region of New Zealand ceased milking in June 2011. Ten cows died during the subsequent 14 days. For at least 9 months, the cows had received palm kernel expeller (PKE) and molasses supplements. Additional Cu supplementation was provided through the water system. Total Cu intake was calculated to be 400 mg/day/cow.CLINICAL AND PATHOLOGICAL FINDINGS: Half of the cows died suddenly while others presented with anorexia, depression and ataxia, which progressed to recumbency and death after 1 to 3 days. Clinical signs were mild dehydration, cyanosis and firm faeces which were covered in dark blood. Mean concentrations of Cu in liver and kidney in three of the dead cows were 3,900 and 440 μmol/kg fresh weight (FW), respectively. Haemorrhages were observed throughout the alimentary tracts and in muscles, and there were ecchymotic haemorrhages on the epi- and endocardia. The livers were swollen and the gall bladder walls were inflamed.DIAGNOSIS: High concentrations of Cu in the liver and kidney are characteristic findings of chronic Cu toxicity.TREATMENT: The remaining herd was fed 200 mg Mo, as sodium molybdate, per cow per day and all Cu supplements were removed including those provided by the water supply. This reduced mean concentrations of Cu in liver from 3,100 to 1,320 μmol/kg FW within 26 days in the five live animals that were biopsied. There were no further deaths.CLINICAL RELEVANCE: In dairy herds where excessive Cu intakes have resulted in high liver Cu concentrations and caused chronic Cu toxicity, the removal of all Cu supplements and provision of high intakes of Mo (200 mg/cow/day) can markedly reduce liver Cu stores within 4 weeks. © 2013 New Zealand Veterinary Association. Source


Grace N.D.,26 Williams Road | Knowles S.O.,Agresearch Ltd. | Nortje R.,Southern Rangitikei Veterinary Services
New Zealand Veterinary Journal | Year: 2014

AIMS: To determine the vitamin B12 status of dairy calves during their first year of life, and to evaluate the benefits of vitamin B12 supplementation.METHODS: In Experiment I, 20 17-day-old heifer calves from the AgResearch Flock House herd were monitored until 198 days old. On Days 0 and 90 of the study, half of the animals received an injection of microencapsulated vitamin B12 at 0.12 mg/kg bodyweight. All received colostrum, milk replacer and calf meal, with ad libitum access to pasture. At regular intervals the calves were weighed and serum collected for vitamin B12 measurement.In Experiment II at Flock House and the adjacent Landcorp Tangimoana station, 80 150-day-old heifer calves were monitored until 342 days old. On Days 0 and 97, half of the animals received vitamin B12 as per Experiment I. At regular intervals samples were collected from 12 calves per group, to determine concentrations of vitamin B12 in serum.RESULTS: Mean concentration of vitamin B12 in milk replacer was 63 (SE 4) μg/kg dry matter (DM). Cobalt concentrations in calf meal were 0.45-1.58 and 0.07-0.28 mg/kg DM in pastures. From 17 to 198 days of age (Experiment I) mean concentrations of vitamin B12 in serum of the control group decreased from 119 (SE 8) to 57 (SE 5) pmol/L. From 150 to 342 days of age (Experiment II), overall mean concentrations of the control groups at Flock House and Tangimoana were 90 (SE 2) and 96 (SE 3) pmol/L, respectively. Vitamin B12 injections increased (p<0.001) serum concentrations for at least 90 days, with peak concentrations of 323 (SE 23) (Experiment I) and 520 (SE 22) (Experiment II) pmol/L reached 28-35 days after each injection. Liveweight gain was not increased by supplementation and there was no difference in final liveweight between groups.CONCLUSIONS: Concentrations of vitamin B12 in serum of unsupplemented calves prior to weaning indicated their vitamin B12 status was adequate due to the vitamin B12 and Co content of the milk replacer, and calf meal. Concentrations decreased during the transition to a pasture-based diet. Supplementation increased concentrations of vitamin B12 in serum but did not improve liveweight gains.CLINICAL RELEVANCE: Under this calf rearing system, vitamin B12 deficiency is unlikely to occur prior to weaning, and vitamin B12 supplementation is unlikely to increase growth rates of grazing calves when concentrations of vitamin B12 in serum are >90 pmol/L. © 2014 New Zealand Veterinary Association. Source

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