A practical approach to managing the risks of iodine deficiency in flocks using thyroid - weight: birthweight ratios of lambs

AIM: To establish a protocol for determining the iodine status of a flock and managing the risks of iodine deficiency, using thyroid-weight:birthweight ratios of newborn lambs and serum iodine concentrations of ewes. METHODS: Data were collected from iodine supplementation studies in Southland and Rangitikei, of sheep fed exclusively pasture or pasture plus brassica during the latter half of gestation (n=350, or 89 per treatment group). The ewes were supplemented pre-mating or at the time of pregnancy scanning with an injection of long-acting iodised oil. Serum iodine concentrations were measured in ewes prepartum in Rangitikei and postpartum at both locations. The thyroid-weight:birthweight ratios (as g/ kg) in 229 newborn lambs were determined at post-mortem examination and compared between iodine supplemented vs unsupplemented flocks using probit analysis. Samples of pasture and kale were analysed monthly for determination of iodine and selenium. RESULTS: Initial mean serum iodine concentration of all ewes was 41 mug iodine/L. Supplementation increased serum iodine concentrations regardless of forage fed, and concentrations remained high for between 127 and 206 days. The range of thyroid-weight:birthweight ratios in lambs from supplemented ewes was 0.09-0.70 (mean 0.35, standard deviation (SD) 0.147) g/kg. Among lambs from unsupplemented ewes, the range was much wider (0.21-8.5; mean 1.61, SD 1.95 g/kg). About half of those ratios were >0.8 g/kg and clearly indicative of goitre, including 62% from the groups on brassica and 18% from the Rangitikei group fed exclusively pasture. Probit calculations showed that a ratio of 0.40 (95% confidence interval (CI)=0.29-0.47) g/kg predicted with 35% probability, and a ratio of 0.80 (95% CI=0.70-0.99) g/kg predicted with 90% probability that a lamb came from an unsupplemented flock. CONCLUSIONS: Compared to iodine concentrations in forages, thyroid-weight:birthweight ratios more accurately reflected the iodine status of the flock and could be used to identify which flocks to supplement the following year. Serum iodine concentrations of ewes measured before or after lambing did not reflect forage fed, but values near 40 mug/L were associated with goitrous lambs. CLINICAL RELEVANCE: Thyroid-weight:birthweight ratios >0.8 g/kg were indicative of iodine deficiency, and ewes should be supplemented pre-mating or during pregnancy to prevent goitre the following year. Ratios <0.4 g/kg rarely occurred among deficient flocks, so the probability of benefit from supplementation was low. Intermediate ratios were ambiguous, and the iodine status of the flock could not be determined from biomarkers. In such cases individual-farm supplementation trials might be required to detect and manage the risks of marginal deficiency.     

Dihydrostreptomycin or streptomycin in combination with penicillin G in dairy cattle therapeutics: A review and re-analysis of published data Part 2: Resistance and residues

Combination formulations of penicillin G salts and dihydrostreptomycin were developed during the 1960s and are currently marketed in New Zealand for parenteral and intramammary use in dairy cattle. In this paper, the second part of a two paper series, the mechanisms by which bacteria develop resistance to each of these drugs independently is reviewed and the impact of this resistance on potential for synergy is discussed. Further, the considerable potential for tissue drug residues with dihydrostreptomycin or streptomycin from these formulations is examined by re-analysis of literature data, demonstrating an urgent need to reassess the place for aminoglycoside-containing formulations in dairy cattle therapeutics.     

Epidemiology and diagnosis of subclinical iodine deficiency in crossbred cattle of Punjab.

OBJECTIVE: To determine the prevalence of iodine deficiency in crossbred cows (taurus x indicus) of Punjab and to assess the diagnostic value of the plasma concentrations of thyroid hormones, total cholesterol and free fatty acids in iodine deficiency. The efficacy of ethiodised oil, as a long-term supplement of iodine, was also evaluated. PROCEDURES: Base-line survey of iodine status was conducted by measuring plasma inorganic iodine (PII) concentration in 48 crossbred cows from 31 dairy units. Concentrations of plasma triiodothyronine (T3), thyroxine (T4), total cholesterol and free fatty acids were compared between iodine deficient and normal cows. Circulating T4 and T3 concentrations were also determined before and after injection of ethiodised oil in cows with low PII levels. RESULTS: The mean prevalence of iodine deficiency was 35.9% and showed considerable geographical variation from 0 to 86% within Punjab. Cardinal clinical signs of iodine deficiency were absent and basal plasma T3 and T4 concentrations and their ratio did not differ between deficient and control cows. Activity of circulating T4 and T4:T3 ratio increased in response to ethiodised oil injection and persisted beyond 70 days after injection. CONCLUSION: Asymptomatic iodine deficiency is prevalent in crossbred cows of Punjab and response to iodine supplementation is the most reliable index of thyroid dysfunction associated with iodine deprivation. The results of this study also support the view that injection of 1 mL of 78% ethiodised oil can prevent iodine deficiency for more than 70 days.     

A critical evaluation of serum methylmalonic acid and vitamin B12 for the assessment of cobalt deficiency of growing lambs in New Zealand

AIM: To derive reference ranges for serum methylmalonic acid (MMA) for the diagnosis of cobalt/vitamin B₁₂-responsiveness in lambs and critique existing serum vitamin B₁₂ reference ranges.

METHODS: Individual animal data from earlier supplementation trials, involving 225 ewes, 106 suckling lambs, 301 lambs during the suckling and post-weaning periods and 414 weaned lambs, for which weight gain to supplementation was observed, were used to derive relationships between serum vitamin B₁₂ and MMA, and liveweight gain.

RESULTS: Serum MMA concentrations were rarely elevated above the norm of <2 µmol/L when serum vitamin B₁₂ concentrations were >375 pmol/L, and not elevated into the range where a liveweight response to supplementation occurred (>10 µmol/L) unless serum vitamin B₁₂ concentrations were below 200 pmol/L. Suckling lambs were able to maintain high growth rates despite elevated serum MMA concentrations (>20 µmol/L).

CONCLUSIONS: The current reference ranges used in New Zealand for serum vitamin B₁₂ are set conservatively high. Serum MMA concentrations appear to allow better differentiation of a responsive condition than vitamin B₁₂ concentrations. Serum MMA concentrations <13 µmol/L indicate responsiveness to supplementation whilst concentrations <7 µmol/L indicate unresponsiveness. In the range 7–13 µmol/L, variation in response was observed and predictability of response is less certain, but supplementation is advisable.

CLINICAL RELEVANCE: The current reference ranges for vitamin B₁₂ responsiveness are conservatively high and lead to over-diagnosis of vitamin B₁₂ deficiency in ill-thriftiness of sheep.     

The effect of progesterone supplementation post mating and shearing of ewes in early pregnancy on the reproductive performance of ewes and birthweight of lambs

AIM: To determine whether short-term progesterone supplementation post mating or shearing of ewes in early pregnancy affected either the proportion of ewes that lambed or that had multiple lambs, or the birthweight of lambs.

METHODS: Romney ewes (n=457) were synchronised in oestrus using controlled internal drug-releasing (CIDR) devices containing progesterone, and mated to Romney rams over a 5-day period. The mid-point of mating (Day 0) occurred 2 days after the withdrawal of CIDR devices. Ewes mated (n=397) were randomly allocated to one of four treatment groups: shearing at Day 5, shearing at Day 30, no shearing, and no shearing plus progesterone supplementation using a CIDR device inserted on Day 3 for 6 days. During the period from Day 5 to Day 27, six harnessed Suffolk rams were placed with the ewes and matings recorded. At Day 48, all ewes that did not return to the Suffolk rams were scanned for pregnancy using ultrasound. At Day 140, single- and multiple-bearing ewes were set-stocked at 15.1 and 12.2 ewes/ha, respectively, and equivalent numbers of ewes from each treatment group were placed in each paddock. Blood samples from 10 unshorn and 10 progesterone-supplemented ewes were collected on Days 3, 6 and 9, and analysed for plasma progesterone concentrations. Lambs were identified to their dam and weighed within 12 h of birth, and again at 27 and 93 days after the mid-point of lambing. The ewes were weighed at regular intervals throughout the trial.

RESULTS: Plasma progesterone concentrations of supplemented ewes were higher than those of unsupplemented ewes (3.28 vs 1.75 ng/ml) on Day 6 (p=0.02) but not on Day 9 (4.58 vs 4.63 ng/ml). Treatment of ewes had no effect on either the proportion of ewes which lambed to the synchronised mating period or that had multiple lambs. Lambs born to ewes shorn at Day 30 tended (p=0.09) to be heavier at birth (by 0.28 kg) than those born to unshorn ewes but this effect was not evident when data were corrected for length of gestation. Neither shearing at Day 5 nor progesterone supplementation had any effect on the birthweight of lambs, and the treatment of ewes had no effect on the survival rate of lambs to weaning.

CONCLUSIONS: Progesterone supplementation for 6 days beginning 3 days post mating did not increase either the proportion of ewes that lambed or that had multiple lambs, or the birthweight of lambs. Shearing 5 days after mating had no significant effect on the reproductive performance of ewes and need not be avoided, but is unlikely to result in an increase in lamb birthweight. Shearing ewes at Day 30 may result in an increase in the birthweight of lambs but, ideally, ewes should be further advanced in pregnancy before shearing is undertaken.     

A longitudinal study of the risks for introduction of severe footrot into sheep flocks in the south west of Norway

In 2008, ovine footrot was detected in Norway for the first time since 1948. By December 2012 it had spread to 99 flocks, all in the county of Rogaland in the south west of Norway, and 42% of which were located in the municipality of Rennesøy in Rogaland. The aim of this study was to investigate risk factors for contracting severe footrot in flocks of sheep. A flock was considered positive for severe footrot based on positive virulence test or by clinical signs in addition to a positive PCR test.     

The use of pooled vs serial urine samples to measure urine protein:creatinine ratios

Background: Evaluation of serial urine protein:creatinine (UPC) ratios is important in prognosticating chronic kidney disease and monitoring response to therapeutic interventions. Owing to random biologic variation in dogs with stable glomerular proteinuria, multiple determinations of UPC ratios often are recommended to reliably assess urine protein loss. This can be cost‐prohibitive. Objective: The purpose of this study was to evaluate agreement between the mean of 3 UPC ratios obtained on 3 separate urine samples per dog and a single UPC ratio obtained when aliquots of the separate samples were pooled and analyzed as 1 sample. Methods: Three separate urine samples were collected from each of 25 dogs, both client‐owned and members of a research colony. Protein and creatinine concentrations were measured in the supernatant of each sample using a biochemical analyzer, and the mean of the 3 UPC ratios was calculated. A 1.0 mL aliquot of each of the 3 samples from each dog was pooled to create a fourth sample for that dog, and the UPC ratio of the pooled sample was similarly determined. Agreement and correlation between the mean and pooled UPC ratios were assessed using Bland–Altman difference plots and regression analysis, respectively. Results: The UPC ratio in the pooled samples was highly correlated (r=.9998, P<.0001) with the mean UPC ratio of the 3 separate samples. Strong agreement between results was demonstrated; a UPC ratio from a pooled sample was at most ±20% different than the mean UPC ratio obtained from 3 separate samples. Conclusions: Measuring the UPC ratio in a pooled sample containing equal volumes of several different urine specimens from the same dog provides a reliable and cost‐effective alternative to assessing multiple UPC ratios on several specimens from the same dog.     

Effects of a high-protein, low-energy diet in finishing lambs: 1. Feed intake, estimated nutrient uptake, and levels of plasma metabolites and metabolic hormones

Patterns of tissue mobilisation in ruminants are ill-understood. This hinders nutritional management to mitigate the effects of energy deprivation on protein mass, and nutritional regimens designed to change body composition. An experiment was conducted to comprehensively evaluate the effects of a low-energy high-protein diet in growing lambs. Three diets (CON = concentrate diet ad libitum, STR = straw ad libitum, SFM = straw ad libitum plus 150 g/d fish meal) were fed to growing white-face lambs. Analysis of feed intake and metabolite data provided evidence that greater available N did not have a synergistic effect on intake of low quality forage. Metabolite and hormone profiles of lambs in negative energy balance, supplemented with duodenally available protein, revealed that SFM animals did not respond with an accelerated rate of fat mobilization or maintain protein mass due to available N. This was particularly evident from the leptin profiles, which indicated higher circulating leptin levels for SFM compared to STR animals. Further, the data revealed that in sheep fed below requirements for maintenance, leptin levels did not correspond with acute ME intake, whereas the opposite was true for well-fed animals. Conversely, the response of the GH/IGF-1 axis to high protein–energy ratio (PER) diets was indicative of effects not explained by the difference in energy provided by the two experimental diets.

These results contrast with observations from intra-gastric infusion experiments testing similar PERs and previous conventional feeding trials and provide evidence of: (1) specific differences associated with PER in lambs fed via intra-gastric infusion vs. a conventional feeding approach, and (2) lack of usefulness of high PER diets in the post hoc modification of body composition of growing lambs. While positive N balance is known to occur in ruminants in negative energy balance, the determinants of relative proportions of muscle and adipose tissue catabolised under energy deprivation remain unknown.     

Using sodium molybdate to treat chronic copper toxicity in dairy cows: A practical approach

Abstract

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.     

断奶前补饲不同直/支链淀粉比开食料对羔羊瘤胃上皮发育的影响

为了研究断奶前补饲不同直/支链淀粉比开食料对羔羊瘤胃上皮发育的影响,选取24只体况良好、胎次一致、体重相近的10日龄羔羊(湖羊),将其随机分为3组,在饲喂相同母乳的基础上,分别补饲以纯木薯(CS)、玉米(MS)和豌豆淀粉(PS)(直/支链淀粉比分别约为0.11,0.27和0.44)为唯一淀粉来源的开食料。试验期间,每天4:00-19:00将羔羊抱入补饲栏补饲不同直/支链淀粉比的开食料,并且在6:30, 10:30和15:30将羔羊抱回母羊舍哺乳1 h。羔羊自由饮水,单栏饲喂,自由采食燕麦干草。56日龄时屠宰采样,采集瘤胃组织样品制作石蜡切片进行瘤胃乳头形态测定,采集瘤胃上皮样品提取RNA测定相关基因表达。结果表明:CS组羔羊瘤胃乳头长度和表面积显著(P<0.001)高于MS和PS组,CS和MS组羔羊瘤胃乳头宽度显著(P=0.001)高于PS组。对瘤胃上皮各层厚度统计显示,CS和PS组羔羊瘤胃上皮角质层厚度显著(P=0.001)高于MS组;CS和MS组羔羊瘤胃上皮颗粒层厚度显著高于(P<0.001)PS组;CS组羔羊瘤胃上皮棘基层厚度和总厚度显著(P<0.001)高于MS和PS组。qRT-PCR结果显示:不同直/支链淀粉比开食料显著影响羔羊瘤胃上皮CDK2和CDK6的mRNA表达量(CS>MS>PS, P<0.001);CS组羔羊瘤胃上皮细胞cyclin A和CDK4的mRNA表达量显著(P<0.05)高于PS组,但与MS组无显著差异;CS组羔羊瘤胃上皮cyclin D1的mRNA表达量显著(P=0.012)低于PS组,但与MS组无显著差异。CS组羔羊瘤胃上皮类胰岛素生长因子-1(insulin like growth factor,IGF-1)的mRNA表达量显著(P<0.001)高于MS和PS组,CS和MS组羔羊瘤胃上皮IGF-1R的mRNA表达量显著(P=0.001)高于PS组。上述结果表明:较高支链淀粉比开食料与较高直链淀粉比开食料相比,在瘤胃中较易降解生成挥发性脂肪酸,促进瘤胃上皮IGF-1及细胞周期蛋白mRNA的表达,进而有利于断奶前羔羊瘤胃上皮的发育。研究结果对制订羔羊营养方案具有重要指导意义。     

New approach to the fed pattern: feeding evokes the specific spike burst setting in the small bowel of non-fasted sheep

As feeding is not a factor disrupting the migrating motor (myoelectric) complex (MMC) in sheep, it is presumed that the fed pattern is absent in this animal species. In turn, feeding may stimulate ovine gastrointestinal motility. To verify this discrepancy the myoelectric activities of the antrum and duodeno-jejunum were recorded in seven adult sheep. Additionally, the relationship between electrical and mechanical activity was tested in four of these animals by means of strain gauge force transducers mounted near the duodenal electrodes. Chronic experiments were conducted in fasted and non-fasted sheep before, during, and after standard feeding. Fodder was offered during the duodenal phases 1, 2a, or 2b of the MMC. Two types of responses to feeding (an unspecific and a specific fed pattern) were denoted. A simple increase in spike burst intensity, i.e. without their special deployment and assessed as the myoelectric activity index (unspecific fed pattern), was observed in the abomasal antrum and small bowel during and after feeding in the course of phase 2b of the MMC in non-fasted and fasted sheep. In the abomasal antrum its duration was longer than in the small intestine. In non-fasted animals the unspecific fed pattern was more pronounced in the abomasal antrum than in the small bowel, while its duration was longer in fasted animals. The specific fed pattern was evoked in the duodeno-jejunum during feeding initiated in the course of phase 2b of the MMC exclusively in non-fasted animals. During this pattern, the spike burst series were significantly reduced compared with those which appeared during phase 2b of the MMC and dispersed single spike bursts predominated. The average duration of the specific fed pattern was 3-4 min and it arrived 2-7 min after feeding onset. In the remaining periods during feeding, the spike burst pattern resembled that often observed during phase 2b of the MMC. Thus the confined fed pattern is present in sheep and its character depends upon the gastrointestinal region and feeding habits.     

A survey of antibodies to pestivirus in sheep in the Republic of Ireland

: Sera from 1,448 adult ewes in 91 flocks, representing all 26 counties in the Republic of Ireland, were examined for pestivirus antibodies using a commercially available ELISA which detected IgG1 antibody to border disease virus. Eighty-one sheep (5.6%) in 42 flocks (46.0%) were antibody-positive. Within infected flocks, the mean seroprevalence level was 11.4% with a range of 6.3% to 30.0%. The highest antibody prevalence was detected in sheep from central lowland counties of Ireland. Comparative neutralisation testing of 42 ELISA-positive sera detected geometric mean antibody titres of 136 to the NADL strain of bovine viral diarrhoea virus (BVDV), 92 to the Moredun strain of border disease virus and 21 to the 137/4 strain of border disease virus. These results suggest that BVDV may be the major ruminant pestivirus infecting sheep in Ireland. Although there are high numbers of infected flocks, many sheep within such flocks remain antibody-negative and are at risk of giving birth to lambs with congenital border disease.     

Effects of age on the electroencephalographic response to castration in lambs anaesthetised using halothane in oxygen

AIM: To use the electroencephalogram (EEG) to ascertain whether the response of the cerebral cortex to the noxious stimulus of castration varied with age in lambs.

METHODS: Two groups of East Friesian lambs were selected according to age; the mean age of the younger group (n=21) was 12 (SD 2) days and the older group (n=20) was 29 (SD 1) days. Anaesthesia was induced via mask using 4% halothane in oxygen, and maintained using 1.5% halothane in oxygen at a flow rate of 4 L/min. Once a stable plane of anaesthesia had been achieved, data collection of EEG and electrocardiographic (ECG) readings commenced, and the lambs were castrated 15 min later, using rubber rings. Median and 95% spectral edge frequencies (F95) and total EEG power (ptot) were derived from data from the EEG.

RESULTS: Following castration, there was an increase in the median frequency (F50) in the younger lambs (p=0.002), and an increase in ptot in both groups (p=0.05), which was of greater magnitude in the older lambs. There were no significant changes in the F95. Both younger and older lambs exhibited a transient bradycardia (p=0.001 and p=0.01, respectively).

CONCLUSIONS: These differences in the cortical response between the two groups suggest that 2-week-old lambs undergo a qualitatively different perception of the noxious stimulus of castration compared to 4-week-old lambs.     

杂交野猪适宜日粮磷水平与钙磷比例的研究

选用纯种野公猪与杜洛克母猪的杂交后代含50%野猪血缘的42日龄杂交野猪36头,随机分成9组,试验为双因子3水平(3×3)析因安排分组,完全随机区组设计,每个因子3个水平,共9个处理。结果显示,不同磷水平与钙磷比例对各处理组的平均日耗料量、平均日增重、料重比差异均不显著(P>0.05)。不同钙磷比例水平下对血清钙的影响差异极显著(P<0.01),日粮磷和钙磷比例互作效应对血清钙影响差异极显著(P<0.01)。不同日粮钙磷比例对血清磷水平差异显著(P<0.05),日粮磷和钙磷比例互作效应对血清磷影响显著(P<0.05);0.4%的日粮磷水平与0.6%的磷水平对血清AKP活性影响差异极显著(P<0.01)。     

Utilization of an enzyme heat stability test and erythrocyte glycolytic intermediate assays to assist in the diagnosis of canine pyruvate kinase deficiency

A macrocytic hypochromic anemia, with marked reliculocytosis and large numbers of circulating nucleated erythrocytes, was recognized in a 3 1/2-year-old male Beagle-cross dog. A presumptive diagnosis of erythrocyte pyruvate kinase (PK) deficiency was made, even though PK activity from the patient was within the range of activities measured for normal dogs, because the PK activity should have been several times normal in light of the large number of reticulocytes present. The PK activity in a hemolysate from the patient was heat-labile compared to activities in hemolysates from normal dogs, a finding consistent with results from a previous study of PK-deficient Basenji dogs. Seven phosphorylated glycolytic intermediates and 2,3-diphosphoglycerate were measured in protein-free extracts of erythrocytes from the patient. All were present in concentrations above that present in normal canine erythrocytes, further supporting the diagnosis of PK deficiency.     

The estimation of gastrointestinal strongyle worm burdens in young sheep flocks: a new approach to the interpretation of faecal egg counts. I. Development

A new approach to the interpretation of faecal egg counts using a simple "formula", is described. It is suggested that adoption of this procedure may enable the likely level and frequency distribution of strongyle worm burdens (Nematodirus excluded) in young sheep flocks to be estimated. The potential relevance of this information to the diagnosis of gastrointestinal parasitism is discussed.     

A review of selenium deficiency in grazing ruminants. Part 2: towards a more rational approach to diagnosis and prevention

ESTIMATING SELENIUM STATUS: Although the importance of selenium in ruminants has been recognised for over 30 years, problems associated with selenium deficiency are still frequently identified in grazing livestock operations. There is a growing diversity of tools available for the management of selenium deficiency giving rise to diagnostic and therapeutic dilemmas for the veterinary practitioner. There is no single test for selenium adequacy which can be considered superior in all diagnostic situations because the method of choice depends on the objective of the testing procedure. REFERENCE RANGES: Reviewing the available data, the current New Zealand reference ranges for selenium concentrations in ruminant tissue and feed appear valid. CLINICAL RELEVANCE: Management of selenium deficiency will continue to be important in grazing ruminants. Practising veterinarians should be familiar with the appropriate use of tests for selenium deficiency. Advice should be based on micronutrient analysis of animal tissue, defensible reference ranges backed by production response data, and supplementation programmes which optimise the return on investment.