Effects of Calliandra and Sesbania supplementation on weight gain in dairy calves on smallholder farms in Kenya.

The growth rate of female calves on dairy farms is one of the crucial factors which influence age at first calving, affecting lifetime lactation productivity of a dairy cow. Diets with adequate crude protein are necessary to support calf growth. The study objective was to determine the effects of nutritional advice and diet supplementation with Calliandra calothyrsus and Sesbania sesban on average daily weight gain in dairy calves on semi-commercial smallholder dairy farms in Kenya. This trial involved 155 calves from 73 smallholder dairy farms, in Kenya, randomly selected and allocated to either intervention or control groups. The intervention group received nutritional advice and seedlings of Calliandra calothyrsus and Sesbania sesban, while the control group did not receive these interventions. Every 1-2 months for 16 months, data on farm nutritional practices and management were collected in a questionnaire, and physical examinations were done to monitor weight and health status. Descriptive and univariable statistical analyses were conducted, and multivariable mixed linear regression models were used for identification of factors associated (P < 0.05) with the natural log transformation of weight gain of calves on a given farm, controlling for clustering of visits within calves. Feeding at least 0.2 kg/day (wet weight) of Calliandra or Sesbania to calves <6 months old resulted in 33.2% increase in daily weight gain, while controlling for confounding by breed and sex of the calf. For calves ≥6 months, there was a significant interaction between amount of hay fed and if calves were also fed on Calliandra or Sesbania. When no Calliandra or Sesbania supplementation was provided, the mean weight gain was low and relatively constant even with increasing amounts of hay. When Calliandra or Sesbania supplement was added to the diet, the mean weight gain increased from 0.17 kg to 0.48 kg when hay was fed at 1 and 5 kg, respectively, while controlling for confounding by amount of maize silage fed and the prevailing season. In conclusion, supplementation of calf diets with at least 0.2 kg/calf/day of Calliandra or Sesbania is beneficial for faster weight gains.

The effect of selenium supplementation before calving on early-lactation udder health in pastured dairy heifers.

Selenium (Se) deficiency has been associated with lowered resistance to mastitis in dairy cattle. However, little published data exists on the effect of Se supplementation before calving on udder health of pastured dairy heifers. Further, the relative efficacy of injectable barium selenate and oral organic Se for improving udder health in cows has not previously been tested. The objectives of this study were to determine the effects of precalving Se supplementation and type of supplementation on the blood activity of glutathione peroxidase and measures of udder health immediately after calving and during the first month of lactation in pastured dairy heifers. One hundred forty pregnant Chilean Holstein-Friesian heifers were fed a basal diet containing, on average, 0.15 mg of Se/kg of dry matter. One month before predicted calving, heifers were allocated to 1 of 3 groups. Group 1 (n=49) received no supplementary Se, group 2 (n=46) received a single subcutaneous injection of Se (1 mg/kg of live weight, as barium selenate), and group 3 (n=45) was fed Se yeast (3 mg/heifer/d until calving). Heifers supplemented with barium selenate had a higher glutathione peroxidase activity from 14 d in milk onwards. Selenium supplementation, irrespective of source, tended to reduce the prevalence of intramammary infection (IMI) and decrease the prevalence of quarters with high somatic cell count (SCC) at calving. Overall, Se supplementation did not result in a reduction of the incidence of new IMI or clinical mastitis or in decreased SCC during the balance of the first month of lactation. However, in pasture-based heifers injected with barium selenate before calving, and fed diets with 1.3 and 2.5 mg of Se/d precalving and during lactation, respectively, no cases of clinical mastitis were observed in the first month of lactation.

Milk selenium concentration and its association with udder health in Atlantic Canadian dairy herds.

Soils and plants in Atlantic Canadian provinces are known to contain low concentrations of selenium (Se). Earlier studies have indicated that dairy producers in Atlantic Canada are providing insufficient supplementary Se in the ration to meet the Se requirements of dairy cattle, as measured by herd-level milk Se concentration. The objective of this study was to evaluate the association between milk Se concentration and somatic cell count (SCC) and the risk of new intramammary infection (IMI) in the dry period, in Atlantic Canadian dairy cows. Eighteen dairy farms participating in the Canadian Bovine Mastitis Research Network cohort study were selected as a convenience sample. On each farm 15 cows to be dried off were selected. Quarter milk samples were collected at 4 and 2 wk before drying-off, within 24 h after calving, and at 7 d after calving to evaluate IMI status. Composite milk samples were analyzed for SCC and Se concentration. Mean milk Se concentration was marginal in 14% of the cows that were on pasture during the grazing season. Milk Se concentration was not associated with the overall odds of new IMI in the dry period; however, the odds of having a new Streptococcus spp. and other gram-positive pathogen IMI in the dry period increased with increasing milk Se concentration. Somatic cell count increased with milk Se concentration, even after adjusting for IMI status. The dairy population in our study had higher ranges for milk Se concentration, whereas ranges for prevalence of IMI, and SCC were lower, compared with those in studies where a negative relationship between Se status and udder health was first noted. Therefore, under the current management conditions, milk Se concentration did not appear to be a principal determinant of udder health.

Barium selenate supplementation and its effect on intramammary infection in pasture-based dairy cows.

A significant proportion of cattle receive inadequate dietary Se because of its low content in soils and pastures of various regions of the world. Several economically important diseases in dairy cows, such as mastitis, have been associated with Se deficiency. The objective of this study was to evaluate the effect of a single injection of a long-acting form of Se at drying off on the risk and incidence rate of new intramammary infections and on milk somatic cell count in the subsequent lactation in pasture-based dairy cows. Forty-nine Chilean Holstein-Friesian cows were fed a diet containing <0.05 mg of Se/kg of ration dry matter. During the dry period, cows were allocated to 1 of 2 groups, a supplemented (n=24) group treated with a single subcutaneous injection of barium selenate 2 mo before calving and a control group (n=25) that remained unsupplemented. Duplicate foremilk samples were aseptically collected within 6 d after calving and every 2 wk until drying-off for bacteriological culture. Milk samples were also collected monthly for somatic cell count evaluation. Blood samples were collected before treatment and at 30, 90, 180, and 270 d after treatment for analysis of blood glutathione peroxidase (GPx) activity. The activity of glutathione peroxidase was higher in supplemented cows 30 d after the injection until the end of the study. The risk and incidence rate of new intramammary infections was not affected by supplementation. A progressive increase in somatic cell count was observed throughout lactation, but there was no effect of supplementation. In conclusion, a one-time injection of barium selenate 2 mo before calving in these pasture-based dairy cows did not affect udder health in the subsequent lactation, indicating that Se basal intake was adequate for preventing subclinical mastitis in pasture-based cows in southern Chile.

The effect of age on the immune response of horses to vaccination.

Few studies have investigated immunosenescence in the horse, but it is accepted that the primary and secondary (anamnestic) immune responses may differ between aged and younger horses. The aim of the present study was to determine whether aged horses have a protective immune response post-vaccination. Thirty-four aged healthy horses (> or =20 years) and 29 younger adult horses (4-12 years) of various breeds were vaccinated with commercially produced killed rabies and influenza vaccines. Rabies serum neutralizing antibody titres and equine influenza virus specific antibody subclasses (immunoglobulin IgGa and IgGb) and single radial haemolysis titres were determined. Healthy aged horses mounted a primary immune response to rabies vaccine that was similar to that of younger adult horses. However, aged horses had a significantly reduced anamnestic response to influenza vaccination in comparison with the younger adult horses, even though the pre-vaccination antibody titres of aged horses were higher. Rabies antibody titres in both groups declined significantly by 6 months post-vaccination. Serum concentrations of selenium (Se) and vitamin E were measured to test for potential confounding effects. Significant numbers of horses had suboptimal serum Se concentrations, but Se status had no significant impact on antibody production after vaccination.

Meta-analysis of the effect of oral selenium supplementation on milk selenium concentration in cattle.

Soils in many regions of the world have a low Se content. Consequently, forages and crops grown on these soils may provide inadequate dietary Se for humans and grazing animals. Selenium supplementation has been used to enhance Se status and milk Se concentration, but results conflict. Milk Se concentration appears to be a useful indicator of animal and herd Se status, and reflects the responsiveness to supplementation. A systematic review and meta-analysis were carried out to summarize all available scientific evidence for the effect of oral Se supplementation on milk Se concentration in cattle. The literature search was based on electronic and nonelectronic databases. Fixed- and random-effects models of meta-analysis were used, and a meta-regression was carried out to evaluate heterogeneity among studies. Random-effects meta-analysis was performed on 42 studies published between 1977 and 2007. Oral Se supplementation resulted in an average increase in milk Se content of 0.16 (95% confidence interval: 0.117, 0.207) micromol/L, with a significant heterogeneity among studies. Weak publication bias was evident, but it did not change the average effect. The continent where the study was performed, Se source, Se dose, and the interaction between source and dose explained 71% of the between-study variance. On average, American cows supplemented with Se yeast (e.g., 6 mg/h per day) had greater milk Se concentrations (approximately 0.37 micromol/L) 75 d after the beginning of supplementation when compared with those supplemented with inorganic forms of Se. This information provides a basis for tailoring daily animal requirements and for enhancing the Se intake of consumers of dairy products.

The effect of age on serum antibody titers after rabies and influenza vaccination in healthy horses.

BACKGROUND: The proportion of geriatric horses within the equine population has increased in the past decade, but there is limited information on the immune function of these animals. HYPOTHESIS: Aged horses will have a lesser increase in serum antibody response to vaccination. ANIMALS: Thirty-four aged healthy horses (> or = 20 years) and 29 younger adult horses (4-12 years) of various breeds. METHODS: All horses were vaccinated with vaccines of killed rabies and influenza virus. Horses in each age group were allocated to receive either rabies or influenza booster vaccine 4 weeks after the initial vaccination. Serum samples were taken at 0, 4, 8, and 24 weeks. Rabies serum neutralization titers and equine influenza virus specific antibody sub-isotypes (IgGa, IgGb, IgG(T), and IgA) as well as single radial hemolysis (SRH) titers were determined. RESULTS: Rabies antibody titers were similar in the 2 age groups at all sampling times. Aged horses had higher IgGa and IgGb influenza antibody titers before vaccination than younger horses but similar titers after vaccination (P= .004 and P= .0027, respectively). Younger horses had significantly greater increases in titer than aged horses at all sampling times for IgGa (P= .001) and at 8 and 24 weeks for IgGb (P= .041 and .01, respectively). There was no detectable serum IgG(T) at any time point. A significant booster vaccine effect was seen for both antirabies and anti-influenza titers. Anti-influenza titer before vaccination also had a significant effect on subsequent antibody response. CONCLUSIONS AND CLINICAL IMPORTANCE: Healthy aged horses generated a primary immune response to a killed rabies vaccine similar to that of younger adult horses. Aged horses had a significantly reduced anamnestic response to influenza vaccine.

Effect of copper supplementation on copper status of pregnant mares and foals.

Pregnant Thoroughbred mares (n = 21) were grazed on tall fescue pasture containing 4.4-8.6 mg Cu/kg dry matter (DM). Twelve mares were supplemented with approximately 0.5 mg Cu/kg liveweight (LW)/day as copper sulphate for the final 13-25 weeks gestation. Plasma copper concentration declined during the third trimester for all mares and was not affected by copper supplementation. Liver copper concentration of mares and foals was determined when the foals were 4-10-days-old. Copper supplementation of the mares tended to increase mare liver copper concentration (P<0.08) and increased foal liver copper concentration (P<0.01). There was a significant relationship between mare and foal liver copper concentration (P<0.001, r2 = 0.7). Increasing the copper intake of mares is effective in enhancing the copper status of foals.

Effect of copper supplementation on the copper status of pasture-fed young Thoroughbreds.

The effect of copper supplementation of pasture fed mares and foals on the copper status of the foals, in terms of plasma, soft tissue and bone copper concentrations and caeruloplasmin activity, was investigated. Twenty-one Thoroughbred foals from either control mares (n = 9), or copper-supplemented mares (n = 12) were divided randomly into control (pasture only, n = 10) or supplemented (pasture and oral copper sulphate, n = 11) groups. The pasture diet was grazed by all animals, and contained 4.4-8.6 mg Cu/kg dry matter (DM). The copper supplement for the mares contained copper sulphate equivalent to 0.5 mg Cu/kg liveweight (LW)/day. This daily dose was converted to allow administration as a thrice weekly dose (i.e. multiplied by 7/3) which was given for 13-25 weeks prior to foaling. The supplemented foals, also dosed 3 times a week, received 0.2 mg Cu/kg LW/day at age 21 days, which was increased to 0.5 mg Cu/kg LW/day at 49 days and was continued at this level until euthanasia at 150 days. Foal plasma copper concentration and caeruloplasmin activity increased from birth to 21 days post partum and then plateaued at a concentration similar to the mare, but the rise in these indices was not affected by copper supplementation of the mare or foal. Copper supplementation of the foal increased foal liver copper concentration at 150 days (P<0.03). Copper intake of diets containing approximately 8-28 mg Cu/kg DM is well reflected by liver copper concentration, but is poorly reflected by bone, other soft tissue copper concentrations and circulating copper status indices.

A review of selenium deficiency in grazing ruminants. Part 1: new roles for selenium in ruminant metabolism.

SELENIUM AVAILABILITY: Selenium deficiency has been an important source of loss to the pastoral industries of New Zealand. About 30% of farmed land in New Zealand is considered to be selenium-deficient and continued development of soils and pasture will tend to further decrease the concentration of selenium in pasture. BIOLOGICAL FUNCTIONS: Formerly it was believed that all biological functions of selenium in animals could be attributed to the antioxidant activity of the enzyme glutathione peroxidase. More recently, it has been shown that selenoproteins have roles in immune function and thyroid hormone metabolism. RESPONSES TO SUPPLEMENTATION: Following supplementation of ruminants grazing pastures deficient in selenium, milk production and growth responses are likely to occur in cattle, while in sheep improvements in growth and fertility are most likely. Reproductive dysfunction may not be as important as previously thought in cattle grazing pasture moderately deficient in selenium. The relationship between selenium intake and disease resistance deserves further study. CLINICAL RELEVANCE: Management of selenium deficiency will continue to be important in grazing ruminants. Veterinarians should be aware that many selenoenzymes exist, some with functions quite distinct from the antioxidant role of glutathione peroxidase.

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.

The effect of injectable barium selenate on the selenium status of horses on pasture.

AIM: To examine the effect of intramuscular barium selenate on the blood selenium concentration of horses with marginal selenium status. METHODS: Eighteen mares were assigned to one of six groups. The mares in groups 1-4 received barium selenate at 0.5, 0.75, 1.0 and 1.5 mg Se/kg, respectively, injected into the right pectoral muscle mass. The mares in group 5 received sodium selenate at 0.05 mg Se/kg orally at 8-week intervals. The mares in group 6 were left untreated. Blood samples were collected at 0, 1, 2, 5, 10, 30, 60, 90, 120, 180, 240, 300 and 360 days after the initial treatment for assay of whole blood and plasma selenium. Injection site reactions were recorded on each sampling date. RESULTS: Treatment with barium selenate at each dose rate significantly increased whole blood, plasma and blood cell selenium concentrations when compared to no treatment or oral treatment with sodium selenate, and maintained group mean whole blood selenium concentrations in the adequate range (>1600 nmol/l) until the end of the experimental period of 1 year. The severity of injection site reactions increased with dose rate but was considered acceptable alt the lower dose rates used. CONCLUSION: The injection of barium selenate placed aseptically at a deep intramuscular site was efficacious in correcting the selenium status of mares grazing pasture with a selenium content of 0.01-0.07 mg/kg DM. However, some swelling and fibrosis at the injection site was apparent at all dose rates used. CLINICAL RELEVANCE: There is currently no long-acting selenium supplementation product licensed in New Zealand for use in horses. Barium selenate promises to provide a useful method for selenium supplementation for horses, with an effective duration of at least 1 year following a single injection.

Effect of selenium and lodine supplementation on growth rate and on thyroid and somatotropic function in dairy calves at pasture.

The effects of Se and I supplementation on growth rate and on thyroid and somatotropic function were examined for heifer calves from two herds fed pasture. Supplementation of calves with intraruminal Se pellets increased the basal plasma concentration of 3,5,3'-triiodothyronine and reduced the basal plasma concentration of thyroxine for both herds. For one herd, supplementation with Se increased the triiodothyronine response to challenge with thyrotropin-releasing hormone, increased BW gain, and tended to increase the plasma concentration of IGF-I. The plasma concentration of growth hormone was unaffected by Se supplementation. Supplementation with I increased the response of thyroid hormones to thyrotropin-releasing hormone but did not increase BW gain. Interaction between Se and I treatment within the herds was not apparent for any outcome variable. These data suggest that the effects of Se deficiency in grazing calves may be mediated by alterations in thyroid hormone metabolism but apparently are not mediated through modulation of the peripheral concentration of growth hormone.

Serum glutathione peroxidase activity reflects short-term increases in selenium intake in goats.

The objective of this study was to determine if serum glutathione peroxidase activity reflects short-term changes in the selenium status of goats. Angora goat kids (n=14) were fed pelleted luceme containing 20 microg/kg of selenium, and treated orally with either selenium (0.1 mg/kg of liveweight weekly, as sodium selenate) or de-ionised water. Serum activity of glutathione peroxidase was increased in response to supplementation and differed from that of controls within 24 hours of supplementation. The change in serum glutathione peroxidase activity during the 21 days after the start of weekly supplementation closely followed changes in serum selenium concentration. The results of this study suggest that serum glutathione peroxidase activity reflects the short-term improvement in the selenium status of Angora goat kids following oral supplementation with sodium selenate.

Effect of selenium and a-tocopherol supplementation on postpartum reproductive function of dairy heifers at pasture.

The objective of this study was to investigate the effects of selenium (Se) and alpha-tocopherol supplementation on uterine involution and ovarian function in dairy heifers fed a prepartum diet containing low concentrations of Se and alpha-tocopherol. Twenty-four pregnant Friesian heifers were randomly allocated to one of four experimental groups in a 2 x 2 design balanced for age and body weight. Prepartum treatments consisted of supplementation with either 2 intraruminal Se pellets or 3600 mg of alpha-tocopherol p.o. 4 times per wk, or both. Control animals received no supplementation. For 8 wk before calving, the heifers were fed exclusively on pasture hay which contained less than 10 microg/kg of Se and 19 mg/kg of alpha-tocopherol. After calving, the heifers grazed perennial ryegrass and white clover pasture. Concentrations of Se and alpha-tocopherol in serum for the prepartum heifers of the control group were 10 ng/ml and 1.3 microg/ml, respectively, indicating deficiencies of these nutrients. Treatment with Se and alpha-tocopherol increased prepartum serum concentrations of Se and alpha-tocopherol to 74 ng/ml and 5 microg/ml, respectively (P < 0.001). However, treatment with Se, alpha-tocopherol, or both, failed to enhance uterine involution, hasten resumption of postpartum ovarian activity or reduce the incidence of clinical postpartum abnormalities. These findings suggest that postpartum reproductive dysfunction is not a primary feature of moderate Se or vitamin E deficiency of cattle at pasture.

Alpha-tocopherol, selenium and polyunsaturated fatty acid concentrations in the serum and feed of spring-calving dairy heifers.

The objectives of this study were to provide baseline data for alpha-tocopherol, selenium and polyunsaturated fatty acid concentrations in the serum and feed of New Zealand dairy cattle, and to assess the likelihood that abnormal peroxide metabolism has a role in the impaired lactational and reproductive performance noted in selenium-deficient cattle. Twenty-four Friesian heifers were randomly allocated one of four winter diets consisting of hay with or without selenium supplementation, or pasture and silage with or without selenium supplementation. A winter diet consisting exclusively of hay (alpha-tocopherol concentration 19 mg/kg of dry matter) resulted in a pre-calving serum alpha-tocopherol concentration of 1.2 mg/l compared to 4.5 mg/l for pastured heifers (p<0.01). The pre-calving alpha-tocopherol concentration for the heifers fed hay fell into the range considered deficient (<2.0 mg/l), whereas heifers fed pasture and silage remained in the range considered adequate throughout the study period. Serum fatty acid concentration, and the proportion of fatty acids that were polyunsaturated, were lowest in the hay-fed heifers before calving (1.0 mg/ml, 37.1% respectively), and remained unchanged following re-introduction to pasture after calving in late July and August. Serum fatty acid concentration did not increase following the re-introduction of the heifers to pasture because of the unexpectedly low fatty acid concentration (4.8 g/kg of dry matter) of the mature winter pasture. In October, however, the proportion of fatty acids in serum that were polyunsaturated increased (50%) as did serum cy-tocopherol concentrations (greater than 13 mg/l). Mean serum selenium concentrations in the unsupplemented heifers ranged from 139 to 204 nmol/l, being lowest in October (p<0.01). Supplementation with intraruminal selenium pellets (two pellets delivering about 3 mg of selenium/day) increased serum selenium concentration and glutathione peroxidase activity (p<0.01) whereas the type of winter diet had no effect (p>0.05). These results suggest that dairy cattle wintered on hay can become Vitamin E-depleted, whereas the feeding of pasture and silage should provide adequate Vitamin E. The pasture offered following calving during July and August provided a low dietary polyunsaturated fatty acid challenge, suggesting that abnormal peroxide metabolism is unlikely to be an important mechanism in the impaired performance of selenium-deficient adult cattle which calve at this the of year.

The effect of intra-ruminal selenium pellets on growth rate, lactation and reproductive efficiency in dairy cattle.

In each of two dairy herds (A and B), rising yearling heifers (Trial 1) and adult cows (Trial 2) were assigned to three treatment groups. Untreated animals were compared to animals treated with either two or four intra-ruminal pellets containing 3 g of elemental selenium. The administration of pellets at the recommended dose (two pellets per animal) was effective in elevating whole blood glutathione peroxidase activity and selenium concentration to over 10 times those of control animals. In Trial 1, a 15% response in liveweight gain (p<0.001) occurred in yearling heifers in the herd with the lowest pre-treatment selenium status. In Trial 2, cows receiving two pellets produced a greater milk volume (p=0.06) and more milk solids (p=0.02) than untreated controls; an increase in volume of 5.4% and 8%, and in milk solids of 6.5% and 6.4%, were noted in herds A and B respectively. There was a trend towards decreasing somatic cell counts in milk from the treated cows when compared to controls, the four-pellet group in Herd A and the two-pellet group in Herd B being significantly different from their respective control group. No between-group differences were noted in calving-first service or calving-conception intervals, nor in the proportion of animals pregnant to first or all services. The administration of selenium at twice the recommended dose rate yielded no additional response above that noted after the administration of the recommended dose. The results of this study support the use of currently recommended Ministry of Agriculture and Fisheries selenium reference ranges in cattle for the prediction of a response to supplementation.