CASE NOTES
LACK OF RESPONSE TO TRACE MINERAL SUPPLEMENTATION OF SHEEP AND CATTLE ON THE CENTRAL TABLELANDS OF NSW
BR Watt, K Crawford and J Eppleston, Tablelands Livestock Health and Pest Authority (now Central Tablelands Local Land Service), 66 Corporation Avenue, Bathurst NSW
This paper was presented at the Combined ACV/ASV Annual Conference, Hobart 2015 and appears in the Proceedings of the Combined Australian Cattle Veterinarians and Australian Sheep Veterinarians (ACV/ASV) Annual Conference, Hobart 2015, pp 308-311
Posted Flock & Herd June 2015
Introduction
Selenium deficiency, as measured by low blood glutathione peroxidise levels, is widespread across the central tablelands of NSW and there is evidence of cobalt deficiency in limited areas. The authors have previously described clinical selenium deficiencyiv v vi but we have also reported variable production responses to selenium supplementation in both sheep and cattle in this region. For example deficient Merino weaners supplemented with selenium responded with improved growth rates, fleece weights and lower worm egg counts. However, we observed no growth response in deficient young cattle or improved fertility in marginally deficient ewes when given selenium supplements.
In this paper we present the findings from a further two studies in sheep and cattle in which production responses following supplementation with selenium, vitamin B12 and a commercial mineral mix were absent in the face of low blood levels of GSHPX and/or vitamin B12.
GROWTH RESPONSE TO SELENIUM AND B12 SUPPLEMENTATION IN PRIME LAMBS
Background
As part of an investigation into poor growth of prime lambs, on a property with improved pastures on shale derived soils south of Oberon, marginal selenium levels and low blood vitamin B12 levels were found. A major finding was that the lambs suffered from a burden of macrocyclic lactone resistant Haemonchus. In a faecal egg count reduction test conducted in May 2011, undrenched control lambs had a WEC of 1844 epg, 97% of which were Haemonchus and abamectin and ivermectin produced only a 75% and 0% reduction in WEC, respectively.
Blood samples were collected on two occasions from five lambs. In May pooled samples had normal selenium levels (71 U/gHb) but B12 levels were low (averaging 336 pmol/L compared to normal values of 400-5000 pmol/L). Later, in January 2012, marginal selenium deficiency was detected with two of five samples below the threshold of 50 U/gHb. Vitamin B12 levels were also deficient with four of five lambs below 400 pmol/L (averaging 297 pmol/L).
As a result we conducted two response trials in consecutive drops (2010 and 2011) of this flock to determine whether supplementation with these two minerals would improve lamb growth.
Methods
Trial 1 - 2010 drop
In May 2011, 123 tail end lambs that had not met sale weight were randomly drafted into 4 groups and identified with coloured tags. These were treated with vitamin B12 (1 ml subcutaneous injection of Vitamin B12 cobalamin complex injection for sheep and cattle, containing 1.72mg/ml hydroxocobalamin and 0.2 mg/ml cyanocobalamin, Novartis) and/or selenium (Deposel, 50mg/ml of barium selenate, given subcutaneously at a dose rate of 1 ml/50kg bodyweight, Novartis) in a 2 x 2 factorial design. The lambs were then grazed together on improved perennial pastures for 65 days and re- weighed in July when the majority of lambs were ready for sale.
Trial 2 - 2011 drop
In January 2012, 354 weaner lambs from the same flock that were left after the top-end of the sucker lambs were sold, were individually identified and stratified on LW into four groups. The lambs were again treated with vitamin B12 and/or selenium (as above) in a 2 x 2 factorial design. Blood samples collected in March 2012 showed that 9/10 lambs not treated with B12 had blood levels below 400 pmol/L (averaging 300 pmol/L), as did two of the lambs in the B12 treatment groups. The treatment groups were therefore retreated 70 days after the initial treatment.
Trial lambs grazed improved pastures for the duration of the study and were reweighed 59 and 104 days later. Blood samples collected at the start (n=10) and at the end of the trial (five animals per group) were tested for GSHPx and Vitamin B12. Following a moderate WEC (196 epg) weaners were drenched with moxidectin (Cydectin LV, moxidectin 2.0 g/L dosed at 1 ml/10kg, Virbac Animal Health). In both lamb trials LW data were analysed by ANOVA.
Results
Trial 1 - 2010 drop
Despite random drafting into groups on the day of treatment, the lambs receiving B12 were significantly heavier than those left untreated (35.57 vs. 33.66 kg: P=0.003). There was no difference between animals receiving the 2 selenium treatments (34.66 vs. 34.57; NS) in initial LW.
Because lambs were not individually identified in 2011, growth rates could not be determined and analysed, making statistical interpretation difficult. However at the second weighing there was no difference between B12 (42.68 vs. 43.35 for untreated and treated lambs: NS) or selenium (42.81 vs. 42.23 for untreated and treated lambs; NS) groups in final LW suggesting that neither selenium nor B12 improved lamb growth.
Trial 2 - 2011 drop
A second trial was conducted to overcome the problems encountered in Trial 1 and to confirm the previous finding of no response to supplementation of selenium or vitamin B12. Because lambs were stratified into groups there was no difference between starting LW. At the start of the trial the average blood levels for GSHPx and vitamin B12 were 70 ± 19 U/g Hb and 418 ± 58 pmol/L, respectively. GSH Px levels were significantly increased in the groups treated with selenium, and levels in the 2 groups treated with B12 were also significantly greater than the untreated groups (Table 1).
Again there was no significant effect of supplementing lambs with either selenium or vitamin B12 on subsequent LW or lamb growth during the study (Table 1).
Table 1. Blood levels and growth response of prime lambs supplemented with selenium and vitamin B12.
| Treatment Group | GSH Px (U/g Hb) |
Vitamin B12 (pmol/L) |
LWt1 (kg) |
LWt2 (kg) |
LWt3 (kg) |
ADG 1-3 (g/day) |
|---|---|---|---|---|---|---|
| Control | 56 a | 570 a | 32.3 | 38.9 | 45.1 | 120 |
| B12 | 65 a | 994 b | 32.7 | 38.8 | 45.5 | 124 |
| Se | 284 b | 539 a | 32.7 | 39.5 | 45.7 | 123 |
| Se + B12 | 206 b | 854 b | 33.4 | 39.8 | 46.0 | 123 |
Means with different superscripts within columns are significantly different (P<0.05)
GROWTH AND FERTILITY RESPONSE OF ANGUS HEIFERS SUPPLEMENTED WITH SELENIUM AND A MULTI-MINERAL MIX
Background
Following concerns from a cattle producer about trace mineral deficiencies in his herd we designed a trial to determine whether supplementation with selenium would improve the growth of his Angus heifers and their fertility at first joining. The property is located on shale and granite derived soils with improved pastures south of Bathurst in an area considered likely to be selenium deficient. We also included a group treated with a commercial multiple mineral supplement (MM) containing zinc, copper, manganese and selenium, to evaluate whether additional minerals may improve any observed production response to selenium.
Methods
At weaning in February 2013, a mob of 173 Angus heifers with low blood GSHPx levels were weighed and then stratified into 4 treatment groups and treated as follows;
- Selenium given at weaning (S).
- Selenium given at weaning and a MM injection given pre-joining (SM)
- MM given at both weaning and pre-joining (M), and,
- a control group that received no supplements at either weaning or pre-joining (C).
Both selenium (Deposel, containing 50mg/ml of barium selenate: Novartis) and MM (Multimin, containing zinc as disodium zinc EDTA 40mg/mL, manganese as disodium manganese EDTA 10mg/mL, copper as disodium copper EDTA 15mg/mL and selenium as sodium selenite 5mg/mL: Virbac Animal Health) were given subcutaneously at dose rates of 1 ml /50 kg bodyweight.
The heifers grazed improved pastures and were re-weighed at joining and at pregnancy scanning (198 and 316 days later, respectively). Blood samples were collected at pregnancy scanning from 10 randomly selected animals from each of the 4 treatment groups and these were tested to determine GSH PX, copper and zinc concentrations. Growth and blood test data were analysed by ANOVA.
Results
The mean blood levels of trace minerals, LW at joining and at pregnancy scanning, and fertility and foetal age at pregnancy scanning are presented in Table 2. All three treatments significantly elevated GSHPx levels compared to untreated controls. Selenium treatment elevated levels more than MM-treatment with the greatest increase in heifers treated with both products. However no treatment increased blood levels of copper or zinc.
Despite the effect on circulating selenium levels there were no significant differences between treatment groups in LW, fertility or stage of pregnancy at pregnancy testing.
Table 2. Final (pregnancy scanning) mean (s.e.m.) blood trace mineral levels and joining and final LW, fertility and foetal age at scanning for heifers supplemented with trace minerals at weaning.
| Treatment group | Blood levels | LW at | Fertility (percent pregnant) |
Foetal age (weeks at scanning) |
|||
|---|---|---|---|---|---|---|---|
| GSH PX | Copper | Zinc | Joining (kg) |
Preg. test (kg) |
|||
| C | 8±12a | 16.3±1.0 | 12.3±0.6 | 249 ± 4 | 337 ± 5 | 65.9 ± 7.2 | 9.8 ± 0.5 |
| M | 72±12b | 17.1±1.0 | 11.3±0.6 | 249 ± 4 | 334 ± 5 | 67.5 ± 7.3 | 8.7 ± 0.5 |
| S | 188±12c | 15.6±1.0 | 12.5±0.6 | 255 ± 4 | 342 ± 5 | 74.4 ± 7.0 | 9.8 ± 0.4 |
| SM | 292±12d | 15.6±1.0 | 11.9±0.6 | 256 ± 4 | 342 ± 5 | 73.2 ± 7.2 | 8.9 ± 0.5 |
Means with different superscripts within columns are significantly different (P<0.05)
Discussion
These trial findings suggest that supplementation with selenium or vitamin B12 is unlikely to produce a production response even in prime lambs flocks and cattle herds known to be deficient in circulating levels in the central tablelands of NSW..
Young sheep in areas known to be deficient in cobalt and selenium, such as the Fleurieu Peninsula in South Australia nonetheless shown variable, including sex-related responses. The results of our trials showed no response over two years despite blood test results indicating deficiency for at least some of the year. These results suggest that while responses to B12 cannot be ruled out in some seasons they also suggest that B12 supplementation is not a high priority for central tablelands livestock producers.
Similarly in we could not demonstrate a growth or fertility response in heifers supplemented with selenium and this is in agreement in a previous trial conducted in 2008 in selenium deficient heifers.ii However, clinical selenium deficiency has been reported previously on the central tablelands.
Mineral supplementation may have benefits other than improvements in weight gain or fertility. Our previous study showed that selenium supplementation reduced the worm egg count of young sheep.ii A range of other studies have shown the effects of selenium (and vitamin E) on immune function. Some of these benefits may relate to liver stores of minerals that become available to help the immune system through enzyme systems such as serum superoxide dismutase. For example, recent studies that injectable mineral supplementation can have lower the rate of mastitis. However, unfortunately benefits other than on production traits are difficult to quantify and subject to economic analysis.
Acknowledgements
We gratefully acknowledge the support of Jason Southwall from Neville McMichael and associates and the considerable assistance of manager Jeremy Woods. Ben Kidd from Virbac assisted with the trial and Virbac provided the Multimin and funded the laboratory tests.
References
- Watt BR (2007) A serological and trace mineral survey of beef heifers in central NSW Australian Cattle Veterinarians Conference Townsville
- Celi P, Eppleston J, Armstrong A and Watt BR (2010) Selenium supplementation increases wool growth and reduces faecal egg counts of Merino weaners in a selenium-deficient area Animal Production Science 50:688-692
- Watt BR and Eppleston JE (2011) Selenium Nutrition of Sheep and Cattle. District Veterinarian's conference 2011 www.flockandherd.net.au
- Shallow M, Ellis NJS and Judson GJ (1988) Sex-related responses to vitamin B12 and trace mineral supplementation in prime lambs Australian Veterinary Journal 66:8:250-251
- Watt BR (2010) Selenium deficiency in weaned Hereford calves www.flockandherd.net.au
- Watt BR and Staples P (2011) The myocardial form of nutritional muscular dystrophy in calves on clover dominant pasturesmwww.flockandherd.net.au
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