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The effect of parenteral supplementation of vitamin E with selenium on the health and productivity of dairy cattle in the UK
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The Veterinary Journal The Veterinary Journal 177 (2008) 381–387 www.elsevier.com/locate/tvjl
The effect of parenteral supplementation of vitamin E with selenium on the health and productivity of dairy cattle in the UK N. Bourne a, D.C. Wathes a, K.E. Lawrence b, M. McGowan a, R.A. Laven a
b,*
Reproduction, Genes and Development Group, Royal Veterinary College, Hawkshead Campus, North Mymms, Hertfordshire, AL9 7TA, UK b Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand Accepted 8 June 2007
Abstract Recent work has suggested that the recommended intakes of vitamin E for dairy cattle need to be increased, particularly in dry cows. However, these suggestions are based on data from cattle in the USA, which may have significantly different oxidative stresses than European cattle. This study, which involved 594 cattle on three dairy farms, was designed to determine the effect of increased vitamin E supplementation on the health and fertility of UK dairy cows. Cattle were randomly allocated to receive either two intramuscular injections of 2100 mg of vitamin E (and 7 g of sodium selenite) 2 weeks before calving and on the day of calving, or no additional vitamin E supplementation. Although supplementation had no effect on milk yield, reproductive efficiency, or incidence of uterine infections, supplemented cattle had a lower risk of culling and a lower rate of mastitis. These figures were economically significant but not statistically significant at the 10% level. Supplementation reduced the incidence of retained fetal membranes from 6.5% to 3%, an effect which was almost significant at the 5% level. If these data are representative they suggest that vitamin E recommendations for UK cattle should be reassessed. 2007 Elsevier Ltd. All rights reserved. Keywords: Vitamin E; Mastitis; Fertility; Retained fetal membranes; Dry cow; Culling
Introduction Ruminants have no specific dietary requirements for water-soluble vitamins, such as cobalamin, as sufficient amounts to meet requirements are produced by normally functioning rumen microflora. In contrast, there is no ruminal production of the fat soluble vitamins, such as vitamin E, which need to be present in the diet if deficiency-related problems are to be prevented (NRC, 2001a,b). In cattle, the original calculations that determined the requirements for vitamin E were based on data derived from studies investigating the prevention of nutritional myopathy (Allison and Laven, 2000). This is a disease which primarily affects calves, and the requirements for optimum productivity of dairy cattle are highly likely to *
Corresponding author. Tel.: +64 6 356 9099; fax: +64 6 350 5636. E-mail address: [email protected] (R.A. Laven).
1090-0233/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.tvjl.2007.06.006
be significantly different. Furthermore, the recommended intake of 15 mg/kg dry matter (DM) (ARC, 1980) is based on the concentration of vitamin E in feed, which implies that vitamin E requirement is linked to DM. The oxidative stresses encountered by the dairy cow (and thus the physiological requirements for vitamin E) are unlikely to be directly related to DM intake. For example, oxidative stress increases significantly around calving (Castillo et al., 2005), yet DM intake significantly reduces at this time (Grummer et al., 2004). Allison and Laven (2000) reviewed the literature on the effect of vitamin E supplementation on the health and fertility of dairy cows and concluded that there was convincing evidence that vitamin E supplementation significantly above the ARC recommendations could reduce the incidence and/or duration of clinical mastitis. However, they also found little direct evidence for an effect of such supplementation on infectious diseases other than mastitis, or on
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reproductive efficiency. They concluded that it was likely that the ARC (1980) recommended intake of vitamin E for adult dairy cattle was too low for optimum productivity. This is consistent with an NRC review undertaken at the same time which concluded that vitamin E recommendations for dairy cattle should be increased to 0.8 IU/kg for milking cattle and 1.6 IU/kg body weight for dry cattle (NRC, 2001a). As feed intake reduces significantly during the dry period (Hayirli et al., 2002), a single dietary concentration of vitamin E cannot be recommended for the whole dry period, but around 2 weeks pre-partum an intake of 1.6 IU/ kg bodyweight is equivalent to a dietary vitamin E concentration of 105 mg/kg DM (seven times higher than NRC, 1989 recommendations). Most of the data on which Allison and Laven (2000) based their conclusions came from the USA and there was a lack of data from European dairy cattle. This may be important as European cattle are likely to encounter significantly different oxidative stresses from those of US cattle due to differences in management systems. Differences in feed composition can significantly influence oxidant status (Stefanon et al., 2003). For example, European cattle tend to have more exposure to pasture, which because of its high level of polyunsaturated fatty acids can predispose to oxidative stress (Pearce et al., 2005). Differences in production can also influence oxidant status as increased production is associated with increased metabolic activity and thus production of reactive oxygen metabolites (NRC, 2001b). The use of bovine somatotropin may also alter the response to oxidative stress (see, for example, Elvinger et al., 1992). The primary objective of the present study was to determine the effect, under UK conditions, of additional vitamin E supplementation on the periparturient health and fertility of dairy cattle receiving adequate in-feed vitamin E (as determined by ARC, 1980). Materials and methods
All experimental procedures were carried out in accordance with the UK Animal (Scientific Procedures) Act (1986).
Vitamin E supplementation Cattle on each farm were supplemented with dl-a-tocopheryl acetate by intramuscular (IM) injection (Vitenium; Novartis Animal Health). No vitamin E only formulations are authorised for parenteral use in the UK, so Vitenium was selected as it contains the lowest selenium to vitamin E ratio of any available product. All cattle were given 15 mL of Vitenium by IM injection on two occasions, 2 weeks prior to the estimated date of calving and again within 24 h of parturition. Vitenium contains dl-a-tocopheryl acetate and sodium selenite, thus cattle received 2100 mg vitamin E and 7 mg of sodium selenite on each occasion. The parenteral dose of vitamin E was calculated in a previous trial (Bourne et al., 2007b). This dose is equivalent to a supplemented intake of 105 mg/kg DM over a 7-day-period, presuming a feed intake of 10 kg feed per day and an absorption factor of vitamin E across the intestine of 33% (Bender, 1992). Although Bourne et al. (2007b) showed that this dose produced a significant increase in plasma vitamin E for less than 1 week, two doses approximately 14 days apart were used in this study to minimise the risk of selenium toxicity.
Vitamin E intake During the study, samples of dry cow total mixed ration (TMR) were collected weekly from each farm. These were frozen and stored at 20 C. Samples were bulked for each farm into spring (March–May), summer (June–August) and autumn (September–December). High performance liquid chromatography (HPLC) (Manz and Philipp, 1981) was then used to measure the vitamin E concentration of each of the three samples per farm.
Monitoring of vitamin E and selenium status Around 20 cattle on each farm (9–11 from each treatment group) were randomly selected for assessment of plasma vitamin E concentration and erythrocyte glutathione peroxidase (GSH-Px) activity. Blood samples were taken from each cow from the coccygeal vein into heparinised vacutainers on three occasions; 2 weeks pre-partum (prior to injection), 2 weeks postpartum and 8 weeks post-partum. Vitamin E concentrations were measured using HPLC (Vuilleumier et al., 1983), whilst erythrocyte GSH-Px activity was determined by a direct spectrophotometry method (Paglia and Valentine, 1967).
Farms and animals
Production and health monitoring
Three all year-round calving dairy herds in South-East England (Essex) were used for the study. Details of each farm are summarised in Table 1. All cows (1st parity or greater) that had been diagnosed as pregnant by the herd’s veterinarian, and due to calve between March 2003 and the end of December 2003, were enrolled in the study. At drying off, cows were blocked on the basis of parity and expected calving date and then randomly allocated to receive either no additional vitamin E supplementation (control) or parenteral vitamin E supplementation.
Monthly milk yield and somatic cell count (SCC) data for the first 6 months of lactation were derived from monthly records collected by National Milk Records. The incidence of retained fetal membranes (RFM) at a day after calving as well as uterine infection and mastitis were estimated using farm records. Uterine infection was defined as abnormal discharge as observed by farm staff, requiring (severe) or not requiring (mild) veterinary intervention. A mastitis case was determined by the use of standard intra-mammary or parenteral antibiotic mastitis treatment protocols for each herd. For mastitis cases, a new case was defined when treatment for mastitis occurred more than 10 days after previous treatment. Details of services, veterinary pregnancy diagnoses and culling or deaths were also taken from farm records. All data were collected from standard farm records but farmers were not specifically asked to maintain additional health records during the trial.
Table 1 Details of farms involved in the study Milking Farm Mean herd herd size milk yield size (Ha) (L) approx Farm 1 280 Farm 2 480 Farm 3 260
547 3237 1642
6000 9000 8500
Number of cattle allocated
Mean parity Breed (range) of study cows
191 247 166
3.7 (2–8) 2.8 (1–11) 2.6 (1–8)
Jersey Holstein Holstein
Statistical analysis The effect of vitamin E supplementation on vitamin E and selenium status, somatic cell count, and milk yield was evaluated using a univariate
general linear model with farm, treatment and time as the fixed effects. This analysis was undertaken using SPSS 12.0 for Windows (SPSS Inc.). The effect of vitamin E supplementation on fertility was assessed using survival analysis. The cumulative probability of pregnancy for each treatment was calculated using the method of Kaplan and Meier (1958) and plotted from the date of calving. This calculation was repeated for the data for ‘first service’ and for culling. All cows not experiencing the event of interest were censored at day 220 after calving. The Kaplan–Meier procedure estimates the instantaneous risk of the event of interest at any particular time as the ratio of the number with the event at that time to the current ‘‘risk set’’, which is defined to be the set of individuals currently at risk of experiencing the outcome of interest. The logrank test (Peto et al., 1976) was used to test the null hypothesis that there was no difference between the treatment groups in the probability of an event at any time point. To test the hypothesis that treatment was associated with time to first service and time to conception a Cox proportional hazards model (Cox, 1972) was developed with time to event as the outcome variable. ‘Farm’ and ‘cow parity’ were included as explanatory variables to adjust for confounding and test for possible interactions between farm, cow parity and treatment. Time to culling was further modelled parametrically using a Wiebull regression model. The Wiebull distribution is used to model the hazard if it increases or decreases with time and is described by two nonnegative constants; a is called the scale parameter, because it scales the time variable, and b is called the shape parameter, because it determines the shape of the rate function. For the effect of vitamin E on the incidence and severity of uterine infection, the incidence of RFM and the incidence of mastitis, point estimates and confidence intervals for the summary incidence risk ratio and incidence rate ratio were based on formulae provided by Rothman (2002).
Results Of the 604 animals enrolled, 56 were excluded because of a later than anticipated calving date or culling prepartum. Vitamin E intake The vitamin E content of dry cow rations for Farms 1, 2 and 3 were 20.1, 83.2 and 83.8 IU/kg DM, respectively. As it was not possible to record daily feed intakes on farm, vitamin E intakes per kg (as per the NRC, 2001a,b recommendations) could only be estimated. Using farmer estimates of cow weight and estimated feed intakes from Hayirli et al. (2002), at 2 weeks pre-partum, daily intakes of vitamin E were approximately 0.42, 1.32 and 1.33 IU/ kg body weight per day for Farms 1, 2 and 3, respectively. Vitamin E and selenium status There was no effect of treatment on mean plasma vitamin E concentration (P = 0.1). Additionally there were no significant interactions between treatment and farm or time (P > 0.4). The only factors found by the model to have an effect on mean vitamin E concentration were time in relation to calving (P < 0.01) and an interaction between time and farm (P < 0.01). This is summarised in Fig. 1. The data show that, as expected, there was an increase in mean plasma vitamin E concentration after calving (P <
Plasma vitamin E concentration (mg/L)
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383
7
6
5
4 Farm 1 Farm 2 Farm 3
3
2 -2
0
2
4
6
8
Time in relation to calving (weeks) Fig. 1. Effect of farm on change with time in relation to calving of mean plasma vitamin E concentration (SEM). fl indicates time of injection. First blood sample was taken prior to injection. (As there was no significant effect of treatment on vitamin E concentration this figure uses data from both control and treated groups).
0.01). In 2/3 farms this increase was apparent 2 weeks after calving, on Farm 1 it was detected at week 8 only. Using the criteria for vitamin E deficiency defined by Bass et al. (2000), namely <3 mg/L plasma vitamin E, we found that 2 weeks prior to their expected date of calving 44% of sampled cows were deficient. Two weeks after calving this percentage had fallen to 36% (P = 0.45). Six weeks later, none of the sampled cows had plasma vitamin E concentrations <3 mg/L. There were marked differences between farms in the proportion of sampled cows which were deficient. At week 2, the proportion of deficient cows was 38% on Farm 1, 11% on Farm 2 and 69% on Farm 3 (P < 0.001); at week 2 the proportions were 35%, 14% and 48%, respectively (P = 0.13). There was no effect of treatment on GSH-Px activity (P = 0.1). Nor were there any significant interactions between treatment and any other factor (P > 0.4). The only factors found by the model to have a significant effect on mean GSH-Px activity were farm and time in relation to calving (P < 0.001 for both). Mean erythrocyte GSH-Px activities were 404 ± 13.0, 334 ± 13.6 and 322 ± 11.4 for weeks 2, 2 and 8, respectively. Overall there was a trend towards decreased mean GSH-Px as the study progressed, with mean GSH-Px being lower 2 weeks after calving than 2 weeks before, and mean GSH-Px activity 8 weeks after calving being lower than that at the other two time points. At all times, on all farms, no cow had a GSH-Px activity indicative of selenium deficiency (i.e. <55 U/mL RBC) (Underwood and Suttle, 1999). Somatic cell count and milk yield data The effect of farm and treatment on SCC and milk yield are summarised in Table 2. Both farm and time in relation to calving had a significant effect on mean SCC (P < 0.001 and P = 0.045 respectively). However, there was no
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Table 2 Effect of farm and treatment on mean (SEM) log somatic cell count and mean daily milk yield n
Farm 1 Farm 2 Farm 3
Mean log SCC/1000
Mean daily milk yield (kg/day)
Control
Supplemented
Control
Supplemented
Control
Supplemented
88 119 70
87 112 72
1.90 (0.03) 2.05 (0.03) 1.97 (0.03)
1.98 (0.03) 2.06 (0.03) 1.98 (0.03)
25.4 (0.30) 39.0 (0.59) 40.0 (0.43)
25.6 (0.27) 38.3 (0.54) 39.0 (0.43)
significant effect of treatment on mean SCC, nor were there any significant interactions with either time after calving or farm. There was an effect of farm on mean daily milk yield (P < 0.01), however no treatment effect or any significant interactions were detected (P > 0.2 for both). Incidence of retained fetal membranes and uterine infection The effect of treatment on these factors is summarised in Table 3. The incidence of RFM and uterine infection differed between herds (P = 0.54 and P < 0.001 respectively) There were however no interactions between herd and supplementation (P = 0.38) so pooled data from all farms are presented. For RFM, there was a relative risk of 0.45 for supplemented cows compared to controls (95% confidence interval 0.2–1.03, P = 0.055). There was no significant effect of vitamin E supplementation on the incidence of uterine infection, nor on its severity (P > 0.25 for both). Mastitis There was no significant effect of treatment on the number of cows affected with mastitis in the first 200 days of lactation, with 95 cows (34.7%) affected in the control group and 93 in the treated group (34.3%). When the total number of mastitis cases was analysed, there were 141 cases in control cows (55 cases/100 cow years), while for treated cattle there were 126 cases (47 cases/100 cow years), resulting in an incidence rate ratio of 0.86 (95% confidence interval 0.68–1.1) for supplemented compared to control cows (P = 0.23). The incidence of mastitis did not differ between herds (P = 0.65). Fertility The effect of treatment on interval between calving to first service and calving to conception is shown graphically in Fig. 2. The median calving to first service intervals calculated from the Kaplan–Meier plots were 84 days for the control group and 87 days for the supplemented group.
There was no significant difference in time to first service between treatments (P = 0.54 log-rank test). The hazard ratio for time to first insemination with treatment (controlling for farm and cow parity) was 0.93 (95% CI 0.77, 1.13). The median calving to conception intervals calculated from the Kaplan–Meier plots were 140 days for the control group and 154 days for the supplemented group. There was no significant difference in time to conception between treatments (P = 0.83 log-rank test). The hazard ratio for conception with treatment (controlling for farm and cow parity) was 0.97 (95% CI 0.78, 1.2). The analysis for both fertility parameters showed that although there were significant differences between herds in fertility (P < 0.01), there were no significant interactions between treatment, farm or cow parity. Culling Culling rate was not significantly different between herds (P = 0.98). The effect of treatment on the likelihood of being culled is summarised in Fig. 3. The culling rate during the first 220 days of lactation was 46 in the supplemented cows (21.9%) compared to 59 in the control group (26.8%). This was not significant at the 5% level (P = 0.17). The hazard of culling with treatment (controlling for farm and cow parity) was 0.76 (95% CI 0.52, 1.12). Discussion The aim of this study was to assess the effect of increasing vitamin E supplementation through two strategic injections on dairy cattle productivity and health. The rate of supplementation was not as high as some studies (e.g. Erskine et al., 1997) but was chosen as the minimum likely effective rate following previous work (Weiss, 1998). The amount used was based on a previous study (Bourne et al., 2007b), which showed that supplementation with this level of vitamin E significantly increased plasma vitamin E concentration, though for <7 days. Weekly supplementation at the end of the dry period may therefore have been
Table 3 Effect of treatment with vitamin E on the number of cows with retained fetal membranes (RFM) or uterine infection RFM present
Control Supplemented
Uterine infection
No
Yes
% with RFM
None
Mild
Severe
% with infection
259 263
18 8
6.5 3
242 223
7 11
28 37
12.6 17.7
1.0 0.8 0.6 0.4
Probability of conception
0.6 0.4
385
0.2
1.0 0.2
b
0.8
a Probability of first insemination
N. Bourne et al. / The Veterinary Journal 177 (2008) 381–387
No Vitamin E injection Vitamin E injection
0.0
0.0
No Vitamin E injection Vitamin E injection
0
50
100
150
200
Days since calving
0
50
100
150
200
Days since calving
0.9 0.8 0.7 0.6
No Vitamin E injection Vitamin E injection 0.5
Cumulative probability of surviving
1.0
Fig. 2. Kaplan–Meier survival curves showing the cumulative proportions of the population that (a) had received their first service or (b) had conceived as a function of days since calving stratified by treatment.
0
50
100
150
200
Days after calving Fig. 3. Kaplan–Meier survival curves (dashed and solid line) showing the cumulative proportions of the population that had been culled as a function of days since calving stratified by treatment along with fitted Weibull curves (dotted line).
preferable, however a 2-week interval between injections was used to minimise the risk of selenium toxicity. All farms were feeding above the current ARC (1980) recommendation of 15 mg/kg DM, but were estimated to have intakes <1.6 IU/kg bodyweight as recommended by NRC (2001a). The dietary intake of vitamin E varied markedly between farms. This variation was primarily due to differences between farms in the amount of supplementary vitamin E that was fed to the dry cows rather than differences in vitamin E content of the base forage and concentrates. On all three farms the vitamin E concentration in the mineral mix was based on the recommendations of the herd’s nutritional adviser, indicating that ARC (1980) rec-
ommendations on vitamin E intake were not being followed. The effect of time in relation to calving on plasma vitamin E concentration was similar to that reported in previous studies (e.g. Weiss et al., 1994) with mean plasma vitamin E concentrations being the same 2 weeks before and 2 weeks after calving, but increasing significantly thereafter. The correlation between estimated vitamin E intake and status, as measured by plasma vitamin E concentration, was poor. The differences in vitamin E intake between Farms 2 and 3 were small but mean vitamin E concentrations were significantly different and, 2 weeks before calving, there were far more cattle which had plasma vitamin E concentrations <3 ng/mL on Farm 3 than on Farm 2 (69% vs. 11%). Furthermore, cattle on Farm 1 received much less vitamin E than those on Farm 3, yet their plasma vitamin E status was markedly better (38% ‘deficient’ vs. 69%). These data clearly show vitamin E intake is a poor predictor of plasma status. Animals on each farm had similar dry period management and comparable dry period lengths, and when they were sampled all cattle had been on a consistent dry cow diet for at least 40 days, so factors such as time dry or dietary changes were not the cause of the differences. Further research is required to establish the factors which influence plasma vitamin E concentration, and thus its value as a measure of overall vitamin E status. In this study, parenteral supplementation with 2100 mg of vitamin E 2 weeks before and within 24 h of calving had no significant effect on mean plasma vitamin E concentration. This is not unexpected as plasma vitamin E concentration was measured 2 weeks after each injection and Bourne et al. (2007b) showed that the increase in plasma vitamin E concentration after an IM injection of 2100 mg vitamin E was short-lived, with plasma concentrations consistently returning to pre-injection values within 7 days.
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Thus the lack of response of plasma vitamin E concentration to this parenteral supplementation regime does not indicate that it had not improved overall vitamin E status. No significant milk yield response to parenteral vitamin E supplementation was found, indeed on 2/3 farms supplemented cattle produced less milk than unsupplemented cattle, but the differences were small and non-significant. In contrast, Lacetera et al. (1996) reported that cattle supplemented with vitamin E and selenium produced 10% more milk than unsupplemented cattle. However, in this study supplemented cattle received markedly more sodium selenite (30 mg as opposed to 7 mg) and much less vitamin E (150 mg vs. 2100 mg). It is possible that the response reported by Lacetera et al. (1996) was primarily a selenium response rather than a vitamin E one. The results of the current study are consistent with another study which showed no effect on milk yield of vitamin E supplementation at a dose of 250 IU/kg DM (Weiss and Wyatt, 2003). There was no benefit of vitamin E supplementation on SCC. A power analysis prior to the trial found the size of the study had an 80% chance of detecting a reduction in SCC of 30,000; a realistic reduction based on previous work (Smith et al., 1984). The absence of an effect is thus likely to be a true representation, particularly as there was no consistent pattern in the SCC response to supplementation. There was also no significant effect of supplementation on the number of cows affected by mastitis; the power analysis had suggested that there was an 80% chance of detecting a reduction in incidence from 30% to 20%, again a realistic reduction based on previous work (Smith et al., 1984). Although the number of cows with mastitis was not different between control and supplemented groups, the number of cases per affected cow was numerically higher in control animals (P = 0.23). This meant that there were eight fewer cases of mastitis/100 cows/year in treated cattle compared to control cattle. Assuming a cost of mastitis to a farmer of around £131/ case1 (Berry et al., 2004), this reduction alone would justify the use of this vitamin E regime. More data are therefore needed to confirm if this is a real effect. The present study found no evidence of an effect of vitamin E supplementation on fertility, with the Kaplan–Meier curves for treated and control cows being very similar. The increase of 14 days in the median calving to conception interval in the supplemented cows compared to the control cows would appear to suggest that supplementation with vitamin E had a deleterious effect on fertility. However, the apparent difference in the median values was confounded by culling; fewer cattle were culled in the treatment group which extended the median calving to conception interval for this group. The Kaplan–Meier curves take culling into account and are therefore a much more sensitive indicator of the effect of supplementation on fertility than a single estimate such as median calving
1
£1 = approx. €1.47; US$1.97.
to conception interval. This finding is consistent with the conclusions of Allison and Laven (2000) who stated that the evidence for an effect of vitamin E supplementation on reproductive efficiency was very limited. This study found no beneficial effect of vitamin E supplementation on the incidence or severity of uterine infection, consistent with the findings of LeBlanc et al. (2002). There was, however, a beneficial effect of supplementation on the incidence of RFM which was almost significant at the 5% level (P = 0.055). This effect is consistent with findings from a meta-analysis of other studies of the effect of vitamin E supplementation on RFM (Bourne et al., 2007a). The reduction in incidence of RFM seen in this study (from 6.5% to 3%) would result in an economic benefit to the farm of in the region of £900/100 cows (based on a cost of £250 per case (Kossaibati and Esslemont, 1997). This is approximately the same as the cost of two injections of Vitenium. Thus, for this regime of parenteral vitamin E supplementation to be economically beneficial, either the reduction in the incidence of RFM would have to be greater than we found in this study or there would have to be other proven economic benefits (such as reduction in the incidence of clinical mastitis). The former might occur if the product was used on a farm with a higher incidence of RFM than those farms that participated in our study. Cattle supplemented with vitamin E were less likely to be culled than unsupplemented cattle, with 5% fewer animals culled in the supplemented group. Unfortunately the study lacked the statistical power required to investigate the effect of supplementation on culling rates. However, the observed reduction in the culling rate would have been worth approximately £5,000/100 cows (Kossaibati and Esslemont, 1997), a figure which, if representative, would more than justify the supplementation regime used in this study. Further research is needed to confirm if this apparent benefit is real. Conclusions This study found that a supplementation regime using only two injections of vitamin E in the late dry period reduced the incidence of RFM after calving and possibly had a positive benefit on culling and the number of mastitis cases. If these benefits are representative of the effects of vitamin E supplementation they would make this regime economically beneficial. However, only the effect on RFM approached significance at the 5% level. The results are not sufficient therefore to recommend parenteral vitamin E supplementation to all dry cows fed <1.6 mg vitamin E per kg bodyweight, but do strongly suggest that vitamin E recommendations for European cattle should be reassessed by testing on larger numbers of cows. Acknowledgements This work was supported by funding from UK government’s Department for Environment Food and Rural Af-
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fairs (Defra) and DSM Nutritional Products with further funding from British Cattle Veterinary Association (BCVA) for the metabolic analyses. References Allison, R.D., Laven, R.A., 2000. Effect of vitamin E supplementation on the health and fertility of dairy cows: a review. Veterinary Record 147, 703–708. Agricultural Research Council, 1980. Selenium and Vitamin E. In: The Nutrient Requirements of Ruminant Livestock. Wiley, Oxford, UK, pp. 243–251. Bass, R.T., Swecker, W.S., Stallings, C.C., 2000. Effects of supplemental parenteral administration of vitamin E and selenium to Jerseys and Holsteins during the nonlactating period. American Journal of Veterinary Research 61, 1052–1056. Bender, D.A., 1992. Nutritional Biochemistry of the Vitamins. Cambridge University Press. Berry, E.A., Hogeveen, H., Hillerton, J.E., 2004. Decision tree analysis to evaluate dry cow strategies under UK conditions. Journal of Dairy Research 71, 409–418. Bourne, N., Laven, R., Wathes, D.C., Martinez, T., McGowan, M., 2007a. A meta-analysis of the effects of vitamin-E supplementation on the incidence of retained foetal membranes in dairy cows. Theriogenology 67, 494–501. Bourne, N., Wathes, D.C., McGowan, M., Laven, R.A., 2007b. A comparison of the effects of parenteral and oral administration of supplementary vitamin E on plasma vitamin E concentrations in dairy cows at different stages of lactation. Livestock Science 106, 57–64. Castillo, C., Hernandez, J., Bravo, A., Lopez-Alonso, M., Pereira, V., Benedito, J.L., 2005. Oxidative status during late pregnancy and early lactation in dairy cows. The Veterinary Journal 169, 286–292. Cox, D.R., 1972. Regression models and life tables. Journal of the Royal Statistical Society Series B 34, 187–220. Elvinger, F., Natzke, R.P., Hansen, P.J., 1992. Interactions of heat stress and bovine somatotropin affecting physiology and immunology of lactating cows. Journal of Dairy Science 75, 449–462. Erskine, R.J., Bartlett, P.C., Herdt, T., Gaston, P., 1997. Effects of parenteral administration of vitamin E on health of peri-parturient dairy cows. Journal of the American Veterinary Medicine Association 211, 466–469. Grummer, R.R., Mashek, D.G., Hayırlı, A., 2004. Dry matter intake and energy balance in the transition period. Veterinary Clinics of North America, Food Animal Practice 20, 447–470. Hayirli, A., Grummer, R.R., Nordheim, E.V., Crump, P.M., 2002. Animal and dietary factors affecting feed intake during the prefresh transition period in Holsteins. Journal of Dairy Science 85, 3430–3443. Kaplan, E.L., Meier, P., 1958. Nonparametric estimation from incomplete observations. Journal of the American Statistical Association 53, 448– 457. Kossaibati, M.A., Esslemont, R.J., 1997. The costs of production diseases in dairy herds in England. The Veterinary Journal 154, 41–51. Lacetera, N., Bernabucci, U., Ronchi, B., Nardone, A., 1996. Effects of selenium and vitamin E administration during a late stage of
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pregnancy on colostrum and milk production in dairy cows and on passive immunity and growth of their offspring. American Journal of Veterinary Research 57, 1776–1780. LeBlanc, S.J., Duffield, T.F., Leslie, K.E., Bateman, K.G., TenHag, J., Walton, J.S., Johnson, W.H., 2002. The effect of prepartum injection of vitamin E on health in transition dairy cows. Journal of Dairy Science 85, 1416–1426. Manz, U., Philipp, K., 1981. A method for the routine determination of tocopherols in animal feed and human feedstuffs with the aid of high performance liquid chromatography. International Journal of Vitamin and Nutrition Research 51, 342–348. NRC, 1989. Dry matter intake and nutrient requirement tables. In: Nutrient Requirements of Dairy Cattle, National Academy of Sciences – National Research Council. National Academy Press, US, p. 87. NRC, 2001a. Nutrient requirement tables. In: Nutrient Requirements of Dairy Cattle, National Academy of Sciences - National Research Council. National Academy Press, US, p. 270. NRC, 2001b. Oxidative stress. In: Nutrient Requirements of Dairy Cattle, National Academy of Sciences - National Research Council. National Academy Press, US, p. 191. Paglia, D.E., Valentine, W.N., 1967. Studies on the quantitative and qualitative characterization of erythrocyte glutathione peroxidase. Journal of Laboratory Clinical Medicine 70, 158–169. Pearce, K.L., Masters, D.G., Smith, G.M., Jacob, R.H., Pethick, D.W., 2005. Plasma and tissue a-tocopherol concentrations and meat colour stability in sheep grazing saltbush (Atriplex spp.). Australian Journal of Agricultural Research 56, 663–672. Peto, R., Pike, M.C., Armitage, P., Breslow, N.E., Cox, D.R., Howard, S.V., Mantel, N., McPherson, K., Peto, J., Smith, P.G., 1976. Design and analysis of randomised clinical trials requiring prolonged observation of each patient. British Journal of Cancer 34, 585–612. Rothman, K.J., 2002. Epidemiology. An Introduction. Oxford University Press, London, UK, pp 130–143. Smith, K.L., Harrison, J.H., Hancock, D.D., Todhunter, D.A., Conrad, H.R., 1984. Effect of vitamin E and selenium supplementation on incidence of clinical mastitis and duration of clinical symptoms. Journal of Dairy Science 67, 1293–1300. Stefanon, B., Colitti, M., Gabai, G., Knight, C.H., Wilde, C.J., 2003. Mammary apoptosis and lactation persistency in dairy animals. Journal of Dairy Research 69, 37–52. Underwood, E.J., Suttle, N.F., 1999. Selenium. In: The Mineral Nutrition of Livestock. Cabi Publishing, Oxon, UK, pp. 421–476. Vuilleumier, J.P., Keller, H.E., Gysel, D., Hunziker, F., 1983. Clinical chemical methods for the routine assessment of the vitamin status in human populations, Part 1: The fat soluble vitamins A and E, and bcarotene. International Journal of Vitamin and Nutrition Research 56, 265–272. Weiss, W.P., 1998. Vitamin requirements for dairy cows. Journal of Dairy Science 81, 2493–2501. Weiss, W.P., Hogan, J.S., Smith, K.L., Williams, S.N., 1994. Effect of dietary fat and vitamin E on (-tocopherol and (-carotene in blood of peripartum cows. Journal of Dairy Science 77, 1422–1429. Weiss, W.P., Wyatt, D.J., 2003. Effect of dietary fat and vitamin E on atocopherol in milk from dairy cows. Journal of Dairy Science 86, 3582–3591.
The Veterinary Journal The Veterinary Journal 177 (2008) 381–387 www.elsevier.com/locate/tvjl
The effect of parenteral supplementation of vitamin E with selenium on the health and productivity of dairy cattle in the UK N. Bourne a, D.C. Wathes a, K.E. Lawrence b, M. McGowan a, R.A. Laven a
b,*
Reproduction, Genes and Development Group, Royal Veterinary College, Hawkshead Campus, North Mymms, Hertfordshire, AL9 7TA, UK b Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand Accepted 8 June 2007
Abstract Recent work has suggested that the recommended intakes of vitamin E for dairy cattle need to be increased, particularly in dry cows. However, these suggestions are based on data from cattle in the USA, which may have significantly different oxidative stresses than European cattle. This study, which involved 594 cattle on three dairy farms, was designed to determine the effect of increased vitamin E supplementation on the health and fertility of UK dairy cows. Cattle were randomly allocated to receive either two intramuscular injections of 2100 mg of vitamin E (and 7 g of sodium selenite) 2 weeks before calving and on the day of calving, or no additional vitamin E supplementation. Although supplementation had no effect on milk yield, reproductive efficiency, or incidence of uterine infections, supplemented cattle had a lower risk of culling and a lower rate of mastitis. These figures were economically significant but not statistically significant at the 10% level. Supplementation reduced the incidence of retained fetal membranes from 6.5% to 3%, an effect which was almost significant at the 5% level. If these data are representative they suggest that vitamin E recommendations for UK cattle should be reassessed. 2007 Elsevier Ltd. All rights reserved. Keywords: Vitamin E; Mastitis; Fertility; Retained fetal membranes; Dry cow; Culling
Introduction Ruminants have no specific dietary requirements for water-soluble vitamins, such as cobalamin, as sufficient amounts to meet requirements are produced by normally functioning rumen microflora. In contrast, there is no ruminal production of the fat soluble vitamins, such as vitamin E, which need to be present in the diet if deficiency-related problems are to be prevented (NRC, 2001a,b). In cattle, the original calculations that determined the requirements for vitamin E were based on data derived from studies investigating the prevention of nutritional myopathy (Allison and Laven, 2000). This is a disease which primarily affects calves, and the requirements for optimum productivity of dairy cattle are highly likely to *
Corresponding author. Tel.: +64 6 356 9099; fax: +64 6 350 5636. E-mail address: [email protected] (R.A. Laven).
1090-0233/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.tvjl.2007.06.006
be significantly different. Furthermore, the recommended intake of 15 mg/kg dry matter (DM) (ARC, 1980) is based on the concentration of vitamin E in feed, which implies that vitamin E requirement is linked to DM. The oxidative stresses encountered by the dairy cow (and thus the physiological requirements for vitamin E) are unlikely to be directly related to DM intake. For example, oxidative stress increases significantly around calving (Castillo et al., 2005), yet DM intake significantly reduces at this time (Grummer et al., 2004). Allison and Laven (2000) reviewed the literature on the effect of vitamin E supplementation on the health and fertility of dairy cows and concluded that there was convincing evidence that vitamin E supplementation significantly above the ARC recommendations could reduce the incidence and/or duration of clinical mastitis. However, they also found little direct evidence for an effect of such supplementation on infectious diseases other than mastitis, or on
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reproductive efficiency. They concluded that it was likely that the ARC (1980) recommended intake of vitamin E for adult dairy cattle was too low for optimum productivity. This is consistent with an NRC review undertaken at the same time which concluded that vitamin E recommendations for dairy cattle should be increased to 0.8 IU/kg for milking cattle and 1.6 IU/kg body weight for dry cattle (NRC, 2001a). As feed intake reduces significantly during the dry period (Hayirli et al., 2002), a single dietary concentration of vitamin E cannot be recommended for the whole dry period, but around 2 weeks pre-partum an intake of 1.6 IU/ kg bodyweight is equivalent to a dietary vitamin E concentration of 105 mg/kg DM (seven times higher than NRC, 1989 recommendations). Most of the data on which Allison and Laven (2000) based their conclusions came from the USA and there was a lack of data from European dairy cattle. This may be important as European cattle are likely to encounter significantly different oxidative stresses from those of US cattle due to differences in management systems. Differences in feed composition can significantly influence oxidant status (Stefanon et al., 2003). For example, European cattle tend to have more exposure to pasture, which because of its high level of polyunsaturated fatty acids can predispose to oxidative stress (Pearce et al., 2005). Differences in production can also influence oxidant status as increased production is associated with increased metabolic activity and thus production of reactive oxygen metabolites (NRC, 2001b). The use of bovine somatotropin may also alter the response to oxidative stress (see, for example, Elvinger et al., 1992). The primary objective of the present study was to determine the effect, under UK conditions, of additional vitamin E supplementation on the periparturient health and fertility of dairy cattle receiving adequate in-feed vitamin E (as determined by ARC, 1980). Materials and methods
All experimental procedures were carried out in accordance with the UK Animal (Scientific Procedures) Act (1986).
Vitamin E supplementation Cattle on each farm were supplemented with dl-a-tocopheryl acetate by intramuscular (IM) injection (Vitenium; Novartis Animal Health). No vitamin E only formulations are authorised for parenteral use in the UK, so Vitenium was selected as it contains the lowest selenium to vitamin E ratio of any available product. All cattle were given 15 mL of Vitenium by IM injection on two occasions, 2 weeks prior to the estimated date of calving and again within 24 h of parturition. Vitenium contains dl-a-tocopheryl acetate and sodium selenite, thus cattle received 2100 mg vitamin E and 7 mg of sodium selenite on each occasion. The parenteral dose of vitamin E was calculated in a previous trial (Bourne et al., 2007b). This dose is equivalent to a supplemented intake of 105 mg/kg DM over a 7-day-period, presuming a feed intake of 10 kg feed per day and an absorption factor of vitamin E across the intestine of 33% (Bender, 1992). Although Bourne et al. (2007b) showed that this dose produced a significant increase in plasma vitamin E for less than 1 week, two doses approximately 14 days apart were used in this study to minimise the risk of selenium toxicity.
Vitamin E intake During the study, samples of dry cow total mixed ration (TMR) were collected weekly from each farm. These were frozen and stored at 20 C. Samples were bulked for each farm into spring (March–May), summer (June–August) and autumn (September–December). High performance liquid chromatography (HPLC) (Manz and Philipp, 1981) was then used to measure the vitamin E concentration of each of the three samples per farm.
Monitoring of vitamin E and selenium status Around 20 cattle on each farm (9–11 from each treatment group) were randomly selected for assessment of plasma vitamin E concentration and erythrocyte glutathione peroxidase (GSH-Px) activity. Blood samples were taken from each cow from the coccygeal vein into heparinised vacutainers on three occasions; 2 weeks pre-partum (prior to injection), 2 weeks postpartum and 8 weeks post-partum. Vitamin E concentrations were measured using HPLC (Vuilleumier et al., 1983), whilst erythrocyte GSH-Px activity was determined by a direct spectrophotometry method (Paglia and Valentine, 1967).
Farms and animals
Production and health monitoring
Three all year-round calving dairy herds in South-East England (Essex) were used for the study. Details of each farm are summarised in Table 1. All cows (1st parity or greater) that had been diagnosed as pregnant by the herd’s veterinarian, and due to calve between March 2003 and the end of December 2003, were enrolled in the study. At drying off, cows were blocked on the basis of parity and expected calving date and then randomly allocated to receive either no additional vitamin E supplementation (control) or parenteral vitamin E supplementation.
Monthly milk yield and somatic cell count (SCC) data for the first 6 months of lactation were derived from monthly records collected by National Milk Records. The incidence of retained fetal membranes (RFM) at a day after calving as well as uterine infection and mastitis were estimated using farm records. Uterine infection was defined as abnormal discharge as observed by farm staff, requiring (severe) or not requiring (mild) veterinary intervention. A mastitis case was determined by the use of standard intra-mammary or parenteral antibiotic mastitis treatment protocols for each herd. For mastitis cases, a new case was defined when treatment for mastitis occurred more than 10 days after previous treatment. Details of services, veterinary pregnancy diagnoses and culling or deaths were also taken from farm records. All data were collected from standard farm records but farmers were not specifically asked to maintain additional health records during the trial.
Table 1 Details of farms involved in the study Milking Farm Mean herd herd size milk yield size (Ha) (L) approx Farm 1 280 Farm 2 480 Farm 3 260
547 3237 1642
6000 9000 8500
Number of cattle allocated
Mean parity Breed (range) of study cows
191 247 166
3.7 (2–8) 2.8 (1–11) 2.6 (1–8)
Jersey Holstein Holstein
Statistical analysis The effect of vitamin E supplementation on vitamin E and selenium status, somatic cell count, and milk yield was evaluated using a univariate
general linear model with farm, treatment and time as the fixed effects. This analysis was undertaken using SPSS 12.0 for Windows (SPSS Inc.). The effect of vitamin E supplementation on fertility was assessed using survival analysis. The cumulative probability of pregnancy for each treatment was calculated using the method of Kaplan and Meier (1958) and plotted from the date of calving. This calculation was repeated for the data for ‘first service’ and for culling. All cows not experiencing the event of interest were censored at day 220 after calving. The Kaplan–Meier procedure estimates the instantaneous risk of the event of interest at any particular time as the ratio of the number with the event at that time to the current ‘‘risk set’’, which is defined to be the set of individuals currently at risk of experiencing the outcome of interest. The logrank test (Peto et al., 1976) was used to test the null hypothesis that there was no difference between the treatment groups in the probability of an event at any time point. To test the hypothesis that treatment was associated with time to first service and time to conception a Cox proportional hazards model (Cox, 1972) was developed with time to event as the outcome variable. ‘Farm’ and ‘cow parity’ were included as explanatory variables to adjust for confounding and test for possible interactions between farm, cow parity and treatment. Time to culling was further modelled parametrically using a Wiebull regression model. The Wiebull distribution is used to model the hazard if it increases or decreases with time and is described by two nonnegative constants; a is called the scale parameter, because it scales the time variable, and b is called the shape parameter, because it determines the shape of the rate function. For the effect of vitamin E on the incidence and severity of uterine infection, the incidence of RFM and the incidence of mastitis, point estimates and confidence intervals for the summary incidence risk ratio and incidence rate ratio were based on formulae provided by Rothman (2002).
Results Of the 604 animals enrolled, 56 were excluded because of a later than anticipated calving date or culling prepartum. Vitamin E intake The vitamin E content of dry cow rations for Farms 1, 2 and 3 were 20.1, 83.2 and 83.8 IU/kg DM, respectively. As it was not possible to record daily feed intakes on farm, vitamin E intakes per kg (as per the NRC, 2001a,b recommendations) could only be estimated. Using farmer estimates of cow weight and estimated feed intakes from Hayirli et al. (2002), at 2 weeks pre-partum, daily intakes of vitamin E were approximately 0.42, 1.32 and 1.33 IU/ kg body weight per day for Farms 1, 2 and 3, respectively. Vitamin E and selenium status There was no effect of treatment on mean plasma vitamin E concentration (P = 0.1). Additionally there were no significant interactions between treatment and farm or time (P > 0.4). The only factors found by the model to have an effect on mean vitamin E concentration were time in relation to calving (P < 0.01) and an interaction between time and farm (P < 0.01). This is summarised in Fig. 1. The data show that, as expected, there was an increase in mean plasma vitamin E concentration after calving (P <
Plasma vitamin E concentration (mg/L)
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383
7
6
5
4 Farm 1 Farm 2 Farm 3
3
2 -2
0
2
4
6
8
Time in relation to calving (weeks) Fig. 1. Effect of farm on change with time in relation to calving of mean plasma vitamin E concentration (SEM). fl indicates time of injection. First blood sample was taken prior to injection. (As there was no significant effect of treatment on vitamin E concentration this figure uses data from both control and treated groups).
0.01). In 2/3 farms this increase was apparent 2 weeks after calving, on Farm 1 it was detected at week 8 only. Using the criteria for vitamin E deficiency defined by Bass et al. (2000), namely <3 mg/L plasma vitamin E, we found that 2 weeks prior to their expected date of calving 44% of sampled cows were deficient. Two weeks after calving this percentage had fallen to 36% (P = 0.45). Six weeks later, none of the sampled cows had plasma vitamin E concentrations <3 mg/L. There were marked differences between farms in the proportion of sampled cows which were deficient. At week 2, the proportion of deficient cows was 38% on Farm 1, 11% on Farm 2 and 69% on Farm 3 (P < 0.001); at week 2 the proportions were 35%, 14% and 48%, respectively (P = 0.13). There was no effect of treatment on GSH-Px activity (P = 0.1). Nor were there any significant interactions between treatment and any other factor (P > 0.4). The only factors found by the model to have a significant effect on mean GSH-Px activity were farm and time in relation to calving (P < 0.001 for both). Mean erythrocyte GSH-Px activities were 404 ± 13.0, 334 ± 13.6 and 322 ± 11.4 for weeks 2, 2 and 8, respectively. Overall there was a trend towards decreased mean GSH-Px as the study progressed, with mean GSH-Px being lower 2 weeks after calving than 2 weeks before, and mean GSH-Px activity 8 weeks after calving being lower than that at the other two time points. At all times, on all farms, no cow had a GSH-Px activity indicative of selenium deficiency (i.e. <55 U/mL RBC) (Underwood and Suttle, 1999). Somatic cell count and milk yield data The effect of farm and treatment on SCC and milk yield are summarised in Table 2. Both farm and time in relation to calving had a significant effect on mean SCC (P < 0.001 and P = 0.045 respectively). However, there was no
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Table 2 Effect of farm and treatment on mean (SEM) log somatic cell count and mean daily milk yield n
Farm 1 Farm 2 Farm 3
Mean log SCC/1000
Mean daily milk yield (kg/day)
Control
Supplemented
Control
Supplemented
Control
Supplemented
88 119 70
87 112 72
1.90 (0.03) 2.05 (0.03) 1.97 (0.03)
1.98 (0.03) 2.06 (0.03) 1.98 (0.03)
25.4 (0.30) 39.0 (0.59) 40.0 (0.43)
25.6 (0.27) 38.3 (0.54) 39.0 (0.43)
significant effect of treatment on mean SCC, nor were there any significant interactions with either time after calving or farm. There was an effect of farm on mean daily milk yield (P < 0.01), however no treatment effect or any significant interactions were detected (P > 0.2 for both). Incidence of retained fetal membranes and uterine infection The effect of treatment on these factors is summarised in Table 3. The incidence of RFM and uterine infection differed between herds (P = 0.54 and P < 0.001 respectively) There were however no interactions between herd and supplementation (P = 0.38) so pooled data from all farms are presented. For RFM, there was a relative risk of 0.45 for supplemented cows compared to controls (95% confidence interval 0.2–1.03, P = 0.055). There was no significant effect of vitamin E supplementation on the incidence of uterine infection, nor on its severity (P > 0.25 for both). Mastitis There was no significant effect of treatment on the number of cows affected with mastitis in the first 200 days of lactation, with 95 cows (34.7%) affected in the control group and 93 in the treated group (34.3%). When the total number of mastitis cases was analysed, there were 141 cases in control cows (55 cases/100 cow years), while for treated cattle there were 126 cases (47 cases/100 cow years), resulting in an incidence rate ratio of 0.86 (95% confidence interval 0.68–1.1) for supplemented compared to control cows (P = 0.23). The incidence of mastitis did not differ between herds (P = 0.65). Fertility The effect of treatment on interval between calving to first service and calving to conception is shown graphically in Fig. 2. The median calving to first service intervals calculated from the Kaplan–Meier plots were 84 days for the control group and 87 days for the supplemented group.
There was no significant difference in time to first service between treatments (P = 0.54 log-rank test). The hazard ratio for time to first insemination with treatment (controlling for farm and cow parity) was 0.93 (95% CI 0.77, 1.13). The median calving to conception intervals calculated from the Kaplan–Meier plots were 140 days for the control group and 154 days for the supplemented group. There was no significant difference in time to conception between treatments (P = 0.83 log-rank test). The hazard ratio for conception with treatment (controlling for farm and cow parity) was 0.97 (95% CI 0.78, 1.2). The analysis for both fertility parameters showed that although there were significant differences between herds in fertility (P < 0.01), there were no significant interactions between treatment, farm or cow parity. Culling Culling rate was not significantly different between herds (P = 0.98). The effect of treatment on the likelihood of being culled is summarised in Fig. 3. The culling rate during the first 220 days of lactation was 46 in the supplemented cows (21.9%) compared to 59 in the control group (26.8%). This was not significant at the 5% level (P = 0.17). The hazard of culling with treatment (controlling for farm and cow parity) was 0.76 (95% CI 0.52, 1.12). Discussion The aim of this study was to assess the effect of increasing vitamin E supplementation through two strategic injections on dairy cattle productivity and health. The rate of supplementation was not as high as some studies (e.g. Erskine et al., 1997) but was chosen as the minimum likely effective rate following previous work (Weiss, 1998). The amount used was based on a previous study (Bourne et al., 2007b), which showed that supplementation with this level of vitamin E significantly increased plasma vitamin E concentration, though for <7 days. Weekly supplementation at the end of the dry period may therefore have been
Table 3 Effect of treatment with vitamin E on the number of cows with retained fetal membranes (RFM) or uterine infection RFM present
Control Supplemented
Uterine infection
No
Yes
% with RFM
None
Mild
Severe
% with infection
259 263
18 8
6.5 3
242 223
7 11
28 37
12.6 17.7
1.0 0.8 0.6 0.4
Probability of conception
0.6 0.4
385
0.2
1.0 0.2
b
0.8
a Probability of first insemination
N. Bourne et al. / The Veterinary Journal 177 (2008) 381–387
No Vitamin E injection Vitamin E injection
0.0
0.0
No Vitamin E injection Vitamin E injection
0
50
100
150
200
Days since calving
0
50
100
150
200
Days since calving
0.9 0.8 0.7 0.6
No Vitamin E injection Vitamin E injection 0.5
Cumulative probability of surviving
1.0
Fig. 2. Kaplan–Meier survival curves showing the cumulative proportions of the population that (a) had received their first service or (b) had conceived as a function of days since calving stratified by treatment.
0
50
100
150
200
Days after calving Fig. 3. Kaplan–Meier survival curves (dashed and solid line) showing the cumulative proportions of the population that had been culled as a function of days since calving stratified by treatment along with fitted Weibull curves (dotted line).
preferable, however a 2-week interval between injections was used to minimise the risk of selenium toxicity. All farms were feeding above the current ARC (1980) recommendation of 15 mg/kg DM, but were estimated to have intakes <1.6 IU/kg bodyweight as recommended by NRC (2001a). The dietary intake of vitamin E varied markedly between farms. This variation was primarily due to differences between farms in the amount of supplementary vitamin E that was fed to the dry cows rather than differences in vitamin E content of the base forage and concentrates. On all three farms the vitamin E concentration in the mineral mix was based on the recommendations of the herd’s nutritional adviser, indicating that ARC (1980) rec-
ommendations on vitamin E intake were not being followed. The effect of time in relation to calving on plasma vitamin E concentration was similar to that reported in previous studies (e.g. Weiss et al., 1994) with mean plasma vitamin E concentrations being the same 2 weeks before and 2 weeks after calving, but increasing significantly thereafter. The correlation between estimated vitamin E intake and status, as measured by plasma vitamin E concentration, was poor. The differences in vitamin E intake between Farms 2 and 3 were small but mean vitamin E concentrations were significantly different and, 2 weeks before calving, there were far more cattle which had plasma vitamin E concentrations <3 ng/mL on Farm 3 than on Farm 2 (69% vs. 11%). Furthermore, cattle on Farm 1 received much less vitamin E than those on Farm 3, yet their plasma vitamin E status was markedly better (38% ‘deficient’ vs. 69%). These data clearly show vitamin E intake is a poor predictor of plasma status. Animals on each farm had similar dry period management and comparable dry period lengths, and when they were sampled all cattle had been on a consistent dry cow diet for at least 40 days, so factors such as time dry or dietary changes were not the cause of the differences. Further research is required to establish the factors which influence plasma vitamin E concentration, and thus its value as a measure of overall vitamin E status. In this study, parenteral supplementation with 2100 mg of vitamin E 2 weeks before and within 24 h of calving had no significant effect on mean plasma vitamin E concentration. This is not unexpected as plasma vitamin E concentration was measured 2 weeks after each injection and Bourne et al. (2007b) showed that the increase in plasma vitamin E concentration after an IM injection of 2100 mg vitamin E was short-lived, with plasma concentrations consistently returning to pre-injection values within 7 days.
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Thus the lack of response of plasma vitamin E concentration to this parenteral supplementation regime does not indicate that it had not improved overall vitamin E status. No significant milk yield response to parenteral vitamin E supplementation was found, indeed on 2/3 farms supplemented cattle produced less milk than unsupplemented cattle, but the differences were small and non-significant. In contrast, Lacetera et al. (1996) reported that cattle supplemented with vitamin E and selenium produced 10% more milk than unsupplemented cattle. However, in this study supplemented cattle received markedly more sodium selenite (30 mg as opposed to 7 mg) and much less vitamin E (150 mg vs. 2100 mg). It is possible that the response reported by Lacetera et al. (1996) was primarily a selenium response rather than a vitamin E one. The results of the current study are consistent with another study which showed no effect on milk yield of vitamin E supplementation at a dose of 250 IU/kg DM (Weiss and Wyatt, 2003). There was no benefit of vitamin E supplementation on SCC. A power analysis prior to the trial found the size of the study had an 80% chance of detecting a reduction in SCC of 30,000; a realistic reduction based on previous work (Smith et al., 1984). The absence of an effect is thus likely to be a true representation, particularly as there was no consistent pattern in the SCC response to supplementation. There was also no significant effect of supplementation on the number of cows affected by mastitis; the power analysis had suggested that there was an 80% chance of detecting a reduction in incidence from 30% to 20%, again a realistic reduction based on previous work (Smith et al., 1984). Although the number of cows with mastitis was not different between control and supplemented groups, the number of cases per affected cow was numerically higher in control animals (P = 0.23). This meant that there were eight fewer cases of mastitis/100 cows/year in treated cattle compared to control cattle. Assuming a cost of mastitis to a farmer of around £131/ case1 (Berry et al., 2004), this reduction alone would justify the use of this vitamin E regime. More data are therefore needed to confirm if this is a real effect. The present study found no evidence of an effect of vitamin E supplementation on fertility, with the Kaplan–Meier curves for treated and control cows being very similar. The increase of 14 days in the median calving to conception interval in the supplemented cows compared to the control cows would appear to suggest that supplementation with vitamin E had a deleterious effect on fertility. However, the apparent difference in the median values was confounded by culling; fewer cattle were culled in the treatment group which extended the median calving to conception interval for this group. The Kaplan–Meier curves take culling into account and are therefore a much more sensitive indicator of the effect of supplementation on fertility than a single estimate such as median calving
1
£1 = approx. €1.47; US$1.97.
to conception interval. This finding is consistent with the conclusions of Allison and Laven (2000) who stated that the evidence for an effect of vitamin E supplementation on reproductive efficiency was very limited. This study found no beneficial effect of vitamin E supplementation on the incidence or severity of uterine infection, consistent with the findings of LeBlanc et al. (2002). There was, however, a beneficial effect of supplementation on the incidence of RFM which was almost significant at the 5% level (P = 0.055). This effect is consistent with findings from a meta-analysis of other studies of the effect of vitamin E supplementation on RFM (Bourne et al., 2007a). The reduction in incidence of RFM seen in this study (from 6.5% to 3%) would result in an economic benefit to the farm of in the region of £900/100 cows (based on a cost of £250 per case (Kossaibati and Esslemont, 1997). This is approximately the same as the cost of two injections of Vitenium. Thus, for this regime of parenteral vitamin E supplementation to be economically beneficial, either the reduction in the incidence of RFM would have to be greater than we found in this study or there would have to be other proven economic benefits (such as reduction in the incidence of clinical mastitis). The former might occur if the product was used on a farm with a higher incidence of RFM than those farms that participated in our study. Cattle supplemented with vitamin E were less likely to be culled than unsupplemented cattle, with 5% fewer animals culled in the supplemented group. Unfortunately the study lacked the statistical power required to investigate the effect of supplementation on culling rates. However, the observed reduction in the culling rate would have been worth approximately £5,000/100 cows (Kossaibati and Esslemont, 1997), a figure which, if representative, would more than justify the supplementation regime used in this study. Further research is needed to confirm if this apparent benefit is real. Conclusions This study found that a supplementation regime using only two injections of vitamin E in the late dry period reduced the incidence of RFM after calving and possibly had a positive benefit on culling and the number of mastitis cases. If these benefits are representative of the effects of vitamin E supplementation they would make this regime economically beneficial. However, only the effect on RFM approached significance at the 5% level. The results are not sufficient therefore to recommend parenteral vitamin E supplementation to all dry cows fed <1.6 mg vitamin E per kg bodyweight, but do strongly suggest that vitamin E recommendations for European cattle should be reassessed by testing on larger numbers of cows. Acknowledgements This work was supported by funding from UK government’s Department for Environment Food and Rural Af-
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