MILK DEVELOPMENT COUNCIL VASECTOMISED BULLS

Transcription

1 MILK DEVELOPMENT COUNCIL VASECTOMISED BULLS Project No. 02/T1/04 1

2 2 A cost-benefit study on the use of vasectomised bulls as an aid to heat detection in UK dairy herds. Paddy Gordon MA VetMB CertCHP MRCVS Shepton Veterinary Group, Allyn Saxon Drive, Shepton Mallet, Somerset BA4 5QH Tel , Fax , vet@sheptonvet.com

3 3 Contents Page Number 1.0 Executive Summary 3 Report Body 2.0 Background Objectives Study design Study plan 4.2 Study personnel 4.3 Study farms 4.4 Bull selection 4.5 Data recording 4.6 Record analysis 4.7 Fertility analysis 4.8 Behavioural analysis 4.9 Progesterone data analysis 4.10 Farmer questionnaire 5.0 Results Submission rates 5.2 Calving-1 st service interval 5.3 Conception rates 5.4 Bull activity 5.5 Cow oestrus behaviour 5.6 Progesterone data 6.0 Bull health Cost-benefit analysis Farmer questionnaire Farmer recommendations Discussion Conclusion 26 Appendix 1 27 Table1 Table of fertility results Table 2 Table of behaviour results Table 3 Table of progesterone results Appendix 2 Recording sheets and farmer questionnaire 31 Appendix 3 Budget 34

4 4 1.0 Executive Summary The aims of the study were to: Determine the effectiveness of vasectomised bulls as an aid to heat detection in UK dairy herds. Record the impact on reproductive performance of vasectomised bulls. Record the behavioural effects of the presence of a bull. Assess the cost-benefits of the use of vasectomised bulls. Highlight any practical difficulties of the use of vasectomised bulls. This was to allow practical guidance to be given to farmers on the suitability, effect, and management of a vasectomised bull. The study was run on five commercial farms in Somerset, and the dairy unit at Seale Hayne College in Devon. A variety of bull breeds were use. Following vasectomy, the bulls were used once they reached a minimum weight of 350kg. The study was conducted on the basis of alternate 28 day periods, with and without the bull, over a 24 week period. Bulls were fitted with a chin ball harness, so that bulling cows were marked, if oestrus activity was not observed. All fertility parameters were recorded and input into the DAISY recording system for later analysis. Brief periods of observation were carried out to observe oestrus behaviour, with the bull present and absent. Milk progesterone samples were taken from oestrus cows to confirm the accuracy of heat detection. The study found the effect of the bull on reproductive performance was: A 10% improvement in 28 day submission rates. This result was found to be highly significant. A 5.4 day improvement in calving-1 st service. This result was not statistically significant. No effect on conception rates. The improvement in submission rates was observed on five out of six farms, and statistically significant on two individual farms.

5 5 28 day Submission rates Bull period 40% Control period Control period 85% Bull period 80% 75% 70% 65% 60% 55% 50% 45% HO CR MP MW HW SH Mean Farms Observation data found that the presence of the bull increased the intensity of oestrus activity, with mounting activity increased. The levels were not statistically significant. There was no effect on the duration of oestrus activity. Milk progesterone data found no deterioration in the accuracy of heat detection with a bull present, and this was confirmed by comparable conception rates in bull and control periods. Cost-benefit analysis of this data indicates a financial benefit of up to 0.65 pence per litre from the use of a vasectomised bull. This information is derived, and comes from a reduction in calving interval of 7.4 days, and a predicted reduction in culls for infertility of 3%. The return on investment is of the order of 500%. All farmers found the bull eased the identification of cows in oestrus, commenting that the presence of the bull saved time spent on heat detection, and helped in determining the timing of service. The use of an Angus-cross appeared to be most beneficial as these animals had a better libido. Practical difficulties were few, but there was a need to acclimatise the bull to running with larger cows in order to avoid injury.

6 6 Report Body 2.0 Background Good reproductive efficiency is essential to profitable dairy farming and is measured by calving index and numbers culled for infertility, with breeding costs a further concern. The major factors influencing reproductive efficiency are heat detection and conception rates. A number of factors have combined to reduce the reproductive efficiency in UK dairy herds. Conception rates are widely recognised as falling, and the fall is linked to the increased yield of Holstein cows. Farmers, however, have a greater influence over heat detection, yet heat detection rates have remained at 55% for 20 years, with an 80% rate attainable. Improved heat detection would have an immediate effect on reproductive efficiency. Significant factors may be high yielding cows show reduced oestrus activity and have more irregular oestrous cycles; increased cow numbers in dairy herds has reduced the time available for heat detection, and time per cow has been reduced. Stockman knowledge of individual cows is likely to be less, and perhaps cow identification is more difficult. There are many aids to heat detection. These include the use of heat mount detectors, tail paint, pedometers, closed circuit television, vaginal probes to assess electrical resistance, and milk progesterone assays. While they are all effective, their uptake is not universal due to problems associated with their use. Use of vasectomised bulls has been carried out in the past but is not currently in use in the UK. It may be that the use of vasectomised bulls fits the current UK dairy industry need for improved heat detection. The use of a bull is often found to increase oestrus activity on farm, but the farmer loses control over timing of service and bull selection. The use of a vasectomised bull offers the advantages of improved heat detection while maintaining control over breeding. The use of a bull would also reduce reliance on vet intervention with hormones. This is likely to be of particular significance for organic herds, unable to use oestrus synchronisation techniques.

7 7 3.0 Objectives To determine the effectiveness of vasectomised bulls as an aid to heat detection in UK dairy herds. An assessment of both the efficacy and accuracy of heat detection will be made. To record the impact on reproductive efficiency of vasectomised bulls. Records of submission rates, conception rates, calving-1 st service and calving-conception will be analysed. To record the cow behavioural effects of the presence of a vasectomised bull. To assess the cost-benefits of the use of vasectomised bulls. To highlight any practical difficulties of the use of vasectomised bulls. 4.0 Study design 4.1 Study Plan The study was run on six farms on alternate trial and control periods of 28 days. During the trial periods the bull was run with the milking herd, or breeding group, as appropriate. The bull was out of sight of the milking herd during the control periods. The initial aim was to continue the study for a 24 week period on each study farm. Farm Start period Study duration HO Bull CR Bull HW Control 24 MP Control weeks MW Control SH Bull Time was given initially in the training of farmers in the use of a bull and chin ball marker, in the supervision of the bulls health and condition, and in data recording and monitoring. After an initial period the farm was visited every 2 weeks as part of normal routine fertility visits, allowing record gathering and the evaluation of any problems encountered. Heat type was recorded by the farmer and categorised as bull activity/marking, cow activity, both or other.

8 8 B C O Cow served mainly due to marking by bull, or bull activity Cow served mainly due to cow activity Cow served for other reason, eg fixed time, bulling string Milk samples for progesterone measurement were taken from a proportion of heats to assess the accuracy of heat detection by each method of heat detection. A behaviour study of bull activity was built into the study, involving veterinary and agricultural students. Training was given in heat detection, and observations were carried out three times a day over a two week period. A standard recording sheet was used (Appendix 2) to record all cow oestrus behaviour and any bull involvement. The data was used to compare cow behaviour during the control and bull periods. 4.2 Study personnel The study was carried out by Paddy Gordon on 5 farms served by Shepton Veterinary Group, Shepton Mallet, Somerset. Additional assistance on one farm was provided by a colleague, Peter Morley. Jean Margerison, Senior Lecturer at Seale Hayne College, supervised the study at the Universty of Plymouth dairy unit. Three students were involved in the behavioural studies. They were Rebecca Mann and Susanna Payne, Final Year vet students from the Royal Vet College; and Robert Collins, from Seale Hayne College, University of Plymouth. Behavioural observations on one farm were carried out by Paddy Gordon, and a vet, Matt Watkinson. Shepton Veterinary Group is a mixed veterinary practice of 9 vets in Shepton Mallet, Somerset. Six farm vets service dairy cows in the immediate area. The practice has a longstanding reputation for excellence in dairy health and fertility. Roger Eddy developed herd fertility work and the DAISY system with Dick Esslemont, University of Reading. Peter Edmondson is an RCVS Specialist with an international reputation for work on milk quality and mastitis. The practice regularly carries out work to Good Clinical Practice standards for pharmaceutical companies, and has carried out work for registration purposes. The practice has entered a collaboration with the Royal Veterinary College to co-operate in clinical research and the post-graduate education of Farm Animal Senior Training Scholars. Paddy Gordon has been involved almost wholly in farm animal veterinary work since graduating from Cambridge in In July 2001 he became a partner at Shepton Veterinary Group. He has worked in practice for the majority of his career but also spent 3 years at the Royal Veterinary College as the Farm Animal Resident. During this time he gained the RCVS Certificate in Cattle Health & Production as well as carrying out duties in the practice, teaching and some research. His interest has been predominantly in the

9 9 reproduction and health of dairy cattle, working with farmers via routine fertility visits and advising on health control. He has carried out research into oestrous synchronisation in cattle, and has made presentations, including at the World Buiatrics Congress 1996, and published articles on this subject, surgery, and clinical cases. His interests and experience covers reproduction and embryo transfer, dairy cow nutrition, mastitis control, and surgery. 4.3 Study farms 6 farms were used to conduct the study. They are five commercial dairy farms, and the dairy unit attached to Seale Hayne College. Farm Cow numbers Farm type Calving pattern Start date HO litre, zero grazed All year round March 2002 CR litre, TMR fed All year round, Autumn 2002 block calving HW litre, organic Autumn Winter 2002 MP litre All year round Autumn 2002 MW litre, TMR fed Summer/Autumn Autumn 2002 SH litre, Jersey/Friesian Summer/Autumn Autumn 2002 The following fertility history was available for the study farms. Results are based on the year preceding the trial, and information was limited to DAISY or NMR records where available. Farm Pregnancy rate (%) Calving interval (days) Culling rate for infertility (%) HO CR HW MP MW SH Farmer heat detection routines are outlined in the table below.

10 10 Farm Farm size Number of staff involved in heat detection Heat detection routines (Observation during routine work plus) Other aids HO None Kamars CR Two evening checks None HW Evening check Tail paint MP Evening check None MW Evening check None SH 130 2/3 4 periods 4.4 Bull selection The aim was to choose Angus or Hereford cross calves on the basis of their low value, temperament when compared to dairy breeds, and smaller stature which would allow them to remain in winter cubicle housing. The bulls would be vasectomised around puberty at 9 months of age. They would be put to use once of reasonable stature, typically 15 months old. The bulls were fitted with a chin ball marker topped up with paint. This resulted in the bull marking cows and worked as an aid to heat detection, where bulling behaviour was not observed. The well required topping up every 7-14 days. Where this study may differ from previous studies is in the use of young immature bulls for vasectomy, rather than unwanted stock bulls. This should: mean low value animal is used, increasing farmer willingness to undertake procedure lower perceived financial risk, and readily available subject material make surgical procedure easier reduced time, cost and materials - thereby reducing cost to the farmer and probably reducing any vet concerns Allow a study on sexually inexperienced animals. These animals should have good libido, with sexual performance irrelevant. Concerns about venereal disease or imported disease become less relevant as the animal will be virgin, and preferably home-bred 4.5 Data recording Cow identity and date of oestrus/insemination was recorded and input into the DAISY computer recording system. Other information relevant to the study was also recorded calving date, PD result. 4.6 Record analysis The records were analysed for each period and each farm. The results were then aggregated to give a comparison of overall differences in performance between the bull and control periods.

11 Fertility Data analysis Submission rates For ease of analysis these were assessed on a 28 days basis. All cows more than 43 days calved at the start of the 28 day period were considered to be eligible for service. This ensured that all animals eligible for service (more than 50 days calved) would complete an oestrus cycle within the window. Cows less than 43 days calved, pregnant, or marked as barren were not included. The submission rate is the proportion of cows served, from the group identified as eligible for service. Mean serves This is the number of serves within the bull or control periods, divided by the number of 28day periods. This was simply a measure of whether there was a significant difference in the amount of oestrus activity between bull and control periods. Conception rates For each 28 day period the number of pregnancies was divided by the number of serves to give a conception rate. Calving-1 st service For each 28 day period the days to first service was recorded for all cows receiving a first service. The mean was then calculated. Calving-conception The days from calving-conception was recorded for all cows conceiving in any 28 day period. The mean was then calculated for each farm. A weighted mean was then calculated to give the overall mean. Bull activity The farmers record of the reasons for service within any bull period was used to indicate the proportion of heats that involved the bull on each farm. 4.8 Activity data analysis For each bull and control period there was a short 5-7 day period of intense observation. Cow and bull oestrus activity was recorded and analysed in the following way for each period. Data was calculated for each farm and overall, for both control and bull periods.

12 12 Oestrus activity Primary/secondary behaviour The number of cows in oestrus was recorded and the proportion of cows showing primary signs calculated. Oestrus Duration Cows were observed three times daily and cows scored according to the frequency of oestrus observations. A cow observed on a single occasion scored 1, a cow showing oestrus activity on 2 occasions scored 2, etc. Oestrus intensity The number of mounts was recorded (cows mounted and oestrus cows mounting), and the total number of cows recorded in oestrus. The total mounts was divided by the number of cows to give the mean mounts per cow. The total number of mounts was recorded and divided by the number of cows showing primary oestrus behaviour. This gave a figure of the mean mounts per primary oestrus cow. The number of cows in standing heat was recorded, and comparison with the total number of cows in oestrus gives a value for proportion of cows showing standing heat. The number of mounts in each standing heat was recorded. Division by the number of cows in standing heat gave a figure for the mean mounts per standing heat. 4.9 Milk Progesterone These were assessed in the following ways for each farm and aggregated to give overall figures. The proportion of samples found to be negative (<5ng/ml) was recorded. This is an indicator of the accuracy of oestrus detection on each farm. The proportion of samples found to be negative for the bull and control periods. This gave an indication of whether oestrus detection accuracy was altered by the presence of the bull. The proportion of samples with low progesterone for each heat type was recorded. This gave an indication of whether heat type had an influence on oestrus detection accuracy Farmer Questionnaire A follow-up questionnaire was used (Appendix 2) to establish farmer opinion on the effectiveness of the bull, any health or safety problems, and management costs.

13 Results Study design Deviations from the study design are given below. The results were analysed for complete 28 day periods when the study design was adhered to. This resulted in some reduction in the number of periods, and alteration to study design, as shown in the table below. Farm Start period Study duration Start month HO Bull 6 periods March 2002 CR Bull 5 periods October 2002 HW Control 3 periods January 2003 MP Bull 5 periods October 2002 MW Bull 5 periods September 2002 SH Bull 5 periods November 2002 The reasons for the changes were the use of a stock bull on 3 farms (CR, MP, MW). This use was not anticipated on setting up the study. On farm HW the study was shortened due to bull injury, and a limited breeding season. Bull selection Following Foot and Mouth Disease in 2001, there was a strong demand for store cattle in This resulted in some problems finding suitable bulls for use. The bull breed and their source is outlined in the table below. Farm Bull breed Source HO Continental-cross Homebred CR Hereford Purchased HW Angus x Friesian Purchased MP Angus x Friesian Homebred MW Angus x Friesian Homebred SH Continental-cross Purchased

14 Reproductive performance These results are tabulated in Appendix 1, Table Submission rates 28 day submission rates were improved from 64% to 74% by the presence of the bull. Chisquared analysis showed this result to be highly significant. On 5 farms there was an increase in submission rates when the bull was used. This increase was up to 15%. The farm with the lowest increase reported that the bull had a low libido. On one farm (HW) there was no improvement, but this may reflect the fact that only a single bull period was recorded, and that submission rates for the start of the breeding season (a control period) were exceptionally high. There was a variation in submission rates between farms (44-57% on farm MP) and (70-84% on farm MW). This variation reflects oestrus detection on individual farms. Mean serves This was recorded to indicate the amount of oestrus activity during each 28 day period. It shows a mean of 48.0 serves with the bull, and 42.0 serves in control periods. The bull figure may be higher due to higher submission rates. 5.2 Calving-1 st service The presence of the bull resulted in a reduction of calving-1 st service from 87.6 to 74.3 from a total of 533 first serves. The result is magnified by the timing of bull and control periods for seasonal calving herds. If the all year round calving herds (HO, CR, MP) only, are considered, where study design will have no influence on calving-1 st service, there is a reduction of 5.4 days (from 78.1 to 72.7 days). 5.3 Conception rates The conception rates between the two periods were comparable, at 39 and 40%. These conception rates reflect current UK figures. The conception rates may be depressed because they reflect all serves, and not only those for which the outcome is known. Calving-Conception The calving-conception data indicates that there was an increase in calving-conception of 7.2 days (108.9 vs days) when the bull was present. The presence of the bull should not influence the days from calving-conception, and the results are purely a function of the cows conceiving during each period.

15 Bull activity Farmer recording of heat type was available for 620 heats. Overall the bull was recorded as involved in 52.9% of heats. This indicates the bull is an aid to heat detection, and cannot be the sole basis for selecting cows in oestrus. The variation was from % of heats. Herds with low bull activity included farms HO, where the bull was injured and changed; and CR where a low libido was reported for the Hereford bull. The highest activity was reported on farms with bulls with good libido. The table below gives an indication of the number of cows in the milking herd, and likely to come into oestrus, based on 75% of unserved cows, and 50% of served cows). Farm Study Beginning Or End Cows in milk HO Beginning End CR Beginning End HW Beginning End MP Beginning End MW Beginning End SH Beginning End Cows likely to come into oestrus 5.5 Bull behaviour These results are tabulated in Appendix 1, Table 2. Primary and secondary signs of oestrus 189 cows in oestrus were observed, and 83% of oestrus cows showed primary signs (mounting, standing to be mounted, Kamar colour change) when the bull was present. This compared to 78% during the control periods. Mounting activity The mean number of mounts per cow in oestrus during the bull periods was 4.8, compared to 3.8 in the control periods. This result was not found to be statistically significant on analysis using the Student s t-test. The mean number of mounts per cow showing primary signs was also higher at 5.9, compared to 4.9 in the control periods.

16 16 The proportion of cows observed showing standing heat was higher at 65%, compared to 59.5% in the control periods. The number of mounts per standing heat was also higher at 4.7, compared to 3.6 in the control periods. The only farm where the oestrus activity was repeatedly less intense during the bull period was farm CR, where the libido was low. The above observations would indicate that the presence of the bull increased the intensity of oestrus activity. Unfortunately the number of observations are not of sufficient size to make the results statistically significant. Oestrus duration The mean number of observations of oestrus activity was 1.7 in the bull periods and 1.9 in the control periods. This indicates that the presence of the bull did not increase the duration of oestrus activity. With observations approximately every 8 hours, this would indicate that mean duration of all observed oestrus activity was hours. 5.6 Progesterone data These results are tabulated in Appendix 2, Table 3. The presence of a low progesterone level confirms that cows submitted for service are in oestrus. 165 samples were collected, and 79% of cows had a low progesterone level. 79% of milk samples taken during the bull period had a low progesterone level compared with 86% in the control period. 80% of samples taken from heats recorded as bull activity had a low progesterone level, compared with 85% of control samples. There was a low rate of oestrus detection accuracy for heat type other at 64%. There was a low rate of heat detection accuracy for farm HW at 54%. 6.0 Bull health On farm HO there were problems with the bull damaging his hip and upper leg, resulting in a chronic lameness. The bull was changed midway through the study. On farm HW there was a temporary lameness due to hip injury, which recovered after 2 weeks rest. On two farms (HO, MP) the bulls became bruised around the tailhead. It is likely that all these injuries were the result of small stature bulls falling off cows onto concrete when mounting. On farm MW there was a temporary mild lameness due to digital dermatitis. The chin ball marker caused no problems to the head of the bull, or to any cows.

17 Cost-benefit analysis Running Costs Farm Initial Finishing Value in /kg weight weight HO 350kg 400kg 1 CR 280kg 400kg 1 HW 330kg 375kg 0.80 MP 350kg 500kg 0.80 MW 300kg 500kg 1 SH 300kg 400kg 0.90 Average 322kg 435kg 0.92 The initial and final value of the bull is given in the table above. On this basis the average cost or value of the bulls at the start of the trial was 296, and at the end was 400. Farm Daily feed cost HO 1.20 CR 0.75 HW 1 MP 1.50 MW 1 SH 1.15 Average 1.10 The given feed costs are tabulated. The total running costs of running a vasectomised bull over the trial period are set out in the table below. Item Unit cost Total cost Initial value/purchase 0.92 per kg 296 Vasectomy costs 130 Chinball marker 64 Marker dye 23 per pot 46 Feed costs for 183 days 1.10 per day 201 Final bull value 0.92 per kg ( 400) Anticipated treatments 25 Total cost 362

18 18 The above is calculated for the period of the trial. If the bull was maintained in the herd for a period of 12 months the costs would be as outlined in the table below. Item Unit cost Total cost Initial value/purchase 0.92 per kg 296 Vasectomy costs 130 Chinball marker 64 Marker dye 23 per pot 92 Feed costs for 365 days 1.10 per day 402 Final bull value 0.92 per kg ( 500) Anticipated treatments 50 Total cost 534 The above gives the total cost of keeping a bull for a year, assuming he is sold at the end of his useful life. No allowance has been made for any claims for payment on male animals held. Reproductive efficiency The major indices in reproductive efficiency are listed below. Calving-1 st service Submission rates Conception rates Culls for infertility The presence of a vasectomised bull has been shown in this study to improve the calving-1 st service by 5.4 days, and improve submission rates by 10%. There was no effect on conception rates. The farmers indicated that they would continue to serve a cow until she got in calf, or yield became uneconomic. A figure of 10 oestrus cycles from the end of the voluntary weight period (50 days) has been assumed.

19 19 The effect on overall reproductive performance can be calculated using the method calculated by Esslemont (1993). This is outlined in the table below. Parameter Calving-1 st service UK average value Vasectomised bull figure Vasectomised bull effect Minus 5.4 days Submission rates 55% 65% Plus 10% Conception rates 38% 38% None Reproductive efficiency Plus 3.8 Predicted effect on reproductive performance Calving interval conception 110 days 108 days Minus 2 days Culling rate for infertility 10% 7% Minus 3% The effect of the bull is a 7.4 day saving in calving-conception interval, and a 3% saving in cows culled for infertility, based on a 260 day limit for serving. Applying these figures to a typical UK herd of 180 cows, giving 7000 litres of milk receiving 18.2 pence per litre, gives the financial saving outlined in the table below. Parameter Calving interval Culls for infertility Reduction Cost per unit Vasectomised bull saving 7.4 days % Total 5934 Total in pence per litre 0.65ppl The above assumes the bull works constantly for a 12 month period. It is more realistic to assume that the bull will work intermittently. Assuming the bull works for 6 months of the year then a financial benefit of almost 3000 can be anticipated. This should be weighed up against annual running costs of 534. This gives a net return of 2450 or a 500% return on investment. A further alternative is to look at these figures as the impact on a pence per litre basis. This would give an increase on milk price of 0.65 pence per litre on an annual basis, or 0.32ppl if the bull only worked for 6 months.

20 Farmer Questionnaire All farms reported that the presence of the bull made it a lot easier to detect bulling cows. Four farms reported that the presence of the bull saved a little time, while two indicated the bull saved a lot of time. Four farms indicated that they felt the bull increased pregnancy rates, although this was not shown in the results. All farms felt the chin ball marker was useful in helping to mark bulling cows, but one farm felt it was a fiddle to top up the marker. The bulls all became used to having the chin ball marker removed and refitted. All farms indicated they would continue to use the bull, until he became too big to manage, and would recommend the use of a vasectomised bull to other farmers. There were no health and safety concerns associated with the bulls, but relief staff were anxious about bull handling on one farm.

21 Farmer Recommendations The use of a vasectomised bull should be considered where the aim is to improve heat detection rates. Other factors affecting fertility, such as staff skills, staff routines, cow health and nutrition, and housing should also be considered. Breed selection Aberdeen Angus x Friesian is advised due to animals being usually hardy, have a relatively small frame and a good libido. Vasectomy timing should be discussed with your vet, but could be carried out at any time from 6 months of age. Prior to vasectomy, the bull should be kept away from non-pregnant females, and for at least 6 weeks after the vasectomy, if he has reached puberty. Bull management Start use when bull is of sufficient stature, typically two thirds of cow weight. Run the bull with pregnant cows for a couple of weeks prior to use to allow the bull to get used to being on concrete, and feeding among the larger cows. Initially the bull will attempt to mount many cows, so do not fit chin ball marker and ignore activity for the first 48 hours. The chin ball marker needs to be topped up every 1-2 weeks. Care should be taken in interpretation of markings on a cow, as they may only reflect bull-cow interaction. When a cow is in oestrus the marks are striped along the back of a cow, and are considerable. The bull was run with up to 100 empty cows during trial work. The following guidelines are suggested, but will need to be tailored to the farm and bull, and veterinary advice is advised. Herd size Calving pattern Bull use Up to 200 cows All year round Single bull, intermittent use. 4 weeks on, 2 weeks rest Up to 200 cows Block calving Single bull, use from 6 weeks into breeding season More than 200 cows All year round Two bulls, swap over every 2 weeks More than 200 cows Block calving Single bull, use from 6 weeks into breeding season

22 22 Bull health The bull rapidly becomes accustomed to having the marker changed. Check for sores around the harness. The bull will get fat if overfed, and lose his sex drive if he is permanently running with a large number of non-pregnant cows. Use of the bull needs to be intermittent, with removal to the dry cow group for rest periods. The length of use and rest periods will depend on herd size, number of empty cows and feeding. The main risk of injury to the bull comes from falling off cows onto concrete. This is minimised by acclimatising the bull to concrete first of all. If the bull becomes injured or lame he should be removed and rested, as libido will be lost if the bull loses confidence. Cow health The use of a bull carries a risk of venereal disease. Venereal disease will result in abortions, an increase in whites and irregular returns. Use of a bull will not be appropriate in herds with a history of venereal disease, or Infectious Pustular Vaginitis. It is unlikely the bull will be the source of disease, but he may contract infection if you use hire bulls, or purchase infected cows. The risk of venereal disease should be no greater than the use of a sweeper bull at the end of the breeding season. Health and Safety Farmers should be aware of Health and Safety Guidance notes on the Safe Custody and Handling of bulls on farms. A bull is an uncastrated male over 10 months of age. These notes indicate staff should be trained in safe work methods a second person should be present if it is necessary to enter a building or yard where a bull is running loose. Observation of bulling activity is usually possible from outside the yard on most farms. When at grazing, persons moving or inspecting the herd should be accompanied or use a farm vehicle as a mobile sanctuary. The breed, stature and regular handling meant concerns were minimal during the study, however the unpredictable nature of bulls means Safety should be given serious consideration.

23 Discussion Study design The study was designed to assess the impact of a vasectomised bull on the reproductive performance of commercial UK dairy farms. As a consequence there were always likely to be aspects of the study not controlled in the same way as a study within a research centre. The study was reduced in duration as a consequence of bull injury or the use of a stock bull, within the initially set control periods. The impact of this was to reduce the volume of data available, and therefore the chance of significant results. It is not regarded as likely to create any bias in the results. Heat detection routines on five farms were limited to evening checks only, with heat observation at other times due to detection while other tasks were carried out. This is a reflection of the lack of time available on farm, and the low commitment given to heat detection. It is probably a pattern of behaviour that would be reflected on most other UK dairy farms. The 28 day study period was set as this fitted the cycle of routine visits on each farm. 28 day submission rates were used for simplicity of assessment. Cows eligible for service were all cows not pregnant or barren, and calved sufficient time as to be available for service, provided they could complete one oestrus cycle (21 days) within the 28 day period. The values are likely to be the order of 28/21higher than a 21 day submission rate. If the average UK submission rate is 55%, then the equivalent 28 day submission rate is 73%. The results then indicate that most study farms were slightly below average in submission rates, and the presence of the bull raised rates to above average levels on 4 herds. There was no effect on one herd (HW), and for one herd (MP) submission rates, while improved, were still below average. The most important aspect of the submission rate data is not the method of calculation but the difference between the two periods, as provided the same method is used each time the increase reflects accurately the effect of the bull Reproductive performance The improvement in submission rates was statistically highly significant. It is significant also in its effect on reproductive performance and anticipated financial return. The effect was achieved using a low-cost immature bull, at a high ratio of cow:bull of over 100:1. A 10% improvement in submission rates would alleviate the decline seen in conception rates over the past 25 years. Farmers involved in the study expressed confidence that the presence of the bull aided heat detection, improved confidence in the timing of insemination, and resulted in less time spent on heat detection.

24 24 When compared to other heat detection aids, the use of a vasectomised bull does not require a change in working practices, and farm routines. The investment required is also relatively low. This may mean the use of a bull is more readily taken up by farmers, when compared to other heat detection aids. For example, use of Kamars involves pulling out cows to apply heat detectors; or the use of activity meters involves considerable investment and time spent at a computer. The small difference (14%) in mean serves indicates that it is likely there were comparable numbers of cows in oestrus during bull and control periods, and therefore the increase in submission rates with the bull is likely to be a reflection of the presence of the bull, rather than increased cow activity due to larger numbers of cows being in oestrus. Calving-1 st service was reduced by the presence of the bull. This is a direct reflection of improved submission rates. The use of seasonally calving herds creates some bias, as the timing of bull or control periods would influence the likely values. Once these figures are removed it can be seen that there is still a bull effect. The magnitude of reduction and cow numbers meant this was not at a significant level. Conception rates were not affected by the bull s presence. The effect of the bull could have been positive, due to improved timing of insemination, or negative if the bull resulted in false heats being identified. Calving-conception for each period is a reflection of the cows holding during the period, and the bull has no direct influence on this. As a result the increase seen in calving-conception during the bull periods is not relevant to the study Behaviour Bull activity, as an indicator of oestrus, was recorded by the farmer. The proportion of heats involving the bull is a reflection of the libido of the bull, so on farm HO the bull had a low libido due to injury, and the Hereford bull on farm CR showed a low libido. The value for farm MP may be low due to a poor level of recording on this farm. Observations and results indicate that the Aberdeen Angus cross bull had the greatest libido and was the most appropriate breed for use. The project was successful in the use of small stature bulls indicating bull enthusiasm was most important. The bull s libido was sustained in spite of an inability to always achieve intromission. The use of small stature bulls minimised the risk of injury to high value milking cows. The behavioural data can be regarded as unsound for a number of different reasons. There were different cows in oestrus, and different numbers of cows in each observation period. The observations were not continuous and therefore do not reflect all cow oestrus activity. The observers were inexperienced, and differed between farms. In spite of all this the data

25 25 were all collected in the same way and analysed by the author aimed at trying to establish if there was a reason for the improved submission rates, and reported improved ease of heat detection by the farmers. The data appears to show that there is an increased intensity of oestrus when a bull is present. This manifests itself as increased mounting activity, and increased numbers of mounts, but not an increase in duration of oestrus. This increase is termed biostimulation. The bull may also be acting as a focus for heat detection, both for cow activity, and for farmer observation, thus making heat detection simpler and more rapid Milk Progesterone data The progesterone assays were carried out to assess the accuracy of heat detection on the farm, and when the bull was present. The results indicate that the overall accuracy of heat detection was only 79%. This is a low figure, and is depressed by the results for farm HW. These results for HW are likely to be erroneous, as they do not reflect the conception rates achieved on the farm. The laboratory assays for this particular farm were not carried out by the experienced technician who processed the other samples. This makes the results open to doubt. There was little variation between bull and control periods for progesterone results, and this repeats the findings for conception rates, that the presence of the bull had no effect on heat detection accuracy. 9.6 Concerns The concern would be whether this improvement would be sustained in the long term. Bull use was intermittent and for a 3 month period only in this study. Running a bull at a high cow:bull ratio is likely to result in loss of libido due to overwork. Maintenance on a milking cow ration is likely to result in considerable weight gain. These two factors mean that the use of a single vasectomised bull should be intermittent, with rest periods in between periods of use. Experience will determine the optimum length of time. The alternative is to use a pair of bulls and swap them over. Farm HO has successfully taken this approach since the end of the trial. The bulls are likely to have a finite life due to weight gain, and potentially they may become more aggressive. The use of mature bulls is unlikely to be satisfactory under housed conditions due to the risk of injury to cows, and in cubicle systems the lack of an appropriate lying area. The farmers in this study indicated that they would continue with the use of the bull until the bull became too heavy or ineffective.

26 Financial analysis The cost benefit analysis shows a positive effect of bull use, even with the conservative figures used. The cost per day of an extended lactation is a minimum of 10 litres per day (Esslemont 1993). Using a current milk price of 18 pence per litre gives a cost of 1.80 per cow per day. This is considerably lower than other frequently quoted figures of 3 per day. The cost of a culled cow is given as 650, which is based upon a cull price of 250 and a purchase price of 850. These figures are conservative. The alternative way of expressing the financial gain is a 0.65 pence per litre improvement in milk price, or 3.6% gain, based on a milk price of 18 pence per litre. This financial return is achieved for a modest outlay, and with minimal change in working routines required. Given quoted figures of 2 pence per litre for financial losses due to reproductive wastage, the use of a vasectomised bull would appear to reduce these losses buy a third. The above cost benefit analysis takes no account of further financial savings due to reduced time spent on heat detection, or reduced vets bills due to a reduction in cows presented for oestrus not observed. 9.8 Farmer response The farmer response was unanimous as they all found the bull a useful aid to heat detection. The presence of the bull improved submission rates by up to 15%. The reproductive performance on each farm are typical of those seen in UK dairy herds. Herds were selected for the trial on the basis that they were likely to undertake and fulfil the trial, and there was no attempt made to select herds most likely to benefit from improved heat detection. However it is interesting to note that only one herd had an optimal heat detection routine of checking cows four times daily. It is likely that this reflects the approach used across many UK dairy herds, due to a perceived lack of available time Conclusion In conclusion, the use of a vasectomised bull has been shown to have a markedly positive effect on reproductive performance due to improvement in submission rates. Adoption of this practice by UK dairy farmers involves minimal outlay, or change in daily routines. It is therefore a practical proposition and should be given consideration where there is a need to improve heat detection and submission rates. The demonstrated benefits far outweigh the potential risks.

27 27 References Esslemont RJ (1993) Vet Record 133, Relationship between herd calving-to conception interval and culling rate for failure to conceive. Acknowledgments I would like to acknowledge, and thank the following for their input. The Milk Development Council for funding the study. The farmers involved for their time and input, and for being willing to undertake trial work when there are so many other pressures. Clive Phillips and Jean Margerison for assistance in constructing the study, and results analysis. Robert Collins, Suzanna Payne, Rebecca Mann and Matt Watkinson for time spent on cow observations.

28 28 Appendix 1 Table 1 Table of fertility results Herd HO CR MP MW HW SH Mean Submission rates Bull period Eligible cows Eligible Served cows Submission rate 81% 73% 57% 84% 71% 73% 74% Control period Eligible cows Eligible Served cows Submission rate 66% 66% 44% 70% 75% 62% 64% Chi-squared analysis Yates P value Mean serves Bull period No. of periods Mean serves 48.0 Control period No. of periods Mean serves 42.0 Conception rates Bull period Serves Pregnancies Overall rate 37% 40% 38% 37% 48% 38% 39% Control period Serves Pregnancies Overall rate 37% 48% 28% 35% 52% 36% 40% Difference not significant

29 29 Table 1 (continued) Herd HO CR MP MW HW SH Mean Calving-1st service Only all Bull period year round Cows herds Mean Weighted 72.7 SD Control period Cows Mean Weighted 78.1 SD Difference not significant Calving-Conception Bull Period Cows Mean Weighted SD Control period Cows Mean Weighted SD Bull activity Heats recorded Bull involvement Percentage bull 33.2% 56.8% 34.0% 72.4% 91.1% 55% 53.3% Cow only Other NR

30 30 Table 2 Behaviour data Farm HO CR MP MW HW SH Total Proportion showing primary oestrus activity Bull Cows in oestrus Primary Proportion 95% 75% 78% 67% 89% 75% 82% Control Cows in oestrus Primary Proportion 92% 100% 46% 100% 58% 71% 77% Number of oestrus observations Bull Duration total Duration mean Control Duration total Duration mean Mounts per cow in oestrus Bull Total mounts Mounts per cow All oestrus cows Control Total mounts Mounts per cow All oestrus cows P value 0.08 Mounts per cow showing primary behaviour Bull Total mounts Mounts per cow Mounting cows Control Total mounts Mounts per cow Mounting cows Cows showing standing heats Bull Cows standing ht Proportion standing 75.0% 50.0% 69.6% 66.7% 57.9% 62.5% 64.6% Standing heats obsvd Mounts per standing heat Control Cows standing Proportion standing 64.0% 100.0% 46.2% 42.9% 36.8% 57.1% 59.1% Standing heats obsvd Mounts per standing heat

31 31 Table 3 Progesterone data Farm HO MW CR MP HW SH Total Proportion samples low progesterone No samples Negative Positive % neg % Separated by bull or control period Control period Negative Positive % neg % Bull period Negative Positive % neg % Separated by recorded heat type Heat type Bull Negative Positive % neg % Cow Negative Positive % neg % Other Negative Positive % neg %

32 Bull involvement Standing to be mounted Mounting Increased activity Vulva sniffing licking Chin resting rubbing Tail raising switching Frequency of urination Excessive bellowing 32 Appendix 2 Recording sheets and Farmer questionnaire FARM DATE START TIME TIME (2 mins) Cow Comment

33 33 Farmer survey Cost-benefit study on the use of vasectomised bulls as an aid to heat detection in UK dairy herds Farm breeding policy How many days after calving do you start serving? What is your usual heat detection routine? Who else carries out heat detection on the farm? How many days after calving do you stop serving? How many times will you serve a cow before culling? Heat detection Do you think vasectomised bull Made it easier to detect bulling cows A lot A little No difference Worse Saved time on heat detection A lot A little No difference Worse Improved pregnancy rates A lot A little No difference Worse Any other comments on fertility Chin ball marker Was the chin ball marker useful in marking bulling cows? A lot A little No difference Worse Did the chin ball marker cause any problems? Were there any problems with topping up the marker or handling the bull?

34 34 Long term Will you keep the bull as an aid to heat detection? If so, for how long? Cull before or after 30 months old. Would you consider using another vasectomised bull? Would you recommend using a vasectomised bull to other farmers? Running costs What was the initial weight of the bull? What was the initial value of the bull? What is the final weight of the bull? What is the final value of the bull? What was the daily feed cost? Were there any other costs in keeping the bull? Did you have any Health and safety concerns about running a bull? Any other comments

35 35 Appendix 3 Budget and Expenditure Item Farm Farm Farm Farm Farm Farm Other Cost per Total HO CR MP MW HW SH unit Units/time 1 Initial vasectomy Visit Total cost Surgery Medicines Rompun PenStrep Lignocaine Devomycin Initial training Visits Bull, recording,health,etc Followup Visits Data collection, bull health DAISY recording Data analysis Seale Hayne budget Chin-ball markers Purchase harnesses Purchase dye Student observation Accomodation Travel Expenses Supervise students Cow observations Milk progesterone Assay purchase Technician fees 0 9 Review data, interim reports Report writing Report writing TOTAL Total Predicted 15,364