CASE NOTES
INVESTIGATING A REPRODUCTIVE PROBLEM IN A BEEF HERD—WHEN DO YOU STOP?
Paul Freeman, NWW DPI
Posted Flock & Herd April 2013
Introduction
The investigation of reproductive problems in beef cattle herds can be problematic. Rarely is suboptimal performance due to a single cause and the challenge in investigating problems is to be able to define the stages of the reproductive cycle when suboptimal performance is occurring.
That requires some knowledge or benchmark about performance parameters because you need to have some opinion or judgment about optimal performance to be able to define suboptimal performance. The other issue when undertaking these investigations is that often you are constrained by inadequate records, herd observations or management practices. For instance conception records may not be available, joining practices may be all year round and herd managers may only operate part time and live off farm.
Busy veterinarians often take samples and find evidence for the presence or absence of etiological agents and that may be the limit of their involvement in herd fertility investigations. They may diagnose an infectious disease in the herd and give some preventive or therapeutic advice and leave it at that. In some herds that may be all that is necessary but rarely addresses the issue of suboptimal reproductive performance which in itself is one of the key drivers for profitability in beef herds.
Taking a broader role will take longer. It may require more property visits and time setting up systems to gain the information need for accurate decision making. However veterinarians are the best trained people to give advice to producers in regards to fertility. It is true that the benefits that accrue as result of improvements to fertility indices benefit the individuals and the use of private veterinarians to do the work may be the most appropriate option. But some private veterinarians are often reluctant to do this type of work for various reasons. In many areas they do limited farm animal work and the fees they can charge of often inadequate for the time involved. Some lack the broader skills to understand the interplay between disease, production and management. The process and outcomes of detailed fertility investigations and any ongoing monitoring do generate substantial advisory messages and the broader industry benefits when those messages are disseminated. District Veterinarians with their broad skill set are the obvious choice for disseminating fertility advisory messages and in some areas at least it may be appropriate that they lead infertility investigations.
To illustrate the complexity of fertility investigations a case study is presented from a 200 breeder cow north coast beef herd.
CASE STUDY
The owner sought assistance because "the number of calves born seems to be dropping each year" and according to the owner "the calving rate used to be around 80% and now it was below 50%". The 2600 acre property near Bonalbo had been a family property for almost 100 years and the present owners who live off the farm had purchased the farm outright from another family member almost 10 years ago. At that time the property had around 100 breeders and stock numbers had been built up by retaining females although on occasions some small lines of heifers had been introduced as well. They are store weaner producers and sell weaners at the autumn weaner sales. Pasture fattening of weaned steers would only be possible with substantial pasture improvement.
Current situation
| Property details | |
|---|---|
| Size | 2600 acres in total with approximately 50% cleared for grazing. Remainder steep timbered country. |
| Topography | Elevation varies from 200 metres on the flats to 450 metres in the timbered elevated areas at the west. The grazing areas are undulating. |
| Soils | Mostly light sandy loams on flats. Basaltic soils in sloping elevated timbered areas. |
| Water | Two creeks traverse property which contract to pools in drought. Dams in paddocks without creek access. All paddocks have water available. |
| Paddock layout | Paddocks are generally set stocked to carry around 30-40 breeders with a bull. |
| Fertilizer history | Regular use of super up to around 30 years ago but nothing in past 20 years. |
| Pastures | Mostly native pastures. Flats are mostly paspalum compressum and small amounts kikuyu along creek banks. Extensive areas of blady grass on cleared slopes. Some years get clover in spring but minimal. |
| Weather | Average rainfall 1250 mm with 70% falling between December and June. Frosts regularly occur during winter. |
| Herd details | Stock numbers in April 2012 |
|---|---|
| Adult females | 172 |
| Unjoined replacement heifers | 58 |
| Calves | 50 |
| Bulls | 5 (1 missing) |
| Breed makeup | The herd has 2 main breed groups. About half the breeders have about 50% Brahman content and are mated to Angus bulls while the other half are of Hereford origin and mated to Brahman bulls. |
| Herd management | |
|---|---|
| Joining period | All year round joining |
| Age of heifers at first joining | Around 2 years of age |
| Bull mating rate | 1 bull per 30-40 females |
| Identification system | No individual identification system used. Just visual ID. |
| Supplementary nutrition | None |
| Herd health | |
|---|---|
| Vaccinations | Clostridial and lepto given to calves but boosters not given. No vibrio, EF or pestivirus vaccine used |
| Internal parasites | Whole herd treated with flukicide and pour on ML once yearly. Calves also given worming treatment at weaning. |
| External parasites | Irregular spray treatments for buffalo fly and ticks. |
| Grazing management | Paddocks are generally set stocked with some rotation. Some slashing is undertaken to control weeds but is
irregular as the owners work and live off farm. A next door neighbour is contracted to keep an eye out on
the place and will do minor fence repairs and move mobs of cattle and muster mobs for management
procedures. Pasture growth Nov- May. Several attempts at growing oats for grazing have failed due to flooding or drought. |
| Reproductive indices | |||
|---|---|---|---|
| Year | No. calves born | Number joined | Calving rate |
| 2011 | 124 | 210 | 59 |
| 2010 | 125 | 182 | 69 |
| 2009 | 129 | 167 | 77 |
| 2008 | 107 | 148 | 72 |
Property visit on 20th April 2012
Rectal examination
Female cattle were examined rectally for evidence of pregnancy and for those not detectably pregnant or with small calves, ovaries were palpated for CLs and follicles and the uterus was checked for metritis, RFMs, tears and post calving involution.
Because the herd uses all year round joining, calves of various ages were present in the breeding herd.
Clotted blood and swabs in PBGS were collected from a sample of each mob for pestivirus and vibrio testing.
| Class | Number tested | Number PD +ve | Comments |
|---|---|---|---|
| Maiden heifers | 52 | 23 | Majority were in good condition. A few had immature reproductive tracts and inactive ovaries. |
| Mob 1 breeders (Brahman dominant) | 92 | 36 | Average body condition. About 20% had small inactive ovaries. Many of the empties had normal ovaries and reproductive tracts on palpation. Quite a few had big bottle teats |
| Mob 2 breeders (Hereford dominant) | 71 | 27 | Much the same as the first mob. Second calvers were very poor performers |
| Disease | Number tested | Result |
|---|---|---|
| pestivirus | 13 ( all ages groups included) | All samples Antibody negative |
| campylobacter | 10 | 5/10 positive, ELISA units had 25-118 range indicating widespread infection. |
Results of investigation phase
- Vibrio is disseminated widely in the herd and would have contributed to the poor calving rate this season. The fact that it was detected in all age groups suggests recent infection.
- The herd appears to have not been exposed to pestivirus to date and is susceptible to infection should a PI emerge in the herd.
- There is evidence of nutritional anoestrus in the herd based on examination of ovaries and body condition scoring of females with older calves or empty at PD.
- There is wide phenotypic variation among breeders indicative of an ill defined breeder selection program.
- The lack of individual animal identification makes production monitoring and culling policy more difficult.
- All year round joining limits the ability to market adequate lines of store weaners at autumn sales.
Discussion
Based upon the findings of the investigation phase the following suggestions were given to improve the herd's reproductive performance:
- Cull all the bulls aged over 5 years. Vaccinate the remaining bulls with Vibrio vaccine 2 doses 4 weeks apart. Get the private vet to irrigate the prepuce with antibiotic just before giving the second vibrio vaccination. Give all the breeders a single dose of vibrio vaccine.
- The herd appears to be fully susceptible to pestivirus infection. Additional sampling should be undertaken to verify the results of the current sampling.
- Introduce individual animal identification using numbered coloured ear tags
- Introduce a restricted joining period. Put the bulls in with maiden heifers on July1 and with the main herd on 1 August. This allows the maiden heifers an extra month before rejoining next year.
- Join approximately 20% more heifers than are needed so that early conceivers can be identified and the slowest 20% can be sold (usually as in calf heifers excess to requirements).
- Weigh the maiden heifers on several occasions prior to joining aiming for minimum mating weights of 300 kgs. If indications are that meeting the target weight is unlikely a supplementary feeding program should be introduced.
- Purchase 3 additional 2 year old bulls to replace the culled and missing bulls. Aim for joining rates of 1/30 females. Make sure these new bulls are fully vaccinated before being put with females.
- Undertake pregnancy testing of the heifers around 1 Nov and get the pregnancies aged to identify those who conceived early in the joining period.
- Undertake pregnancy testing of the main herd in December and identify the pregnant animals with a secondary identification system such as tail banging. The pregnant subgroup can then be drafted off and the NDP group can get the best nutritional support to enhance the chances of conception.
- Maintain individual records for all breeding females (DOB, progeny details, calving dates).
While attending to the vibriosis problem will lead to improved reproductive performance in the short term, attending to improvements in nutrition and reproductive management are required to improve profitability in the long term. With these changes in place and ongoing monitoring it is then possible to benchmark the herd more accurately to link reproductive efficiency with profitability.