“Performance review and then management planning aimed at improvement should be a regular part of the routine on any farm but can often be neglected because of the many and varied day to day tasks necessary to look after the animals and ensure their health and welfare,” says Keith Cutler, Veterinary Surgeon at Endell Veterinary Group and a member of the NBA’s Animal Health Committee on behalf of the National Beef Association (NBA). The advent of a new year might provide an opportune moment to look back and reflect on performance over the year just gone and to ponder whether and how improvements might be made in the coming year.
Here Keith gives advice on – when planning herd health – how comparing a few basic ‘key performance indicators’ against targets might be a useful place to start.
· How many cows and heifers were put to the bull last year?
· How many calved and how many animals were lost?
This information will start to provide some assessment of herd performance but at a very superficial level. To make the assessment more meaningful and useful, information about the duration of the calving period and the distribution of calvings within this period is necessary.
More information about losses including differentiating culls into voluntary and involuntary, information about the age of the animal lost and the reason for the loss (including the number of pregnant cows which never calve, which will require pregnancy diagnosis to be carried out at the appropriate time) will allow common themes to be identified and then hopefully addressed.
A fully fit and fertile bull ought to be able to get at least 60% of the cows he is running with pregnant within three weeks. This is assuming a satisfactory bull:cow ratio and that the cows are all fit and healthy and cycling normally. If this is achieved this means that of 100 cows put to the bull 93 should be expected to be pregnant after a nine week bulling period, with 60 of these conceiving within the first three weeks. Extending the serving period by a further three weeks should result in a further four cows in-calf. Extending the serving period beyond this may result in one additional pregnancy for each three weeks the serving period is extended but is this sensible or is it false economy?
In any seasonal system, the later a calf is born during the calving period the younger and therefore smaller it will be at weaning resulting in it being less valuable. It will also be exposed to a greater infectious pressure than calves born early during the calving period and so is more likely to become ill. This will require it to be treated and further reduce its performance, and could result in death.
In addition, cows which calve late during the calving period will have less time for the uterus to undergo involution and for ovarian cyclicity to restart than cows which calve early during the calving period before they are put back with the bull for the subsequent serving period. A cow which calves on the first day of a three month calving period will have three months ‘open’ before being put back with the bull. However, a cow which calves on the last day of a three month calving period will be put back with the bull the day after she calves (if the seasonality of the herd is to be maintained). Early calving cows tend, therefore, to conceive early during the subsequent bulling period. They remain early calving cows year after year, whilst later calving cows tend to slip further and further in the calving period each year until they fail to conceive within the desired time period, forcing a decision about whether to extend the serving period, carry them round or cull them.
A tight calving period also makes herd management much easier; many management tasks (disbudding, vaccination and weaning for example) can be carried out on a group rather than an individual basis allowing labour in particular to be better planned.
Looking at the spread of calving within the calving period might also give an insight into the management and health of the herd. If more than 95% of the cows put to the bull conceive within a twelve week period and then at least 60% of these calve within the first three weeks of the calving period this might suggest that there is not too much to worry about. If, however, as many calves are born during the final three weeks of the calving period as are born during the first three weeks, then this might suggest compromised fertility. This may be due to a number of causes; was nutrition and cow condition optimal, were the bulls used all fully fertile or is infectious disease compromising performance?
From a nutrition point of view – whilst minerals and trace elements can be important – energy status, body condition score and how it is changing are more likely to be significant. Cows that are too fat at calving tend to have more difficult calvings. This can result not only in more dead calves but also in more uterine problems after calving often having an adverse effect on future fertility. Cows that are too thin will take longer to return to cyclicity and to conceive. Weaning thin cows before fatter cows can provide a potent means of manipulating body condition score. If supplementary feed is required on a herd basis there is benefit if this is done sooner rather than later and cows should be in a ‘fit-not-fat’ condition and on a rising plane of nutrition for at least six weeks before and during the entire serving period.
The published literature consistently reports one in ten bulls to be infertile which means they are incapable of successfully impregnating cows. A further two in ten are reported to be sub-fertile. These bulls will successfully get cows pregnant but less efficiently than fully fertile bulls (so either fewer cows will calve than hoped or the calving period will extend). A thorough pre-breeding examination of each bull would hope to identify ‘problem’ bulls so that they can be replaced before being used. At the very least body condition and locomotion should be evaluated and a critical assessment of the penis and testicles should be carried out prior to the breeding season to make sure that there are no obvious problems. You should then continue to watch the bull during the serving period to ensure that he is working properly.
From an infectious disease point of view the options are many and varied. Some of these will have a direct effect on fertility, BVD for example, whilst others, such as Johne’s disease will have an indirect effect. Some may affect calf viability and result in pregnancies being aborted. Herd health status should be discussed with your vet who will be able to plan with you surveillance strategies and plans to protect the health of the herd, if no evidence of disease is found, or to control the disease and mitigate its effects, perhaps by implementing a vaccination or other management programme, or an eradication programme, if disease is identified.
This, of course, is herd health planning, which, when carried out proactively by monitoring and analysing performance and using the results of this to influence herd management aiming for improved performance, should deliver both easier management and economic advantage.
