In basic terms the fertility efficiency of a beef suckler herd
can be defined as achieving the maximum output (kg) of saleable
beef per breeding cow per year (Fig 1). Any factor that
prevents a cow from conceiving, carrying a calf to term, delivering
a live calf and rearing it successfully to weaning will therefore
have an impact on herd fertility.
Fig 1: In basic terms the fertility efficiency of a
beef suckler herd can be defined as achieving the maximum output
(kg) of saleable beef per breeding cow per year
Many vets are experienced at analysing dairy herd fertility and
do this as part of routine herd fertility visits using computer
generated printouts which allow detailed analysis with little
effort. The situation in beef herds is completely different
with few farmers and vets ever sitting down to discuss detailed
fertility analysis. One of the main reasons for this is that
few farms have fertility data that can be easily produced in a
useable format without considerable effort. The data needed
to carry out basic fertility analysis and benchmarking is not
complex but without recording and analysing this data the farmer
and vet cannot identify areas of loss and work to improve
The minimum data that should be gathered for annual analysis is
shown in Figure 2, and from this data you can calculate some key
benchmark performance figures.
What are the key
performance figures ?
Three benchmark figures that can be useful to highlight are
% cows calving of mated - TARGET >
This figure reflects overall herd
fertility which is influenced by cow and bull factors and in a
fertile herd a target of 95% females calving following a 9-10 week
mating period should be the aim. In herds consistently getting >
5% barren cows there should be an investigation for potential
causes of infertility which could be failure to conceive or
abnormal pregnancy loss/abortion. An analysis of the barren
cows' information is useful eg. were they mostly young or old cows
? when did they calve in previous calving period ? and did they
have bad calvings.
% cows calved in 1st 21 days of calving
period - TARGET > 65%
This is a useful benchmark figure to
calculate as it reflects overall fertility efficiency of cows and
bulls. Note when calculating this figure calculate day 1 of the
calving period by adding 285 days onto the date the bulls were put
in with cows. Include all cows calved in the next 21 days
plus any calved prior to the calculated start of calving (Figs
3-4). If this figure is calculated form the date the first
cow calves (which may be up to 10 days early with twin calvers etc)
the benchmark figure will be inaccurate and not comparable within
herds and years. Herds achieving this target will have fertile
cyclic cows and fully fertile bulls (see bull fertility
bulletin). The higher the % of calves that are born in this
period the higher the average weaning weight which will
significantly boost herd output.
Calf crop % - TARGET > 94%
This is a useful figure to calculate
as it reflects overall fertility output including calf mortality.
Recent QMS survey data suggests the average calf crop % for
Scottish suckler herds is between 85-90% with a
wide range around this average. If the calf crop % is < 90%
figures must be analysed to see where in the production cycle the
losses are occurring ie. is it poor cow fertility or subsequent
calf losses that are the problem.
Without farmer and vet analysing these
figures together it is hard to target advice and efforts to
maximise profits. It may be much easier to improve output by
reducing areas of calf losses (eg dystocia and neonatal disease)
than trying to push herd pregnancy rates up by a few %.
Figs 3 and 4: These calving histograms show the
advantage of synchronisation when all cows are mated on day 1 of
the breeding period leading to a compact
How to achieve targets for beef herd
To achieve these targets it is
important to pro-actively manage the herd to ensure all areas of
potential fertility inefficiency are being addressed. In the
rest of this bulletin and in bulletin 2 we will consider the main
areas that need managed to ensure success.
These areas are :
- Cow body condition and nutrition
- Replacement heifer management
- Reducing dystocia and calf
- Controlling infectious diseases that
- Monitoring bull fertility
Cow body condition, nutrition and
After calving it is normal for cows to
have a period of anoestrus (acyclicity) when the ovaries are
inactive. In beef cows the 2 main factors which influence the
length of the anoestrus period are suckling by the calf (Fig 5),
and body condition at calving. Calf suckling inhibits
the release of hormones in the brain which stimulate the ovaries to
become active again after calving. As calves get older and suckle
less frequently this effect wanes and the ovaries become
active. Restricted access suckling and calf separation has
been shown to significantly reduce the post calving anoestrus
period in beef cows however it is impractical for most farms to
manage this even for short periods so is a tool unlikely to be used
Fig 5: Calf suckling is the main factor inhibiting
cyclicity in beef cows after calving
The second most important factor
controlling resumption of ovarian activity post calving is cow body
condition at calving. Recent studies in Ireland with spring
calving suckler cows confirmed clearly that the critical
factor controlling post calving anoestrus period is body condition
score (BCS) at calving. Increasing the energy feed
levels of cows that calve in poor body condition in the immediate
post calving period had negligible effect on shortening the post
calving anoestrus period . Nutritional planning must be
focussed on achieving target calving condition scores if good
fertility is to be achieved in restricted mating periods.
Fig 6: Spring calving cows calved in BCS 2.5-3 will
resume cyclicity within 50-60 days in most
On average, a beef suckler cow calving
in moderate to good BCS will have an anoestrus period of 50-60 days
(Fig 6). Thin cows, especially 1st calvers which
are still trying to grow and suckle their first calf will be at
risk of having anoestrus periods of 70 days or more (Fig 7).
The effect of prolonged anoestrus in a restricted mating period of
9-10 weeks is shown in Figure 8 (below).
Fig 7: First calvers are at high risk of extended
anoestrus if calved in poor body condition and not managed
What this diagram shows is how a
normal anoestrus period of 8 weeks (56 days) influences the cows
opportunities to get re-bred. Cows that calve in the first
month of calving, if in good BCS are highly likely to be cyclic by
the time the bulls go out and thus have 3 or more chances of having
a fertile heat during the mating period. This is another reason why
the target of 65% or more calving in 1st 3 weeks is a
key figure. Herds that achieve this have the best chance of
cows rebreeding plus wean heavier calves.
Thin cows, even if they calve in month
1 of calving period are unlikely to start cycling until after the
bulls are in. Worse still, thin cows that calve late in the
calving period may only start cycling in the last few weeks of the
mating period meaning they are at risk of ending up barren.
If you have a lot of barren 1st calvers at PD it is
quite possible that this is simply down to extended anoestrus -
they can't get pregnant if they are not cycling when the bulls are
in! Obviously having extended mating periods where bulls are
run for 5-6 months will solve this problem but lead to inefficient
herd management due to extended calving periods.
- Plan nutrition to achieve target BCS
- Thin cows, especially 1st
calvers will be less likely to conceive during restricted mating
periods simply due to delayed cyclicity.
What about trace element deficiency ?
The 'quick fix' for infertility is
often to buy expensive mineral/vitamin supplements or blame some
obscure dietary deficiency. The fact is that most cows on a
properly planned winter diet with general purpose mineral/vitamin
supplement will be unlikely to have any deficiencies severe enough
to influence fertility. If a farm has a history of severe
deficiency in copper, selenium or iodine in grazing animals then it
is clearly sensible to address this especially in bulling heifers
which are most likely to be affected. Most infertility
related to diet is down to extended anoestrus due to poor planning
of pre-calving diets or grassland management.
The next critical area to manage to
ensure good fertility is integration of replacement heifers and
this is dealt with in the next bulletin.