Breeding management and fertility - the main factors to consider
A key aspect of running an efficient suckler system is good breeding management and herd fertility. Cow nutrition, bull fertility, the incidence of calving difficulty and herd health are some of the main factors that affect fertility in the herd.
The traits described below in Table 1 highlight average national reproductive performance of a spring-calving suckler system compared to target performance of research farms or high-performing commercial farms. The difference between current national performance and targets shows that there is potential to improve the reproductive performance of the Irish suckler herd. It is worth noting that these targets are being reached on high-performing commercial farms, so this level of performance is achievable.
The current national average of 0.86 calves per cow per year means that only 86 cows in a 100-cow herd are weaning a calf every year. Achieving 95 calves weaned per 100 cows in a herd requires excellent cow and calf management, from achieving the correct body condition score (BCS) at key time points through correct nutrition, to a good herd health status though a proper health plan to appropriate housing. Calving heifers at 24 months of age is also key to reaching reproductive targets.
Earlier and compact calving of the herd is required to match turnout date with grass growth pattern in spring-calving systems; this date will vary across the country depending upon conditions. The national average six-week calving rate is 25% poorer than the target, indicating that there may be several issues at farm level, such as inadequate heat detection, anoestrus cows or sub-fertile bulls. Heat detection needs to be excellent and at least 90% of cows should be submitted for AI or served by the stock bull in the first three weeks of the breeding season; there are several options available to improve heat detection which are outlined below.
Table 1: Reproductive targets for a spring-calving suckler herd versus national average
|Key Performance Indicator (KPI)||National average||Target|
|Calving interval (days)||396||365|
|Age at first calving (months)||32||24|
|6-week calving rate (%)||55||80|
In Ireland, less than 20% of calves in suckler beef herds are bred from artificial insemination (AI). Such low usage of AI most likely reflects the difficulty and labour requirements for heat detection, assembly of cows for insemination and land fragmentation in beef herds.
Oestrous or heat synchronisation is the process of manipulating the oestrous cycle of the cow using synthetic hormones to better manage the timing of breeding. The benefits of using heat synchronisation include: align breeding and calving to best suit the availability of labour; 100% submission rate using fixed-time AI; and inducing heat in anoestrous cows. Increased AI improves the use of higher genetic merit bulls and a more focused replacement heifer policy, as well as improving the opportunity to compact the calving season.
To develop and test a robust and repeatable timed AI programme for Irish suckler beef farmers, Teagasc conducted a large on-farm trial, which involved fixed-timed AI of over 2,200 cows on 85 herds throughout Ireland. An overall pregnancy rate of 55% to the timed insemination (first-time submission) was achieved, which is good considering that approximately 50% of the treated cows were anoestrous (not resumed heat cycles) at the start of the protocol. When combined with repeat matings, 80% of synchronised cows were pregnant in the first three weeks of the breeding season, which has very positive benefits for average herd calving interval and compactness of the subsequent calving season.
Regimens for heifers
As the vast majority of replacement heifers should be cyclic during the breeding season, there is a reduced requirement for incorporating an exogenous source of progesterone in the regimen for heifers. Consequently, prostaglandin-based regimens are the method of choice for use on replacement heifers. An effective regimen involves good heat detection initially carried out for six days and all heifers detected in heat are inseminated. On the sixth day, all heifers not yet detected in heat are injected with prostaglandin. The injected heifers will respond to the prostaglandin and show heat 2-4 days after injection and should be inseminated as normal; conception rates of 65-70% should be expected. The remaining heifers not yet recorded in heat and inseminated can be treated with a second prostaglandin injection 10-11 days after their initial injection. Up to 80% of heifers will respond to one or two injections of prostaglandin. Using this protocol drug use, semen costs and veterinary costs are minimised.
Bull fertility is key to maintaining a compact calving period and overall herd profitability. The reported incidence of infertility in stock bulls is generally low (3-5%), however, subfertility is much more common (20-25%), with significant differences among individual bulls.
Subfertility may be caused by low libido, sperm quality/quantity, defects or physical factors affecting bull mobility or mating ability. Frequently, sub-fertile bulls go undetected and farmers may be unaware of the problem until much of the breeding season has elapsed or until pregnancy scanning.
Furthermore, there is no guarantee that a bull will retain his fertility from season to season or even within a season. Thus, farmers must be continually vigilant for potential fertility problems so that corrective action can be taken.
Regardless of the breeding strategy used, good heat detection is vital for successful breeding. There are a number of methods that a farmer can choose from.
- Visual heat detection: observe all cows for a minimum of twenty minutes, four times per day, spread evenly across the day as much as possible.
- Vasectomised bull: a vasectomised bull fitted with a chin ball marks the cows on the top of their backs when he is serving them. Position yourself to see the marks on the backs of the cows, and ensure that the paint in the chin ball is topped up as required.
- Digital technology: systems that are based on cow activity and rumination can be used to alert farmers that a cow is in heat or systems that incorporate a vasectomised bull and use proximity alerts to notify a famer that the cow is in heat.
- Tail Paint: apply a narrow strip 1.5-2.0 inches in width to the tail head. When the paint is completely rubbed off the cow, she is in standing heat. It is helpful to change the colour of the tail paint when the cow is AI’d, to help identify repeats and undetected cows.
- Heat mount detectors: Scratch cards and Kamars applied to tail head - changes in colour indicate heat.
A comprehensive health plan is vital for prevention of diseases that may cause reproductive wastage in suckler cows. A farm-specific vaccination protocol should be discussed with your local vet. Some common diseases include: rotavirus; coronavirus (vaccines should be administered between 12 and three weeks before calving); bovine viral diarrhoea; leptospirosis (vaccines should be administered approximately four weeks before breeding); and infectious bovine rhinotrachitis (IBR) (vaccines should be boosted every six months). Other diseases should be vaccinated for if they are found to be present on farm.
This article from Colin Byrne, Martina Harrington, Peter Doyle and David Kenny was adapted from the Beef 2022 ‘Supporting Sustainable Beef Farming’ open day book.
Also read: Monitoring a young bull's performance throughout the breeding season
Also read: Selecting beef heifers for breeding
Listen: Key aspects of a synchronisation regimen for a suckler beef herd