Dealing with late calvers

Speckle Park International magazine - 2022 edition Technical news

Bringing back the late calver

The return to oestrus of late calvers is the key to early conceptions, tightening calving distribution and driving weaner weights in a beef production system.

Late calving females can be a major source of reproductive wastage in Australian beef herds, contributing to economic losses, lower weaning weights and heifers unable to reach mating weights.

The 365-day reproduction cycle relies on a cow calving, reproductive tract involution, return to oestrus and conception within 84 days. Coupled with this, within a progressive, profitable cow herd, calves fall in a concentrated calving distribution, aligned with a seasonal pasture availability and prioritizing farm labour resources to breeder management.

Minimising the time from calving to resumption of oestrus and maximising the opportunity to conceive is the key to advancing the conceptions of late calvers and bringing them back into season with the rest of the cow herd. Selection pressure for fertility is a must; reducing the incidence of the cows drifting out of season. Select cows capable of conceiving within two mating cycles and bringing a live weaner every year.

Energy availability greater than requirements for all other physiological requirements is the main driver for return to oestrus.

‒ Relative to the dry cow

◦ a lactating cow requires 1.5 x energy for maintenance

◦ a growing, lactating first calf heifer requires 2.2 x energy for maintenance.

‒ The most economic way to maximise energy availability during this time is to calve cows in body condition score (BCS) 3.5 (1= too thin; 5=obese), they have body reserves for use when there is a deficit in provision of energy.

‒ When BCS may appear inadequate, if high quality feed is on offer – over and above that required for growth and maintenance – adequate energy can be redirected to the reproductive process.

Early post calving hormone treatment has been shown to advance conception date. Late calvers can be selected for an AI program to commence synchronisation as early as 14 days post calving followed by exposure to a cover bull for two cycles.

This method will not necessarily maximise conceptions to the AI round, however owing to early hormone treatment and oestrous synchronization will maximise conceptions earlier in the joining period. Treated cows will result in an earlier average conception date compared with an untreated mob. A twelve-week pregnancy test using ultrasound can diagnose conceptions to the AI round, nine-week pregnancies to the first cycle with the bull and six-week pregnancies to the second cycle with the bull.

Management of the late calvers with this program offers control to the producer, aids in nutritional management from calving to joining of this group and gives choice for retention or cull at the pregnancy test muster.

To maximise conceptions, frozen semen must be good quality and bulls must be fertile and in working order. There is no time for lost opportunities for conceptions.

Ultrasound scanning and measurement of follicles at AI can provide valuable information on every cow, giving choice around what value semen to use and whether to AI at all, serving to reduce semen wastage. Health events at calving including dystocia’s, infections, inflammation, metabolic disorders and acute nutritional disorders must be diagnosed early and managed well. Management of genetic selection, heifer growth prior to joining and during gestation, sound breeder nutrition will reduce the incidence of these events. Cows falling into this group will be difficult to advance conception date and may require culling from the herd.

Return to oestrus of late calvers is the key to early conceptions, tightening calving distribution and driving weaner weights in a beef production system.

Late calvers fail to join and drop out of the system, late calves have fewer growing days to weaning, lighter weights at weaning and heifers have less days to reach mating weight.

Good management and identifying opportunities to avoid the late calver or to advance the conception date will maintain a 365-day reproductive cycle and allow a concentrated calving distribution.

For more information on this topic or any other repro questions, call the Repro360 Helpline on 1300 163 056 or visit repro360.com.au

Tips for running a successful artificial breeding program

By Dr Sophia Edwards

Many Speckle Park breeders have already conducted an artificial breeing program. Whether you are new to artificial breeding or are well experienced, here are some tips to help along the way.

Most veterinarians or technicians will supply a protocol for you to follow on the timing and dosage of treatments for synchronisation. The timing and correct dosage is important to reach an optimal result.

Whether it be Fixed Time AI or ET activities, the best success is often achieved when females are on a rising plane of nutrition. Cows or heifers that are fat or well-conditioned surprisingly do not always deliver a good result.

The ideal state is for heifers and cows to be in a forward store condition and in a rising plane of nutrition leading into their reproductive program. Avoid pastures with legume content such as clovers and lucerne; this can be associated with disruption to the hormonal cycle. If supplementary feeding is required, a cereal hay diet is ideal. Place your artificial reproduction activities in your calendar and take some time to be a quality assurance officer.

Although artificial reproduction programs are easy to implement if the program is followed, if any one of the steps of the program fails, it will often result in poor performance. Ensure that steps to avoid disasters are implemented. For example, ensure that semen to be used in the protocol is of acceptable quality. Make sure all staff are well informed of activities and read the instruction labels.Although some good conception rates are quoted, and some of these rates are achievable, do your maths with the conservative average given your environment and cattle.

One good method for calculating what is possible in your herd with artificial reproduction is to critically assess your current reproduction rates. While a 90 per cent pregnancy rate seems high, if a breeder joins for six months, their conception rate per cycle may not be that good compared to a breeder that has an 80 per cent pregnancy rate and joins for 12 weeks.

If your herd has high innate fertility, it is expected your artificial reproduction rates will be good given all other factors are under best practice management.

For more information and resources visit: www.repro360.com.au

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