Average Age of Beef Heifer to Have First Calf

Selecting and Managing Heifers for Convenance

The backbone of a cow calf product system is the choice and integration of heifers into the beef herd. The replacement rate varies considerably between farms simply on average lies between 10 to 20%. The decisions effectually which cow to cull ranges from age of cow, breeding success, calf quality, rearing success, temperament of cow, cow health etc. In the majority of cases, the historic period of the cow is the number one determinant on which cow should be culled.

Since the replacement heifer is the foundation of a productive cow herd, the choice of heifer and her evolution tin can greatly impact the economic science of the farm operation through her genetics, future performance, and longevity. Fourth dimension of first calving has a major influence on life time productivity, which is one of the nearly important traits to consider. Research has consistently shown that targeting first calving at 24 months maximises lifetime productivity, provided the cow continues to produce a calf each year. Research from Oklahoma State University College of Agriculture Sciences showed that heifers calving at 24 months produced 330 lbs of dogie more over their lifetime than heifers calving at 36 months.

To calf at 24 months, heifers must exist bred by 15 months of age. The onset of puberty in cattle is adamant by weight, age and breed. Weight is the major factor. The age at which puberty occurs is breed dependant with larger, later on maturing breeds coming into puberty subsequently than smaller, earlier maturing breeds.

Table 1. Weight (lbs) at which 14 - 15 month quondam heifers of unlike breeds reaches puberty.

% of heifers in heat	Angus	Hereford	Charolais	Angus x Hereford	Simmental x British	Lim x British
50	550	600	700	550	650	650
65 - 70	600	650	725	600	700	700
85 - 90	650	700	750	650	750	750

Source: J. Field, OMAFRA

Table 1 shows the effect of weight on the % of heifers in a herd at 14 - fifteen months of age which bear witness first heats, (onset of puberty). It demonstrates that before maturing breeds, i.east Angus, Heredford, achieve puberty at a lighter weight than larger framed breeds, i.due east. Charolais, Simmental. Farmers should bear these target weights in mind when selecting heifers to brood. Larger framed breeds must weight heavier at the target convenance date, i.e 15 months, compared to smaller framed breeds. Feeding the correct nutrition to heifer calves, taking into account breed, is important to ensure heifers achieve their target weight past 15 months of age.

Replacement beef heifers should reach 65 to 70% of their potential mature weight by the time they are bred at fourteen-xv months of age. From weaning to first breeding, heifers should gain an average of 0.56 kgs to 0.80 kgs, (1.25 lbs to one.75 lbs), per 24-hour interval or 115 to 160 kgs, (250 to 350 lbs), total (depending on breed). For most breeds and crosses, heifers should weigh betwixt 300 to 390 kgs, (650 to 850 lbs.), at breeding fourth dimension.

Lifetime productivity rates are affected by feeding direction during critical phases. Inquiry has shown that energy intake in excess of requirement can pb to the infiltration of fatty into the developing udder which may restrict milk production in those heifers as cows later in life. Poor milk product leads to poor dogie functioning and earlier culling than planned for that animal.

Table 2. Nutrient Requirement for Replacement Heifers (growing at one.25 lbs per day).

Medium Framed Heifers

Body Weight (lbs)	Dry Matter Intake (lbs)	Total Poly peptide (lbs)	TDN (lbs)
400	10.03	1.08	6.65
500	11.86	1.16	seven.86
600	13.sixty	1.24	9.01

Big Framed Heifers

Body Weight (lbs)	Dry Matter Intake (lbs)	Total Protein (lbs)	TDN (lbs)
500	12.75	1.24	7.82
600	14.61	ane.33	8.97
700	16.41	1.41	x.07

Source: J. Field, OMAFRA

Table 2 shows the ideal nutrient requirement of growing heifers at various torso weights. Medium framed heifers accept a lower feed requirement at the same weight every bit big framed heifers. Producers must be witting of the frame type of heifer on their subcontract to avoid underfeeding or overfeeding.

Producers should plan breeding of heifers at least iii weeks before breeding the balance of the herd. Heifers accept longer to cycle post calving than mature cows. By allowing a 3 week gap at convenance, showtime calf heifers will probable show heats post calving at the same time as the principal herd. A breeding season of 45 days is acceptable for heifers provided they are in good nutritional status. To maximise the return from heifers, it's important to pregnancy cheque all heifers and cull those not in calf.

Heifers are very sensitive to calving difficulties. Enquiry by Ontario Veterinary College has shown that on boilerplate 22% of get-go calf two year olds require help, and work by the University of Arkansas has shown that up 34% of first calf 2 yr olds require assistance. Heifers must non be over or underfed as both weather can pb to calving difficulties. The birth weight of the dogie is related to genetics, less nutrition. Underfeeding will restrict the growth rate of heifers, reduce the size of the pelvis and increase the rate of calving difficulty. Overfeeding equally reduces the size of the nascency canal due to backlog fat deposition.

Beginning calf heifers should be separated away from the main herd prior to calving. Calving should be monitored closely, but not obtrusively, to avoid increasing stress on the beast (which may delay calving), and provide help where necessary. The calving process tends to have longer in first calf heifers versus mature cows.

E'er check that the newborn dogie has sucked. Start calf heifers are very inexperienced in assuasive calves to suckle and assistance may be required. Great care must be taken when handling calves of heifers. A previously quite heifer may go extremely unsafe and unpredictable post calving.

The all-time method to reduce the risk of calving difficulties with first calf heifers is to breed heifers to an easy calving bull. Calving ease is the relationship between calf birthweight and moo-cow pelvic size. Research has shown than in eighty% of cases where calves die at birth, they were normal, and presented in the correct "diving" position, merely the cause of death was suffocation. These types of deaths are primarily due to a mismatch between calf birth weight and dam pelvic size. Calf birthweight varies between breeds and within breeds, but a articulate distinction exists between smaller framed, earlier maturing breeds and larger framed, later maturing breeds. Producers should select bulls with low dogie birth weight when breeding heifers.

Pelvic measurements take been used by some producers as a means of selecting heifers for convenance. The University of Nebraska has developed ratios that can be used to determine the calf birthweight that a heifer could potentially successfully evangelize. Measurements are taken at 12 to 13 months of age using a pelvimeter and from those measurements a maximum dogie birthweight can exist determined.

In Australia, pelvic measurements are primarily used every bit a alternative tool to successfully identify abnormally modest or abnormally shaped pelvises rather than as a convenance selection tool. These situations, if left unidentified, are associated with extreme calving difficulty, resulting in caesarean delivery and fifty-fifty death of the calf, cow or both.

Good selection and direction of heifers for breeding is critical to the genetic advocacy of the herd and the long term profitability of the beef farming enterprise.

References

Field, J. 2015, Feeding and Managing Replacement Beef Heifers, OMAFRA Fact Sheet.

Carson, Marker E., 2011, Preparing Heifers for Convenance, OMAFRA.

Lardner, Dr. Bart, 2014, Effect of Development System on Growth and Reproductive Performance of Beef Heifers. J. Anim. Sci. 7:3116-26.

Comerford, John W., 2011, Replacement Heifer Selection, PennState Extension.

Patterson, John, 2013, Tips to consider when selecting replacement heifers, Beef USA.

Patterson, David J., 1997, Pelvic Measurements and Calving Difficulty, University of Missouri Extension.

Troxel, Tom R., 2011, Pelvic Area Measurements in the Measurements of Replacement Heifers, University of Arkansas Agronomics and Natural Resources, FSA 3010.

Fahey, Thou., Boothby, D., Fordyce, G. and Sullivan, 1000. 2000, Female Selection in Beef Cattle, Queensland Beefiness Manufacture Institute, Q10047

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Source: http://www.omafra.gov.on.ca/english/livestock/beef/news/vbn0718a2.htm

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