Learn about Birth Wt and Calving Ease
in Angus GROUP BREEDPLAN

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Birth Wt & Calving Ease EBV
54 – What do Calving Ease and Birth Weight EBVs really mean
55 - Matching Birth weight EBVs and calving ease
56 - Selecting sires on Birth weight EBVs to join to heifers
57 - I don't measure Birth weight of my calves but get Birth Wt EBVs, why ?

54 : What do calving Ease and Birth Weight EBVs really mean.

Calving Ease (CE) EBVs estimate the difference (plus or minus) in the ease of calving that you can expect for the progeny of a sire, compared to breed average, when joined to “breed average” heifers calving as 2 year old.

Calving Ease EBVs are reported in two ways – Calving Ease (direct) & Calving Ease (daughters)

Calving Ease (direct ) reports the expected difference in the percentage of a sires calves that are unassisted at birth, compared to the breed benchmark. For example, you can expect the progeny of a sire with a CE EBV of +5% to average 2.5% fewer assisted calves from two year old heifers than the breed benchmark.

Calving Ease (daughters ) reports the expected calving ease of the sire’s daughters calving at two year old.. Again, this is expressed in percentage terms relative to the breed base.

Birth Weight (BW) EBVs estimate the difference (plus or minus) in kg of birth weight of a sires progeny, compared to the breed benchmark (0)

As for CE, the sires contribution to the performance of his progeny is 50%, therefore a sire with a BW EBV of =+6 kg is expected to produce progeny that average 3 kg heavier than the breed benchmark.

Whilst research has shown that birth weight is a major contributor to calving difficulty, high birth weight EBVs do not necessarily mean reduced calving ease. Shape of calf and pelvic size/shape and general fitness of the heifer are also contributing factors.

55 : Suppose I join a sire with a +6 kg birth weight to a cow with a 0 EBV for birth weight, are the results the same as mating a sire with a birth EBV of +3 to a female with a birth EBV of +3 kg. . . . . . . . . . . . . .Go to Top

Over time and with enough matings, the resultant average birth weight EBVs of the progeny will be about the same.

It should however be noted that the mismatch between sire and dam birth weight potential in the first mating example could provide a greater birth challenge for the cow than in the second mating example. Birth weight is associated with other growth traits and a small birth weight EBV could also indicate a smaller cow.

56 : What birth weight EBV would be suitable for my heifers. . Go to Top

The ideal birth weight EBV will vary with breed, calving time, geographic and environmental conditions. Experience has proven that less calving trouble will be experienced with a combination of low birth weight EBV in the parents and management to ensure low to moderate birth weight of the calves. Ideally, the birth weight EBV of the sire and heifer should be as close as possible. Anecdotal evidence suggests that the EBV of the sire should not be greater than +2 kg higher than the EBV of the heifer.

Don't forget - conformation of the sire, for example length of body and smooth shoulder setting is also important in minimising calving problems with heifers and needs to be assessed independently of birth weight. The sire's contribution to the pelvic size of his daughters is an important factor when they in turn calve.

57 : I don't measure birth weight but get birth weight EBVs - why?. . . . . . . . . . . . . . .Go to Top

Birth weight is highly correlated to weight at 200, 400 and 600 days of age. Where birth weights are not measured, Breedplan estimates a birth weight EBV from these later weights. Although estimated indirectly they are a good genetic estimate of birth weight differences from the herd or breed average.