Maternal Might, Longevity and Weaning Ratios

Much of the cattle breeding fraternity’s focus at this time of the year shifts to the bull primarily because the bull, has the task of covering 40- 60 breeding cows per season for an expected 4 to 5 year life span. The prospective young sire purchase should be producing in the order of 220 – 250 progeny throughout his working life.

Importantly from the commercial cow/calf operators perspective this prospective young sire inherits economically important sets of genes from his dam. Up until recently it was postulated that 25% of the genes for the economically important traits, in the resultant progeny of this new sire purchase, would have come from the dam of the sire. Currently, genomics and gene sequencing are indicating that the ‘inheritance’ of the economically important genes may not be that ‘cut and dried’. Whatever the scenario suffice it to say that the maternal dam has a significant say in the genetic make up of the 220 – 250 progeny sired by this young bull throughout his working life.

The maternal plan must be considered in the purchase decision particularly if the new sire is destined to a self replacing herd.


In 2005 we started accurately calculating weaning weight ratios for all our calves born, this data has helped us select our future breeders.Given the longevity failure rate we are witnessing first hand and by word of mouth from fellow Angus seedstock breeders of a range of ‘brochure’ bulls in use , we have decided to promote the longevity trait, initially by presenting the weaning ratios for the dams of the bulls presented in this year’s Dulverton Angus Bull Sale.

While the weaning ratio directly doesn’t help us select for longevity and female stayability in the herd, the profile on the female generated by the weaning ratio data indicates her value in terms of her ability to remain functionally efficient (deliver a live calf and rear it to weaning) the more the merrier!!

Note that from the data set presented on the Dams of the 75 bulls in this year’s sale, 20 of these dams (27%) have had 8 or more weaners analysed. The average weaning ratio of these 20 dams is 98.5 or only 1.5% below the average. This would in dicate to us that while we are putting pressure on these cows to stay (until a ripe old age) we don’t appear to be sacrificing too much growth. The fact that these cows are able to stay does help us in maintaining the all important fertility sets of genes. It also ensures that their sons should inherit above average abilities re:

  1. The will to live and survive
  2. Structural soundness thereby helping those sires last as breeding machines for that required 4 – 5 seasons


The table with the dams of the Sale Bulls listed illustrating those dams’ weaning ratios to date is very valuable information. This data indicates that this list of dams are fulfilling their PRIMARY FUNCTION. Note that a Dulverton cow at Shannon Vale must:

  1. Settle in calf at 14 months weighing about 320kg. That heifer is synchronised for one AI (Artificial Insemination) then given 60 days exposure to a bull, to stay she must be pregnant.
  2. Deliver a live calf unassisted. Any heifer that has to be assisted is sold to slaughter, so too are her progeny.
  3. Settle in calf each year. Cows are synchronised for one AI cycle and given 60 days exposure to a mop up bull not all cows get the 60 days given that by the time we finish the third AI round there aren’t 60 days left pre the 15th December (prevents late calves – scours, pink eye etc.).


The Weaning Ratio is calculated by:

STEP 1: Average the weaning rates of the Management Group (set of cows running at pasture as a mob, at Shannon Vale we run 4 management groups).

STEP 2: Place the individuals weaning weight over the average weaning weight for the Group and multiply by 100 over 1. Note the weaning weight for a calf out of a 2 year old cow is adjusted up 15%, for a 3yo up 10%, and a 4yo up 5%. These adjustments were established by Dr Roger Barlow with the Trangie Research Station’s Angus herd in the late 1960s – early 1970s.

Take for example Lot 25 J086. He is by Dulverton Glory G131 out of the heifer Dulverton Annie G057. His daily gain at weaning was 1.48kg/day. When this gain is adjusted up 15% for age of dam it becomes 1.70kg/day.

Lot 69 is J246, he is by Dulverton Graphic G113 out of Dulverton Pixie G041. His actual daily gain at weaning was 1.28kg/day, adjusted up 15% for age of dam gives him a weaning daily gain of 1.46kg/day.


The worked examples illustrate the fact that J086 performed at 13% above the average for the group and J246 at 3% below the group average – Assume the average to be 100. By inference these ratios suggest that D. Annie G057 is an above average dam in terms of raising a bull calf to weaning, and that D. Pixie G041 is a slightly below average dam at rearing a calf to weaning.

Will we cull D. Pixie G041? Answer is No.

Why Not?

Her calf, which is her first calf, has only performed slightly below average, and has progressed to make the sale team. We would think that admirable for a first calver. Should her next calf perform in the low 90s for weaning ratio we would seriously consider culling her.

The C93 cow is very interesting, she weaned at 3% below her group average herself. She has had 6 live calves and reared them all to weaning for an average ratio of 105 or 5% above the groups average. These are cows we want more of, not all that large or high maintenance themselves yet they are weaning heavier than average calves, thereby promoting herd productive efficiency. No doubting the trait is ‘heritable’; C93’s dam is Z25 who has weaned 9 calves (only 8 analysed as her first calf was to a X – Bred bull), sure her ratio is dropping away yet joined to the right sire she will produce daughters with that very special productivity such as C93.


The inability of cows to raise live calves born to weaning is an issue for us. Should a cow fail on this account for reasons such as mismothering, ill thrift of calf then she will be culled. Should the calf die from accidental causes e.g. twins, intervention by human activity, moving mobs or by disease e.g. scours, pulpy kidney etc. then the cow is spared. The instances where the weaning number is one below the calf born number is high enough, it has occurred 20 times amongst this set of 75 bull rearing dams.

Example: Lot 20 J291’s dam A048 has had 8 calves and reared 7 of them, the one that wasn’t reared died of pulpy kidney. Note that her own weaning ratio is slightly below her group average of 98 and her 7 calves to date have weaned at 109 , she is worth retaining.

The average number of calves born by this set of 75 cows, the dams of this year’s sale draft, is 6.1. The average weaned is 5.8.

Some may argue that to have a bull breeding herd where the average number of calves born per cow is greater than 6 means the cow herd is too old. This maybe correct from a purist genetic theory perspective, the genetic theory argues that to maximise genetic gain for the traits being selected for then the generation interval should be reduced, that is, the younger 3, 4 and 5yr olds are the best. However a commercial cow calf operator wants cows to last/stay until they’ve weaned their 8th calf as a ten and a half year old. To do this it follows that the bulls this commercial cow calf operator is using, should preferably come from bull breeding herds with selection pressure on the stayability of the dams of these bulls.

We certainly aren’t ashamed of the fact that the average number of calves the set of dams represented by these sons in this year’s sale is in excess of 6. It is our contention that should a young bull be expected to work 4 –  5 years then he should be born from a cow that has jumped through all the fertility, structural soundness etc. hoops for at least that period of time and preferably longer.

When purchasing a bull it is always worth calculating the amount of that purchase price that can be attribute d to each calf born/weaned. For example given a purchase price of $5,500 and a working life of three years this sire should produce 120 progeny at a cost per calf of $45.80. Should that bull last five years and produce 200 progeny then that cost reduces to $27.50.

Maternal Might it is an issue of tremendous significance to our industry particularly during this next 3 – 5 years when the national cow herd has to be re-built.

Take Home Message

Don’t under estimate the value of the dam of your next bull.

  • He should last 4 – 5 years
  • He should produce 220 – 250 progeny in that time.
  • The dam of that bull has a substantial input into the performance of that bulls progeny especially replacement females

Use the data presented in the table to help build a profile on the performance and projected longevity of your next bull. Understand the longer the dam has been about, fulfilling her expected goals – fertility, have calves, weaners raised, weaners own performance, the longer her sons are likely to last.

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