Happy New Year, hopefully the rewards to those of you who continue to follow the pathway of a dedicated beef cattle breeder will be commensurate with the time and effort you have committed to achieving your goals and outcomes. In the last edition I discussed “Beef Fertility” and attempted to outline how important fertility is in determining enterprise profitability and how important management is relative to the genetic component in determining the outcome. Dr Rex Butterfield has, through his now famous statement “Dead calves have distressingly poor growth rates” positioned the need for live calves in the beef enterprise. Live calves, a fundamental need of the beef enterprise, are a function of a number of factors. These include:
- Female herd management
- Calf Shape
- Birth Weight
- Pelvic size/area and shape
- Gestation length
1. Female Herd Management
The genetic contribution to live calves born is higher than that of fertility but is still reported in the scientific literature as having low heritability. This means the most significant contributor to the expression of the trait (live calves born) is the environment and its management.
Female herd management to maximize live calves born can be quite easy. Simply start with the maiden heifers and follow a step-by-step procedure
Step 1 Map out a projected growth pathway acknowledging the three critical control points.
i) Weaning ii) Joining iii) Calving
Identify the age range for these three events and then a weight gain per day (growth rate), between these three control points. Consider the following pathway.
Suggested growth path to help maximize live calves born
Birth to Weaning
- Heifer weaning weight 240-270Kg.
- Weaning weight age 240-270 days.
- Heifer gain birth to weaning 205-235Kg
- Targeted gain per day birth to weaning 0.85Kg.
- Birth weight 35Kg
Wean to Joining
- Heifer joining weight 290-320Kg
- Heifer joining age 380-420 days.
- Time interval weaning to joining 140 days.
- Heifer gain weaning to joining 60Kg
- Targeted gain per day weaning to joining 0.45Kg.
- Heifer weaning weight 240-270Kg.
Joining to Calving
- Heifer calving weight 420-470Kg.
- Heifer calving age 690-720 days.
- Time interval joining to calving 283 days.
- Heifer gain joining to calving 130-150Kg
- Targeted gain/day joining to calving 0.5Kg.
- Heifer joining Wt 290-320Kg.
One assumption made is that heifer calves will grow at about 5% slower then their steer calve siblings up to 400 days (Barlow Roger). It is advisable for a live calve outcome, to mange the nutrition to achieve the targeted growth rates for the three intervals rather than to simply budget on a whole of life (birth to 720 days which represents age at first calving) gain of 0.6 to 0.62 Kg/day. Interestingly, a 2-year-old weighing 420 to 470Kg at calving should end up with a mature cow (5yr.old) weight in the order of 540 Kg at calving. This represents a sensible mature cow weight from a whole of herd gross efficiency perspective. That is, large enough to produce calves with sufficient growth potential to achieve the various carcase weight targets of 320 to 400Kg and yet not too large as to put pressure on the ability to maintain that cow particularly during periods of nutritional stress e.g. winter. A check for fatness or body condition score and so maturity pattern is also important. Guard against the growth, particularly during the phase joining to calving being composed of too much fat. Aim for a 2 plus to 3 condition score (4 to 10mm of p8 fat). If the heifers are too fat they will suffer from ‘lazy calving’ syndrome. That is, the excess fat will restrict muscle tone development too the point where the heifer will take to long to have the calf or worse still not be able to deliver the calf due to her having stopped contracting prior to delivery.
Be careful not to end up with heifers that are too lean otherwise their maturity pattern may end up very late which will impact on age/weight for onset of first oestrus and general do-ability, the ability to quickly respond to seasonal improvement.
Step 2 Understand Fetal Nutrition
The growth and therefore nutrition of the foetus should be thought about in the trimesters, the three, three monthly periods of the gestation (conception to birth). It has been shown particularly in dairy heifers that fetal nutrition in the first trimester is critical to calving ease. If heifers are on super high nutritional planes during this time then they will be establishing the capacity for larger than is necessary “life lines” in the form of blood (nutrient) supplies from the heifer/cow to the foetus. Calf birth weight is in the order of 35-40% heritable (Cundiff and Gregory Clay Center USDA); therefore the remaining 60-65% of the expression for that trait is due to conditions in the uterine environment. The super high heifer/cow nutrition during that first tri-mester will therefore result in heavier than is necessary fetal weights at the time of birth, this can lead to dystokia problems. Managing heifer nutrition does present problems at the time of and during the commencement of the first tri-mester. On the one hand the issue confronting fertility is to have the heifers on a rising plane of nutrition and on the other hand it is important not to have these heifers that have settled into calf early on too high a plane otherwise they will be establishing that blood supply life line to the foetus with the potential to create heavy fetus’s at ‘term.’ This may well create calving difficulties. This is another reason to mange the joining period of the heifers, in particular, so that they aren’t on too good a paddock for much more then 6-8 weeks. Immediately after joining get them onto feed that will sustain their growth at 0.45 to 0.5 Kg/day even and adequate growth for each individual. Managing heifer and for that matter cow nutrition during the second and third tri-mesters is also critical. Remember the flow line of nutrient from dam to foetus is established during that first tri-mester. If nutrition for the heifer becomes limiting once the ‘flow line’ is established then that dam will draw on her body reserves to keep the nutrient supply up to the foetus. The fact that the two year old in particular is being starved that is drawing on her body reserves means she is not developing to her potential frame and skeleton size. As a result, the pelvis may not develop to the point where it can successfully ‘deliver’ the foetus. I have never been one to support the theory of starving heifers so as to reduce dystokia. Keep that pelvis growing and developing right through the second and third tri-mesters. That is keep them growing at 0.5 Kg/day through the length of the gestation watching that they don’t get fat in that third tri-mester. The fat cow/heifer will be the lazy calver. N.B If the heifers get too fat at a growth rate of 0.45Kg to 0.5Kg/day then they are more likely too early maturing. Exercise during calving will definitely help so where possible give heifers some hills to move about in but protect that growth of 0.45 to 0.5Kg/day.
Heifers starved during the final tri-mester don’t milk to their full potential as a result their heifer calves won’t develop skeletally (tissue of the body develops as follows bone, muscle, fat), during their first 4 to 6 months of life. Therefore they will have problems when it’s their turn to calve.
Step 3 Sire Selection
Be sure to have a sire selection set of criteria for the maidens. The list needs to include:
- Birth weight, gestation length and calving ease of daughters EBV’s (to be discussed later in the article).
- Growth and maturity pattern
- Shape particularly length of body, neck extension, shoulder set, width at pin bones and bone shape.
- Age and body weight of sire. Where possible use yearlings or two year olds weighing 650 to 700Kg maximum over maiden heifers. Remember those heifers only weigh 280-320Kg at joining.
Step 4 Monitor heifers during calving
Heifers that have to be assisted during calving must be identified and disposed of as a slaughter animal prior to being re-joined.
Step 5 Monitor calves born
Any calves that have to be assisted must be identified and recorded and disposed of as slaughter animals. Never use assisted calves as future breeders. Just as fertility is lowly heritable and infertility highly heritable. Dystokia (the reserve to live unassisted calves) is highly heritable. Get rid of the problem before it magnifies itself.
2. Calf Shape, Pelvic Area and Shape
In the current era where more and more pressure is being brought to bear on cattle achieving 350-420Kg-carcase weight at 20-28 months with optimal fat levels (taste and muscle preservation) corresponding pressure is brought to bear on lives calves born. Heavy calves have higher survival rates and have the potential to grow faster and leaner. Calf shape does have a significant influence, some will argue even more significant than birth weight, in achieving maximum numbers of live calves born.
What is the preferred shape?
Understand that the calf must be delivered through the birth canal and so the pelvis of the heifer/cow in effect determines the preferred shape. The birth canal has width and height limitations. Therefore the long slender calf with angulations in the joints particularly the shoulder has a much better chance of being delivered alive than a calf with a thick ‘bully’ head, thick shoulders with little or no angle and excessively wide hips. The shoulder angle of about 45 degrees is necessary to allow the shoulder to mould in behind the head as the calf progresses down the birth canal. If the angle is too steep, 60 degrees plus, then the shoulder is too straight and so the floor of the chest of the calf and the top of the shoulders will jam in the pelvic canal. Likewise thick shouldered calves suffer the same fate.
Like begets like (Colonel De Quincy) therefore to help reduce dystokia and maximize live calves born be sure to select breeding stock with the preferred calving ease shape:
- Long bodied
- Adequate angulations in the shouldered 45 degrees
- Long head
- Neck extension
- Width in the pin bones
- Longer flatter bone pattern, Optimum bone
Guard against the thickset body with straighish shoulders, thick bully heads and round to oval excessive bone.
Doug Tozers analogy – bovine shape to wine bottle shape is a good one. That is, the preferred shape for our bovine female is somewhat like a white wine bottle – long and slender with ample neck extension. The red wine bottle is something akin to the preferred shape of a bovine male, thicker bodied with muscle able to be carried right along the top line into the chine (top of the shoulder) region. Note the neck of the red wine bottle is long and slender. The port, Tia Maria, baileys bottles are to be guarded against, too thick, too short in the body and very little neck extension. Shape isn’t all that easy to measure objectively, it is a trait like structure that will require experience and ‘cattle sense’ in order that it be correctly identified.
3. Birth Weight
How important is birth weight to the live calf equation? There are at least six factors some already discussed, contributing to the live calf born e.g. heifer/cow management during gestation, calf shape, pelvic area, gestation length, the combined contributions of the bull and female to calve easily.
As bull breeders Sal and I have been terribly frustrated, particularly over the last ten years by the obsession of the beef breeding industry toward birth weight. It seems nothing else (other than birth weight) matters in the industries quest to ensure maximum live calves born.
It is important to get the contribution and particularly the genetic contribution of birth weight into perspective. Cundiff and Gerard attribute 35 to 40% of the expression of birth weight to the genetic-make-up. Gregory Davies (Genetic solutions0 has searched the literature and reports the herability for calving ease that is, live calves born is 15%. The logic therefore suggests the genetic contribution of birth weight to live calves born is 35% of 15% or 5.25%. Therefore, just as fertility is lowly heritable and infertility highly heritable, then so too live calves delivered is lowly heritable and calving problem issues highly heritable. That is a young bull calf assisted at birth mated to a heifer assisted at birth will almost certainly produce offspring that have to be assisted. What does all this mean? As a cow calf operator know that the bulls you purchase haven’t been assisted at birth and if you do have to assist heifers or cows calve then be sure to cull the heifer/cows so they cannot re-breed. Cull the heifer calves that have to be pulled.
Birth Weight EBV’s
Significant progress toward reducing dystokia has been made since the introduction of birth weight EBV’s. The birth weight EBV’s have also reinforced the linkage of birth weight to growth rate. That is, heavier calves have greater survival rates and grow faster; conversely lighter calves have lesser survival rates and grow more slowly. Where are the boundaries? How heavy is too heavy? How light is too light?
Prior to attempting to set some boundaries for the selection process for birth weight please remember that the EBV for the trait, is attempting to define the ‘genetic contribution’ of the individual for the trait. The genetic contribution is in the order of 35-40% meaning that the environmental /management contribution is in the order of 60-65%. The breed plan model attempts to remove the environmental effect and to this end uses the measured performance of the individual plus its ancestors. Individuals with the same genetic capacity/code for the birth weight trait can have significantly higher or lower birth weights depending on how the heifer/cow is managed during the gestation. This is why ‘raw’ data can be misleading depending on how it is used. Currently the ‘average’ birth weight EBV for animals born in 2003 is +4.1. It is therefore wise to use heifer bulls with EBV ranges of +3.5 to+5.5 and cows are capable of supporting bulls with EBV’s for the trait of +5.0 to +7.0. When using bulls at the ‘top end’ of these recommended ranges be sure to have considered the other contributors to live calves born listed and discussed here in. It’s important to re-visit the heifer bull theories of using very light birth weight sires. This because light birth weight is correlated to lower growth rates and as a rule the heifer component of the most self replacing herds is going to contribute 10-12.5% of the potential calf crop. In addition heifer calves from the heifer portion of the herd will be retained as future breeders. If these heifers haven’t grown sufficiently then their pelvis etc won’t have developed to the point where it will not restrict normal calf delivery. Keep the balance don’t push the extremes this is why it is important not to use too heavy a birth weight fundamentally too many calves will simply be too big. It is certainly tempting at times to use those extremes growth bulls, they usually also have expressive muscle in an effort to maximize growth and therefore profitability just remember the Butterfield quote when being tempted “Dead calves have distressingly poor growth rates.”
4. Gestation Length
It is not uncommon for the fetus to be growing at rates of between 0.65 to 0.7Kg per day during the last three weeks of gestation. Therefore calves born 4 days ‘earlier’ than the average can be almost 3Kgs lighter. 3Kgs in an average birth weight of 36Kg is significant it represents 8% of the birth weight.
Including gestation length in the set of criteria top assist improve live calf born performance is a must. To date a number of son’s grandsons and great grandsons we have used of VDAR New Trend 315 a highly maternal sire who is -3.9 days for gestation length, one of his more pre-potent grandsons PARB Design Plus 97 is -4.7 days for gestation length Rockn’D Ambush is -3.6 days. Perhaps one of the most successful live calves born sires we have used to date is Dulverton Texas T15, he has been used by Gary McDonall who reports the same outcomes, T15 is -4.1 for gestation length, interestingly his daughters are amongst the easiest calvers we see, they are also above average growth.
5. Ability of Sire to Produce Daughters Who Calve Easily
There is no doubt that good measurement and accurate records provides more and more insight into the complete picture regarding maximizing the number of live calves born. One such record is the ability of sires to produce daughters who calve easily. Some sires we have been able to identify include Five Star Valour V2 (a bull we share with John and Selena Sylvester), O’Neill’s Crusader, O’Neill’s Renovator, RocknD’Ambush, Dulverton Texas T15, RRScotchcap 9440.
There is no doubt live calves born is a complex issue, there are no ‘silver bullet’ answers in fact there are at least five contributing factors to be considered when analyzing the problem. As with all livestock performance related traits, there is a genetic and an environmental component that needs to be managed.
Some tips to help include:
- Understand feotal growth
- Grow heifers evenly and adequately through the pregnancy
- Never use bulls or heifers that were assisted at birth as future breeders
- Include birth weight, gestation length and calving ease of daughters in your selection criteria.
Good Luck
Greg Chappell