Are our Cows getting too big?

Over the course of Nephew Sam’s wedding 24/04/2021, I was approached by a guest enquiring  “Are our Cows too big?” We did have a reasonably long and “in depth” conversation, for a wedding at least, re this Topic.
Might I say Sal and I have been wrestling with this same Issue for the past three /four years, it would appear it’s a debate in the Industry at large as well as the Angus Breed needs to have. You might recall Angus Australia’s Technical Team recently re- configured the Heavy Grain Index by including a weighting for Mature Cow Weight amongst other weighting changes. The “New Index” wasn’t well received and so the Old was re-instated, Change is in the offing.

Prior to launching into a discussion re the above topic, let’s investigate where the Angus Breed specifically has come from since the 1970’s.
My involvement with Angus dates back to the early 1970’s at that time the Angus Breed as I recall fulfilled two roles-:
1) Providing a source of “Heifer Bulls” to the industry at large
2) Providing the Butcher Trade with ideal Eating Quality carcases that fulfilled the Butchers Beef Yield requirements *Minimum Bone *Adequate Muscle *Appropriate surface Fat Cover. These Carcases were very light 150-170kg, coming from live “Vealers” no heavier than 300kg.
The Breed back then was widely applauded as having-:
1) Super Fertility
2) Great Foraging Capabilities
3) Ideal Calving Ease
4) Dark Skin Pigment
5) Major Milk producing capability providing finished Vealers
6) Played a role in producing the Black Baldie Cow.
7) The Polled Character
On the negative side of the ledger the breed was seen as having-:
1) Insufficient Growth
2) Major Temperament Issues
It was these two negatives, Growth in particular, that had kept the Angus Breed in the doldrums for so long.
It was during the 1970’s that Growth,  “Lean” growth  in particular became an industry wide focus. Two events-:
  *The ABCAM/ABCAS Carcass Judging systems
  *The Importation of Semen from Europe of the Charolais, Simmental etc Breeds
Considerably promoted the “Lean” Growth phenomenon.

The late 1970’s and the 1980’s witnessed a change in those investing in Australian processing from that of mainly the British to that of the Americans and Japanese. With this investment came a growth of the Feedlot industry and in the case of the Japanese a specification that stipulated a days on feed requirement of 150 to 300 days. These Specs also had Marble Score requirements of Aus-Meat 2 (150 days) and Aus-Meat 3+ (300 days) with a Carcase Weight of 380kg’s +( today that requirement is 420kg+). Some company specification included a breed requirement, that being for Angus.
The stimulus was now present, the Australian Industry had to increase its ability to supply cattle on Feed that could withstand 150 to 300 day feeding intervals and produce Marble Score 2 & 3+ bodies with adequate rather than gross fatness.

The 1980’s was an exciting decade for Angus with the Market specifications starting to drive significant changes. Angus witnessing significant increases in Frame and Lean Growth outcomes per favour of Live and Semen/Embryo imports from North America.

During the 1990’s and through the first two decades of the new Millennium, the lean growth selection process was consolidated. A suite of EBV’s including Growth, Fatness, Muscling and IMF% have assisted progress toward fulfilling the Carcase specifications of the era. It would seem the Methodology for evaluating genetic make-up and the Trait list to focus more on Profitable Productive Efficiency needs updating, another fascinating topic yet very relevant to the Issue “How Big Is Too Big”.

Angus have undergone a major transformation over the past fifty years both in Popularity and Mature Size.
Commercial Angus Cows on the New England in the 1970’s would have them in the weight range of 450 to 480kg. Today these same cows are in the weight bracket of 550- 620kg, over the same period mature Bulls have increased from 700-750kg to 900-1,000kg.
These are significant increases in mature size yet quite justified considering the fact that the starting point was so low and that the increase has had to happen such that Angus could fulfil the Japanese Market 300 day Grainfed Carcase requirement of 420-440kg. There aren’t many cows with a mature weight of 480kg capable of producing a 420kg Carcase at 32 months. Note the other Grainfed Carcase weights such as E.U.etc are in the weight range of 300 to 350kg, these cattle are needing similar “Lean Growth” and marbling gene compliments. They are fed shorter intervals and so gain at a better rate, are leaner and therefore their “cut-out” yields are significantly better than those fed the 300 days to a Carcase endpoint of 420+kg.

O.K., Cows are now larger than they were forty and fifty years ago, no argument. Mature cow size increase is an issue, larger cows eat moire feed to-:
          1) cope with increased Body Maintenance requirements
          2) enable them to continue growing through to maturity, 4/5 year old
          3) get them to Cycle
          4) maintain the pregnancy
          5) produce milk
Than smaller cows.

On the flip side, larger cows produce calves with-:
           1) faster growth rates meaning they are worth more at the Weaner Sales.
           2) the ability to reach prescribed Carcase weight endpoints Leaner
           3) a greater residual Carcase value at the completion of their productive lives.
In essence larger cows eat more to maintain their productivity, a major issue on the New England in August and September.

Hopefully I have established that there is a need for Angus cows to have sufficient Frame/Body Mass to supply the Market specifications outlined, not forgetting that it is these Market requirements that have been responsible for the unprecedented growth in Angus numbers over the past 50 years. Yet with this increase in Frame /Body Mass comes a corresponding increase in cow feed requirements-somewhat of a Dilemma!
Solving the dilemma is possible.
However applying pressure on Mature Cow Weight so as to make cows smaller doesn’t appear to be the way to go as this downward pressure will only reduce the Productive Capabilities of the Cow Herd. Smaller Cows mature earlier and will fatten at lighter weights a trait they will pass onto their progeny, these progeny will have lesser growth rates at Feed and will be grossly over fat particularly over 300 day Feeds.

The question then becomes-:
“Is it possible to maintain Cow Weights in the vicinity of 560-600kg and so remain Productively Profitable, while not substantially increasing The Feed Budget?”

The most appropriate measure to achieve the Target of Maintaining a cow with the capabilities of producing the progeny with the necessary growth rates to fulfil the 400KG Carcase weights is,

The concept being to maintain that flexible 560kg+ cow who is capable of consuming the same as a 500kg cow while maintaining the same levels of Productive Profitability. Feed Efficiency is a trait Angus to their credit have been measuring for quite some time now.
There are huge Genetic Gains yet to be made re the improvement of this all important Value Determining Trait
Prior to us being able to select for Feed Efficiency Sal and I had been selecting for Slightly negative Fatness, mainly to assist our progeny pass on reasonable Beef Yield traits and now, as it turns out, this practise has ensured the Dulverton herd does perform reasonably well for the all important Value Determining Trait FEED EFFICIENCY.
At Dulverton we have embarked on utilising the Neogen/Igenity Genomically enhanced suite of Traits primarily to be able to utilise their-:
               1) Stayability
               2) RFI Residual Feed Intake
               3) Tenderness
               4) Carcase measured marbling Traits.
At Dulverton we are happy to be relying more and more on the above list of Igenity Beef Traits as-:
               1) they aren’t available on Breedplan
               2) they are generated from a reference population encompassing seven breeds, the data set is seen as Bovine Taurus. This is especially important to us as it’s our contention that Angus is performing Sub-Par for both Feed Efficiency and Stayability/Longevity.
The 120 Two Year Old Angus Sale Bulls evaluated for the Igenity Beef suite of Traits have averaged 6.6 for the RFI Trait, the same as the 50 females tested for the recent Dulverton Female production Sale.
RFI is an indicator of Feed Efficiency. It is the difference in animals’ daily feed consumption to achieve the same level of daily gain. Lower RFI indicates greater feed Efficiency. The 6.6 value the 120 Dulverton Sale Bulls averaged for RFI equates to the Mr. Average bull having had to consume 0.56kgs more per day to achieve the same level of Daily Gain. The Dulverton goal is to reduce that 6.6 Value to 4.5 meaning that same Mr. Average bull would only have to consume 0.2kgs additional feed to achieve the same level of gain.
By selecting females with lower RFI and higher daily gain, efficiency of maintenance and daily gain will be improved

> It would appear that selecting for Positive Fatness won’t help improve genetic performance for the Feed Efficiency Trait. Indications are that the Traits are negatively correlated. This makes sense as it takes 2.25 as much ENERGY, which has to come from feed in the paddock, to produce a unit of Muscle/Bone as it does a unit of Fat. Further, surplus Fat will impact negatively on Fertility and Milking ability. In addition, Surplus Fat will tend to be associated with Earlier Maturity which will not only impact negatively on Beef Yield but will reduce Mature Size to the point where cows will again struggle to fulfil the goal of producing steer progeny to reach those 400kg+ Carcase weights with adequate rather than gross fat cover.

Over the years we have worked to simplify the processes that impact on total herd productivity, the Reproductive/Calving pathway one of those. Consider the following
Heifer Joining
Heifers are bred (A.I’d) during the 1st week of October. To be exposed each individual  must weigh 320kg, mop up bulls run with heifers for 6 weeks including the A.I. Date.
These heifers are pregnancy tested in early January, the empties are prepared for sale to slaughter.
Two Year Old First Calving
In calf Heifers are grown along such that each individual achieves a Body Weight of 460kg by mid July at time of first calving. Any heifer having trouble calving is disposed of so too the calf if it were assisted. The 460kg target ensures the heifer is well enough developed in the pelvis to be able to calve, very adequate nutrition at calving is essential,  provides energy for the heifer during the act of calving.
By the time these two year olds reach maturity (four/five year old) they will have reached that preferred mature cow weight target of 560-600kg.
James Bradford Guthrie Centre Iowa in the early 1970’s has been quoted as saying
“Allow Fertility to be the Governor of Growth”. How succinct and simple. I guess what James is saying is moderate your growth by establishing your pregnancy rate goals, should those pregnancy rates drop below acceptable levels for no other reason then moderate growth put downward pressure on growth whilst watching those Market Signals e.g. Carcase Weight.

Production Pathways such as the one outlined above do provide for an Environmental/Management process re controlling outcomes for important Performance events. Importantly there is also a need to evaluate such events Genetically. Stayability is an extremely important Trait to be included in any Breeding enterprise particularly where questions such as that being posed, “How Big is Too Big”need answering.
What is Stayability?
The chance a heifer will remain in the herd as a Productive Cow until at least Six years of age. A higher value is desired.
There are a number of components that interact in producing the expression of this trait-:
                  1) Fertility. Cull the “Empties” Fertility is not all that highly Heritable but Infertility definitely is!
                  2) Ability to rear a Profitable Weaner
                  3) Coping Mechanisms e.g. cows must Cope with Worm Burdens, Buffalo Flies, seasonally induced Stressors e.g. extreme cold, limited winter nutrition Eye irritations Blight (Pinkeye) etc.
                  4) Structural Soundness including “Doability” not necessarily “Fatness” but rather the Body indicators of-:
                   *Capacity, *Soft Pliable Skin, *Silky Slick Hair, *Deep, wide chest floor etc.
Angus can certainly make inroads into improving the Stability Longevity Trait. At Dulverton we have long held the belief that we should be supplying our Clients with Bulls that will last 4 Breeding seasons and not 2.3 Seasons which is currently the case.
Genetic pressure on this trait Stayability will not only assist “Cap” mature cow size/weight but also provide for better Structure and coping mechanisms amongst bulls enabling them to fulfil working careers of at least four years.

Thanks to the guest at Sam and Ally’s wedding for posing the Question. It has been a timely reminder to The Dulverton Team as we progress toward our 2021 Bull Season.
My take home message
   “If your Cows are getting to be in excess of 620kg then they may well be getting Too Big”
    To keep a lid on their Mature size try utilising Feed Efficiency and Stayability/Longevity data. Putting downward selection pressure on Mature Cow Size and positive pressure on Fatness will result in reduced Profitable Productivity. The Production Pathway outlined will assist not only reduce dystokia re Heifers not being properly developed to calve, but will also keep downward pressure on Mature Cow frame Size the two year old only needs be 460kg at calving.

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