Calving Ease or Calving Difficulty?

By Greg Schulz

What size calf can my Miniature Hereford Cow or Heifer have without difficulty?
There have been many conversations about this subject among many breeders. There have been numerous studies performed on standard size cattle by numerous universities. On the surface this may seem like a very simple question, but the answer is not quite so simple. There are several factors that may affect calving difficulty, some of these include:
-Birth weight of the calf
-Pelvic area of the cow/heifer
-Gestation Length
-Sex of Calf
-Inadequate heifer development
-Body condition of cow/heifer at time of calving
-Abnormal hormone profiles at time of birth
-Abnormal presentation of calf at time of birth.
According to most studies and my own experience birth weight may be the greatest cause for dystocia (calving difficulty). Body condition of the cow or heifer at the time of
calving is another consideration. There are some breeders who believe that by reducing nutrient intake during latter stages of gestation, thus reducing body condition of the cow will result in lower birth weights and less dystocia. Research has shown that while this lowers the birth weight, it does not necessarily reduce the incidents of dystocia, but does result in a weaker cow/heifer, and a weaker calf. Cows and heifers should be in a body condition 5 at calving. Birth weight is a hereditary trait. When looking for
replacement heifers and herd sires you should look beyond just the parents, but look to the grandparents also for birth weights. Just because a given bull or heifer has a low birth weight does not ensure they will pass this trait on to their offspring. However if their parents and grandparents also had low birth weights, then this will increase the accuracy of predicting their ability to pass on the low birth weight trait. There has been some study done on the pelvic area of cows and heifers. It is worth mentioning however that frame size of the animal must be taken into consideration when using pelvic area measurements. Heifers with abnormal pelvic areas should be culled as there is a high degree of probability that these heifers may be subject to dystocia. Heifer development is also crucial for low incidence of dystocia. Heifers should achieve 85% of their mature size by the time they give birth to their first calf. Early maturing heifers should achieve this size by 24 months of age. Slower maturing heifers may not achieve this till they reach 36 months of age.
-Just because a heifer is cycling does not mean she should be bred.
-Just because a heifer can be bred does not mean she should be bred.
There are multiple reasons a heifer may develop early or late. These factors include:
-Genetic potential of the animal.
-Nutrition availability allowing the heifer to grow to her genetic potential.
Some other factors that could be considered when looking to improve calving ease include:
1. Head size of herd bulls and replacement heifers. Smaller heads may improve calving ease.
2. Shape of head of herd bulls and replacement heifers. Heads that are more elongated may provide more calving ease than heads that are wide and short.
3. Neck length. Longer necks that fit smoothly into the shoulders may provide more calving ease than a short-necked wide-shouldered bull or heifer.
So the question once again is: “What size calves are the right size for my Miniature Herefords?” That depends on your cows and heifers.
How to reduce calving difficulty:
1. Breed heifers to calving ease bulls with verified low birth weights in their pedigrees.
2. Develop heifers to prebreeding target weights
3. Ensure that heifers are in good body condition going into the calving season

4. Cull heifers with abnormal pelvic measurements. When you are ready to work on your calving size, the first investment a breeder should invest in is a reliable scale. A good reliable set of scales is an invaluable investment that will help you establish your birth weights, w e a n i n g w e i g h t s , y e a r l i n g weights and the current weights of your cows, etc…

As you select bulls and replacement heifers, you should consider all traits throughout your selection. Single trait selection may hurt your future more than help it. Once
you reach your threshold on birthweights there is not a need to continue looking for smaller birth weights. Your goal should be to have birth weights small enough to reduce dystocia, but still the largest calf your cows and heifers are capable of having. All things being equal, small calves will be smaller at weaning and smaller as yearlings. At Schulz Farm we look for heifers to calve with 40 to 42 pound calves. Our heifers are able to give birth to calves of this size without assistance, these calves hit the ground vigorous, ready to nurse and get busy with life. Our calves are born in pastures without assistance or intervention from people. Our mature cows are capable of giving birth to calves that weigh 50 pounds. Our average for the past two years on mature cows ranging from 000 to 1 frame scores was 47.6 pounds. We have found that the majority of our cows in a body condition 5, are capable of giving birth to calves ranging from 6 to 8% of her body weight:
900 pound cow = 54 to 72 pound calf
850 pound cow = 51 to 68 pound calf
800 pound cow = 48 to 64 pound calf
750 pound cow = 45 to 60 pound calf
700 pound cow = 42 to 56 pound calf
650 pound cow = 39 to 52 pound calf
600 pound cow = 36 to 48 pound calf
550 pound cow = 33 to 44 pound calf
500 pound cow = 30 to 40 pound calf
Your birth weights may differ from ours. If your cows are able to calve with minimal dystocia, then your calving ease is right where you want it. You may not need to reduce your birth weights.
Resources include:
http://www.extension.umn.edu/
http://extension.missouri.edu/
http://www.uaex.edu/
http:// www.uky.edu/
http://www.tamu.edu

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