Calving season sure has changed on the typical western cow-calf operation. Some cow herds start dropping their first calf at the beginning of February, while others have their beef cows freshen well into April, even into May. One thing that hasn’t changed over the years is the need for good nutritional preparation in the crucial six weeks before calving. Getting beef cows on a higher pre-calving nutrition plane will pay off with a larger and healthier calf crop and more profitable cows that can get bred back and pregnant with the next calf crop.
Key to a successful calving season means successfully matching the cow herd feeding program with the increasing nutrient demands of what is going on inside their pregnant bodies that starts to accelerate during the last trimester of gestation.
Up to this point, the growth of the fetus was slow and steady and now weighs about 60 per cent of its final birth weight as a newborn calf. However soon afterwards, this fetal growth dramatically speeds up and along with accumulation of fetal fluids and membranes; adds nearly a half kilo to the cows’ weight daily. At the same time, colostrum (first milk that contains the rich antibodies for the newborn calf) is being manufactured in a bagging udder. Unseen by the naked eye, the cow’s reproductive system is also preparing itself to resume estrus.
Some producers have failed to realize the advantages of a good pre-calving feeding program and have wrongfully limited good nutrition in order to avoid large calf birthweights, which they believe leads to difficult births and pulling calves. Such ideas are not supported by recent university extension research, which clearly proves that any lowering of pre-calving nutrition below essential standards may actually increase calving difficulties among underfed first-calf heifers and thin mature cows. Furthermore such a shortage of nutrition has also been shown to delay estrus after calving and reduces the quality and quantity of colostrum produced by the just-fresh cows for their newborn calves.
Most sound pre-calving feeding programs should maintain or achieve a mature beef cow BCS of 2.5 to 2.75 on a scale of 1 to 5 (thin = 1, and 5 = obese) by calving time, while replacement heifers should calve out a little better BCS of 3.0. Furthermore, optimum BCS should parallel 60 to 70 kg of fetus and fetal membranes weight gain, which is lost on the day the calf is born.
Subsequently, if the number of cows in the herd is large and pens are available, it’s a good idea is to separate and feed the cow herd in at least two groupings: (1) mature cows with a BCS of 2.5 to 3.0 plus obese animals, and (2) thin cows with a BCS of less than 2.5, and most first-calf replacement heifers (except the obese ones). This practice would fulfill our main objective of matching the respective nutrient requirements of all cows during the last trimester of pregnancy as mentioned above.
Dietary energy and protein are going to be a premium of all late-gestation beef cow diets. The mature cow group of a BCS of 2.5 to 2.75 will need a new overwinter diet that contains about 55 to 60 per cent TDN (total digestible nutrients) and about 10 to 11 per cent protein in order to maintain good body condition. Thin beef cows that score 2.0 or less and growing replacement heifers in order to achieve a desired BCS of 2.5 by calving should consume a similar diet, but energy and protein supplied should be increased about 25 and 20 per cent, respectively.
For most producers whose cows calve out in the middle of February until the end of March should also be prepared to account for an energy requirement increase to their cows by 25 to 40 per cent during periods of bitterly cold weather.
A cold weather rule of thumb as follows: for every 1 C drop in temperature below 0 C, the beef cow’s TDN energy maintenance requirements are increased by about two per cent. When the thermometer drops, metabolic triggers in the cow stimulates her feed intake, but they will only increase dry-matter consumption at the very most by 30 per cent; often limited by physical constraints of the rumen and a reversal in feed digestibility. Since pre-calving beef cows can eat only so much feed during very cold weather, it is wise to increase the energy density of their rations by using high-energy and lower fibre feeds.
Luckily, the winter diets of precalving mature beef cows and first-calf replacement heifers (plus thin mature cows) are not particularly difficult to formulate if one has a good forage inventory, which can be easily supplemented with high-energy grain and other feeds. Adequate-quality grass hay or mixed grass-alfalfa mixtures make excellent pre-calving feeds often mixed with a little grain such as barley or grain by products such as distillers’ grains. Similarly, the use of lower-quality forages such as poor-quality hay or cereal straw can be also adequately fed to pre-calving, just as long as their feed intake by beef cows and nutrient limitations are recognized. In these cases, forages should be diluted with better quality forages or an extra compliment of grain or more protein might be needed.
In addition to assuring an adequate supply of energy and protein for pre-calving cows, meeting their mineral and vitamin requirements is also very important. Commercial minerals with complementary levels of calcium and phosphorus to those found in the forages and with good levels of trace minerals (copper, zinc, manganese, cobalt, iodine and selenium) and vitamins A, D, and E should be provided at the rate of 50 to 85 grams per head, daily. Salt and a good source of free choice water should also be included in the feeding program for expecting cows.
With a daily investment of about $1.50 per beef cow (assume most beef cows are about 1,400 lbs. and in adequate body condition), the following pre-calving diets might be put together:
18 lbs. barley straw @ $40/mt, 9 lbs. barley @ $190/mt, 1.5 lbs. 32 per cent beef supplement @ $450/ mt and 3 oz. of commercial 2:1 mineral with salt @ 11c/head/d. = $ 1.50/head/day.
20 lbs. medium quality hay @ $80/mt, 6 lbs. barley @ $190/mt, 0.5 lb. 32 per cent supplement @ $450/ mt and 2.5 oz. of commercial 2:1 mineral with salt @9c/head/d = $ 1.43/head/day.
20 lbs. high quality hay @ $115/ mt, 3 lbs. barley @ $190/mt, 2.5 oz. of commercial 2:1 mineral with salt @ 9c/head/d = $ 1.39/head/day.
The actual feed ingredient prices of these pre-calving diets may vary from farm-to-farm. It is also important to note that substitution of a couple of pounds or more of forages with more pounds of grain in the thin-cow and replacement heifer pens, or to allow for upcoming colder weather is likely to feed costs.
Simple pre-calving feeding programs seem to work the best, and in most cases tend to be the most economical Such workable precalving diets help maintain desirable body condition in mature beef cows, can provide extra growth for replacement heifers or substantially increase weight on thin cows. In this way, making sure that all beef cows are ready for calving, only promotes a better and more profitable calving season.
PeterVittiisanindependentlivestock nutritionistandconsultantbasedinWinnipeg. Toreachhimcall204-254-7497orbyemailat [email protected]