Post-calving nutrition determines next year’s success

Management: Your cow's nutritional regime will have a major influence on when and if it gets bred.

Cows need to be on a rising plane of nutrition after calving to conceive and rebreed  on time.

In some areas of Canada this has been a very difficult winter to be a cow-calf producer. With last summer’s drought and the current feed shortage in those areas, many producers are left pondering what to do. Barry Yaremcio, a nutrition specialist with Alberta Agriculture and Forestry, and Murray Feist a beef cattle nutritionist with the Saskatchewan Ministry of Agriculture, have fielded many questions and concerns from producers in the drought-stricken areas on what to do with their feed shortages.

With the impending breeding season, the nutritional regime that your cows are on will have a major influence on when and if your cows get bred. Cows need to be on a rising plane of nutrition following calving for them to conceive and rebreed at the same time each year regardless of pre-calving nutrition.

We found this out many years ago, at the Ag Canada Melfort Research Station in Saskatchewan in a three-year research trial evaluation how different energy levels of pre-calving nutrition could affect future breeding performance. This research was in partnership with Dr. Reuben Mapletoft and Dr. Albert Barth, reproductive physiologists at Western College of Veterinarian Medicine. The objective of this research was to examine the effects of limiting feed intake in the last trimester of pregnancy on the reproductive and calving performance of mature beef cows that were fatter and thinner at the start of the study.

In the first fall, the cow herd was visually assessed and separated at the gate into groups of thinner and fatter cows. These cows remained in the same treatment groups for the three years of the project. Rations were based on a free-choice barley straw diet, supplemented with barley silage and grain. In each group, half of the cows were fed a higher (115 per cent of the then-current NRC) or a lower energy ration (80 per cent of the then-current NRC) pre-calving in the third trimester.

At the end of calving each year (March 14-20), all cows received the same “post-calving” straw base ration supplement with barley silage and grain that was formulated to meet the maintenance requirements of a lactating beef cow with high milk production. This diet was provided until the cows and calves were turned out to pasture in late May to early June, depending on pasture condition. The pairs remained on pasture until the forage available was finished and the calves were then weaned between mid-September and mid-October. The weaned cows then grazed spring-seeded winter cereals until they were returned to their winter treatment pens in early November each year. Cows remained in their winter treatment combination groups for the entire course of the three-year trial. Each year, after the summer and fall grazing, all cows return to their wintering pre-calving treatments at their original starting body weight.

In the fall of the first year there were no significant differences in adjusted weaning weights between groups. Pregnancy check revealed on the first year that the thinner cows fed the lower energy pre-calving ration had 100 per cent conception, while the thinner cows fed the higher energy pre-calving ration had 90 per cent conception. The fatter cows with the higher energy ration were at 92 per cent conception, while the fatter cows fed the lower energy ration had 87 per cent conception.

Calving interval for the fatter cows fed the higher energy ration was 371 days, while the fatter cows with the lower energy ration was 365 days. The thinner cows fed either ration had a 360-day calving interval in the first year calving. By the second and third year of the study all calving intervals were similar but the fatter cows on the lower energy pre-calving ration had twice the number of open cows compared to all the other groups.

Take-home message

Feist goes on to say, “I feel it’s the same story as we have with the vitamin A world shortage. Short-term deficiency may have issues at calving, but body stores will be replenished on pasture. However, if the energy and vitamin deficiencies extend over a period of years, beef producers will have troubles. I don’t want producers to think they can have normal calving and reproductive success on a vitamin-deficient feeding program, and quit feeding it altogether in a false sense of security then have a wreck or troubles next year.

“One thing I do know is if producers continue to feed low-quality straw diets with limited mineral/vitamin supplements we will be seeing more cows and calves diagnosed with a vitamin A deficiency at the veterinary diagnostic lab. So it is extremely important to feed more energy and continue with proper vitamin and mineral supplements after calving and during the breeding season.”

When Barry Yaremcio talks to beef producers who are having difficulties this winter with short feed supplies, he stresses don’t be afraid to feed some grain after calving.

“Feed anywhere from four to eight pounds of grain along with your hay and straw. Feeding hay alone will not provide the increase in energy that will be required post calving for the cows to cycle quickly and rebreed. It will take about 12 weeks for a cow to reach her maximum feed intake after calving. The uterus has to contract and the rumen has to expand over this period in order to have maximum feed intake. Feeding hay and straw only will not allow for enough intake to meet the increased energy requirements of a nursing cow, thus the reason for adding grain. Straw is a high-fibre, low-energy and low-protein ingredient. If possible, minimize or eliminate straw from lactating cow rations. Use of a program such as CowBytes, available from Alberta Agriculture, to balance rations will help eliminate problems.”

If you are concerned about the labour needed to feed a protein energy supplement, then feed every other day. Research at University of Alberta by Ruth Tellier and Dr. Gary Mathison found no measurable negative effect on intake or digestibility on a high straw-based diets when providing protein/energy concentrates every second day. It is recommended that cows be introduced to the higher levels of grain over time.

“In addition, it is extremely important to separate out your two-year-old heifers that have calved and feed them extra,” says Yaremcio. “Heifers are still growing. They are really only at about 85 per cent of their mature body weight. If the heifers remain with the older cows they just can’t compete for the extra feed that they need.”

When cows and calves go to grass this spring, it is important that the grass be at the three-leaf stage before grazing begins. Grazing too soon will affect the production of the pasture over the summer. In addition, if cows go to dormant grass or pasture that was left over from last fall specifically for spring grazing, be aware this dormant grass does not have the energy required for nursing cows. Feed test this dormant grass prior to turning the cows out to graze.

Yaremcio concludes, “Pasture yield in some areas could be in short supply next summer due to the overgrazing or the drought that might have occurred last year. If this is the case, producers should consider very early weaning of their calves or creep feeding them on pasture.”

About the author


Duane McCartney is a retired forage-beef systems research scientist at Lacombe, Alta.



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