I remember not too long ago, cow-calf operators in Western Canada calved most cows by mid-March. This century-old tradition allowed cows to nurse their calves and put heavy weaning-weight over the course of the summer and then calves were sold to feedlots by the end of October. This doesn’t seem to be the sole case anymore, since many people have adjusted their calving season to allow cows to give birth on sprouting green pastures in order to take advantage of a friendlier climate and save on winter feeding costs.
Delaying the calving season until May makes sense to me as a beef nutritionist and novice economist. Since mid-gestation cows in the middle of January/February would have lower total nutrient requirements compared to traditional cows in the last trimester of pregnancy/calving.
This would allow producers to overwinter the delayed cow herd on good-quality forages of lower nutrient value as well as provide less energy and protein supplementation. Furthermore, it would also allow better efficiency to increase their plane of nutrition to keep them warm during the coldest winter months. As a result, mid-gestation cows should come out of a typical winter in better body condition (to be better prepared for calving). Producers would save money on their overwintering feeding program.
Consider the potential money savings for a 250-beef cow operation by replacing all the drylot forages and half of the supplemented barley grain in a drylot lactation ration with one month of grazed May pasture. One might assume that cows were delayed one more month in the fall and that grass pastures in the late-spring contain enough forage volume (dry matter basis) to support the cow herd’s general feed intake and contain early vegetative growth of substantial energy and protein value (note: some barley might still be fed on pasture to assure all energy needs are met).
The pencil calculations for potential savings of a late-spring calving season are as follows: Total feed intake of 15 kg = 600 kg x 2.5 per cent of body weight, 15 kg = 14 kg of mixed hay @ $90/mt + 1 kg of barley @ $185/mt. One month winter feed cost = $ 1.26 + $0.19 or $ 1.45 x 30 days. Total monthly feed cost savings (250 cows) = $ 10,875.
In this example, there is a general feed savings on over-winter feed costs, but at the other end of the scale, there might be dire economic consequences to revenue. For example, some Canadian references state there is a difference of about 50 kg less live weaned pounds per calf sold during the traditional autumn months.
Some of this loss of revenue is offset by the marketing of lighter-weight calves at higher prices compared to heavier lower-priced calves. Some studies by the University of Alberta suggest late-spring calves go through a summer period of “catch up” in which they growth faster than winter-born calves, which significantly decreases this disparity. Some producers often retain these light calves and sell them at a later date in later markets or put them into their own background feeding programs.
Aside from the above potential winter-feed savings and general avoidance of calving out the cow herd during arctic-like weather, a late-calving season is not without its natural challenges. Under poor weather conditions calves are at greater risk of pneumonia and diseases such as intestinal scours.
Breeding season affected
By personal experience, one of the first things that come to my mind when producers switch from midwinter to an early-spring calving season in May means that 80 days later their breeding season tends to fall upon the hottest days of the summer in July/August. That means heat-stressed cows are more likely to remain open, because they are less likely to ovulate, have irregular estrus cycles, may have poor conception rates, and suffer from a high rate of early embryonic deaths. Furthermore, a period of “dog days” can literary make otherwise-fertile bulls sterile.
A few years ago, I was called out to a late-spring beef producer’s place (200-cow herd) in southern Manitoba on a +30 C July day. The owner was complaining that a mineral feeding program that I had put together for him was not working, because one of his bulls couldn’t settle a segregated group of 18 Angus replacement heifers.
I was confident that my mineral recommendations were sound and once I saw his bull, which was panting and testicles descended to almost ground level; heat stress had temporarily sterilized him. All of the replacement heifers were laying by the tree-line. In a subsequent visit on a cooler fall day, I discovered the same bull had successfully bred each one of those same heifers with a new calf, which were put in the producers’ fall-calving herd.