IF YOU BUY WEANED HEIFERS, you must feed them through winter before breeding them as yearlings. Weaned heifers can spend fall and winter on pasture with some supplemental feed, or in a pen and be fed hay. (For a discussion of buying heifers, see chapter 3.)
Proper nutrition enables a growing heifer to reach proper growth on time and become sexually mature in advance of when you want her to breed. But heifers should never be overfed to the point of fatness; fat is detrimental to future fertility.
Green grass provides all the nutrients a growing heifer needs, but late-season pasture grass may be mature and dry or covered with snow. Once the grass is past its growing stage, you need to feed hay to meet the heifer’s nutritional needs. If there is still grazeable grass, heifers may need only a part feed of good alfalfa hay to supply the protein and vitamins lacking in the grass. A mix of good grass hay and alfalfa is ideal if there is no pasture for the heifers to graze.
Don’t feed grain unless you are short on good hay. If heifers need grain to grow fast enough to gain proper breeding weight and sexual maturity on schedule, they won’t be profitable cows. You want a heifer that is efficient — growing well, producing good calves without costly pampering.
FIGURING OUT A FEED RATION FOR HEIFERS
Hay is the usual basis for a feed ration if heifers aren’t on pasture. If they eat as much hay as they can, it will meet their requirements. They usually eat 2.2 to 2.4 percent of their body weight daily. If a heifer weighs 700 pounds (318 kg), this is 15.4 pounds (7 kg) of hay. A mix of grass hay and alfalfa usually has enough protein. For best feed consumption, split the ration and feed morning and evening.
If you have no alfalfa, give 0.75 to 1.25 pounds (0.34–0.57 kg) of a protein supplement per heifer per day. Heifers need about 12 to 13 percent protein in the total ration, so choose a supplement (and figure the proper amount of it) to supply this level of protein. Ask your county extension agent or a nutritionist on staff at a cattle feed company to show you how to calculate a proper ration.
A good cow should be able to raise a big calf and breed back on schedule, eating whatever feeds the farm or ranch can produce cheaply — such as grass and hay — and the calves should do well on these feeds also.
Keep your ultimate goal in mind: producing efficient and healthy brood cows. An overly fat heifer isn’t as fertile as she ought to be, and when she does become pregnant she may have calving problems because of fatty deposits in her pelvic area. Also, a fat heifer tires more quickly during labor, which often makes her unable to deliver her calf without help from you.
In some situations you may need to feed grain. Perhaps you don’t have good pasture, and alfalfa hay is expensive this year. If your region is suffering from drought, or you don’t have space to pasture the heifers, or you can’t find good hay at a good price, you can substitute grain for part of the ration. Feed grass hay, a little grain, and a protein supplement. Your county extension agent can help you figure out a proper growing ration for heifers, taking into consideration what feeds are available and affordable, to help heifers reach their breeding weight on schedule without becoming too fat.
With proper feed and management after weaning, heifers can continue to grow well without getting fat. If a heifer weighs 500 to 600 pounds (227–272 kg) at weaning, with the genetic potential to weigh 750 to 800 pounds (340–363 kg) at breeding age (15 months), she must gain 200 to 300 pounds (91–136 kg) in the 160 days between weaning and breeding. She should be able to reach this goal on good hay alone, gaining 1.2 to 1.8 pounds (0.54–0.82 kg) per day or more. Most crossbred heifers get to an ideal weight very easily over winter. But if you have poor hay or a heifer that needs more feed to grow that quickly, you can add a little grain to her ration. Start her very gradually on grain.
Keep close track of how heifers look. Do they seem “full” (well-rounded abdomen, no ribs showing) or “empty” (hollow sides, visible last rib)? Growing heifers should never look empty. Evaluate the growth and fatness of heifers and feed accordingly. Remember that as they grow larger they need more feed. You’ll have to increase the amount several times over winter as they grow. Just be careful not to overfeed.
Understand the effects of rate and growth. The rate at which heifers gain weight the first winter after weaning will have a big influence on their age and weight at puberty, as well as their future reproductive potential. Heifers with a high rate of gain are usually heavier and younger at puberty than heifers not fed well enough to gain adequately. If heifers are small when they start cycling, the conception rate may be poor and there is more chance of embryo death between conception and calving.
ARTIFICIAL FEED SITUATION
Many purebred breeders feed grain to make calves grow faster so they look good at sales. Purebreds bring more money than commercial cattle; they are sold individually by the head, not by the pound. So purebred breeders may feel that they can afford to use grain or buy extra feed to make cattle bigger and fatter more quickly.
This is an artificial situation. The grain-fed bull or young heifer looks good to buyers, but the animal’s appearance is not a true indication of how she would do on natural feeds like grass and hay. The nice fat heifer you bring home from the purebred sale may do poorly on your pasture and actually lose weight or not breed on schedule without the pampering she was accustomed to. And when she calves, her calf may not grow as well as she did unless he, too, is fed grain.
If undernourished, poorly grown heifers do become pregnant and carry the calf to term, they may have problems calving as two-year-olds. A difficult birth can put the calf’s (and heifer’s) life in danger, as well as damage the future reproductive ability of the heifer.
Separate cows and heifers. If you have cows as well as heifers, keep the heifers in a separate pen or pasture. They cannot compete with larger, older, more dominant animals for feed. An older cow eats faster and her larger rumen holds more feed. The heifer’s nutritional requirements — especially for protein and extra energy while growing — are much greater than those of mature cows, so they should always be fed separately.
WEIGHT OF DIFFERENT BREED CROSSES AT PUBERTY
Heifers are assumed to be at least 13 months old. Crosses (X) are from Angus or Hereford cows.
Heifers should be bred at about 15 months of age, to calve the next year as two-year-olds. A heifer can be bred any time after she becomes sexually mature and has regular heat cycles. Most heifers reach puberty by the time they are 12 months old, but some cycle earlier and some start later, especially if they are slow-maturing. You should be able to see some evidence of sexual maturity as heifers grow up: as they start having heat cycles, they mount and “ride” one another.
Heifer fertility (age at puberty and ability to breed and settle soon after reaching puberty) is a combination of nutrition and genetics. Large-framed or slow-growing heifers generally reach puberty later than moderate-sized, fast-maturing individuals. The genetics of sire and dam play a major role in a heifer’s age at puberty and ability to conceive quickly. Fast-growing, early-maturing bulls (which tend to have above-average scrotal size) sire daughters that reach puberty sooner than heifers sired by slow-growing, late-maturing bulls (which often have smaller scrotal circumference). Heifers from early-maturing cows also tend to be more fertile than daughters of late-maturing cows.
The breeder who sells you the heifers should have information on the bull who sired them; that information should include scrotal circumference. (See chapter 14.) There are many advantages to having heifers reach puberty early. The earlier a heifer starts to cycle, the better her chance of becoming pregnant and calving by 24 months of age. Since age at puberty is highly heritable, this is an important trait to select for.
Heifers must be cycling before you put them with a bull or try to breed them by artificial insemination, so they need to reach puberty well ahead of the breeding season. Some heifers show signs of heat before they are mature enough to ovulate; they let other heifers or even a bull mount them but are not yet producing an ovum and have no chance of becoming pregnant. A few observations of heifers riding each other does not mean they have reached full puberty and are ready to breed.
CONCEPTION RATE
The first heat when a heifer reaches puberty may not be as fertile as later heats. Conception rate is about 20 percent greater at third heat than at puberty. Heifers must reach puberty before the breeding season so they’re not being bred at their very first heat.
You don’t want a heifer to calve when she is younger than 2 years of age. Though some heifers reach puberty as early as 6 to 8 months of age, they are not physically large enough to handle pregnancy and calving. But you also don’t want her to breed too late, or she may calve late every year for the rest of her life.
It takes 9 months of gestation to develop the calf after the heifer becomes pregnant. Feed her properly so she can breed and conceive at about 15 months of age. Then she’ll calve at about 24 months of age. Keep a target weight in mind for breeding and calving, to help you feed properly. Heifers should be at least 65 percent of mature body weight by breeding age; British breeds (Hereford, Angus, Shorthorn) should weigh 650 to 700 pounds (295–318 kg) when bred (the lighter weights for Angus), whereas larger-framed Continental breeds or their crosses should weigh at least 750 to 800 pounds (340–363 kg) at breeding. By calving time, as two-year-olds, these same heifers should weigh between 80 and 85 percent of what they will weigh when fully mature, which means well-grown heifers with good flesh but not fat. If a heifer was born in February, she needs to weigh at least 65 percent of her eventual mature weight and be having fertile heat cycles by May of the next year so she can be bred to calve in February of the following year.
The time of year to breed heifers depends on the age of the heifers and what season you want calves to arrive. If you have mild weather you may wish to calve in early spring to take advantage of summer pastures with cows that have large, growing calves. If spring weather is stormy or cold, you may wish to calve after bad weather is past, unless you have a good calving barn and shelter during stormy spring weather. To calve in February, breed during May. To calve in March, breed in June. For April calving, breed in July.
Some folks prefer calves to be born in fall, taking advantage of higher prices for weaned calves in the spring. This idea works if you have mild winters or a lot of good feed for cows nursing calves through winter. The demands of lactation and cold weather require a lot of feed. Others calve in January so calves are bigger by fall or big enough to wean early and sell before the main flood of calves going to market in late fall.
After heifers are bred, they need adequate nutrition to keep growing and to provide for the developing calf. For the first 6 months of pregnancy the growing fetus makes little demand on the mother’s body; she doesn’t need extra nutrition beyond her own needs for growth. Good green pasture will provide all she needs. If a pregnant heifer can graze pasture throughout the summer, this feed will be adequate, as long as she had water and salt, and in many instances, a proper mineral supplement. If it’s a late spring and grass is not grazeable yet, heifers may need hay for a while at the time of breeding until the pastures are ready.
Providing hay. During the fall and winter, or whenever pasture conditions are poor in your geographic region, pregnant heifers need hay as soon as grass is no longer adequate. Part of the ration should be alfalfa, to provide protein needed by the growing heifer and her developing fetus. Most pregnant beef heifers don’t need grain unless weather gets very cold for long periods or hay is not of very good quality.
Pregnant heifers need adequate protein, calcium, trace minerals, and vitamin A during the last trimester when the fetus is growing fastest. If the heifer doesn’t get enough protein, she can’t create good colostrum (first milk) for her calf. Underdeveloped, small calves — from thin mothers — may be too weak to stand up and nurse after birth. Good alfalfa hay during the last trimester of pregnancy ensures a strong, well-developed, healthy calf. If you cannot get good alfalfa hay, substitute a protein and vitamin supplement. A good general rule for feeding pregnant heifers is to feed all the good hay they will clean up — a mix of grass and alfalfa. Grass hay provides most of the roughage (fiber) and nutrients needed, while alfalfa gives the extra protein, calcium, and vitamin A.
In cold weather. If weather gets cold, heifers need more feed to maintain body warmth. If they clean up hay well, increase the amount — especially the grass portion. It creates heat during digestion. If weather is extremely cold, you can feed a little grain to make sure heifers continue to grow. Mature cows do fine in the cold with all the hay they can eat, but sometimes a pregnant heifer — who is still growing — needs a little help.
Cattle can reproduce at any time of year. The cow must recover from calving before she will rebreed, and that recovery period takes about 40 to 60 days. A young heifer will breed at any time of year after becoming sexually mature.
After reaching puberty (or after recovering from calving), the bovine female begins her estrous cycle, coming into heat every 21 days. This is an average; individual cows or heifers may cycle every 18 to 24 days. The complete heat period lasts about 14 hours, but standing heat may be as short as 4 to 8 hours. This heat period is the only time during the 21-day cycle that she will allow a bull to mate with her, and she may accept him only for part of the time she is in heat. The few hours when she will stand still to allow the bull to mount and breed is called “standing heat.”
If she mates but doesn’t conceive, she will be back in heat about 21 days later. This cycle continues until she conceives. After becoming pregnant, heat periods stop (though on rare occasion a cow will have one or two “false heats” after becoming pregnant). She will not mate again until after the calf is born and she has recovered from calving. Sometimes a cow or heifer has a “split cycle” and returns to heat within 8 to 12 days instead of 21 days. This is fairly common; if you are watching heifers for signs of heat, do not be surprised if you see a short cycle.
A cow or heifer can be bred only when in heat. Whether you will be putting a bull with her when she comes into heat or will be having her bred by artificial insemination (AI, the process of a technician placing a capsule of semen into her uterus), you must know when she is in heat.
If she is living by herself with no other cattle near, it can be hard to determine when she is in heat. She may be more restless than usual, pacing the fence or bawling, or have a clear or milky discharge from her vulva. She may have a blood-tinged discharge appearing about 2 to 3 days after she goes out of heat. If you notice this, it’s nothing to worry about (it’s normal), but it also means that she was in heat a few days earlier and you missed it. Not all cows or heifers have obvious signs of heat.
If she’s with other cattle, it’s easier to tell when she comes into heat because they will mount her or she will try to mount them. Hair over her tail head and hips may be ruffled from mounting activity. She may lose patches of hair over her hips and pin bones (on either side of the tail). Bull calves or steers follow her around. She may fight other cattle more than she normally does.
If you plan to breed heifers or cows by AI, spend at least 30 minutes three times a day watching for signs of heat. It’s best to look at the cows at daybreak — before feeding time in the morning if they are on a feeding program — and in the middle of the day and again before dark. Always choose a time when there is nothing else distracting them. If you drive out to the field or pasture in a vehicle, use something different than the feed truck. If they think you might be bringing feed, they will be attracted to it rather than exhibiting in-heat behavior.
The cow’s reproductive tract consists of vulva (external opening), vagina, cervix, uterus, ovary, and oviduct. The cervix (the opening to the uterus) stays tightly closed most of the time and protects the uterus from infection. It seals off completely during pregnancy and opens at the start of labor so the calf can emerge. It also opens during the cow’s heat period when she is ready to mate. An egg emerges from the ovary during ovulation, entering the oviduct (tube between ovary and uterus). Fertilization takes place in the oviduct when the sperm from the bull meets the egg from the ovary. The fertilized egg attaches to the uterus, becomes an embryo and then a fetus, developing into a calf.
If you notice a cow in heat, estimate when you think she came into heat to know when might be the optimum time to breed her. Try to determine if she is just starting to interact with other cattle or has been ridden most of the night, for instance. If you think she came into standing heat after 11 a.m., wait and breed her the next morning unless she is obviously going out of heat by evening. In that case, breed her that evening. (See chapter 14 for a discussion of artificial insemination.)
If she is bred by a bull, he mounts her and finds his proper position, then deposits semen into her reproductive tract, giving a jump as he ejaculates. A cow that has been bred will stand for a moment with her back humped up and tail out after he dismounts. If he mounts her but fails to successfully breed her (without ejaculating semen), she will not show these signs of being bred. If she has been bred, she may hold her tail out for only a short time or for part of a day.
Once semen is deposited, the sperm cells migrate through the uterus and up the oviduct to meet the egg from the cow’s ovary. The egg has been sitting in a follicle on the ovary, waiting to be released during ovulation, which occurs about 24 hours into the heat period. Sperm cells must undergo a 6- to 10-hour period of adjustment to be ready to unite with the egg, so they have to be deposited in the cow’s reproductive tract ahead of ovulation (this is why the cow becomes receptive to the bull and allows him to breed her fairly early in her heat period, before she actually ovulates).
The fertilized egg starts traveling slowly down the oviduct, becoming larger and many-celled. After about six days it reaches the uterus, attaches, and by about the twelfth day becomes an embryo. The embryo stage lasts until about the 45th day of gestation as the major tissues, organs, and systems of the body begin to form. By the end of this period, the species of the embryo is recognizable. The embryo becomes a fetus and begins developing into a calf.
Attachments of fetal membranes enlarge (becoming “buttons” that attach the placenta to the lining of the uterus) to supply nutrition to the developing fetus via the cow’s bloodstream. The fetus increases in size gradually at first, then rapidly during the last 3 months.
Gestation lasts about 285 days. If you know the breeding date for a cow, you can predict within a few days when she will calve. Her “due date” will be approximately 9 months and 7 days from the day she was bred. Most calve within 3 or 4 days of that date, but some are as much as 10 days ahead or 10 days after it. Actual length of pregnancy depends on many factors, including heredity. Some family lines (and some breeds) have slightly shorter or longer gestations, on average, than others. Nutrition, sex of calf, and the weather can also be factors. A falling barometer may trigger labor a day or two ahead of the due date. Bull calves are sometimes carried longer than heifer calves. If a cow goes past her due date, it may mean she’s going to have a bull calf.
Weather stress can trigger labor, resulting in the cow calving a few days early. Any kind of stress raises the cortisol level in the cow, which can induce labor. The calf is usually what triggers labor, however. When he is fully developed for birth, he starts producing cortisol, and this hormone causes the cow to go into labor.
If you have a registered purebred and want to raise purebred calves, you’ll choose a registered bull of her own breed. If your heifers are not registered or are cross bred, it doesn’t matter what breed the bull is; if you want crossbred calves, choose a bull of a different breed from the heifers, or a good crossbred bull.
Streamlined, low-birth-weight bull. This two-year-old bull is being used to breed heifers; he was born very easily himself and will sire calves that will be born easily.
The main thing, for a heifer’s first calf, is a good bull that sires calves that are streamlined or small at birth. Calf size at birth is mainly determined by genetics. If a heifer was large at birth, her calves will probably be large as well. It’s best to keep only those heifers with low to medium birth weights. Then if she is bred to a bull who was small or streamlined at birth (and sires calves with that trait), there is a good chance the calf will have a reasonable birth weight. Do not breed heifers to a bull that sires calves that are large or thickbodied (heavily muscled or thick through shoulders and hips), or you’ll have calving problems.
A calf too large to come through the birth canal, even with pulling by you, must be delivered by caesarean section performed by a vet, cutting through the cow’s abdomen and into the uterus, taking out the calf, and then sewing up the cow. This surgery can be very risky for both cow and calf.
Taking heifers to a breeder. If you have just one or two heifers, you might arrange to take them to a farm or breeder and leave them to be bred. The stockman might put your heifer with a group of his own that are being bred, in a pasture with a bull that sires easily born calves. Or he may put your heifer in a pen next to other cattle so he can observe her for signs of heat, then put a bull with her at the proper time.
Breeding heifers at home. It may be simpler to breed a group of heifers at home. When leasing or borrowing a bull, make sure he’s healthy with no risk of venereal diseases that might be spread to your heifers. (These diseases will be covered in chapter 9.) If an older bull has already been used for breeding, a veterinarian should check him to be sure he is free of diseases that might cause abortion in your cows. The safest choice is to get a young bull that has not yet been used for breeding. Next best is a bull that has only been used on virgin heifers. They are less likely to have any infections that could spread to the bull.
If you purchase, borrow, or lease a bull, disease is less of a risk if he has been used only on heifers. Bulls at most risk are ones that have been breeding a variety of cows — especially purchased cows with unknown background. (See chapter 14 for a discussion on buying a bull.)
You may choose to breed your heifers through artificial insemination (AI). For this you’ll need a chute to restrain the heifer so the AI technician can insert a capsule of semen into her uterus, and you must be able to watch her closely during the time she might come into heat. Talk to the AI technician ahead of time to get advice on what you need to do and to order semen. Mention that you want a bull that sires low birth weight calves. He can show you the bull’s records and help you make the selection.
Several breeding services collect semen from good bulls all across the country to sell to stockmen, purebred breeders, dairymen, and the like. Some beef producers and most dairies use AI so they can breed cows to top-quality bulls located anywhere in the country. If your heifers are purebred, many good bulls in their breed would be available through an AI service. If your heifers are not purebred, you can choose a bull from whatever breed you wish.
The price of semen can vary greatly. Some bulls, especially the champions and popular sires in a breed, are expensive. You don’t need the most expensive semen; any good bull that sires low birth weight, high-quality calves will do.
USING FROZEN SEMEN
A bull used for AI can sire hundreds of calves. The semen he ejects is collected and then divided into many small portions, stored in tubes called straws. These are frozen and stored in liquid nitrogen (−320°F [−196°C]). Frozen semen can be stored almost indefinitely and shipped anywhere. If your AI technician orders semen, he keeps it in a tank of liquid nitrogen until needed. When he breeds your cow or heifer, he thaws a straw of frozen semen for 30 seconds, then inserts it into her uterus.