|
Frequently Asked Questions (click on question for answers)
|
|
What are the allowable levels in animal feeds? |
|
Spring and summer are times when insects like flies and ticks become a large
problem for cattle, what do you suggest producers do to minimize their
populations?
|
|
For cows with spring-born calves, what type of work needs to be done them and
their calves? Any specific worming or vaccines?
|
|
What about cows who will calve in the fall? What are their needs right now?
|
|
Do you suggest castrating young bulls? When?
|
|
What about nutrition? How does that change from winter to summer?
|
|
What is Reproductive Tract
Scoring? (RTS)
|
|
What are Embryo Transfers? (ET)
|
|
When is the
beginning of cattle breeding season?
|
|
What is the significance of having breeding season during a particular time?
|
|
What is the condition of cattle at the time they go into breeding?
|
|
Additional Information about 48 hour calf removal by Dr. Gary Williams
|
| There are so many choices for breeding - AI, embryo transfer - what can you tell me abut these? Why are these a better choice for some producers? Has the practice increased? |
| Q. Spring and summer are times when insects like flies and ticks become a large problem for cattle, what do you suggest producers do to minimize their populations? |
| Dr. Paschal:
Ranchers can control horn flies (the number one external pest of cattle) using a
variety of methods: sprays (not long lasting but good for immediate control),
concentrated pour-on (good for immediate control plus control for several days
or weeks), ear tags of various compounds (for long lasting control, several
weeks to a few months), self applicators (dust bags, back rubbers, etc) for long
lasting if intermittent control, and insect growth regulators (IGR) in feed or
minerals (must be consumed). Ideally ranchers would try a mixture of methods to control horn flies, an immediate control method (like an inexpensive insecticide pour on or spray) combined with a long lasting method (self applicator, ear tags, IGR feeding, etc). If one doesn't work, then they should try another. The insecticide pour on I refer to here are solely for external parasites, there are several de-wormer products that will control internal parasites (commonly called "stomach worms") as well as external parasites (mainly horn flies). To control ticks, there are a few sprays (whole body spray for hard ticks) and ear sprays (or "bombs" as we used to call them) for the soft bodied ticks found in the ears. There are also several good ear tags for ticks (that will control horn flies as well). Although ticks are not as prevalent as horn flies, the economic damage can be just as great. |
| Q. For cows with spring-born calves, what type of work needs to be done them and their calves? Any specific worming or vaccines? |
| Dr. Paschal:
At the risk of getting cross-wise with local veterinarians who should be the
ranchers first line of defense in disease prevention and cure, I would vaccinate
all of my calves for the "Blackleg" or clostridia diseases (usually called a "7-
or 8-way) around 3 months of age. I would vaccinate my cow herd and my replacements for this disease as well but probably in the fall when have my vet out to pregnancy test my cowherd (and it is a little cooler). The difference between the 7 and 8 way is usually for either tetanus or redwater, neither of which are important to calves but can be to cows. I would castrate commercial bull calves and implant them with a growth implant in their ear (if I have the help and the skill to do both). Realistically, there are a lot of bull calves going to market so a lot of folks either don't know how are don't have the skills to castrate and implant. These bulls will be castrated before going on feed and the losses incurred are passed back to the calf seller with lowered prices for weaned bulls (compared to steers). Right now, we are so short of any calves, this discount, normally $5.00 per hundredweight, is nonexistent. Some might consider de-worming their calves at this point in time, it really depends on weather conditions, the nutritional condition of the cows and pasture conditions. If de-worming is going to be conducted, all cows and calves should be de-wormed and then turned into a clean, rested pasture. Newly de-wormed cattle should not be turned out into the pasture they just came from, they will get re-infested. Although the biggest direct economic benefit from de-worming will be in increased calf weights, the destruction of the adults in the cows keep the entire population under control. Mature, healthy cows can tolerate a fairly large worm burden if they are in good condition and on a good plain of nutrition. There are a number of products offered and come in a variety of forms. Pastes and drenches (orally applied products) tend to be less expensive but require facilities to handle cattle. Pour-ons are more expensive but require less labor and are more forgiving about facilities. There are feed blocks that contain de-wormer that can also be used. There are differences between these products (and forms) and you local veterinarian should be consulted to determine which are best for you. Some folks might also consider implanting their heifers with a calf implant as well. If nutrition remains adequate, research shows their is no effect on reproduction. If that is a concern, then either do not implant any of your heifers (you are intending to keep) or only implant those lighter ones you are definitely not keeping. I would identify my calves with either an ear tag (a plain ear tag is fine, it doesn't have to be an national animal ID RFID tag) that has a number and ranch brand or name (it can be placed on the back). Usually a yellow or white tag with black letters has the best contrast. Some folks might brand their calves at this time (some registered breeds require a fire-branded number) with their ranch brand and/or ID number. If you are branding calves, use a small calf brand (2-3 inches), and let it cool to ash gray before applying it to the hide. Rock it slightly side to side and up and down while pressing firmly. A brand should never be red hot of the hair catch fire when branding... the idea is to permanently ID the animal, not barbeque it! Once I vaccinated my calf, castrated and implanted, treated for internal and external parasites and branded or tagged my calf, I would turn it back to its momma and when all of the calves are "mothered up", I would turn them out to a new, fresh pasture. |
| Q. What about cows who will calve in the fall? What are their needs right now? |
| Dr. Paschal:
I would pregnancy check the cows calving in the fall (if they have been yet),
and vaccinate them for Blackleg, Leptospirois, Vibriosis, and Bovine Respiratory
Disease (use a vaccine safe for pregnant cows). I would control internal and external parasites on and in them. |
| Q. Do you suggest castrating young bulls? When? |
| Dr. Paschal: As early as possible. At birth or at calf working, but not at weaning. The procedure is too stressful and will cost you weight and possibly a dead calf if improperly done. |
| Q. What about nutrition? How does that change from winter to summer? |
| Dr. Paschal: Nutrition recommendations should be based on the stage of production (pregnancy), pasture and weather conditions. Many spring calving herds in South Texas are already getting some form of protein and energy supplementation due to lack of rain fall. Some have de-stocked to avoid feeding. North of here rains have been adequate to supply the necessary nutrients. |
| Q. When is the beginning of cattle breeding season? |
| Dr. Paschal: There really is not a specific time to breed cows; cows are reproductively active all year long. We generally think of "Spring" time (February through May) as the ideal calving season (in fact about 70-75% of all calves born are born in this period, although it is not exactly "Spring") because the forage is re-growing as sunlight and temperatures increase thus providing adequate nutrition to the cow and her calf (through her milk). Having said that, since the gestation length in cows is about 285 days (approximately 9 1/2 months, a few days longer in larger and Bos indicus breeds and a few days shorter in smaller and dairy breeds), then the "ideal" breeding season for Spring born calves is 91/2 months prior to that or beginning in April but for sure by May. In many areas of Southern Texas calves are born in December so the breeding season has already started (in February or March). |
| In Webb
county, about 25 years ago, a county agent by the name of Fred Schuetze
(now the manager of a ranch near Granbury), collected data on weaning
weights of over 10,000 calves born in and around that area. He went and
looked at weaning weights by birth month and for that area (Webb Co. is in
south/southwest Texas) the highest weaning weights were form calves born
in December through February. As a result, many ranchers breed their cows
to calves in that period. One thing is for sure, most folks in Texas try
not to breed too long into the summer, especially further south as heat
stress can keep a bull's interest (libido) and his semen quality low (due
to high temperatures).
|
| Q. What is the significance of having breeding season during a particular time? |
| Dr. Paschal: This plethora of "spring" born calves has a significant effect on the following fall market when these calves are weaned. Early in September the market rises as the demand for feeder calves (weaned calves going either to the feed yard or to grass as stockers) increases. Then sometime in October, mid to late, the demand is overwhelmed by the supply and the prices begin to slip so Spring calves need to be born early and marketed early. By the way, the opposite is true of the 25-30% of calves born at other times (mostly in the fall - September through November), when these calves are weaned there are few feeders available and the prices for these calves are usually very good. However, there is a cost associated with fall calving and that is the extra cost of carrying a "wet" cow (one that is nursing a calf) through the winter. These costs offset any additional increase in price usually. Although a few years ago the mid-west was touting the use of a summer breeding season to get a head start on this Spring market, few in the south are able to take advantage of this due to heat stress on the bulls and pregnant cows. |
| Q. What is the condition of cattle at the time they go into breeding? |
| Dr. Paschal:
Cows should be in a body condition score of at least 5 (no ribs showing)
and heifers should be bred at least 30-60 days before the cows and
hopefully in a body condition score of 6 (some padding over the hooks and
pins - the hips and bones protruding on either side of the tail). Cows are
generally nursing their calves at this time which can be a nutrient drain
if pastures or feedstuffs are in short supply. We don't think cows can be
"flushed", that is fed an energy dense feed to make them think they are in
better body condition than they are and come into heat more quickly (as we
can so with sheep and goats) but there is some data to indicate there may
be a small effect. Also, feeding cows fats or oils has been shown to
increase follicle size and improve pregnancy rates.
There are a few reports that exposure to bulls prior to breeding (for a week or two) may actually improve conception rates by stimulating the cows to come into heat earlier. In an artificial insemination program that also uses estrus synchronization, the late Dr. James Wiltbank (one of the leading reproductive physiologists in the country and the director of the Beeville Station in the 1960's) designed a program that removed the calves from nursing cows for 48 hours immediately after treatment. This helped the cows to come into estrus and whether it was because of reduced nutrient demands, reduced oxytocin (the hormone responsible for milk let down and stimulated by the calf nursing) or some other effect, it was unknown - but it worked! Some 15-25% increase in estrus signs and pregnancy rates were (and have been) observed. It is a highly regarded and used practice today and recommended for AIing nursing cows. I have even seen a response in cows being bred by natural service although it is not as widely practiced due to labor and management difficulties. The problem is that cows with calves that are also in poor body condition tend to be anestrous and we need to stimulate them to achieve estrus, become active again to ovulate and show signs of heat. |
|
Additional Information about 48 hour calf removal by Dr. Gary Williams
1) Historically, 48-h calf removal has always proven highly beneficial in conjunction with estrous syncrhonization and timed artificial insemination protocols. However, the newer protocols involving a combination of drugs (GnRH, prostaglandin-F2-alpha, and an intravaginal progestin (CIDR device) has been yielding outstanding results in English and European cattle in the midwest without calf removal. The jury is still out for Bos indicus-influenced cattle in the south as we are still fine-tuning those protocols for use in those types of cattle. We are currently not getting the results seen in the midwest (e.g., > 55% fixed time AI conception rates), but it may or may not require calf removal in order to solve our problem. We will know more later this year. 2) 48-h calf removal to induce cyclic activity in anestrous cows is of only minimal benefit when not used in conjuction with estrous syncrhonization drugs. In our experience, no more thatn 30% of cows will exhibit estrus and ovulate within 48 h if that is the only thing that is done. Hence, when the calves are replaced at 48 h, all cows that have not ovulated (or are about to ovulate) will lose all of the benefit derived fromt the 2 days of calf removal and remain in the anestrous state. 3) Restricted suckling (1x daily) and early weaning are very helpful tools when cattle are thin or you are in the middle of a drought. Greatest benefits are gained in first calf heifers. |
| Q. There are so many choices for breeding - AI, embryo transfer - what can you tell me abut these? Why are these a better choice for some producers? Has the practice increased? |
| Dr. Paschal:
Artificial insemination (AI)
is just what it sounds like, cows are bred using bull semen that has been
frozen in a .5 ml straw (about the size of a coffee stir stick) and thawed
(usually). This is placed in a metal insemination gun (a hollow tube with
a plunger) and covered with a plastic sleeve (for sanitation). The semen
is collected from bulls, evaluated for quality, has egg yolk (for an
energy source), glycerol (to protect cells from lysine when frozen) and
antibiotics (to prevent disease) added to it. Then the semen is
placed in an automatic machine that loads the straws and prints the breed
code, bull name, registration number and stud code on each tube. Sometimes
the date of processing is also printed. These are slowly cooled to the
temperature of liquid nitrogen (-273 degrees F). They are packaged in
bundles of 5 or 10 straws and and placed in semen tanks for storage and
sale.
The straws are taken from the tank and placed in a warm water bath for about a minute to allow them to thaw (96 degrees F) before insemination. The inseminator (with a long plastic glove or sleeve) inserts their arm into the cows rectum and locates their cervix. The gun is inserted into the cow's vulva and placed in the vagina against the cow's cervix. The inseminator finds the rear (distal) opening or "os" of the cervix and slowly and gently slides the cervix over the insemination gun until the tip of the gun in at the forward () opening of the cervix where it joins with the uterus. At this point the inseminator depresses the plunger slowly and then removes the gun. Really, most folks need to use good bulls (natural service). I have and do AI a lot of cows (and heifers) and although it is a little technical the practice is fairly simply. The problem is time and labor in checking heat (even with synchronization). Only about 80% of the cows (in good condition and with their calves removed, a slightly lower % for heifers) will respond to estrus synchronization. Of these, we will get 60-70% of these bred If we then turn those cows out with good bulls we will get most of the rest of them bred in a shortened breeding season as all of the cows were synchronized and will remain so for a several cycles. In purebred herds, AI is certainly an option and is used but not at a high percentage, probably less than 10%, and closer to 5%. AI is an option for getting really high performing (genetically speaking) bulls that you could not purchase but you can purchase semen on them for a reasonable amount ($10-$50 per straw). Of course there are some breeds chasing single traits like coat color whose semen is in the $100-250 range. I will defer to discussing other topics like ET, the use of the fertility associated antigen (FAA), bull libido scoring and reproductive tract scores to either Dr. Gary Williams in Beeville, or Dr. Bruce Carpenter (ELS in Ft. Stockton and also a reproductive physiologist) |
| Q. What is Reproductive Tract Scoring? (RTS) |
| Dr. Paschal:.
One other reproductive management tool that would be beneficial to
cattlemen trying to breed heifers usually by
A I but could be used
on commercial females (natural service) is reproductive tract scoring (RTS)
and managing the body weight of replacement heifers.
RTS is a scoring system developed in the 1990's at Colorado State University where a rectal examination of the heifer's reproductive tract is conducted to determine her sexual maturity. The scores range from:
Several studies have indicated a 5-20% increase in pregnancy rates of heifers with a RTS of 4 or better, compared to heifers with a RTS of 3. Pregnancy rates of heifers with RTS scores of 4 and 5 were 41 and 58% greater than heifers with an RTS score of 1. Heifers with a RTS of 3, and possibly 2, just need a little more time and nutrition while those with a RTS of 1 are candidates for culling. The best time to score heifers is 30-60 days before breeding. For many years we have been aware that heifers need to reach about 65% of their weight (as mature cows) as long yearlings (15-18 months) in order to get them to reach sexual maturity and begin estus cycling. Sexual maturity is affected by age and weight of the animals. Some current research indicates that 65% might be a little high and that heifers, properly developed, will be puberal and productive at 55% of their body weight. |
| Q. What are Embryo Transfers? (ET) |
| Dr. Paschal: ET "should be" used to propagate the genetics of outstanding or desired sires and dams. ET is basically used to increase the reproduction rate of valuable cows, the rapid multiplication of rare animals, and for export (frozen embryos take up less room and weigh less than cows). The "donor" female (a cow who is genetically superior and will donate her eggs that are fertilized by the semen of a similarly genetically outstanding male) is super ovulated (causing her to release more than one egg at ovulation, as few as 2 to as many as 2 dozen, not all viable). The cow is inseminated and in a few days the eggs are collected (flushed) and graded (for quality). The better quality eggs can be transferred fresh to cows that have been synchronized to come into heat the day of the flush (recipient cows) or they may be frozen (like the semen used in AI). Fresh transferred eggs generally have a much higher pregnancy rate than frozen and implanted eggs (into cows in heat of course). Frozen eggs have a 50% success rate usually. Cost per live calf varies depending on fresh or frozen egg use, who owns the recipient cows. All of the calves born are full siblings (same sire and dam) but are not genetically identical nor will they look or perform the same. The average genetic relationship between full siblings is on 50% (50% of the genes are exactly the same as compared to half siblings where only one parent is shared, the case in most cow herds, where only 25% of the genes are the same). It is still widely used today but not by commercial cattle producers. Many elite purebred herds use ET and many sell the frozen eggs to others as a way to pass along the genetics in a package. |