By Tim Barnes
The next time you are on the internet, google “Barnyard Blindness”. What did you find? My experience has been there is no good answer. It offers you sites for blind horses and barnyard festivals!
In an old Drovers Journal article, the author states: “The definition of BARNYARD BLINDNESS is when everybody thinks that their critter is better than anyone else’s, but the real meaning is when a breeder cannot see the animals shortcomings and therefore, continues to produce subpar offspring.”
Daily, as I feed and water (garden hose – no automatic fountain), I observe the groups of our lambs, ewes, and rams. Making sure all are up and about but also evaluating (in my mind) just how good they are in the big picture of the Shropshire & Tunis worlds. I personally think I get a much more optimistic opinion in the morning than in the evening. I do not know why, but I would guess the freshness of the new day is verified by the calm of the animals in the barn. By evenings all those little problems start to add up, a hanger is broken on a feeder, ewe 1725 is limping, lamb 1840 is coughing, a light bulb is burnt out, etc. So, I continually try to balance the good with the bad and never make big sheep decisions in the evening.
So how good are my sheep??? How can I compare them to the other flocks? Let me say right here and now! I have used EPDs and benchmarks for years in the swine industry and firmly believe they are an invaluable resource for herd improvement. But the show sheep industry currently places little/no value in this type of data, so each of us must develop our own system to evaluate our sheep.
You can establish a baseline for your flock by visiting other breeders. I am not sure why my mind works this way, but when I visit other flocks, I am always impressed with their sheep for the first few minutes. My mind thinks their sheep are bigger, thicker, sounder, and longer. But then reality and experience set in and my mind starts to calibrate the surroundings. Soon after, I start to focus on the priority traits I am looking for, and then establish a balance between my sheep and the host flock. Years ago in Oklahoma a breeder told me you can have your pick of my ewe lambs. REALLY! My problem was there were 150 head in a 100 acre pasture! Needless to say that visit was a real eye opener! Be flexible and ready for many new experiences on a farm visit!
FAT SELLS, FAT SELLS, FAT SELLS!!! Learn quickly the difference between fat and muscle. There are meat science videos, live sheep judging videos, feed management videos, and old experienced shepherds who can help you evaluate muscle and fat. The vast majority of sheep judges today are profile judges (they place the animals from the side view), thus fat makes a narrow animal wide, a shallow animal deep and a small animal massive.
We are all BARNYARD BLIND to a certain degree. We raise the type of sheep we like to look at. The great breeders know a good one whether they are skinny or fat. Embrace the challenge of breeding better sheep. Learn, live, look and enjoy each moment in the barn. Remember ”BARNYARD BLINDNESS” is a curable problem!
Dewormers – Are They An Extremely Valuable Non-Renewable Resources? April 25 2018
– Michelle Arnold, DVM (Ruminant Extension Veterinarian, UKVDL), University of Kentucky
A “non-renewable” resource is a resource with economic value that cannot be readily replaced on a level equal to its consumption. Petroleum and coal are two familiar examples of valuable non-renewable products used daily but known to exist in limited supply, and formation of new product takes billions of years. Dewormers, on the other hand, are products that can be purchased from almost any farm or veterinary supply store and online. There are many different kinds, fairly inexpensive, and seemingly effective at killing parasites in the digestive tract of cattle and certain types also control flies, ticks and lice. They come in many forms and can be delivered to cattle by mouth as a liquid, paste or in block form, by injection, or simply by pouring it down the topline. Given this situation, how could dewormers ever be classified as “extremely valuable non-renewable resources”? In a recent veterinary continuing education meeting at the UKVDL, Dr. Ray Kaplan, an internationally-known veterinary parasitologist from the University of Georgia, used that very phrase to describe the dewormers used every day in cattle operations.
Dr. Kaplan is considered a leading expert on the rapidly developing problem of “anthelmintic resistance” which means the dewormers available are losing their effectiveness in the field with no new products on the horizon to take their place. He explained that although new drug “classes” entered the market every decade from the 1950s to the 1980s, it has now been over 30 years since ivermectin was introduced in 1981. Basically ‘we have what we have’ which is 3 major chemical classes or families of dewormers known as the Benzimidazoles (SafeGuard®/Valbazen®/Synanthic®), the Macrocyclic Lactones (Ivomec®/ Cydectin®/ Eprinex® & LongRange®/Dectomax®) and the Imidazothiazoles/ Tetrahydropyrimidines (Rumatel®/ Strongid®/ Prohibit® or Levasol®). “Resistance” is the term used for the ability of a parasite to survive after treatment with a dewormer given at the right dose, at the right time and in the right species. What was once a sheep and goat problem is now a growing cattle concern. The first case in US cattle was reported in 2004 and serious problems are now recognized worldwide. Resistance is most common in Cooperia, but increasingly reported in Haemonchus, Ostertagia and Oesophagostomum. Resistance to chemical dewormers is caused by a slow buildup of “resistance genes” in parasites from repeated drug treatment over many years. These genes accumulate undetected over time until the point when so many resistant worms survive there is an obvious treatment failure. Resistant worms are not more aggressive or deadly but they simply survive in high numbers after deworming, causing disease. So why, if livestock has been raised for hundreds of years and dewormers have only been around for the last 50 of those, are such dramatic effects seen if drugs fail? Unfortunately, this reliance on chemical deworming has allowed selection of bulls and replacement females with high production numbers but ignored their genetic inability to resist parasite issues. As Dr. Kaplan explained, we have developed “wimpy” animals when it comes to fighting parasites. Additionally, chemical deworming has allowed neglect of husbandry and pasture management factors that keep worm burdens naturally low. For example, overstocking a pasture means more feces, more worm eggs and larvae after egg hatching, shorter grass and more parasites in animals. This is a management problem and not the fault of the animal or the dewormer.
Parasites are a normal part of the ecosystem and it is also normal for grazing animals to be infected with parasites. “Infection” in this sense means there are worms in the digestive tract and is not the same thing as “disease”. In cattle, “clinical disease” from parasites includes signs of diarrhea, anorexia (“off feed”), rough hair coat and, depending on the parasites involved, anemia (low number of red blood cells) and hypoproteinemia (low blood protein). However, the bigger concern is often “subclinical disease” where there are no overt signs of a problem yet there is actually decreased intake and decreased nutrient utilization resulting in severe reductions in weight gain. Most animals develop good protective immunity from parasites but this can only happen if the immune system gets stimulated by worms inside the animal (similar to how a vaccine works). Development of immunity to parasites largely depends on age of the animal. Calves under a year of age have poor immunity so clinical disease is possible and production losses are certain from Cooperia and Ostertagia without proper control. Two-year olds have moderate immunity so clinical disease is less of a problem but production losses likely without good control as more Ostertagia (the brown stomach worm) are active in this age group. Three-year olds and above have good immunity with little clinical disease and only slight production losses from parasites. This immunity can be maintained throughout their productive lifespan as long as nutrition is satisfactory. Those without good immunity formed early in life are at higher risk for disease. “Premunition” is the term used for this immunity that is stimulated by a resident population of worms and actually restricts the establishment of new worms. Treatment too often in young animals removes worms and eliminates the state of premunition.
How is it possible to know if dewormer resistance is a problem in a herd? The best way to test is a Fecal Egg Count Reduction Test (FECRT) based on the premise that dead worms don’t lay eggs. Fecal samples are taken from 20 animals before deworming then the same 20 are re-sampled in 2-3 weeks (depending on which dewormer was used). The number of parasite eggs should be reduced by >95% between pre- and post- treatment samples. If <90% reduction, resistance to that family of dewormers is certain. The test is best run in weaned animals under 16 months old and is not as reliable in adult cattle. Once parasites become resistant to a drug family, they never go back to being susceptible. For this reason, it is wise to do a FECRT on any newly purchased/leased breeding stock to avoid contamination of the farm with resistant parasites before allowing them to mix with the rest of the herd.
How can we slow the development of resistance to dewormers? Reducing unnecessary treatment with dewormers, making sure the dewormers used are effective, and strategic culling all contribute to fewer resistant genes in parasites. The following are Dr. Kaplan’s recommendations:
- Reduce treatment frequency and/or modify treatment strategies. In cattle, treat only 80, 90 or 95% of adult population of the herd, leaving heaviest and best-looking untreated. In practical terms, if you deworm twice a year (spring and late summer/early fall), limit the slick, fleshy cows to just one time per year. This leaves a proportion of the worm population untouched by a dewormer (including the worms in untreated animals and also any eggs and larvae on pasture at the time of treatment). Parasitologists refer to this proportion of worms unexposed to the chemical effects of the dewormer as “refugia”. The greater the proportion in refugia (protected or “in refuge” from chemicals), the slower the development of resistance. Unfortunately, the common recommendation for many years has been strategic parasite control by deworming when environmental contamination is at a minimum in the summer. This practice actually promotes resistance because very few worms are in refugia.
- Ensure the treatments we administer are very effective. Given the common state of dewormer resistance, use of drug combinations is essential. Combinations slow resistance because they kill more resistant worms! An example of this is using LongRange® injectable and using a drench dewormer (SafeGuard®/ Valbazen®/Synanthic®) at the same time. The purpose of the second drug is to kill any worms that survived the first drug, resulting in much fewer worms left to reproduce. Conversely, if drugs are underdosed or administered in a manner with reduced bioavailability or absorption, then partially resistant worms are more likely to survive and mate to produce fully resistant worms.
- Culling the “wormiest” animals. The 80/20 Rule is in effect when it comes to parasites in cattle. Approximately 20-30% of animals in the herd have 80% of the parasites. Culling the wormiest-looking animals removes a significant number of parasites and stops the passing of genetic “wimpy-ness to parasites” to their offspring.
In summary, it is impossible to eradicate parasites and, the harder we try, the faster resistance develops. The goal is not to eradicate parasites but to keep them at a level that does not cause detrimental health effects. Reliance on less chemical control and incorporating strategies based on our knowledge of parasites in the pasture (see box below) will help preserve the effectiveness of current dewormers. Viewed this way, dewormers meet the definition of “extremely valuable non-renewable resources.”
Iowa State University, Northwest Research Farms and Allee Demonstration Farm ISRF05-29, 31
Absorbency of Alternative Livestock Bedding Sources
Reggie Voyles, undergraduate research intern
Mark Honeyman, professor
Department of Animal Science
As the demand for niche-marketed meats
increases, so does need for research in this area.
One niche market that is being examined is pork
raised in deep-bedded systems. There is also a
call for alternative bedding materials. Farmproduced
bedding sources such as cornstalks
and various types of straws are commonly used.
However, this study looked at other possible
materials. Products were tested to see if they
could be equal substitutes based on their
absorbency. A ground lumber product and a
ground lumber with drywall product with a ratio
of 8:1 lumber-to-drywall were tested. These
products were produced from demolished
buildings. They had different performance
qualities than wood shavings and were
compared to cornstalks, recycled paper, oat
straw, and triticale straw.
Materials and Methods
The trials were conducted at the Iowa State
University Ag Engineering and Agronomy
Farm, Boone, Iowa. Samples of cornstalks,
recycled paper, oat straw, triticale straw, ground
lumber, and a ground lumber/drywall mixture
were collected. The Taylor Recycling Facility of
Iowa, LLC, donated the two ground lumber
samples. The rest of the samples were collected
from various Iowa State University research
farms. Once the samples were collected, they
were tested for absorbency. The process used
was taken from an article found on the Ministry
of Agriculture and Food of Ontario, Canada’s
website. The steps were:
1. Place 1 lb of the bedding material in one leg
of pantyhose, weighing both the pantyhose
and bedding material.
2. Place the material in a five-gallon pail of
water and leave it completely immersed for
24 hours. Make sure that there is enough
water so that some free water is left after the
24 hours has ended. Covering the pails cuts
down on the chances of water evaporation.
3. Take the bag out of the water and hang it to
drain, but only until it has stopped dripping,
not so long that the sample has started to dry
4. Reweigh the material and calculate the
absorbency factor from the following
Absorbency factor = (weight after
soaking – original weight)/original
Five replications of this process for each of the
six bedding type were completed. Each sample
was soaked in a bucket for 24 hours and then
hung to drip for 75 minutes, the time that it took
for the sample to quit dripping. After it had
finished dripping, the sample was reweighed to
calculate its absorbency factor as a bedding
Results and Discussion
The absorbency means of the five replications
of the six bedding materials are shown in Table
1. The means shown in Table 1 were compared
using the Tukey’s test for mean separation
(P<0.002) with SAS. The data collected show
some differences in the absorbency of the
different bedding materials. There were three
pairs of bedding based on absorbency: a top,
middle, and bottom pair. The greater the
absorbency factor, the more water the material
held. Cornstalks and oat straw each held about
three times their weight of water. The samples
of shredded paper and triticale straw each held
about two times their weight of water, while the
ground lumber and ground lumber/drywall
Iowa State University, Northwest Research Farms and Allee Demonstration Farm ISRF05-29, 31
mixture held only just over their weight of
After knowing their absorbencies, these
different bedding materials can be placed in a
usage schedule. Cornstalks and oat straw have
the higher absorbency, so it is recommended
that corn producers use harvested stalks as
bedding. The shredded paper is an option for
those who are close to a recycling center with an
abundance of this product available. The lumber
products can be used if there is a shortage of
cornstalks or straw or to stretch the available
supply of bedding materials. They also might
make a good base for a bedding pack, because
of their durable structure when wet. The lumber
products absorb just like the others; it just takes
more bedding to absorb the same amount of
The authors gratefully acknowledge the
following people for all of their help and
encouragement throughout this project: Arlie
Penner, Mike Fiscus, Wes Rodgers, and Seth
Schroeder. The project was supported by the
Agronomy/Baker Endowment and the Leopold
Center for Sustainable Agriculture.
Table 1. Mean absorbencies of six bedding types.
Materials Mean absorbency factor
Shredded paper 2.08b
Triticale straw 1.97b
Oat straw 2.86a
Shredded lumber 1.15c
Shredded lumber plus
Means with different superscripts differ (P<.002).
College of Veterinary Medicine DVM Candidates 2019
Hypothermic Lambs: How to defrost before they’re in the freezer
Winter has already been harsh this year, making it only fitting to write about hypothermia in lambs. Even with the best management, this is bound to be an issue for many sheep producers. Hypothermia has many causes and can affect lambs at different ages. In newborn lambs less than five hours old, hypothermia often occurs due to prolonged exposure to cold temperatures.
Difficult or premature births can cause weak lambs which contributes to hypothermia because these lambs do not get up and nurse warm colostrum as readily as lambs that have a normal birth. Poor mothering can also lead to hypothermia if an ewe fails to thoroughly lick her lambs dry or if she abandons a lamb. If the ewe has poor body condition and there was a lack of adequate nutrition during gestation the risk for hypothermia increases as lambs born from these ewes are often weak and colostrum production is decreased.
Hypoglycemia, or low blood sugar, often accompanies hypothermia in newborn lambs because they have not ingested colostrum which is both a source of immunity and glucose. Lambs are born with brown fat that provides an energy source prior to colostrum ingestion but this fat is gone around five hours after birth. Therefore, lambs that have not nursed colostrum within five hours after birth are at a higher risk for hypoglycemia and will need glucose supplementation before warming. Lambs that failed to receive enough good quality colostrum in a timely manner are also at risk of sepsis associated hypothermia which occurs secondary to lack of maternal immunity. Lambs that are septic will not respond to basic hypothermia and hypoglycemia treatment and should be seen by a veterinarian as soon as possible.
Diagnosis of hypothermia in any age lamb is straightforward. The number one clinical sign of hypothermia is a subnormal body temperature of 100°F or less. As a reminder, the normal body temperature of a lamb is 102-103°F. Always have a clean, functioning thermometer on hand to take the body temperature of a lamb at the first suspicion of hypothermia. These lambs are will be very weak and lethargic. In severe cases, they may lack a suckle response and will be unable to hold their head up.
Treatment of hypothermia varies based on the severity and the age of the lamb. A lamb with mild hypothermia, a body temperature of 99-100°F, should first be thoroughly dried off before receiving colostrum via a stomach tube. It is a better option to tube hypothermic lambs since they often lack a suckle response. Giving colostrum via bottle without a suckle reflex may result in aspiration pneumonia and subsequent death of the lamb. Contact your veterinarian or experienced shepherd to learn how to tube a lamb. If warm, fresh colostrum cannot be obtained from the ewe, use a commercially available colostrum replacer. Do not use a colostrum supplement because it does not have a high enough concentration of antibodies as a replacer.
Often these replacers are made for calves but will work well for lambs also. Mixing instructions will be the same for calves and lambs but obviously a lamb does not need as much volume as a calf. A lamb should receive 10% of its body weight in colostrum over at least a few meals during the first six hours of life. Another option is to keep fresh-frozen colostrum on hand. Fresh-frozen
bovine colostrum can be used but try to make sure it comes from a healthy herd since Johnes disease transmission through the milk to lambs is possible. Some producers will choose not to use cow colostrum or ewe colostrum from other flocks due to this risk, so consider retaining fresh-frozen colostrum from your own ewes.
Lambs that are severely hypothermic with a body temperature of less than 99°F require more aggressive treatment. A lamb that is less than five hours old and severely hypothermic needs to be dried and warmed before giving colostrum via stomach tube. Warming can be accomplished using commercially available warming boxes or simply using blankets or towels. It is especially helpful if these materials can be warmed in a dryer prior to use. Another method is to place warm jugs of water or heating pads under the lamb. Do not use a hair dryer to attempt to dry and warm lambs as the high-pressure air will result in evaporative cooling rather than warming.
Lambs that are severely hypothermic and greater than five hours old must receive colostrum first before drying and warming. Lambs more than five hours old do not have any brown fat reserves left. If these lambs are warmed before receiving glucose in the colostrum, they will convulse and likely die. Again, a stomach tube should be used to give colostrum.
However, if the lamb cannot hold its head up, tubing can be a challenge and there is an increased risk for aspiration pneumonia since it is more likely for the tube to enter the trachea and lungs instead of the esophagus and stomach. In this case, Karo corn syrup can be rubbed on the gums of the lamb because absorption of sugar across the gums occurs rapidly. Alternatively, an intraperitoneal glucose injection can be given if the producer is comfortable doing this.
However, inexperienced shepherds should not attempt intraperitoneal injections without instruction from a veterinarian since there can be severe complications with incorrectly injecting any solution into the abdomen of any animal. After these lambs have been given some energy, begin the drying and warming process. It is recommended to tube these lambs again after their body temperature has increased.
Overall, it is important to remember that the best treatment for hypothermia in lambs is prevention. Ensure that lambs are born in clean and dry environments such as a well bedded lambing pen. Knowing when an ewe will lamb will help a producer predict when to move ewes into an appropriate lambing area since most of the time ewes are sheltered in colder environments such as a three-sided shed on pasture. Careful observation of breeding dates and aging fetuses at the time of pregnancy diagnosis will aid in knowing due dates. Neither of these methods are perfect so frequent monitoring for signs of parturition is necessary. The lambing area should also be free from drafts. Heating lamps are a common recommendation but make sure that they are secured to reduce fire risk. Most of the time though, the heat from the dam and her colostrum will be enough for a lamb to maintain body heat if the lamb is born in a well- insulated and appropriately ventilated barn. Wishing everyone the best of luck during this lambing season.
REARING LAMBS ARTIFICIALLY
By Tim Barnes Ohio State University Extension Educator
Within 2 to 4 hours after birth, decide which lambs among those needing assistance should be removed from their mother. Look for the stressed, or small lambs to select for artificial rearing.
It is important that newborn lambs receive colostrum within the first four hours. The best source of colostrum is from the mother but other ewes within the flock provide a high level of immunity.
Provide a warm, dry, draft free area to start lambs.
Use a milk replacer that is 30% fat and 25% protein. Each lamb will consume 20# of replacer.
Lambs will require assistance the first day to teach them to nurse on the device that is used.
Start lambs on distribution device quickly the younger the is the easier they are to start.
Milk replacer is presented to lambs free choice and at room temperature.
There is a Formaldehyde solution available that retards bacteria growth in the milk.
Place a light over the milk replacer feeding device and dry ration feeder.
Remember to vaccine lambs with BoSe at two days of age. At two weeks of age vaccine with Colostridum Perfringen type C & D for over eating.
Place 3-4 lambs in each feeding group. Try to maintain no more than one week age difference in lamb groups.
Provide lambs with high-quality creep feed by two weeks of age. Provide ample fresh water at all times. Do not feed hay until after the lambs are weaned.
Wean lambs at 30 days of age. Remember this is a stress situation for the lambs they will lose some weight until their digestive system adjust to the no-liquid feed source.
So You Want To Show A Market Lamb But Don’t Know Where To Begin?
From: Tim Barnes Ohio State University Extension Educator
The experts say selection and show preparation are a science that will aid in predicting the final product of your sheep. A well-planned feed and exercise program is the foundation for any winning project.
Understanding the project
In order to establish a feed and exercise program, you have to understand the genetics of your lamb, and how to tailor your program.
The type of lamb selected will have a major influence on the results. Select a lamb with structural correctness, muscle, eye appeal, and growth potential.
The best age to select the project lamb is two to three months of age. If the lamb has muscle shape or structural flaws at that age they will have the same problems later in the show season.
Evaluate lambs on the farm in their natural environment and look at the lamb several times before purchasing to evaluate growth potential. Also, check to see if the lamb has been vaccinated for enterotoxemia (overeating disease).
After purchasing the lamb it is time to develop a feeding program. A goal would be to have the lamb weigh 100 pounds 60 days before the first show. This weight is a good place to start managing weight and finish for the show.
Take the show schedule into account and feed accordingly. Your feeding program is the simplest way to manage the lamb’s weight gain.
Remember each lamb is an individual and they do not all grow the same or have the same body composition. With this in mind it is important to feed each lamb individually when they reach 100 pounds.
There are many feed choices but select a base ration in the 14-18 percent protein ration in pellet form. The higher the protein content, the easier it is for the sheep to put on fat. The 16 percent ration works well in terms of growth and muscle building. As the lamb gains weight the protein should be decreased because they need less as the reach their endpoint.
The 60 days before the show the lamb should be fed a protein ration to develop muscle shape and expression and the proper amount of fat.
One month before the first show the natural endpoint should be taken into account. Pounds of feed help determine where the lamb should be. Example if you are feeding 6 pounds a day of an 18 percent protein feed the lamb should gain 1 pound per day and if you cut that back to 3 pounds a day the lamb will gain closer to a half pound per day, so in 30 days the lamb will gain close to 15 pounds.
For inexperienced showman there is no simple conversion in adjusting back fat, it depends on the size of the lamb, the projected stress level (based on environment and movement), the lamb response to feeds and exercise. This is the one area where experience will improve the final results.
Water intake is important and should always remain the same in a feeding program. Before stress period adding electrolytes will help animal hydration issues.
Feeding a nutritionally sound, balanced diet and keeping the lamb blanketed will promote good skin and fleece condition.
Exercise is wise
Exercising lambs is a necessity. The three best options are lamb walker, tracking and/or treadmilling. Just like feeding, a schedule is also critical for exercise. When the lamb reaches 100 pounds the exercise should begin.
Exercise should start 60-90 days before the show. Walker are used during most exercise periods to promote head placement and proper speed of movement while improving endurance. Treadmilling and tracking are used for short time periods ( 3 minutes). Walking for one minute, and then let the sheep stand for one minute. Eventually, work up to walking for an hour. At big shows, classes can take up to an hour to judge. So preparing your sheep to stand and walk for that long is important in showmanship.
There are several regimes to exercise lambs. One example is to exercise every other day throughout the show season, using a walker and then on a track or treadmill during that session. More experienced fitters will alternate tracking and treadmilling from one session to the next.
Consistency is the key
Consistency is the key for a successful feed and exercise program. Set a schedule and stick to it! Drastic changes in the management program will do more harm than good.
Do your homework
Remember every lamb is different and understanding how to tailor your exercise and feeding program to each lamb takes time and experience.
Maintain a relationship with the breeder you purchased you lamb from and inform them of the lamb’s progress they can give you feeding tips.
By putting in the needed work in the time leading up to the show, you can have a successful lamb project. It’s all a matter of understanding the SCIENCE.
Subject matter taken from: The Science of Show Preparation by Jill Johnson
By Tim Barnes Ohio State Extension Marion County
To achieve maximal fertility, rams should be physically examined for reproductive fitness to detect abnormalities that may affect breeding performance. A breeding soundness examination can be completed before breeding season. The scrotum and its contents and the penis and prepuce must be carefully examined. The size and symmetry of both testes and epididymides should be assessed, and both testes should be firmly palpated for consistency and resilience. Semen can be collected and evaluated to check potential sires, particularly in ram lambs. All screening procedures should be done 2-3 weeks before mating to allow management changes if a ram needs to be replaced in the breeding program.
Supplementary feeding of the ram can be started 6 weeks prior to breeding season. High protein rations can increase both testicular size and number of cells in the germinal layers of the testicle, resulting in increased sperm production.
Mating activity may be monitored by using a breeding harness on the ram and changing the color of the crayon color every 14-17 days. When fewer than expected ewes are marked, poor ram libido, insufficient number of rams to breed the flock, or anestrus is suspected. When ewes are serially marked with different colors, conception failure or early embryonic death is possible.
The ram to ewe ratio varies with breed and whether synchronization or induction of estrus has been practiced. For ram effect, the ration should be 1:20; for estrus synchronization, 1:10 to 1:15 (in season); and estrus induction (out of season), 1:15 to 1:17.
Length of ram exposure during the breeding season should be limited to two or three cycles so the lambing period will be shorter and this will optimize lambing management. Excellent fertility can be achieved with a breeding exposure of 35-42 days. Poor fertility indicates an issue with the ram management. Flock movement should be avoided at mating, but normal handling should not affect mating. Because younger ewes have a shorter, less intense estrous period, they are better mated separately from older ewes with experience rams.
MANAGEMENT FACTORS AFFECTING SHEEP FERTILITY
An Arab horse breeder in the early 13th century carried out the first insemination reported,
by trapping stallion semen in wool placed in the vagina of a mare and transferring this to
the vagina of another mare (Heape, 1898). Later, in 1780, an Italian priest and physiologist
named Lazzaro Spallanzani performed artificial insemination with dog semen, and
revolutionised the way scientists thought. Since then, scientist and farmers have striven to
improve this technology, motivated by the benefits that could be achieved. Sheep is one
of the species subsequently linked to this technology and in which many questions still
remain to be resolved to improve fertility. However, the potential impact of this technique
on the genetic progress of sheep is high and further studies are needed to improve its
Artificial insemination programs in sheep are linked to the genetic selection
schemes of the breeds, but it has not been successfully integrated with reproductive
technology on farms as happen in sows or cows. The technical difficulty and weak fertility,
ranged between 15 to 60 % for pregnancy rate, limits its application.
Female associated factors
Management factors associated with artificial insemination in the ewe can modify fertility.
In reproductive planning, intervals between lambings, season, age of ewe, heat stress,
nutrition state or breed are some of the factors which have a great effect on fertility results.
David et al. (2008), using a joint model combining two main traits, one relative to female and
the other relative to the male, reported that the main variation factors of AI success were
relative to non-sex-specific effects and to female effect, suggesting that choosing females to
inseminate might slightly improve the AI results.
Seasonal variations are described as a limiting factor in sheep reproduction. In natural
conditions, seasonality, which is mediated by photoperiod, modifies hormonal balance and
causes seasonal reproductive variations in sheep (Karsch, et al. 1984; Yeates, 1949), giving
rise to a decrease in reproductive activity during long days (anoestrous season).
Photoperiodic information is translated into neuroendocrine changes through variations in
melatonin secretion from the pineal gland (Bittman, et al., 1983). Melatonin, secreted in
pineal gland, triggers variations in the secretion of luteinising hormone-releasing hormone
(GnRH), luteinising hormone (LH) and follicle stimulating hormone (FSH) (Arendt, et al.,
1983, Karsch, et al., 1984). In any case, seasonal changes in reproductive activity are clearly
defined in sheep breeds from high latitudes (>40º)(Pelletier, et al., 1987), where the
differences in daylight duration between short days and long days are more notable.
As in natural mating, season affects fertility after AI, although hormonal treatment is used
to synchronise and induce oestrus. Windsor (1995) reported low cervical AI fertility rates in
non-breeding season in Merino ewes, a shallow seasonal breed. According to this, Anel et al.
(2005) found a season effect on the AI fertility in Churra ewes, which was more important in
cervical than laparoscopic artificial insemination. In cervical AI, semen is deposited in the
external portion of the cervix and the sperm transport is affected by cervical mucus quality.
Theses authors suggest that photoperiod could alter progestagens and so cervical mucus
characteristics, making it scarcer and more viscous. In consequence, sperm transport in the
cervix can be interfered with. It is important to note that seasonality affects the ram
reproductive parameters in the same way and changes in seminal quality during anoestrous
season may decrease the fertility results after AI.
It has been reported than in tropical and sub-tropical areas the local sheep show restricted
sexual activity in the summer months (Marai et al., 2004). Marai et al., 2007 reviewed how
exposure to high ambient temperature causes impairment of reproductive functions in
sheep. The heat effect is aggravated when heat stress is accompanied with high ambient
humidity (Marai et al., 2000, 2004, 2006, 2007). Heat stress evokes a series of drastic changes
in animal biological functions, which include a decrease in feed intake efficiency and use,
disturbances in the metabolism of water, protein, energy and mineral balances, enzymatic
reactions, hormonal secretions and blood metabolites. (Shelton, 2000; Marai et al., 2006). Male associated factors
It has been reported that variation in fertility of ram ejaculates exists independently of the sperm quality (Choudhry,
et al., 1995; Paulenz, et al., 2002). Variations in the fertility of rams have been reported after
cervical inseminations with fresh semen (Anel, et al., 2005; Paulenz, et al., 2002), with frozen
semen (Colas, 1979; Windsor, 1997; Soderquist, et al., 1999; Paulenz, et al., 2005, 2007) and
after laparoscopic inseminations with frozen semen (Eppleston et al., 1986; Maxwell, 1986;
Eppleston, et al., 1991; Eppleston & Maxwell, 1995). In a large scale epidemiological study,
Anel et al. (2005) observed that the male factor significantly influenced fertility. Despite the
restrictions in the choice of ejaculates, the authors found important differences in fertility
among rams. Salamon and Maxwell (1995) proposed that ram differences in fertility could be both genetic and
environmental, whereas ejaculate differences are probably due to nutrition, management
and previous frequency of ejaculation.
Whereas differences in fertility have been demonstrated among fertile males in different
species, the causes of these differences remain unclear (Ostermeier, et al., 2001). Saacke et al.
(1988, 1994) have suggested in bulls that factors associated with semen quality which affect
fertility can be classified as either compensable or non-compensable. It was suggested that
the effects of compensable factors on fertility might be sensitive to the number of sperm
inseminated, whereas those of non-compensable factors were not. As the number of sperm
inseminated increases, fertility increases until a plateau is reached (den Daas, 1992). At this
point, compensable factors no longer have an effect on fertility. Commercial insemination of
ovine in Mediterranean Countries provides at least the plateau number of sperm in an
insemination dose. It is thus the non-compensable factors that contribute most to the fertility
level of a ram. A non-compensable defect in sperm would be one in which a sperm reaches
the fertilisation site and initiates the egg activation process, but fails to sustain zygotic,
embryonic, or foetal development (Ostermeier, et al., 2001). Evidence of such defects in
sperm has been described in bulls with fertility differences (Eid, et al., 1994). Likely
candidates for non-compensable factors would be incorrectly assembled chromatin or
damaged DNA within the sperm nucleus. It seems logical to assume that the transfer of a
complete and intact DNA molecule from sperm to ovum is crucial to obtain fertilisation
with certain prospects of success. It is well-known that the presence of defects in the genetic
material, such as anomalies in chromatin condensation related with the sperm maturation
process, the integrity of the DNA molecule associated with the presence of breaks both of
single and double DNA strands, or the presence of chromosomal anomalies, are closely
associated with infertility (Aravindan, et al., 1997).
Pilar Santolaria, Inmaculada Palacin and Jesús Yániz
Instituto Universitario de Ciencias Ambientales y Departamento de Producción Animal y
Ciencia de los Alimentos. Escuela Politécnica Superior, Huesca
Universidad de Zaragoza
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