The Dam's The Thing: Care Of The Pregnant Bitch
The Dam's The Thing: Care Of The Pregnant Bitch
ACVIM 2002 Joni L. Freshman, DVM, MS, DACVIM Colorado Springs, CO
Breeders spend thousands of dollars and hours planning and bringing about an important breeding. A single breeding may be the culmination of years of work and generations of careful pedigree combination. Ensuring a healthy pregnancy is a vital, valuable service. Instituting a routine plan for prebreeding and prenatal care is an excellent way to provide this service.
The diagnosis of pregnancy can be made by palpation, ultrasonography, or radiography. Abdominal palpation for pregnancy is best performed between 21 and 28 days, when the fetal vesicles can be felt like small "golf balls." Tense, obese, and heavily muscled bitches are more difficult to assess.
Ultrasonography can identify fetal vesicles as early as 17 days gestation. More reliable identification of gestational sacs is obtained at 25 to 30 days from the last breeding. Fetal movement and heartbeats can be seen at 28 days gestation. The presence of intestinal gas can interfere with observation of fetal sacs. While sonographic pregnancy diagnosis is 97% accurate at 30 days of gestation, the accuracy for fetal number is only 37%.
Radiography can identify fetal skeletons at 43-45 days of gestation. Due to the potential disparity between days from breeding and gestational age, radiography at or after 50 days from last breeding is recommended to prevent false negative results. Ideally, the bitch will be radiographed with an empty stomach and colon to enhance the ability to observe all fetuses present. Evaluation of both lateral and ventrodorsal views is essential. In most cases, these parameters will allow an accurate count of pups present. Radiography is relatively insensitive in identifying fetal distress, as fetuses must be dead for at least 24 hours before radiographic signs are present.
Ideally the bitch will be well conditioned prior to breeding. Obese bitches should undergo weight reduction prior to breeding to improve conception rate and decrease risks of dystocia and poor lactation. Pregnancy is not a good time to attempt weight loss.
During the first three weeks of gestation the well-conditioned bitch may undergo little or no weight gain. The consumption of a high quality maintenance dog food is sufficient unless the bitch is underweight. Bitches who enter pregnancy excessively thin should eat a growth or performance food to rapidly correct their condition. At about three weeks gestation many bitches suffer a loss of appetite that persists for about a week. Nausea and mild vomiting occasionally accompany the anorexia. Appetite will return at about week four. Occasionally bitches have poor appetites throughout pregnancy. A thorough physical and biochemical evaluation should be performed to rule out any underlying medical problems. If none exist, addition of Worchestershire sauce, or canned food to increase the palatability may increase her appetite. If this is not successful force-feeding may be required. Balls of canned food are placed in the back of the mouth at each feeding.
During the last half of pregnancy, energy requirements increase, as does the need for protein and carbohydrate. This is usually provided by the increased intake of a high quality maintenance ration. Some texts recommend changing the pregnant bitch to a growth formula, however this should not be necessary with a well- conditioned bitch. Alteration of diet may lead to gastrointestinal distress. An underweight bitch or one that is exhibiting a poor appetite would be best served by gradual change to a growth or performance diet.
The amount of food required by a pregnant bitch in later gestation increases in proportion with litter size and growth. A 40% average increase in food consumption accompanies the 20-55% increase in body weight. Due to the increased intra-abdominal pressure from the enlarging uterus, multiple small meals are easiest for the bitch to consume. Bitches carrying large litters may have extreme discomfort the last week of gestation and suffer a decreased appetite again at this time. Many, but not all, bitches will stop eating 24 to 48 hours before parturition.
The administration of additional vitamins and supplements to pregnant bitches should be discouraged. Calcium supplementation, though unfortunately still common, is contraindicated. Although calcium requirements increase in the pregnant bitch, they are met by the increased amount of food ingested. Excess calcium above the amount provided by a high quality diet suppresses parathyroid hormone production and increases the bitch's risk of peurperal hypocalcemia. Breeders should be cautioned not to add calcium in any form to the pregnant bitch's diet. Excess vitamin A has been associated with congenital defects, including cleft palates. Folate deficiencies have been associated with fetal defects in humans. While premium dog foods should contain enough folate, supplementation of B vitamins is not harmful. Dogs produce sufficient vitamin C of their own and do not require supplementation. Excess vitamin D may complicate the calcium mobilization ability of the bitch. Supplementation of Omega 3 fatty acids will maximize cerebral and retinal development in the fetuses.
Fit, well-conditioned bitches are less likely to suffer dystocia. Regular exercise during pregnancy is important to maintain condition. Brisk walking is the safest exercise. In late gestation, bitches carrying large litters may need to limit this to short walks. Performance bitches should stop heavy work during pregnancy; herding, agility, field and advanced obedience work are discouraged due to the risk of abdominal trauma and the potential stress to fetuses. During pregnancy, moderate contractions called contractures occur. They occur approximately every 20 to 120 minutes and last 3 to 15 minutes. They are of low amplitude (5-15mmHg), but do decrease fetal oxygen levels. This in turn stimulates fetal ACTH release. During contractures, the fetus does not breathe or undergo REM sleep. Significant mental or physical stress on the bitch can cause adrenaline secretion by the dam that decreases blood flow to the uterus and placenta. This results in decreased fetal oxygen and can impair development and threaten survival. It behooves the breeder to keep the pregnant bitch's life as stress-free as possible.
Vaccinations for rabies, canine distemper, hepatitis, cornonavirus, parainfluenza and leptospirosis (if indicated in bitch's location) should be current prior to breeding. The puppies' early immunity is dependent upon consumption of colostrum containing high levels of antibodies and therefore upon the bitch's immune status. Vaccine titers in the bitch can be measured to assure appropriate levels are present. Modified live vaccinations should not be given during pregnancy.
Toxocara canis larvae encysted in muscle tissue of the pregnant bitch are reactivated during the last trimester and migrate transplacentally to the pups. It is important to realize that routine deworming of the bitch will not affect this process. The infestation of pups can be interrupted by administration of fenbendazole at 50mg/kg PO from day 40 of gestation to day 14 post-whelping. Ancylostoma caninum can also be transmitted transplacentally and is responsive to the above treatment.
External parasites are best controlled with environmental management and a flea comb for the bitch. Non-toxic environmental controls are now available. Avoidance of organophosphates and pyrethroids during pregnancy is recommended. The newer flea control products are not, at this time, approved for pregnant bitches.
Microfilaria of Dirofilaria immitis can cross the placenta. Although they will not create a patent infestation they can result in a pup that is a reservoir for spreading heartworm disease and may put the puppy at risk for adverse reactions to routine heartworm preventative medication. Pregnant bitches should be routinely tested for heartworms and maintained on heartworm preventative in at-risk areas. Both ivermectin and milbemycin oxime monthly preventatives are safe in pregnant bitches.
Certain blood values are altered by the pregnant state. The most notable is packed cell volume (PCV), which decreases to approximately 40% by day 35 of gestation. At term the PCV is often below 35%. The anemia is normocytic, normochromic and caused by hemodilution. This is due to increased plasma volume and can also affect measurement of serum levels of hormones.
The immune system is moderately depressed during pregnancy, resulting in a decrease in serum IgG. Creatinine decreases by 25-35% as well. Fribrinogen and other coagulation proteins increase during pregnancy. Diagnostic testing and medical treatment in the pregnant bitch should be performed with these alterations in mind.
Also known as pregnancy toxemia, this serious illness is most common in thin, poorly conditioned bitches. These bitches have inadequate fat stores, muscle mass, and dietary carbohydrate. They may present with nonspecific signs of illness, gastrointestinal distress, or seizures. Ketonemia and ketonuria without glucosuria often accompany the hypoglycemia. Because hypocalcemia presents with similar signs and can occur in term bitches, serum calcium level should also be evaluated. Treatment of hypoglycemia is with intravenous administration of dextrosecontaining fluids. Nutritional supplementation will be needed in bitches that do not voluntarily eat. Termination of pregnancy may be necessary in severe cases. Pregnant bitches, maintained on diets deficient in carbohydrate, developed hypoglycemia in the last two weeks of gestation. This resulted in a significant increase in stillborn pups and in neonatal mortality in the first three days of life.
Pre-existing subclinical diabetes mellitus may be aggravated by the pregnant state. Sensitivity to insulin is decreased as early as 35 days of gestation and continues to decrease as pregnancy progresses. Insulin should be given if indicated by carefully monitored blood glucose levels. The varying demands and hormonal alterations during pregnancy and parturition make glucose control challenging. Cross fostering of pups and retirement from breeding should be encouraged.
Although rare, failure to maintain appropriate serum progesterone level throughout pregnancy is a treatable cause of fetal loss. Monitoring of serum progesterone level allows accurate diagnosis of this problem. Serum progesterone levels above 2 ng/ml are required to maintain pregnancy. In a normal pregnancy, progesterone reaches peak levels of 15 to 90 ng/ml by 15-30 days post LH (luteinizing hormone) peak. During the last trimester, progesterone decreases to 4 to 16 ng/ml before dropping below 2 ng/ml approximately one day before parturition. Monitoring of serum progesterone level can be performed weekly if the levels are 20-50 ng/ml or daily if they are 5-10 ng/ml. Treatment of hypoluteodism can be performed with injections of progesterone in oil(2-3mg/kg IM every 24 hours). Alternatively, ally-trenbolone (Regumate, Hoescht-Roussel Agri-Vet Co) at 0.088mg/kg PO daily can be given. Ultrasonographic monitoring of fetuses can be helpful in assessing fetal viability. Fetal heart rates less than 160bpm indicate fetal distress, as does decreased fetal movement. Exact timing of ovulation, and therefore parturition date, is necessary so that progesterone supplementation can be stopped about 72 hours prior to expected parturition, allowing an approximation of normal decline of progesterone. Milk production by the bitch may not be adequate: supplemental feeding of pups should be planned.
Canine Herpesvirus (CHV)
The fatal form of this disease results from exposure of the pups during the last three weeks of gestation and the first three weeks of life. Canine herpesvirus is most commonly spread as a mild respiratory infection between adult dogs. Titers to CHV can be measured in the bitch prior to breeding to determine if she has had previous exposure. A naive bitch is at risk for infection during pregnancy, as a previously exposed bitch is not. The neonates are still at risk after birth in either situation. As no vaccination is currently available, prevention is the most effective approach. Complete isolation of the pregnant bitch and her pups for this sixweek danger period is effective in preventing infection. Unfortunately, no successful treatment is available if the pups become infected.
Administration of any medication is best avoided in the pregnant bitch, especially during days 13 to 30 of gestation. Some drugs have proven relatively safe, while others are definitely dangerous to the developing fetus (see tables). Many other drugs carry potential risks that have not been researched or established. The safest course is to avoid any medication of questionable safety and to only administer medication if absolutely necessary.
MONITORING THE PREGNANT BITCH
Prior to breeding, assessment of vaccine status, body condition, diet, and any routine medication should be made. This prebreeding visit is important in establishing baseline data and a plan for care during the pregnancy. The breeder's knowledge and expectations can be assessed and any necessary changes in care implemented. Older bitches should have a complete blood count, urinalysis, and biochemical profile evaluated at that time. Brucella canis testing and, if desired, CHV titers can be performed.
At the time of pregnancy diagnosis by palpation or ultrasonography further evaluation should be made. The bitch's body condition is again assessed and her appetite and diet evaluated. Changes in her activity can be discussed and the need for isolation in later pregnancy stressed.
A final prenatal evaluation can be done at 10-14 days prior to parturition. Abdominal radiography can help determine fetal count. Ultrasonography can be performed to assess health of the fetal vesicles and monitor fetal heart rate. Digital vaginal examination can be performed on any bitch that had a previously diagnosed vaginal stricture, as some do relax as parturition approaches.
Packed cell volume, serum glucose and calcium levels can be measured at this time as well. This is an excellent time to discuss indications of dystocia with the client and to instruct in monitoring twice daily body temperature in the dam to help monitor the onset of labor. Success has been seen in monitoring uterine activity in late-term bitches to better determine the onset and normalcy of labor.
In summary, the careful evaluation, care, and monitoring of the valuable pregnant bitch is an important, often overlooked, service. The veterinarian and breeder work as a team to ensure the best possible outcome for this special event. The institution of a planned, scheduled program can be a valuable addition to your practice.
Table 1: Drugs Considered Safe In Pregnancy
- amoxicillin with clavulanic acid
- pyrantel pamoate
- milbemycin oxime
Table 2: Selected Drugs To Avoid During Pregnancy
1. Bebiak DM, Lawler DF, et al (1987), "Nutrition and Management of the Dog," Veterinary Clinics of North America Small Animal Practice, May, pp 505-515.
2. Concannon PW (1986), "Physiology and Endocrinology of Canine Pregnancy," in Current Therapy in Theriogenology 2, David A. Morrow, ed, Philadelphia, PA, W. B. Saunders Company.
3. England GCW (1998), "Ultrasonographic Assessment of Abnormal Pregnancy," Veterinary Clinics of North America Small Animal Practice, July, pp 849-868.
4. Evermann JF (1989), "Comparative Clinical and Diagnostic Aspects of Herpesvirus Infections of Companion Animals with Primary Emphasis on the dog," in Proceedings of the Society for Theriogenology Annual Meeting (Idaho), pp 335-339.
5. Feldman EC, Nelson RW. (1996), "Breeding, Pregnancy and Parturition," in Canine and Feline Endocrinology and Reproduction, Philadelphia, PA, pp 547-558.