Bovine Reproductive Herd Health
441-457

BOVINE THERIOGENOLOGY

Dairy vs. Beef - click here to view a PowerPoint

• Several terms are routinely used in the cattle industry and we should be familiar with their meaning: heifer, first-calf heifer, dry cow, fresh cow, open cow, springer, "on DHIA", heat, replacements, clean-up breeder

• The goal of any herd health program is to increase profits and decrease the cost of production.
  •  One important aspect is to increase quality herd replacements while decreasing reproductive failures. Consequently, a decrease in reproductive culls will allow selection for other factors, such as milk production, etc. 
  • Another is to monitor the reproductive efficiency  achieved and by taking action to decrease the number of semen units used per conception (AI). 
  • Number of services (or AI) per pregnant cow will reflect the efficiency of conception and pregnancy rate when fertile cows are mated or artificially inseminated. 
  • An adequate reproductive efficiency will result in an increase production. For beef cows, more kg calf weaned/cow exposed to a bull will be obtained and for dairy cattle an increase in number of days in cow's life when she is producing milk most efficiently (see lactation curve).

• The 12 mo. calving interval is desirable because cows that calve every 12 mo. give more milk than cows that have a calf at longer intervals. This becomes obvious if one looks at the lactation curve. The closer two lactations are together, the more time is spent during peak milk production and less time during low milk production at the end of the curve. Having cows calve once a year (a calving interval of 12 mos., brings the curves as close together as nature will generally allow, maximizing milk production).

• The dry period is a time during which the farmer will stop milking their cows to allow the mammary tissue to repair itself and prepare for the next lactation. It allows the cow to have a higher peak milk production on the subsequent lactation. The farmer stops milking the cow 45-60 days from the anticipated calving date.

• A vaccination program (JAVMA (8/1/86) is an important aspect of herd health that affects reproductive performance, mainly regarding diseases which cause abortions. 
• Physical facilities should minimize the deleterious effects of harsh environmental conditions such as excessive cold, heat, humidity while allowing comfortable conditions for reproductive events such as estrus signs, calving, breeding practices, etc. 
• Quality and availability of replacement heifers are also important, mainly because the goal is to have a heifer calving and lactating while she still has not completed her total physical body growth and maturation. 
• Poor or imbalanced nutrition can be the underlying cause for many reproductive problems such as acyclicity, delayed uterine involution, metritis, retained placenta, abortions, etc. Body condition scoring (Edmonson et al., J Dairy Sci, 72:70, 1989) is a simple and efficient way to check the nutritional status in a herd. It is graded from 1 to 5 in dairy cows and 1 to 9 in beef cows. 
• General health (parasites, feet, milk fever, ketosis, lameness, etc.) an increase in certain problems may point to a specific area to correct (increased abortions ->vaccination program; increase days to first service -> heat detection; increase postpartum metritis -> calving environment). The dry cow period should be around 45 to 60 days before the next calving to maximize best production in the next lactation.

• Common traits in any herd health program will include client education, routine exams, collection and processing of data, assessment of performance, establishment of goals, implementation of changes to meet goals, monitoring response (set reasonable goals and change them as they are met). Farmers must be willing to keep records and ID cows. Adjust and set the performance goals according to the characteristics of the farm you are working with (dairy vs. beef, large vs small, computer availability).

• Advantages of artificial insemination are often obscured by problems such as inseminator incompetence (insemination technique, timing of insemination, accuracy of estrus detection). Natural breeding implies that the herd be disease free of agents such as Trichomonas foetus, Campylobacter spp., Brucella sp., Mycobacterium sp.). Bulls should be checked periodically for semen quality (Breeding Soundness Evaluation).

• To calve every 12 months, a cow must be bred by 83 days post calving (282 days gestation + 83 = 365)

• The main goal of the beef cattle producer is to produce the maximum kg calf weaned/cow exposed to a bull. This can be affected by several factors:
  • Calf mortality (dystocia, heifers with small pelvic diameter)
  • Decreased weaning weight - goal is to have a 500 lb calf at 250 days
  • Decreased pregnancy rate

• Silent heat or anovulatory estrous cycles at the beginning of the breeding season can be caused by inadequate nutrition. 
  • Assessing body condition score is a good way to check cows before calving. 
  • Cows should be fed in the last trimester of pregnancy to calf at a body condition score 5 to 6. 
  • The rule of thumb is to have cows in a good body condition before calving. 
  • After calving, another alternative is to flush the cows 3 weeks before the start of the breeding season coupled with 48 h calf removal (suckling causes postpartum anestrus via inhibition of GnRH and subsequently decrease pulsatile LH secretion. This hormonal inhibition is probably modulated by endogenous opioids. The physical presence of the calf is also important). There is a need for good fences and a high energy calf starter.

• Moderate condition score at calving - 60 d calving season (60 d breeding) - 48 h calf removal at start of breeding - Cows gaining weight for 5 wks starting 2 wks before breeding starts - Bulls of high fertility
• The importance of keeping good records can not be overemphasized (percent calf crop, pregnancy rate, culling rates, breeding efficiency of bulls, calf mortality, etc.).

• If working with AI, utilize heat synchronization schemes to maximize efficiency and minimize costs
• Replacement heifer management should include periodical check on growth. You should start to breed heifers 21 d before cows. Consequently, they will calve earlier and have longer to breed back (remember, heifers are still growing and need more time to cycle back)

• The goal is to have a breeding season of 63 days (63 = 3 estrous cycles), but most people still use 90 or 120 days)
• Vaccinations
• Check the vaccination history of the herd. Brucellosis, IBR, BVD, leptospirosis, clostridia, are recommended. Some herds may need immunization against trichomonas and campylobacter. Annual vaccinations should be given shortly before the breeding season.

• Brucellosis should be checked periodically, mainly if the farm is not in a state Brucella-free.
• Tuberculosis is also another important disease to be tested. 
• Bulls should be negative for trichomoniasis (3 weekly cultures)

• Do not visit the farm every 3 weeks. Better when done monthly, bimonthly, weekly, etc.
• When doing reproductive exams or other routine procedures, can assess dairyman's performance in other areas, e.g. nutrition, hoof care, heifer raising
• Tailor program to dairyman's own personal needs. This will depend on number of cows, level of achievement of performance goals, etc.

• It is very important to keep updated records. 
• Individual cow records will allow veterinarian and farmer to decide whether a particular cow is in trouble or not. 
• Assembling records of individual cows to give a picture of the herd as a whole serves two purposes. 
  • On the one hand it makes it easier to draw up lists of those cows which need to be brought up for herd checks, need to be dried off, etc. - so called "action lists". 
  • On the other hand they can provide the farmer with valuable measures of herd performance. Individual cow record should include ID, date of birth, vaccination record, breeding and heat dates, calving history (dystocia, RFM (Retained Fetal Membranes)), mastitis, other health history, reproductive exam information. Daily action list will include cows to calve, breed, etc.

• Cows (between 14 and 21 days post partum) should be included in this list. 
• Those cows which have been fresh more than 21 days should have no fluid in their uterus and the uterus should be retractable to allow thorough examination. 
• If a cow's uterus is involuting behind schedule, or abnormal post partum, we will find her on this check. 
• We do not routinely perform post partum checks earlier than three weeks since a normal cow would still have an enlarged uterus and maybe some fluid at that time, and it would be difficult to identify a cow with a problem. 
• Fresh cows found to be undergoing an abnormal uterine involution will suggest you to check calving area, calving practices, dry cow nutrition, etc. 
• High calf mortality also suggest you check on calving practices.

• Cows with more than 3 services are also in the vet check list. Uterine or ovarian pathology should be ruled by gynecological exam. Abnormal cycles, discharges, should be investigated.
• Heat detection problems
• Cows found open and not rebred in the next 21 days reveal a heat detection problem if reproductive tract is normal. Cows without recorded heat after 21 days past the voluntary wait period suggest the same problem.

• This list should include all cows bred >35 days and not seen in heat. 
• You can also recheck all pregnant cows seen in heat or with abnormal discharge or pregnant cows before the dry period to make sure they are still pregnant. 
• Because roughly 1 in 10 cows will loose a pregnancy before day 90 a recheck can be scheduled for this time.

• Heat detection is the foundation for a successful reproductive program.
• A good heat detection rate, requires all cows have an identifiable ID. 
• A good plan for a heat detection program must include post partum and pre-breeding checks. 
• Heat detection can be labor intensive and requires time, knowledge and motivation (some farms have an incentive program). 
• All cows should be sound and be comfortably housed ( remember the effects of nutrition, lameness, heat stress, etc.)

• From Dairy Herd Improvement Assoc. (DHIA)

• Standing to be mounted

• Searching
• Increased locomotion, vocalization, and tail movements
• Courtship
• Increased grooming, mounting attempts with other females
• Arousal
• Homosexual behavior and bull receptivity

• Search
• Chin resting, testing for lordosis
• Courtship
• Flehmen, nuzzling and exploring perineal region
• Arousal
• Penile protusion with dribbling of seminal fluid with few spermatozoa, erection and copulation

• Swollen vulva; clear vaginal discharge (mucus) ; roughened tailhead; pink vaginal mucosa. After estrus (1-3 days), 50% will have a bloody discharge (metestrous bleeding)

• LH surge occurs at the beginning of estrus and will cause ovulation 24 to 30 h later.
• Average estrus lasts 14 - 18 h. It is shorter in beef than in dairy cows. 
• Cows should be inseminated in the last 2/3 of estrus up to 6-8 h after standing heat. 
  • The a.m./p.m. rule is a good and practical way to manage artificial inseminations. 
  • If a cow is seen in heat in the morning, she will be scheduled for insemination in the evening and vice-versa. 
  • Mature, ovulated oocytes hold good fertility only for 10-12 hours.

• It is the best but is labor intensive, time-consuming, and boring. 
• Cows need to checked 30 minutes every 12 h. 
• Only 25-30% will show standing heat in 2 consecutive periods of heat checking. 
• Good footing surface is essential for a good heat behavior display. 
• In the summer time, mainly here in the S.E. U.S., many cows will show heat between 12 a.m. and 6 a.m.

• Estrus-detector animals are very useful to enhance heat detection and include vasectomized bulls, surgically altered bulls or hormonally treated animals (males or females).

• Pressure-sensitive mount detectors
• Mount detectors applied with adhesive in the cow's rump. They will be activated by sustained pressure caused by the mounting (example = Kamar). Problem with false positives. Remember to write cow's ID on cloth.

• Chalking/Painting the tailhead is another inexpensive option.

• Electrical resistance of reproductive tissue fluids
  • Electrical resistance is decreased during proestrus and estrus. Extremely labor intensive.
  • 
• Pedometers register increased walking times
• Electronic pressure-sensitive mount detectors - Heat Watch
  • Very efficient
  • Duration and number of mountings are transmitted to a receiver interfaced with a computer.
  • 
• Rectal palpation
  • Sensitivity and Specificity of Rectal Palpation to Determine the Presence of a
    Mature Corpus Luteum in Cycling Cows

  	Corpus Luteum Present
  Palpate Corpus Luteum	Yes	No	Totals
  Yes	8	5	13
  No	2	6	8
  Totals	10	11	21

   

• Milk progesterone
• Dogs

Assessing heat detection efficiency

• Percent pregnant at pregnancy check - > 90%
• 24 day heat detection trials
• Average estrous cycle length - closer to 21
• Ratio of single to double heats (>6:1)