Chapter Two - Animal Reproduction 2 - PPT PDF

The Reproductive Performance of Dairy Cattle Eman Sallam  Reproduction is a vital factor in determining the efficiency of animal production.  At best, a cow is only likely to produce a single calf per year.  The reproductive performance of a dairy herd has a significant effect on...

The Reproductive Performance of Dairy Cattle Eman Sallam  Reproduction is a vital factor in determining the efficiency of animal production.  At best, a cow is only likely to produce a single calf per year.  The reproductive performance of a dairy herd has a significant effect on the profitability of that herd.  In dairy cows, reproduction has two major functions: to induce the onset of lactation and to provide replacement animals for the current generation of cows. Eman Sallam  The main objective in the dairy herd is to produce milk as economically as possible.  Poor reproductive performance is one of the most common reasons for culling in dairy herds. Because a. it affects the amount of milk produced per cow per day of herd life, b. affects the longevity of the cow in the herd, c. and indirectly influences herd replacement costs, breeding costs, and expenses for veterinary treatment & drugs. Eman Sallam  Reproductive performance refers to a cow's ability to produce calves at regular intervals.  It is calculated as the number of cows that got pregnant \ the num ber of cows that were eligible to be pregnant.  it is a measure of the speed at which cows got pregnant after the voluntary waiting period. Successful reproduction demands a lot of expertise by the producer because many factors affect the likelihood of pregnancy: 1. Cow's fertility 2. Bull's (semen) fertility 3.Heat detection efficiency 4. Insemination efficiency. Eman Sallam  1. Cow fertility is influenced by many factors: ✓ The age of the animal has a strong influence on fertility. Heifers are usually more fertile than mature cows. ✓ Fertility is higher when the cows are: a) Free from reproductive diseases. b) Free from problems at calving. c) Free from nutritional imbalance (especially if the cow is not too thin or too fat at the time of calving). Eman Sallam  2. Bull fertility influenced by many factors: ✓ Age and sexual maturity ✓ Proper nutrition ✓ Libido (sexual desire). In the case of A.I, the fertility of a bull is also affected by semen dilution, processing, storage, and handling from the time it is collected to the time it is deposited in the cow’s uterus. Eman Sallam  3. Heat detection efficiency: Poor heat detection efficiency is the most important factor affecting the pregnancy rate of otherwise fertile cows. Heat detection efficiency is made up of two components: a. The level of detection. b. The accuracy of detection. Eman Sallam  4. Insemination efficiency: ✓ In general, insemination efficiency is close to 100% when a sound bull is used for natural service. ✓ In the case of A.I, however, this factor is measured primarily by the competence of the herdsman and inseminator to: Determine the correct timing of insemination. Handle the frozen semen correctly. Deposit the thawed semen accurately at the entrance of the uterus. Eman Sallam Eman Sallam  Reproductive characteristics of dairy cattle Parameter Mean Range Sexual season Polyestrous Age at puberty (months) 9 5 - 18 Estrous cycle - Length (days) 21 18 - 24 - Estrus (hours) 18 2 - 30 Ovulation - Type Spontaneous - Time after the end of heat (hours) 10 - 12 - Number of eggs shed 1 - Fertile life of ova (hours) 6- 10 Gestation length 280 278 - 293 First ovulation after calving (days) 15 - 20 Eman Sallam Item Goals of reproductive Optimal Value indicating performance value serious problems 1. Age at first breeding (m) 15 18 2. Age at first freshening (m) 24 30 3. Calving intervals (m) 12.5-13 > 14 4. Days open 85-110 > 140 5. Length of dry period (days) 45-60 < 45 6. Reproductive cull rate < 10 > 10 (% year) 7. Abortion rate (% year) < 2 >5 Eman Sallam Item Goals of reproductive Optimal Value indicating performance value serious problems 1. Days to first observed heat < 40 > 60 (post-partum) (days) 2. No of cows observed in heat > 90 < 90 within 60 days post-partum (%) 3. No of cows with a breeding > 85 < 85 interval 18-24 days (%) 4. Days (open) to first service 45-60 > 60 (DFS) 5. No cows open 120 days or < 10 > 15 more (%) Eman Sallam Item Goals of reproductive Optimal Value indicating performance value serious problems 1. Number of Services per < 1.7 > 2.5 conceptions 2. First service conception of 65-70 < 60 heifers (%) 3. First service conception rate of 50-60 < 40 lactating cows (%) 4. Cows that conceived with less > 90 < 90 than 3 services (%) 5. 60-90 day non return bulls (%) Above or More than 5% stud below stud average average 6. Calf crop (%) > 90 < 90 Eman Sallam Item Goals of reproductive Optimal Value performance value indicating serious problems 1. Calf mortality (% under 28 days of age) 5 2. Cow mortality (%) 2 3. Incidence of herd culled (%) 30 > 35 4. Incidence of retained placenta (% of 5 cows calved/mo) 5. Incidence of lameness (%/mo) 5 6. Incidence of displaced abomasums (% of 5 lactating cows) 7. Incidence of milk fever (% of < 10 > 10 multiparous cows calved / mo) 8. Incidence of ketosis (% of fresh < 15 > 15 cows/mo) Eman Sallam  Determining the reproductive efficiency There are several ways to monitor the rate of reproductive efficiency of dairy herds using what is called reproductive indices. Reproductive indices are indicators of the reproductive performa nce of a herd (days open, calving interval, etc.). They can be calculated when reproductive events in the herd have been properly recorded. Eman Sallam 1. Age of heifers at first calving 2. Calving Interval 3. Voluntary waiting period 4. Days (open) to first services 5. Days open 6. Services per conception 7. Percentage of Non-Returns 8. Conception rate 9. calf crop % Eman Sallam 1. Age of heifers at first calving (AFC)  Age at first calving, the period that a heifer needs to reach puberty and to reproduce for the first time, is an important factor in the cost of rearing replacements in dairy herds.  First calving marks, the beginning of a cow's productive life.  the average age of 24 m. at first calving (freshening) is ideal in terms of maximizing production per day of life of the animal.  If AFC exceeds 30 m. it is a costly problem, and the cause (s) should be identified and corrected. Eman Sallam  The length of rearing period has a direct effect on the total cost of heifer rearing therefore, controlling AFC can be used as a management factor to reduce rearing costs.  AFC is closely related to generation interval. Heifers are usually mated when they are mature enough to withstand the stress of parturition and lactation.  decreasing AFC is also associated with a shorter generation interval and subsequently higher genetic progress. Eman Sallam 2. Calving Interval (CI):  CI can be divided into three periods: gestation, postpartum estrus (from calving to first estrus) and the service period (first postpartum estrus to conception).  It defined as the number of months between the two successive calving dates. CI is a very accurate indicator of what has happened in the past but does not indicate current status.  CI as a reproductive management figure is affected by two reproductive figures: a. Gestation length. Obviously, gestation length cannot be altered. b. Days open consist of the length of the postpartum estrous and service periods. This part of the calving interval that can be shortened by improved herd management. Eman Sallam  Ideal CI is 12.5-13 month.  If the average herd CI exceeds 14 m., it indicates a serious problem, and the cause(s) should be identified and corrected.  Long CI a. reduce the percent of cows in the early lactation period, and b. fewer calves are born each year.  High producing cows tend to have silent heat more than low producing one missing cows in a heat cows do not get bred back as early as possible increased days open period and consequently increase CI. Eman Sallam 3. Voluntary waiting period (VWP):  VWP is the interval of time from calving until the manager is willing to rebreed the cattle.  It is fixed period following calving before attempting to bred a cow.  It determined by herd owner\ manager.  Often the same for all cows in herd although some have a longer VWP for 1st lactation cow.  It usually between 40-70 day.  High producers tend to have silent heat more often than low producers. so Dairy farmers may give high producers a longer wait period before being bred back. Eman Sallam 4. Days (open) to first services (DFS):  It is number of days between calving and when a cow is bred back for the 1st time after calving.  Animal may or may not conceive to this service\ breeding.  It is an indication of heat detection intensity.  An average days to first service of 45-60 days is considered ideal and if it exceeds 60 days, it indicates a serious problem, and the cause (s) should be identified and corrected. Eman Sallam 5. Days open (DO):  It is defined as the period between parturition and the following conception (calving-conception interval) or average number of days between recent calving and conception.  DO is influenced by months postpartum especially on uterine involution and rebound ovarian cyclical activity and the onset of estrus which consequently affect when breeding begins postpartum. Also affected with heat detection efficiency. Eman Sallam  Good heat detection is the single most important factor in Minimizing DO.  A good practical goal for DO is 85 to 110 days.  Minimizing days open is economically beneficial as lead to: a. Increasing milk yield relative to labor and feed costs, b. Increasing the number of calves c. Increasing lifetime productive days d. As well as reducing breeding costs and culling rates. N.B: DO may equal DFS if cow conceive after 1st breeding after calving. Eman Sallam 6. Services per conception (pregnancy) (S/C):  It is a measure of fertility in cows with reproductive successes and have become pregnant. However, it is a measurement that combines the effects of semen quality, fertility of the cow, timing of insemination, semen handling and insemination technique, in accurate heat detection, as well as factors such as high environmental temperature and stress.  The increased number of S\C often indicates the problems with cow reproductive system, which has a negative impact on farms profitability. Eman Sallam  Calculation of services per conception (S/C):  S\C is calculated by dividing the total services to pregnant cows in the herd by the number of pregnant cows. 𝑆\𝐶 = (𝑇𝑜𝑡𝑎𝑙 𝑠𝑒𝑟𝑣𝑖𝑐𝑒𝑠 𝑡𝑜 𝑝𝑟𝑒𝑔𝑛𝑎𝑛𝑡 𝑐𝑜𝑤𝑠) ⁄ (𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑟𝑒𝑔𝑛𝑎𝑛𝑡 𝑐𝑜𝑤𝑠)  A good goal would be between 1.5 and 1.8 S\C. the number of S\C around 2 is still acceptable, but values exceeding 3 are indicative of considerable organizational and/or health problems with reproduction. Eman Sallam 7. Percentage of Non-Returns (NRR):  NRR is the most frequently used measure for male fertility. AI centers use NRR to evaluate fertility of the entire operation as well as for individual sires and technicians.  NRR is defined as the percentage of cows inseminated for the first time within a certain period, usually a specific month, that have not returned for a subsequent service and so are presumed pregnant.  Or proportion of cows that are not subsequently rebred within a certain period after 1st insemination as presumed be pregnant. Eman Sallam  Most AI studs calculate a 30 to 60-day and a 60 to 90 day NRR. The most widely used Figure is the 60-90 day.  NRR calculated for all first services performed during the third preceding month. This figure allows more time for repeat services and also includes a greater proportion of early embryonic mortality than a 30-to 60-day NR.  NRR is associated with age at insemination, days from previous calving to insemination, milk production level at the time of insemination. Eman Sallam 8. Conception Rate (CR):  It is the number of pregnant cows over total services in a given period of time. 𝐓𝐨𝐭𝐚𝐥 𝐧𝐮𝐦𝐛𝐞𝐫 𝐨𝐟 𝐩𝐫𝐞𝐠𝐧𝐚𝐧𝐭 𝐜𝐨𝐰𝐬  𝐂𝐑 = × 𝟏𝟎𝟎 𝐓𝐨𝐭𝐚𝐥 𝐧𝐮𝐦𝐛𝐞𝐫 𝐨𝐟 𝐬𝐞𝐫𝐯𝐢𝐜𝐞𝐬 (𝐛𝐫𝐞𝐞𝐝𝐢𝐧𝐠𝐬)  it is usually expressed as a % pregnant per service. So, if 100 cows receive 170 inseminations over a 12-month period and 85 become pregnant then the pregnancy rate is 50% (85/170*100).  Partial goal can be stated as 50-60% (lactating cows) and 65- 70% (heifers) for the first service, 80% for the first two services and more than 90% for the first three services. Eman Sallam 9. Calf crop %:  Calf crop define as the numbers of calves that are born annually to a particular cow group. This is usually expressed as a percentage of calves weaned from a particular cow group  A fertile herd should produce more than 90% calf crop annually if cows only are considered or a 110% calf crop annually when heifers are included, and turnover rate is 25 to 30%. Eman Sallam  When to breed dairy heifers?  Raising dairy heifers (animals over one year age that have not had a calf) to an adequate size and with an AFC between 22 and 24 months can optimize profitable milk production.  This achievable goal requires proper nutrition and feeding management, so heifers are large enough to breed at 13 to 15 months old.  Live weight is more important than age in determining the onset of estrus. Heifer age can give you a rough guideline as when your heifers are ready for breeding but knowing height and weight will assure you, they are ready to be bred. Eman Sallam  Shortening the period from puberty to first calving can decrease rearing costs, while maintaining healthy heifers through their first calving.  According to the Nutritional Requirements of Dairy Cattle (NRC, 2001), a heifer is ready for breeding when it reaches 55 to 65 % of its mature body weight, which for most animals occurs by 14 months of age.  Conception can occur at about 360 - 400 kg of about 65% of mature live weight. For ease of calving at two years. Eman Sallam  Heifers should be bred by weight, not age due to: Why?  Calving weight had a greater impact on first-lactation performance than did calving age i.e., performance of dairy cows is explained by size than by age at calving.  Heifers at the same age can be a wide variation in size. Consequently, for breeding heifers that have a similar age at conception (15 months) and at calving (24 months) will be inconsistent ease of calving, inconsistent health around calving, or inconsistent performance after calving.  Dairy heifers bred late (after reach target weight) can have metabolic problems at calving, such as ketosis. Additionally, reduced milk production and wasted money used for feeding can be a concern. Breeding by heifer size could help address these challenges, allowing heifers to enter the milking herd sooner. Eman Sallam Ideal age at 1st Calving is 24 Months. Why Should We Consider It? Lifetime output of the cow is increased. Leads to potentially faster genetic progress as reduces generation intervals. A lower proportion of non-productive females in the herd. Early calving produces more calves per 100 cows. The earlier heifers enter the milking herd, the sooner the return on the initial investment. Moreover, there is a reduction in the net cost of rearing replacements. Eman Sallam  Heat detection  Heat detection is very important for daily reproductive management and also to define the optimal timing for A.I.  In cattle the estrus (heat) is defined a period of acceptance for mating (sexual receptivity) that normally occurs in non-pregnant animals. Or define as Regularly occurring state of sexual receptivity during which the female will accept male.  The accurate and efficient detection of heat in dairy cattle is an important component of a good reproductive management program. Failure to observe cows in estrus is the biggest cause of reproductive management problems in most herds. Eman Sallam Individual cows may not be observed in estrus for one of two reasons: Anestrus: the ovaries of the Heat missing: the dairy cow are not functioning producer or the heat properly, and the cow is detector misses seeing a anestrus (failure to have an cow that actually is in estrus estrus cycle). (the most common cause). Eman Sallam  Inadequate heat detection affects herd profitability in several ways: Combinations of Insemination Decrease unrecognized of pregnant Lower conception Undetected estrus and cows lifetime milk rates and heats result in low mistakenly production wasted semen longer calving conception identified in and fewer and time intervals. rates may heat may calves. (both are very lead to culling cause costly). of normal abortion. cows. Eman Sallam  How to Improve the efficiency of heat detection? 1. Ensure knowledge and up-to-date team training: a. What is estrous cycle? It is the period of sexual receptivity of open cows and heifers normally occurs every 18 to 24 days remember every cow is an individual, so focus on the range not the number of days. Why Heat Occurs?  Egg Develops in Cow’s Ovary produce estrogen, estrogen causes changes in reproductive, circulatory, and nervous systems. These changes are observed as signs of heat. Eman Sallam  Progesterone is Secreted from yellow body (Corpus Leutum). Progesterone Suppresses Egg Development and Heat Signs for 3 Weeks or Duration of Pregnancy.  As we know, the heat cycle is controlled by two hormones, Estrogen and Progesterone. Estrogen causes the external signs of heat to occur, making A.I. possible. Eman Sallam  The ovarian hormones control the reproductive cycle for two or three days. If the cow is mated and becomes pregnant those hormones remain in control and the cow will not have a regular estrus until she has her calf. If the cow is not bred, she will begin the next stage in the cycle as the ovarian hormone lose control of the reproductive tract, hormones from the pituitary gland take over the estrus cycle and begin preparing another heat period. Eman Sallam b. Knowing estrous signs: Signs of heat:  Most heat activity occurs in the late evening, through the night, and in the early hours of the morning.  More than 70% of mounting activity takes place between 7:00 at night and 7:00 in the morning.  In order to detect more than 90% of the heats in a herd, cows should be observed carefully in the early hours of the morning, the late hours of the evening, and at four- to five-hour intervals during the day. Eman Sallam Timeline for Heat Signs in Cattle Coming to heat Standing heat Going out of heat 6-10 hours 6-24 hours (18 hr.) 10-12 hours  Stand and bellows  Stand to be mounted.  Not standing to be Signs  Smell another cow It is a reliable indicator ridden  Attempt to ride another of true estrus.  Smell other cow cow but not stand to  It is best sign of a cow mounted s fertile period  Red and swollen red vulva  Clear mucous discharge from vulva Eman Sallam c. Knowing Timing of insemination: Moreover, we can also understand the following facts: a. Most cows remain in standing heat about 18 hours. b. The egg becomes available for fertilization about 10-12 hours after the end of standing heat. c. The egg remains fertile about 6 to 12 hours. d. Sperms remain alive inside the cow for approximately 18 to 24 hours. e. Sperms must be in the female reproductive tract about 6 hours before they can reach the egg to fertilize it. From all previous facts, the best time to breed dairy cattle can be obtained by breeding during the last half of standing heat period. Breeding earlier or later than this reduces conception because of reduced viability of either sperm or ova. Eman Sallam 2. Observe your cow, no substitute for visual observation:  Time and frequency of visual observation play an important role in detecting cows in estrus.  Observe for heat at least 30 minutes, twice a day. Why double observation daily at least? As Observation cows once a day will miss cows showing standing heat earlier.  More frequent observations improve heat detection efficiency.  The heat detection usually be done during the quite times of the day. Eman Sallam  Researchers found that mounting activity of cattle in estrus is concentrated (70%) around dusk (sunset) and down (sunrise).  One person (heat detector) should be identified and given the responsibility of being the primary observer for estrus.  Early morning, noon and late evening observations for 20 minutes each are necessary to observe more than 90 percent of the heats in a herd.  During hot weather, watch animals earlier and later each day. During cool weather, the middle of the day is generally the best time to watch. Eman Sallam  Times Percent of Cows Observed in Heat Observed No. Minutes Observed 5 10 20 1 26 52 63 2 36 72 86 3 39 79 95 4 49 82 98 Source: OLDS (1980) Eman Sallam 3. Choose the right tools for heat detection  accurate observation is of primary importance in detecting heat. Several aids also are available to help confirm and identify cows not exhibiting obvious signs of heat. Heat detection aids in dairy herds includes: a. Heat expectancy chart, b. Mount detection aids, includes  Pressure- sensitive mount detectors or Heat detection patches.  Tail chalk, crayon, or paint or Tailhead marking. Eman Sallam c. Heat detector animals (teasers), includes  Vasectomized or surgically modified bull  Androgenized steers  Testosterone–treated female d. Electronic aids,  Activity meters (pedometers)  Vaginal electrical resistance Eman Sallam  Anticipate heat with records: By recording accurate herd heat detection and insemination information on barn charts is essential to increase the efficiency of heat detection. Proper identification of cows (ear tags, freeze bands) is important in visual observation of heat detection. Eman Sallam  Heat detection efficiency and accuracy:  Efficiency of detection of estrus is usually expressed as the percentage of possible estruses that were observed over a given period. Fact, most calculations of detection efficiency actually are the number of cows observed, recorded, and reported as being in estrus divided by a calculated number of estruses that should have occurred over that time period multiplied by 100 Eman Sallam  Accuracy of detection of estrus is the percentage of estruses observed that are true estruses. There is a difference between the accuracy and the efficiency of heat detection. Inaccurate heat detection occurs when cattle are inseminated but are not in true estrus (Standing heat). Inefficient heat detection simply refers to too many unobserved or missed heats. Many reproductive problems herds experience both inaccurate and inefficient heat detection. Eman Sallam  Breeding after calving:  The dairy cow is a polyestrous animal that is she cycles regularly regardless of season of the year. it takes at least 30 days after calving for a cow's reproductive tract to return to normal. Therefore, some cows can be bred starting 45-60 days after calving.  Your veterinarian should palpate the reproductive tract of each cow as soon after 30 days after calving as possible to make sure the cow is ready to breed.  Most normal cows have a first heat period 20 to 60 days after calving.  All cows fresh 40 days or more that have not been in heat should be examined by a veterinarian and treated as needed. Eman Sallam  Rebreeding at first heat 50 days after calving is reasonable for: Whose reproductive Cows that have not tracts have been For average or below experienced calving palpated and found average producing problems or retained to be normally cows. placenta, involuted, Eman Sallam It is advisable to recommend waiting until 60-90 days for: Those that have experienced Higher producing cows, problems at or since last calving. Eman Sallam  Two systems can be followed to determine when to inseminate a dairy cow in estrus: Breeding either too early or too late allows will result in poor conception. Artificial Insemination: Cattle should be inseminated during the last half of standing heat (best fertility is obtained). A. Morning-evening rule (a.m. - p.m. rule)  For many years, dairy producers followed the a.m. - p.m. rule when inseminating.  This rule dictates that cows and heifers first observed in heat in the morning should be bred late in the afternoon. Likewise, cows and heifers first observed in heat in the afternoon should be bred the following morning. Eman Sallam  B. Once-a-day insemination  Although, the a.m. - p.m. rule is still a good principle, but many producers have now successfully gone to once-a-day insemination.  This rule dictates that cows and heifers first observed in estrus in the afternoon and the following morning should be bred late that morning. Advantages of the once-a-day rule:  Results in high conception rates comparable to the a.m.- p.m. rule,  Allows all breeding to occur at one time during the day. Eman Sallam  Benefits of improved reproductive performance: Higher average milk yields each day. Cows with poor reproductive performance will spend more of their time in late lactation when daily milk yields are lower. Fewer cows that have become excessively fat because they have failed to conceive. Less compulsory culling of cows failing to become pregnant Fewer cows with long dry periods. Eman Sallam  Reduced insemination and semen costs. Heifers calving at a younger age. Increased number of calves produced each year, thus providing more animals for sale or as replacements for the milking herd. More profits, less work and less worry. Eman Sallam Thank you Eman Sallam