Among dairy breeds, the intense selection for higher milk production during the last 20 to 30 years has led to a negative energy balance in early lactation. Consequently as milk production increases, reproduction efficiency decreases.E.g. conception rate of 50% was considered poor performance 20 years ago. Today, is above average in the USA.
A major realistic goal of any breeder should be raise or market 75-85 calves per 100 cows every year.As pregnancy rate increases, the calving to conception interval decreases, thereby increasing the amount of milk produced per day of herd lifetime and reducing the number of cows culled for reproductive failureCollectively, this increases herd income
Services per 2.5 2.0 1.66 1.43 1.25conceptionConception 40 50 70 80 90rate %interpretation poor Poor desirable good excellent
Lactation VS ConceptionThe ability to conceive is influenced strongly by the physiology status of the cow.In mammals, milk is essential to survival of the young. Thus in early lactation, the body gives milk production the highest priority for the available nutrients.In addition to nutrients found in the diet, females in early lactation tend to mobilize their body reserves to support milk production.Generally, a female cannot eat sufficient amounts during early pregnancy.
They are in a state of negative energy balance. They loose weight and their ability to conceive is drastically reduced.It’s only at a later stage of lactation, when the energy ingested is in balance with the energy required for milk production, that the ability to initiate a new pregnancy increases.Depending on the milk production in early lactation. Negative energy balance may last for 2 to 10 weeks of lactation.
Energy deficiency in early lactation cannot be avoided but it should be minimized. In dairy herds where cows loose excessive body weight during early lactation and don’t show signs of estrus by 30-40 days after calving, changes must be made in feeding practices during early lactation, late lactation and dry period.
Excessive intake during late lactation and dry period can lead to “Fat cow” problems. cows that are too fat have a higher incidence of difficult calving, retained after birth, uterine infections and cystic ovaries. This disorders are frequently secondary to disorders associated with excess body reserves.Rapid mobilization of fat results in accumulation of fat in the liver. This causes the cow to loose appetite, which further worsens their energy deficiency and delays the return of normal estrus activity.
These problems will be minimized adjusting the feeding of cows, starting in late lactation to avoid under conditioning or over conditioning during the dry period.Feeding during the dry period should not be aimed at altering the amount of body reserves but simply to maintain the ideal body condition in the late lactation.
Body ConditionThe goal is to have a cow that is neither too fat or too thin in early lactation. For every Kilogram lost, it’s enough to produce 7 Kgs of milk.
• Body condition indicates how much stored energy a cow has for future use. BCS can help you track energy balance and understand production and reproductive performance.• The most common body condition scoring system ranks cows from one to five with a score of one being thin and a score of five being obese. Areas to evaluate when body condition scoring include hooks, pins, tail head, and the ligaments around these bones.• Body condition of feeding groups should be evaluated. It will reflect the true energy content of the diet.• Cows should be scored at calving during their first postpartum exam, when bred, when checked for pregnancy, some time during late lactation and at dry-off.
An evaluation of body condition can help you understand the past nutritional status of your cows and why your milk production and reproductive performance results are good or bad.It will also show you some of the challenges to come. Body condition is an indication of how much energy a cow has stored for future usage. Body condition scoring was developed to help farmers and nutritionists more definitively assess and track body condition. This is very important because the monthly changes in body condition tend to be more highly correlated with health, productivity, and reproduction than a cow’s actual body condition on any particular day.
BCS = 1.5 This cow is too thin and is hopefully rarely seen on a farm. This cow will not milk well or reproduce. This cow probably isn’t healthy. The vertebrae, short ribs, hooks, pins, and tail head are very sharp and visible. One-half of the length of the transverse processes is visible. The ligaments are easily seen. The area around the tail head and the dish of the rump (thurl) are very dished. There are folds of skin seen between the tail head and pins.
BCS = 2 This cow is very thin, causing low milk production and poor reproduction. Health may be OK. The spine and short ribs can be easily seen, but the individual vertebrae are not really apparent. The short ribs appear scalloped. The upper surfaces of the short ribs can be felt. One-half to a third of the length of the transverse processes is visible. The hooks and pins stand out. No fat can be felt on the pin bones. The ligaments are sharp and easily seen. The areas around the tail head and the thurl area are very dished. There are folds of skin between the tail head and pins.
BCS = 2.5 It is a reasonable goal not to have more than 10 percent of the herd scoring 2.5 or less. This is the lowest acceptable condition score. A cow with a score of 2.5 has vertebrae showing but they cannot be seen as individual bones. The short ribs can be counted but are not scalloped. One-third to a quarter of the length of the transverse processes is visible. The ligaments are easily seen but not as sharp as with a BCS of 2.0. Both the hooks and pins are angular but some fat can be felt on the pin. The areas around the tail head and thurl are dished.
BCS = 3.0 This cow could be a healthy, high-producing cow. But, if a cow calves in at a score of 3.0 or less, she may not have enough body fat to use for high peak milk production and to carry her through until dry matter intake increases. At this score, the dish of the rump (thurl) is at the transition between looking like a “U” and looking like a “V”. Any cow under a BCS of 3.0 has a thurl area looking like a “V”. The backbone can be seen but the individual vertebrae are rounded. Covering the short ribs is half to one inch of flesh. Less than quarter the length of the transverse processes is visible. There is fat covering the ligaments but they are still obvious. The hooks and pins have some fat that can be felt. The area around the tail head is dished but no folds of skin are seen.
BCS = 3.5 Dry cows and calving cows should have a body condition score of 3.5. On this cow, fat can be felt on the backbone, short ribs, and ligaments. The hooks and pins are rounded. No individual transverse processes can be seen. The thurl is somewhat dished. The coccygeal (tail head) ligament is barely visible but the sacral ligament can still be seen. The area around the tail head is rounded and filled in but not fat.
BCS = 4.0 Cows calving in at this condition will eat less, lose more weight and have more metabolic problems. This cow’s back is flat because fat has filled it in. The short ribs can not be seen individually but they can just barely be felt. The hooks and pins are obviously fat. The “U” between the hooks and pins is very flat with no depression. The ligaments cannot be seen. The area around the tail head is filled in and folds of fat are seen.
BCS = 5.0 This cow is extremely fat and will have metabolic and breeding problems. The backbone and short ribs cannot be seen and are hard to feel. The hooks and pins are buried in fat and hard to feel. The thurl is totally filled in. The tail head is buried in fat.
Reproductive EquationPregnancy rate = cow fertility% x Semen Fertility% x heat detection % x Insemination efficiency%Pregnancy rate is the number of animals that become pregnant per 100 Inseminations.
Cow FertilityCow fertility is influenced by many factors.The age of the animal has a strong influence on fertility. Heifers and second lactation cows are usually more fertile than first lactation cows and mature cows.Fertility is highest in the coolest months of the year, and when cows are: Free of reproductive diseases; Free of problems at calving; Free from nutritional imbalance—especially if the cow is not too thin or too fat at the time of calving. Fertility is also high when cows stop losing weight and begin to replenish body stores a few months after calving.
Heat Detection EfficiencyPoor heat detection efficiency is probably the single most important factor affecting the pregnancy rate of otherwise fertile cows. Heat detection efficiency is made up of two components: the level of detection and the accuracy of detection.Heat detection accuracy may be low because:The herdsman is not familiar with the signs of heat and fails to correctly identify the cow(s) in heat;Heat is correctly detected, but an error occurs in determining the cow’s identification or in recording the event (e.g., incorrect date).
The onset of heat activity follows a distinct pattern, with most activity occurring in the late evening, through the night, and in the early hours of the morning.Research shows that 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.
Insemination efficiencythis 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.
SynchronizationThis is designed to eliminate the need for heat detection before insemination through what is know as Timed Artificial insemination.producers have a reliable system that results in acceptable pregnancy rates to timed AI.It involves taking control of the estrus cycle using drugs to bring the cow on heat.This system is a useful management tool the world over.
advantagesAvoids the human error in heat detectionEarly rebreeding of non Pregnant cows thus reducing the open days.Solves the problem of silent heatTreats cases of cystic ovaries.
Consist of giving GnRH on day 0 then PGF2α 7 days later. A second injection of GnRH is given 48 hours later, and finally timed artificial insemination is done after 16-18 hours.This protocol has a 80% success rate in dairy cows.
Incorporation of Timed Artificial Insemination in dairy herd reproductive management programs reduces labor requirements for detection of estrus while improving overall reproductive performance and maximizing profits.