2002 FebruaryReproductive Performance
Do you want a tighter calving pattern?
Would you like to reduce the number of late cows?
Want to get more cows in calf earlier to AI next season?
Now is the time to look at how this can be achieved next season. The InCalf study identified 6 important factors that have significant effects on herd reproductive performance in many seasonal calving herds. One of these important factors is :
Calving date to mating start date interval
Calving date to mating start date interval has been found to have a huge effect on fertility. To allow all cows in the herd to have a long calving to mating start date interval it is important to achieve a tight calving pattern.
Why is calving date to mating start date interval so important?
The InCalf study found :
- Cows that had calved by the 3rd week of calving had the highest fertility.
- Cows calved in weeks 4-6 of calving had reduced fertility
- Cows calved after week 6 are quite likely too have poor reproductive performance
What can I do to ensure a long calving to mating start interval?
There are three key areas to focus on to achieve a tight calving pattern, they are :
- Heifer Management
- Calve as many first calvers as possible in the first 3 weeks of calving.
- It is achievable to calve 70% by the first 3 weeks and 95% by 6 weeks
- Yearlings must be in good condition and exceed minimum target weights for mating.
- Use adequate numbers of highly fertile bulls, (1 bull per 30 yearlings)
- Purchase Decisions
- Calving dates of any purchased cattle are an important consideration
- Ensure cattle being purchase have reliable estimates of dates of conception
- Place a higher value on cattle that will calve earlier in your calving period, than cattle that would calve later (after the 1st 3 weeks)
- A Planned Approach To Calving Induction
- How do I plan an induction program?
Firstly calving dates need to be obtained by pregnancy -testing the herd. This is best done early. Ideally the herd is pregnancy tested 8-12 weeks after the end of AI followed by a retest of the not in calf cows 6 weeks after mating is completed. This improves the accuracy of aging of the pregnancy. Anytime after the bulls have been removed for longer than 6 weeks is suitable. Once calving dates have been collated, any cows that will calve after the first 6 weeks of calving can be identified for an induction program.
These late calving cows can be induced to calve between 8 and 11 weeks before their natural calving date. For many, this will be within the first 3 weeks of calving. This gives them a much longer calving date to mating start date interval. Cows will have an improved chance of getting in calf early to AI and maintaining their early calving cycle within the herd.
Although it is feasible to induce all late calving cows, there is a higher risk of animal health problems inducing cows over 6 years of age. Studies have also shown that older cows have less ability to make satisfactory gains in their calving time following induction.
This strategy of identifying late calving cows early in the season and planning an early induction program is one of the most effective tools available to improve reproductive performance in a herd.
For more information about inducing cows click here.
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Grain - to feed or not to feed
The inclination to reduce grain inputs this season has been assisted by a favourable winter and spring. Summer is now starting to take its grip and pasture feed is quickly disappearing and being replaced by silage and crops. If summer continues to be dry and hot then most of us will be facing a significant feed shortfall in February and March that is normally offset by grain.
Determining the level of grain feeding in the herd that is profitable can be a daunting task. Some farmers make a rash decision to either feed at high levels regardless of the economics, or to pull out grain all together and let seasonal conditions take control of lactation level.
Whatever the decision, it is valuable to make some assessment of the impact of grain or no grain before acting. Some of the factors for consideration are discussed below.
Assessing the return in immediate milk production
In summer and autumn, in most situations, an extra kg of grain fed will not substitute for the intake of silage pasture or crop unless the cows are already being provided with more than they can eat. Therefore their total intake will rise by close to the equivalent of the extra grain provided.
Some of this grain will be channeled into milk production and some to body condition score. How much goes into condition score will depend on a number of factors.
Stage of lactation.
A fresh cow will lose condition score for the benefit of milk production<p>
Level of production
As production rises cows will reach a point where they will start putting some on their backs rather than extra milk if they are well enough fed<p>
Quality of the diet.
If cows have poor quality forage or a low protein diet they will be less able to use the high energy levels in the grain to produce milk<p>
Acidosis.
In circumstances where the fibre level is too low in the diet, extra grain will potentially exacerbate an underlying acidosis problem
Genetic merit of the cow.
Some cows will respond more positively to grain with milk rather than body condition score.
There are many trials that demonstrate different responses to grain over varied situations. There is enough energy in a kg of grain to produce almost 2 litres of milk if all were to be channeled into production, however trials invariably show a lesser response at this time of year. It is reasonable to assume that a cow being underfed in mid lactation is capable of producing an extra litre. Fresh cows may respond more than this whilst stale cows may respond less.
Based on a return of 1 litre for 1kg of grain fed, with the price of cereal grains at 30 cents per kg, it will be difficult on milk production alone to see an economic response until milk reaches 30 cents per litre. This price will be received by most suppliers for a standard 4.2/3.3 test milk at premium quality this autumn once step-ups and productivity incentives are applied.
Body condition score
This season the tendency to reduce grain inputs over spring has resulted in some body condition score loss. This is probably not of great concern unless herds have been fed no grain for extended periods. The repercussions are significant both for animal health and reproductive performance and for production the next lactation.<p>
It takes 200-300 kg of extra feed to put on one extra condition score to a cow in late lactation. If an extra 3kg of grain are fed per day for the last 100 days of lactation then it is likely that cows will dry off one condition score heavier. The response in the next lactation to an extra condition score is to produce at least 10 kg of extra butterfat at no extra feed cost. Therefore the value of extra production next year is around $70 per cow.
Over the next 100 days, if we only receive an average of 27 cents per litre and grain remains at 30 cents per kg, then based on feeding an additional 300 kg per head over that period, we will have lost 3 cents per kg fed or 9 cents per day. This is a $9 loss offset by a gain next lactation of $70.
There are also other factors to consider such as a change in milk and grain price, an early autumn break and the benefits of improved body condition score on reproductive performance and animal health during the next lactation. The economics of this scenario are even more convincing for fresh cows since there is much more at stake.
Summary
Cows should at least be fed to body condition score in late lactation. It is not feasible to think that cows can put on condition in the dry period during the last 8 weeks of their gestation. Unless they are to have a longer dry period, then the ability to more efficiently put on body weight whilst still milking, should be utilised.
Unless there is considerable crop available it is likely that at least 3-5 kg of grain per day will be needed to make up a typical daily intake of 15-18 kg dry matter. If silage quality and quantity is limited it is possible that additional protein will need to be added to the diet to elicit an adequate response.
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Being prepared for an early break
Our seasonal conditions are reminiscent of the last big drought of 1982-83. For those of us here then, the horrors of Ash Wednesday are still clear. None of us would like to see those events repeated however, the seasonal conditions that followed are well worth remembering.
In 1983, the autumn break was substantial and early. The break arrived mid March and above average rains were received for all of autumn. Today's long range forecast is predicting an end to the drought in the north some time in autumn. Such rains often extend down south and provide an excellent opportunity for us to establish new pastures before winter.
Almost every year there is enough rain in late March-April to strike seed. This usually means that all the weeds and annuals are away to a head start. One strategy that has worked without fail in this district is the early sowing of annual ryegrasses into dry seedbeds in late February. Many farmers have the traditional approach of waiting till the soil moisture is sufficient and follow up rains are assured before sowing. This strategy is a wise one for perennial pastures that are much more vulnerable to heat and moisture stress if they are planted and strike with early rains. However the later the sowing, the harder it is to have these new pastures well enough established before winter arrives. Annual rye grasses are much hardier and can sit in a dry seedbed for a long period. This is their natural process as annual species. If good rains arrive in early autumn and annuals are already sown, they will strike immediately and develop to first grazing quickly due to the warm conditions that are still prevalent. If conditions revert back to dry, the are able to withstand the heat and lack of moisture for a long period. The advantage of dry sowing has been demonstrated often by farmers in this region who have done pre and post break sowings. The early sown paddocks are always well ahead of the later paddocks.
Paddocks that have been cultivate in spring for brassica crops can be prepared with minimal tillage after they are finished. Unless the paddocks are very clean, it is worth spraying residual weeds before recultivating. Paddocks to be sown directly form old pasture to annuals can be sprayed out in early February and cultivated and sown by the end of the month. It is not unreasonable to plan to have all annuals sown by the end of February.
Annual varieties
Reproductive Performance
Do you want a tighter calving pattern?Would you like to reduce the number of late cows?
Want to get more cows in calf earlier to AI next season?
Now is the time to look at how this can be achieved next season. The InCalf study identified 6 important factors that have significant effects on herd reproductive performance in many seasonal calving herds. One of these important factors is :
Calving date to mating start date interval
Calving date to mating start date interval has been found to have a huge effect on fertility. To allow all cows in the herd to have a long calving to mating start date interval it is important to achieve a tight calving pattern.
Why is calving date to mating start date interval so important?
The InCalf study found :
- Cows that had calved by the 3rd week of calving had the highest fertility.
- Cows calved in weeks 4-6 of calving had reduced fertility
- Cows calved after week 6 are quite likely too have poor reproductive performance
What can I do to ensure a long calving to mating start interval?
There are three key areas to focus on to achieve a tight calving pattern, they are :
- Heifer Management
- Calve as many first calvers as possible in the first 3 weeks of calving.
- It is achievable to calve 70% by the first 3 weeks and 95% by 6 weeks
- Yearlings must be in good condition and exceed minimum target weights for mating.
- Use adequate numbers of highly fertile bulls, (1 bull per 30 yearlings)
- Purchase Decisions
- Calving dates of any purchased cattle are an important consideration
- Ensure cattle being purchase have reliable estimates of dates of conception
- Place a higher value on cattle that will calve earlier in your calving period, than cattle that would calve later (after the 1st 3 weeks)
- A Planned Approach To Calving Induction
- How do I plan an induction program?
Firstly calving dates need to be obtained by pregnancy -testing the herd. This is best done early. Ideally the herd is pregnancy tested 8-12 weeks after the end of AI followed by a retest of the not in calf cows 6 weeks after mating is completed. This improves the accuracy of aging of the pregnancy. Anytime after the bulls have been removed for longer than 6 weeks is suitable. Once calving dates have been collated, any cows that will calve after the first 6 weeks of calving can be identified for an induction program.
These late calving cows can be induced to calve between 8 and 11 weeks before their natural calving date. For many, this will be within the first 3 weeks of calving. This gives them a much longer calving date to mating start date interval. Cows will have an improved chance of getting in calf early to AI and maintaining their early calving cycle within the herd.
Although it is feasible to induce all late calving cows, there is a higher risk of animal health problems inducing cows over 6 years of age. Studies have also shown that older cows have less ability to make satisfactory gains in their calving time following induction.
This strategy of identifying late calving cows early in the season and planning an early induction program is one of the most effective tools available to improve reproductive performance in a herd.
For more information about inducing cows click here.
back to top
Grain - to feed or not to feed
The inclination to reduce grain inputs this season has been assisted by a favourable winter and spring. Summer is now starting to take its grip and pasture feed is quickly disappearing and being replaced by silage and crops. If summer continues to be dry and hot then most of us will be facing a significant feed shortfall in February and March that is normally offset by grain.Determining the level of grain feeding in the herd that is profitable can be a daunting task. Some farmers make a rash decision to either feed at high levels regardless of the economics, or to pull out grain all together and let seasonal conditions take control of lactation level.
Whatever the decision, it is valuable to make some assessment of the impact of grain or no grain before acting. Some of the factors for consideration are discussed below.
Assessing the return in immediate milk production
In summer and autumn, in most situations, an extra kg of grain fed will not substitute for the intake of silage pasture or crop unless the cows are already being provided with more than they can eat. Therefore their total intake will rise by close to the equivalent of the extra grain provided.
Some of this grain will be channeled into milk production and some to body condition score. How much goes into condition score will depend on a number of factors.
Stage of lactation.
A fresh cow will lose condition score for the benefit of milk production<p>
Level of production
As production rises cows will reach a point where they will start putting some on their backs rather than extra milk if they are well enough fed<p>
Quality of the diet.
If cows have poor quality forage or a low protein diet they will be less able to use the high energy levels in the grain to produce milk<p>
Acidosis.
In circumstances where the fibre level is too low in the diet, extra grain will potentially exacerbate an underlying acidosis problem
Genetic merit of the cow.
Some cows will respond more positively to grain with milk rather than body condition score.
There are many trials that demonstrate different responses to grain over varied situations. There is enough energy in a kg of grain to produce almost 2 litres of milk if all were to be channeled into production, however trials invariably show a lesser response at this time of year. It is reasonable to assume that a cow being underfed in mid lactation is capable of producing an extra litre. Fresh cows may respond more than this whilst stale cows may respond less.
Based on a return of 1 litre for 1kg of grain fed, with the price of cereal grains at 30 cents per kg, it will be difficult on milk production alone to see an economic response until milk reaches 30 cents per litre. This price will be received by most suppliers for a standard 4.2/3.3 test milk at premium quality this autumn once step-ups and productivity incentives are applied.
Body condition score
This season the tendency to reduce grain inputs over spring has resulted in some body condition score loss. This is probably not of great concern unless herds have been fed no grain for extended periods. The repercussions are significant both for animal health and reproductive performance and for production the next lactation.<p>
It takes 200-300 kg of extra feed to put on one extra condition score to a cow in late lactation. If an extra 3kg of grain are fed per day for the last 100 days of lactation then it is likely that cows will dry off one condition score heavier. The response in the next lactation to an extra condition score is to produce at least 10 kg of extra butterfat at no extra feed cost. Therefore the value of extra production next year is around $70 per cow.
Over the next 100 days, if we only receive an average of 27 cents per litre and grain remains at 30 cents per kg, then based on feeding an additional 300 kg per head over that period, we will have lost 3 cents per kg fed or 9 cents per day. This is a $9 loss offset by a gain next lactation of $70.
There are also other factors to consider such as a change in milk and grain price, an early autumn break and the benefits of improved body condition score on reproductive performance and animal health during the next lactation. The economics of this scenario are even more convincing for fresh cows since there is much more at stake.
Summary
Cows should at least be fed to body condition score in late lactation. It is not feasible to think that cows can put on condition in the dry period during the last 8 weeks of their gestation. Unless they are to have a longer dry period, then the ability to more efficiently put on body weight whilst still milking, should be utilised.
Unless there is considerable crop available it is likely that at least 3-5 kg of grain per day will be needed to make up a typical daily intake of 15-18 kg dry matter. If silage quality and quantity is limited it is possible that additional protein will need to be added to the diet to elicit an adequate response.
back to top
Being prepared for an early break
Our seasonal conditions are reminiscent of the last big drought of 1982-83. For those of us here then, the horrors of Ash Wednesday are still clear. None of us would like to see those events repeated however, the seasonal conditions that followed are well worth remembering.In 1983, the autumn break was substantial and early. The break arrived mid March and above average rains were received for all of autumn. Today's long range forecast is predicting an end to the drought in the north some time in autumn. Such rains often extend down south and provide an excellent opportunity for us to establish new pastures before winter.
Almost every year there is enough rain in late March-April to strike seed. This usually means that all the weeds and annuals are away to a head start. One strategy that has worked without fail in this district is the early sowing of annual ryegrasses into dry seedbeds in late February. Many farmers have the traditional approach of waiting till the soil moisture is sufficient and follow up rains are assured before sowing. This strategy is a wise one for perennial pastures that are much more vulnerable to heat and moisture stress if they are planted and strike with early rains. However the later the sowing, the harder it is to have these new pastures well enough established before winter arrives. Annual rye grasses are much hardier and can sit in a dry seedbed for a long period. This is their natural process as annual species. If good rains arrive in early autumn and annuals are already sown, they will strike immediately and develop to first grazing quickly due to the warm conditions that are still prevalent. If conditions revert back to dry, the are able to withstand the heat and lack of moisture for a long period. The advantage of dry sowing has been demonstrated often by farmers in this region who have done pre and post break sowings. The early sown paddocks are always well ahead of the later paddocks.
Paddocks that have been cultivate in spring for brassica crops can be prepared with minimal tillage after they are finished. Unless the paddocks are very clean, it is worth spraying residual weeds before recultivating. Paddocks to be sown directly form old pasture to annuals can be sprayed out in early February and cultivated and sown by the end of the month. It is not unreasonable to plan to have all annuals sown by the end of February.
Annual varieties
Later heading annuals
- Prime 20kg/ha
- Crusader 20kg/ha
- Concord 20kg/ha
- Conquest 20kg/ha
Bi-annuals (> 1 year potential)
- Maverick 20kg/ha
- Feast II 30kg/ha
Early heading annuals
- Tetila 30kg/ha
- Gulf 30kg/ha
The early heading annuals should only be sown into paddocks that are planned for recultivating in early to mid spring. They have little growth potential after the end of October. The later heading varieties will continue vigorous growth well into November. Bi-annuals should only be considered in heavier country. There are not many bi-annuals that perform as well in year two as they did in the first year.
Successfully established annuals have such vigorous early growth that they respond well to nitrogen and provide a substantial feed source to the herd during late autumn.
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Beating the Diamond-backed Moth
This year we have seen relentless attacks on our crops from Diamond -backed moths. Seasonal conditions have been perfect this year for the moth.The traditional use of sprays to control this moth by can be unrewarding. There are a number of reasons for this and it is likely that this problem will be with us more commonly in the future.
The Diamond-backed moth is about 1.5 cm long and brown/fawn colour. It has a 33-day life cycle and is active from early spring to late autumn, permitting it to have up to 7 lifecycles per year. Eggs are laid on the brassica leaves and hatch after 7 days. The grubs go through 4 stages of development before cocooning in preparation for adult life.
The initial damage is evidenced by whitening of the leaf as immature grubs bore into the leaf. This is followed within days by holes appearing. It is during this period that they are most effectively controlled by sprays. It is important to observe the plants so that spraying can be timed to coincide with the early post hatch period before they start eating the plants. Spraying eggs is not successful since the sprays registered for use have little residual effect.
The commonly available sprays are effective at killing these grubs. Resistance is possibly building up due to poor use of the sprays over several life cycles.
Key points to remember when spraying are:
- Time the spraying to hit grubs soon after hatching
- Use an effective dose rate
- Use liberal volumes of water to improve chemical plant contact (at least 300 litres/ha)
- Always use a surfactant to improve contact
- Ideally spray in the evenings and in cooler weather
Infestation of crops is unlikely to be in waves such that they are all at a similar stage, therefore the spray interval can be as short as two weeks instead of monthly to match the life cycle. Crops need to be monitored regularly for eggs.
Sprays used for controlling moths
| Product Name | class of compound | application rate per Ha | Cost per Ha |
|---|---|---|---|
| Fastac | synthetic pyrethroid | 400ml | $25 |
| Astound | synthetic pyrethroid | 400ml | $7.50 |
| Follidol | organophosphate | 700ml | $10 |
| Lorsban | chlorpyrifos | 1.5L | $28 |
There is a chemical called 'mobate' that has claims for improving the effectiveness of sprays such as fastac if added. The product is mollasses based and probably acts as a surfactant as well as supposedly attracting the pests. There is insufficient data available to support this claim. Some biological control methods have been trialed but again there is not sufficient evidence to endorse their use.
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What Does Dry Cow Do?
The 2 main functions of Dry Cow Therapy (DCT) are- To cure existing subclinical mastitis infections.
- To reduce the number of new infections in the dry period and around calving.
How does Dry Cow Therapy work to cure existing infections?
DCT involves infusing an antibiotic preparation into the udder which stays in the udder after drying off.
It is known that cure rates of mastitis infections are increased when a high dose of antibiotic is maintained in the udder for an extended period of time.
Does DCT cure all cows?
No.
How can I tell if a cow is likely to be cured with DCT?
Factors that affect the likeliehood of cure are:
- Age. Younger cows have a higher cure rate than older cows.
- Number of quarters infected. Cows with 1 infected quarter are more likely to be cured than cows with 2 or more infected quarters.
- History:
- Cows that have had 3 or more clinical cases are less likely to be cured
- Cows that had a high ICCC last lactation, were treated with DCT and have a high ICCC this lactation, are unlikely to be cured.
- Type of bacteria: Streps are easier to cure than Staphs.
- Udder scarring: Examination of udders will find some cows with lumps and internal scar tissue from repeated infections. These cows have a reduced chance of responding to DCT.
For example:
- A 1st calver that had 1 clinical case and is infected with Strep. agalactia will have close to 100% cure rate.
- A 4 year old cow that had 1 clinical case and developed a high ICCC towards the end of lactation with Staph Aureus will have a 50-80% chance of being cured.
- A 10 year old cow that had 3 clinical cases in 2 quarters, had a high ICCC last year, has an uneven udder with some palpable scar tissue in the back left and is infected with Staph Aureus, has a less than 5% chance of being cured, even if she does give 45 litres!
Does DCT prevent mastitis?
We know that one of the high risk periods for cows becoming infected is during the dry period, especially just after drying off and just round calving. DCT at drying off will reduce the number of these new infections that occur during the dry period. Depending on the type of product used and the length of time the cow is dry, it will also reduce the number of new infections around calving.
It is important to note that DCT will not prevent infections by the types of environmental bacteria that may be introduced into the udder when infusing the DCT.
How do I know that a cow is infected with subclinical mastitis?
Mastitis is caused by bacteria entering the udder. We can determine this by culturing a sample of the milk. Culturing, while an important tool for investigating mastitis in herds, is impractical as a whole herd test. Individual Cow Cell Counts (ICCC's) are considered the best method available to determine whether cows have subclinical mastitis.
A cow is considered to have a subclinical infection if she has had an ICCC above 250 000 cells /mL at any time during her current lactation. At least 4 ICCC's are required to be confident of a cows status.
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Differences between Dry Cow Products
| Active component | Name | Duration of Action | Minimum Dry period |
|---|---|---|---|
| 500mg Cloxacillin | Orbenin DC, Noroclox | Medium | 30 days |
| 600mg Cloxacillin | Enduro,Duro Dry | Long | 35 days |
| Cephalonium | Cepravin | Very Long | 49 days |
In General cure rates are probably superior with 600mg products versus 500mg products and prevention of new infections extends longer with the longer acting products.
It is important to keep in mind the minimum dry periods of each product. Ensure cows are dried off to allow adequate dry periods for the dry cow product that is used, bearing in mind some cow may calve up to 2 weeks prior to there due date.
The product that bests suits your herd and farm is a decision which can be made looking at farm history, clinical case records, herd test figures and milk culture results in conjunction with one of our vets.
What information do I need to help choose which Dry Cow Product to use?
- Herd average BMCC for the past 12 months
- Clinical Case Records
- Herd test ICCC summary for all cows in herd
- Results of any milk cultures taken from your herd (will be on file at clinic)
Should I use Dry Cow on the whole herd (Blanket DCT) or only on some of the herd (Selective DCT) ?
The decision to use selective or blanket is based on a number of factors. Click here to see a flow chart to help with this decision.
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Teatseal
What is Teatseal?Teatseal is a new non antibiotic product which is infused into the teat at drying off. It is composed of Bismuth in a paraffin base and sits in the teat canal, remaining there without hardening until it is removed by suckling or manually stripping the quarter. It does not have any curative affect on infected quarters.
If it doesn't cure infected quarters, why is it of benefit?
We know that the ability of the teat to form a solid plug after drying off is extremely important in preventing infection during the dry period. The plug acts as a physical barrier to bacteria. The vast majority of quarters that become infected during the dry period are quarters that fail to form an effective plug. Some of these infections are obvious as swollen quarters during the dry period, but many do not become obvious until after the cow calves. Typically, 50% of quarters are still "open" seven days after drying off and 5% never close.
How does the preventive effect of Teatseal compare with that of DCT?
Overseas studies (United Kingdom and New Zealand), have shown that Teatseal is better than no treatment and as effective as antibiotic DCT, in preventing new infections in the dry period. It is likely that for the most part these results will be seen here. There are however, differences between our systems that suggest that we need to closely monitor the results and determine what factors are important for success. Examples of the differences are, greater production level at drying off Compared to NZ and a greater prevalence of E. Coli bacteria in UK herds.
How can I find out more about the use of Teat seal?
Due to the potential importance of this product in a market continuing to demand "clean" product and the sometimes complex factors in deciding if it should be used in an individual herd, it is best to discuss your situation with one of our vets.
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