A Very Specific System

Transcription

1 Evaluating the advantages of block-calving Establishing the targets required to maintain a block-calving pattern Examining specific management requirements. Objective: To establish the key factors to maintain a successful block-calving system. Challenge: Recognise the need for excellent fertility performance and management for a true block-calving system. Set specific fertility improvement targets for your herd based on objective measurements of current performance. A Very Specific System Regardless of the season of calving, all block-calved herds share the same need for rather different fertility management targets to herds without a distinct seasonality of calving. This is due to their over-riding priority on maintaining a particularly tight calving pattern. The discipline of block-calving can be very positive for fertility but it does require a certain attitude of mind, coupled with a commitment and ability to cope with intensive periods of calving and breeding activity in particular. Target Achieve a Six-Week In-Calf Rate of 75% and Failure to Conceive Culling Rate of under 8% Block-Calving Suitability Page 9-1 Block-Calving Targets Page 9-2 Block-Calving Maintenance Page 9-4 3:10/07 9

2 Action Plan To achieve a Six-Week In-Calf Rate of 75% and Failure to Conceive Culling Rate of under 8% Assess Block-Calving Suitability Review the extent to which block-calving is suitable for your herd Set Clear Block-Calving Targets* Establish realistic targets for your key block-calving herd fertility measures, appreciating the interrelationships between them Maintain Your Block-Calving Pattern Fine-tune key aspects of your record-keeping, team approach, heat detection, herd nutrition and management to maintain the required calving pattern. Page 9-1 Page 9-2 Page 9-4 * See Section 5 for All-Year Calving Herds 3:10/07 9

3 Block-Calving Suitability There are a number of well-recognised advantages to maintaining a consistently tight annual calving pattern. Most notably: The attraction of being able to effectively shut down the unit for a few weeks each year when the cows are dry allowing holidays to be taken, and maintenance and repairs to be unhindered by routine jobs A total focus on the specific priorities of calving, breeding, drying-off and transition cow management in turn reducing the pressure of different seasonal needs and improving the prospect of success in each Easier matching of the specific nutritional needs of the majority of the herd at any time, especially at grass enabling feed planning and supplementation on more of a herd than individual animal basis, and reducing the complexity of feeding management The ability to run the whole herd as one avoiding the need for different calving groups, switching of cows between groups, and the fertility-harming stress this can cause (Sections 6 and 8) Simplified heifer rearing, with replacement animals all born at the same time and reared as a single group with a minimum spread of weights and ages improving the effectiveness of rearing heifers to meet the required breeding and calving targets (Section 10) Better use of veterinary and feed adviser resources over a shorter, more intensive period giving more focus to the fertility team (Section 4) and potential economies in the number of visits required. Most importantly, block-calving offers the opportunity to improve fertility through a total dedication to achieving the correct body condition in early lactation and maximising accurate heat detection in the breeding season. Assessing Block-Calving Suitability The key fertility-related factors to consider in establishing whether block-calving is suitable for a particular herd are: The track record of the current system through an objective appraisal of present performance against key targets The extent to which the management system allows the potential for improvement through focused fertility action to be exploited for which the basics must be in place The ability of dairy staff to take the pressure of intensive calving and breeding seasons crucially as far as heat detection is concerned The support available from the veterinary practice and other advisers especially during the intensive calving and breeding seasons (Section 4) The state of record-keeping. Accurate and up-to-date records are an essential resource in targeting activities and achieving targets for large herds in particular (Section 3) The extent to which all concerned are happy to manage animals as a herd rather than as individuals. The particular requirements of the milk buyer as far as seasonality of milk supply is concerned are also an important consideration in deciding whether block-calving is suitable, as may be lifestyle and other personal priorities. Block-calving is unlikely to be appropriate where: Milk yield is the over-riding objective and the herd is high yielding or of particular genetic merit The focus is on individual animals and the ruthless culling required to maintain the calving pattern might be compromised Grazed grass or other forages are of poor quality and can not be matched to the needs of a large number of cows at the same stage of lactation without excessive use of purchased concentrates Record-keeping and target-setting are not a high priority and any slippage in calving pattern can easily go undetected for an extended period There is any reluctance to commit 100% of effort and resources into an intensive period of heat detection Two-year calving of heifers cannot be achieved (Section 10). 3:10/07 9-1

4 Block-Calving Targets There is a clear difference in fertility targets between herds with and without pronounced seasonal calving patterns. Maintaining the calving pattern is the top priority for block-calving herds, presenting a number of distinct challenges if the Failure to Conceive Culling Rate is to be contained within reasonable bounds. In herds with an extended calving pattern individual cows may be allowed as many as seven or eight oestrus cycles to get back in-calf, the impact of the extended Calving Interval being masked by the already wide spread of calvings. Block-calving herds simply do not have this luxury. A similar Fertility Factor can, of course, be achieved by different combinations of Heat Detection and Pregnancy Rates 60% heat detection and 40% pregnancy producing the same Factor as 40% heat detection and 60% pregnancy. The relationship between the number of oestrus cycles available, the Fertility Factor and the resulting Failure to Conceive Culling Rate is particularly important to block-calving herds (Figure 9.1). Figure 9.1: Oestrus Cycle Availability and Failure to Conceive Culling Rate at Three Levels of Fertility Factor 50 A 90-day calving period allows a maximum of four 21-day oestrus cycles in which to correctly detect heat and establish pregnancy, while a 60-day calving period means only three cycles. Failure to Conceive Culling Rate (%) It has to be accepted that, regardless of their individual value, later calving animals will have fewer opportunities to achieve a new pregnancy within the required timescale, and may have to be culled if the calving pattern is to be maintained. The critical factors determining fertility success in block-calving herds are: Heat Detection (or Submission) Rate Pregnancy Rate. Multiplying these two rates produces a single measure of particular value in block-calving herds the Fertility Factor (Table 9.1). Table 9.1: Heat Detection and Pregnancy Rates and the Fertility Factor Heat Detection Rate (%) Pregnancy Rate (%) Fertility Factor (%) Maximum Number of Oestrus Cycles 20% Fertility Factor 30% Fertility Factor 40% Fertility Factor Source: Esslemont and Kossaibati (2002) British Cattle Breeders Club Annual Conference. A low Fertility Factor of 20% in a herd with only three or four oestrus cycles available results in a clearly unacceptable 40-50% Failure to Conceive Culling Rate Under the same conditions a Fertility Factor even as good as 30% (representing a 60% Heat Detection and 50% Pregnancy Rate) would lead to a 20-30% Failure to Conceive Culling Rate which is also excessive A high Fertility Factor of 40%, on the other hand, implies a much more acceptable Failure to Conceive Culling Rate of 20% for three cycles, rapidly falling to around 10% by four cycles. Source: Esslemont and Kossaibati (2002) British Cattle Breeders Club Annual Conference :10/07

5 Setting the Key Targets If the Fertility Factor is low there is no way block-calving can be practicable given the need to achieve pregnancy within three or four oestrus cycles. It is only when the Fertility Factor reaches 40% that a viable Failure to Conceive Culling Rate is possible within the constraints of the required Calving Interval. The target Fertility Factor of 40% or more can most effectively be achieved through a number of primary physical targets focused on heat detection and pregnancy (Table 9.2) resulting in several target outcomes (Table 9.3). Fundamental to success, of course, is the maintenance of a strict service start date and an equally strict cut-off date beyond which cows will not be served. The Calving to First Service Interval will be slightly longer for the earliest calving cows to prevent them advancing their calving date, and shorter for the later calvers to prevent time losses. Table 9.3: Target Outcomes for Block-Calving Herds Calving to Conception Interval (days) Calving Interval (days) Percent Conceiving of Calved (%) > 87 Percent Conceiving of Served (%) > 93 Days Open Failure to Conceive Culling Rate (%) < 8 6-Week In-Calf Rate (%) > Day Not-In-Calf Rate (%) < 8 One of the single most valuable means of monitoring performance within block-calving herds is the Six-Week In-Calf Rate (Section 2). The Six-Week In-Calf Rate is particularly valuable for providing early feedback on the success of the service campaign. While the 100-Day In-Calf Rate is of more value for non-seasonally calving herds, since it extends beyond the end of the defined service period it is of no practical use for block-calvers. Achieving the target Six-Week In-Calf Rate fundamentally depends on achieving the right combination of Submission and Pregnancy Rates (Table 9.4). Table 9.2: Primary Physical Targets for Block-Calving Herds Voluntary Waiting Period (days) A set calender date Submission Rate (%) 90 Calving to First Service Interval (days) 65 Pregnancy Rate to First Service (%) > 55 Return to Service Detection Rate (%) > 80 Overall Pregnancy Rate (%) > 55 Assumed Pregnancy Rate (%) > 65 Table 9.4: Six-Week In-Calf Rates from Different Submission and Pregnancy Rates Submission Pregnancy Rate (%) Rate (%) Source: Recent Research in Dairying (2002), Agricultural Research Institute of Northern Ireland. The target Six-Week In-Calf Rate of 75% requires a Pregnancy Rate in excess of 55% combined with a Submission Rate of more than 80%. 3:10/07 9-3

6 In Australia, where block-calving is particularly important, the key relationship between Submission Rate and Six-Week In-Calf Rate has been defined through detailed herd monitoring (Figure 9.2). Figure 9.2: The Relationship Between Six-Week In-Calf Rate and Three-Week Submission Rate Six-Week 60 In-Calf Rate 40 (%) 20 The 31 best performing herds all had Three-Week Submission Rates between 75% and 95% Block-Calving Maintenance A number of specific record-keeping, planning, heat detection, nutritional and other management considerations are particularly important in maintaining a successful block-calving system. Identifying Critical Records Good record-keeping (Section 3) is vital in block-calving herds Source: In-Calf (2000) Dairy Research and Development Corporation, Australia. Costing the Benefits Three-Week Submission Rate (%) In terms of Failure to Conceive Culling Rate losses alone (Section 5) the financial impact of anything other than excellent fertility performance in block-calving herds is clearly disastrous (Table 9.5). To this, of course, must be added the cost of disruptions to the production system, heifer rearing and breeding programme. The most important essentials are: Daily diary Three-week breeding diary CuSums for Submission Rates Breeding charts CuSums for Pregnancy Rates Computerised records where possible Body Condition Scoring at critical periods. Planning the Approach Table 9.5: The Cost of Poor Fertility in Block-Calving Herds Fertility Factor 40% Fertility Factor 20% Difference Three Oestrus Cycles Available Failure to Conceive Culling Rate (%) Cost ( /100 cow herd) 19,840 Cost (p/litre) 3.31 Four Oestrus Cycles Available A multi-disciplinary team of farm staff, veterinary practitioner, nutritionist and adviser (Section 4) is likely to be most cost-effective in block-calving herds. Team activity will be more focused over a shorter period of time, with meetings required fortnightly on occasions. The more concentrated effort required may reduce overall team and veterinary costs. Failure to Conceive Culling Rate (%) Cost ( /100 cow herd) 17,360 Cost (p/litre) 2.89 Source: Esslemont and Kossaibati (2002) British Cattle Breeders Club Annual Conference. Fact Sheet 3 details the calculations and assumptions behind the fertility costings 9-4 3:10/07

7 Managing Heat Detection Optimising Herd Nutrition As the most significant contributor to success in block-calving herds, heat expression and observation (Section 6) require particular management attention. Achieving precisely the right energy intake (Section 7) is much more significant when success depends upon getting every animal possible pregnant in a few specific weeks. Key requirements include: Allowing sufficient time for cow observation Designating three to four 30-minute observation periods a day, one of these after 10pm Providing more and dedicated observation resources over the most critical periods Ensuring housing and floor conditions do not interfere with bulling activity Avoiding lame cows Achieving Body Condition Scores of at calving, and condition score losses of less than 1 (preferably 0.5) between calving and service. Heat detection aids have an especially significant role in block-calving herds given the concentrated pressure on heat detection. In particular: Accurate cow identification is a must Diaries and charts have a key role Everybody involved needs a three-week breeding diary Tail-paste or heat mount detectors should be used A vasectomised or penned bull can be very useful A natural service bull should be run with the herd after the first two service cycles Pedometers should be considered Progesterone assays are very valuable and their cost-benefits much more attractive Pregnancy diagnosis is essential. Key considerations include: Targeting late-lactation, dry cow and early lactation feeding to achieve Body Condition Scores of at drying-off and calving, and at service Avoiding very thin cows at service Ensuring nutritionists and computer rationing programmes place sufficient emphasis on feeding for fertility as well as production Measuring early lactation intakes and milk proteins alongside body condition to ensure energy supplies are not compromised Avoiding all ration changes during the service period Serving as many cows as possible before turnout and making the transition to grass gradual over at least two weeks if it coincides with the breeding season Addressing any dietary protein shortfalls with supplementation two weeks before the start of the service season, taking particular care not to increase levels of quickly degraded protein immediately prior to the service period Correcting any identifiable mineral deficiencies. Fact Sheet 11 sets out the latest thinking on Transition Cow Management 3:10/07 9-5

8 Addressing Herd Management Attention to the non-nutritional factors affecting Pregnancy Rate (Section 8) is also more critical in block-calving herds. Key considerations include: Minimising the incidence of lameness ahead of the service period Keeping a few extra replacements in the pipeline if herd age is advancing to account for lower Pregnancy Rates in older animals Selecting the highest possible fertility bulls and, in some cases, even introducing an element of cross-breeding to boost inherent fertility levels Preparing AI facilities and service management plans well in advance of the service period Taking particular care with DIY AI, given the average 2-4% lower success rates than technician service, and re-training inseminators who may have got out-of-practice in the nine-month gap between the end of one service season and the beginning of the next Examining the extent to which technician-ai can allow farm staff efforts to be concentrated on heat detection, particularly where large numbers of animals to be served within a short season permit a regular AI call programme Using a natural service bull as a routine after the second oestrus cycle or as soon as it appears likely that all replacement requirements have been satisfied Assessing the value of oestrus manipulation and controlled breeding programmes to increase Submission Rates; synchronise heifers calving into the herd; and bring into line early and late-calving animals. Oestrus synchronisation programmes (Section 8) can be especially valuable in block-calving herds in view of the far greater improvement in Pregnancy Rates achieved by the same improvement in heat detection within 45 days (six weeks) of the start of the breeding season rather than the day period more appropriate for all-year calvers (Table 6). Table 9.6: Increased Proportion of Cows Pregnant Using Oestrus Synchronisation at Different Underlying Heat Detection and Pregnancy Rates Heat Pregnancy Rate (%) Detection Rate (%) Days After Onset of Breeding Source: Diskin and Others (2001) BSAS Occasional Publication 26. The MDC breeding+ programme provides practical advice on improving herd profitability through breeding 9-6 3:10/07

9 Summary Block-calving is a very specific system with particular demands There are distinct advantages of a block-calving approach, but it demands total dedication to excellent fertility performance Target Heat Detection Rate and Pregnancy Rate expressed together as a Fertility Factor should exceed 40% Submission Rates need to exceed 75% to achieve the desired fertility The main potential loss of failing to achieving the standards is a high Failure to Conceive Culling Rate Anyone contemplating block-calving needs to ask some rigorous and honest questions of themselves and their resources Managing and maintaining a block-calving pattern requires sufficient resources to be focused on key targets at the correct time. See also The MDC breeding+ programme provides practical advice on improving herd profitability through breeding Section 2: Section 3: Section 4: Section 5: Section 6: Section 7: Section 8: Defining Your Terms Identifying Critical Records Planning Your Approach Establishing Your Starting Point Managing Heat Detection Optimising Herd Nutrition Addressing Herd Management Section 10: Managing Heifer Rearing Section 11: Fact Sheet 3: Fertility Costs Fact Sheet 11: Transition Cow Management 3:10/07 9-7