Most New Zealand herds have some cows that are too thin at calving. They may also have some cows that are too fat at calving and lose too much body condition in early lactation. Both are problems that reduce reproductive performance.
Hitting body condition score targets is important
Cows calving in body condition score (BCS) 5.0 for mature cows, and 5.5 for first and second calvers, have substantially better reproductive performance than cows in lower body condition.
Losses of one body condition score can be expected in early lactation, and cows calving at BCS 5.0 and 5.5 targets will likely be condition score 4.0-4.5 at Mating Start Date.
Cows that calve in low condition score (4.0-4.5) may lose less condition but end up at condition score less than 4.0 at mating. They produce less milksolids, take longer to start cycling and their reproductive performance suffers.
Excessive losses of condition score (1.5 scores or more) can occur when cows calve in body condition score above 5.5, reducing their reproductive performance. First calvers are at risk of losing more than one condition score, but as long as they calved early, and are gaining condition prior to Mating Start Date (MSD), they have every chance of getting back in calf early.
Managing body condition score is all about managing your herd’s nutrition and lactation programme. Condition scoring at critical times throughout the year lets you know if you need to consider changing herd nutrition or shortening lactation of some cows.
Herd managers need to regularly track against budget all aspects of feed and nutritional management. The allows you to anticipate and detect problems early and take action to avoid excessive loss of condition and reduced reproductive performance.
When to body condition score
Regular condition scoring will allow you to monitor nutritional trends and provide sufficient warning to take action even 6 months before poor condition reduces reproductive performance.
Monthly checks using the scoring sheet in Body Condition Scoring Made Easy or the BCS tracker app, are recommended in late lactation and dry period. Record and monitor your first and second calvers' profile separately from the mature cows.
If you wish to condition score at the most important times, they are:
- After the end of mating, before dry summer/autumn conditions reduce pasture quantity and quality;
- In late lactation (90-150 days or 3-5 months) before Planned Start of Calving date;
- Just before Planned Start of Calving date;
- At this time, calculate the average condition score for at least 70 cows per mob selected at random, the percentage below and above 5.0 for mature cows, and the percentage below and above 5.5 for first and second calvers.
- Two weeks before Mating Start Date;
- at this time, calculate the average condition score for at least 70 cows selected at random, and the percentage below 4.0.
Also calculate the difference in condition score from calving to 2 weeks before the start of mating.
To maximise herd reproductive performance, every farm must have a strategy in place to effectively assess body condition score. You may want to implement your own system of regular condition scoring, using the procedure suggested in Body Condition Scoring Made Easy. Alternatively, get a Certified BCS Assessor who is condition scoring cows on a regular basis to perform this task.
Once you have a system in place to measure body condition, then feed budgets, milking frequency and drying-off plans can be developed to achieve body condition targets while milksolids productions targets are also met.
A sound BCS programme allows you to meet herd targets
- Not more than 15% of mature cows are below body condition score 5.0 at calving and not more than 15% of mature cows are above body condition 5.0 at calving;
- Not more than 15% of first and second calvers are below body condition score 5.5 at calving and not more than 15% of first and second calvers are above body condition score 5.5 at calving;
- The average decrease in body condition score for the herd between calving and mating is not more than 1.0;
- Not more than 15% of cows are below body condition score 4.0 at mating; and
- Cows maintain or gain body condition from the commencement of mating.
Make sure the farm system feed supply and demand are balanced and that your cows are well fed.
Herd managers need to regularly track against budget all aspects of feed and nutritional management. This allows you to anticipate and detect problems early and take action to avoid excessive loss of condition and reduced reproductive performance.
When considering changes to nutritional management, you need to think about the whole farm system:
- What are the likely benefits now and further on?
- Will these benefits outweigh the costs involved?
- Will there be added costs in terms of time or extra labour?
- Will this change affect other parts of the farm?
Negative Energy Balance
When a cow’s energy demands for lactation, maintenance and activity aren’t met by dietary intake, a negative energy balance (NEB) occurs. A cow in NEB is forced to mobilise its fat and muscle to provide energy to meet the deficit.
All cows enter into a state of NEB for six to eight weeks after they’ve calved, but it is important that they have stopped losing condition and are in a state of positive energy balance before the planned start of mating. There is very little that can be done in the first 4 – 5 weeks after calving to prevent BCS loss, and the biggest driver of BCS loss after calving is BCS and feed management pre-calving.
Reducing the impact of NEB for mating
To more information on meeting feed requirements see FeedRight.
Cows and heifers that are below target BCS coming into mating should be identified, and management strategies implemented to ensure they are in a positive energy balance through the mating period. Milking these cows once a day for several weeks, while ensuring adequate energy intake, will support a positive energy balance situation.
Even if cows continue to be milked twice daily, identifying and separating any younger, thinner cows from the main herd and preferentially feeding them with good quality pasture and supplements, if necessary, will remove competition from older, more dominant cows and improve energy status and BCS. This will increase the potential for a more successful mating result.
If cow BCS and pasture residuals are on target, adding supplements to the diet will not improve reproduction. However, if you do need supplements, use good-quality supplements that are free from spoilage.
There’s no reproductive benefit of feeding high-starch supplements, such as grains, compared with high-fibre feeds (e.g. PKE or pasture silage; see our article in last month’s Inside Dairy). Therefore, your decisions on supplement type should be based on the cost/benefit of the predicted milksolids response.