How to hit replacement heifer targets

For most parts of the country, grassland management has proven a struggle to date this year, given the contrasting rain levels between early and mid/late summer, contributing to sporadic periods of sustained high growth rates.

However, as we approach the later quarter of the grazing season, it is important to maximise perfomance off grass, while also setting the platform up correctly for Spring 2024. As always, we’re hoping to control the decline in milk production from here to the end of lactation. Milk yield in normal conditions will drop off 2.5% per week or 10% per month once we get to mid lactation.

Energy Deficit  

Any drop greater than this indicates an energy deficit, which would signal deteriorating grass quality or where a deficit occurs, the herd’s dry matter intake capacity may not be being met. However, milk protein and butterfat should be incrementally increasing at this point, with the target being at least +0.05% per month. Milk protein is energy based and where grass quality has suffered, summer milk protein percentages have been similarly impacted.

Next Generation

It is also a good time to reassess where we stand with the next generation of milking cows – that heifers are still on track to achieve their target weight for age (% of mature weight). Weighing now compared to weighing at the point of housing provides the opportunity to identify heifers that are behind target, and to make alternative plans where these targets are not being met.

The threshold figure for 2022 spring born weanling heifers is approximately 198kg in mid-September (33% of an assumed mature weight of 600kg). Heifers that are lighter than this should be separated into their own group and given priority access to high quality grass and supplementary concentrates (depending on how below target they may be).

Higher weight gains can be achieved from grass rather than from winter/silages diets and a good response to autumn supplementation can be achieved. Research shows that youngstock at grass in summer can achieve weight gain of 0.85kg/day on grass only. While in the autumn where 1kg of concentrate plus high-quality grass is offered, Average Daily Gains of 1kg/head/day can be achieved.

For more information, contact your local Agritech Sales Advisor.

Hitting target weights at certain milestones is crucial to ensure replacement heifers are on course to achieve the main goal of being 60% of their mature weight when bred at 15 months.

Meal feeding at grass

Transitioning calves from a milk-based diet to a grass-based diet can be tricky. Spring born calves that are weaned and now at grass, should be offered supplementary concentrates in the diet for 4-6 weeks minimum, to ease with the transition onto a grass-based diet.

Where 102kgs concentrate is offered at grass for the first number of weeks, this reduces the total amount of fresh grazed grass in the diet and avoids hungry calves over-indulging on lush low fibre, high N grass; resulting in what is often referred to as ‘summer scour’.

Alongside offering concentrates, fibre sources can also be offered in the diet (e.g., straw/hay/roughage) through this transition, as well as turning calves into slightly heavier covers. We must remember young calves are not fully developed ruminants yet and high quality lush grass may not be the best forage for supporting rumen development.

Target weights

Weighing scales are by far one of the most under-utilised management tools on farm. Timing of weighing can also be beneficial. By weighing in the weeks pre-housing, compared to weighing at the point of housing, allows farmers to identify heifers that are behind target. The best advice is to group accordingly and make alternative plans for those heifers under target weights.

The threshold figure for 2023 spring born weanling heifers is approximately 200kg in mid-September (33% of an assumed mature weight of 600kg). Heifers that are lighter than this should be separated and given priority access to the highest quality grass and re-introduce concentrates depending on their weight relative to the herds target.

Further information: 

For more information, contact your local Sales Advisor.

Firstly, weaning should only ever occur once calves are consuming at least 1.5 kg of concentrate per head per day in group scenarios. Alongside this, gradual weaning is advised to minimise stress levels in young calves and to allow them to increase dry matter intakes over a prolonged period.

During the first grazing season, heifer calves should have a good consistent growth rate of 750g /day or 20kg/month. Calves should always have access to high-quality grass, and depending on target weight gain and grass availability, a quality concentrate supplementation may be required. Typical advice is to feed meal at least 6 weeks post-weaning/turnout and reintroduce meal again in autumn if desired weights are not being met.

Setbacks that occur now or over the first grazing season will result in heifers struggling to meet target weights in the future and can result in these heifers not making it to the parlour.

What is Summer Scour? 

Year on year, in the proceeding weeks after turnout to grass, cases of calves suffering from setbacks are reported, typically described as Summer Scour Syndrome or calf wastage.
Lush grass is very high in oils like CLA (conjugated linoleic acid), sugars and potentially nitrogen, and to a young undeveloped rumen this can be hard to adjust to. In addition, low covers of grass have very little fibre, which is a key substrate for good rumen health.

It’s often asked why Summer Scour Syndrome was not an issue until recent years, and the short answer is that we are victims of our own success. Grassland management has dramatically improved over the past number of years. Calf rearing has also improved, and we are typically weaning calves at 8-10 weeks of age. It is also worth noting that ditches are now typically fenced off to youngstock where historically they would have been used as a source of fibre by calves.

In severe cases or if prolonged, rumen function can be severely impaired and B vitamins may no longer be manufactured by the rumen, resulting in blindness and ‘star-gazing’.

Note: Where poor thrive/scouring is an issue at grass post-turnout, Coccidiosis should be the first port of call to rule out.

Avoiding the issue: 

Ideally, the rumen is developed over the milk feeding period/pre-weaning by offering ad lib access to concentrates (18% Crude protein crunch/nut), and clean fresh straw to reduce your risk of Summer Scour Syndrome.

Below are several management practices that can help combat against the onset of Summer Scour Syndrome symptoms this season, a few which will be farm/system dependent:

1. Offering concentrates in the weeks post-turnout will help to avoid overindulging on rapidly digestible lush grass. Hungry calves are more likely to gorge on lush covers.
2. During periods of rapid growth, avoid letting calves into low covers of grass. Until rumens are well developed and luxury uptake of nitrogen is not a problem, target covers of at least 1,200-1,400 kg DM/ha for 8-10 weeks after turnout.
3. The use of Agritech’s Rumicare in meal pre and post-weaning will help the buffering capacity in the rumen, decrease the risk of acidosis/ruminal upsets during the transition period and promote positive bacteria populations in the rumen (typically included at 2%).
4. Give access to grass and indoor accommodation simultaneously prior to full-time turnout to ease the transition to grass.
5. Offer a fibre source post-turnout. Round feeders are an option to allow access to clean dry straw.
6. Use strip-wire allocations. Strip-wires allow for less selective grazing and force calves to eat stem content along with the leaf.

More Information: 

For more information on reducing the stress of weaning on your calves, contact your local Agritech Sales Advisor.