Heifer Weighing

Heifer growth should be measured by liveweight, the only objective measure of dairy heifer performance. Weight performance is also useful to inform working relationships between stock owners and the heifer grazier.

Weighing frequency

Weighing systems and weigh scales are essential for heifer management. Good practice for weighing is every 4-8 weeks, a minimum of every 12 weeks.

Younger heifers can benefit from monthly weighings because the necessary growth rates are a higher percentage of body weight at a young age.  If heifers fall behind weight early it can be difficult to get them back on track.  To achieve target weights heifers should double their weight in the first 3 months of life and double it again over the next 7 months.

Key times for weighing

• Arrival or exit of a property.
• At 12 months of age to check they are on track for achieving puberty pre-mating.
• At the start of mating as a management review.
• 20 months to check that stock are on track to meet 22 month Lwt and BCS targets.

Grazing contracts should stipulate weighing expectations, reporting and actions for underweight animals.

Weighing system

Ideally every weighing event should be approached with a similar process.  There is not a prescribed method for weighing but these key aspects should be consistent:

• Accurate scale. Weigh a ‘known weight’, such as a 25kg bag of meal.
• Time since fed. Weigh full, 2-3 hours after fresh feed.
• Time in yard. No more than two hours in the yard, if animals are off feed longer than normal or previous weighing use the results with caution.
• Changes in diet. Important if weighing events are less than 4 weeks apart.

Weight variation can be influenced by “Gut Fill” which can account for up to 22% of a heifer’s liveweight.

Factors that influence gut fill:

• water access and water quality
• feeding levels and supplement as a high percentage of the diet
• time since feed and/or water access
• quality of feed and rate of passage, higher quality feed is digested faster
• effect of a weather event on feed intakes and utilisation.

Heifers grazed on forages have heavier rumen contents than animals with concentrates (e.g. grain or meal) in the diet. Gut fill can decline by 40% over 12 hours and 60% after 24 hours after being off feed.

Identifying poor animal performance

There are two ways to identify animal performance: visually and through weight. Visual assessments should never replace weighing. Both methods have value, heifers can be weighed on a monthly to three monthly basis and should also be observed daily to multiple times a week. Visual observation may detect issues between weighings.

There are four different uses for weight data:

• Mob liveweight relative to target liveweight
• Individual liveweight relative to target liveweight
• Mob growth rate compared to targeted growth rate
• Individuals growth rate compared to mob growth rate

Poor performance of the whole mob

• If more than 30% of animals are below the minimum then the whole mob has fallen behind.
• If expected heifer growth rate is significantly behind expected growth rate.

Possible causes for many animals being behind target weights:

• Feed allocation or poor utilisation.
• Low quality feed offered.
• Energy loss to environmental conditions e.g. shivering, muddy coats, etc.
• Animal health issues and ill-thrift.

Poor performance of a tail end of the mob

A 'tail end' in a mob of heifers is a situation where there is a greater than expected (10-30%) number of animals lighter than targeted weight range.

If a group of heifers has a tail end, then assess whether the group should be preferentially treated or if the corrective action will be applied to the whole mob.

Possible causes for a tail end:

• animal health or ill-thrift in a small group
• some animals not competing within the mob
• issues from calf rearing or not meeting weaning criteria
• rearing late born animals.

Poor performance of individuals

When assessing individual heifer performance (less than 10% of the mob) it is important to judge the individuals by:

• breed type
• birth date
• calf rearing and/or meeting weaning criteria
• historic liveweight and past growth rates.

Birth date and weaning policy can increase the range of liveweights in a mob. Late born heifers may need heavier weaning weights or priority care to meet mob liveweight targets.

Poor performing individuals are easily identified with multiple weighing events, lesser liveweight or growth rate compared to the mob. Poor performing individuals may also show signs of illness or injury.