Table 1. Heifer herd size for a 100-cow herd and a 10% heifer cull rate


Cull Rate (%)


26 30 34 38 42


Source: Penn State


When age at first calving increases, so does the need for heifer housing, feed, labour, and management. This increase in input variables can be as much as 50% or


22 53


61 69 77 86


Age at First Calving (months)


24 58


66 76 84 93


26 63


72 82 92


101


28 67


78 88 99


109


30 72


83 94


106 117


possible


• Clean and rest calf pens • A calf should always have a dry bed • Concrete floors should have a 1:20 slope to allow effective drainage


• Minimise levels of airborne infections, there should be four changes of interior volume of air an hour, look at air movement and in and out flows of air, when necessary consider tube fan ventilation


• Minimise condensation and reduce humidity with better ventilation as above


• Aid evaporation from urine and faeces, bedding and water spillage, ensure good drainage with a 40cm deep gravel base and 10cm drain tile


• Remove water vapour


• Reduce dust levels • Create even air distribution • Reduce heat stress


Purchasing cattle


Table 2: Replacements required to maintain a constant 100 cow herd size


Herd turnover rate (%)


26 38


Source: Penn State more in extreme situations. See table two.


B - Space required • Ensure enough housing is available for pre-weaned calves – individual or group housed


• Weaned heifers should have 46cm feed space/heifer


• By 12 months of age allow 60cm feed space/heifer


• Avoid overstocking • Provide a minimum 1.5m2


of floor space


Table 3: Minimum space allowances for calves in group housing


Calf weight


Less than 150kg 150kg to 200kg Over 200kg


- see table three, and 6m2 space depending on age


Minimum space per calf


1.5m2 2.0m2 3.0m2


Source: Penn State / Advanced Nutrition to 10m2 of air


Finally, don’t forget to include any heifers that are to be produced for sale or breeding purposes.


C - Environment • Calves more than eight weeks old have to be loose housed


• Calf pens should be easily dismantled for cleaning


• Use an all in / all out policy whenever THE JOURNAL FEBRUARY 2015 99 Age at first


calving (months) 22 30


Replacements required


53 106


When you plan to buy in cattle to either widen the genetic pool or simply to make up numbers, then do not ignore potential disease impact.


Investigate the status of both the herd and individual animals for Johne’s, BVD, Lepto and IBR at least. Be aware of and understand the risks and methods of prevention before you start. For example, Johne’s visual symptoms may not impact for several years following infection; when heifers are homebred then whole batches can be lost to this disease in second or third lactations. Johne’s can also impact on SCC, fertility and


reduced production.


If you want to keep your herd moving forward and in profit, then consider these bottleneck areas as priority, thinking of milk production in future as well as today. Always take a 360° approach to all areas of the farm enterprise.


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