Correcting ventilation issues in Co. Tipperary
Natural ventilation systems in cattle sheds provide a number of roles. Most importantly, though, they allow for the inward movement of fresh, clean air and the expulsion of stale air, odours, pathogens and viruses.
Farming in Lattin, Co. Tipperary, JP Hammersley – a participant in the Teagasc Green Acres Calf to Beef Programme – recently observed that the ventilation within his weanling shed was insufficient and he feared that it may have a knock-on impact on health and daily liveweight gains.
After initially noticing an ammonia-like odour from within the shed two weeks after housing, further examination revealed condensation forming on the rafters and sheeting.
For the most part, poor ventilation in existing facilities is down to inlets/outlets being too small or absent. As JP’s weanlings are currently housed in a round-roofed shed and adjoining cubicle house, the absence of suitable air outlets was quickly identified as the cause of the problem.
The purpose of a ventilation system is to control dust levels, temperature, humidity and air circulation. And, although sufficient air could enter the shed, it had nowhere to exit.
After a discussion with his dedicated programme advisor, Seán Cummins, a decision was made to raise some of the sheets on the round-roof shed.
The total area of the shed, along with its stocking density, was calculated to give an indication of how many sheets need to be raised to provide a sufficient outlet space.
In total, giving the stocking density of the shed and the height difference between the inlets and the potential position of the outlets, a total of 3.024m² of outlet area is required. To achieve this, three sheets at the apex of the round roof need to be risen at least 275mm.
It has also been recommended to increase length of the ‘capping’ sheet to prevent excess rain from entering the shed. By carrying out this task, JP will essentially create a breathing roof and providing a suitable outlet for the stale air to leave the shed.
In addition, sheets will also be raised on the ‘lean to’ to a height of approximately 100mm, with an overlap of approximately 100mm to 150mm, at each side, to prevent in-blown rain.
After this task is completed, JP will monitor the performance of the shed closely to see if any more changes are needed.
Winter weanling nutrition
Along with resting paddocks, the primary aim of the winter housing period on calf-to-beef systems is to ensure that animals – both weanlings and stores – are primed to perform at grass next spring.
An average daily liveweight gain target of at least 0.6kg/day has been set on JP’s farm for his weanlings; growth rates of 0.25kg/day or below are to be avoided at all costs as this may lead to a degree of stunting occurring.
To ensure this level of performance is achieved, a special focus needs to be placed on nutrition. Silage testing conducted on JP’s first-cut silage earlier this winter indicated a DMD of 74.3% and a crude protein content of 14.5%.
With this silage, a decision has been made to supplement weanlings with approximately 1kg/day of concentrate over the winter months.
In addition, weighing completed shortly after housing indicated that JP’s weanlings were on target in terms of weight gain at an average weight of 276kg on November 23 (average date of birth: 04/02/2019).
If the 0.6kg/day target is achieved, these animals should weigh – on average – 335kg on March 1.