Similarly to humans, broilers also need well balanced, energy rich diets to maintain their body temperature during the cold season. And they must keep FCR at a low rate of course. Proper heating and ventilation are just as important however. Finding the right balance between these factors demands an integrated approach.
Since the onset of intensive broiler production several decades ago, the industry has made much more rapid progress resolving hot weather situations than it has cold weather environments. Technologies such as evaporative cooling, high-efficiency fans and tunnel ventilation have made the summer months almost a non-issue for many companies.
However, we still seem to struggle during the winter months where the costs of fuel, litter, and housing combine to make good cold-temperature performance a real challenge.
This is not to discount some great improvements for winter housing, such as insulated solid sidewalls, stir fans, controllers and the use of litter amendments. Yet adequate heating, moisture removal and fresh air often become a challenge in the winter.
Due to typically moist conditions within the chicken house during winter, gut health can also be more affected by coccidiosis, enteric bacteria and viral challenges, such as Runting and Stunting Syndrome (RSS). The gut can become more difficult to manage. In many cases, the nutritionist will attempt to make adjustments to help maintain performance, make floors drier and improve foot quality through feed manipulation as a result of marginal management and deteriorating environmental conditions. The feeding formulation package can assist in helping performance in cold weather – but it is not as powerful as providing good heat and air. The nutritionist, husbandry manager and veterinarian must work together in an integrated way to keep performance from slipping during the cold part of the year.
Typically, one of the first moves by a nutritionist in cold weather is to reduce the sodium in feed, due to increased litter moisture. It is well documented that lower sodium can reduce water intake, water excretion and litter moisture. Adjusting electrolyte balance in the winter will need to be driven by footpad quality goals, and the welfare and economics of footpad dermatitis vs. overall production benefits.
The balance of research over the years shows a minimum requirement for sodium for optimal growth and FCR, which may be higher than that desired for optimal litter moisture control and footpad quality. In other words, your priorities should dictate how low you go in cold weather.
Some good work by Jankowski et al, showed that lower sodium levels resulted in lower litter moisture, but a minimum of 0.19% was needed in early diets, and 0.15% in later diets to maximise growth and FCR. So, recognising that every situation is different, we must be careful not to over-react to cold weather by dropping salt levels beyond what is optimal for good performance, regardless of potential improvements in foot quality.
Other research has shown that using lower calcium and phosphorus levels in cold weather will lower faecal and litter moisture. Again, lower minerals will result in lower water intake but too much of a decrease can impact performance.
For several years Cobb-Vantress has demonstrated that raising the amino acid levels, even above recommended levels, will support better FCR, higher growth rates, and higher breast meat yields. Amino acid density then becomes a matter of setting economic priorities.
Higher protein diets will result in higher water intake, more water excretion and higher depositions of nitrogen in the litter. Therefore, if managers are unable to deal with the moisture and ammonia load inherent from feeding higher protein diets, we are probably better off using low protein feeds. Similarly, some recent work by Ajinomoto demonstrated that reducing the crude protein and supplementing the feeds with higher levels of crystalline amino acids also reduced nitrogen excretion and decreased gut disorders.
In fact, my own communications with veterinarians and nutritionists have indicated that slightly lower protein feeds seem to reduce gut insults, especially during cold weather, where possibly housing out-time is limited. However, again, lower protein and lower water consumption means lower plant yield, so these formulation decisions need to be coordinated. And, the reduced heat increment (heat produced from digestion) inherent in lowering the protein, will place more pressure on providing adequate background facility heat.
Several nutritionists have observed performance improvements and better litter conditions when they were able to replace a portion of the soybean meal with a reliable animal protein. In cold weather, this becomes a useful tool, as the non-starch polysaccharides in the soy meal, along with the high potassium level, can create stresses on the intestinal tracts. Generally, if the soymeal can be reduced in a broiler from 31% to 26% using animal protein with all amino acid balances being equal, my own observation has been that of equal-to or better performance, and drier litter.
A very comprehensive cage study was conducted by Vieira and workers (Table 1), where comparisons were made between corn-soy-fed broilers and those fed a practical percentage of substituted poultry meal. The corn-soy group utilised soya oil as the liquid fat source, while the animal protein group utilised poultry fat. In this study, the animal protein group had the same performance results as the all-vegetable group, but displayed significantly less water intake and excreta moisture.
When examining the diets, it could be argued that a key difference was the lower potassium levels in the animal protein feed. With this in mind, even all-vegetable producers will substitute lower potassium protein sources such as canola meal, sunflower meal and dried distiller’s grains as a partial replacement for soybean meal.
Therefore, protein substitution reveals another tool to help combat poor litter conditions in cold weather, while maintaining good performance.
As mentioned earlier, it seems that broiler performance, especially FCR, tends to decline in the cold months. From my own experience, I have observed that FCR would deteriorate when the seasonal daily low temperatures fall beneath 50°F (10°C). Invariably, farm managers and producers would restrict fuel consumption by turning off brooders and furnaces, thereby forcing bird body heat to keep the house at or around thermo-neutral (70°F/21.1°C).
The introduction of fresh air then becomes limited as efforts are made to maintain temperatures inside the house. Exhausted moisture and ammonia also means exhausted heat.
As bird heat is transferred from inside the house to outside the house via simple thermal transfer or through minimum ventilation, the sole source of energy in many instances is feed, with no other background source of heat.
So, using simple logic and thermodynamics, the birds will consume more feed in an effort to keep comfortable.
However, I have recently seen cases when background heat is maintained, even at older ages, that good FCRs are maintained. One example in North East USA is the use of attic vents, where sun-warmed air is pulled into the house after being stored in the house’s attic plenum. Farms which have mastered this supplemental heating method have seen much improved FCR, a reduction in fuel expense and drier floors.
Another system I observed in Western Europe involved a direct fire boiler system utilising straw. The boiler was connected to a heat exchanger which delivered warm air to the entire house, even on older birds. Such systems can work off multiple raw materials, including straw, wood or cellulose pellets. Farms with this system have shown better performance and less pododermatitis. Again, the common theme is background heat – not relying simply on the bird-generated heat during cold weather. In both of these examples, the common observation is that more air was moved as thermostat-triggered fans cycled more often.
Even with a pure heating fuel such as propane, it is still less expensive to heat with propane than with feed consumption. For example, consider that one litre of propane costs $0.66, and generates 24,024 BTUs, or 6054 kcal. In simple terms, the cost of the propane becomes $0.11 per 1000 kcal. Conversely, a grower feed costing $400 per ton ($0.40 per kg), with 3130 kcal per kg of feed, will cost $0.1278 per 1000 kcal.
However, based on a host of past information on metabolisable energy partitioning, feed is at best 40% efficient at generating body heat, so the new calculation needs to be $0.1278 ÷ .40, resulting in $0.32 per 1000 kcal. This is strictly a cost of energy comparison and does not account for the additional expense for removal of moisture and nitrogen resulting from poorer feed conversion.
Another way to view this is to consider the loss of 5 points of FCR during cold weather on a 2 kg bird – a typical phenomenon. This is an additional 100 grams of feed consumed per bird, or 313 additional kcal or $0.10 in added feed cost. Had propane been used to provide the 313 calories, presumably to keep the birds at thermo-neutral, the cost would have been $0.0344 per bird, a very profitable swap.
In our industry, the entities paying for the feed (companies) are typically different from those paying for fuel (farmers). Fuel allowances have been administered with varying successes across our industry in an effort to conserve feed and to maintain chicken product quality. For the overall benefit of our industry, we need to continue to work on this concept.
As we have seen, the provision for heat and adequate ventilation often falls short during cold weather, resulting in increased feed intake for heat production. Some nutritionists will increase dietary energy (not protein) during cold weather in an effort to maintain constant feed intake, growth and FCR. This will be costly, but most certainly less than allowing FCR to float upward.
So, in theory, extra calories are provided to offset environment-related bird heat loss, without creating added intake in protein and minerals.
An interesting observation was made by Huang in 2011 (Table 2), where it was observed that higher energy feed resulted in less water intake, most likely due to lower feed intake. This becomes important as we battle litter moisture and footpad quality during the cold seasons.
Table 2 – The effect of relative energy level on water intake (ml/bird/day) in broilers. (from Huang, et. al., 2001 Australian Poultry Science Symposium)
|Relative AMEn||Water intake (0-49 days)|
|Water intake was significantly different at 0.001 probability level|
Other nutritionists have noted that raising feed energy levels during cold weather did not alleviate lower performance resulting from a compromised environment. It may be worth a try to evaluate this on a few flocks first.
There have been some feed or water additives that have shown favourable effects in reducing faecal moisture in some cases. These include bentonite, turmeric, yucca extracts and betaine. We do not discount these, but firstly more fundamental attempts should be made to control house environment through management and basic nutrition without resorting to the expense of additives.
There are times, however, when the nutritionist must try some of these products. We do know this: maintaining cold weather performance is difficult, and can only be accomplished with an integrated approach by several people. The housing manager, farmer, veterinarian and nutritionist must all spend time on the farms evaluating and discussing the best steps to take from each area of expertise. Working together, good performance can be a reality in cold weather.
This article was featured in World Poultry magazine no. 1, 2015. To read more printed articles see World Poultry digital magazine