Proper ventilation, sprinklers, and other efforts to maintain pig comfort are important to minimize the negative impact of summer heat on feed intake and growth rate of finishing pigs. However, even with these changes, market weights tend to decline in the summer months.
The seasonal decline from May to August shows that market weights in August are 10 to 15 lb. lower than pigs marketed in May (Figure 1 on page 14 in the issue). It normally takes until the second or third week of October before market weights rebound to more normal levels.
The lighter market weight during the summer also reflects a higher percentage of pigs that do not reach minimum weights set by packers, further decreasing profit potential.
There are just two solutions to counteract the summer growth slump — increase the growth rate of the pigs or increase days on feed.
Because grow-finish space is often limited, any efforts to increase growth rate can pay dividends. Timing of management changes is important. Keep in mind, pigs placed in finishing barns today (March) will be marketed during the heat of the summer. Thus, any diet management changes to improve summer weights should start with pigs born in December or placed in finishing barns in March.
Following are a few dietary, feed and water management areas that could have a positive impact on growth during the summer:
1. Review feeder space and adjustment.
If feeders are adjusted aggressively to minimize wastage, feed access can become limited.
Pigs alter their feeding pattern during hot weather, eating more during the cooler part of the day and decreasing activity during the hottest part of the day. If feeder space or feed access is limited, the negative impact on growth rate will be more severe in the summer months because some pigs will be unable to eat during the cooler part of the day.
Feed access may not be a major issue in most operations; however, it is important to check feeder adjustments to ensure feed access isn’t limiting feed intake. Similarly, because feeding patterns are altered and pigs eat earlier in the day, make sure feeders are full when pigs prefer to eat.
These feeding patterns hold true in sows, too. Automated feeding systems ensure that lactating sows have access to feed during the cooler evening and morning hours when they choose to eat during the hot summer months.
If automated feed delivery is not available, alter feeding times to provide enough feed so sows can eat when they want to.
2. Review water access.
Animals drink more during hot weather. The use of sprinkler systems adds to water use, so be sure to check water pressure and availability in each pen. This is important because limiting access to water can have a detrimental effect on feed consumption.
Properly operating sprinklers in each pen are important so pigs do not try to use the drinkers as cooling devices. When this happens, dominant pigs can limit the water intake of subordinate pigs and, thus, their feed intake.
If wet/dry feeders are used, sprinklers become even more critical as dominant pigs monopolize the feeder and use it as a cooling device, again limiting water and feed intake of other pigs.
Cooling the water before it is consumed by pigs has been shown to lower water requirements and increase feed intake, presumably because it helps the pig maintain core body temperature more easily.
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3. Increase the caloric density of the diet.
Increasing the energy level in the diet fed to pigs marketed during the summer months provides two benefits. First, it increases the amount of energy consumed with each mouthful of feed and, thus, the daily energy intake. Second, higher energy diets have a lower heat increment, which means that there is less heat produced in digesting the feed. Lower heat production means the pig has less heat to dissipate. Thus, pigs can more easily maintain their core body temperature, they feel more comfortable and they increase their energy intake.
The two main ways to decrease the heat increment of the diet is to add fat and decrease fiber levels. Economic evaluation of high-fiber ingredients should receive extra scrutiny during summer months due to their negative impact on energy intake under heat stress.
Nutritionists have long known that adding fat to the diet increases growth rate in the summer. Unfortunately, in recent years, low-cost fat sources, such as choice white grease or tallow, are often used for biodiesel production during the summer, which makes the use of fat less economically competitive exactly when it is needed most. Producers should work with their nutritionist to evaluate the economics of added dietary fat. A simple fat economic calculator can be found at www.KSUswine.org.
Whenever the dietary energy level is increased, the levels of other nutrients, such as amino acids and phosphorus, also should be reviewed and increased as necessary.
4. Decrease crude protein (increased crystalline amino acids).
High crude protein levels in the diet cause two main problems for the pig. First, excess amino acids must be broken down and removed from the body. Second, high crude protein content normally lowers the net energy level in a diet. Therefore, replacing crude protein with crystalline amino acids that are economical (e.g., lysine, threonine, methionine) can increase the net energy content of the diet and increase energy consumption. As L-tryptophan becomes more routinely economically viable, the crude protein level of the diet can be lowered further. The benefit of low crude protein diets can be maximized during the hot summer months.
5. Feed pelleted diets.
When high-quality pellets (less than 25% fines) are fed to finishing pigs, growth rate can be increased by 4 to 5%. Because of the higher value of growth rate for pigs marketed during summer months, it is the optimum time to capture the value of pelleted diets.
Feeding pelleted diets also increases eating speed, so pigs can achieve their desired feed intake in a shorter period of time. This is especially important when feeder access is limited.
6. Consider liquid feeding.
Although liquid feeding is not widely used in the United States, providing feed in a liquid form helps pigs maintain consumption during heat stress. Therefore, the greatest benefit of liquid feeding systems is captured during the summer months.
7. Try feed additives.
Any feed additive that increases growth rate is more valuable during the summer months than other times of the year. For example, feeding Paylean (Elanco Animal Health) during the last three to four weeks before market increases market weight by more than 6 lb./pig. When documented to improve growth rate, other feed additives, such as growth- promoting levels of copper or antibiotics, also provide their greatest economic benefit in the summer.
8. Add days on feed.
If all of the management technologies are already in use before summer arrives, few adjustments are available to further improve nutrient intake and growth performance. In these cases, increasing days on feed is the only way that market weights can be maintained during the summer. Days on feed can be increased by adjusting marketing schedules, but pig flow and barn turnover rates must also be considered. Unless additional finishing space is available, average market weights are still likely to decline.
On average, pigs need an additional seven to 10 days on feed in August to reach the same market weight as those marketed in May.