Nutritional measures to prevent heat stress in pigs in summer

Heat stress refers to the sum of the non-specific physiological responses of the body in an extremely high temperature environment to the thermal environment. With the development of intensive and high-density feeding, the decline of sow fecundity caused by heat stress is becoming more and more serious.

Heat stress caused serious weight loss of sows, prolonged the interval between weaning and reestrus, reduced the number of ovulation, decreased conception rate, decreased embryo survival rate, reduced litter size, sows without estrus, and even shortened the useful life of sows. In addition, under the feed intake of lactating sows during heat stress, the lactation will be insufficient, thus affecting the growth of piglets and the survival rate before weaning.

Provide high quality protein

Dietary protein and lysine in lactating sows are the key factors affecting their reproductive performance. Low protein in the diet during lactation will prolong the interval between weaning and reestrus in sows. Under heat stress, pigs need more protein, but too much crude protein will increase the body heat of sows and make them feel hotter. Therefore, when the weather is hot, providing high-quality protein and essential amino acids to lactating sows can effectively meet their needs and reduce weight loss.

The daily lysine requirement of lactating sows should be more than 60 grams, and the corresponding feed lysine content can be calculated according to the actual feed intake of sows. Threonine is not enough relative to milk production and breast growth. Therefore, threonine has become a potential limiting amino acid for sows with low feed intake and high body weight loss.

During the 21-day lactation period, the ratio of threonine to lysine in feed should be increased to 75% for sows with a weight loss of 75-80 kg. For sows with the lowest weight loss (0,8kg), the ratio of threonine to lysine in feed can be reduced to 60%. For sows fed a typical corn-soybean meal diet, threonine may become the first limiting amino acid when weight loss is greatest (75kg to 85kg), but in other cases of weight loss, lysine may still be the first limiting amino acid; when weight loss is minimum, valine may become the second limiting amino acid after lysine. It is reported that increasing the level of arginine in the diet of heat-stressed sows from 0.96% to 1.73% can reduce the weight loss of lactating sows and improve feed efficiency, but has no significant effect on feed intake of sows and growth performance of piglets.

Increase dietary energy concentration during lactation

When the dietary energy concentration of sows was increased, the feed intake of sows tended to decrease, and the final energy intake was similar. However, when using a high-fat diet, sows generally participate in energy intake. According to the principle of thermodynamics, more body heating can lead to a decrease in feed intake under the condition of high temperature. Compared with carbohydrates and protein, fat has lower heat consumption and higher energy content, so it is more beneficial for lactating sows to increase energy concentration by adding fat to diet. Feeding high-fat diets to heat-stressed sows can shorten the interval between weaning and reestrus. The composition of short-chain fatty acids in breast milk, do not use saturated fatty acids and long-chain fatty acids compared to the high fat. In addition, summer must prevent added fat from oxidation or rancidity, it is recommended to add antioxidants at the same time.

In addition to heat stress, it is not appropriate to add fat to the diet of lactating sows, because fat does not promote insulin secretion like starch. On the contrary, adding fat to the diet of lactating sows decreased plasma insulin content and luteinizing hormone secretion.