What to do when first-litter sows do not come into heat after weaning? Improving nutrition is key
First-litter sows not coming into heat after weaning? Solving nutrition is the key!
The root cause of first-litter sows not coming into heat after weaning, difficulty conceiving again, and lower piglet numbers in the second litter is that when entering the second reproductive cycle, the sow's body nutrient reserves are severely insufficient, because the reproductive system has a weaker priority in nutrient distribution than other organs and systems, so nutrient deficiency affects the reproductive system the most. Of course, first-litter sows not coming into heat after weaning is also related to sow health, especially reproductive tract health, and the heat-induction environment.
Here we mainly start from nutrition management to solve a series of reproductive disorder problems such as first-litter sows not coming into heat after weaning.
01
Nutrition principles and concepts
The nutrient reserves needed for estrus include not only major nutrient reserves, but also reproductive nutrient reserves.
Major nutrient reserves mainly refer to reserves of nutrients such as starch, protein, fat, and macro minerals, reflected in body weight and body condition;
Reproductive nutrient reserves mainly refer to reserves of key nutrients related to reproductive structures and reproductive functions, such as special vitamins and special trace elements.
Sufficient reserves of both types of nutrients are indispensable for completing the reproductive process.
The main reasons for insufficient major nutrient reserves are:
The first-litter sow's own weight gain (the first-litter sow's own weight gain is about 50kg), failure to meet standards at first mating, insufficient/improper restricted feeding in early and mid-gestation, insufficient total daily nutrient intake, insufficient feed intake during lactation, and insufficient flushing for fetal development.
The main goals of major nutrient reserves are:
At weaning, the sow's weight loss should not exceed 10kg, and body condition should reach a body condition score of 2.5 to 3. To achieve this body reserve goal, increasing feed intake during lactation alone is not enough; it is necessary to start from the whole process of first-litter sow rearing (as shown in the figure below).
Figure 1 Effect of body weight loss during lactation on the weaning-to-estrus interval
Regarding reproductive nutrient reserves:
First, pay attention to insufficient intake of reproductive nutrients during the restricted feeding period due to reduced concentrate intake;
Second, pay attention to the fact that the lactation nutritional needs during lactation differ from the reproductive nutritional needs; during the preparation period for mating, even if a relatively nutrient-rich lactation feed is fed, it still cannot meet the reproductive nutritional needs required for estrus;
Third, the increased demand for reproductive nutrients in high-temperature seasons must also be considered; fourth, the destruction of reproductive nutrients in feed by environmental factors must be considered; fifth, the possible insufficiency of the amount added in commercial feed must be considered.
02
⟧Measures to solve first-litter sows not coming into heat after weaning
⟧1) First mating must meet standards.
For introduced foreign breeds, the first mating standard should reach: body weight above 140kg, backfat 18 to 22mm, age above 230d. If sows with low body weight, thin backfat, and insufficient age are mated too early, it will lead to: delayed estrus after weaning in first-litter sows and a high return-to-estrus rate after re-mating; fewer piglets per litter in the second litter; increased chance of abortion in cold seasons; low milk yield and shortened productive life.
2) For first-time pregnant sows, certain nutrient levels during gestation can be appropriately increased by about 10% compared with multiparous sows; such as CP 14%, lysine (Lys) 0.7%, calcium 0.9%, total phosphorus 0.8%, available phosphorus 0.45%.
3) In late gestation, first-litter sows still need moderate feed increases for fetal development.
Because two-thirds of the fetus's body weight is gained during the last one-third of the sow's gestation period. If fetal development is not supported with extra feed, according to the principle of nutrient distribution that gives priority to offspring, the sow's nutrients are preferentially supplied to the fetus, and under insufficient intake, the sow may mobilize body fat and even body protein to supply fetal growth, meaning the first-litter sow is already losing weight and body condition in late gestation!
Furthermore, if fetal development is not supported with extra feed, the sow's physique will decline, which instead affects farrowing; in addition, insufficient fetal birth weight will affect piglet survival rate during lactation. In fact, surveys have found that birth weights within 1.5kg will not cause dystocia due to excessive birth weight.
4) Exercise the sow's intestinal function.
A good stomach means a good appetite. "Good stomach" here refers to good gastrointestinal function and large gastrointestinal volume. At the 2014 "International Academic Conference on Nutrition and Intestinal Health" held in Europe, attending experts believed:
First, in addition to digestive function, the animal's intestine also has chemosensory and body signal reception functions. The small intestine is not only a passive absorption channel; in fact, before absorption it also has regulatory and control functions. Therefore, when raising animals, the small intestine must be well cared for first;
Second, control measures for piglet diarrhea should not only consider pathogenic factors, nor should antibiotics be abused, but should focus on improving the environment, adjusting water quality, and strengthening nutrition;
Third, regulate piglet intestinal health through sow feeding. Therefore, pig farms should take the sow as the core element, work on strengthening nutrition and management, and condition the sow's milk well; fourth, in hot environments, special attention should be paid to improving sow feeding management.
For pregnant sows, especially first-litter pregnant sows, supplementing high-quality crude fiber, especially green fodder, throughout gestation is very necessary. It can reduce constipation, exercise intestinal function, enlarge gastrointestinal volume, promote reproductive organ development, and increase the sow's happiness index.
Experimental studies have found that supplementing green fodder 3d before farrowing and 7d after farrowing is very helpful for reducing lactation disorders and increasing feed intake after 7d.
5) Concentrate the advantageous resources of the pig farm to increase the feed intake of first-litter sows during lactation.
As can be seen from Figure 1, the greater the body weight loss during lactation, the longer the interval from weaning to estrus, but this characteristic is more obvious mainly in first parity (Vesseuret al.,1994). Therefore, increasing feed intake during lactation is the most effective measure to reduce weight loss after weaning in first-litter sows, and the ideal feed intake target (kg) must be reached: 1.8+0.5×(number of piglets suckled by the sow).
03
Key points for increasing feed intake of first-litter sows during lactation
1) Temperature.
The most suitable temperature for sows is 18 to 22°C. Above 24°C, every increase of 2°C will reduce feed intake by 0.5kg. Relatively ideal cooling methods in the farrowing house include tile water curtain cooling, local cold air cooling, and drip cooling, preferably combined with roof and wall insulation for better results (as shown in Figure 2 below).
Figure 2 Tile water curtain cooling
2) Clean and sufficient drinking water.
The water supply rate of the drinker should be 1.5 to 2L/min, the water temperature should be about 17°C, preferably with drinking water in the trough, and the water quality should meet human drinking water standards.
3) Supplement disease-resistance nutrition.
Research has found that only when the substances an animal eats each day are fully metabolized that day does the animal have a good appetite. If metabolism is not smooth, it will cause blockage; many substances block metabolic pathways, and at this time the animal has no appetite. The role of disease-resistance nutrition in improving appetite is, on the one hand, to make substance metabolism in the body smoother. On the other hand, it can improve the sow's health.
4) Clean troughs.
In summer, it is very necessary to clean the trough before each feeding, which can remove sour odors and reduce poisoning from spoiled substances.
5) Restricted feeding in early and mid-gestation.
During gestation, basic nutrients should be ingested strictly according to feeding standards, and excessive intake should not occur, because feed intake in early and mid-gestation is negatively correlated with feed intake during lactation, while feed intake during the fetal development period is not closely related to feed intake during lactation. Intestinal exercise during gestation: the sow's intestinal function is not only the resulting basis for feed intake during lactation, but also an important guarantee of the sow's physique.
6) Feed ingredients should be clean and fresh;
Feed wet feed, with a water-to-feed ratio of 4:1; increase the number of feedings to 3 to 4 times, and feed during low-temperature periods.
7) Appropriately increase the nutrient concentration of lactation feed for first-litter sows.
For example, protein can reach 20%, lysine can be supplemented to 1.2%, and fat should also be supplemented at the same time, paying attention to the balance among amino acids.
8) Prevent postpartum infection in sows.
Production findings show that sows with postpartum infection will not only have reduced feed intake, but also directly affect post-weaning estrus and conception. Therefore, active prevention should be carried out through measures such as clearing pathogens before farrowing, infusion during farrowing, injection after farrowing to fight infection, and infusion of Gongyanjing to remove lochia. Once mammary or reproductive tract infection occurs, activelytreat it。
9) Wean in 2 batches and wean appropriately earlier.
① Method: wean the heavier half-litter of piglets 2 to 5d earlier than the lighter half-litter of piglets; ② Mechanism: start the hormonal mechanism of estrus by reducing prolactin secretion;
③ Effect: reduce the sow's nursing burden; strengthen the physique of lighter piglets;
④ Result: earlier estrus in sows; better piglet uniformity; especially suitable for first-parity sows. When conditions permit, weaning first-litter sows about 3d earlier can reduce the sow's nursing burden and restore body condition as soon as possible.
10) Supplement reproductive nutrition.
Supplement reproductive nutrition starting from lactation until gestation. Especially in high-temperature seasons, the demand for reproductive nutrition is greater.