Sow nutrition: Critical points in the transition period (2/2)

Nutrition during the transition period (TP), which includes the last ten days of gestation and the first 10 days of lactation, has a direct impact on the productivity of the sow and her piglets. We will continue to describe some of the factors that are directly affected. We began this list in the previous article.

6) Body condition and mobilization of reserves: When a sow reaches farrowing in an inadequate body condition (due to deficiency or excess), the problems at farrowing are aggravated: more stillbirths, worse piglet vitality, greater heterogeneity of weights, higher incidence of mastitis, metritis, agalactia, prolapse, ulcerations on the back, diarrhea in suckling piglets, worse oestrus, and lower fertility and prolificacy at the next cycle. Doubts arise... What amount of feed should we give in those last ten days of gestation? On the 106th day of gestation, if the sows arrive overweight, clearly we should not increase the feed consumption, but what isn't so clear is whether the thin sows at that point should eat a lot of feed before farrowing. Many studies have shown that feeding large amounts of feed (>4 kg/day) has a negative effect on milk production in the first 10 days of lactation. A negative energy balance in those 10 days pre-farrowing has benefits for milk production.

7) Farrowing process: The duration of farrowing in hyperprolific sows is longer than it was in the past, and above all, there is a much higher individual variability (90 to 900 minutes), which is not associated with the total number of piglets born. Nutrition programs have a role to take into account, summarized by the following aspects:

• Energy: Pre-farrowing diets with elevated energy or fat content that promote overweight sows lead to longer farrowing.
• Fiber: Directly correlated with the quality of the feces (water content). If sows are constipated at the end of gestation, farrowing is prolonged with all the aforementioned consequences. The quality and type of fiber, more than the level of crude fiber, are determinant due to their water retention capacity, regulation of intestinal transit, digestive comfort, and regulation of microbiota.
• Calcium: The calcium pump in the nerve endings is necessary for the contraction mechanisms in the uterine musculature. An appropriate level of calcium will favor the physiological process of farrowing. Excesses calcium or calcium deficiency can cause the blockage of this mechanism and have the opposite effects.
• Zinc: Its role in reducing stillborn piglets is well referenced, but the exact mechanisms that determine this are not known. Due to the legal limitations of this mineral in Europe, we believe incorporating it in its organic form is opportune to achieve its beneficial effect in breeding sows.

8) Stillborn piglets and post-farrowing mortality: Piglets that are dead when we arrive to attend to the farrowing in progress or the finished farrowing. This includes both piglets that were already dead before farrowing began and those that die during farrowing, which are closely related to multiple causes, especially the duration and the triggering factors of farrowing. We know that during the entire lactation, mortality in the first 100 hours of life is the highest (graph 1). Many of these losses are related to insufficient energy intake if colostrum intake does not happen early (first 12-16 hours) and milk production, which starts between 23 and 39 hours, is not sufficient. An important conclusion is that there can be no discontinuity between colostrum and milk production.

9) Glycogen reserves in piglets at birth: As soon as the piglets are born, the glycogen present in their body reserves (liver and muscle) begins to oxidize, as well as the nutrients from colostrum that provide energy, since their thermoregulation needs increase dramatically outside the intrauterine environment and the high heat losses due to their large body surface area. The glycogen content in piglets at birth is between 50 and 70 grams (3-3.5% of their live weight - similar to the proportional weight of the liver) which is the energy equivalent of two kilograms of gestation feed with 40% starch. Controversies on how to increase glycogen levels in fetuses during the last days of gestation with diets containing corn starch, medium-chain fatty acids, or coconut and fish oils are variable in the scientific literature.

10) Synthesis of colostrum and milk: The newborn piglet depends on colostrum consumption to acquire proper passive immunity. Colostrum is the first secretion of the mammary gland and a source of maternal immunoglobulins and provides other soluble immune components, cytokines and leukocytes that have an immunomodulatory action. Colostrum also provides highly digestible nutrients, energy sources (lactose and lipids), and contains natural growth factors that support the normal development of vital organs and the intestinal tract of the piglet from birth. The high IgG content of colostrum defines systemic passive immunity. Piglets with less than 10 mg/ml of IgG in plasma at day 3 of life have three times higher mortality than those with levels above 10 mg/ml (Cabrera, 2012). IgA levels help protect the intestinal mucosa against digestive pathogens. The weight of the neonate's stomach increases by 26-54% between the first and third day of life compared to the 7.5 to 23% increase in body weight. The small intestine increases in weight by 70%, length by 24%, diameter by 15%, villus height by 33%, and enzyme activity also increases 80-200% in this very short period of time. Piglets' colostrum consumption in this period can be estimated by the prediction equation combining average daily gain and birth weight (Theil, 2014). One of the components of colostrum that catalyzes lactose synthesis (alpha-lactalbumin) increases in the blood plasma of sows 7-10 days before farrowing, with a significant level of lactose in plasma 4-5 days before farrowing. Most of the genesis of colostrum production is considered to take place in the early part of the transition period (last 10 days of gestation) (Quesnel, 2015). Colostrum production is highly variable in different studies with ranges from 1.5 to 5.5 kg (Quesnel, 2011) with an estimated mean of 3.5 kg; another study found 4.75 kg (0.65-9.42 kg/day) (Declercl, L 2013); another 5.9 kg with ranges from 2.7 to 8.5 kg/day (Theil, 2014); and a recent study found 5.6 kg (Nuntapaitoon, 2019). Sow weight, parity number (2nd to 4th parity sows produce more colostrum than gilts or 7+ parity sows), body condition, and inducing farrowing influence this range of variation per sow. The birth order of piglets in the litter does not influence colostrum intake and vitality/vigor of the litter does influence colostrum production capacity (Devillers, 2007). When the percentage of dead piglets increases, colostrum production decreases (Quesnel, 2011).

The composition of the milk changes over the days following colostrum; it changes less quickly, and is estimated to stay the same, with few variations, after 10 days of lactation (end of TP), as we can see in the following table.

Table I. Nutrient content of colostrum and milk (Hurley, 2015).

We can increase the fat and dry matter content of the milk based on the fat content/type in the feed supplied during the TP. Lactose and ash content will remain constant, as we can do little through the nutrition of sow at this stage. To our knowledge, the modulation of feed protein levels does not influence the protein content of milk during lactation, where its content drops from day five onwards, also changing the amino acid profile. From that day on, alanine, cysteine, phenylalanine, glycine, leucine, methionine, serine, threonine, and valine are more abundant. The content of glutamic acid, lysine, isoleucine and proline decreases, while aspartic acid, arginine, histidine, tyrosine and tryptophan contents remain stable.