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Practical targets

Best Practice (102):

·        Pigs weaned per litter: 9.4 (immediate target-top 20%), if weaning 9.7 pigs (long-term target-top 10%).

·        Piglet growth rate to weaning: 220 g/day (6.0 kg at 21 days, 7.5 kg at 28 days).

·        Sow condition score 3 maintained throughout lactation.

·        A national USA survey resulted in feed conversion ratios ranged from 2.18 to 5.91 kg in grow-finish stage, for an average X=3.28 ± 0.52 kg of feed/kg of growth.

The birth weight, weaning weight, and the post-weaning daily growth rate during the first week without suckling its dam are the best targets for pig farms to accomplish better results for further development and to finish more efficient pigs. Piglets weaned under <7.5 kg need more attention to avoid post weaning syndrome. It is important to provide for the animals’ needs to obtain an average daily gain performance > 250 g during the week after weaning to reduce growing variation as compared to the heavier weaned pigs (80). The weight of the piglet at any age does not determine the ADG after weaning (81). The birth weight will be an intrinsic advantage or disadvantage throughout the production cycle of the pig (Table 1.24), but being underweight could be overcome under appropriate nutrition and management. Many factors will affect the growth performance of the weaning pig such barn facilities, temperature, relative humidity and ventilation, space allowance per head, nutrition diet, feed’s form presentation (liquid, dry, pellet) and feeder design as well as many other management practices, but attention should be paid to the less suited pigs in order to reduce weight differentiation with the heavier pigs (167).

Table 1.24.    Relationship between birth weight and body weight at weaning at 27 days (42)

Suckling piglets supplemented ad libitum liquid and mixed pelleted skim milk (20% dry matter DM) grew faster during lactation at the rate of 291 g/d vs. 223 g/d and weighted more at weaning (20 days) 6.74 vs. 6.13 kg compared to piglets that only sucked their dams (57). After weaning the creep feed group improved growth rate of 213 vs. 151 g/d after the 2 days post weaning and this advantage was maintained at 41 days with 14.7 vs. 12.2 kg and pigs were 10% heavier at 120 days with 64.5 vs. 60.6 kg, respectively. This advantage was maintained throughout growing period to the finishing stage for the liquid feeding but not for dry feeding (56). A compensatory growth response for the non supplemented pigs was equivalent to the growth rate of pigs receiving dry feed that had a growth lag after weaning. This compensatory growth proves that regardless of the beneficial effects of early creep feeding in improving health of the suckling piglets, reducing mortality, improving feed efficiency all the way through the finishing process, the early growth advantage can be lost if daily growth rate is not maintained or improved  after the first week of weaning.  The average commercial growth rate for piglets of 1.5 kg live weight gaining 285 grams per day whereas their genetic potential is 576 g/d (87).

The biological growth potential 400g/d is 74% higher for the supplemented piglet than the pig only nourished by its dam and growing at the rate of 230 g/day from birth to 21 days of age. This growth difference is highly influenced by an endogenous intestinal reduction (60-75%) in the synthesis of arginine after 7 days of age and progressively even more after 14 days of age, indicating that sows milk provides only < 40% of the daily arginine requirement for suckling piglets. The importance of providing feed supplements high in arginine is because amino acids like arginine and leucine stimulate the secretion of insulin and growth hormone that regulate protein accretion. Arginine is the most important carrier of nitrogen in the body and participates in many metabolic pathways. It is the immediate precursor of citrulline and ornithine and a reduction in arginine plasma concentration reduces glutamine, threonine, and alanine levels as well (130).

A research study conducted with different numbers of suckling piglets per treatment demonstrated that the sow that milked the 6/6 group of litters reared 12 piglets and lost less weight than sows constantly milking 12 pigs per litter (Table 1.25).

Those small litters may have higher individual growth rates because there is more milk available for each of the pigs in the litter, whereas larger litters of 12 pigs will have 50 grams less body weight at weaning than litters of 6 piglets. The cross-suckle treatment 6/6 during early lactation produced milk yield of 8,920 g/d and those litter with only 6 piglets produced 7,819 g of milk/d. The largest daily gain was for litters with 6 piglets but not for the total litter weight at weaning. The lactating sows had a feed intake of 4.57 kg/d (121).

Table 1.25.    The effect of suckling treatment on sow live weight and backfat and on litter growth rates during lactation (121)

^aSuckling treatments had sows that continually suckled 6 and 12 piglets, respectively, from parturition to 28 days of lactation. The litter treatment 6/6 comprised two suckling groups of six piglets; each group was allowed to suckle the sow during alternative 30 minutes from d 6 to 28 days of lactation.

^b,c,dWithin a row, means lacking a common superscript difference (P<0.05); in the absence of superscripts, means are not significantly different.

Fostering

The main goal of cross fostering is to match the number of piglets according to the capacity of the sow and to equalize piglet weights within litters. This practice is used to optimize the rearing capacity of the sow and to standardize piglet weight at weaning. A large database of 300 farms demonstrated that this practice is common in USA and Canada (151).

A sizable British analysis that involved 13,640 piglets from 1,615 sows revealed that cross-fostering reduced piglet growth 10.5 % from birth to 14 days of age. More than 10% of the newborn pigs were fostered and should have been limited to the first day after farrowing, moving only piglets with light to medium birth weights in order to minimize the detrimental effect on piglet growth within a litter (69). Some studies reported advantages for practicing cross fostering and many did not recommend this method because several factors were involved that increased health risks (82).

The practice of fostering implies many unwanted results as 13% lighter piglets at weaning, more frequent fights in resident and fostered pigs, failed nursing and snaps at piglets (Table 1.26). Piglets develop teat fidelity within the first days after birth and suckled at the same teat until weaning. This behavior is an advantage to the young because it reduces competition and fighting at the udder. The practice of fostering interrupts all the social equilibrium and results in stressful behavior to the pig and sows (129). It is important to understand that fostering is a husbandry tool to resolve stressful situations for the milking mother or to some members of the litter that have severe disadvantage to thrive or survive, but this practice implies biological justifications and should not be used as a mechanical tool in the daily routine activities as it is common to see it in large confinement farms.

The practice of fostering is enhanced if allows piglet colostrum intake after delivery or if it is implemented between sows of the same farrowing date, remove piglets before the litter establish teat selection and fixation. The fostering activity could be used at the end of the lactation period on partial weaning practices if an extended lactation period can be accomplished. Fostering should be limited to sows and piglets in the same farrowing room to avoid disease dissemination and to accomplish the establishment of the All-In-All-Out system. It is important to notice that fostering should be avoid during normal lactation period just to make more uniform litter numbers if mortality rate was increased.  

Table 1.26.    Piglet weight average at 14 days of age in two categories for birth weight: fostered and not-fostered piglets. (69)

Only the difference of 1.8 kg in weaning weight (6.1 vs. 7.9 kg) at 25-29 days of age increased the difference to 5 kg at 78 days and to 10 kg at 150 days. Piglets weaned at 4.1 to 5.0 kg required 11 to 20 days longer to reach market weight at 105 kg compared with weaned pigs at 7.3 to 8.6 kg. For any farrowing time the weight at weaning can be large from 4.4 to 11.0 kg and the weight of a 9 weaned pig litter ranged from 58 to 83 kg and there are also very large weight variations within littermates from 5.6 to 10.12 kg/pig within pigs of the same litter. Maximum growth rate (248 ± 63 g/d) occurred at 14 to 21 days and would correspond to the peak of sow’s milk production (99). Previous studies showed that a 2.8 kg difference in weaning weight (4.7 vs. 7.5) resulted in less than 15 days to reach 105.0 kg at market weight. The difference of 0.44 kg at weaning time could reduce 4 days at the finishing stage (114).

Each gained kilo in the suckling piglet during lactation period will represent savings of approximately 5 days of feeding during the finishing stage. This may be equivalent to 20 kilos extra of finished feed instead of < 1.5 kilo of milk substitute used in the farrowing barn. The extra labor involved at the beginning of the rearing stage is easily rewarded with optimized growth in posterior stages. The ad libitum feed intake for a finisher pig >100 kg BW in a diet with energy concentration of 12.0 MJ DE/kg will consume > 3.92 kg/day (52).

The injection of a single dose of dexamethasone (1-2 mg/kg BW) at birth may result in increased weight gain during the lactation and post weaning period for barrows but not for gilts, resulting in an improvement in growth performance and less days to market (114). It can be suggested that the injection of dexamethasone has a relive effect on the practice of early castration but this is a question mark because also inhibits the immune system. There is an important advantage in most of the productive parameters for the heaviest pigs in the litter but the pig industry has to deal with all the piglets born alive to consider economic profits (Table 1.27).

Small piglets < 1.1 kg have fewer numbers of muscle fibers in their body and they have smaller organs (except the brain) than the same pigs in the litter with higher birth weight and these physiological disadvantages may affect their subsequent growth potential. The number of fibers is fixed at or shortly after birth and sometimes reduced after weaning time. The lower number of muscular cells could be compensated at slaughter time when a finished pig of 105 kg will have fewer but larger muscle fibers (82).

Table 1.27.    Post weaning performance of pigs weaned at 18 days of age in relation to weaning weight (135)

Feed Processing

The physical form of feedstuffs such cereals (maize, wheat, barley, rice, triticale, rye, sorghum) can be modified  using several feed processing techniques by means  of rolling, milling, flaking, extrusion, expansion (puffed), expanding jetsploding, pellets, cooking, autoclaving, baking, thermal treatment and application of steam heat conditioner, steam flaking, steam pelleting (80°C ) and pressure and infra-red radiation/micronization (34).

Feed can contain thousands of bacteria and fungi in each gram which cause negative reactions in the upper part of the digestive tract. It is necessary to prevent these organisms from multiplying and a few products will be discussed in subsequent section of the paper. The proper use of any other physical or chemical treatments, contribute to the improvement in digestibility of the starch fraction of the grain and the reduction of salmonella. The process selected may also react on the denaturation of anti-nutritive components and nondigestible factors of the grain and may have an effect on the reduction of any other bacteria populations already present in the feed (5). Gelatinization occurs at 65°C changing the physical structure and distribution of the granules of starch. The response to the treatment depends on many external factors (time, temperature, and moisture) and it changes its degree for every type of cereal. When the transformed feed is fed to the animal, this leads in the digestive system to a more hydrolytic action by enzymes. The most important issue is to get a more palatable product to stimulate feed consumption. On the contrary, the over heating of the starch causes a reduction in the digestibility of the grain and generates bitter flavors (170).

Some cereal species may have anti-nutritional factors as b-Glucans and pentosans and lesser amounts of flatulence producing oligosaccharides as raffinose, stachyose, verbascose and ajucose. These products also occur with higher levels in oil seeds species and oil-extracted meals and are not easily digested because the pig does not have a-galactosidase, but instead a metabolic pathway using invertase (sucrase) enzymatic reaction occurs hydrolyzing these carbohydrates improving digestible values and reducing the fermentative potential of gases in the hind gut (35).

The recommendation is that cereal grains should be ground to >400 to <700 microns and later on pelletized in a 2.4-3.97 mm diameter to 13 mm length pellet (164). The stomachs of weaned pigs fed a finely ground wheat-based diet were shown to have severe ulceration and were colonized by Helicobacter species, while feeding extruded wheat showed no ulceration and no bacteria (85).

Cereals are cooked in Europe to increase digestibility (gelatinization) of the starch fraction and the process will increase the overall digestibility of the feeds. Piglets have a preference for dried ground feed rather than high moisture rolled or high moisture whole feed. The most easily digested cereals are cooked oat starch and flaked maize (64). This list includes rice for human consumption that has no resistant starch and if cooked will be an excellent energy source that will reduce incidence of scours but will not accomplish growth rates obtained with corn. Basically, there is an effect of a high relation rate in the weight of the starch content and the seed weight cuticle. These cereals may have lower cellulose content or tannin levels as compared to other cereals (170). The hydrolyzed corn syrups or dextrose is another method to feed corn in form of sugars or sweeteners.

The use of soybean meal may cause allergic or transient hypersensitivity reactions in the immature gut of the young pig thus limiting its use in early rearing formulas (7). It is possible to detect b-conglycinin in the blood serum of a weaned piglet (9). Different industrial processes have been used to reduce anti-nutritional factors such trypsin and chymotrypsin inhibitors, antigenic proteins, unavailable carbohydrates and lectins (haemaglutinins), developed during prolonged soybeans storage that generated proteins as glycinin and b-conglycinin. Soybean protein either stimulates nitrogen secretion by the exocrine glands of the digestive tract or causes excessive loss of gut wall cell by sloughing. The same effect was found on soybean meal, soy protein isolate and fishmeal (3). The high digestibility > 80% of the soybean meal, soy protein isolate and fishmeal is comparable to skimmed milk powder but poorly absorbed < 75% on the apparent ileal digestibility, leaving protein molecules for bacteria growth in the colon. This is a main reason not to use high levels of soybean protein in weaner diets because the young pig does not have the required enzymes to break down proteins and complex carbohydrates from soybean meal (8).

The hydrolytic contribution of the hydrochloride acid in the stomach is low during the first days of age. The flatulence producing oligosaccharides present in whole soybean and soybean meal are raffinose, stachyose and verascose and this is the reason to apply thermal treatment to the soybean grain. It is not that soybean meal use is wrong it is the most studied vegetable protein and research in this topic dominates the majority of the reports, this is why there is more information on it and a supportive way to decide its wiser proper use. Table 1.28.

Soybean protein concentrates are produced by the alcohol washing process which together with subsequent heat treatments deactivates the antigenic substances (glucinin and B-Glycinin and the lectins) and the anti-trypsin factor and removes the soluble carbohydrates raffinose and stachyose. This also denatures the protein in the product and renders it insoluble. This product is proportionately about 95% of the digestibility of skim milk, but its physical characteristics have a problem of rapid sedimentation in the reconstituted milk. The soybean isolates are expensive but the product contains more protein (171). They require extra process by enzymatic digestion to deactivate antigenic or antinutritional factors (63). It has not been proven whether supplements made of soybean sources may cause reduced growth effect during lactation, because there is a protective inflammatory factor on fresh sow milk.

The list of soybean byproducts in the feed industry is large and just to mention a few as full fat extruded soybean, texturized soybean protein, whole fermented soybean, whole extruded soybean, high protein soybean, macerated full fat soybean, micronized soybean.

Table 1.28.    Effect of different soybean products on immune response; absorption (Xylose) and post-weaning growth rate in young pigs (44)

The lower antigenic products as milk substitutes would be soy flour, soy protein concentrate, isolated soy protein and the protease treatment of soybean meal in hot ethanol.          

Supplementation

The methods for supplementing feed and nutrients are orally, stomach tube, anal, intravenous and intraperitoneal. The following data are the comparison effects on growth rate (g/d) for not supplemented piglets (NS) and supplemented (YS). The results show that from 10 to 20 days of age the NS gained 220 g/d and YS grew 290 g/d. For those providing creep feeding from day 14 to day 35 the NS grew at 180 g/d and YS at 220 g/d. The neonates that received milk substitute from birth to 21 days of age, during the cool season the ADG was 235 g/d for the NS and 255 g/d for the YS. The group fed during the warm season had a growth rate of NS 170 g/d and YS 235 gram per day (82).

The artificially bottle forced supplementation at this early age may reduce variation in growth rate within and among litters, reducing the numerous environmental effects that cause poor milk consumption.  This vari