Nutrition and management of the early-weaned pig
Published: November 15, 2007
By: CHARLES MAXWELL (Courtesy of Alltech Inc.)
Several factors, including larger pigs at weaning, better nursery facilities and management as well as improved feeding programs, have contributed to the improved performance. These advances are the result of rapid development and implementation of advanced technologies. This paper will summarize three areas of technology development that have contributed to a better understanding of requirements for optimum performance of early-weaned pigs. These include the evolution of spraydried plasma protein, the development of segregated early weaning (SEW) as a routine management tool and the potential of oligosaccharides derived from yeast cell wall for improving performance in young pigs.
Spray-dried plasma protein
Weaning as early as three weeks of age has been accomplished for a number of years by the use of diets containing high levels of milk products (dried skim milk, dried whey, cheese by-product), fish meal and refined soybean protein as the primary protein source. More recently, weaning as early as two weeks of age, with an average weaning age of about 17 to 18 days, has become routine in large production complexes with three site production systems. The earlier pigs are weaned, the greater the need for a complex diet to minimize post-weaning lag. This was demonstrated by Okai et al. (1976). In this study, diets varying in complexity were fed to pigs weaned at three or five weeks of age.Amore complex diet was required to minimize post-weaning lag in pigs weaned at three weeks of age than those weaned at five weeks.
In general, early-weaned pigs fed milk-based diets have out-performed those fed other protein sources (Fitzpatrick and Bayley, 1977;Wilson and Leibholz, 1981a,b,c;Walker et al., 1986). Recent research has been directed toward attempts to identify other protein sources which can be efficiently substituted for milk proteins or which can be fed in combination with milk proteins to improve performance (Sohn and Maxwell, 1990a,b). Among the ingredients tested, spray-dried porcine plasma protein has been shown to consistently improve performance when included in starter diets (de Rodas et al., 1995).
Spray-dried plasma protein (plasma protein), is the most exciting protein product to be tested in early weaning pig diets in recent years. Improved handling of the blood products and the utilization of the spray-drying process has dramatically improved the quality and subsequent use of blood protein products in nursery diets.
Several trials have been conducted to evaluate plasma protein for the young pig.
Research at Oklahoma State University (de Rodas et al., 1995) is typical of the responses observed. In this study, 144 pigs weaned at approximately 24 days of age and weighing 7.23 kg were fed one of three diets. Plasma protein (AP-820) or spray-dried blood meal (AP-300) was substituted on an equal lysine basis for dried skim milk in a complex prestarter diet essentially devoid of soybean proteins. Both plasma protein and blood meal improved gain and feed intake during week 1 and week 2 post-weaning (Table 1). Feed efficiency was not affected by treatment. It is interesting to note that feed intake and gain continued to be improved in pigs during a subsequent three week period when all pigs were fed a common corn-soybean meal starter diet.
A summary of studies evaluating plasma protein as a protein source is presented in Table 2. These studies indicate that plasma protein consistently improves feed intake and gain in young pigs. This effect is most evident in the first two weeks post-weaning. Effects of plasma protein also appear to be more evident in week 1 post-weaning than in week 2. Table 3 summarizes studies in which the week 1 and week 2 post-weaning data are presented. In four of the five studies, the gain response and the feed intake response to plasma proteins was greater in week 1 than in week 2. It is also interesting to note that scour score was reduced in pigs fed plasma protein in experiment 5 (Table 4).
Several trials have been conducted to determine the optimumlevel of spraydried porcine plasma for weanling pigs. Gatnau et al. (1991) fed increasing levels of plasma protein (0 to 8%) to 28-day old pigs weighing 7.09 kg and fed a corn-soybean meal-whey diet. Lysine level was maintained at 1.2%. Gain and efficiency of gain in the first two weeks post-weaning improved with increasing plasma levels up to 6% of the diet. Similar results were reported in a larger study (96 pigs) with 25-day old pigs averaging 6.09 kg (Gatnau and Zimmerman, 1992). More recent studies at higher lysine levels, however, have shown that growth performance is enhanced in pigs fed up to 10% plasma protein (Kats et al., 1994; Table 5). These researchers also observed improved performance with methionine supplementation in pigs fed diets containing high levels of spray-dried blood products.
The fraction of plasma protein responsible for producing the growth response in phase 1 has been evaluated in three studies (Cain, 1995; Pierce et al., 1995; Owen et al., 1995). The major protein fractions of AP 920 include fibrin, high molecular weight (globulin), medium molecular weight (albumin) and low molecular weight (<10,000 mw) compounds. Data from the study of Cain (1995) are shown in Table 6.
Pigs fed the AP 920 diet grew faster and consumed more feed during the first twoweeks post-weaning than those fed the negative control diet (P<0.05). Growth performance of pigs consuming the diet containing the high molecular weight fraction (globular proteins) was similar to that of pigs fed the AP 920 diet. Growth of pigs fed the medium molecular weight (albumin) or low molecular weight fractions was not different from that of the negative control. Increased small intestine villi surface area, enzyme activity and serum zinc were also associated with feeding the high molecular fraction. It seems likely to assume that either the immunoglobulins or other unknown factors in this fraction are responsible for the improved performance, intestinal function and zinc status. Results were similar in the other studies.
Also consistent with the concept that passive immunity via the globular fraction in plasma protein is involved in the improved performance in early-weaned pigs fed plasma protein are data showing that the greatest response to the addition of AP 920 occurs when pigs are fed in challenging environments. Coffey and Cromwell (1995) fed pigs weaned at 21 days either a dried skim milk or a plasma protein-based diet in two environments (clean and conventional). The clean environment consisted of an environmentally controlled room (temperature and humidity) previously free of pigs for six months, while the conventional environment consisted of the regularly-used nursery at the University Research Station.
Pigs reared under segregated early weaning (SEW) conditions exhibited little response to spray-dried plasma protein whereas pigs reared in a conventional on-farm nursery exhibited a 32% improvement in gain when the diet was supplemented with spray-dried plasma protein (Table 7). Observations by Gatnau and Zimmerman (1991) were similar. This may be an indication that the improvement in immunocompetence of young pigs mediated by immunoglobulins present in spray-dried plasma protein may not be as essential in an SEW environment and suggests that excellent performance can be obtained with SEW pigs fed less complex diets.
The above study suggests that other approaches may be used to obtain improved performance in pigs without the inclusion of plasma protein. The US swine industry is pursuing a program of earlier-weaning (as early as 14 days with an industry average of 17 to 18 days) with all-in, all-out placement of nursery pigs by site as a means of improving performance.
Segregated early weaning
Early weaning at an age of less than 21 days and removal of pigs to a second isolated site, which is commonly referred to as segregated early weaning, has been shown to substantially reduce disease transfer from the dam (Fangman et al., 1997). Weaning at an earlier age appears to enhance the success of eliminating pathogens (Wiseman et al., 1994). This strategy has been successful in reducing the number of pathogens, but has not been successful in eliminating all pathogens. The premise is that pigs are removed from the sow while their immunity, as a consequence of maternal antibodies, is still high. This maternally derived passive immunity will prevent vertical transfer of indigenous pathogens. Pigs reared in isolation have been shown to have reduced immunological stress (Johnson, 1997) resulting in improved growth and efficiency of feed utilization. Harris (1993) has suggested weaning ages for a number of diseases (Table 8).
Williams et al. (1997a) observed that performance of pigs reared under a medicated early weaning scheme to minimize disease transition had improved average daily gain and feed efficiency when compared to pigs reared in a conventional system and exposed to older nursery pigs. This is consistent with observations in our research at the University of Arkansas to determine if differences in immune stimulation can explain performance differences in conventional vs. off-site reared pigs. A total 432 weanling barrows (19 ± 2 days of age) were obtained from a local commercial company from a single source. Half the barrows from litters were selected for the off-site nursery study (6 pigs/pen) with the remaining pigs staying in the conventional nursery facilities (approximately 18 pigs/pen).
Pigs were weighed and serum samples obtained via venipuncture on day 0, 14 and 34 post-weaning from a total of 72 pre-selected pigs placed in the conventional facilities and an off-site nursery. Aminimum of one pig/litter was sampled in the conventional facility and a minimum of two pigs in each of 36 pens were sampled in the off-site nursery. Serum α1-acid glycoprotein concentrations were determined using a commercial kit (porcine α1-acid glycoprotein plate, Development Technologies International, Inc., Frederick, MD) and a single radial immunodiffusion method. Pigs reared in the off-site nursery were 1.95 lb heavier (P <0.001) at day 14 post-weaning and 5.28 lb heavier (P<0.01) at 34 days postweaning (Figure 1). In addition, serum α1-acid glycoprotein concentration was elevated (P <0.01) in pigs reared in the conventional nursery. This suggests that reduced performance in a conventional nursery may be associated with the immunological stress associated with production under these conditions.
Patience et al. (1997) evaluated the impact of age and site of weaning on pig performance under high health conditions. Pigs were derived from a breeding herd free of infectious respiratory disease, internal and external parasites and most infectious gastrointestinal diseases. Sixteen litters were weaned at 12 ± 2 days and housed in an all-in, all-out nursery room at the swine center (Conventional SEW); 16 litters were weaned at 12 ± 2 days of age and moved to an off-site location (Off-site SEW) and 16 litters were weaned at 21 days and retained on-site (Control). At 21 days control pigs were heavier than off-site SEW or conventional SEW pigs. However, at 56 days of age the off-site SEW pigs were heavier than the convention SEW or control group (Table 9).
The response to SEW is not surprising and is consistent with expected performance in high health herds in animals not undergoing an acute phase response. Exposure of animals to antigens, however, has been shown to result in the release of cytokines that activate the immune system (Dinarello, 1984). This results in a major alteration of metabolic processes (Klasing, 1988) which depress protein synthesis (Jepson et al., 1986) and stimulate protein degradation in skeletal muscle (Zamir et al., 1994). Therefore, pigs which are undergoing exposure to antigens which activate the immune system would be expected to exhibit reduced feed intake and weight gain during the period of antigen exposure.
This is consistent with the concept described by Johnson (1997) who indicated that a dirty, less hygienic environment increases the level of immunological stress and depresses growth and performance of pigs. These effects are mediated by cytokines which affect feed intake and alter the utilization of protein. A second important feature of the inflammatory response is an increase in release of acute phase proteins by the liver. Synthesis of some acute phase proteins may increase several 100-fold. These acute phase proteins are synthesized at the expense of degradation of skeletal muscle protein. Reeds et al. (1994) estimated that to provide sufficient amounts of the limiting amino acid for acute phase protein synthesis (phenylalanine) would require more than a 2-fold increase in degradation of muscle protein. Thus, immunological stress is linked by cytokines to enhanced hepatic acute phase protein synthesis, and decreased muscle protein synthesis and/or increased muscle protein degradation.
This concept explains the impact that specific rearing regimes may have on pig performance. Numerous studies have shown that pigs kept under all-in, all-out management eat more, grow faster and are more efficient when compared to pigs under continuous flow management. Segregated early weaning is a management system which appears to have the potential to reduce immunological stress even further than that observed with all-in, all-out management.
Induction of immunological stress with lipopolysaccharide has demonstrated the relationship of this stressor with increased cytokine production (Johnson, 1997; Mandali et al., 1997). In the Mandali et al. (1997) study, pigs injected with LPS polysaccharide exhibited elevated levels of TNFa (Figure 2). IGF-1 concentrations were also substantially reduced (Figure 3).
A second study that demonstrates the impact of immunological stress on subsequent performance was reported by Ragland et al. (1997). In this study, SEW pigs were commingled with farm-reared pigs at approximately 60 days of age in a control test station. Average daily gain, feed efficiency, average daily lean gain and efficiency of lean gain were lower in SEW pigs when compared to conventional farm reared pigs (Table 10).
This suggests that the SEW reared pigs were undergoing increased immunological stress and reduced performance during the finishing period as a consequence of exposure to higher levels of pathogens during finishing. The best strategy for inhibiting the costly effects of increased immunological stress appears to be by avoiding contact with potential bacterial and viral stressors from nursery to finishing. In fact, performance during finishing may be compromised by a strategy of commingling pigs from nurseries with varying levels of disease.
Pigs reared under isolated SEW conditions have not only been shown to exhibit improved performance, but carcass composition seems to be enhanced as well (Williams et al., 1997b). Research by Frank et al. (1997), however, suggests that any effect of SEW on carcass composition is dependant upon genotype. These researchers compared performance and carcass composition of littermate barrows and gilts which were either segregated early-weaned at 13 days of age (4.8 kg) to an off-site nursery and finisher or conventionally weaned at 27 days of age (7.25 kg) to an on-site nursery and finisher. Genotypes were Landrace-Yorkshire cross (YL) or European Terminal Sire cross (ETS). The ETS pigs had larger loin eye area, higher percent lean and lower 10th rib backfat (Table 11).
However, the lower lean gain (YL) pigs had increased backfat and a lower percent lean in the SEW environment while the ETS pigs had no difference in backfat thickness and an improvement in percent lean in the SEW environment (environment x genotype interaction, P<0.05 and P<0.01, respectively). This study suggests that low lean gain pigs might get fatter and have lower lean yield under the faster growth SEW conditions whereas pigs with higher lean gain potential may have improved carcass composition.
It is also interesting to note that death loss was higher in pigs reared in the conventional environment than those reared in the SEW environment. This difference was primarily due to increased death losses in ETS pigs in the conventional environment suggesting that genetic differences exist for pig survival.
Efficacy of Bio-Mos in improving gain and efficiency in early-weaned pigs
Oligosaccharides derived from yeast cell wall offer an additional technology with potential to improve health and performance in young pigs. Typically, pigs are commingled at weaning and reared in off-site nursery units before being transported for finishing in single source finishing systems. The stress of commingling pigs prior to the nursery phase of production and of long distance hauling to finishing locations is a concern for the swine industry. Polysaccharides derived from cell walls of yeast have been shown to improve performance and to enhance immune function.
Researchers in aquaculture have found a yeast glucan which enhances the non-specific defense mechanism (Raa et al., 1992; Engstad et al., 1992) and survival in fish. Maintaining immunological integrity is particularly critical in the young pig since the trend to earlier weaning now commonly practiced in the swine industry has been associated with a decrease in cellular immunity (Blecha et al., 1983). Similarly, performance has been improved in early-weaned pigs fed a glucan isolated from yeast (Schoenherr and Pollmann, 1994; Schoenherr et al., 1994). Dvorak and Jacques (1997) reported that adding a mannan oligosaccharide (Bio-Mos) to the milk replacer improved gain and intake in young calves. Bio-Mos has also been shown to improve performance in nursery pigs (Spring and Privulescu, 1998). The following study was conducted to further assess the efficacy of Bio-Mos in improving performance in pigs fed two levels of inorganic copper (10 and 185 ppm) and reared in an off-site nursery unit.
EXPERIMENTAL PROCEDURES
A total of 216 weanling barrows [The Pork Group, Inc. terminal sire line X line I (commercial gilt); 21 ± 2 days of age] were obtained from The Pork Group, Inc. from a single source. Pigs were transported to the University of Arkansas off-site nursery facilities, sorted by weight, and divided into weight groups (blocks). Pigs within each weight group were allotted into equal subgroups (six pigs per pen). Treatments were then randomly assigned to pens (subgroups) within each of the weight groups. Four dietary treatments consisted of two levels of inorganic copper (Cu) (10 and 185 ppm) from copper sulfate with and without the addition of Bio-Mos (0 or 4.0 lb Bio-Mos /ton) in a 2 × 2 factorial arrangement of treatments. The specific diets during the first 10 days post-weaning (Phase 1) consisted of the following:
1. A negative control with Phase 1, 2, and 3 diets containing Cu as CuSO4 at 10 ppm (Table 12).
2. The negative control Phase 1, 2, and 3 diets containing 10 ppm Cu plus 175 ppm Cu as CuSO4 (1.4 lb/ton).
3. The negative control Phase 1, 2, and 3 diets containing 10 ppm Cu supplemented with 0.2% Bio-Mos (4.0 lb/ton).
4. The negative control Phase 1, 2, and 3 diets containing 10 ppm Cu plus 175 ppm Cu as CuSO4 (1.4 lb/ton), and supplemented with 0.2% Bio-Mos (4.0 lb/ton).
Substitutions in all diets were made at the expense of corn. Phase 1 diets were formulated to contain 1.50% lysine, 0.90% methionine plus cystine, 0.90% calcium, 0.80% phosphorus, and 14.53% lactose and were fed for a period of 10 days. Upon completion of the Phase 1 diet, pigs were fed a Phase 2 diet (1.35% lysine) from day 10 to 24 and a Phase 3 diet (1.20% lysine) from day 24 to 38 post-weaning.
Pigs were housed in an off-site nursery facility in pens with two nipple waterers, a five-hole feeder, and Maxima nursery flooring. Pigs had ad libitum access to feed and water. For the first week of the trial the nursery was maintained at 85 wF and decreased 1 wF per week. Pig body weight and feed intake were determined at the initiation and termination of Phase 1, and weekly during Phases 2 and 3.
In vitro cellular response was measured using a lymphocyte blastogenesis assay (Blecha et al., 1983). One blood sample was taken via venipuncture from two randomly selected pigs in each pen (total of 18 pigs per treatment, 72 pigs total). Samples were obtained on day 28, 30, 32, and 34 of the study with 25% of the pens sampled (18 pigs, 9 pens) on each of the four days. Approximately 15 ml of blood were collected in heparinized tubes by venipuncture for isolation of mononuclear cells. Blood mononuclear cells were isolated by gradient centrifugation and plated in 96-well round bottom plates (Corning, Corning NY) at a concentration of 2 x 106 cells/ml. Phytohemagglutinin (PHA) and pokeweed mitogen (PWM, Sigma Chemical) were used as mitogens at a concentration of 50 and 25 μg/ml, respectively. Incubation, labeling with [3]thymidine and cell harvesting followed procedures outlines by van Heugten and Spears (1997). Uptake of [3]thymidine served as the measure of cell proliferation.
Performance data were analyzed as a randomized complete block design with pen as the experimental unit and blocks based on initial body weight. Analysis of variance was performed using the GLM procedure of SAS (1988). The effects of block, CuSO4, Bio-Mos, and CuSO4 x Bio-Mos interaction effects were evaluated. Immune data were analyzed as a randomized complete block design with pen as the experimental unit. Analysis of variance was performed using the GLS procedure of SAS (1988). The effects of CuSO4, Bio-Mos, and CuSO4 x Bio-Mos interaction effects were evaluated.
RESULTS
A Bio-Mos x Cu level interaction was observed during Phase 1 (day 0 to 10) for average daily gain (P <0.01), average daily feed intake (P<0.10) and gain:feed (P<0.02). Average daily gain, feed intake and gain:feed increased with the addition of Bio-Mos at 0 ppm Cu, but either remained about the same or decreased with the addition of Bio-Mos at 185 ppmCu. Therefore, these data are presented as treatment means (Figure 4).
Performance data during Phase 2 and Phase 3, and results of the lymphocyte proliferation assay are presented as main effect means (Table 13) as no Bio-Mos x Cu level interaction was observed. Pigs fed diets supplemented with 185 ppm Cu during Phases 2 and 3 had greater daily gain (P <0.003 and P<0.01 for Phase 2 and 3, respectively and average daily feed intake (P<0.01 and P<0.04 for Phase 2 and 3, respectively) than those fed diets with 10 ppm Cu.
Feed efficiency was similar among pigs fed both levels of copper. Additionally, pigs fed diets supplemented with Bio-Mos in Phase 3 had higher average daily gain (P <0.04) and gain:feed (P<0.09) than those fed diets without Bio-Mos. For the overall study, (days 0 to 38), pigs fed diets containing 185 ppm Cu had greater (P <0.01) average daily gain, average daily feed intake and gain:feed than those fed diets containing 10 ppm Cu. Pigs fed diets containing Bio-Mos had greater (P<0.04) average daily gain and gain:feed than those fed diets with no Bio-Mos. Dietary treatments did not affect lymphocyte proliferation from mitogen stimulation on samples taken on days 28, 30, 32, and 34 postweaning.
The performance results of this study are consistent with previous results in young pigs and poultry. As in the present study, Schoenherr et al. (1994) and Van der Beke (1997) reported improved weight gain and feed efficiency in weanling pigs when oligosaccharides were added to the diet; and addition of Bio-Mos improved rate of gain (Stanley et al., 1996) and efficiency (Kumprecht and Zoba, 1997) in broiler chicks. The improved performance may be explained by changes in intestinal morphology, such as greater crypt depth and increased villus width observed in a study by Savage et al. (1997). The addition of Bio-Mos to milk replacer improved gain and intake in young calves (Dvorak and Jacques, 1997). As in the young calf study, gain increased with the inclusion of Bio-Mos in the diet of young pigs. However, no significant increase in intake was observed in pigs fed diets containing Bio-Mos compared to those fed diets with no added Bio-Mos.
Previous research has reported that a yeast glucan enhances non-specific immunity in fish (Raa et al., 1992; Engstad et al., 1992). In the present study, the effect of Bio-Mos on the immunocompetence of weanling pigs was evaluated by mitogen-stimulated lymphocyte proliferation. Although response to mitogen was numerically greater in stimulated cell cultures from pigs fed Bio-Mos, neither Bio-Mos nor dietary copper had a significant effect on proliferation of lymphocytes from mitogen stimulation in the present experiment. This may be attributed to the high level of variability observed in the animals that were sampled.
This study indicates that the performance response to Bio-Mos in phase 1 varied with level of dietary Cu. However, in phases 2 and 3, diets containing either Bio-Mos or 185 ppm Cu resulted in improved performance.
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Author: Charles Maxwell
Animal Science Department, University of Arkansas, Fayetteville, Arkansas, USA
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