Effects of
Spirulina platensis
on growth
performance of weanling pigs
$G.S. Grinstead, M.D. Tokach, S.S. Dritz
*,1,
R.D. Goodband, J.L. Nelssen
Department of Animal Sciences and Industry, Kansas State University, Manhattan, KS 66506-0201, USA
Received 5 May 1999; received in revised form 8 October 1999; accepted 17 November 1999
Abstract
Three experiments were conducted to evaluate the in¯uence of an algae derived feed additive,
Spirulina platensis(SP), on weanling pig performance. In all experiments, pigs were blocked by weight and allotted to one of four (experiments 1 and 3) or six (Experiment 2) dietary treatments. Standard diets and feeding regimens were implemented in all three experiments and SP replaced soybean meal on an equal lysine basis. Zinc oxide (3000 mg Zn kgÿ1
) and medication were included in the diets for only experiments 1 and 3. In Experiment 1, a control diet or diets containing 2, 5, or 20 g SP kgÿ1
were fed in a pellet form from days 0 to 14 after weaning followed by meal form from days 14 to 28 after weaning. From days 0 to 14, no differences in pig performance were observed. From days 14 to 28, a cubic (p< 0.05) response was observed for ADG and ADFI with pigs fed 20 g SP kgÿ1
having greater ADG than pigs fed the control diet. In Experiment 2, dietary treatments (meal form) consisted of a control diet (no SP, fed for 6 weeks), 1 g SP kgÿ1
(fed for 6 weeks) or 2 g SP kgÿ1
(fed for 1, 2, 4, or 6 weeks). Pigs were switched to the control diet at the end of each SP feeding regimen. From days 0 to 14 after weaning, no differences in ADG or ADFI were observed. Pigs fed diets containing 1 or 2 g SP kgÿ1
for the entire 28 days had better feed ef®ciency (p< 0.02) than the treatments in which SP had been removed from the diet on day 7 or 14 after weaning. However, from days 0 to 42 after weaning, no differences in ADG or ADFI were observed. In Experiment 3, dietary treatments were arranged in a 22 factorial with the main effects of feed processing (meal versus pellet) with or without 2 g SP kgÿ1. From days 0 to 14 after weaning, adding SP to pelleted diets numerically tended to decrease ADG (SPfeed
83 (2000) 237±247
$
Contribution No. 99-360-J of the Kansas Agric. Exp. Sta., Manhattan 66506.
*Corresponding author. Tel.:1-785-532-4202; fax:1-603-676-5543.
E-mail address: dritz@vet.ksu.edu (S.S. Dritz).
1Food Animal and Health Management Center, College of Veterinary Medicine, Kansas State University,
Manhattan 66506-5606.
processing,p< 0.10), whereas adding SP to meal diets tended to improve ADG. From days 14 to 28 or days 0 to 28 after weaning, no differences in ADG, ADFI, or F/G were observed. In conclusion, the response to SP was inconsistent and occurred only with meal diets.#2000 Elsevier Science B.V. All rights reserved.
Keywords:Pigs; Algae; Performance
1. Introduction
Two-thirds of the Earth's biomass is comprised of more than 25 000 species of algae (Henrikson, 1997). Historians have discovered that alga were a major dietary component of ancient cultures and are still consumed by people today (Kay, 1991). Algae can be grouped into two categories: macroalgae (seaweeds); and microalgae (e.g.Chorellaspp.
and Spirulina spp.). Both classes of algae are used for human food, animal feed,
fertilizers, biochemicals, and the development of pharmaceuticals (Henrikson, 1997). Microalgae are considered as a suitable nutriental supplement because of their high protein content (500±700 g CP/kg) and their abundance of vitamins and minerals (Kay, 1991).Spirulina platensis (SP) are a species of microalga that have not been evaluated widely in animal feeding studies.
Spirulina platensisare grown organically in specialized ponds to provide a product that is free of contaminants (Henrikson, 1997). Qureshi (1995) observed that young poults fed 1000 to 10 000 ppm SP had heavier spleen and thymus weights than poults fed a control diet. Chicks fed SP also exhibited a higher clearance rate ofEscherichia coli(intravenous inoculation) from their circulation than did chicks fed a basal diet (Qureshi, 1995). Yap et al. (1982) conducted an experiment replacing dried skim milk withSpirulina maxima. Pigs fed high levels ofS. maxima(140 g/kg diet) had similar performance as those fed the diet containing skim milk.
Based on its potential to enhance growth, these experiments were designed to evaluate the effect of dietary SP on weanling pig performance.
2. Materials and methods
2.1. Animal care and use
The experimental protocols used in these studies were approved by the Kansas State University Institutional Animal Use Committee.
2.2. Animals and housing
Three experiments were conducted to evaluate the effects of SP on weanling pig performance. Pigs (PIC, L326C22) used in experiments 1 and 3 were reared in a commercial swine operation in northeast Kansas. At weaning, pigs were placed in an environmentally controlled nursery, in pens (1.21.5 m) with two nipple waterers, a
hole feeder, and woven wire ¯ooring. In Experiment 2, pigs (PIC, L42L19) were obtained from a closed production system located in central Kansas. Pigs were transported in an enclosed stock trailer for1 h without access to feed or water. They were housed in an all-in-all-out, off-site, environmentally regulated, nursery facility located a minimum of 0.8 km from other pig-rearing sites at Kansas State University. Pigs were weighed on arrival and then allotted to their respective pens. Each pen (1.2 m1.2 m) contained one nipple waterer, a ®ve-hole feeder, and metal bar ¯ooring. Nurseries were maintained at 348C for the ®rst week after weaning. Temperature was reduced by 1.58C each week, and air ¯ow was regulated to maintain pig comfort. Animals were provided ab libitum access to feed and water for the duration of the experiments.
2.3. Experiment 1
A total of 203 pigs (initially 3.70.85 kg and 11±12 days of age) were used in a 28-day growth trial. Pigs were blocked by weight and allotted randomly to one of four dietary treatments. There were eight or nine pigs/pen and six pens/treatment. In formulating diets, the amino acid values for SP were provided by the supplier (Table 1) and NRC (1988) values for soybean meal were used. The trial was divided into three phases to approximate a nutritional program similar to that used in commercial production. Three diets were used; the ®rst was fed from days 0 to 7 after weaning, the second from days 7 to 14 after weaning, and the third from days 14 to 28 after weaning. Pigs remained on their respective dietary treatments in all three phases.
All diets were maize±soybean meal based. The days 0±7 and 7±14 diets were fed in pellet form (4 mm diameter; Table 2). The diets fed from days 14 to 28 were fed in a meal form.Spirulina platensis(2, 5, and 20 g kgÿ1
) replaced soybean meal on an equal lysine
Table 1
Composition ofSpirulina platensisa
Item (g kgÿ1) Spirulina platensisb
Protein 620 (610)
Fat 55
Amino acids
Arginine 43 (39)
Cystine 6 (7)
Histidine 10 (10)
Isoleucine 35 (32)
Leucine 54 (51)
Lysine 29 (27)
Methionine 14 (14)
Phenylalanine 28 (26)
Threonine 32 (28)
Tryptophan 9 (6)
Tyrosine 30 (24)
Valine 40 (36)
aValues shown on an as-fed basis.
bAmino acid levels provided by the supplier, and analyzed values are provided in parentheses.
basis in the control diet to provide the additional experimental treatments. All diets contained a medication (carbodox, 55mg kgÿ1) and 3000 mg kgÿ1 (days 0±14) or 2000 mg Zn kgÿ1
(days 14±28) from zinc oxide for growth promotion. The pelleted diets (experiments 1 and 3) were conditioned with a 10 s retention time at 608C using a Master Model HD 1000 series California Pellet Mill equipped with a 3.2 cm effective thickness die. The corresponding pellet exit temperatures averaged 688C. Average daily gain (ADG), average daily feed intake (ADFI), and feed ef®ciency (F/G) were determined by weighing pigs and measuring feed disappearance on days 7, 14, 21, and 28 after weaning.
Table 2
Composition of basal diets (as-fed basis)
Dietary phases
Days 0±7a Days 7±14b Days 14±28c Days 28±42d
Ingredient (g kgÿ1)
Maize 335.6 399.2 581.7 660.4
Dried whey 250.0 200.0 100.0 ±
Soybean meale 124.7 232.4 245.6 305.4
Spray-dried animal plasma 67.0 25.0 ± ± Select menhaden ®sh meal 60.0 25.0 ± ±
Soybean oil 60.0 50.0 ± ±
Lactose 50.0 ± ± ±
Spray-dried blood meal 17.5 25.0 25.0 ±
Antibioticf 10.0 10.0 10.0 ±
Monocalcium phosphate 7.6 12.8 16.4 15.4
Limestone 4.8 7.5 10.0 9.7
Zinc oxideg 3.8 3.8 2.5 ±
Premixh 4.0 4.0 4.0 4.0
Salt 2.0 2.5 2.5 3.5
L-Lysine HCl 1.5 1.5 1.5 1.5
DL-Methionine 1.5 1.3 0.8 0.1
Chemical analysis(g kgÿ1)i
Experiment 1 223 224 206 ±
Experiment 2 218 228 200 203
Experiment 3 222 220 200 ±
aFormulated to contain g per kg of diet: lysine17, methionine4.8, Ca9, and P8. bFormulated to contain g per kg of diet: lysine16, methionine4.4, Ca9, and P8. cFormulated to contain g per kg of diet: lysine13, methionine3.6, Ca8.5, and P7.5. dFormulated to contain g per kg of diet: lysine12, methionine3.2, Ca7.5, and P7 (Experiment 2). eSpirulina platensisreplaced soybean meal on an equal lysine basis.
fProvided 55mg carbadox kgÿ1 experiments 1 and 3. In Experiment 2, additional maize replaced the
antibiotic.
gOnly included in experiments 1 and 3 to provide 3000 (days 0±14) or 2000 (days 14±28) mg Zn kgÿ1
of diet.
hPremix provided per kilogram of complete diet: Mn, 40 mg; Fe, 165 mg; Zn, 165 mg; Cu, 16 mg; I, 0.3 mg;
Se, 0.3 mg; vitamin A, 11 025 IU; vitamin D3, 1103 IU; vitamin E, 44 IU; menadione (menadione sodium
bisulfate complex) 4.4 mg; ribo¯avin, 9.9 mg; d-pantothenic acid, 33 mg; niacin, 55 mg; choline, 166 mg; and vitamin B12, 0.04 mg.
iValues for each respective diet represent the mean of all treatments.
2.4. Experiment 2
A total of 180 weanling pigs (initially 5.60.75 kg and 182 days of age) was used in a 42-day growth trial to examine the effect of duration of SP feeding on growth performance. Pigs were blocked by weight and allotted randomly to one of six dietary treatments. There were ®ve pigs/pen and six pens/treatment. The trial was divided into four phases: days 0±7, 7±14, 14±28, and 28±42 after weaning. Dietary treatments consisted of a control diet (no SP) fed for 6 weeks; 1 g SP kgÿ1fed for 6 weeks; and 2 g SP kgÿ1
fed for 1, 2, 4, or 6 weeks. At the end of each SP feeding regimen, pigs were switched to the control diet and remained on it for the remainder of the experiment.
The basal diets used for each phase were similar to those used in Experiment 1. The days 28±42 diet was maize±soybean meal-based diet formulated to 12 g total lysine kgÿ1
and did not contain any specialty protein sources. All diets fed in this experiment were in a meal form and did not contain growth promotional levels of Zn or a feed medication. Average daily gain, ADFI, and feed ef®ciency were determined by weighing pigs and measuring feed disappearance on days 7, 14, 21, 28, 35, and 42 after weaning.
2.5. Experiment 3
A total of 192 weanling pigs (initially 4.00.64 kg and 11±12 days of age) was used in a 28-day growth trial. This experiment was designed to examine the effects of SP fed in pelleted or meal-based diets on pig performance. Pigs were blocked by weight and allotted randomly to one of four dietary treatments. There were eight pigs/pen and six pens/treatment. The facilities, basal diets, feeding regimen, and experimental procedures were the same as those used in Experiment 1. Pigs were fed a control diet or diets containing 2 g SP kgÿ1
replacing soybean meal on an equal lysine basis. Both diets were fed in pellet and meal forms.
2.6. Chemical analysis
Samples of SP were collected and analyzed for amino acid concentrations (Table 1) using ion exchange chromatography following acid hydrolysis (Knabe et al., 1989). Methionine and cystine were determined following oxidation with performic acid (Moore, 1963). Tryptophan was determined following alkaline hydrolysis (LaRue, 1985). Analyzed values were similar to the nutrient values provided by the supplier that were used in diet formulation. Amino acid values for soybean meal (475 g CP kgÿ1
) were derived from published values (NRC, 1988). The amino acid pro®le of SP appears to be similar to that of soybean meal. All experimental diets were sampled and analyzed for crude protein (CP) (AOAC, 1990). Analyzed values were similar to calculated values (Table 2).
2.7. Statistical analysis
All experiments were analyzed as randomized complete block designs. Pigs were blocked by initial body weight and the pen was the experimental unit. Analysis of
variance was performed using the GLM procedures of SAS (1998). In Experiment 1, linear, quadratic, and cubic polynomials (Peterson, 1985) were evaluated for increasing levels of SP. In Experiment 2, data were analyzed as the mean of each SP level and the lengths of time each was fed. Treatment means were separated using the LSD test, which was protected by requiring rejection of experiment wide F-tests ( < 0.05) before application (Steel and Torrie, 1980). Experiment 3 was analyzed as a 22 factorial with the main effects of feed processing (meal or pellet) with or without 2 g SP kgÿ1and their interaction.
3. Results and discussion
Previous studies have evaluated higher inclusions (up to 330 g kgÿ1
) of microalgae as a protein replacement for soybean meal in weanling pig diets (Rigor et al., 1980; Yap et al., 1982; Hugh et al., 1985). The current study was conducted using low inclusions of SP because of the improvement in performance observed with low levels in poultry trials by Qureshi et al. (1996) and the fact that little research has been conducted with these lower levels in weanling pigs. The analyzed amino acid values of the SP used in this experiment were in general agreement with the values used in diet formulation (Table 1). This indicates that the low inclusion levels of SP used in the experiment had little effect on the amino acid balance of the diets used in the experiments.
3.1. Experiment 1
From days 0 to 7 and days 0 to 14 after weaning, increasing SP had no effect on growth performance relative to that of pigs fed the control diet (Table 3). From days 7 to 14 after weaning, no differences in ADG were observed. However, ADFI numerically increased, decreased, and then increased again (cubic,p< 0.10) in response to increasing SP. Feed ef®ciency tended to become poorer (linear,p< 0.10) with increasing SP.
From days 14 to 28 after weaning, ADG and ADFI responded in a cubic (p< 0.05) fashion as SP increased. Pigs fed 2 g SP kgÿ1
had the best ADG which was greater than those fed the control diet or diet containing 5 g SP kgÿ1. Daily feed intake was greatest for pigs fed either 2 or 20 g SP kgÿ1compared with those fed 5 g SP kgÿ1, with those fed the control diet having intermediate ADFI. Feed ef®ciency was not affected.
For the entire experimental period (days 0±28 after weaning), ADG tend to (cubic,
p< 0.08) and ADFI (cubic,p< 0.05) increased, decreased, and then increased again with increasing SP (Table 3). Feed ef®ciency was unaffected by SP.
All diets were pelleted during the ®rst two weeks of the experiment. During the second half of the experiment, days 14±28, pigs fed 2 g SP kgÿ1
had increased ADG compared with those fed the control diet. The cubic response in growth and feed intake happened to coincide with the feeding of meal-based diets. It was speculated that high temperatures associated with the pelleting process may have damaged or inactivated the SP. Similar heat stability problems have been observed in pig diets with supplemental enzymes or probiotics that have been subjected to thermal processing (Gunther, 1986; Swanson and Hancock, 1989; Maloney et al., 1998).
The other potential explanation for the improved performance from days 14 to 28 with no response from days 0 to 14 was the duration of SP feeding. If the improvement in growth performance were mediated through an enhancement in immune function, several days of SP feeding might be needed for a response to occur. Qureshi et al. (1996) fed increasing levels of SP to chicken poults and evaluated immunological performance after injection of sheep red blood cells. No differences in total Ig were observed 7 days after the ®rst injection. However, 7 days after a second injection, higher total Ig concentrations were observed in all poults fed SP. This suggests that the immune enhancement response is not immediate. Therefore, the objectives of two subsequent experiments were to evaluate feeding duration of SP (Experiment 2) and to explore the effects of feed processing on SP (Experiment 3).
3.2. Experiment 2
In Experiment 2, SP was evaluated over a 6 week period. Medication and growth promotants were not included in the diet to ensure that any possible growth improvement was from the inclusion of SP. Because of cubic responses observed in Experiment 1, a lower level (1 g kgÿ1
) of SP was also evaluated. From days 0 to 14 after weaning, no
Table 3
Effect of increasingSpirulina platensison weanling pig performance (Experiment 1)a
Item Spirulina plantensis(g kgÿ1) SEM Probability (P<)
0 2 5 20 Linear Quadratic Cubic
Days 0±7
ADG (g) 127 113 122 140 9.2 0.11 0.45 0.35 ADFI (g) 144 139 145 151 4.5 0.15 0.79 0.36 F/G 1.14 1.22 1.18 1.07 0.06 0.15 0.39 0.42 Days 7±14
ADG (g) 223 238 214 216 11.8 0.44 0.68 0.22 ADFI (g) 239 264 246 254 10.3 0.69 0.76 0.10 F/G 1.07 1.10 1.14 1.18 0.05 0.10 0.38 0.96 Days 0±14
ADG (g) 175 176 168 178 8.9 0.73 0.51 0.72 ADFI (g) 192 201 195 202 6.4 0.40 0.88 0.31 F/G 1.09 1.14 1.16 1.14 0.03 0.55 0.25 0.70 Days 14±28
ADG (g) 288 324 291 309 12.4 0.62 0.99 0.04 ADFI (g) 460 491 443 486 13.4 0.28 0.24 0.03 F/G 1.60 1.52 1.52 1.56 0.05 0.97 0.26 0.44 Days 0±28
ADG (g) 231 250 230 243 8.1 0.60 0.73 0.08 ADFI (g) 326 346 319 341 8.9 0.34 0.41 0.05 F/G 1.40 1.39 1.39 1.40 0.02 0.74 0.56 0.70
aA total of 203 weanling pigs (initially 3.7 kg and 11±12 days of age) with eight or nine pigs per pen and six
replacements per treatment.
signi®cant differences in ADG or F/G were observed among the treatment groups (Table 4). However, pigs fed either 1 or 2 g SP kgÿ1
showed a 20% numerical improvement in ADG compared to pigs fed the control diet as a result of a trend for increased ADFI (p< 0.07). During the initial period after weaning, ADFI tended to increase with the inclusion of SP in the diets, which is consistent with the results when pigs were fed meal diets of Experiment 1.
From days 14 to 28 or days 0 to 28 after weaning, pigs fed 2 g SP kgÿ1for only 2 weeks had greater ADFI (p< 0.01) than any other treatment group. The increase in ADFI numerically improved ADG. Pigs fed diets containing 1 or 2 g SP kgÿ1for the entire 28 days had better feed ef®ciency (p< 0.02) than the treatments in which SP had been removed from the diet on day 7 or 14 after weaning.
For the ®fth and sixth week after weaning, (days 28±42) no differences were observed in ADG, ADFI, or F/G. For the entire experimental period (days 0±42 after weaning), no differences in ADG or ADFI were found. However, pigs fed 1 g kgÿ1
SP tended to have the best feed ef®ciency (p< 0.09) of any treatment group.
Hugh et al. (1985) evaluated growth performance on 3- to 4-week-old weanling pigs fed diets that contained 0, 15, 30, 60, and 90 g SP kgÿ1
replacing soybean meal on an equal lysine basis. Pigs fed 15 g SP kgÿ1
had numerically higher ADG and ADFI compared to pigs that were fed the other treatments. These ®ndings suggest that lower levels of SP may have a speci®c mode of action instead of just being a protein replacement for soybean meal.
3.3. Experiment 3
From days 0 to 7 after weaning, feeding SP had no effect on ADG or F/G. An SP by feed processing interaction (p< 0.03) was observed for ADFI (Table 5). Pigs fed SP in pelleted diets had lower ADFI than pigs fed SP in meal diets. Feeding pelleted diets tended to improve ADG (p< 0.07) and improved F/G (p< 0.01) compared to meal diets. From days 7 to 14 after weaning, feeding SP had no effect on ADG, ADFI, or F/G. From days 0 to 14 after weaning, pigs fed SP in pelleted diets tended to have a decrease in ADG (SPprocessing, p< 0.10), whereas those fed SP in meal diets tended to have increased ADG. A similar trend (SPprocessing,p< 0.06) was also noted for ADFI. Pigs fed pelleted diets had better F/G (p< 0.01) than pigs fed meal-based diets.
From days 14 to 28 after weaning, ADG, ADFI, and F/G were unaffected by SP. For the entire experimental period, days 0 to 28 after weaning, SP fed in either a meal or pellet diet had no effect on ADG, ADFI, or F/G. Feed ef®ciency (p< 0.01) was better for pigs fed pelleted diets than pigs fed meal diets.
The favorable results with SP resulted from feeding meal diets to weanling pigs. The results from Experiment 3 suggest that feed processing may affect the palatability of diets containing SP. Average daily feed intake was signi®cantly lower when pigs were fed SP in a pelleted diet than in a meal diet. This supports the response to feed intake when pigs were fed meal diets in Experiment 1. Although not signi®cantly different, pigs fed SP had numerically better growth performance than pigs in other treatments.
Another possible explanation for the varied results with SP is the health status of the pigs used in the experiments. Phycocyanin, a pigment found in blue-green algae, is
thought to be responsible for the immunomodulatory properties associated with SP. Although SP normally contains 60±80 g phycocyanin kgÿ1
, the particular product used in the current experiments was standardized to 125±140 g kgÿ1
(R. Henson, Earthrise Co.,
Table 4
Effects of feeding duration ofSpirulina platensison weanling pig performance (Experiment 2)a
Itemb 0 1 (g kg)ÿ1 2 (g kg)ÿ1c Spirulina removed on SEM Probability
7b 14b 28 (P<)
Days0±7
Replications 6 6 24
ADG (g) 106 132 131 12.6 0.32
ADFI (g) 127 160 153 9.0 0.07
F/G 1.25 1.23 1.25 0.11 0.99
Days7±14
Replications 6 6 18 6
ADG (g) 279 279 309 301 14.4 0.26
ADFI (g) 323 297 337 348 18.1 0.29
F/G 1.15 1.06 1.09 1.18 0.04 0.20
Days0±14
Replications 6 6 18 6
ADG (g) 193 206 222 210 12.2 0.29
ADFI (g) 225 228 247 247 12.1 0.40
F/G 1.17 1.11 1.11 1.19 0.03 0.11
Days14±28
Replications 6 6 12 6 6
ADG (g) 484 483 483 479 503 12.6 0.72
ADFI (g) 728 c 686 c 711 c 742 c 804 d 19.2 0.004 F/G 1.52 c,d 1.41 c 1.47 c 1.56 d 1.60 d 0.04 0.02
Days0±28
Replications 6 6 12 6 6
ADG (g) 338 344 350 344 367 10.7 0.46
ADFI (g) 476 c 457 c 473 c 494 c 534 d 14.4 0.01 F/G 1.42 d,e 1.32 c 1.35 c,d 1.44 e 1.46 e 0.03 0.004
Days28±42
Replications 6 6 6 6 6
ADG (g) 703 702 675 702 706 684 22.3 0.61 ADFI (g) 1145 1151 1111 1164 1159 1148 27.5 0.80 F/G 1.63 1.63 1.65 1.66 1.64 1.68 0.02 0.69
Days0±42
Replications 6 6 6 6 6 6
ADG (g) 460 464 455 464 480 460 13.0 0.60 ADFI (g) 699 685 684 718 742 691 17.0 0.14 F/G 1.52 1.48 1.50 1.55 1.55 1.50 0.02 0.09
aA total of 180 weanling pigs (initially 5.6 kg and 18 days of age) with ®ve pigs per pen and six replications
per treatment.
bMeans in same row with different letters differ (p< 0.05).
cRepresents mean of all pens remaining on 2 g spirulina kgÿ1for each respective weight period.
personal communication). Phycocyanin has been shown to have antioxident and anti-in¯ammatory properties in mice (Romay et al., 1998) and to provide protection to liver enzymes during induced hepatotoxicity in rats (Vadiraja et al., 1998). These potential health bene®ts of SP may have been masked by the inclusion of medication and growth promotants in experiments 1 and 3. Even though no growth promotants or antibiotics were used in Experiment 2, the implementation of an off-site facility may have provided an environment suitable for excellent pig performance without any additional health-promoting ingredients. Additional studies may be warranted in production systems where health conditions may be compromised by management or facilities.
4. Conclusions
The results of these three experiments showed inconsistent and minimal improvement in growth performance when pigs were fed diets containing Spirulina platensis. The health status of the pigs and feed processing methods (i.e. pelleting) may be factors affecting the effectiveness ofSpirulina plantensis.
Table 5
Effects of feedingSpirulina platensisin a meal or pelleted diet on weanling pig performance (Experiment 3)a
Item Meal Pelleted SEM Probability (P<)
Control Spirulina Control Spirulina Processing Spirulina Spirulina
processingb
Days 0±7
ADG (g) 105 116 141 126 11.5 0.07 0.84 0.29 ADFI (g) 161 176 158 147 5.4 0.009 0.70 0.03 F/G 1.55 1.55 1.16 1.20 0.10 0.001 0.84 0.82 Days 7±14
ADG (g) 253 260 248 248 8.9 0.36 0.74 0.68 ADFI (g) 345 344 313 294 10.7 0.002 0.36 0.41 F/G 1.36 1.35 1.26 1.19 0.06 0.02 0.42 0.51 Days 0±14
ADG (g) 179 188 194 187 4.5 0.15 0.89 0.10 ADFI (g) 253 260 234 220 5.2 0.001 0.50 0.06 F/G 1.41 1.40 1.21 1.18 0.04 0.001 0.61 0.81 Days 14±28
ADG (g) 338 348 312 330 10.1 0.05 0.20 0.67 ADFI (g) 489 499 460 470 11.1 0.02 0.38 0.99 F/G 1.45 1.44 1.48 1.42 0.05 0.97 0.46 0.69 Days 0±28
ADG (g) 259 268 253 259 5.3 0.16 0.18 0.78 ADFI (g) 371 380 347 345 6.8 0.001 0.60 0.49 F/G 1.44 1.43 1.37 1.33 0.04 0.05 0.50 0.71
aA total of 180 weanling pigs (initially 4 kg and 11±12 days of age) with eight pigs per pen and six
replications per treatment.
bInteraction ofSpirulinaand pellets.
Acknowledgements
We thank Eichman Brothers, St. George, KS for the use of animals and facilities in experiments 1 and 3 and to Jason Sawyer and Rusty Stott for assistance in data collection. We also thank Earthrise Co., Tollhouse, CA for providing the Spirulina platensis and partial ®nancial support.
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