Trace mineral levels evaluated for swine

Trace mineral levels evaluated for swine

*John H. Goihl is president of Agri-Nutrition Services Inc., Shakopee, Minn. To expedite answers to questions concerning this article, please direct inquiries to Feedstuffs, Bottom Line of Nutrition, 7900 International Dr., Suite 650, Bloomington, Minn. 55425, or email [email protected]

A SWINE diet is composed of many nutrients — including energy, amino acids, macrominerals, vitamins and trace minerals — and the formulation of swine diets involves combining the best-cost feed ingredients into a complete feed to meet the pig's nutritional needs for its age, size, production status and genetic potential.

The macro-minerals calcium and phosphorus are generally sourced from limestone and dicalcium or monocalcium phosphate — all of which contain appreciable amounts of micro-minerals, iron and manganese — which can supply levels for grower/finisher pigs that are often greater than National Research Council (NRC) requirements.

However, the micro-mineral content and bioavailabilities are variable and largely unknown. Consequently, the micro-mineral contributions of these ingredients are generally ignored in diet formulations and are considered to contribute to a margin of safety.

Research reports have indicated inconsistent results on the supplementation of micro-minerals and vitamins in grower/finisher diets. When there was no supplementation of micro-minerals, the results were either reduced performance with no difference in carcass characteristics or no effect on pig performance or carcass characteristics.

Swine researchers D.W. Gowanlock, D.C. Mahan, J.S. Jolliff and S.J. Moeller at The Ohio State University and G.M. Hill at Michigan State University designed a study to investigate the dietary effects of copper, iron, manganese and zinc levels below and up to NRC recommendations and the addition of only zinc and iron to a non-fortified micro-mineral basal diet for grower/finisher pigs.

The study utilized 222 pigs with an initial bodyweight of approximately 24.3 kg that were fed to a final bodyweight of approximately 115 kg.

All treatments were corn/soybean meal diets with phytase. Selenium was added at 0.3 mg/kg and iodine at 0.14% to all diets. Ractopamine was added at 10 mg/kg to all phase III diets for the last three weeks. Supplemental calcium was provided from ground limestone and phosphorus from 18.5% dicalcium phosphate. Supplemental copper, iron, manganese and zinc were supplemented as mineral proteinates.

The pigs were allotted to the following treatments: (1) no added copper, iron, manganese or zinc, (2) diet 1 plus 50% of NRC levels for copper, iron, manganese and zinc, (3) diet 1 plus 100% of NRC levels for copper, iron, manganese and zinc (which provided 3.5 mg of copper, 50 mg of iron, 2 mg of manganese and 50 mg of zinc per kilogram of diet), (4) diet 1 plus 25 mg/kg of zinc, (5) diet 1 plus 50 mg/kg of zinc and (6) diet 1 plus 50 mg/kg of iron.

The diets were fed ad libitum for three growth phases: phase I from 20 kg to 50 kg, phase II from 50 kg to 80 kg and phase III from 80 kg to 115 kg.

The pigs were allotted six pigs per pen for two replicates and five pigs per pen for five replicates. The pigs were housed in pens that were 50% solid concrete floors and 50% slatted floors separated by steel-rod grates.

Pig weights and feed disappearance were obtained at the beginning of the experiment and again when the pen averaged the weight of diet change between phases. Also, blood was drawn from the jugular vein from three pigs per pen between phases for later analysis at the same time pen weights were obtained.

At approximately 115 kg, three pigs from each pen were harvested to obtain various carcass measurements and assessments of meat quality.

 

Results

Table 1 summarizes the analyzed innate micro-mineral concentration of each diet fed for each phase.

Table 2 summarizes the growth performance of the pigs fed the six treatments. Based on these performance results, the researchers indicated that during each growth phase and for the entire experimental period, there were no significant effects among treatments.

Table 3 summarizes the pigs' hemoglobin and hematocrit values. The results, as interpreted by the researchers, indicated that the hemoglobin concentrations and hematocrit volumes were not affected by treatment during each phase or for the entire experiment. This suggests that the innate supplies of the evaluated trace minerals were adequate to support these hematological measurements.

Table 4 summarizes the carcass measurements, and the researchers indicated that there were no effects of treatment on the carcass measurements obtained. The researchers also reported no differences in subjective color scores and ultimate pH among treatments.

The results of this study indicate that a typical corn/soybean meal diet fortified with limestone (1.00-1.15%) and dicalcium phosphate (1.05-1.50%) may have adequate innate micro-minerals to support growth, hematology and carcass traits of grower/finisher pigs.

The total calcium, phosphorus and lysine of the three diets fed are summarized in Table 5.

Using the total-tract apparent digestibility percentages for the four micro-minerals, the digestible micro-mineral concentrations exceeded NRC requirements for manganese and iron but were marginal for copper and deficient for zinc. However, the NRC requirements are based on total micro-mineral content, not digestible micro-mineral content. Also, micro-mineral levels are variable in feed ingredients.

The researchers offered other considerations that may have influenced the results of this study, including:

* The dietary regimen for the pigs during the nursery period may have contributed a carryover of micro-minerals into this study.

* Phytase was added to the diets to enhance the availability of micro-minerals in addition to phosphorus.

* The combination of the elements in the digestive tract may reduce the utilization of zinc or other microminerals.

* Feeding organic micro-minerals may also be more digestible, thus causing reduced chelation in the digestive tract.

In this study, the addition of the organic zinc along with ractopamine produced no improvement in performance.

 

The Bottom Line

Under the conditions of this study, the results would suggest that supplemental micro-minerals — copper, iron, manganese and zinc — may not be needed in typical corn/soybean diets for pigs. However, in typical commercial conditions, with the variability that exists in feed ingredients and herd health status, the researchers recommended a supplemental level of at least 50% of the NRC recommendations from organic micro-mineral sources.

 

Reference

J. Anim. Sci. Vol. 91. No. 12.

 

1. Analyzed innate micro-mineral concentration of each diet for each phase

 

-Innate micro-mineral

Total-tract

Avg. dig.

NRC requirements

 

concentration, mg/kg-

apparent

mineral

for 50-80 kg

Mineral

Phase I

Phase II

Phase III

digestibility, %

concentration, mg/kg*

pig, mg/kg

Copper

6.57

9.23

6.00

44.4

3.22

3.5

Iron

200.70

203.30

186.10

37.3

73.20

50

Manganese

20.21

33.66

17.85

21.7

5.19

2

Zinc

35.42

58.53

36.57

25.3

11.01

50

*Average of the three diets x % digestibility.

 

2. Growth performance

 

-Treatment-

 

1

2

3

4

5

6

Initial bodyweight, kg

24.1

24.5

23.9

24.3

24.7

24.6

Final body weight, kg

118.2

118.8

116.7

118.8

120.0

117.8

Avg. daily gain, kg

1.08

1.08

1.07

1.08

1.09

1.07

Avg. daily feed intake, kg

2.56

2.58

2.68

2.51

2.63

2.52

Gain:feed

0.42

0.41

0.40

0.43

0.41

0.43

 

3. Hemoglobin and hematocrit values (average of three samples from each phase

 

-Treatment-

 

1

2

3

4

5

6

Hemoglobin, g/dL

13.1

12.8

12.8

13.1

12.9

13.1

Hematocrit, %

40.3

39.5

40.0

39.9

39.7

40.1

 

4. Summary of carcass measurements

 

-Treatment-

Criteria

1

2

3

4

5

6

Hot carcass weight, kg

87.58

87.93

85.83

88.50

90.17

87.63

Back fat, mm

21.52

21.80

21.53

22.65

22.87

22.92

Loin muscle area, sq. cm

46.23

46.89

45.68

47.17

47.54

46.32

Fat-free lean, %

52.60

52.58

52.50

52.17

52.12

51.95

Dressing, %

76.90

76.47

76.35

77.17

76.97

76.82

 

5. Total calcium, phosphorus and lysine of diets

 

-Phase-

Nutrient

1

2

3

Total calcium, %

0.81

0.81

0.70

Total phosphorus, %

0.65

0.59

0.55

Total lysine, %

1.20

1.10

1.10

Phytase, FTU/kg of diet

1,000

1,000

1,000

 

Volume:86 Issue:04

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