Effect of Dietary Zinc Source and Level on Performance, Zinc Status and Immune Response of Nursery Pigs

By J.W. Spears, J.T. Blackwelder, T.A. Armstrong and E. van Heugten

North Carolina State University Swine Nutrition Research from 1998-2000. Recent studies with swine have indicated that replacing a portion of the inorganic trace minerals with chelated forms can improve performance. Veum et al. (1995) reported that replacing 15 to 36% of the supplemental inorganic zinc, iron, copper, and manganese with chelated metal proteinates increased gain and gain:feed in nursery pigs. Supplementing sows with a mixture of zinc, copper, and manganese proteinate improved reproductive performance compared with sows supplemented with only inorganic trace minerals (Mirando et al., 1993). There has been increasing environmental concerns recently regarding excretion of zinc in swine waste. Chelated forms of zinc may exhibit greater bioavailability than commonly used inorganic forms of zinc. Therefore, use of zinc proteinate in swine diets may allow for a lower inclusion rate in the diet and thus, reduced excretion of zinc in waste. The present study was conducted to determine the effects of: 1) zinc level and 2) replacing 25 to 50% of supplemental inorganic zinc with zinc proteinate on performance, immune response, and zinc status of nursery pigs.

Materials and Methods

One hundred ninety-two crossbred weanling pigs (3-weeks-old) were allotted to 24 pens based on weight, sex, and litter origin. Pens were randomly assigned to treatments. Each pen contained 8 pigs and each treatment consisted of 4 replicate pens. Treatments consisted of: 1) 50 ppm supplemental zinc (100% zinc sulfate (ZnSO₄)), 2) 50 ppm supplemental zinc (25% zinc proteinate (ZnP), 75% ZnSO), 3) 50 ppm supplemental zinc (50% ZnP, 50% ZnSO₄), 4) 150 ppm supplemental zinc (100% ZnSO₄), 5) 150 ppm supplemental zinc (25% ZnP, 75% ZnSO₄), 6) 150 ppm supplemental zinc (50% ZnP, 50% ZnSO4). Zinc proteinate (Bioplex zinc) was provided by Alltech, Inc.

The nursery phase lasted a total of 35 days. A two-phase diet system was used. Phase 1 diet was fed for the first 14 days following weaning and the phase 2 diet was fed the last 21 days of the nursery period. Pigs were weighed and feed intake was determined weekly.

Blood samples were obtained from 8 pigs per treatment on days 14 and 28 for determination of plasma zinc concentrations and alkaline phosphatase activity. In vivo cellular immune response was investigated on day 32 of the study using a phytohemagglutinin (PHA) skin test. Eight pigs per treatment were injected subcutaneously with 0.1 ml PHA (150 μg/ml). Skin thickness was measured using calipers at 0, 6, 12, 24, and 48 hours after injection. Thirty-six pigs were killed at
the end of the study and samples of liver, bone, and pancreas were collected for zinc analysis.

Results and Discussion

Pigs supplemented with 50 ppm of zinc gained faster (P < .05) and consumed more (P < .10) feed than pigs supplemented with 150 ppm of zinc during the first 14 days of the study (Table 1). Zinc level did not affect gain, feed intake, or gain:feed during phase 2 or for the entire nursery period. In pigs fed 50 ppm of zinc, replacing a portion of the ZnSO₄ with ZnP tended to improve gains and feed intakes during phase 1. In the 150 ppm zinc treatments, pigs that received 50% of their supplemental zinc from ZnP had a higher (P < .05) gain and gain:feed than pigs fed 25% of zinc from ZnP over the entire nursery period.

Alkaline phosphatase, a zinc dependent enzyme, was not affected by zinc level or source. Plasma zinc concentrations were higher in pigs supplemented with 150 ppm compared to those supplemented with 50 ppm of zinc. Source of zinc did not affect plasma zinc concentrations. Liver, bone, and pancreas zinc concentrations were higher (P < .05) in pigs supplemented with 150 ppm of zinc. In pigs fed the higher zinc level, replacing 25 or 50% of the ZnSO₄ with ZnP resulted in decreased zinc concentrations in bone but not in liver or pancreas. In vivo cellular immune response was not significantly affected by zinc level or source. However, pigs receiving ZnP tended to have a greater skinfold thickness response to PHA administration than pigs receiving only ZnSO₄.

Table 1. Effect of zinc level and source on performance of nursery pigs

	Treatment: 50 ppm zinc			Treatment: 150 ppm zinc			SE
	ZnSO₄	25% ZnP	50% ZnP	ZnSO₄	25% ZnP	50% ZnP	SE
Gain, kg/d
Day 0 – 14	.271^ab	.287^a	.296^a	.251^b	.240^b	.277^ab	.013
Day 15 – 35	.498^ab	.536^a	.495^ab	.515^ab	.480^b	.527^ab	.018
Total	.408^ab	.437^a	.416^ab	.411^ab	.385^b	.429^a	.013
Intake, kg/d
Day 0 – 14	.407^a	.425^ab	.461^b	.416^a	.394^a	.415^a	.015
Day 15 – 35	.886^a	1.004^b	.948^ab	.912^a	.916^a	.928^ab	.029
Total	.697^a	.775^b	.756^ab	.716^ab	.711^a	.725^ab	.021
Gain:Feed
Day 0 – 14	.664	.678	.643	.606	.609	.669	.031
Day 15 – 35	.562^ab	.535^ab	.523^a	.566^ab	.524^ab	.568^b	.015
Total	.585^ab	.565^ab	.552^ab	.575^ab	.542^a	.592^b	.015

Means in a row without a common superscript differ (P < .05)

Summary

Results of this study indicate that 50 ppm of supplemental zinc is adequate for growth and immunity in nursery pigs. Replacing 25 or 50% of the supplemental inorganic zinc with zinc proteinate tended to improve gain and feed intake of pigs receiving 50 ppm of added zinc.

References

Mirando, M.A., D.N. Peters, C.E. Hostetler, W.C. Becker, S.S. Whiteaker, and R.E. Rompala. 1993. Dietary supplementation of proteinated trace minerals influences reproductive performance of sows. J. Anim. Sci. 71 (Suppl. 1):180.

Veum, T.L., D.W. Bollinger, and M. Ellersieck. 1995. Proteinated trace minerals and condensed fish protein digest in weanling pig diets. J. Anim. Sci. 73 (Suppl. 1):186.

Effect of Dietary Zinc Source and Level on Performance, Zinc Status and Immune Response of Nursery Pigs

Table 1. Effect of zinc level and source on performance of nursery pigs

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