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Nutrient Needs Of High Lean Pigs

Tim S. Stahly, Ph.D.
Department of Animal Science
Iowa State University, Ames, Iowa, USA

The nutrient needs of pigs are dependent on the type of the biological processes occurring in the pig and the rates at which the processes are being expressed. High lean genetic strains of pigs normally exhibit greater body maintenance processes and proteinaceous tissue (i.e., muscle, bone, and visceral organs) growth, but lower rates of fatty tissue accretion. These patterns of tissue growth result in body gains higher in protein, macrominerals, and water but lower in fat and energy content. The higher water and lower energy content of gain in high lean pig results in less feed and feed energy being required per unit of body weight gain compared with moderate lean pigs. Similarly, voluntary energy intake is less, even though body weight gains are equal to or greater than moderate lean pigs.

The greater productivity of high lean pigs reared in high health herds are even more striking when compared with the expected performance of pigs on which the current National Research Council’s nutrient requirements for swine (NRC, 1988) are based (Table 1). In this comparison, high lean pigs (barrows only) fed from 11 to 22, 22 to 44, 44 to 110, and 110 to 242 pounds, respectively, required .74, .83, .91, and .85 pounds less feed per pound of body weight gain than those assumed in the NRC (1988). Furthermore, their daily gains were .46, .51, .56, and .17 pounds greater in the respective four stages of growth.

Table 1. Growth and feed utilization of pigs.^a

	Pig	Pig weight, lb
Criteria	Type	11-22	22-44	44-110	110-242
Daily feed, lb	NRC 1988^b	1.01	2.09	4.18	6.85
	Mod lean^c	1.17	2.01	4.16	6.75
	High lean^c	1.15	1.94	3.81	6.00^d
Daily gain, lb	NRC 1988	.55	.99	1.54	1.81
	Mod lean	.96	1.42	2.01	2.11
	High lean	1.01	1.50	2.10	1.98^d
Feed/gain	NRC 1988	1.84	2.11	2.71	3.79
	Mod lean	1.22	1.60	2.07	3.27
	High lean	1.10	1.28	1.80	2.94^d
^aPigs allowed to consume feed (no supplemental fat, nutritionally adequate) and water ad libitum. ^bExpected pig (barrows-gilts) performance, Nutrient Requirements for Swine, NRC (1988). ^cGrowth data of pigs (barrows only) in Iowa State University studies (1993-1997). Four and seven sources of high and moderate lean pigs, respectively, were reared via a MEW or SEW scheme in a thermal neutral climate. ^dData from only trial (strain) reported for 110-242 pound weight category.

Vitamins

The high rates of proteinaceous tissue growth in high lean strains cause these animals to have a greater dietary need for the nutrients required to fuel these processes. Vitamins, particularly B vitamins, are key elements in proteinaceous tissue growth via their role in energy and protein metabolism. In recent work at our research station, the dietary needs of pigs with a high lean growth capacity for a group of five B vitamins were evaluated. The five test vitamins (niacin, pantothenic acid, riboflavin, B₁₂, and folic acid) were chosen because they are involved in fueling proteinaceous tissue accretion. All other vitamins were provided at 600% of the NRC (1988) estimated requirement.

Pigs with both a high and moderate genetic capacity for lean growth were evaluated. All pigs were reared via a medicated-early-weaning (MEW) scheme to minimize the level of chronic immune system activation in the pigs, thus allowing maximum accretion of proteinaceous tissue to occur. High lean pigs fed from 20 to 62 pounds responded linearly to increasing dietary concentrations of the five test vitamins up to 470% of the NRC (1988) estimated need for 11- to 22-pound pigs (Table 2). In moderate lean pigs, daily gains and efficiency of feed utilization were maximized by dietary B vitamin concentrations of 370 and 270% of NRC (1988), respectively. Inadequate intakes of the test vitamins in the high lean pigs lowered daily gains by about .08 pounds and increased feed required per unit of gain by .07 pounds for each reduction in the test vitamins equivalent to 100% of the NRC (1988) requirement. Based on these data, high lean, high health pigs have greater dietary needs for one or more of the five test B vitamins than current NRC (1988) estimates.

Table 2. Response of high and moderate lean pigs to dietary B vitamin concentrations.^a,b

	Pig	Dietary B vitamins, % NRC for 5-10 kg pigs^b
Criteria	Strain	70	170	270	370	470
Daily feed, lb	High lean	2.05	1.97	2.07	2.06	2.06
	Mod lean	2.20	2.11	2.13	2.23	2.24
Daily gain, lb	High lean	1.30	1.33	1.47	1.52	1.58
	Mod lean	1.26	1.26	1.36	1.42	1.43
Feed/gain	High lean	1.57	1.48	1.41	1.35	1.31
	Mod lean	1.74	1.69	1.57	1.58	1.57
^aStahly et al. (1995). Pigs allowed to consume diets ad libitum from 20 to 62 pounds body weight. ^bThe five test B vitamins were niacin, pantothenic acid, riboflavin, B₁₂, and folacin. A basal diet was supplemented with synthetic sources of the five test vitamins to provide 70, 170, 270, 370, and 470% of the NRC (1988) estimated requirement for 5 to 10 kg pigs. All other vitamins were provided at 600% of the NRC (1988) estimated requirements.

The vitamin thiamine also is closely involved in fueling proteinaceous tissue growth. However, thiamine concentrations in feedstuffs normally are 300 to 400% of the current estimated needs of pigs (NRC, 1988). Dietary thiamine concentrations equivalent to 200% of NRC (1988) estimates for 11- to 22-pound pigs have been reported to be adequate in high lean, high health pigs fed from 22 to 88 pounds (Table 3).

Table 3. Response of high lean pigs to dietary thiamine concentrations.^a

	Dietary thiamine, % NRC for 5-10 kg pigs^b
Criteria	200	330	460	590	720
Daily feed, lb	2.45	2.50	2.47	2.38	2.42
Daily gain, lb	1.73	1.70	1.68	1.63	1.71
Feed/gain	1.42	1.47	1.47	1.46	1.42
a Stahly and Cook (1996b). Pigs allowed to consume diets ad libitum from 28 to 88 pounds body weight. ^bAll other vitamins were provided at 600% of the NRC (1988) estimated requirements for 5 to 10 kg pigs.

The needs for fat soluble vitamins (i.e., vitamins A, D, E, and K) in high lean pigs have not been well documented. Because the major role of these vitamins involve tissue protection and cell integrity, it is hypothesized the need for these vitamins will be more dependent on the level of antigen exposure or oxidative stress than genetic capacity for proteinaceous tissue growth (Cousins, 1996; Stahly et al., 1997).

Macrominerals

Phosphorus is a major component of proteinaceous tissues. Specifically, tissue phosphorus content averages .206% in muscle, 3.16% in bone, .175% in offal, .071% in skin, and .036% in fatty tissue. In high lean pigs, muscle and bone growth accounts for 25 to 35% and 55 to 65%, respectively, of the daily phosphorus accrued in pigs (Bertram, 1995). High lean pigs respond to higher dietary available phosphorus concentrations than current NRC (1988) estimates (Table 4). Available phosphorus represents the amount of phosphorus in a feedstuff or diet that can be digested and, thus, made available to the pig. High lean pigs weighing 10, 40, 70, 100, 130, 160, 190, 220, and 250 pounds are estimated to require, respectively, 4.0, 3.8, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, and 3.0 grams of available dietary phosphorus per pound of daily body weight gain. These values represent an additional .4 to .7 g of available phosphorus per pound of weight gain than NRC (1988) estimates for similar weight pigs. These greater phosphorus needs are the result of the greater accretion of high phosphorus-containing tissues in the high lean strains. As the pig matures, less available phosphorus is needed per pound of body weight gain. This pattern reflects the changes in the rate at which high- and low-phosphorus tissues are being deposited. Bone growth predominates in the young pig, muscle growth in the developing pig, and fatty tissue growth in the finishing pig.

Table 4. Responses of high lean pigs to dietary available phosphorus (P) concentrations.^a

	Dietary available P, %
Criteria	.080	.110	.155	.222	.323	.473
Pig weight gain, lb	120	120	120	120	120	120
Avail P intake, g	118	158	203	274	390	561
Days	76.8	67.1	62.5	57.0	58.0	55.9
Feed, lb	326	316	289	272	266	260
a Adapted from Bertram (1995). Pigs (barrows) self-fed corn and soybean meal diets from 42 to 162 pounds body weight.

The optimum dietary concentration of available phosphorus for a particular weight pig seems to be that which maximizes rate and efficiency of proteinaceous tissue but maintains body phosphorus stores in bone. Inadequate dietary phosphorus intakes slow body weight gain, lower efficiency of feed utilization, and increase the body content of low phosphorus tissues (i.e., fatty tissue.). When receiving inadequate dietary phosphorus, high lean pigs will mobilize body phosphorus stores in bone and, to a limited extent, in muscle, but not to the extent needed to optimize pig performance. The marginal biological responses to each additional gram of dietary available phosphorus consumed declines as dietary phosphorus intakes approach the pig’s requirement (Table 5). However, the pig’s response to the last increment of dietary phosphorus supplementation still results in a 5-dollar (U.S.) return over the cost of the additional gram of dietary available phosphorus.

The calcium (Ca) needs of high lean pigs are estimated to be 1.5 to 3.0 times that of the available phosphorus needs of pigs. The higher Ca/available P ratios are needed as the pig matures from 10 to 250 pounds body weight.

The needs for other macrominerals (i.e., potassium, magnesium, and sulfur) and trace minerals (i.e., iron, zinc, copper, manganese, iodine, and selenium) in high lean pigs have not been specifically defined.

Amino Acids

The dietary amino acid needs of high lean pigs also are greater than NRC (1988) estimates. For example, a dietary lysine concentration of 1.80% is needed to maximize rate and efficiency of growth in high lean, high health pigs fed corn, soybean meal, and 20% whey diets from 12 to 56 pounds (Table 6). Dietary concentrations of 1.15 and .95% were estimated by NRC (1988) for slower growing, less efficient pigs weighing 11 to 22 and 22 to 44 pounds, respectively.

Table 5. Biologic and economic responses of high lean pigs to incremental increases in dietary available phosphorus (P) intakes.^a

	Dietary available P, %
Criteria	.080	.110	.155	.222	.323	.473
Available P intake
Total, g/pig	118	158	203	274	390	561
Incremental increase, g/pig	0	+40	+45	+71	+116	+171
Marginal change per gram of incremental increase in available P intake^b
Days		-.23	-.11	-.08	-.00	-.00
Feed, lb		-.26	-.60	-.23	-.06	-.03
Muscle, %^c		+.000	+.030	+.003	+.001	+.007
Marginal return per kg of incremental increase in available P intake^d
Total return, $		51	59	31	8	9
P cost, $		1.50	1.50	1.50	1.50	1.50
Return on investment		34/1	39/1	21/1	5/1	6/1
a Adapted from Bertram et al. (1995). Pigs (barrows) self-fed fortified corn and soybean meal diets containing 1 of 6 dietary available P concentrations from 42 to 162 pounds body weight. ^bChange in days, feed, and muscle percentage achieved over 120 pounds of weight gain. ^cChange in muscle assumed to be 50% of that determined by physical dissection after 200 pounds of body weight gain. ^dEconomic values assumed were: 1 day = $.15, 1 pound feed = $.065, 1% carcass muscle = $1.20/pig, 1 kilogram available P = $1.50 (dicalcium phosphate, 18.5%).

Table 6. Dietary amino acid needs of high lean pigs fed from 12 to 56 pounds.^a

	Dietary lysine, %
Criteria	.60	.90	1.20	1.50	1.80
Daily feed, lb	1.67	1.87	1.74	1.79	1.60
Daily gain, lb	.48	.94	1.12	1.21	1.61
Feed/gain	3.58	1.99	1.53	1.46	1.36
^aAdapted from Stahly et al. (1994). Pigs (barrows) self-fed corn and soybean meal diets and exposed to low levels of antigen exposure.

In high lean pigs, the grams of dietary lysine in a corn and soy diet needed per pound of body weight gain is estimated to be 8.3, 8.4, 8.6, 9.1, 9.6, 9.9, 10.1, 10.2, and 10.3 for pigs weighing 10, 40, 70, 100, 130, 160, 190, 220, and 250 pounds, respectively (Stahly et al., 1991; Friesen et al., 1995; Bikker et al., 1994; Williams et al., 1997). These values are derived for diets in which about 85% of the dietary lysine is digested and absorbed by the pig.

The ideal ratios of other dietary amino acids for the high lean pigs have not been specifically determined. The ratios outlined by Fuller et al. (1989), Wang and Fuller (1989), and Chung and Baker (1992) with slight adjustments for stage of growth are assumed to approximate the ideal ratio for essential amino acids for growth of high lean pigs. Based on these data, dietary concentrations of digestible tryptophan, threonine, and methionine–cystine should be a minimum of 17–19, 65–72, and 50–62%, respectively, of the pigs’ dietary need for digestible lysine. The higher ratios are needed as the pig matures.

Providing dietary amino acids in excess of the pigs’ needs results in less energy being available for tissue accretion and more dietary nitrogen being excreted in waste products. In addition, excess dietary amino acid intakes result in lower body weight gains and less efficient utilization of feed, although carcass fat content generally is reduced slightly (Stahly et al., 1991; Stahly et al, 1993; Williams et al., 1997c).

Metabolizable Energy (ME)

Because of the lower energy and higher water content of proteinaceous tissues, the dietary energy needs per pound of body weight gain also are lower for high lean strains of pigs than previous estimates (NRC, 1988). The Mcal of dietary ME (from grain and soybean meal diets) needed per pound of body weight gain in high lean, high health pigs is estimated to be 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, and 5.5 for pigs weighing 10, 40, 70, 100, 130, 160, 190, 220, and 250 pounds. High lean pigs seem to consume sufficient dietary energy voluntarily if their health status, thermal environment, etc., is adequate. Ingestion of ME intakes in high lean pigs above that voluntarily consumed in an ad libitum feeding regimen have not been shown to enhance proteinaceous tissue growth (Table 7). Rather fatty tissue accretion is increased. However, restriction of ME intake below the voluntary consumption level in high lean pigs substantially lowers body weight gain and proteinaceous tissue growth (Campbell and Taverner, 1988) but has minimal effect on carcass fat content. In contrast, similar restriction of ME intakes in moderate lean pigs has minimal impact on proteinaceous tissue growth but reduces carcass fat content and the quantity of feed required per unit of weight gain.

Table 7. Effect of superalimentation (over feeding of energy) on body protein and fat accretion in high lean pigs.^a,b

	Ad	Superalimented, % of ad lib
Criteria	Lib	100	120	140
ME intake, Mcal/day	8.25	8.61	9.64	10.50
Body nutrient accretion
Protein, g/day	183	189	180	172
Fat, g/day	173	203	251	311
Energy, Mcal/day	2.68	2.99	3.40	3.90
^aAdapted from McCracken et al. (1994). ^bPigs (boars only) with a high genetic capacity for muscle growth received a single diet from 40 to 90 kg body weight via: 1) ad libitum consumption, or 2) permanent gastric cannula (5 times daily) at levels equivalent to 100, 120 or 140 % of the ME intake of the ad libitum group.

Antimicrobials

The biologic and economic responses of high lean pigs to feed additives such as antimicrobial agents also differ from that of fatter genetic strains. High lean, high health pigs fed subtherapeutic concentrations of an antimicrobial agent (carbadox) from 14 to 78 pounds deposited more body muscle, less body fat, and required less feed per unit of gain (Table 8). In contrast, ingestion of the agent by low lean, high health pigs resulted in fatter carcasses with minimal changes in feed utilization and muscle tissue growth.

Table 8. Response of high and moderate lean pigs to subtherapeutic concentrations of an antimicrobial agent.^a,b

	Pig	Carbadox, ppm
Criteria	Strain	0-0	55-0	Change
Body growth and feed utilization
Daily feed, lb	High lean	4.90	4.92	+.02
	Low lean	5.09	5.09	+.0
Daily gain, lb	High lean	1.68	1.77	+.09
	Low lean	1.61	1.60	-.01
Feed/gain	High lean	2.92	2.78	-.14
	Low lean	3.16	3.18	-.02
Carcass composition
Backfat, in	High lean	1.08	.96	-.12
	Low lean	1.42	1.56	+.14
Muscle, %^c	High lean	54.4	56.2	+1.8
	Low lean	45.9	45.6	-.3
Fat, %^c	High lean	29.1	27.0	-2.1
	Low lean	37.1	38.5	+1.4
^aAdapted from Stahly et al. (1996). ^bPigs (barrows only) self-fed a single diet containing either 0 or 55 ppm carbadox from 14 to 78 pounds and then pigs in both groups were fed the control diet (0 ppm carbadox) until pigs reached 254 pounds. ^cCarcasses were physically dissected in muscle, fat, bone, and skin components.

Expected Performance of High Lean Pigs

The daily feed intake, body weight gain, and feed/gain ratios observed for high lean pigs reared under good production conditions are reported in Table 9. The daily ME intakes and estimated dietary needs of these pigs for lysine and available phosphorus are reported in Table 10. In instances that production conditions deviate from those reported in Table 9, the optimum dietary regimen will also be altered. For example, chronic exposure of pigs to antigens will lower the pigs’ ability to synthesize proteinaceous tissues as well as lower voluntary feed intake. Because tissue growth is depressed more than feed intake in a chronic health challenge, the pigs’ dietary needs for lysine and phosphorus expressed as grams per day or a percentage of the diet are both lowered. In contrast, cold exposure normally does not alter the pigs’ potential for proteinaceous tissue growth but does increase the pigs’ daily feed or ME intake. Thus, the concentration of nutrients in the diet can be lowered and still provide the necessary intake of nutrients.

Table 9. Performance of high lean pigs.^a

	Pig weight, lb
Criteria	10	40	70	100	130	160	190	220	250
Daily feed, lb	.79	2.25	3.48	4.47	5.48	5.97	6.37	6.92	7.39
Daily gain, lb	.77	1.65	2.04	2.20	2.31	2.20	2.09	2.04	1.98
Feed/gain	1.02	1.36	1.69	2.03	2.37	2.71	3.05	3.39	3.73
^aPerformance of a lean genetic strain of pigs allowed to consume a fortified, corn and soybean meal diet ad libitum. Pigs reared in a thermal neutral climate, allowed adequate space, and experienced a minimum level of chronic antigen exposure. Summary of five studies conducted at Iowa State University from 1993 to 1997.

Table 10. Dietary ME intakes and lysine and available phosphorus needs of high lean pigs.^a

Dietary	Pig weight, lb
Regimen	10	40	70	100	130	160	190	220	250
ME intake, Mcal/day	1.2	3.3	5.1	6.6	8.1	8.8	9.4	10.2	10.9
Lysine, %	1.75	1.35	1.10	.98	.88	.80	.72	.66	.60
Available P, %	.86	.61	.46	.38	.31	.27	.23	.20	.18
^aAssumption: high lean pigs reared under the production conditions outlined in Table 9.

Summary

The high lean pigs require greater amounts of some vitamins, macrominerals, and amino acids per unit of body weight gain and per Mcal of dietary ME than moderate lean pigs. Because a greater proportion of these nutrients is used to fuel muscle growth, the economic return per unit of dietary nutrient consumed also is greater than that for moderate lean pigs. Thus, the economic incentive to accurately define rates at which pigs are expressing key biological processes in a specific situation and then providing the nutrient inputs needed to fuel these levels of process expressions is greater in high versus moderate lean pigs.

LITERATURE CITED

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Stahly, T. S., N. H. Williams, S. G. Swenson, and R. C. Ewan. 1995. Dietary B vitamin needs of high and moderate lean growth pigs fed from 20 to 60 pounds body weight. Iowa State University Swine Research Report. ASL-633. p. 15-18. Ames, Iowa.

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Williams, N. H., T. S. Stahly, and D. R. Zimmerman. 1997a. Effect of chronic immune system activation on the rate, efficiency, and composition of growth, partial efficiency of lysine and energy utilization, and lysine needs of pigs fed from 6 to 27 kg. J. Anim. Sci. 75:2463-2471.

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Williams, N. H., T. S. Stahly, and D. R. Zimmerman. 1997c. Effect of level of immune system activation on the growth and dietary lysine needs of pigs fed from 6 to 112 kg. J. Anim. Sci. 75:2481-2496.