Livestock Production Science, 18 (1988) 141-155 141 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

Joint Effects of Fraterni ty Size, P lane of Nutrit ion and Nurs ing Schedule on Pig Growth from Birth to 20 Weeks of Age

H.L. CHANG, D. GIANOLA, R.A. EASTER, L.H. THOMPSON and S.A. WILLIAMSON

Department of Animal Sciences, University of Illinois, Urbana, IL 61801 (U.S.A.)

(Accepted 13 August 1987)

ABSTRACT

Chang, H.L., Gianola, D., Easter, R.A., Thompson, L.H. and Williamson, S.A., 1988. Joint effects of fraternity size, plane of nutrition and nursing schedule on pig growth from birth to 20 weeks of age. Livest. Prod. ScL, 18: 141-155.

Eighty-nine gilts were assigned to 8 treatments (2 dietsX2 litter sizesX 2 nursing schedules) in a cross-fostering experiment. Diets were a corn-soya bean ration with or without 15% animal fat; litter sizes were 6 or 10 pigs; nursing was conventional or restricted. Interactions on body weight through 20 weeks of age in progeny of the gilts were assessed. Sires of pigs did not differ before weaning but did so thereafter, accounting for 15.3% of the variance in 18-week body weights. Pre-natal maternal effects explained 44.4% (birth weight) to 7.1% (7-week weight) of the vari- ance. Post-natal effects increased through 10 weeks of age, and decreased later. About 31% of the variance of 20-week body weight was accounted for by pre- and post-natal maternal effects. An increase in fraternity size reduced body weight of 10-18-week-old pigs under conventional nursing but not under limiting nursing. Pigs raised in a "constant" nutritional environment grew faster than those reared in a "variable" environment. Diet fed to genetic dam X diet fed to nurse X fraternity size interactions affected body weights at 3, 4, 5, 10 and 12 weeks of age.

INTRODUCTION

G r o w t h ra t e is i m p o r t a n t because f a s t -g rowing pigs require fewer days to r each m a r k e t weight , a n d the pe r iod of p o t e n t i a l d isease exposure is reduced. R a t e of body -we igh t ga in a n d ef f ic iency of feed conve r s ion are pos i t ive ly re- la ted, a l t houg h th i s r e l a t i onsh ip var ies wi th b r eed a n d m a n a g e m e n t ( W a r w i c k a n d Legates , 1979) . R e s e a r c h wi th mice has s u b s t a n t i a t e d the i m p o r t a n c e of m a t e r n a l in f luences on t r a i t s r ecorded before or a t weaning, or a t l a te r s tages in life (e.g., Ru t l edge e t al., 1972 ). Ah l schwede a n d Rob i son (1971) found t h a t 18% of t he v a r i a t i o n in pig body weigh t a t 8 weeks of age was a c c o u n t e d for by p o s t - n a t a l m a t e r n a l effects; a t 20 weeks , the f igure was 10.8%. I tu lya e t al.

0301-6226/88/$03.50 © 1988 Elsevier Science Publishers B.V.

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(1983) suggested that maternal effects are important at weaning and early post-weaning stages, and that additive genetic influences would diminish later.

Studies on maternal influences on growth of pigs have indicated a negative effect of large litters on weaning weight, and on growth from weaning onwards (Robison, 1979). Standal (1973) found that litter size adversely affected the post-weaning performance in pigs born in gilt litters; this effect was not as large in pigs born to multiparous dams. Stevenson and Britt (1981) reported that pigs raised in large fraternities (13-14 pigs per litter) did not grow as fast as those weaned from average-sized litters (8 pigs), although they consumed twice as much creep feed. Vangen (1977) estimated a 6.7 gm day -1 decrease in post-weaning growth rate for each additional pig in the litter.

Some experiments (Thompson and Jensen, 1979; Thompson et al., 1980; Stevenson and Britt, 1981) have not found a consistent effect of nursing schedule on pig growth. However, pigs undergoing periods of limited nursing during late lactation tended to have a higher post-weaning average daily gain than those allowed to suckle ad libitum, and the consumption of creep feed during lactation increased 2- to 3-fold. In general, the total (pre- and post- weaning) body-weight gain of pigs raised under limited nursing was similar to that obtained with conventional nursing.

The availability of nutrients supplied by the dam is critical to the neonate pig, particularly before creep-feed consumption begins. If energy in sow's milk is a limiting factor, this may restrict utilization of other essential nutrients for maximum growth (Pond and Maner, 1974). Feed consumption by lactating sows fed ad libitum may be insufficient to meet needs for milk production as indicated by loss of backfat during lactation (Michel et al., 1980). An influence of energy intake by the dam during lactation on litter performance has been found in several studies ( Seerley et al., 1974; Wahlstrom and Libal, 1976; Boyd et al., 1978; Moser et al., 1978; Nelssen et al., 1985 ). Because of its high caloric density, the energy content of milk might be increased by adding fat to the sow's diet.

The purpose of this experiment was to assess the joint effects of the pre- weaning plane of nutrition, fraternity size and nursing schedule on the growth of pigs from birth to 140 days of age.

MATERIALS AND METHODS

Experimental design

This study started with 99 crossbred gilts, the progeny of dams from a 3- breed rotation (Yorkshire, Duroc and Hampshire) mated to Chester White boars. Gilts were randomly chosen from contemporary females with at least 12 apparently functional nipples and without obvious leg weaknesses.

Gilts were mated at the third post-puberal estrus in 3 farrowing groups; 89

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such gilts farrowed. All gilts were hand-fed to appetite with a conventional corn-soyabean diet until day 109 of pregnancy. Within farrowing groups, each gilt was randomly assigned to one of 8 treatments in a 23 factorial design. Fac- tors were: (1) level of energy from day 109 of gestation through weaning; (2) post-natal fraternity size; (3) piglet nursing schedule. Weaning was at 28 days of age.

Levels of dietary energy were represented by 2 diets. The diets were a con- ventional corn-soya bean diet with or without 15% animal fat. The caloric content of the fat-added diet was 19.8% larger than that of the conventional ration (3911 vs. 3265 ME kcal kg -1) ; both diets had 16% crude protein, and met vitamin and trace mineral requirements. Post-natal fraternity sizes were 6 vs. 10 pigs nursed per litter; these were obtained via reciprocal cross-fostering of pigs in randomly-paired litters farrowing withima 24-hour period. When the 2 gilts in a pair farrowed less than a total of 16 live pigs, foster animals born on the same day were used to standardize litter size, but no records were taken on these. Nursing schedules were conventional (unrestricted) or limited from Day 19 of lactation through weaning. Pigs in the unrestricted group suckled ad libitum. Those under limited nursing were separated from their nurses begin- ning at Day 19 of lactation. Thereafter, nursing was 4 times daily ( 30 minutes each time) from Days 19-22, and 3 times daily (30 minutes each time) from Day 23 through weaning. Creep feed was made available to all piglets from Day 14.

Pigs were weighed weekly from birth until 8 weeks of age and biweekly there- after until 20 weeks of age; pigs born in one of the farrowing groups failed to be weighed at 10 weeks of age. The number of animals with records varied between 881 pigs at birth to 204 pigs at Week 10. Variation in number of rec- ords reflected mortality, reduction of stock done at random following weaning (because of space constraints) or missing records, e.g., body weights at 10 weeks of age.

Statistical analyses

Univariate mixed linear model techniques (Henderson, 1984) were used. Restricted maximum likelihood (REML) via the EM algorithm (Dempster et al., 1977) was used for estimating the necessary variance components. Best linear unbiased estimates of marginal means for "main effects" (averaged across appropriate interactions), and of interaction between levels of "main effects" were obtained solving mixed-model equations, conditionally on the REML es- timates of variances. Tests of testable hypotheses were also obtained using mixed-model methodology. Full details are in Chang (1986).

Birth weight The statistical model first entertained was

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Yiiktm~o = Ai + B i + Ck + Dt + ( CD ) kt +Sm + diikm, + ~ Cs ) am + eiiktm~o (1)

where Ai = fixed effect of the ith farrowing season ( i = 1, 2, 3 ) ; By = fixed effect of the j th barn ( j = l , 2); Ck=fixed effect of the kth diet of dam ( k = l , 2); Dt = fixed effect of t h e / t h sex ( female or male ) of pig ( l = 1, 2 ) ; (CD) kl = fixed effect of the interaction between the kth diet and t h e / t h sex; Sm= effect of the mth sire of pig ( m = 1, 2,...,18), Sm~ (0, a 2 ); dijhmn=effect of the n th genetic dam mated to the mth sire, nested within the kth diet, j th barn and ith farrow- ing season, diihm, ~ (0, a 2 ) ; (Cs) hm = effect of the interaction between the kth diet and mth sire, (Cs) hm ~" (0, a2cs ) ; eijatmno-~ random residual, eijklmn o "~ ( O, ave). Because the ratios 2 2 2 2 aCs/ae were as a s / a e and est imated less than 10 -s, the random variables Sm and (Cs) km were eliminated from the model. Hypotheses were formulated as follows. The marginal mean for the kth diet of dam is

3 2 2 2

#..h....= ~ A / /3+ ~ B j / 2 + C k + ~ Dr /2+ ~. (CD)kJ2 i = 1 j = l / = 1 / = 1

The hypothesis of "no difference between diets" is H:#..k....--#..k,....=O. Simi- larly, the hypothesis of "no interaction between diet and sex of pig" is H:P..kl... -- #..kz'... -- #..k'r ... + #..k' z'... = 0, where #..h~... is a 2-factor marginal mean. Corresponding sums of squares and F-statistics were calculated following Hen- derson (1984).

Body weight at I week, 2 weeks and 18 days of age The model employed first was

Yijklmnopq =Ai +Sj + Ck + Dz + E ~ + (BD)i~ + (BE)j-m + (DE)~m +sn

+dijmno +filmp "4- ( B s ) j n -4- ( S f ) i j lm p -4- ( D s ) l n q- ( D d ) ijlmno

"~ ( E s ) mn "~ ( s f ) ilrnnp "1- (dr) ijhnnop ~-eijklrnnopq

where Ai = fixed effect of the ith farrowing season ( i = 1, 2, 3 ); By = fixed effect of the j th diet fed to the genetic dam (j = 1, 2 ); Ck = fixed effect of the kth sex (female, barrow or male ) of pig (k = 1, 2, 3); Dl = fixed effect of t he / t h diet fed to the nurse ( /=1 , 2); Era=fixed effect of the mth fraterni ty size ( m = 1, 2); sn=effect of the n th sire of pig, s , ~ (0, a 2 ); dijmno=effect of the oth genetic dam mated to the nth sire and nested within the ruth fraterni ty size, j th diet of genetic dam and ith farrowing season, d..~j~,o ~ (0, a 2 ); filmy = effect of the p th nurse nested within the mth fraterni ty s ize , / th diet of nurse in the ith farrowing season, filmp~ (0, a~ ); (BD)jt, (BE)/m, (DE) lm= fixed effects of 2- factor interactions; (Bs) j , , (Bf)ijlmv, (Ds ) t , , (Dd)ijlmno, (Es)mn, (S[)ilmnp,

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(dr) ije~nov= random effects of 2-factor interactions, all IID with appropriate variances, and eijhlmnop q -~ random residual, eijhlmnop q "~ ( O, a2e ).

Random variables with estimated variance such that ^ 2 2 a i / ~ e < 10 -s were eliminated, after which the model became:

Yijkemopq =Ai +Bj +Ck +De +Era + (BD)je + (BE)ira

+ (DE)e~ +dii~o +fiery -beijkemovq (2)

Body weights f rom 3 to 20 weeks of age After eliminating random variables with negligible variance, the model em-

ployed was

Yijkemn& =-Ai +Bj +Ck +De + (BD);e +Sin +diirnn "F'fieo "l-eijklmnop (3)

where A, B, C, d and f, are as in model 2, sm is sire of pig and De is the fixed effect of t h e / t h diet X fraternity size X nursing schedule post-natal t reatment combination assigned to the nurse of the pig ( /= 1, 2,..., 8). The 7 degrees of freedom for post-natal t reatment combinations were partitioned to study sin- gle-factor, 2-factor and 3-factor effects.

RESULTS AND DISCUSSION

All estimates of interaction variance components, e.g., s i re×die t and sire )< fraternity size, were negligible for all traits, suggesting that these random variables can be ignored in models for evaluation of pig growth. This was the course of action followed in this study. REML estimates of variance compo- nents expressed as a percent of total variance, or relative to residual variance are given in Table I. Differences between sires were negligible before weaning but gradually increased thereafter, contributing from 0.5% of the total vari- ance at 4 weeks of age to 15.3% at 18 weeks. Only 18 sires were represented so the estimates are imprecise. For example, the estimate of sire variance at 12 weeks of age was inconsistent with those obtained at 10 and 14 weeks, and this is probably due to sampling. Pre-natal maternal effects contributed from 44.4% (birth weight) to 7.1% (body weight at 7 weeks) of the variance. Post-natal effects increased in importance through 10 weeks of age and decreased there- after, but the trend was not smooth owing to sampling variance. Prior to wean- ing, pre-natal effects tended to be larger than post-natal effects, but this picture changed somewhat at later stages. At 20 weeks of age, about 31% of the vari- ance was still explained jointly by pre- and post-natal maternal effects, the 2 types of influences contributing about equally.

Only "main" effects and interactions of experimental interest are discussed, i.e., effects involving diet, fraternity size and nursing schedule. Diet fed to the genetic dam did not affect any of the body weights measured. The finding that

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TABLE I

Restricted maximum likelihood estimates of the variance between sires (S), dams (D), nurses (N) and residuals (R) for body weights from birth through 20 weeks of age, as a percent of the total variance

Trait 1 % of variance Ratios R (kg 2)

S D N R R/S R/D R/N

BW 0 44.4 - 55.6 > 1012 1.25 0.05 Wl 0 37.9 10.3 51.7 > 10 TM 1.37 5.16 0.15 W2 0 24.3 21.4 54.3 > 1032 2.24 2.55 0.38 D18 0 28.7 16.0 55.3 > 102o 1.92 3.52 0.52 W3 0 25.0 13.3 61.7 > l0 s 2.47 4.62 0.74 W4 0.5 18.4 23.8 57.3 106.00 3.12 2.41 1.06 W5 0.5 24.0 16.9 58.5 107.00 2.43 3.45 1.07 W6 2.9 12.0 24.4 60.7 20.88 5.06 2.49 1.67 W7 3.0 7.1 36.1 53.7 17.85 7.48 1.49 2.32 W8 4.3 10.7 31.3 53.8 12.61 5.04 1.72 3.53 Wl0 4.7 11.4 41.6 42.4 9.11 3.73 1.02 7.65 W12 0 17.3 30.8 51 .9 1410.00 3.00 1.68 14.10 W14 11.1 22.5 18.1 48.3 4.35 2.14 2.66 23.53 W16 13.1 12.3 21.7 52.8 4.01 3.89 2.43 38.18 W18 15.3 15.4 13.5 55.8 3.64 3.61 4.14 55.91 W20 10.6 17.2 13.5 58.7 5.52 2.41 4.36 72.12

'BW=birth weight; D18=body weight at 18 days of age; Wl--W20 are body weights from 1 to 20 weeks of age.

a fa t supp lemen t in the genet ic dam's diet f rom late ges ta t ion t h ro u g h farrow- ing does no t a f fec t body weights of piglets agrees wi th resul ts of o the r workers (Seer ley et al., 1974; Okai e t al., 1977; Seer ley et al., 1978; Coffey et al., 1982). Es t im a t e s of marg ina l means for diets fed to nurses are in Tab le II. Pigs reared by nurses fed a fa t s u p p l e m e n t weighed 0.21 kg, 0.27 kg an d 0.34 kg more at 3, 4 and 5 weeks of age, respect ively , t h a n those rea red by nurses fed a conven- t iona l diet ( P < 0.05, Tab le I I ) . However , d i f ferences be tween diets d iss ipated the rea f t e r . T h e posi t ive effect on ear ly growth of adding fat to the nurse ' s diet could be exp la ined by modi f ied mi lk composi t ion , pa r t i cu la r ly milk lipids, and by an increased mi lk p roduc t i on due to fa t su p p l em en ta t i o n ( B o y d et al., 1978; Coffey et al., 1982) . Lack of s ta t i s t ica l s ignif icance before 3 weeks of age is cons i s t en t wi th o the r s tudies (Cof fey et al., 1982; K ing and Wil l iams, 1984 ).

As shown in Tab le III, pigs r ea red in " sma l l " f ra te rn i t i es were heavier t h a n those rea red in large l i t ters, a l though s ignif icant ly ( P < 0.05 ) so only t h ro u g h 10 weeks of age. S igni f icant d i f ferences r anged f rom 0.19 kg at 1 week of age to 1.64 kg at 10 weeks. At 20 weeks, t he re was still an advan tage of 1.33 kg in body weight for pigs r ea red in " sma l l " f ra tern i t ies . La rge r f r a t e rn i ty sizes lead- ing to l ighter pigs is in ag r eemen t wi th mos t s tudies ( L u s h et al., 1934;

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TABLE II

Best linear unbiased estimates (BLUE's) and standard errors of marginal means (kg) for diet fed to nurse

Trait 1 Diet

Corn-soyabean Corn-soyabean plus 15% fat

Wl 2.55 _+ 0.05 (330) a 2.52 ± 0.05 (321 ) a W2 4.04±0.07 (336) a 4.13±0.07 (316) a D18 4.77±0.11 (173) a 5.11±0.12 (161) a W3 5.11 _+ 0.08 ( 306 ) ~ 5.32 ± 0.08 ( 294 ) b W4 6.04±0.10 (323) a 6.31±0.09 (310) b W5 7.24±0.15 (179) a 7.58±0.15 (171) b W6 8.86±0.21 (176) a 9.10±0.20 (169) a W7 11.45±0.32 (170) a 11.67_+0.32 (163) a W8 13.92±0.55 (165) ~ 13.88±0.53 (160) a Wl0 20.41+1.10 (108) a 20.21+1.15 (96) ~ W12 28.92 ± 1.04 (158) ~ 28.78 ± 1.00 (140) a W14 35.90± 1.49 (163) ~ 35.30_+ 1.44 (158) ~ W16 44.86±2.16 (160) ~ 44.16±2.08 (154) ~ W18 52.16 __+ 2.55 (157) a 51.54 ± 2.45 (152) ~ W20 62.34 ± 2.82 (129) a 61.63 ± 2.75 (128) a

1Wl-W20 are body weights from I to 20 weeks of age; D18 = body weight at 18 days of age. a,bBLUE's with different superscripts differ (P < 0.05 ). Value in parentheses is number of records for each level.

Bywaters, 1937; Menzies-Kitchin, 1937; Smith and Donald, 1937; Winters et al., 1947; Fredeen and Plank, 1963; Standal, 1973; Vangen, 1977; Robison, 1979; Stevenson and Britt, 1981; Van der Steen, 1982, 1983). Similar results have been found in experiments conducted with mice and rats (Wurtmann and Miller, 1976; Epstein, 1978; Hayes and Eisen, 1979; Eisen and Durrant, 1980a, b,c).

Limited nursing depressed growth at all ages considered (P<0.05, Table IV). Differences between pigs in the 2 nursing schedules increased from 0.93 kg at 3 weeks of age to 4.63 kg at 20 weeks of age. Results obtained in other experiments have not been consistent (Smith and Donald, 1939; Fredeen and Plank, 1963; Thompson and Jensen, 1979; Thompson et al., 1980; Stevenson and Britt, 1981 ).

All 2-factor interactions included in Model 2 for body weight at 1 week, 2 weeks and 18 days of age were not significant. When the 7 degrees of freedom for post-natal treatment combinations (Model 3) were partitioned to study joint effects on body weights from 3 to 20 weeks of age, the only significant interaction was between fraternity size and nursing system. As presented in Table V, only body weights at 10, 14, 16 and 18 weeks of age were affected (P<0.05) by this interaction. Under conventional nursing, pigs reared in

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TABLE III

Best l inear unbiased est imates (BLUE ' s ) and s tandard errors of marginal means (kg) for frater- ni ty size

Tra i t 1 Fra te rn i ty size

6 pigs 10 pigs

W l 2.63 +_ 0.05 W2 4.30 +_ 0.07 D18 5.27+_0.11 W3 5.50 -+. 0.09 W4 6.50+0.11 W5 7.70_+ 0.16 W6 9.41 + 0.22 W7 11.99 +- 0.34 W8 14.41 +- 0.56 W l 0 21.13_+1.12 W12 29.26 + 1.05 W14 36.07 +_ 1.49 W16 45.07 +_ 2.16 W18 52.82 +_ 2.55 W20 62.65 _+ 2.85

(237) ~ (238) ~ (126) ~ (219) a (235) ~ (151 i a (154 ,a (152 i a (150 b a (109 b a (161 i a (171 ~a (167 t a (167 i ~ (137 i ~

2 .44+0.05 (414) b 3.87_+0.07 (414) b 4.61+_0.10 (208) b 4.93 +_ 0.07 ( 381 ) b 5.84_+0.08 (398) b 7.13_+0.14 (199) b 8 .55+0.19 (191) b

11.12_+0.30 (181) b 13.40+_0.53 (175) b 19.49+_1.13 (95) b 28.44 +_ 1.00 (137)" 35.14_+ 1.43 (150) a 43.96 +- 2.08 (147) a 51.54+-2.45 (142) a 61.32_+2.71 (120)"

lW1-W20 are body weights from 1 to 20 weeks of age; D18- -body weight at 18 days of age. a'bBLUE's wi th different superscripts differ ( P < 0.05). Value in parentheses is number of records for each level.

"small" fraternities were 3.06 kg, 3.06 kg, 4.64 kg and 4.94 kg heavier at 10, 14, 16 and 18 weeks of age, respectively, than those in "large" fraternities. On the other hand, an increase in fraternity size was not accompanied by a decrease in body weight under limited nursing. It is not clear why this interaction was observed only for body weights at or beyond 10 weeks of age, but not for earlier weights.

Upon partitioning the 7 degrees of freedom for interaction between diet fed to genetic dam and post-natal t reatment ( Model 3 ), it was found that the dam diet × nurse diet (Table VI) and the dam diet X nurse diet × fraternity size in- teractions ( Table VII) were significant for several body weights. The effect on pig weight of adding a fat supplement to the diet of the nurse was positive when the pig was out of a genetic dam that had been fed the same ration. However, the opposite was true when the pig was out of a genetic dam fed the conven- tional diet. The heaviest pigs were those in the Dfx Nf cells through 12 weeks of age (Table VI). This 2-factor interaction can be viewed as a contrast be- tween body weights of pigs in "constant" ( Dc × No, Dr× Nf) and in "changing" (De X Nf, D~X No) environments. If this interaction is real, the results would suggest that variation in nutritional environment in the early life of the pig may retard growth somewhat. Nevertheless, it would appear that body weight

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TABLE IV

Best l inear unbiased es t imates (BLUE ' s ) and s tandard errors of marginal means (kg) for nursing systems

Tra i t 1 Nurs ing system

Convent ional Limited nurs ing nursing

W3 5.68 _+ 0.09 (296) a 4.75 -+ 0.07 (304) b W4 7.05_+0.10 (326) ~ 5.29_+0.09 (307) b W5 8.22_+0.15 (174) a 6 .61±0.15 (176) b W6 9.75_+0.22 (175) a 8.21_+0.19 (170) b W7 12.24_+0.33 (171) ~ 10.87_+0.31 (162) b W8 14.69±0.55 (166) a 13.12±0.53 (59) b W l 0 21.21_+1.13 (96) a 19.41±1.12 (108) b W12 29.84_+ 1.04 (155) a 27.86_+ 1.01 (143) b W14 36.86_+ 1.49 (163) a 34.35_+1.43 (158) b W16 46.07_+ 2.16 (158) ~ 42.95 _+ 2.09 {156) b W18 53.75 _+ 2.54 (156)a 49.96 -+ 2.45 (153) b W20 64.30_+2.84 (130) a 59.67-+2.72 (127) b

'W3 ..... W20 are body weights from 3 to 20 weeks of age. a'bBLUE's with different superscripts differ ( P < 0.05). Value in parentheses for each level.

is number of records

at puberty in females and at market weight in males would not be affected by this interaction.

Estimates of means for diet fed to genetic dam × diet fed to nurse × fraternity size subclasses, and of interaction effects are in Table VII. Body weights at 3,

TABLE V

Best linear unbiased estimates and s tandard errors of joint means (kg) for fraternity size × nursing systems, and of interact ion: body weights from 10 to 20 weeks of age

Tra i t 1 Fra te rn i ty size = 6 pigs Fra te rn i ty size = 10 pigs In terac t ion

CN LN CN LN

W l 0 22.74+1.31 19.51±1.17 19.68___1.19 19.31±1.26 2.86_+1.42" W12 30.89 ___ 1.30 27.63 ± 1.08 28.78 _+ 1.07 28.09 ± 1.14 2.57 -+ 1.67 W14 38.39 -+ 1.82 33.74 ± 1.51 35.33 ___ 1.50 34.94 -+ 1.60 4.26 -+ 1.99" W16 48.89±2.52 42.24_+2.15 44.25±2.15 43.66_+2.27 5.88±2.99* W18 56.22±2.97 49.42_+2,53 51.28_+2.53 50.50_+2.67 6.02-+3.02* W20 66.56_+3.44 58.74±2.85 62.05_+2.82 60.60_+2.99 6 .37±3.87

1W3,..., W20 are body weights from 3 to 20 weeks of age; CN = convent ional nursing; LN =- l imited nursing. Value in parentheses is number of records for each level. *P < 0.05.

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TABLE VI

Best linear unbiased estimates and standard errors of joint means (kg) for diet fed to genetic dams × diet fed to nurses

Trait ~ Do Df Interaction

No Nf Nc Nf

W3 5.31+_0.08 5.05_+0.13 4.91_+0.14 5.59_+0.08 0.94_+0.17" W4 6.26_+0.09 6.08_+0.16 5.82_+0.17 6.54_+0.09 0.90-+0.27* W5 7.54-+0.15 7.47-+0.22 6.94_+0.23 7.70+_0.15 0.83_+0.40* W6 8.96_+0.19 8.94_+0.30 8.76_+0.32 9.26+__0.19 0.52_+0.59 W7 11.78_+0.31 11.44_+0.42 11.11_+0.44 12.90_+0.31 2.13_+0.78" W8 14.25_+0.53 13.58_+0.64 13.59_+0.68 15.18_+0.52 2.26_+1.14" Wl0 20.96 _+ 1.05 18.57 _+ 1.38 19.86 _+ 1.34 21.85 _+ 1.14 4.38_+ 2.14" W12 29.61 _+ 0.98 27.78 _+ 0.24 28.22 _+ 1.35 29.78 _+ 1.00 3.39 _+ 1.57" W14 36.77 _+ 1.43 34.22 + 1.72 35.03 -!-_ 1.84 36.39 _+ 1.41 3.91 -+ 1.95" W16 45.54_+2.12 42.20_+2.40 44.18_+2.52 46.12_+2.04 5.26_+2.63* W18 53.09 _+ 2.51 49.92 _+ 2.82 51.22 + 2.96 53.17 +- 2.40 5.12 -+ 3.17 W20 63.54_+2.79 59.06_+3.33 61.15_+3.31 64.20_+2.66 7.53_+6.74

*w3-w20 are body weights from 3 to 20 weeks of age; D¢-corn-soya bean diet fed to genetic dams; Df= corn-soya bean diet plus 15% fat fed to genetic dams; No-- corn-soya bean diet fed to nurses; Nf= corn-soya bean diet plus 15% fat fed to nurses. *P<0.05.

4, 5, 10 and 12 weeks of age were affected significantly ( P < 0.05) by these 3- factor effects. When comparing pigs in "cons tant" versus "changing" feeding regimes, the differences were 0.81 kg and 0.09 kg at weaning (W4) for "small" and "large" litters, respectively; corresponding differences at 20 weeks of age were 4.36 kg and 3.18 kg, respectively. With in a "cons tant" feeding environ- ment, pigs from dams and nurses fed a fat supplement weighed 0.45 kg and 0.11 kg more at weaning in "small" and "large" litter sizes, respectively, than those from females fed a conventional diet.

CONCLUSION

In general, it has been found tha t maternal influences are important at weaning and at early post-weaning stages (Cox et al., 1959; Young et al., 1965; EI-Oksh et al., 1967; Ahlschwede and Robison, 1971; Rutledge et al., 1972; Jamison et al., 1975; I tulya et al., 1983) and the results of this study agree. Post-natal influences diminished during post-weaning growth, which also agrees with results obtained by several authors (Standal, 1973; Vangen, 1977; Robison, 1979; Stevenson and Britt , 1981; van der Steen, 1982). Some inter- actions indicated by this research suggest tha t there may be pitfalls in char- acterizing maternal environment in terms of a single factor, e.g., fraternity

TABLE VII

Best linear unbiased estimates and standard errors of joint means (kg) for diet fed to genetic damX diet fed to nurse >< fraternity size subclasses and of interaction effects

Trai t 1 D~ Df Interaction

Nc Nf No Nf

6 pigs 10 pigs 6 pigs 10 pigs 6 pigs 10 pigs 6 pigs 10 pigs

W3 5.63_+0.12 4.98_+0.09 5.26_+0.20 4.85_+0.16 5.02_+0.24 4.80_+0.15 6.08_+0.13 5.11_+0.09 0.99+0.44* W4 6.68_+0.15 5.83_+0.11 6.24_+0.24 5.91_+0.21 5.95_+0.29 5.69_+0.18 7.13_+0.14 5.94_+0.11 1.45_+0.53" W5 7.93_+0.21 7.16_+0.17 7.59_+0.32 7.35_+0.29 6.94_+0.37 6.93_+0.25 8.34_+0.20 7.06_+0.19 1.80_+0.64" W6 9.36_+0.25 8.56_+0.23 9.38_+0.41 8.51_+0.39 8.88_+0.54 8.64_+0.31 10.02_+0.24 8.50_+0.23 1.21_+0.97 W7 12.14_+0.37 11.42_+0.35 11.86_+0.55 11.02_+0.52 11.04_+0.70 11.19-+0.43 12.92_+0.35 10.88_+0.36 2.07_+1.39 W8 14.60_+0.57 13.90_+0.59 14.14_+0.78 13.03_+0.74 13.56_+0.95 13.62_+0.69 15.33_+0.57 13.04-+0.57 1.94_+1.84 Wl0 20.98 _+ 1.11 19.00 -+ 1.19 18.15 -+ 1.67 17.38 -+ 1.71 19.92 ___ 1.73 19.80 _+ 1.73 23.84 ± 1.26 19.80 -+ 1.23 5.13 -+ 2.61" W12 30.06 ± 1.05 29.17 _+ 1.13 28.75 -+ 1.57 26.81 _+ 1.48 26.64 _+ 1.90 29.80 -+ 1.41 31.60 -+ 1.15 27.96 -+ 1.09 5.75 ± 2.90* W14 37.02 _+ 1.54 36.52 _+ 1.58 34.86 _+ 2.10 33.59 _+ 2.03 34.33 _+ 2.55 35.72 _+ 1.89 38.06 ± 1.54 34.71 _+ 1.53 3.97 _+ 3.74 W16 45.26 _+ 2.26 45.83 _+ 2.25 43.19 _+ 2.81 41.21 _+ 2.74 43.25 _+ 3.30 45.10 _+ 2.60 48.56 _+ 2.19 43.69 _+ 2.16 4.17 _+ 4.01 W18 52.93 _+ 2.67 53.25 _+ 2.65 52.14 _+ 3.31 47.69 _+ 3.22 50.28 -+ 3.86 52.19 ± 3.06 55.92 _+ 2.58 50.42 ± 2.55 2.64 _+ 4.74 W20 63.73 _+ 2.99 63.35 _+ 3.01 60.99 _+ 4.37 57.13 _+ 3.54 59.95 _+ 4.27 62.34 _+ 3.56 65.92 _+ 2.90 62.48 -+ 2.84 2.35 -+ 5.24

lW3 ..... W20 are body weights from 3 to 20 weeks of age; De--corn-soyabean diet fed to genetic dams; Df--corn-soyabean diet plus 15% fat fed to genetic dams; Nc = corn-soyabean diet fed to nurses; Nf--corn-soyabean diet plus 15% fat fed to nurses. *P < 0.05.

152

size. For example, the effect of litter size on growth depended on the nursing size. For example, the effect of litter size on growth depended on the nursing schedule. Also, changes in nutritional environment of the dam from pre-natal to post-natal stages had an impact on growth of piglets. It would appear that a broader conceptual framework is needed to understand the impact of maternal environment on growth and, perhaps, on reproduction of pigs. On the other hand, the study revealed that interactions between "main" factors (e.g., diet, fraternity size) and random variables (e.g., sires) are negligible. This should be considered when developing pig evaluation models.

ACKNOWLEDGEMENTS

This research was supported by the Illinois Agricultural Experiment Station and by the Illinois Pork Producers Association. The authors wish to thank H. Cook, R.L. Brewer, J.S. Heffernan, C.D. Alexander and R.C. Keever for the excellent technical support provided during the course of this experiment.

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RESUME

Chang, H.L., Gianola, D., Easter, R.A., Thompson, L.H. et Williamson, S.A., 1988. Effets de la taiUe de la pottle, du plan d'alimentation et du type d'allaitement sur la croissance des porcs entre la naissance et 20 semaines d'~ge. Livest. Prod. Sci., 18:141-155 (en anglais).

Quatre-vingt-neuf truies primipares ont ~t~ r~parties entre 8 traitements (2 r~gimes x 2 tailles de port~ X 2 types d'allaitement) dans une expdrience basde sur r~change de porcelets. Les r~gimes consistaient en un aliment ~ base de ma'is et de tourteau de soja avec ou sans 15% de graisse animale; les portdes comportaient 6 ou 10 porcelets; rallaitement dtait classique ou limit& Les interactions sur le poids vif des porcs issus de ces truies jusqu'& 20 semaines d'~ge ont dtd calculdes. Le p~re des porcelets n'exer~ait pas d'influence jusqu'au sevrage, mais intervenait pour 15.3% dans la variance du poids ~ 18 semaines. Les effets matemels pr~nataux expliquaient de 44.4% (poids ~ la naissance) ~ 7.1% (poids ~ 7 semaines) de la variance. Les effete postnataux augmentaient jusqu'~ 10 semaines d'~ge, et ddcroissaient par la suite. Environ 31% de la variance du poids ~ 20 semaines ~tait due aux effets maternels pr~ et postnataux. Une augmentation de la taille de la pottle diminuait le poids vif des porcelets de 10 ~ 18 semaines dans le cas d'un allaite- ment classique, mais pas dans celui dun allaitement rationn& Les porcs ~lev~s dans un environne- ment nutritionnel "constant" avaient une croissance plus rapids que ceux qui ~taient ~lev~s dans un environnement "variable". Les interactions r~gime de la mbre g~n~tique X rdgime de la m~re nourrici~re × taille de portde affectaient le poids vif ~ 3, 4, 5, 10 et 12 semaines d'~ge.

KURZFASSUNG

Chang, H.L., Gianola, D., Easter, R.A., Thompson, L.H. und Williamson, S.A., 1988. Gemeinsame Einfltisse der Wurfgr~ii~e, des Erniihrungsniveaus und des Siiugeplanes auf das Wachstum von Schweinen bis zum Alter von 20 Wochen. Livest. Prod. Sci., 18:141-155 (auf englisch).

Neun-und-achtzig Jungsauen wurden in einem "cross fostering"-Experiment 8 Behandlungen zugeordnet (2 Futterrationen X 2 Wurfgr6flen X 2 Siiugepliine). Die futterrationen waren Mais-Soja-Rationen mit oder ohne 15% tierischem Fett; die Wurfgr~f~en betrugen 6 oder 10 Ferkel; die Stiugepliine warsn normal oder restringiert. Die Interaktionen auf das K~rpergewicht bis zu 20 Wochen Alter wurden bei den Nachkommen ermittelt. Die V~iter der Ferkel batten keinen Einflul~ auf das Wachstum vor dem Absetzen, erkliirten abet 15.3% der Varianz des 18-

155

Wochengewichtes der Nachkommen. Prenatale maternale Effekte erkl~ten 44.4% (Geburtsgew- icht) bis 7.1% (7-Wochen-Gewicht) der Varianz. Postnatale Effekte stiegen bis zu einem Alter von 10 Wochen und fielen danach wieder ab. Etwa 31% der Varianz des 20-Wochen-Gewichtes wurde dutch pre- und postnatale maternale Effekte bestimmt. Steigende Wurfgr6£e senkte das Gewicht von 10-18 Wochen alten Schweinen bei konventionellem, aber nicht bei restringiertem S~iugeplan. Unter einem "konstanten" Ern~ihrungsniveau gehaltene Schweine wuchsen schneller als unter "variablem" Niveau gehaltene. Die Interaktion zwischen Ration der genetischen Mutter X Ration der Amme X WurfgrSl~e beeinflui~te die K~irpergewichte der Nachkommen bei 3, 4, 5, 10 und 12 Wochen Alter.