Livestock Science 136 (2011) Contents lists available at ScienceDirect. Livestock Science. journal homepage:

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1 Livestock Science 136 (2011) Contents lists available at ScienceDirect Livestock Science journal homepage: The performance response of pigs of different wean weights to high or low input dietary regimes between weaning and 20 weeks of age E. Magowan a,, M.E.E. Ball a,b, K.J. McCracken b, V.E. Beattie c, R. Bradford e, M.J. Robinson d, M. Scott c, F.J. Gordon d, C.S. Mayne a,b a Agri-Food and Biosciences Institute, Large Park, Hillsborough, Co. Down, Northern Ireland BT26 6DR, United Kingdom b The Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX, United Kingdom c Devenish Nutrition Ltd., 96 Duncrue Street, Belfast BT3 9AR, United Kingdom d John Thompson & Sons Ltd., York Road, Belfast BT15 3GW, United Kingdom e Preferred Capital Management, 96 Duncrue Street, Belfast BT3 9AR, United Kingdom article info abstract Article history: Received 21 June 2010 Received in revised form 13 September 2010 Accepted 16 September 2010 Keywords: Pigs Starter diets Finishing pig diets Wean weight Performance In a factorial design, this study aimed to compare the lifetime performance of light (average of 7.1 kg), medium (average of 8.9 kg) or heavy (average of 10.4 kg) wean weight pigs when offered either a high (12 kg/pig) or low (6 kg/pig) allowance of starter diets post weaning and either a normal (DE 13.5 MJ/kg, total lysine 9.5 g/kg) or special (DE 14.5 MJ/kg, and total lysine 11 g/kg) finishing diet from 11 weeks of age. Over six time replicates, 720 pigs (Landrace Large White) were randomly allocated at weaning (28±2 days of age), into groups of 20 which were balanced for sex. These groups were split into two groups of ten at 10 weeks of age (transferred to finishing accommodation). The 20-week weight (88.9 kg), ADG (702 g/day) and ADFI (1841 g/day) between wean and 20 weeks of age was greater for heavy weight pigs (Pb0.001) than for light weight pigs (82.2 kg, 692 and 1715 g/day respectively). However, on a per kg of body weight basis the feed intake/kg (Pb0.01, 39 g/day/kg) and growth rate/kg (Pb0.001, 14.8 g/day/kg) of light weight pigs was greater than that of heavy weight pigs (37.4 and 14.4 g/day/kg respectively). A high allowance of starter diets increased 10-week weight (Pb0.01), ADG (Pb0.01) and reduced ADFI (Pb0.05) and FCR (Pb0.001) between weaning and 10 weeks of age compared with that of pigs offered a low allowance. There were significant interactions between starter diet allowance and finishing diet on finishing pig performance. The 20-week weight and ADG (11 to 20 weeks) of pigs offered a high allowance of starter diets increased (Pb0.01 and b0.05 respectively) when they were offered a special finishing diet compared with a normal finishing diet. However, that of pigs offered a low allowance of starter diets was lowered when they were offered a special finishing diet compared with a normal finishing diet. On the other hand, the ADFI of pigs offered a high allowance of starter diets was similar whether they were offered a normal (1977 g/day) or special (1976 g/day) finishing diet, whereas those offered a low allowance of starter diets had an increased ADFI (Pb 0.01, 2091 g/day) when offered a normal finishing diet compared with a special finishing diet (1903 g/day). In conclusion, when the nutrient density of the diet changed, in particular towards lower supplies, pig weight and growth rate were poorer. In addition light weight pigs at weaning were found to convert feed as efficiently as heavy weight pigs throughout their lifetime. Furthermore, their lifetime growth rate and feed intake on a per kg of body weight basis was higher than that of heavy pigs Elsevier B.V. All rights reserved. Corresponding author. Tel.: ; fax: address: elizabeth.magowan@afbini.gov.uk (E. Magowan) /$ see front matter 2010 Elsevier B.V. All rights reserved. doi: /j.livsci

2 E. Magowan et al. / Livestock Science 136 (2011) Introduction It is largely accepted that the variation in weight between pigs is the main contributing factor to the variable growth rate observed, with small pigs growing slower than large pigs (Magowan et al., 2007; Klindt, 2003; Mahan, 1993). Allen et al. (2010) noted that the coefficient of variation for pig wean weight reduced as pig birth weight increased. An increase in pig birth weight and more uniform birth weights within a litter appears to be the strongest influencing factors in reducing variation in wean weight and subsequent growth rate variation. However, influencing these factors is difficult as many sow factors contribute to the growth rate of unborn pigs, for example the position of the foetus within the uterus (Wise et al., 1997; Vallet and Freking, 2007) and the ratio of primary to secondary muscle fibres within the piglet (Dwyer et al., 1994). Therefore, the majority of research has focused on reducing the variation in weight after birth, especially post weaning. Using 6000 pigs weaned at 21 days of age, Mahan (1995) noted that 25% weighed more than 6.9 kg whereas 25% weighed less than 5.1 kg. Using the data set reported by Allen et al. (2010) which used the wean weights of 13,158 pigs, weaned at 28 days of age and reared by 1351 sows it was found that 25% of the pigs had a wean weight over 10 kg whereas 20% had a wean weight under 7.5 kg with 4% of these pigs weighing under 6 kg. This data highlights the vast range of wean weights from commercial herds weaning at 4 weeks of age. Research suggests that smaller pigs have a less developed digestive system and lower body fat content at birth on an absolute basis compared with larger pigs (Mahan, 1993; Morise et al., 2009) although by weaning Morise et al. (2009) noted that their body fat content on a fractional basis was similar. However, as such, some producers offer light weight pigs at weaning higher allowances of starter diets to support and even boost their growth rate. Previous research, attempting to reduce the variable weight and growth rate of pigs, has investigated the effects of offering high or low planes of nutrition but many studies only report the effect on the average weight of the group of pigs and do not identify the effects of treatment on the different weights of pig (e.g. Magowan et al., submitted for publication; Dritz et al., 1996; Chiba, 1995). The limited research that has focussed on the effects of different diets on different weights of pigs has used pigs which were weaned at 3 weeks of age (e.g. Mahan, 1993; Mahan et al., 1998) and therefore were significantly lighter and less developed than the typical weights achieved when weaning at 4 weeks of age. Although O'Connell et al. (2005) found no effect, Magowan et al. (2009) identified that uniformly grouped pigs at weaning had a reduced variable weight at 15 and 20 weeks of age compared with pigs in mixed weight groups. The current study continued this research by investigating the effect of offering these uniformly grouped pigs which represented, light, medium and heavy weight pigs at weaning, a high or low input dietary regime between weaning and 20 weeks of age. 2. Materials and methods 2.1. Herd details The experimental trial was conducted at AFBI, Hillsborough which has operated as a closed, specific pathogen free unit since Gilts are vaccinated for Parvo Virus and Erysipelas. The pigs were vaccinated for Mycoplasma hyopneumoniae at weaning. At the time of the trial, Porcine Circovirus 2 (PCV2) was identified at high levels in some pigs and it was suspected that Post weaning Multi-systemic Wasting Syndrome (PMWS) was apparent at a low level (Total mortality=6%) in the finishing pigs of the herd. Zinc Oxide and Tylan (Elanco) were included in all diets Pre weaning management Within the first 5 h after birth the piglets received 2 ml of an iron supplement, their tails were docked and their teeth were clipped. Cross-fostering of piglets between litters also occurred within the first 24 h after birth to balance the number of piglets on each sow. Within cross-fostering, the large pigs were removed from their dam and placed on a foster dam hence smaller pigs remained with their dam. Sows were offered 2.5 kg of a lactation diet on the day of farrowing and their allowance of lactation diet increased by 0.5 kg daily until they consumed 10 kg per day which they were offered daily to weaning. The piglets were tagged at 21±2 days of age and received creep feed (DE 15.8 MJ/kg, CP 20%, and lysine 1.6%; Devenish Nutrition Ltd, Belfast) ad libitum from 18±2 days of age. The creep feed was offered on the floor of the heated forward creep area, and was the same as the starter 1 diet used in the trial (Table 1) Housing At weaning the pigs were transferred to a growing (stage 1/stage 2 combined) accommodation (0.38 m 2 /pig) with plastic slatted floors. Temperature was 28 C on the first day of treatment, and was reduced by 0.5 C/day to a minimum of 18 C. In the growing accommodation the pigs were offered feed via a dry multi space feeder (Etra Feeders, Northern Ireland). Two feeders placed along the front of the pen, 0.5 m apart were used per pen (20 pigs). At 10 weeks of age the pigs were transferred to a finishing accommodation (0.61 m 2 /pig) with a fully slatted concrete flooring where they remained until slaughter (105 kg). In the finishing accommodation the pigs were offered feed via a wet and dry single space shelf feeder (Verba, Verbakel, The Netherlands). One feeder was used per pen i.e. per 10 pigs. During the trial, all pigs were offered water from bowl drinkers (10 pigs per drinker). They were exposed to natural lighting through windows and artificial lighting (6250 lux), for 16 h per day Experimental design The experiment was designed as a 3 (light, medium, heavy wean weight) 2 (low or high starter diet allowance) 2 (normal or special finishing diet) factorial. The allocation of dietary treatments in the finishing period was balanced across the dietary treatments from the growing period so that carryover effects could be tested for. Pigs were on experiment from weaning to 20 weeks of age. Table 1 reports the composition of the diets used.

3 234 E. Magowan et al. / Livestock Science 136 (2011) Table 1 The ingredients and composition of the diets used from weaning to finish. Diet Starter 1 Starter 2 Grower Normal finisher 2.5. Treatments during the growing and finishing period Special finisher Ingredient (g/kg) Wheat Barley Maize Cooked cereal Soya (Toasted) (Toasted) Rice protein Sugar Whey Molaferm Vegetable oil blend Soya oil Limestone Mono DCP Salt Lysine Methionine Devicare (mins and vits) Emulsifier Lignosulphate binder Chemical analysis as formulated Dry matter (g/kg) Digestible energy (MJ/kg) Crude protein (g/kg) Oil A (g/kg) Fibre (g/kg) Ash (g/kg) Total lysine (g/kg) The diets were commercially manufactured by Devenish Nutrition Ltd (Belfast) (Starter diets 1 and 2) and John Thompson and Sons Ltd (Grower, Normal and Special finisher). The exact amount of each ingredient cannot therefore be disclosed, however a tick represents the presence of the raw material in the diet. Over six time periods (replicates) a total of 720 pigs (1/4 Landrace 3/4 Large White) were weaned at 28±2 days of age and randomly allocated into groups of 20 according to their weight and sex (groups were balanced for sex). Within each replication two groups of light weight pigs (average weight of 7.1 kg), two groups of medium weight pigs (average weight of 8.9 kg) and two groups of heavy weight pigs (average weight of 10.4 kg) were formed. Groups of pigs were offered either a low or high allowance of starter diets post weaning. Pigs offered a low allowance of starter diets were offered 2 kg per pig of starter diet 1 followed by 4 kg/pig of starter diet 2. Pigs offered a high allowance of starter diets were offered 4 kg per pig of starter diet 1 and 8 kg per pig of starter diet 2. In practice, allowances were offered on a pen basis, for example each pen on a high allowance was offered 80 kg of starter 1 diet followed by 160 kg of starter 2 diet. All diets were offered ad libitum and when pens of pigs had consumed their allowances, they were offered the same grower diet (Table 1) to 11 weeks of age. At 10 weeks of age (70±2 days of age) pigs were transferred to finishing accommodation. At this stage, each group of 20 pigs was split to form two groups (balanced for weight and sex) of 10 pigs. The original assignment of light, medium or heavy remained with the group. From 11 weeks of age pens of pigs were randomly allocated to receive either a special or normal finishing diet so that diet was balanced across previous dietary regime Measurements The pigs were individually weighed and pen feed intakes were recorded at wean 7, 10, 11, 15 and 20 weeks of age. Average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR) were subsequently calculated. In order to standardise comparisons between the light, medium and heavy weight pigs, feed intake (FI/kg) and growth rate per kg of body weight (GR/kg) were also calculated. For example, if, between weaning and 10 weeks of age the feed intake and growth rate of pigs was 700 and 480 g/day respectively and the weight of pigs at weaning was 9 kg and their average weight at 10 weeks of age was 30 kg, then the FI/kg and GR/kg between weaning and 10 weeks of age was 700/(9+30/2) and 480/(9+30/ 2) respectively Statistical analysis Data were analysed on a pen mean basis by Analysis of Variance (ANOVA) using Genstat version 10.1 statistics package (Genstat 10.1, Lawes Agricultural Trust, Rothamsted Experimental Station). Data were analysed according to the design (wean weight starter diet allowance finishing diet). All statistical analyses were conducted at a significance level of 5%. No covariates were applied. 3. Results 3.1. Post weaning performance The weight and average daily gain of heavy, medium and light weight pigs differed significantly at wean, 7 and 10 weeks of age (Tables 2 and 3). The ADFI and ADG of light weight pigs were generally lower than that of heavy weight pigs. However, on a fractional basis, FI/kg and GR/kg of light weight pigs were higher than that of heavy weight pigs (Pb0.001) (Table 3). A high allowance of starter diets was found to increase the 10-week weight (Pb0.01) and ADG of pigs (Pb0.01) and reduce ADFI (Pb0.05) and FCR (Pb0.001) between weaning and 10 weeks of age compared with pigs offered a low allowance of starter diets (Table 3). Although there were no significant interactions, it was noted that the effects of high starter diet allowance on growth rate were most obvious for heavy weight pigs whereas the effects on feed intake were most obvious for light weight pigs (Table 3) Finishing pig performance The weight of heavy and medium weight pigs was similar at 20 weeks of age but greater (Pb0.001) than that of light weight pigs (Table 2). When the pigs were offered a high

4 E. Magowan et al. / Livestock Science 136 (2011) Table 2 The effect of wean weight and starter diet allowance on pig weight (kg) between weaning and 20 weeks of age. Low allowance High allowance Effect of starter diet allowance Effect of wean weight Light Medium Heavy Light Medium Heavy SEM P value SEM P value Wean NS 0.05 b NS 0.15 b b b b b NS 0.74 b0.001 allowance of starter diets post weaning their 15 week weight was significantly greater (55.2 kg, Pb0.05) than pigs offered a low allowance (53.6 kg). Finishing diet had no significant (PN0.05) effect on the 15 or 20 week weight of the pigs. There were significant interactions between starter diet allowance and finishing diet on the 20-week weight (Pb0.01, SEM 0.86) and ADG (between 11 and 20 weeks) (Pb0.05) of pigs. Twenty-week weight and ADG (11 to 20 weeks) of the pigs offered a high allowance of starter diets post weaning increased when they were offered a special finishing diet (87.8 kg, 864 g/day) compared with when they were offered a normal finishing diet (85.7 kg, 821 g/day) whereas that of those offered a low allowance of starter diets was lower when they were offered a special finishing diet (84.7 kg, 847 g/day) compared with when they were offered a normal finishing diet (87.2 kg, 862 g/day). There were also significant interactions between starter diet allowance and finishing diet on the ADFI (Pb0.01) and FCR (Pb0.01) of the pigs between 11 and 20 weeks of age (Table 4). The pattern of the interactions on ADFI and FCR differed from those described above. Pigs that were offered a high allowance of starter diets had similar ADFI's whether they were offered a normal (1977 g/day) or special (1976 g/day) finishing diet, whereas those offered a low allowance of starter diets had an increased ADFI (2091 g/day) when they were offered a normal finishing diet compared with aspecialfinishing diet (1903 g/day). On the other hand, the FCR of pigs that were offered a high allowance of starter diets was improved to a greater extent by offering a special finishing (2.30) instead of a normal finishing diet (2.51) compared with that of pigs offered a low allowance of starter diets post weaning (2.35 and 2.45 respectively). There were no significant interactions on FI/kg between 11 and 20 weeks of age. FI/kg was highest (Pb0.001) for light weight pigs (35.5 g/day/kg) and lowest for heavy weight pigs (32.0 g/day/kg) between 11 and 20 weeks of age (Table 4). There was a significant interaction (Pb0.05) between starter diet allowance and the wean weight of pigs on the ADG and GR/kg of pigs between 11 and 20 weeks of age (Table 4). The ADG and GR/kg between 11 and 20 weeks of age of heavy weight pigs was lower (825 g/day, 13.2 g/day/kg) when they were offered a high allowance of starter diets compared with a low allowance (873 g/day, 14.1 g/day/kg). In contrast, the ADG of light weight pigs increased numerically (843 g/day) when they were offered a high allowance compared Table 3 The effect of wean weight and starter diet allowance on post weaning pig performance. Low allowance High allowance Effect of starter diet allowance Effect of wean weight Light Medium Heavy Light Medium Heavy SEM P value SEM P value ADG (g/day) Wean NS 6.8 b b b0.001 Wean b b0.001 ADFI (g/day) Wean b b NS 9.7 b0.001 Wean b b0.001 FCR Wean b b b b0.05 Wean b b0.001 FI/kg (g/day/kg) Wean b b b0.001 Wean b b0.001 GR/kg (g/day/kg) Wean NS 0.43 b NS 0.32 b0.001 Wean b b0.001

5 236 E. Magowan et al. / Livestock Science 136 (2011) Table 4 Effect of wean weight, starter diet allowance and finishing diet on finishing pig performance (11 20 weeks of age). Effect of finishing diet Effect of wean weight Low allowance High allowance Starter diet allowance Normal Special Normal Special finishing diet interaction L M H L M H L M H L M H SEM P SEM P SEM P ADG a (g/day) b b NS ADFI (g/day) b NS 19.2 b0.001 FCR b NS b0.001 FI/kg b (g/day/kg) NS 0.34 b b0.001 GR/kg b,a (g/day/kg) NS 0.13 b b0.05 L: Light, M: Medium, and H: Heavy. Starter diet allowance wean weight interaction: ADG Pb0.05, SEM 14.5; and GR/kg P b0.05, SEM Effect of starter diet allowance: FI/kg Pb0.05, SEM 0.28; and GR/kg Pb0.01, SEM a b with a low allowance (816 g/day) although GR/kg was similar (14.7 and 14.8 g/day/kg respectively). In addition, although not significant, the 20 week weight of light weight pigs was 2.7 kg heavier when they were offered a high allowance of starter diets compared with a low allowance. Overall from weaning to 20 weeks of age the ADG and ADFI of medium and heavy weight pigs was similar but that of light weight pigs was significantly lower (both Pb0.001) (Table 5). However, FI/kg and GR/kg between weaning and 20 weeks of age were significantly higher for light weight pigs than for medium or heavy weight pigs (Table 5). There was a significant interaction (Pb0.01) between starter diet allowance and finishing diet on ADG between weaning and 20 weeks of age, which followed a similar pattern to that described above for 20- week weight and ADG between 11 and 20 weeks of age (Table 6). Pigs that were offered a special finishing diet had a lower ADFI (Pb0.001) and improved FCR (Pb0.001) between weaning and 20 weeks of age. Those that were offered a high allowance of starter diets post weaning also had an improved FCR between weaning and 20 weeks of age (Pb0.05) (Table 6). There were no significant effects on GR/kg between weaning and 20 weeks of age but there was a significant interaction (Pb0.01) between starter diet allowance and finishing diet on FI/kg (Table 6). FI/kg was similar when pigs were offered a low allowance of starter diets post weaning and either a normal or special finishing diet, but when pigs were offered a high allowance of starter diets post weaning, FI/kg was lower when they were offered a special finishing diet compared with a normal finishing diet (Table 6). 4. Discussion In agreement with previous studies, offering pigs a high allowance of starter diets i.e. nutrient dense diets for a longer period of time, reduced feed intake but improved pig growth rate and feed conversion efficiency post weaning compared with pigs offered a low allowance of starter diets (Mahan, 1993; Chiba, 1995; Dritz et al., 1996). The high allowance of starter diets provided pigs with the same density of nutrients in a lower volume of feed than the low allowance. It is likely that this was the main reason why feed intake was reduced although further work would be required to understand why feed intake was reduced over the entire post weaning period since all pigs were offered the same grower diet for the latter 3 weeks of the post weaning period. Although there was no significant interaction, it was apparent that pigs with different weaning weights responded differently to the levels of starter diets offered. In agreement with Lawlor et al. (2002), the effects of the high allowance of starter diets on growth rate were most Table 5 Effect of wean weight on pig performance from weaning to 20 weeks of age. Light Medium Heavy SEM P value ADG (g/day) 692 a 709 b 702 a,b 6.8 b0.001 ADFI (g/day) 1715 a 1797 b 1841 b 19.8 b0.001 FCR NS FI/kg (g/day/kg) 39.0 b 37.4 a 37.4 a 0.37 b0.01 GR/kg (g/day/kg) 14.8 c 14.6 b 14.4 a b0.001 Numbers with the same superscripts and not significantly different (PN0.05).

6 E. Magowan et al. / Livestock Science 136 (2011) Table 6 Effect of starter diet allowance and finishing diet on pig performance from weaning to 20 weeks of age. Low allowance High allowance Starter diet allowance finishing diet interaction Effect of starter diet allowance Effect of finishing diet Normal Special Normal Special SEM P value SEM P value P value ADG (g/day) 701 a,b 680 a 687 a,b 709 b 7.89 b NS NS ADFI (g/day) NS 16.2 NS b0.001 FCR b0.05 b0.001 FI/kg (g/day/kg) 38.4 b 38 b 39.1 b 36.2 a 0.42 b NS b0.001 GR/kg (g/day/kg) NS NS NS SEM for effects of starter diet allowance and finishing diet is the same. Numbers with the same superscripts and not significantly different (PN0.05). marked for heavy weight pigs. In addition, in the current study the effects on feed intake were most marked for light weight pigs. Pluske et al. (2003) suggested that the development of the gastrointestinal tract of light weight pigs at weaning might proceed differently to that of heavy weight pigs. This study, and that of Lawlor et al. (2002), indicates that light weight pigs also respond differently to dietary regimes post weaning which vary in nutrient density compared to heavy weight pigs. It appears that light weight pigs respond to the higher intake of energy and lysine provided from the high allowance of starter diets, by reducing their feed intake but improving their feed conversion ratio which equates to them having similar growth rate when offered either a low or high allowance. The total digestible energy and lysine intake between weaning and 10 weeks of age of light weight pigs were similar when they were offered either the high (396 MJ, 357 g) or low (402 MJ, 363 g) starter diet allowance. It could be suggested that light weight pigs ate to energy requirements for maintenance and growth and since the nutrients required for these functions could be derived from a lesser amount of feed when they were offered the high allowance, feed intake was reduced. Weatherup et al. (2002) demonstrated that the voluntary feed intake of individually housed pigs reduced when the energy content of the diet increased. However, in a group situation, Weatherup et al. (2002) did not find the same effect but found that voluntary feed intake was similar across a range of diets with varying energy density and pigs responded to the higher energy density diets by improving their growth rate. The above hypothesis that light weight pigs ate to energy requirements is therefore improbable and it is likely that social effects also played a role since these pigs were in groups of 20 and therefore competition for resources i.e. feed was a key factor which would have influenced feed intake (Nyachoti et al., 2004). It may be possible that light weight pigs were able to attain sufficient energy for maintenance and growth from a lesser amount of feed when offered the high allowance of starter diets and therefore were not prepared to engage in competition to attain extra feed. When the data for the light, medium and heavy weight pigs was considered on a per kg of body weight basis it was found that light weight pigs actually grew and ate more than heavy weight pigs. Post weaning, light weight pigs were also found to be 3% more efficient at converting feed to gain than heavy weight pigs. Pluske et al. (2003) found that the stomach and small intestine of pigs weighing 5.6 kg when weaned at 28 days of age was 17.2 g and 59 g lighter, respectively, than that of pigs weighing 9.1 kg at the same weaning age. However, the weight of the stomach and small intestine of light weight pigs was larger than that of heavy weight pigs when data were standardised as a percentage of live weight. Furthermore, Pluske et al. (2003) found no significant effect of weaning weight on the villous height or crypt depth in the small intestine or the secretion of lactase or sucrase and although villous height decreased and crypt depth increased post weaning, due to the weaning process (Pluske et al., 1997), there was no effect of weaning weight on the degree of change. Light weight pigs at weaning therefore perform better, on a per kg of weight basis, than heavy weight pigs due to the fact that, relative to live weight, the size and capability of their gastrointestinal tract is similar to that of heavy weight pigs and the growth rate, per kg of body weight, advantage stems from the fact that they can eat more, per kg of body weight and convert better than heavy weight pigs. Whilst some studies have found no improvements (Lawlor et al., 2002; Wolter et al., 2002; Chiba, 1995), others have found that the lifetime performance of pigs is improved when they are offered a higher level of nutrient dense diets or diets with more complexity post weaning which is in agreement with some of the results of this study (Mahan et al., 1998; Dritz et al., 1996). However there are few which have continued to manipulate the diet during the finishing period to investigate if further improvements can be made, especially for different weights of pigs. In the current study the growth rate of heavy pigs during finish was lower when a high allowance of starter diets were offered post weaning, whereas that of light weight pigs was improved which also equated to an improved 15 and 20 week weight, compared with when a low allowance was offered. It appears that although the performance of heavy weight pigs is improved post weaning when they are offered a high allowance of starter diets, these improvements are not realised during finishing. On the other hand although light weight pigs growth rate was not significantly improved post weaning when they are offered a high allowance of starter diets, their subsequent weight during finish was improved. In agreement with previous workers, pigs with a higher wean weight i.e. 8.5 kg or over had better growth rate between weaning and 20 weeks of age than pigs with a light wean weight (7.1 kg on average) and wean weight had a greater and more consistent effect on post weaning performance than the dietary treatments (Mahan et al., 1998; Lawlor et al., 2002). In previous studies a heavy wean weight for pigs weaned at 28 days of age ranged from 8.5 to 9.5 kg. In the current study, these pigs were classed as medium weight and it was interesting

7 238 E. Magowan et al. / Livestock Science 136 (2011) to note that performance between weaning and 20 weeks of age, and response to dietary treatments, of these medium (8.9 kg at weaning) weight pigs were similar to that of the heavy (10.5 kg at weaning) weight pigs. In agreement with previous workers, a special finishing diet (higher energy and lysine) in the current study reduced feed intake and improved feed conversion ratio due to the higher energy and lysine being provided per kg of feed (Azain, 2001; Brumm and Miller, 1996; Henry and Walker, 1994). However, significant interactions between starter diet allowance and finishing diet on the 20-week weight and growth rate, feed intake and FCR of pigs during finish were also observed. Chiba (1995) observed similar interactions between starter diets and grower diet on the feed intake and FCR of pigs during the grower stage, even though the pigs in their study were individually housed. In the current study pigs that were offered a low allowance of starter diets had a reduced feed intake during finish when they were offered a special finishing diet containing a greater density of energy and lysine than the normal finishing diet. However, since the special finishing diet improved FCR, the growth rate of pigs during finish offered a low allowance of starter diets and either the normal or special finishing diets were statistically similar. In contrast, when pigs were offered a high allowance of starter diets, feed intake remained high when they were offered either the normal or special finishing diets. In this case, the improved FCR when the special finishing diet was offered resulted in an improved growth rate. Overall optimum growth rate both during finish and overall between weaning and 20 weeks of age, was achieved when the nutrient density of the diets remained high or low across the post weaning and finish periods, i.e. when a high allowance of starter diets was offered with a special finishing diet or when a low allowance of starter diets was offered with a normal finishing diet. On the other hand, growth rate was lowered when nutrient density changed from the post weaning to the finishing period i.e. when pigs were offered a low allowance of starter diets post weaning and a special finishing diet or when they were offered a high allowance of starter diets post weaning and a normal finishing diet. It appears that when pigs changed from a low nutrient dense regime to a high nutrient dense diet (low allowance of starter diets and a special finishing diet), feed intake was lowered but feed efficiency could not improve enough to be counteractive. A lower feed intake was expected due to the higher energy and lysine concentration of the finishing diet, but reasons for the extent of the reduction are unclear. More detailed analysis of gut histology would be required to thoroughly investigate the causative factors and there appears to be a lack of information in the published literature regarding the carryover effects of post weaning dietary regimes on feed intake, FCR and gut structure during finish. However, in general it appears that changes in nutrient density across the life of the pig affect the feed intake and feed conversion ratio responses of pigs to varying extents and depend on the pattern of change i.e. high to low density or vice-a-versa. 5. Conclusion A high allowance of starter diets improved post weaning pig performance. Furthermore, the 15 week weight of light weight pigs was also improved when they were offered a high allowance of starter diets post weaning compared with a low allowance. It appears that changes in nutrient density throughout the life of the pig affect the feed intake and feed conversion ratio responses of pigs to varying extents and depend on the pattern of change. When the nutrient density changed from low to high, the effects on weight and growth rate were the result of poorer feed intake during finish whereas when the nutrient density changed from high to low, the effects on weight and growth rate were the result of poorer feed conversion ratio during finish. Overall, light weight pigs were found to eat more and grow faster per kg of body weight than medium or heavy weight pigs. References Allen, J., Magowan, E., Beattie, V.E., McCann, M.E.E., Thompson, A., The Effect of Birth Weight on the Variation in Live Weight of Pigs at Weaning. Proceedings of the British Society of Animal Science, p Azain, M.J., Fat in Swine Nutrition, In: Lewis, A.J., Southern, L.L. (Eds.), Swine Nutrition, 2nd Edition. CRC Press, London, p Brumm, M.C., Miller, P.S., Response of pigs to space allocation and diets varying in nutrient density. J. Anim. Sci. 74, Chiba, L.I., Effects of nutritional history on the subsequent and overall growth performance and carcass traits of pigs. Livest. Prod. Sci. 41, Dritz, S.S., Owen, K.Q., Nelssen, J.L., Goodband, R.D., Tokack, M.D., Influence of weaning age and nursery diet complexity on growth performance and carcass characteristics and composition of high-health status pigs from weaning to 109 kilograms. J. Anim. Sci. 74, Dwyer, C.M., Stickland, N.C., Fletcher, J.M., The influence of maternal nutrition on muscle fibre number development in the porcine foetus and on subsequent postnatal growth. J. Anim. Sci. 72, Henry, W., Walker, N., Response of pigs to dietary energy and protein with particular reference to the early finishing period. Ir. J. Agric. Food Res. 33, Klindt, J., Influence of litter size and creep feeding on preweaning gain and influence of preweaning growth on growth to slaughter in barrows. J. Anim. Sci. 81, Lawlor, P.G., Lynch, P.B., Caffrey, P.J., O'Doherty, J.V., Effect of pre- and post weaning management on subsequent pig performance to slaughter and carcass quality. Anim. Sci. 75, Magowan E., McCann, M.E.E., McCracken, K.J., Beattie, V.E., Bradford, R., Robinson, M.J., Scott, M., Gordon, F.J. and Mayne, C.S. (submitted for publication). Effect of diet and grouping strategy on pig performance and variable growth from weaning to slaughter. Livestock Sci. Magowan, E., McCann, M.E.E., Beattie, V.E., McCracken, K.J., Bradford, R., Scott, M., Robinson, M.J., Gordon, F.J., The Effect of Dietary Regime and Method of Grouping on the Variation in Growth Rate Between Pigs. British Society of Annual Science 2009 Conference proceedings, p Magowan, E., McCann, M.E.E., Beattie, V.E., McCracken, K.J., Henry, W., Smyth, S., Bradford, R., Gordon, F.J., Mayne, C.S., Investigation of growth rate variation between commercial pig herds. Animal 1, Mahan, D.C., Feeding for maximum lean growth. Illinois Pork Ind. Conf, pp Mahan, D.C., Effect of weight, split-weaning and nursery feeding programs on performance responses of pigs to 105 kilograms body weight and subsequent effects on sow rebreeding interval. J. Anim. Sci. 71, Mahan, D.C., Cromwell, G.L., Ewan, R.C., Hamilton, C.R., Yen, J.T., Evaluation of the feeding duration of a phase 1 nursery diet to threeweek-old pigs of two weaning weights. J. Anim. Sci. 76, Morise, A., Seve, B., Mace, K., Magliola, C., Le Huerou-Luron, I., Louveau, I., Impact of intrauterine growth retardation and early protein intake on growth, adipose tissue and the insulin-like growth factor system in piglets. Pediatr. Res. 65, Nyachoti, C.M., Zijlstra, R.T., de Lange, C.F.M., Patience, J.F., Voluntary feed intake in growing-finishing pigs: A review of the main determining factors and potential approaches for accurate predictions. Can. J. Anim. Sci. 84, O'Connell, N.E., Beattie, V.E., Watt, D., Influence of regrouping strategy on performance, behaviour and carcass parameters in pigs. Livest. Prod. Sci. 97, Pluske, J.R., Kerton, D.K., Cranwell, P.D., Campbell, R.G., Mullan, B.P., King, R.H.,Power,G.N.,Pierzynowski,S.G.,Westrom,B.,Rippe,C.,Peulen,O., Dunshea, F.R., Age, sex and weight at weaning influence organ weight and gastrointestinal development f weanling pigs. Aust. J. Agric. Res. 54,

8 E. Magowan et al. / Livestock Science 136 (2011) Pluske, J.R., Hampson, D.J., Williams, I.H., Factors influencing the aggressive and agonistic behaviour of the domestic pig. Aust. J. Exp. Agric. 27, Vallet, J.L., Freking, B.A., Differences in placental structure during gestation associated with large and small pig foetuses. J. Anim. Sci. 85, Weatherup, R.N., Beattie, V.E., McCracken, K.J., Henry, R.W., McIllroy, S.G., Smyth, S., The effects of energy and lysine concentrations in grower diets for pigs on performance from 8 to 12 weeks of age. Ir. J. Agric. Food Res. 41, Wise, T., Roberts, A.J., Christenson, R.K., Relationships of light and heavy foetuses to uterine position, placental weight, gestational age, and foetal cholesterol concentrations. J. Anim. Sci. 75 (8), Wolter, B.F., Ellis, M., Curtis, S.E., Parr, E.N., Webel, D.M., Effects of feeder-trough space and variation in body weight within a pen of pigs on performance in a wean-to-finish production system. J. Anim. Sci. 80,