Effects of high dietary concentration of lactose and increased soyabean meal inclusion in starter diets for piglets

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1 Animal Science 2004, 79: /04/ $ British Society of Animal Science Effects of high dietary concentration of lactose and increased soyabean meal inclusion in starter diets for piglets K. M. Pierce 1, J. J. Callan 1, P. McCarthy 2 and J. V. O Doherty 1 1 Department of Animal Science and Production, University College Dublin, Lyons Research Farm, Newcastle, Co. Dublin, Ireland 2 Volac Feed Ltd, Volac House, Church Street, Killeshandra, Co. Cavan, Ireland john.vodoherty@ucd.ie Abstract A 3 2 factorial experiment was conducted to investigate the interactions between lactofeed 70 (LF70) (860 g/kg whey permeate, 140 g/kg soya-bean meal; Volac International, UK) and soya-bean meal (SBM) or dried skim milk (DSM) in piglet diets. Three hundred and thirty-six piglets were selected after weaning at 21 days with an initial live weight of 6 35 kg. They were blocked on the basis of live weight and within each block assigned to one of six dietary treatments. The pigs were offered the following starter diets : (1) 300 g/kg LF70 with 215 g/kg SBM and 100 g/kg DSM; (2) 200 g/kg LF70 with 215 g/kg SBM and 100 g/kg DSM; (3) 100 g/kg LF70 with 215 g/kg SBM and 100 g/kg DSM; (4) 300 g/kg LF70 with 325 g/kg DSM; (5) 200 g/kg LF70 with 325 g/kg DSM; (6) 100 g/kg LF70 with 325 g/kg DSM. The starter diets were offered for 25 days. Following this, a weaner diet (14 g/kg lysine, 14 5 MJ/kg digestible energy) was given for a period of 12 days. There was a significant interaction between LF70 level and protein source on average daily gain (ADG P < 0 001) and food conversion ratio (FCR P < 0 05) during the starter period. There was a linear increase in ADG and a linear improvement in FCR with increasing LF70 levels in diets with SBM. However, there was a linear decrease in ADG with increasing LF70 levels in diets with DSM. There was a significant interaction (P < 0 001) between LF70 level and protein source on average daily food intake (ADFI) during the starter period. At high LF70 levels, the inclusion of DSM reduced ADFI compared with SBM. However, there was no difference between DSM and SBM at the medium and low LF70 levels. There was a significant interaction between LF70 level and protein source in organic matter digestibility (OMD) (P < 0 01) and gross energy digestibility (GED) (P < 0 01). The pigs offered diets containing DSM had a significantly lower OMD and GED at low LF70 levels compared with pigs offered diets containing SBM. However, the inclusion of DSM had no significant effect on OMD or GED at the medium and high LF70 levels. There was a quadratic response in nitrogen digestibility (ND) with increasing concentrations of LF70 (P < 0 05). There was an increase in ND to 200 g/kg LF70 inclusion, however there was no further increase in ND above 200 g/kg LF70 inclusion. In conclusion, increasing the inclusion of lactofeed from 100 g/kg to 300 g/kg in starter diets where soya-bean meal comprised the principle protein source improved food efficiency and increased daily gain and daily food intake when compared with diets where dried skim milk comprised the principle protein source. Keywords: lactofeed, pigs, skim milk, soya-bean meal. Introduction Dried skim milk (DSM) has long been regarded as a highly digestible protein source for piglets (Armstrong and Clawson, 1984). Feeding diets containing milk products has resulted in improved growth rates and food to gain ratios when compared 445 with maize-soya-bean diets (Hays et al., 1959; Graham et al., 1981; Sissons, 1993; Maxwell and Carter, 2001). However, since milk products are costly, there is a need for cheaper sources of protein that will produce fast and efficient gains in the young pig (Lennon et al., 1971; Sissons, 1993).

2 446 Pierce, Callan, McCarthy and O Doherty Soya-bean meal (SBM) is the most widely used source of supplemental protein in pig diets due to its excellent amino acid profile (Rudolph et al., 1983). However, it has been suggested that the gut morphological changes observed after weaning are caused by immunologically-active soya-bean proteins such as glycinin and ß-conglycinin. These proteins can cause a delayed hypersensitivity reaction (Pluske et al., 1997) such as decreased villous height, increased crypt depth and increased serum anti-soya IgG titres (Sewell and West, 1965; Dunsford et al., 1989; Friesen et al., 1993). Several experiments have shown the benefits of high lactose inclusions in starter diets for pigs in terms of improved daily gain (Mahan, 1992; Owen et al., 1993; O Doherty et al., 2004) and food intake (Giesting et al., 1985; Nessmith et al., 1997b). Lactose has also been shown to improve nutrient digestibility (Owsley et al., 1986; O Doherty et al., 2004). The improved protein digestion (Sewell and West, 1965) observed may result from the microbial fermentation of lactose to lactic acid in the stomach which stimulates proteolytic activity, assisting in the digestion of non-milk proteins (Partridge and Gill, 1993). Lactose has a favourable influence on lactic acid bacteria (Pollmann et al., 1980) and work by Krause et al. (1994) suggested that lactose in the diet may increase the number and diversity of lactobacilli in the gastro-intestinal tract. It is our hypothesis that increasing lactose levels will allow for increased SBM inclusion in the diets of weaning pigs without affecting piglet performance. In the current study, lactose was supplied via Lactofeed 70 (LF70), which contains 860 g/kg whey permeate (700 g of which is lactose) and 140 g/kg SBM. The objective of this experiment was to compare three levels of lactofeed (300, 200 or 100 g/ kg) with two protein sources (SBM and DSM) on growth performance and diet digestibility of weanling pigs. Material and methods Diets This experiment was designed as a 3 2 factorial. It was carried out over two consecutive runs. Three hundred and thirty-six piglets (progeny of Large White (Large White Landrace)) were selected after weaning at 21 ( + 3) days of age with an initial live weight of 6 35 kg. The pigs in run 1 and run 2 had an initial mean live weight of 6 2 kg and 6 5 kg respectively. The piglets were blocked on the basis of weight and within each block assigned to one of six dietary treatments each with a different starter diet (see Table 1). The starter diet was given for 25 days followed by a weaner diet which was offered to all Table 1 Dietary treatments Treatment Lactofeed (g/kg) Soya-bean meal (g/kg) Dried skim milk (g/kg) animals for a further 12 days. From days 37 to 72 the pigs were housed in a grower unit and were given the same weaner diet as during days 25 to 37. The ingredient composition and analysis of the six experimental starter diets and subsequent weaner diet are shown in Table 2. The starter diets were formulated to have identical digestible energy (16 MJ/kg) and total lysine (16 g/kg) contents. All amino acid requirements were met relative to lysine (Close, 1994). Lactofeed 70 (Volac International Ltd, Orwel, Royston, SG8 5QX, UK) consists of 860 g/kg whey permeate and 140 g/kg SBM. Lactofeed contains 955 g/kg dry matter (DM); 700 g/kg lactose; 125 g/kg crude protein; 50 g/kg oil; 90 g/kg ash; 10 g/kg crude fibre, and has a gross energy (GE) content of 15 5 MJ/kg and a digestible energy content of 13 5 MJ/kg. Lactofeed replaced wheat in the experimental diets. Chromium III oxide was added at the time of milling at a concentration of 133 p. p. m. in order to determine nutrient digestibility. Management The pigs were housed in groups of seven (eight replicates per treatment) on fully slated pens (1 68 m 1 22 m). House temperature was maintained at 30ºC in the 1st week and then reduced by approximately 2ºC per week. Pigs were weighed individually at the beginning of the experiment (day 0 = day of weaning), day 7, day 14, day 25 and day 37. The pigs were given food ad libitum. Food was available up to weighing and all remaining food in the trough was weighed back for the purpose of calculating the efficiency of food use. During the experiment, ration samples were taken at the time of feeding and retained for chemical analysis. Faecal samples were collected from all pens on days 10 to 16. On day 37 the pigs were weighed and removed to a grower house where they were grouped in pens of 14 pigs per pen (four replicates per treatment). Their intakes and weight gains were recorded until day 72. Laboratory analysis Both concentrates and faeces were analysed for nitrogen (N), DM, ash, GE, neutral-detergent fibre (NDF) and chromium concentration. Following collection, the faeces were dried at 100ºC for 48 h. The concentrates and dried faeces were milled

3 Lactose and soya-bean meal in starter diets for piglets 447 Table 2 Composition and chemical analysis of experimental diets (as fed) Starter Treatment Weaner Start ph ABC (3) (ml HCl) Composition (g/kg) Lactofeed Extruded wheat Soya-bean meal Skim milk Maize 204 Full fat soya Peas 100 Soya oil Salt 4 Dibasic calcium phosphate 7 Maxus (Avilamycin) Zinc oxide Minerals and vitamins Lysine HCl Methionine Threonine Analysis (g/kg) Dry matter Crude oil Crude protein Crude fibre Neutral-detergent fibre Crude ash Gross energy (MJ/kg) Lactose Lysine Methionine Threonine Tryptophan Diets ABC (3) = acid binding capacity (ph 3). Maxus, Elanco Animal Health, Indianapolis, USA. Calculated concentration of lactose. Calculated from proximate analysis (Ministry of Agriculture, Fisheries and Food, 1991). through a 1-mm screen (Christy and Norris hammer mill). The DM of the concentrates and faeces was determined after drying overnight at 103ºC. Ash was determined after ignition of a known weight of concentrates or faeces in a muffle furnace (Nabertherm, Bremen, Germany) at 500ºC. The N content of both food and faeces was determined as Kjeldahl N 6 25 using the LECO FP 528 instrument (Leco Instruments, UK Ltd, Newby Road, Hazel Grove, Stockport, SK7 5DA, Cheshire). The NDF was determined using a Fibertec extraction unit (Tecator). The GE of the food and faecal samples was determined using a Parr 1201 oxygen bomb calorimeter (Parr, Moline Illinois, USA). Crude oil was determined using the 1043 Soxtec System as derived from the Soxhlet method. Chromium concentration was determined according to the method of Williams et al. (1962). In order to examine the quality of the DSM and diet quality, the ph, acid binding capacity and whey protein N content were determined. The ph of the diets was determined by diluting the samples (w/w) with distilled water using a Mettler Toledo MP 220 ph meter. The acid binding capacity of the diets was determined as the amount (ml) of 1-mol/l HCl required to reduce the ph of the food to ph 3. The whey protein test of the

4 448 Pierce, Callan, McCarthy and O Doherty skim milk was conducted according to a modification of the Harland-Ashworth method (Kuramoto et al., 1959). Statistical analysis The data were analysed using the general linear model procedure of Statistical Analysis Systems Institute (1985). The statistical model used included both the linear and quadratic effects of LF70 inclusion, protein source, run number and the associated interactions between the linear effects of LF70 and protein source and the quadratic effect of LF70 and protein source. Both the performance and digestibility data were adjusted for initial live weight by covariance analysis. Means presented in the tables are least-square means. Results The concentration of lactose (g/kg) in the diets was 260, 190, 120, 372 5, and for treatments 1 to 6 respectively (Table 1). The acid binding capacities (ml of 1-mol/l HCl) of the diets were 52 7, 48 5, 44 5, 53 8, 52 6 and 47 1 for treatments 1 to 6 respectively. The whey protein N content of the skim milk used was 18 0 mg/g. Performance The effect of dietary treatments on average daily gain (ADG), average daily food intake (ADFI) and food conversion ratio (FCR) during the starter, weaner, the combined starter-weaner period and the grower period are shown in Table 3. There was a significant interaction between the linear response to LF70 level and protein source on ADG from days 0 to 7 (P < 0 01). At 300 g/kg LF70, the inclusion of high levels of DSM reduced ADG (P < 0 001) compared with SBM. However, there was no difference between the DSM and SBM diets at the medium and low LF70 levels (P > 0 05). There was a significant interaction between the linear effect of LF70 level and protein source on ADG between days 7 to 14 (P < 0 01), 14 to 25 (P < 0 001), days 0 to 25 (P < 0 001) and during the combined starter-weaner period Table 3 The effect of lactofeed (LF70) level and protein source on pig performance (least-square means and s.e.) Lactofeed (g/kg) Significance Protein source (P) Soya Skim Soya Skim Soya Skim s.e. L (LF70) L (LF70) P P Daily gain (ADG) (g/day) Days *** ** Days ** ** Days ** *** Starter (days 0-25) *** *** Weaner (days 25-37) Starter-weaner (days 0-37) *** *** Days Food intake (ADFI) (g/day) Days Days *** *** Days *** *** Starter (days 0-25) *** *** * Weaner (days 25-37) * Starter-weaner (days 0-37) *** *** * Days Food converstion ratio (FCR) (kg/kg) Days ** ** Days ** Days Starter (days 0-25) * Weaner (days 25-37) Starter-weaner (days 0-37) Days Soya = soya-bean meal. Skim = dried skim milk. L (LF70) = linear response to LF70. There was a significant interaction between the quadratic effect of LF70 and protein source (P < 0 05).

5 Lactose and soya-bean meal in starter diets for piglets 449 (days 0 to 37) (P < 0 001). There was a linear increase in ADG with increasing levels of LF70 in the SBM diets. However, there was a linear decrease in ADG with increasing levels of LF70 in the DSM diets. There was an interaction between the quadratic response to LF70 and protein source on ADFI from days 0 to 7 (P < 0 05). The inclusion of 100 g/kg LF70 to diets high in DSM significantly increased intake compared with SBM. However, there was no effect of high levels of DSM on ADFI at 200 or 300 g/kg LF70. There was a significant interaction between the linear response to LF70 level and protein source on ADFI from days 7 to 14, 14 to 25, during the overall starter period (days 0 to 25) and during the combined starter-weaner period (days 0 to 37) (P < 0 001). During days 7 to 14, the inclusion of high levels of DSM significantly reduced ADFI at the medium (P < 0 05) and high (P < 0 001) LF70 levels compared with SBM. However, the inclusion of high levels of DSM had no effect on ADFI at the low LF70 level (P > 0 05). At the high LF70 inclusion level, the inclusion of high levels of DSM decreased ADFI on days 14 to 25, during the overall starter period (days 0 to 25) and during the combined starter-weaner period (days 0 to 37) (P < 0 001) compared with SBM. However, there was no difference in ADFI between DSM and SBM at the medium and low LF70 levels (P > 0 05). There was a significant interaction between linear effect of LF70 level and protein source in FCR during days 0 to 7 (P < 0 01) and during the overall starter period (days 0 to 25) (P < 0 05). The inclusion of high levels of DSM at the medium (P < 0 05) and high (P < 0 001) LF70 levels resulted in a significant deterioration in FCR during days 0 to 7 compared with SBM. However, the inclusion of high levels of DSM had no effect on FCR at the low LF70 level (P > 0 05). There was a linear improvement in FCR with increasing LF70 levels and SBM diets during the starter period. However, there was a linear deterioration in FCR with increasing LF70 levels and DSM diets. Pigs offered diets containing SBM had a significantly improved FCR during days 7 to 14 compared with pigs offered high levels of DSM (P < 0 01) (1 63 v s.e ). During the grower period (days 37 to 72), there was a numerical tendency for pigs previously given the high levels of DSM to have increased ADG (642 g/ day v. 617 g/day, s.e. 0 13) compared with those previously given the SBM diets. Digestibility The effects of LF70 level and protein source on the apparent digestibilities of the starter diets are presented in Table 4. There was a significant interaction between the linear effect of LF70 level and protein source in the apparent digestibility of DM (P < 0 01), organic matter (OM) (P < 0 01), NDF (P < 0 05) and GE digestibilities (P < 0 01) as well as the digestible energy (DE) concentration (P < 0 001). Pigs offered diets containing high levels of DSM had significantly lower DM (P < 0 01), OM (P < 0 001), GE (P < 0 01) and NDF (P < 0 05) digestibilities at low LF70 levels than pigs offered diets containing SBM. However, the inclusion of high levels of DSM had no significant effect on DM, OM, NDF or GE digestibilities at the medium and high LF70 levels (P > 0 05). Pigs offered diets containing the high level of DSM had a significantly lower DE content at the low LF70 inclusion compared with the medium (P < 0 01) and high (P < 0 001) LF70 levels. However, LF70 level had no significant effect on the DE in the diets containing SBM (P > 0 05). Table 4 The effect of lactofeed (LF70) and protein source on the apparent digestibility and digestible energy content of starter diets (leastsquare means and s.e.) Lactofeed (g/kg) Significance Protein source (P) Soya Skim Soya Skim Soya Skim s.e. P L (LF70) P L (LF70) Q (LF70) Faeces dry matter Digestibility coefficients Dry matter ** ** ** ** Organic matter *** ** * ** Nitrogen *** * Neutral-detergent fibre * * * ** Energy ** ** * ** Digestible energy (MJ/kg) *** *** Soya = soya-bean meal. Skim = dried skim milk. L (LF70) = linear response to LF70.

6 450 Pierce, Callan, McCarthy and O Doherty There was a quadratic response in N digestibility with increasing concentrations of LF70 (P < 0 05). There was an increase in N digestibility to 200 g/kg LF70 inclusion, however there was no further increase in N digestibility above 200 g/kg LF70 inclusion. Discussion This study investigated the effects of three different levels of lactofeed in diets containing either DSM or SBM as the principle protein source on growth performance and nutrient digestibility in 3-week-old weaned piglets. The concentration of lactose (g/kg) in the diets was 260, 190, 120, 372 5, and for treatments 1 to 6 respectively and this is not surprising since lactofeed contains approximately 700 g/kg lactose and 140 g/kg SBM. O Doherty et al. (2004) found that this small increase in SBM as a result of lactofeed inclusion is unlikely to have any impact on results obtained. Increasing the concentration of lactofeed from 100 g/ kg to 300 g/kg in diets containing SBM resulted in improvements in nutrient digestibility and in the performance criteria measured. The improved daily gain of pigs given diets containing SBM with increasing lactose levels is in agreement with studies conducted by Owen et al. (1993), Touchette et al. (1995), Nessmith et al. (1997b) and O Doherty et al. (2004). The beneficial effects of lactose on growth performance were still evident in this experiment until day 37. Similar results were reported by Mahan (1993) and Touchette et al. (1996) where increasing lactose levels resulted in linear increases in daily gain to 6 weeks post weaning. The improved performance of pigs given high lactose concentrations has previously been attributed to an increase in food intake (Giesting et al., 1985; Nessmith et al., 1997a; O Doherty et al., 2004) and an improved nutrient digestibility (Sewell and West, 1965; Owsley et al., 1986; Cera et al., 1988; Tokach et al., 1989; O Doherty et al., 2004). In the present study increasing lactofeed increased food intake in the 1st week post weaning and subsequent interactions with protein source resulted in increased intakes on high lactofeed and SBM diets throughout the experiment. Increasing food intake in the immediate post-weaning period promotes gut health through the stimulation of mucosal growth and function, which may preserve the integrity of the small intestine (Pluske, 2001). Therefore, this increased intake may have resulted in the improved food efficiency observed in pigs given the SBM and lactofeed diets. There was a reduction in food intake with high lactofeed levels and DSM. The casein fraction of skim milk has been found to decrease food intake (Tokach et al., 2003) and this may explain the reduced food intake of pigs on skim milk in this experiment. Dritz et al. (1994) also found no benefit from skim milk inclusion when the diet contained adequate quantities of plasma and lactose. During the starter period, the skim milk and high lactofeed diet resulted in a proportional reduction in food intake of proportionately 0 19 compared with SBM and high lactofeed. This decrease in food intake resulted in a proportional decrease in daily gain of proportionately 0 4 in pigs given high skim milk diets. In the present experiment, results for DM, organic matter and energy digestibility agree with previous research that increasing lactose levels increases the nutrient digestibility of SBM (Owsley et al., 1986; Tokach et al., 1989 and O Doherty et al., 2004). This increase in nutrient digestibility may be due to a number of reasons. Firstly, the increased intake of pigs given high lactofeed levels and SBM may influence pancreatic enzyme synthesis and secretion, therefore improving nutrient digestibility (Tsiloyiannis et al., 2001). Secondly, lactobacilli present in the gut readily ferment lactose to lactic acid and the increased acidity aids the digestion of non-milk proteins (Partridge and Gill, 1993). Thirdly, feeding lactose slows digesta flow rates in the ileum therefore increasing the time available for enzymatic digestion of food (Turlington et al., 1989). As pigs do not secrete enzymes that hydrolyse NDF, the observed increase in NDF disappearance may be the result of increased bacterial fermentation due to increased lactofeed inclusion. Work by Pierce et al. (2004) showed that high concentrations of lactofeed increased the concentration of lactobacilli in the large intestine. Higher concentrations of total volatile fatty acids and a decreased colonic ph as a result of high lactofeed inclusion are indicative of increased bacterial fermentation (Pierce et al., 2004). In the current study, the pigs given the low lactofeed level had a proportionally lower NDF disappearance of 0 18 and 0 20 compared with pigs given the medium and high lactofeed levels. Previous studies have shown that the greatest acidification benefits are observed when diets are formulated with cereals and plant proteins (Falkowski and Aherne, 1984; Partanen and Mroz, 1999) while smaller effects are seen in diets containing milk products (Giesting et al., 1991). The conversion of lactose in milk products to lactic acid by lactobacilli (Partridge and Gill, 1993) creates a reduction in ph in the stomach and therefore reduces the requirement for diet acidification (Easter, 1993). This response is evident in the present experiment

7 Lactose and soya-bean meal in starter diets for piglets 451 where the inclusion of lactofeed increased protein digestion in diets containing SBM. However, the overall lower protein digestibility of diets containing high levels of DSM is in contrast to many previous experiments (Hays et al., 1959; Wilson and Leibholz, 1981; Li et al., 1990). A whey protein N test was conducted on the skim milk used in the experimental diets. This test forms the basis for heat treatment classifications which are important in indicating the suitability of skim milk for various uses. A value of 18 mg/g whey protein N obtained for the skim milk in this experiment indicated that no heat damage had occurred and the skim milk was of adequate quality for inclusion in piglet starter diets. The acid binding capacity test conducted on the diets showed that the diets high in skim milk had a higher acid binding capacity at all lactofeed levels compared with diets containing SBM. This increased acid binding capacity, combined with a limited ability of the young pig to secrete gastric acid (Mavromichalis, 2001) may have resulted in an elevated gastric ph impairing proteolytic activity. Combined with a lower food intake, the lower performance of pigs on the skim milk diets may have been partly due to low protein digestibility. Conclusion Increasing the inclusion level of lactofeed from 100 g/kg to 300 g/kg, when SBM comprised the principle protein source, improved food efficiency and increased daily gain and daily food intake compared with diets where dried skim milk comprised the principle protein source. The inclusion of increasing levels of lactofeed was also found to improve N digestibility. The use of SBM in combination with high concentrations of lactofeed offers an alternative protein source to animal proteins in starter diets for pigs, thereby reducing the cost of starter diets. 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