Rearing veal calves with respect to animal welfare: effects of group housing and solid feed supplementation on growth performance and meat quality

Livestock Production Science 75 (2002) 269–280 www.elsevier.com / locate / livprodsci

Rearing veal calves with respect to animal welfare: effects of group housing and solid feed supplementation on growth performance and meat quality a, a a a b G. Xiccato *, Angela Trocino , P.I. Queaque , A. Sartori , A. Carazzolo a

Dipartimento di Scienze Zootecniche, Universita` degli Studi di Padova, Agripolis, via Romea 16, I-35020 Legnaro ( PD), Italy b Veneto Agricoltura, Agripolis, via Romea, I-35020 Legnaro ( PD), Italy Received 19 February 2001; received in revised form 6 November 2001; accepted 6 November 2001

Abstract This study aims to evaluate how rearing techniques that improve veal calf welfare affect growth performance and carcass and meat quality, by comparing both traditional rearing in individual stalls with group rearing in collective pens and exclusive milk feeding with maize grain supplementation. Eighty male calves were raised from 60 days-of-age (live weight 76.465.5 kg) until slaughter (at 182 and 189 days-of-age). Both group rearing and maize grain supplementation significantly improved growth performance (final live weight: 1 7 kg in group-reared calves compared to individually reared calves; and 1 10 kg in maize-supplemented calves compared to exclusively milk-fed calves) and carcass conformation, with no differences in dressing percentage. Group rearing increased blood packed cell volume value. Neither the type of housing nor the feeding system significantly modified carcass or meat colour or the main physical and sensory traits of the meat. Carcass fatness and meat ether extract concentration were higher in the calves reared in individual stalls or supplemented with maize grain. Our results suggest that rearing veal calves in pens and providing solid feed supplements may improve growth performance without impairing carcass and meat quality.  2002 Elsevier Science B.V. All rights reserved. Keywords: Beef cattle; Group rearing; Maize grain; Growth performance; Meat quality; Sensory evaluation

1. Introduction Until now, traditional veal calf rearing techniques have ensured final product quality in terms of the pale colour, tenderness and leanness of meat requested by the consumer. However, housing in individual stalls with tethers and exclusive milk *Corresponding author. Tel.: 1 39-049-827-2639; fax: 1 39049-827-2669. E-mail address: [email protected] (G. Xiccato).

feeding has a negative effect on animal behaviour and welfare (Broom, 1991; Stull and McDonough, 1994). Given that public opinion has become increasingly more sensitive to animal welfare, European legislation has prescribed veal calf rearing conditions that provide for a progressive shift from housing in individual stalls to collective pens, and from exclusive milk feeding to solid feed supplementation [Council Directives 91 / 629 / EC (OJEC, 1991) and 97 / 2 / EC, (OJEC, 1997)]. So far, calf housing research has dealt primarily

0301-6226 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0301-6226( 01 )00319-0

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with the effects of different types of individual cages on growth performance, behaviour and welfare (Fisher et al., 1985; Terosky et al., 1997; Wilson et al., 1999). Other studies have reported improvements in social relationships and reduction of both stress and abnormal behaviour when calves were reared in small groups (Albright et al., 1991; Smits and de Wilt, 1991). Group rearing, however, exerted negative effects on carcass and meat quality, in particular a darker colour (Andrighetto et al., 1999). Supplementation with solid feed allows veal calves to develop a rumen and rumination as in normal digestive physiology (Morisse et al., 2000). However, the supplementation with cereal (Latrille et al., 1983; Beauchemin et al., 1990; Pommier et al., 1995) or roughage (Egger and Bourgeois, 1993; Egger, 1995; Morisse et al., 2000) in veal calf often provoked darker carcass and meat colour, although permitted growth performance similar to that obtained with exclusive milk diets. On the basis of the results above, more pronounced negative effects are likely to be observed when veal calves are simultaneously reared in groups and fed solid feeds in addition to milk replacer. This study aims to evaluate how rearing techniques that improve animal welfare affect the performance of veal calves. Our objective was to compare the effects of (i) the housing system (traditional rearing in individual stalls versus group rearing in collective pens), (ii) the type of feeding (an exclusive milk diet versus supplementation with maize grain), and (iii) the interaction between housing and feeding on veal calf growth performance, carcass characteristics and meat quality.

2. Materials and methods

2.1. Animals and experimental facilities Eighty male Polish Holstein calves were moved from an open-air to a closed stable (in North-East Italy) at the age of around 30 days. After a 30-day period of adaptation and sanitary isolation, the calves (live weight 76.465.5 kg) were moved to a neighbouring fattening stable and housed in the same room under controlled environmental conditions. The room (13 m wide 3 26 m long) was divided into two

sectors by a central feeding alley (2 m wide). The room contained 40 individual partial stalls and 10 collective pens built on a wooden slatted floor elevated 0.35 m above a concrete floor. The fronts and the sides of the individual stalls were made of wooden boards. The fronts were 1.20 m high above the wooden floor. The sides of the stalls were 1.03 m high above the wooden floor and extended 0.70 m from the front towards the rear of the stall. Each stall (1.15 m 2 ) was 0.65 m wide (including the side thickness) and 1.80 m long. The animals were tethered to the front of the stall. A back alley, made of concrete and the same height as the wooden floor and extending 0.95 m from the rear of the stalls to the wall of the room, permitted inspection and movement of the animals. The collective pens (7.04 m 2 ) were 2.56 m wide and 2.75 m long. They were made by joining four adjacent stalls and the corresponding back alley. The pens were separated by tubular stainless steel partitions that extended 2.05 m from the sides of the stalls to the wall of the room, with gates to permit the movement of animals and people. The three wooden sides of the four stalls inside the collective pens were maintained to permit calm consumption of milk and the control of individual milk intake. One of two individual stalls and collective pens were equipped with stainless steel feeders for the administration of solid feed.

2.2. Experimental design Forty calves were housed in 40 individual stalls with tethers, the other 40 in 10 collective pens without tethers in groups of four. Twenty calves kept in the individual stalls and 20 calves kept in five collective pens were exclusively milk-fed (group Milk), the remaining calves were supplemented with maize grain (group Maize).

2.3. Milk feeding and maize grain supplementation The calves were fed in buckets twice a day (at 07:00 and 17:00 h) with commercial milk replacers, based on sprayed skimmed milk powder reconstituted at 38–40 8C. From week 1 to week 8 of the experiment (first period), two starter milk replacers (S1 and S2) were mixed in equal parts. From week

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9, the two starters were substituted by a finishing milk (F) used until the end of the trial (second period). The feeding plan was based on a progressive increase of milk powder concentration from 10% in the 1st week to 20% in the 16th week, with an average concentration of 13% during the first period and 19% during the second period. The calves were fed with fixed amounts of reconstituted milk which progressively increased from 12 kg / day in the first week to 16 kg / day from the 6th week and thereafter. During the trial, the amount of maize grain supplementation was progressively increased from 30 g / calf / day in the 1st week to 550 g / calf / day in the 14th week and thereafter. The chemical composition of the three milk replacers and the maize grain is reported in Table 1. Ether extract was lower in the starter replacers (19.3% on average) than in the finishing replacer (20.9%). Iron concentration was lower in the finishing milk (13 vs. 10 mg / kg). Maize iron concentration was about double that of milk replacers.

2.4. Experimental recordings Individual live weight was measured at the beginning of the trial, at 66 days, and before moving the calves from the stable to the slaughterhouse. Refusals of reconstituted milk were recorded individually after each meal. Maize grain intake was recorded daily as individual data in stalls and as group basis data in pens. Three blood samples were taken after 15, 71, and 113 days of the trial to measure the packed cell volume (PCV) according to the International Committee for Standardisation in Haematology (ICSH, 1967).

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2.5. Slaughter, carcass traits and meat sampling Due to the high number of animals, the calves were slaughtered in two periods, after 122 and 129 days (40 animals per slaughter), in order to permit all the necessary recordings on carcasses at the slaughterhouse and on meat in the laboratory. At the first slaughter 20 calves from individual partial stalls (10 calves of group Milk and 10 calves of group Maize) and 20 calves from six collective pens (10 calves of group Milk and 10 calves of group Maize) were slaughtered. Four pens (two per feeding group) were completely emptied, and two pens (one per feeding group) were partially emptied (two calves out of four). At the second slaughter, after 1 week, the remaining 40 calves were slaughtered. The same procedures were used in the two slaughters. The last meal was supplied at 17:00 h the day before slaughter. At 05:00 h, the calves were individually weighed at the stable before being loaded onto the truck. The transport to the slaughterhouse took around 2 h. All calves were kept in an open air paddock and slaughtered within 1 h of arrival in accordance with the standard procedure at the slaughterhouse. The carcasses were weighed immediately after slaughter and after 48 h in a ventilated refrigerator at 4 8C. The refrigerated carcasses were graded by an official evaluator for conformation, fatness and colour. Conformation was assessed using the EUROP method with a modified scale ranging from 1 to 9 (9 5 E, 7 5 U, 5 5 R, 3 5 O, 1 5 P) to consider intermediate assessments; fatness was assessed using a scale ranging from 1 (low) to 5 (very high); colour was assessed with a scale from 1 (pale) to 5 (dark). The sample cut, made up by the 6th, 7th and 8th ribs including the proximal part of the ribs, was

Table 1 Chemical composition (% as fed) of milk replacers and maize grain

Dry matter (%) Ether extract (%) Crude protein (%) Crude fibre (%) Ash (%) Iron (mg / kg)

Milk replacer S1

Milk replacer S2

Milk replacer F

Maize grain

95.86 20.88 21.72 0.74 6.96 13.44

95.99 17.73 21.42 0.63 6.18 12.77

95.68 20.86 21.88 0.28 6.35 10.08

87.31 3.88 7.98 3.32 1.33 25.90

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taken from the right half carcass. The three ribs were separated, put under vacuum in plastic bags and transported to the laboratory of our Department. The 6th rib was stored at 4 8C until the next day, when the m. longissimus thoracis was separated and prepared for chemical analysis. The 7th rib was stored at 2 18 8C and later submitted to a sensory panel test. The 8th rib was immediately dissected for rheological measurements.

2.6. Dissection and rheological measurements The 8th rib was dissected and divided into the longissimus muscle, other muscles, dissectible fat, and bone. The ultimate pH was measured on five points of the longissimus muscle using a pH meter (HI 9025 C, Hanna Instruments S.p.A., Sarmeola di Rubano, Padova, Italy) equipped with a combined Ingold electrode (406 M3). A 2.5-cm-thick slice was cut from the same muscle. The newly cut surface was exposed to artificial light for 1 h at 4 8C before measuring colour on five points [L*a*b* method; CieLab (CIE, 1976)] using a colorimeter (Minolta CR100 Chromameter, Minolta Corp., Ramsey, NJ, USA). The 2.5-cm slices, packed in plastic bags, were cooked in a water bath at 70 8C for 50 min to measure cooking losses. Shear force was measured using an Instron machine (model 1140) equipped with a Warner–Bratzler device on 10 cores (1.25-cmdiameter) cut from the cooked slice parallel to the fibre muscle direction (Shackelford et al., 1991).

2.7. Sensory analysis The sensory evaluation was performed on the 7th rib. The ribs were cooked for about 45 min in a pre-heated oven at 250 8C, until a core temperature of 75 8C was reached. From the longissimus muscle of each rib, five pieces of cooked meat, 3–4-cmthick, were cut parallel to the muscular fibres and submitted to panellists. Five ribs per session were analysed in 16 sessions. The samples were evaluated by a trained panel of five judges who graded samples for tenderness, texture, juiciness, fibrousness and aroma on a 9-point scale (from 1, denoting the least

favourable condition, to 9, the most favourable condition).

2.8. Chemical analysis Milk replacers and maize grain were analysed using AOAC methods (AOAC, 1990). Iron concentration in diets was measured by atomic absorption spectrometry at 248.3 nm wavelength (Martillotti et al., 1987). The longissimus muscle separated from the 6th rib was minced and freeze-dried. Freeze-dried samples were analysed according to AOAC (1990) to measure residual moisture concentration, ether extract by Soxhlet, crude protein by Kjeldahl, and ash. Gross energy concentration was determined using an adiabatic bomb calorimeter (Martillotti et al., 1987). The fatty acid composition of fresh muscle was determined after lipid extraction (Folch et al., 1957) by gas-chromatography (AOAC, 1965) on an Omegavax 250 column (30 m 3 0.25 mm I.D., 0.25 mm film thickness) (Supelco, Bellefonte, PA, USA), using a fatty acid methyl esters mixture as a standard (189-19, Sigma Chemical Co., St Louis, MO, USA). Cholesterol concentration was measured using highperformance liquid chromatography (HPLC) according to Casiraghi et al. (1994). Meat haem iron was measured according to Hornsey (1956).

2.9. Statistical analysis Statistical analysis was performed by using threeway analysis of variance that considered the effect of housing system, type of feeding, and age at slaughter, and the corresponding interactions. The GLM procedure of SAS (SASI, 1991) was used for all analyses. Maize grain intake was not analysed statistically, because it was recorded as individual data for calves housed in stalls and as average data for calves reared in groups.

3. Results The age at slaughter significantly affected only final live weight (247 vs. 257 kg in calves slaug-

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htered at 122 and 129 days of age, respectively; P , 0.001) and carcass weight. Since no significant effect on growth performance, carcass traits and meat quality was recorded, the effect of age at slaughter is not reported in the tables or discussed. Moreover, due to the absence of significant interaction between the housing system and the type of feeding, the two effects are described separately.

3.1. Growth performance The effects of the housing system and feeding on calf growth performance are reported in Table 2. The calves reared in groups showed higher final live

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weight than calves reared individually (255 vs. 249 kg, P , 0.05) due to the higher daily weight gain (P , 0.001) during the second period. No difference was found in milk powder intake, while feed efficiency (the live weight gain to milk powder intake ratio) was significantly higher in group-reared calves during both the second part of the trial (P , 0.001) and the entire period (P , 0.05). The effect of feeding was more pronounced than the effect of the housing system and evident at an earlier stage (Table 2). Calves fed maize grains were heavier than calves fed an exclusive milk diet after 66 days of the trial (165 vs. 159 kg, P , 0.001). During the second period, this difference in live

Table 2 Growth performance of veal calves Housing

Live weight (kg) Initial Intermediate Final Daily weight gain (kg / day) 1st period 2nd period Entire period Reconstituted milk intake (l / day) 1st period 2nd period Entire period

P

Individual

Group

76.3 162.0 249.2

76.4 161.3 254.7

1.30 1.47 1.38

13.4 15.1 14.2

1.29 1.57 1.42

13.3 15.1 14.2

Milk powder intake (kg / day) 1st period 2nd period Entire period

1.75 2.87 2.28

1.74 2.86 2.27

Maize grain intake b (kg / day) 1st period 2nd period Entire period

0.11 0.26 0.18

0.11 0.26 0.18

Feed efficiency (weight gain / milk powder) 1st period 0.74 2nd period 0.51 Entire period 0.61

0.74 0.55 0.62

n.s., P . 0.05; *P , 0.05; **P , 0.01; ***P , 0.001. a Residual standard deviation. b Data not statistically analysed.

n.s. n.s. *

n.s. *** *

n.s. n.s. n.s.

n.s. n.s. n.s.

n.s. *** *

Feeding Milk

Maize

76.1 158.5 247.3

76.7 164.8 256.7

1.25 1.49 1.36

13.3 15.1 14.2

1.34 1.54 1.43

13.4 15.1 14.2

1.74 2.86 2.27

1.75 2.87 2.28

0 0 0

0.21 0.52 0.36

0.72 0.52 0.60

0.76 0.54 0.63

P

R.S.D.a

n.s. *** ***

5.7 7.7 12.0

*** * ***

0.07 0.11 0.08

n.s. n.s. n.s.

0.07 0.09 0.07

n.s. n.s. n.s.

0.01 0.02 0.01

*** n.s. ***

0.04 0.04 0.03

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weight reached 10 kg (P , 0.001). All the maize supplied was ingested by the calves. In the collective pens, the maize intake was obviously impossible to measure individually. Feed efficiency proved statistically higher in calves supplemented with maize than in calves fed only milk, especially during the first period (P , 0.001). However, when maize intake was also considered, feed efficiency (live weight gain / total dry matter intake) was lower in calves supplemented with maize (0.57) than in calves fed only milk (0.63). After 15 days of trial, the calves presented similar PCV values (Table 3). After 71 days, the calves

reared in groups showed higher PCV than those reared individually (P , 0.05). This difference increased after 113 days (25.8 vs. 22.7%, respectively; P , 0.001). Feeding treatment did not affect PCV.

3.2. Slaughter results and carcass evaluation The slaughter results and carcass evaluation are reported in Table 4. The housing system did not affect carcass weight, dressing percentage, or carcass evaluation for conformation, fatness or colour scores. The effect of maize grain supplementation was

Table 3 Blood packed cell volume (PCV, %) of veal calves Day of trial

15 71 113

Housing

P

Individual

Group

30.9 25.1 22.7

31.3 26.7 25.8

Feeding

n.s. * ***

Milk

Maize

31.4 25.5 24.3

30.9 26.2 24.2

P

R.S.D.

n.s. n.s. n.s.

3.18 3.20 3.48

n.s., P . 0.05; *P , 0.05; ***P , 0.001.

Table 4 Slaughter results, carcass assessment and rib composition of veal calves Housing

Hot carcass weight (kg) Hot dressing percentage a (%) Cold carcass weight after 48 h (kg) Cold dressing percentage a (%) Refrigeration losses (% of hot carcass) Carcass commercial assessment Conformation b Fatness c Colour d Rib (g) Rib composition (%) Meat Dissectible fat Bone

P

Individual

Group

149 60.0 147 58.8 1.86

153 60.0 150 58.9 1.93

3.23 2.72 3.10 736 59.7 22.0 18.3

n.s., P . 0.05; *P , 0.05; **P , 0.01; ***P , 0.001. a Calculated on final live weight at the stable. b 9 5 E, 7 5 U, 5 5 R, 3 5 O, 1 5 P. c 1 5 low, 3 5 average, 5 5 very high. d 1 5 pale, 3 5 pink, 5 5 dark.

Feeding

P

R.S.D.

Milk

Maize

n.s. n.s. n.s. n.s. n.s.

148 59.7 145 58.6 1.89

155 60.2 152 59.1 1.89

*** n.s. *** n.s. n.s.

8 1.6 8 1.6 0.22

3.83 2.53 3.28 777

n.s. n.s. n.s. *

3.08 2.45 3.20 737

3.98 2.80 3.17 776

** * n.s. *

1.40 0.65 0.89 73

60.3 20.5 19.2

n.s. n.s. n.s.

60.4 20.7 18.9

59.5 21.9 18.6

n.s. n.s. n.s.

4.6 3.7 3.3

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also more important than the housing system on carcass assessment, while no difference was observed in terms of dressing percentage. The carcasses of maize-fed calves were heavier, had better conformation, and were fatter, with no differences in colour score when compared to exclusively milk-fed calves. Rib weight was higher in group-reared calves than in individually-reared calves (Table 4). Likewise, rib weight was higher in maize-fed animals than in milk-fed animals. The rib composition was not affected by the housing system.

3.3. Meat quality The meat colour (L*a*b*) confirmed the assessment of colour performed on carcasses, i.e. the absence of differences due to the housing system (Table 5). No difference was measured in ultimate pH, while shear force was higher (P , 0.05) in group-reared calves than in individually-reared calves.

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The sensory properties of the meat were unaffected by the experimental factors (Table 6). Ether extract and gross energy concentration accounted for the main differences in chemical composition between the experimental groups (Table 7). Higher ether extract (P , 0.05) and gross energy concentrations (P , 0.001) were measured in the meat of individually-reared calves than in that of group-reared calves, consistent with the higher fat proportion found in the sample joint. The meat of calves supplemented with maize grain showed higher ether extract and gross energy concentrations than that of exclusively milk-fed calves, as indicated above by the carcass fatness score. The fatty acid composition of meat fat is reported in Table 8. Changes in C18:2, C18:3, C20:4 and C20:5 acids accounted for the higher incidence of polyunsaturated fatty acids in the meat of calves reared in pens in comparison with those reared in stalls. Maize grain supplementation determined a lower incidence of polyunsaturated fatty acids compared to exclusive milk feeding.

Table 5 Longissimus muscle characteristics Housing

Ultimate pH L* a* b* Cooking losses (%) Shear press force (kg / cm 2 )

P

Individual

Group

5.53 54.07 11.50 6.96 25.71 1.96

5.53 52.72 11.32 6.57 23.64 2.30

Feeding

n.s. n.s. n.s. n.s. n.s. *

Milk

Maize

5.53 53.26 11.50 6.67 24.95 2.15

5.53 53.52 11.32 6.86 22.41 2.11

P

R.S.D.

n.s. n.s. n.s. n.s. n.s. n.s.

0.22 4.04 2.27 1.61 5.02 0.60

n.s., P . 0.05; *P , 0.05.

Table 6 Sensory meat quality traits Housing

Tenderness Texture Juiciness Fibrousness Aroma

P

Individual

Group

5.00 5.19 4.01 4.25 4.36

4.74 4.99 4.01 3.97 4.39

n.s. n.s. n.s. n.s. n.s.

Scale from 1 (least favourable) to 9 (most favourable); n.s., P . 0.05.

Feeding Milk

Maize

4.81 4.98 4.00 3.96 4.39

4.93 5.20 4.02 4.25 4.36

P

R.S.D.

n.s. n.s. n.s. n.s. n.s.

1.65 1.67 1.24 1.14 0.49

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Table 7 Chemical composition of longissimus muscle Housing

Water (%) Ether extract (%) Crude protein (%) Ash (%) Haem iron (mg / 100 g) Cholesterol (mg / 100 g) Gross energy (MJ / kg)

P

Individual

Group

75.64 2.04 21.19 1.13 5.61 60.65 5.70

76.06 1.72 21.04 1.18 5.77 60.98 5.46

Feeding

* * n.s. n.s. n.s. n.s. ***

Milk

Maize

75.98 1.72 21.16 1.14 5.78 61.24 5.51

75.71 2.05 21.07 1.17 5.60 60.37 5.65

P

R.S.D.

n.s. ** n.s. n.s. n.s. n.s. *

0.74 0.55 0.52 0.13 1.41 2.65 0.27

P

R.S.D.

n.s. n.s. n.s. n.s. * n.s. n.s. n.s. n.s. n.s. * * n.s. n.s. n.s. n.s. * * n.s. n.s. * n.s.

0.05 0.67 0.19 0.07 1.20 0.38 0.10 0.20 1.18 2.12 1.70 0.04 0.07 0.07 0.05 0.13 0.62 0.07 1.64 2.34 2.36 0.08

n.s., P . 0.05; *P , 0.05; **P , 0.01; ***P , 0.001. Table 8 Fatty acid (FA) composition (% of total FA) of longissimus muscle Housing

C12:0 lauric C14:0 myristic C14:1 myristoleic C15:1 cis C16:0 palmitic C16:1 cis C17:0 C17:1 cis C18:0 stearic C18:1 n-9 oleic C18:2 n-6 linoleic C18:3 n-3 linolenic C20:0 C20:1 n-9 C20:2 n-6 C20:3 n-3 C20:4 n-6 arachidonic C20:5 n-3 EPA Saturated FA (SFA) Monounsaturated FA Polyunsaturated FA (PUFA) PUFA / SFA

P

Individual

Group

0.43 4.57 0.65 0.15 23.70 3.26 0.65 0.34 15.06 38.58 9.29 0.44 0.08 0.20 0.09 0.36 2.00 0.15 44.59 43.02 12.38 1.25

0.41 4.52 0.69 0.16 23.30 3.18 0.65 0.30 14.94 37.84 10.31 0.46 0.07 0.19 0.09 0.40 2.27 0.16 44.08 42.21 13.73 1.27

n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. ** n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. * n.s.

Feeding Milk

Maize

0.43 4.57 0.64 0.15 23.20 3.22 0.64 0.31 15.04 37.79 10.26 0.46 0.07 0.20 0.09 0.40 2.28 0.17 44.12 42.16 13.73 1.27

0.41 4.51 0.69 0.16 23.80 3.21 0.66 0.34 14.97 38.63 9.36 0.44 0.08 0.20 0.09 0.35 1.99 0.14 44.54 43.07 12.38 1.25

n.s., P . 0.05; *P , 0.05; **P , 0.01.

4. Discussion

4.1. Effect of the housing system Housing calves in group pens, in conditions that improve animal welfare with increased movement and social relationship, stimulated growth performance when compared to traditional housing with tethers in individual stalls.

When calves were reared individually, the possibility for movement in larger cages without tethers improved weight gain and feed efficiency in comparison with animals kept in small cages with tethers (Fisher et al., 1985). Data recorded on the effects of group housing are rather contrasting. Our results confirm those of Warnick et al. (1976) and Andrighetto et al. (1999), who observed a favourable effect of group rearing on growth performance in the

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late period of growth. On the other hand, Smits and de Wilt (1991) did not observe any difference caused by the housing system, while Stull and McDonough (1994) reported lower live weight at 16 weeks for veal calves reared in group-pens compared to individual stalls. When group-rearing is adopted, growth performance may be influenced by the number of calves per pen or the stocking density, of which the specific effects have not yet been sufficiently investigated. The improvement in welfare conditions of groupreared calves is also documented by the reduction of anaemia, with an increase in PCV from 22.7 to 25.8%, which corresponds approximately to haemoglobin concentrations of 7.5 and 8.6 g / 100 ml, respectively. The PCV value is faster and cheaper to determine than the haemoglobin value, equally descriptive of the condition and approximately three times the haemoglobin concentration (in g / 100 ml) (Plassiart et al., 1998a,b). The condition of anaemia in which calves are kept for the purpose of veal production is one of the major criticisms raised by the public. According to Schwartz (1990), haemoglobin levels ranging from 7 to 8 g / 100 ml and below 7 g / 100 ml are signs of marginal and clinical anaemia, respectively. Reece and Hotchkiss (1987) observed low growth performance in seriously anaemic calves (haemoglobin: 4.8 g / 100 ml at 15 weeks) reared in individual stalls with tether and fed exclusively milk replacer without iron supplementation. In practical conditions, however, the correlation between haemoglobin level and growth performance may not be so close (Plassiart et al., 1988b; Wilson et al., 1995). Neither marginal nor slight clinical anaemia seem to affect the health status and growth performance of calves in the period from 12 to 16 weeks-of-age (Stull and McDonough, 1994). The higher physical activity of group-reared calves seems to be the only possible reason for the increased erythropoiesis in our trial, since no extrafeed iron was available; in fact, the pens were made only of wood and stainless steel and no straw litter was present. A similar reduction in anaemia produced by increasing movement was found by Reece and Hotchkiss (1987) in calves reared in individual stalls without tethers and by Andrighetto et al. (1999) in calves reared in group pens. On the other

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hand, Terosky et al. (1997) failed to observe any effect of the housing system on blood variables when veal calves were reared in stalls with tethers or in pens of various size. As regards slaughter data, carcass colour was not affected by the housing system despite the differences measured in haematocrit, which is generally considered closely linked to colour traits (Wilson et al., 1995; Klont et al., 1999). Andrighetto et al. (1999) recorded a better conformation but a darker colour in carcasses of calves reared in groups compared to calves kept individually, while according to Terosky et al. (1997) neither the housing system nor the stall size modified carcass colour. The physical and sensory characteristics of the meat were only slightly influenced by the housing system. The most important quality trait of veal, i.e. colour, was similar in the two experimental groups, as observed for carcasses. Meat from group-reared calves showed higher shear resistance, despite the fact that tenderness and other sensory traits were not affected. A similar increase of shear press force was observed by Vestergaard et al. (2000) in the meat of young free-range bulls compared to bulls kept in stalls with tethers and fed a concentrate-based diet. This result was ascribed partly to the higher physical activity and partly to the different feeding level. In fact, the negative correlation between carcass fatness and meat collagen reported by Wood (1990) might also account for the possible increase of shear resistance in leaner meat. Other authors did not report any change of shear press force in the meat of young bulls housed in pens with increased floor space (Andersen et al., 1997). Andrighetto et al. (1999), however, reported a negative effect of group housing on meat colour of veal calves, while shear force and sensory toughness ´ were reduced, as observed in other species (EssenGustavsson et al., 1988; Aalhus et al., 1991). Rearing calves in pens rather than in individual stalls modified meat chemical composition with decreasing concentrations of ether extract and gross energy, as for the fat proportion of the sample joint. The higher movement likely stimulated muscle development at the expense of fat deposition, as observed by others (Andrighetto et al., 1999). Concerning the FA profile, no reference is available on the specific effect of the housing systems on

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veal. In the present trial, FA proportions changed according to the degree of fatness, with a higher relative concentration of polyunsaturated FA in the leaner meat of group-reared calves. In ruminants, an opposite trend is generally described with an increase of unsaturation degree in excessively fat animals, while in monogastric species the leaner the carcasses, the higher the incidence of unsaturated FA in meat lipids, due to the greater incidence of cell membrane lipids compared to depot fat (Wood, 1990; Xiccato, 1998).

4.2. Effect of maize grain supplementation Among the various solid feeds suitable for veal calf feeding, maize grain was chosen firstly on the basis of its wide availability in most of the countries involved in veal production. Moreover, its low iron concentration, constant chemical composition and high nutritive value were considered favourable for preserving the growth performance of calves and, overall, the pale colour of meat. The favourable effect of maize grain supplementation on growth performance was more pronounced than the effect of the housing system. This clearly depended on the higher energy ingestion provided by maize grain and was evident even during early growth. Also Morisse et al. (2000) described higher growth rates when milk was supplemented with cereals, partly due to the extra energy and protein intake, partly due to the extra iron intake. The same improvement in growth performance was recorded both by Beauchemin et al. (1990) and Pommier et al. (1995), when comparing calves fed exclusively milk ¨ and replacer or fed cereal grains, and by Bergstrom Dijkstra (1991), when maize silage or silage / concentrate mixture were added or partially substituted milk diets. Maize supplementation increased carcass weight without changing dressing percentage. This result likely depended on the amount of solid feed supplementation. When milk was only partially substituted (20%) by concentrates and maize silage, no changes ¨ in dressing percentage were observed (Bergstrom and Dijkstra, 1991). The substitution of 30% milk replacer with maize grains (Quilichiny, 1989) or the

complete substitution with a solid concentrate decreased dressing percentage, due to the development of the reticulo-rumen (Beauchemin et al., 1990); Pommier et al., 1995). Some authors reported the impairment of carcass and meat colour when cereal grains and protein concentrates were used to substitute milk diets either partially or completely (Quilichiny, 1989; Beauch¨ and Dijkstra, 1991). emin et al., 1990; Bergstrom The effect of solid feeding on carcass and meat colour depends on the feed type and composition (i.e. iron concentration and availability) and may vary largely according to the quantity ingested ´ et al., 1998). In the (Pommier et al., 1995; Gariepy present study, despite the administration of maize increasing the iron intake by 34%, meat colour was not impaired. In the present trial, sensorial properties of meat were not influenced by the supplementation with ¨ and Dijkstra maize grain, as observed by Bergstrom (1991). According to Quilichiny (1989), the meat of maize-fed calves was more tender and acceptable than that of milk-fed calves, without differences in juiciness and flavour. As described above, FA proportions changed according to the degree of fatness, with a lower relative concentration of polyunsaturated FA in the maize-fed calves.

5. Conclusions The results of this study suggest that rearing veal calves in groups and supplementing the milk diet with maize grain do not impair carcass and meat quality. The rearing of veal calves in group pens without tethers stimulated the growth rate while also increasing social relationships, without affecting the colour of carcass and meat. Supplementation with cereals provided a higher energy intake and, therefore, stimulated growth performance without affecting carcass and meat colour due to the low iron concentration of maize grain. However, in order to enable veal calves to fully express their ruminant nature as required by EU animal welfare laws, supplementation with solid feed containing higher

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fibre concentration might be necessary. In this respect, suitable fibre sources for veal calf production have to be investigated.

Acknowledgements This research was supported by Reg. UE 2052 / 88, ob. 5b.

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