The influence of level of feeding and live weight on feed conversion and carcass composition in Friesian bulls

Livestock Production Science, 37 ( 1993 ) 53- 67

53

Elsevier Science Publishers B.V., Amsterdam

The influence of level of feeding and live weight on feed conversion and carcass composition in Friesian bulls Kjell Martinsson and Ingemar Olsson Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Uppsala, Sweden (Accepted 23 March 1993)

ABSTRACT Feed conversion and carcass quality in relation to feeding level were investigated using 75 bulls of the Swedish Friesian breed. The experiment was carried out using a factorial design with three feeding levels (H, L and F) and three slaughter stages. The bulls were fed concentrate and hay to gain 1100 g/day (H) or 850 g/day (L). The third group (F) was fed to gain 850 g/day until 18 months of age and 1100 g/day thereafter. On each feeding level the bulls were slaughtered at three different ages (H: 13, 18 and 23 months; L and F: 18, 23 and 28 months) and when reaching treatment mean carcass weights of 240, 325, 418, 277, 363,422, 275, 372 and 454 kg, respectively. The relative amounts of fat, lean and bone were strongly affected by both feeding level and age or weight. The carcasses became fatter and the relative weight of the bone decreased as the carcasses grew heavier and as feeding level increased. The feed conversion ratio to the same degree of fatness, expressed as metabolizable energy consumed per kg carcass weight gain, was similar irrespective of feeding level. The conversion of feed into live weight and carcass weight gains increased sharply with increasing live weight. Key words: Growing bull; Feeding level; Feed conversion; Carcass composition

INTRODUCTION

The decreasing number of dairy cows has led to a reduced number of bull calves available for beef production. In order to maintain the total amount of beef produced, a decreasing number of calves can partly be compensated for by an increased weight at slaughter. However, it is necessary to know how live weight (LW) at slaughter affects carcass composition and feed conversion ratio (FCR) at different feeding levels. Almost all experimental results in the literature are in agreement that FCR increases with increasing slaughter weight. Most energy standards presume decreasing energy requirements per unit gain with increasing daily gain (Norrman, 1977; Agricultural Research Correspondence to." Kjell Martinsson, Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Box 7024, S-750 07 Uppsala, Sweden.

0301-6226/93/$06.00 © 1993 Elsevier Science Publishers B.V. All rights reserved.

54

K. MARTINSSON AND I. OLSSON

Council, 1980; Geay and Micol, 1989). However, many feeding experiments showed the lowest FCR when the feeding level was moderate (De Boer et al., 1971; Levy et al., 1974; Andersen, 1975; Andersen et al., 1983). Additional improvement in efficiency and market acceptability may thus be achieved by altering feeding levels and the degree of maturity of animals at slaughter (Andersen, 1975; Webster, 1980; Andersen et al., 1983 ). Furthermore, it has been indicated that differences in FCR due to feeding level can vary according to breed (Geay et al., 1976; Langholz, 1977). The literature does not appear to include an investigation where the effect of increasing LW and feeding level on FCR and carcass composition has been studied at constant daily gains and at the same ME content per kg DM of the feed independent of feeding level, thereby mimicing the way in which requirements usually are expressed. The objective of the present study was to investigate and quantify the effects of daily gain and weight at slaughter on feed conversion and carcass quality in bulls. Additionally, the effect of an increased feeding level during the last months before slaughter was examined. In order to eliminate differences in ME utilization and interaction between ration and feed intake capacity, the ME content per kg DM of the feed and the daily gains were kept constant throughout the whole experimental period. MATERIAL AND METHODS

Experimental design and animals The experiment was designed as a factorial experiment with three feeding levels and three slaughter stages (Table 1 ). Feeding levels were determined to maintain a constant daily live weight gain (LWG) from start until slaughter. The LWGs intended were 1100 g/day (H) and 850 g/day (L). In addition, a third group (F) was fed to gain 850 g/day until 18 months of age and 1100 g/day thereafter. On each feeding level, the bulls were slaughtered at three different ages. Seventy-five bull calves of the Swedish Friesian breed were purchased at an average age of 4 weeks and were equally fed up to the start of the experiment at approximately 5 months of age. The calves were randomly allotted to feeding levels. Before the first slaughter point for each feeding level, the bulls were divided into three growth-classes (high, medium, low) according to the daily gain from the start up to that time in order to ascertain a similar level and variation in growth capacity for bulls slaughtered at all stages. Within feeding level and growth.classes, the bulls were randomly allotted to slaughter stages. During the entire experimental period the bulls were tied up and individually fed in a large well-ventilated and heated test barn. The bulls were weighed every second week. LW at start was calculated as the average of weighings performed one week before start, at start and one week after start. Live weight at slaughter was defined as the average of two weighings made on the two days preceding the actual day of slaughter.

FEED CONVERSIONAND CARCASSCOMPOSITION

55

TABLE 1 Experimental design (number of animals per treatment, days on experiment and age at slaughter) Feeding level

High (H) Number of animals Age at slaughter (months) Days on experiment Low (L) Number of animals Age at slaughter (months) Days on experiment Low/Finishing (F) c Number of animals Age at slaughter (months) Days on experiment

Slaughter stage Early

Medium

Late

9 13 274

9 18 394

9 23 555

6 18 394

9a 23 555

9b 28 701

6 18 394

9 23 555

9 28 701

"Two of these bulls were excluded from the analyses (see text). bOne of these bulls was excluded from the analyses (see text). CLow (L) until 18 months of age - subsequently high (H).

Feeds and feeding The bulls were fed hay and concentrate twice daily. Refusals were removed daily and recorded. The daily amounts of hay and concentrate were the same for all bulls within each feeding level and were adjusted weekly to maintain the desired average LWG for the feeding level. The density of metabolizable energy (ME) of the ration was the same on all feeding levels, but it was allowed to vary with time between 10.5 and 11.3 MJ (kg D M ) -1 depending on the actual ME density of the hay. The target concentrate:hay ratio was 30:70 on a ME base. However, the a m o u n t of hay was allowed to vary between 60 and 80% in order to compensate for differences in ME density of the hay. The concentrate was based on equal amounts of roiled barley and oats and 10% dried molassed sugar-beet pulp, and was supplemented with soyabean meal to meet the requirements for digestible crude protein (DCP) (Norrman, 1977). As the DCP content of the total ration was adjusted according to feeding standards, the percentage of soyabean meal varied from 0 to ~30% depending on the D C P content of the hay. The bulls had free access to mineralized sodium chloride and were fed a commercial mineral supplement and an A-D-E vitamin c o m p o u n d to meet the Swedish recommendations (Norrman, 1977).

Sampling and chemical analysis of feeds Samples of concentrate and hay were taken at every feeding and pooled for periods of two weeks. The components of the concentrate mixture were sam-

56

K~MARTINSSONAND I. OLSSON

pied before mixing and analysed conventionally. ME in the concentrate was calculated from ingredient values according to Axelsson ( 1941 ), using digestibility coefficients according to Eriksson et al. (1976), and adjusted to the DM content of samples at feeding. ME in hay was calculated from in vitro digestibility (Lindgren, 1979). The nutrient content of feeds is presented in Table 2.

Slaughter and carcass assessment The animals were slaughtered according to the industrial routines used in Sweden. During slaughter the weights of the kidney knob and channel fat, omentum and mesenteric fat were recorded, and the sum of these recordings is referred to as fat in the abdominal cavity. Cold carcass weight (CW) was estimated as 98% of hot weight. The weight of the carcass at the beginning of the experiment was estimated as 0.5*LW at start. After cooling, the right sides of the carcasses were cut with a knife to get an estimate of lean meat, fat, tendons and bone. The small muscles along the vertebral column and intercostal muscles together with adhering intermuscular fat were collected and weighed separately. This mixture of muscles and fat was standardised to 15% visible fat in a subjective way, by adding or subtracting fat. The total amount of lean meat was then calculated as the sum of lean meat and 85% of the mixture. In the same way, the total amount of fatty tissue was the sum of dissected fat and 15% of the mixture. Statistical analysis The animal production data were analysed as a 3 × 3 × 3 factorial randomized design. The statistical analyses were performed by using the GLM-procedure described by SAS ( 1985 ). The performance and carcass quality traits TABLE 2 Average crude protein (CP) and metabolizable energy (ME) content of concentrate and hay during different periods of the experiment Experimental period (weeks)

Concentrate

Hay

175.0 130.0 114.0 113.0

116.0 119.0 123.0 123.0

12.9 12.7 12.7 12.7

10.2 10.4 10.8 11.6

CP (g (kg DM)-~) start-35 36-56 57-79 80-100

ME (MJ (kg DM)-9 start-35 36-56 57-79 80-100

FEEDCONVERSIONANDCARCASSCOMPOSITION

57

were described by the following model:

Yiju =/t+FLi +Sj + FL*S~+ Gk +eijk~

(I)

FLi is the effect of feeding level, Sj the effect of slaughter-stage, Gk the effect of growth-class and eijk~the random error. The experimental design also allowed the use of covariance analyses to study feed conversion adjusted to the covariate mean of fatty tissue ( 13.2% ) by the following model, where fl is the effect of fatty tissue (Zijk) : Vij~a =/Aq- F L i + S j

+ FL*Sj +Gk "[" ~*Zijkl + e i j m

(II)

Data presented as least squares means (LSM) refer to these models. Although the growth-class effect is included in the model, this effect is not discussed further in the present context. The least significant difference (LSD) at the 5% level is presented in the Tables. In some cases, LSD has been presented as a range as there were unequal numbers of observations in each treatment combination. The changes in carcass composition that occurred during growth were described by an allometric function: Yi = a * x a TABLE 3

Daily live weight gain (LWG), carcass weight gain (CWG) and ME intake. Least squares means and least significant difference (LSD). Model I Daily gain (g)

Main effects Feeding level (FL) H L F Slaughter stage (T) Tl T2 T3 LSD Interaction (FL X T) H×TI HXTz HXT3 LXTt L X T2 LxT3 FXT1 F × T2 FXT3 LSD FLXT

Daily ME intake (MJ)

LWG

CWG

1098 872 925

581 472 494

91.7 75.4 79.9

969 970 956 30

505 523 519 18

70.7 82.2 94.2 0.9

1143 1099 1052 867 890 860 898 922 955 48-59 P<0.01

579 587 576 464 483 469 471 499 513 28-35 P=0.27

78.7 91.2 105.3 66.9 75.1 84.3 66.6 80.2 92.0 1.4-1.8 P<0.02

58

K. MARTINSSON AND I. OLSSON

where Yi is the estimated value o f lean, fatty tissue or carcass bone at feeding l e v e l ( i ) , ai is the effect of/t*FLi as defined below, X is the carcass weight and Daily

LWG (g)

.... ........

k

I000'

•

.... \

..I~.

~

_i ~

~

500 -

I Daily

ME intake

i

I

I

i

~-~

(M J)

150

Tatal feed

~.

J/~"

intake

100

50'

Concentrate

.....

f

/

.................

2

intake

._.~.

t

I

I

I

I

20

40

60

80

100

Weeks

L~

in e x p e r i m e n t

Fig. 1. Daily gain and daily intake of metabolizable energy (ME) at different weeks on e x p e r i m e n t for feeding levels H ( - - ) , L (--) and F ( . . . . ). FCR (MJ(kg LWG) -I)

FCR (MJ(kg LWG) -I)

160 120 10080-

"" /--,7"-

~

140-

160.

.../.. '

f~

/i ' ' .t

140 -

" /

120

'

-

100-

f

80-

60-

60-

40-

40-

20-

20-

20

40 Weeks

60

80

in e x p e r i m e n t

100

200

400

600

800

LW(kg)

Fig. 2. Feed conversion ratio at different weeks on experiment and at different live weights (LW) for the feeding levels H ( - - ) , L (--) and F ( .... ).

FEEDCONVERSIONANDCARCASSCOMPOSITION

59

8 is the growth coefficient. The parameters were estimated according to the following linear model: log Yij = log/~ 4- log FLi 4- 6*log Xij + log eij

(III)

where log Yij is the weight (log) of lean, fatty tissue or carcass bone, log F L i is the effect of treatment (log), log Xij the carcass weight transformed to log and ~ the growth coefficient.

TABLE 4 Live weight (LW) at slaughter, carcass weight (CW) and total ME intake. Least squares means and least significant difference (LSD). Model I

Weight at slaughter (kg)

Total ME intake (MJ*103)

LW

CW

626 668 697

328 354 367

37.9 42.3 45.3

513 669 810 17-18

264 353 431 11

24.0 40.7 60.9 0.6

476 621 781 530 683 791 533 702 857 29-35 P < 0.03

240 325 418 277 363 422 275 372 454 18-22 P < 0.04

19.4 35.9 58.5 26.4 41.5 59.1 26.2 44.5 65.3 0.9-1.1 P < 0.01

Main effects

Feeding level (FL) H L F Slaughter stage (T) Tl T2 T3 LSD

Interaction (FL × T) H × T~ HXT2 HXT 3 L×T1 LXT2 LXT 3 F×TI FXT2 FXT3 LSD FL× T

60

K. MARTINSSONAND I. OLSSON

RESULTS

Health of the animals During the experimental period a total of three bulls on treatment L had to be slaughtered in advance. In two cases the cause of culling was foot-rot. The third bull had to be slaughtered because of its bad temper. All data relating to those bulls were removed from the analyses.

Live weight and daily gain The average weights of the bulls at start were 192.9, 190.3 and 186.3 in feeding levels H, L and F, respectively, and the average number of days on experiment is shown in Table 1. The daily gains in LW and CW are reported in Table 3 and the daily LWGs during shorter periods of the experiment are presented in Fig. 1. Daily LWGs were in accordance with planned levels and consequently LW at slaughter and CW were affected by treatments (Table 4).

Feeds and feed consumption The daily ME intake during different periods of the experiment is preTABLE5

Feed conversion. Least squares means and least significant difference (LSD). Model I and Model II Feed conversion (II)

Feed conversion (I) MJ (kg LWG) - 1

MJ (kg C W G ) -1

MJ (kg LWG) - l

MJ (kg CWG) -1

84.3 86.9 86.4

158.9 160.4 161.7

84.2 87.4 86.5

158.3 161.7 161.9

73.7 85.1 98.8 2.5-2.6

141.1 157.8 182.0 5.0-5.4

75.4 85.3 97.3 2.4-2.7

145.9 158.4 177.7 5.1-5.7

69.4 83.3 100.3 77.5 84.7 98.5 74.2 87.3 97.6 4.0-4.9 P<0.01

137.0 156.2 183.4 144.6 155.7 180.8 141.6 161.4 182.0 8.4-10.3 P=0.41

70.9 83.4 98.2 79.4 85.2 97.6 75.8 87.4 96.2 4.0-5.6 P=0.02

141.3 156.5 177.3 150.1 157.0 178.1 146.2 161.8 177.8 8.3-14.3 P=0.56

Main effects Feeding level (FL) H L F Slaughter stage (T) Tt T2 T3 LSD

Interaction (FL × T) H×T~ HXTz H)
FEED CONVERSION AND CARCASSCOMPOSITION

61

sented in Fig. 1 (MJ ME/day). On average concentrate ME was 31% of total ME intake, and ranged from 24 to 41% depending on the energy density of the hay. During the main part of the experiment it was thus possible to maintain a ME density in the total ration of about 11 MJ (kg D M ) -1. The total ME intake during the experiment is presented in Table 4, while average daily ME intake is presented in Table 3. It should be noted that by design the bulls on level H spent a shorter time in the test than the bulls on the other treatments. There was a significant interaction of feeding level and slaughter stage on both total and daily ME intake. Feed conversion Marginal FCR calculated as MJ (kg L W G ) - 1 increased sharply with increasing weeks on experiment and increasing LW (Fig. 2 ). Feeding level exerted a significant influence on FCR for the whole experiment (Table 5 ). Bulls on feeding level H had better FCR ( P < 0 . 0 5 ) than bulls on level L. However, because of significant differences in dressing-out percentage ( P < 0.05 ) there were no significant differences in FCR when related to carcass weight gain (CWG). This was even more pronounced when comparing TABLE 6

Fat in abdominal cavity, lean, fatty tissue and bone. Least squares means and least significant difference (LSD). Model I Fat in abdominal cavity

Carcass composition (%)

(% of CW)

Lean

Fatty tissue

Bone

68.4 69.6 68.9

13.7 12.0 13.0

16.1 16.6 16.2

4.9 7.5 11.2 0.8-0.9

71.6 69.4 65.8 0.9-1.1

8.9 12.6 17.0 0.8-0.9

17.7 16.0 15.1 0.6

5.1 8.8 11.9 4.8 6.4 9.7 4.9 7.4 11.9 1.4-1.7 P=0.17

71.3 68.9 64.9 72.3 70.0 66.3 71.1 69.3 66.2 1.3-1.8 P=0.67

9.4 13.0 18.6 8.3 12.0 15.6 9.1 12.9 16.9 1.5-1.8 P=0.20

17.5 16.2 14.6 17.8 15.9 15.9 17.8 16.0 14.9 0.8-1.0 P=0.19

Main effects Feeding level (FL) H L F

8.6 7.0 8.1

Slaughter stage (T) Tl T2 T3 LSD

Interaction (FL X T) HXT~ HXT/ H×T3 LXT~ L×Tz L×T3 F×T~ FXT2 FXT3 LSD FLXT

62

K. MARTINSSON AND I. OLSSON

FCR at the same content of fatty tissue in the carcass (Model II). There was no significant interaction of feeding level and slaughter stage on FCR. Slaughter and carcass assessment The amounts of fat in the abdominal cavity and the relative amounts of fat and bone in the carcass were strongly affected by both feeding level and slaughter stage (Table 6). Bulls on level L had less fatty tissue ( P < 0.05 ) and also less fat in the abdominal cavity ( P < 0.05 ) calculated as a percentage of CW. The carcass quality characteristics for bulls in the F group were not significantly different from those of bulls fed on the H level. The relative contents of lean, fatty tissue and bone in the carcass (Fig. 3 ) were calculated from the parameters in Table 7. As there were no significant interactions between feeding level (log) and the growth coefficient, the same growth coefficient was used irrespective of feeding level. Lean, ~of CW 76747270686664" 62 I

I

I

I

I

I

I

I

I

I

I

I

Fat, ~ of CW 20

18 16 14 12 10

8 6

Bone, ~ of CW 20

18 16 14 12 2O0

I

I

I

I

I

I

250

300

350

400

450

500

CW, kg

Fig. 3. Percentage of lean, fatty tissue and bone at different carcass weights (CW) for the feeding levels H ( - - ) , L ( - - ) a n d F ( .... ).

FEED CONVERSION AND CARCASSCOMPOSITION

63

TABLE 7 Parameter estimates from the allometric relationships (Model III) for lean, fatty tissue and bone (Y) on carcass weight ( X ) Feeding level (FL)

Lean

Fatty tissue

a

~

sea

aX104

8

sea

a

~

sea

H L F

1.589 1.634 1.629

0.854 i.d. i.d.

0.016 i.d. i.d.

1.524 1.222 1.263

2.172 i.d. i.d.

0.082 i.d. i.d.

1.070 1.137 1.121

0.671 i.d. i.d.

0.029 i.d. i.d.

Test for differences between feeding levels: P<0.001 P<0.001

Bone

P<0.001

i.d. = identical to above value. DISCUSSION

Daily growth rate, feed conversion, carcass weight and fat deposition at slaughter are deciding factors in the economics of beef production. A thorough knowledge of the role of these factors in achieving optimum production is of fundamental importance because they can be largely controlled by the producer.

Growth In the present investigation, growth rates were determined by the experimental design. As a whole, the intended growth rates were maintained throughout the experiment. However, the difficulties in maintaining a constant daily gain are illustrated in Fig. 1. Reduced daily gain retarded the gain of fatty tissue relatively more than that of bone. This agrees with the wellestablished growth theory indicating that bone and muscle have higher priority than fat (P~ilsson, 1955 ). The daily LWGs recorded in this study were compared with predicted values derived from the actual ME intakes and the Swedish feeding standards (Norrman, 1977 ). Predicted values were in good agreement with the results on feeding level H, while predicted LWG for feeding levels L and F were about 5% lower than recorded in this study.

Carcass quality Consumers in Sweden prefer carcasses with a relative content of about 12% fatty tissue. This is an important consideration when trying to improve market acceptability. Effect of feeding level The relative contents of fatty tissue, lean and bone in the carcass at a given weight were strongly affected by feeding level. These results support previous research (Geay and Robelin, 1979; Robelin and Daenicke, 1980) reporting that the proportion of fat in the carcass increased

64

K. MARTINSSON AND I. OLSSON

with higher energy intake. Also, in agreement with Robelin and Daenicke (1980), it could be concluded that at higher slaughter weights the fat percentage increases more rapidly with increasing feeding level than at lower slaughter weights. Effect of weight at slaughter. The differential growth of lean, fat and bone causes carcass composition to change with the weight at slaughter. Accordingly, the fat content increased substantially while the relative content of bone decreased as weight at slaughter increased. Corresponding growth patterns were found in earlier experiments with serial slaughter (Andersen, 1975; Liboriussen et al., 1982; Andersen et al., 1983).

Feed conversion Effect offeeding level. FCR calculated as MJ (kg LWG ) -1 was significantly higher on the low level of feeding than on the high level, on both unadjusted and fatty tissue adjusted bases. When calculating FCR as MJ (kg CWG)there were, however, no significant differences, because of differences in dressing-out percentage. From the present experiment it could be concluded that in the range of daily LWG investigated (850 g-1100 g) there were no differences in the conversion of food into carcass gain. This is a wider range of unchanged FCR than proposed by Andersen (1975 ) and Andersen et al. (1983). Data relating to the effects of feeding level on the energetic efficiency of cattle are less easy to interpret (Andersen, 1975; Geay and Robelin, 1979). Differences between experiments in type and amount of feed and stage of development may account for part of the apparent disparity in results. For example, Rompala et al. (1984) reported better FCR at increased growth rate of Charolais cross steers slaughtered at the same degree of finish. A consistent finding in the experiments presented by Andersen (1975 ), Andersen et al. (1983) and Bailey et al. (1985) is that growing cattle perform more efficiently when fed at moderate levels compared with ad lib. feeding on high energy diets. Geay et al. (1976) and Langholz (1977) reported that differences in FCR due to feeding level can vary according to breed. Studies evaluating energy partitioning into fat and lean growth (van Es, 1977; Rohr and Daenicke, 1984) have shown that fat growth is more expensive to produce than lean growth. Unless animals are compared at the same body composition, FCR is likely to be superior for animals having the leanest carcasses. Consequently, comparing at a certain degree of fatness is supposed to give the most accurate answer concerning FCR as affected by feeding level. FCR for the whole experimental period was not significantly different for bulls on feeding level F compared to bulls on feeding level L. FCR was also similar for bulls on feeding levels H and L compared at the same LW (Fig. 2). During the finishing period, there was a tendency for lower FCR, at the

FEED CONVERSION AND CARCASS COMPOSITION

65

s a m e LW, for bulls o n f e e d i n g level F, t h u s s h o w i n g e v i d e n c e o f c o m p e n s a t o r y growth. Effect of weight at slaughter As a result o f a h i g h e r m a i n t e n a n c e r e q u i r e m e n t a n d a c h a n g e in the tissue c o m p o s i t i o n , the F C R increases strongly with increasing weight. T h i s is in a g r e e m e n t with a l m o s t all e x p e r i m e n t s r e p o r t e d in the literature. ACKNOWLEDGEMENT T h e a u t h o r s are grateful to the s t a f f at the D i v i s i o n o f M e a t Science o f the D e p a r t m e n t o f F o o d Science for t h e i r help with the carcass e v a l u a t i o n .

REFERENCES Agricultural Research Council, 1980. The Nutrient Requirements of Ruminant Livestock. Farnham Royal: Commonwealth Agricultural Bureaux. Andersen, H.R., 1975. The influence of slaughter weight and level of feeding on growth rate, feed conversion and carcass composition of bulls. Livest. Prod. Sci., 2:341-355. Andersen, H.R., Ingvartsen, K.L., Kousgaard, K. and Klastrup, S., 1983. Influence of energy level, weight at slaughter and sex on growth, feed conversion, carcass composition and meat quality in cattle. (With English summary and subtitles.) 544. Report from the National Institute of Animal Science, Copenhagen, 145 pp. Axelsson, J., 1941. Der Gehalt des Futters an urnsetzbarer Energie. ZiJchtungsk., 16: 335-347. Bailey, C.M., Liboriussen, T., Andersen, H.R. and Andersen, B.B., 1985. Producing beef from intact male progeny of Holstein sires: feed efficiency and compositional characters. J. Anita. Sci., 61: 27-35. De Boer, F., Smiths, B. and Dijkstra, K.T.J., 1971. Voederhoeveelheid, groei en slachtkwaliteit bij j onge vlesstieren (Feeding level, daily gain and carcass-quality in fattening young bulls). Landbouwkundig Tijdschrift, Dijkstra-nummer, 354-359. Eriksson, S., Sanne, S. and Thomke, S., 1976. Fodermedelstabeller och utfodringsrekommendationer till idisslare, h~istar och svin. LT: s f'orlag, Stockholm. Geay, Y., Robelin, J. and Beranger, C., 1976. Influence du niveau alimentaire sur le gain de poids vif et la composition de la carcasse de taurillons de differentes races. Ann. Zootech., 25: 287-298. Geay, Y. and Robelin, J., 1979. Variation of meat production capacity in cattle due to genotype and level of feeding: genotype-nutrition interaction. Livest. Prod. Sci., 6: 263-276. Geay, Y and Micol, D., 1989. Growing and finishing cattle. In: R. Jarrige (Editor), Ruminant nutrition, recommended allowances and feed tables, Paris: INRA, 121-151. Langholz, H.J., 1977. Interaction between growth potential and feeding level in beef production. In: I. Mason and W. Pabst (Editors), Cross Breeding Experiments and Strategy of Beef Utilization to Increase Beef Production, The Commission of the European Communities, United Kingdom, pp. 445-463. Levy, D., Holzer, Z., Neumark, H. and Amir, S., 1974. The effects of dietary energy content and level of feeding on the growth of Israeli Friesian intact male cattle. Anim. Prod., 18:67-73. Liboriussen, T., Lauritzen, F., Andersen, B.B., Buchter, L., Klastrup, S., Kousgaard, K. and Sorensen, S.E., 1982. Krydsningsog produktionsforsok med europ~eiske kodracer I og II. 527. beretning. Statens Husdyrbrugsforsog, Kopenhavn, 65 pp. Lindgren, E., 1979. The nutritional value of roughages determined in vivo and by laboratory

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methods. (Swedish University o f Agricultural Sciences, Department of Animal Nutrition, Report 45 ). Uppsala. Norrman, E., 1977. In: A. Helmenius (Editor), N~Stk6tt, produktion och ekonomi. LT: s f'6rlag,Stockholm. P~llsson, H., 1955. Conformation and body composition. In: John Hammond (Editor), Progress in the Physiology of Farm Animals. Butterworths, London, pp. 430-542. Robelin, J. and Daenicke, R., 1980. Variations of net requirements for cattle growth with liveweight, liveweight gain, breed and sex. Ann. Zootech., 29: 99-104. Rohr, K. and Daenike, R., 1984. Nutritional effects on the distribution of live weights as gastrointestinal tract fill and tissue components in growing cattle. J. Anim. Sci., 58:753-761. Rompala R.E., Jones S.D.M., Buchanan-Smith J.G., Wilton J.W. and Burton J.H., 1984. Growth and carcass characteristics of latefattening steers on different feeding systems. Can. J. Anim. Sci., 64:313-322. SAS., 1985. SAS User's Guide: Statistics, Version 5 Edition. Car/, NC, USA: SAS Institute Inc. van Es A.J.H., 1977. The energetics of fat deposition during growth. Nutr. Metab. 21: 89-93. Webster, A.J.F., 1980. The energetic efficiency of growth. Livest. Prod. Sci., 7:243-251. RESUME Martinsson, K. et Olsson, I., 1993. Influence du niveau alimentaire et du poids vif sur refficacit6 alimentaire et la composition de la caracsse chez le taurillon de la race frisonne. Livest. Prod. Sci., 37: 53-67(en anglais). Lc rapport entre l'efficacit6alimcntaire ct la qualit6 de la carcasse, d'une part, et ic niveau alimcntairc, d'autrc part, a 6td dtudid dans unc cxpdricncc cffectudc sur 75 taurillons dc la race frisonne suddoisc. L'cxpdricncc a dtd rdalisdc suivant un dispositiffactoriel,avcc trois niveaux alimcntaircs (H, Let F) ct trois ages d'abattage. O n distribuaitaux taurillons des aliments concentr6s et du loin cn vuc dc faire augmenter leur poids de i I00 g/jour (H) ou de 850 g/jour (L). Lcs tauriUons du troisibmc groupc (F) ont dt6 alimcntds dc mani6rc/l obtenir un gain de poids dc 850 g/jour jusqu'/i l'~gede 18 mois ct,cnsuitc,dc I 100 g/jour. A chaquc nivcau alimentairc, Ics taurillonsont 6t6 abattus trois ages diff6rcnts (H: ~tl'agcdc 13, dc 18 ct dc 23 tools;Let F: ~ rage dc 18, de 23 et dc 28 mois), Ics poids dc carcassc moycns atteintspour Ics diffdrentsrdgimes dtant dc 240, 325, 418,277,363, 422, 275,372 ct 454 kg respectivement. Il cst apparu que tant Ic niveau alimcntairc quc rage ou Ic poids avaicnt unc influcncc importantc sur les quantitds relatives dc d6p6ts adipcux, dc muscles ct d'os. Les carcasses 6talent plus grasses et Ic poids relatifdes os diminuait,/t mesure quc Ics carcasses devcnaicnt plus lourdes et quc le nivcau alimcntairc augmcntait. L'efficacitdalimcntairc au m ~ m c degrd d'cngraissement cxprimdc cn quantitd, d'dncrgic mdtabolisable consommde par kg d'augmcntation du poids dc la carcassc 6tait idcntiquc pour Ics trois nivcaux alimcntaircs. L'efficacit6alimcntairc augmcntait radicalcmcnt avec Ic gain dc poids vif.

KURZFASSUNG Martinsson, K. und Olsson, I., 1993. EInfluB des FiJtterungs- und des Gewichtsniveaus auf die Futterverwertung und die SchlachtkSrperzusammensetzung yon Friesian Bullen. Livest. Prod. Sci., 37:53-67 (aufenglisch). Futterverwertung und Schlachtk6rperqualitiit im Verh~iltnis zum Fiitterungsniveau wurde bei 75 Bullen der schwedisch-friesischen Rasse untersucht. Das Experiment wurde als eine faktorielle Anlage mit drei Fiitterungsniveaus (H, L u n d F) und drei Schlachtzeitpunkten durchgef'tihrt. Die Bullen wurden mit Kraftfutter und Heu ffir eine Gewichtszunahme von 1.100 g/Tag (H) oder 850 g/Tag (L) gef'tittert. Die dritte Gruppe (F) wurde bis zu ihrem 18. Lebensmonat for eine G-ewichtszunahme yon 850 g/Tag gefiittert, und danach f'tir 1.100 g/Tag. Beijedem Fiitterungsniveau wurden die Bullen

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in drei verschiedenen Altern geschlachtet (H: 13, 18 und 23 Monate, Lund F: 18, 23 und 28 Monate) und nach dem Erreichen durchschnittlicher Schlachtgewichte von 240, 325, 418, 277, 363, 422, 275, 372, und 454 kg. Die relativen Mengen an Fett, Magerfleisch und Knochen wurden stark durch das Fiitterungsniveau und das Alter oder das Gewicht beeinfluflt. Die K~rper wurden fetter und das relative Knochengewicht sank, als die K6rper schwerer wurden. Die Futterverwertung im Verh~iltniszum gleichen Fettansatz, be rechnet als konsumierte umsetzbaren Energie je kg Gewichtszunahmewar, unabhangigvon dem Fiitterungsniveau, ~ihnlich. Der Grenzwert der Futterverwertungsrate stieg mit steigender Lebendmasse stark an.