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Food Intake Regulation in Pigs. III. Voluntary Food Selection Between Protein-Free and Protein-Rich Diets
Br. uet.
J.
(1974),130,522
FOOD INTAKE REGULATION IN PIGS. III. VOLUNTARY FOOD SELECTION BETWEEN PROTEIN-FREE AND PROTEIN-RICH DIETS By D. \V.
ROBINSON
Department of Animal Science, University of California, Davis 95616 SUMMARY
Six Duroc gilts weighing 45 kg were housed individually in a temperature controlled room. They were offered two isocaloric semipurified diets; one protein-free diet (PF) was constantly available throughout the seven-week experimental period. In successive weeks the gilts were provided with alternative diets of increasing levels of casein fortified with 0'2 per cent DL-methionine (CM) at the percentage levels of 20 (CM20), 30 (CM30), 40 (CM40), 50 (CM50), 60 (CM60), 70 (CM70), 80 (CM80). The voluntary consumption for each diet expressed as a percentage of the average total intake for the respective diets was Week I, PF 16: CM20 84; Week 2, PF 28: CM30 72; Week 3, PF 29: CM40 71; Week 4, PF 37: CM50 63; Week 5, PF 33: CM60 67; Week 6, PF71: CM70 29; Week 7, PF 77: CM80 23· The mean protein concentration reached 70 per cent before the diet with protein would be rejected for one devoid of protein, although individual variation between pigs was considerable. INTRODUCTION
Protein-free diets have been used in free choice studies with the pig to assess the preference between amino acid deficient, adequate or protein-free diets (Jackson, Robinson & Khalaf 1970; Devilat, Pond & Miller, 1970). It has been shown that protein-free diets are rejected by the growing pigs in favour of well-balanced diets but preferred to a degree over amino acid deficient or imbalanced diets, as indeed they are also in the rat (Leung, Rogers & Harper, 1969). No work has been reported however on the effect of protein level per se on the choice made by pigs between a protein-free diet and one with a high concentration of protein. As the protein level itself may influence the choice made, the object of the present study was to define the point at which high protein diets are voluntarily diluted by choice of protein-free diet and the extent to which this occurs at various protein levels. MATERIALS AND METHODS
Eight synthetic diets were formulated in which the protein concentration was progressively raised from 0 (PF) to 80 per cent (diets CM20 to CM80 where 20 and 80 represent the percentage of protein). The diets were kept isocaloric by replacing equal parts of corn starch and sucrose with DL-methionine fortified casein as the sole protein source (see Table I).
FOOD INTAKE REGULATION IN PIGS, III.
5 23
TABLE I PERCENTAGE COMPOSITIO N
Ingredients Casein Sucrose Corn starch Cellulose Vegetable oil Vitaminmineral t premix
OF DIETS
PF
CM20*
CM30
CM10
CM50
CM60
CM7°
CMBo
53 34 4 3
20 43 24 4 3
30 38 19 4 3
40 33 14 4 3
50 28 9 4 3
60 23 4 4 3
70 17 0 4 3
80 7
6
6
6
6
6
6
6
6
0
4 3
• DL-Methionine ( 0'2 per cent) was added to each casein diet, (Feed grade not less than 99 per cent) , t Contains per kg of diet: Minerals: Ca, 10'15 g; P, 7'30 mg; Na, 3'2 g; K, 4'10 g; Cl, 1,6 g; S, 2'24 g; Mg, 400 mg; Mn, 120 mg; Zn, 100 mg; Fe, 310 mg; Cu,6 mg; I, 2'3 mg; CO, 0'4 mg; Mo, 0'1 mg; Se, 0'1 mg; F, 64 mg, Vitamins: A, 6750 VSP; D., 2250 USP; E, 2'5 IV; Menadione, 5,6; Riboflavin, 9'1; Thiamin HCl, 4'5 mg; Pantothenic acid, 16'7 mg; Niacin, 45'1 mg; Choline chloride, 1225 mg; B ... 0'025 mg ; Folic acid, 3'4 mg; Pyridoxine, 3,6 mg; Biotin, 2'2 !Lg, Antibiotic: Bacitracin (from bacitracin methylene disalicylate) 22 mg,
In the experiment six Duroc gilts with an approximate initial weight of 45 kg were housed in a temperature-controlled room in individual pens. Water was provided ad libitum from automatic drinkers throughout the experiment. Initially the 20 per cent casein diet was fed on its own for a four-day adjustment period to the synthetic diet. At the beginning of the experimental period two feed boxes were placed in the pens with the protein-free diet offered in one and the 20 per cent casein offered in the other for a seven-day test period. After the first seven days the second seven-day test period began immediately with 30 per cent casein now replacing the 20 per cent casein and in subsequent weeks the other casein diets were offered to the same gilts, each week the casein being raised 10 per cent. The protein free diet was always offered in the same box and the same location within the pens. Feed was weighed out daily and the unconsumed feed was weighed at the end of each weekly experimental period so that an average daily food intake value was then calculated. A sample of each feed and a sample from the unconsumed feed of each pig was dried at 70°C in a forced air oven for 4.8 h so that food intake could be expressed on a dry matter basis. All pigs were weighed at the beginning of the trial and subsequently at the end of each week RESULTS AND DISCUSSION
The results are summarized in Fig. I with the standard error of the mean for six pigs shown at each data point. There is a gradual shift in preference from the casein diets to the protein free. However, between dietary casein levels of 30 and 60 per cent preference for the casein diets remained at near 60-70 per cent of total daily food intake in spite of an apparent depression of total food intake and growth which was most noticeable at the 60 per cent casein level. It was not until the casein level was raised to 70 per cent that the pigs began to select more of the protein-free diets. There appeared to be a gradual recovery in food intake and of growth as the pigs diluted the high protein with the protein-free diet.
BRITISH VETERINARY JOURNAL, 130, 6
- - - Casein diet - - - - Protein-free diet
I
100
SE of mean
~
.e
.!:
8.....
.. .e'" ..
!"'H"--I--I )---1
75
b c
50
~ lL
--1--+---!----( ____ 1 y/ I
25
o
70
80
Percentage of d ietary casein
Fig.
I.
Voluntary diet selection by gilts.
There was considerable variation between pigs in their preference as the casein was increased. The extent of this variability is demonstrated in Fig. 2 where the data from two extreme pigs are plotted. One pig consumed more of the protein-free diet when the casein level reached 40 per cent; the other continued to consume the 80 per cent casein diet rather than consume the
100
e __e
....o .,
0' c.,o 50 .,~
I
lL
25
if"
//
I
I
/>---~--.. / / /
__e /
e --
o Percentage of dietary casein
e- e e ---e
Pig Pig 0----0 Pig O---
Fig.
I I 2 2
2.
consumption consumption consumption consumption
of of of of
casein diets PFdiet casein diets PFd iet
Voluntary diet selection by two gilts.
FOOD INTAKE REGULATION IN PIGS. III.
protein-free. This latter individual consumed over 1 kg of casein a day at one point without any noticeable depression of her total food intake. The d a ta points at 50, 60 and 70 per cent dietary casein in Fig. 1 are not significantly different owing to this large variation; all other points in Fig. 1 are (P < 0'05 ). Fig. 3 reports the food and protein consumption per unit of metabolic weight (kg 3 /4 power). The marked depression in intake is still apparent with the slight recovery occurring at the higher casein level. Protein intake was far more variable than total food intake, but increased, plateaued, and then dropped precipitously as the pigs began to reject the diets of high protein concentration in favour of the protein-free diet. It would appear that the pigs had an initial tendency to overdilute the protein as they began to reject the high casein diets which is indicated by the depression of both food intake and growth in the week their preference changed. Subsequently, in the following week they became more proficient in adjusting their protein intake so that both food intake and growth recovered. It can be concluded that growing pigs will select a 20 per cent casein diet fortified with methionine over one devoid of protein. The preference for the casein diet at the 20 per cent level was the same as for a 9 per cent casein methionine diet (Jackson, Robinson & Khalaf, 1970) at 84 per cent of the total dry matter intake in both cases when offered together with a protein-free diet. However, the pig does not seem very adept in diluting the higher levels of protein (60 p er cent casein) a nd tends to consume excessive amounts of protein .140
120
80
:30
OJ
-""
20
E
,!: c ';;;
e 10 Cl.
0
10
20
:30
40
50
Percentage of dietary cosein
Fig. 3. Food and protein intake (g/day/wt. kg 0.70).
BRITISH VETERINARY JOURNAL, 130,6
with the result that food intake and growth are curtailed. When the casein is raised to 70 per cent and higher, then the pigs' ability to dilute the high concentration of protein improves. On average, at the 70 per cent casein level the pig will begin to reject the protein-containing diet and consume a greater proportion of a protein-free diet. There is a considerable variation in the individual response of pigs however. One pig refused the 40 per cent casein diet and on the other hand, another pig continued to consume more of the 80 per cent casein diet than the protein-free. The concentration of protein was increased in successive weeks, so that the pigs may have adapted to the high levels of protein. This could affect their preference and have enabled them to reject the protein-free diet to a greater extent than if the protein level had been decreased to 80 per cent at one time. Studies of this nature where a protein-free diet is offered together with a protein containing diet have been most commonly performed where the protein diet has a disproportionate distribution of amino acid. These have been predominantly with the rat (Sanahuja & Harper, 1962; Leung, Rogers & Harper, 1968) although recently this approach has been applied to the pig (J ackson, Robinson & Khalaf, 1970 ; Devilat, Pond & Miller, 1970). It has been shown conclusively that the rat will prefer a protein-free diet to one low in protein and with a disproportionate distribution of amino acids and the pig appears to behave in the same way (Robinson, 1974). The rat offered a choice of a protein-free diet and one of high protein concentration will not select the protein-free diet until the protein is raised over 60 per cent (Rogers, 1970, personal communication). This is slightly lower than our data show for the pig, but it is in a comparable range. ACKNOWLEDGEMENTS
This study was financed by Grant No. 427 from the Nutrition Foundation, New York, and by generous donations from the Tanabe-Seiyaku Co. Ltd., of Osaka, Japan. The expert technical assistance of Karen Hazelwood, Mike Broderick and Jim Robb is gratefully acknowledged. REFERENCES
w.
J.
DEVILAT,J., POND, G. & MILLER, P. D. ( 1970). animo Sci. 31, 536. JACKSON, H . M., ROBINSON, D. W. & KHALAF, F. (1970). animo Sci. 31, 204 LEUNG, P. M. B., ROGERS, R. & HARPER, A. E. (1968). Nutr. 95, 483. ROBINSON, D. W. (1974). Br. vet. 130, 522. SANAHUJA, J . C. & HARPER, A. E. (1962). Am. Physiol. 202, 165.
Q.
J.,
J.
J.
(Abstr. ).
J.
(Acceptedfor publication 7 June 197 3) Regulation de la ration allulDentaire chez les pores. m. Selection aliJDentaire volontaire entre des regimes protidiques libres et des regimes riches en pro tides (Robinson) ResulDe. On logea six truies de race Duroc pesant 45 Kg, individuellement dans une piece ou la temperature est controlee. On leur offrit deux regimes isocaloriques semi-purifies; un
FOOD INTAKE REGULATION IN PIGS. III. regime protidique libre (PL) etait constamment utilisable au cours de la periode experimentale de sept semaines. On donna aux truies au COUTS des sernaines se succedant, des regimes alternatifs avec des taux croissants de caseine renforces avec 0·2 pour cent de DL-methionine (CM), a des taux d e pourcentage de 20 (CM 20), 30 (CM 30),40 (CM40), 50 (CM 50), 60 (CM 60), 70 (CM 70), Bo (CM Bo). La consommation volontaire concernant chaque regime, exprime en tante que pourcentage de la prise totale moyenne etait la premiere semaine, PL 16, CM20 B4; la deuxieme semaine PL 2B, CM30 72; la troisieme semaine PL 29, CM40 71 ; la quatrieme semaine PL 37, CM50 63; La cinquieme semaine PL 33, CM60 67; la sixieme semaine PL 71, CM70 29; la septieme semaine PL 77, CMBo 23. La concentration protidique moyenne atteignit 70 pour cent avant que Ie regime protidique ne soit ecarte pour etre remplace par un regime depourva de proteines, ceci malgre la variation individuelle existant parmi les pores et qui etait considerable.
Regelung der Futterzufuhr bei Schweinen. m. Selbstandige Futterwahl zwischen proteinfreieln und proteinreicheln Futter (Robinson) Zusalnlnenfassung. Sechs junge Duroc Saue wurden einzeln in Stallen untergebracht, deren Temperatur kontrolliert wurde. Es wurden ihnen zwei isokalorische halbgereinigte Arten von Futter zur Verftigung gestellt. Proteinfreies Futter (PF) war wahrend der gesamten siebenwochigen Versuchszeit vorhanden. In aufeinander folgenden Wochen wurde den jungen Siiuen abwechelnde Futterarten mit zunehmendem Gehalt von Kasein plus 0,2 % DL-Methionin (CM ) in einer prozentualen Konzentration von 20% (CM20), 30% (CM30), 40 % (CM40), 50 % (CM50), 60% (CM60), 70 % (CM70), Bo% (C MBo ) angeboten. Die Entscheidung fUr eine der Futterarten, ausgedriickt als Prozentsatz des durchschnittlichen gesamten Konsums, war in der I. Woche PF 16: CM20, B4; in d er 2. Woche PF 2B: CM30, 72 ; in der 3. Woche PF 29: CM40, 71; in der 4. Woche PF 37: CM50, 63; in der 5. Woche PF33: CM60, 67; in der 6. Woche PF 71 : CM70, 29; in der 7. Woche PF 77: CMBo, 23. Die durchschnittliche Proteinkonzentration erreichte einen prozentgehalt von 70 % beY~r das proteinhaltige Futter abgelehnt und das proteinfreie vorgezogen wurde, obwohl bei den verschiedenen Schweinen erhebliche Unterschiede beobachtet wurden. Regulacion de la ingestion de aliInentos en los cerdos. m. Seleccion voluntaria de alhnentos entre dietas ricas en proteinas y libres de proteinas (Robinson) Resumen. Se aislaron individualmente seis cerdas jovenes Duroc con un peso de 45 Kg en una temperatura ambiente controlada. Una vez aisladas se les afrecio dos dietas isocaloricas semipurificadas; durante el periodo experimental de siete semanas se dispuso constantemente de una dieta libre de protein as (PF). En las siguientes semanas se proporciono a los animales otras dietas conteniendo niveles cada vez mayores d e caseina fortificada con 0,2 por ciento de DL-metionina (CM ) a unos porcentajes de 20 (CM20), 30 (CM30), 40 (CM40), 50 (CM50), 60 (CM60), 70 (CM70), Bo (C MBo ). EI consumo voluntario de cada dieta expresado en porcent~ es d e la ingestion total promedia de cada dieta resp ectiva fu e el siguiente: Semana I, PF 16: CM20 84; Semana 2, PF 28: CM30 72; Semana 3, PF 29: CM40 71; Semana 4, PF37: CM50 63; Semana 5, PF 33: CM60 67; Semana 6, PF 71: CM70 29; Semana 7, PF 77: CM80 23. La con centra cion proteica media alcanzo un nivel del 70 por ciento antes de que la dieta con protein as fuese rechazada en favor de la otra dieta sin proteinas, aunque las variaciones individuales entre los distintos cerdos fue considerable.
J.
(1974),130,522
FOOD INTAKE REGULATION IN PIGS. III. VOLUNTARY FOOD SELECTION BETWEEN PROTEIN-FREE AND PROTEIN-RICH DIETS By D. \V.
ROBINSON
Department of Animal Science, University of California, Davis 95616 SUMMARY
Six Duroc gilts weighing 45 kg were housed individually in a temperature controlled room. They were offered two isocaloric semipurified diets; one protein-free diet (PF) was constantly available throughout the seven-week experimental period. In successive weeks the gilts were provided with alternative diets of increasing levels of casein fortified with 0'2 per cent DL-methionine (CM) at the percentage levels of 20 (CM20), 30 (CM30), 40 (CM40), 50 (CM50), 60 (CM60), 70 (CM70), 80 (CM80). The voluntary consumption for each diet expressed as a percentage of the average total intake for the respective diets was Week I, PF 16: CM20 84; Week 2, PF 28: CM30 72; Week 3, PF 29: CM40 71; Week 4, PF 37: CM50 63; Week 5, PF 33: CM60 67; Week 6, PF71: CM70 29; Week 7, PF 77: CM80 23· The mean protein concentration reached 70 per cent before the diet with protein would be rejected for one devoid of protein, although individual variation between pigs was considerable. INTRODUCTION
Protein-free diets have been used in free choice studies with the pig to assess the preference between amino acid deficient, adequate or protein-free diets (Jackson, Robinson & Khalaf 1970; Devilat, Pond & Miller, 1970). It has been shown that protein-free diets are rejected by the growing pigs in favour of well-balanced diets but preferred to a degree over amino acid deficient or imbalanced diets, as indeed they are also in the rat (Leung, Rogers & Harper, 1969). No work has been reported however on the effect of protein level per se on the choice made by pigs between a protein-free diet and one with a high concentration of protein. As the protein level itself may influence the choice made, the object of the present study was to define the point at which high protein diets are voluntarily diluted by choice of protein-free diet and the extent to which this occurs at various protein levels. MATERIALS AND METHODS
Eight synthetic diets were formulated in which the protein concentration was progressively raised from 0 (PF) to 80 per cent (diets CM20 to CM80 where 20 and 80 represent the percentage of protein). The diets were kept isocaloric by replacing equal parts of corn starch and sucrose with DL-methionine fortified casein as the sole protein source (see Table I).
FOOD INTAKE REGULATION IN PIGS, III.
5 23
TABLE I PERCENTAGE COMPOSITIO N
Ingredients Casein Sucrose Corn starch Cellulose Vegetable oil Vitaminmineral t premix
OF DIETS
PF
CM20*
CM30
CM10
CM50
CM60
CM7°
CMBo
53 34 4 3
20 43 24 4 3
30 38 19 4 3
40 33 14 4 3
50 28 9 4 3
60 23 4 4 3
70 17 0 4 3
80 7
6
6
6
6
6
6
6
6
0
4 3
• DL-Methionine ( 0'2 per cent) was added to each casein diet, (Feed grade not less than 99 per cent) , t Contains per kg of diet: Minerals: Ca, 10'15 g; P, 7'30 mg; Na, 3'2 g; K, 4'10 g; Cl, 1,6 g; S, 2'24 g; Mg, 400 mg; Mn, 120 mg; Zn, 100 mg; Fe, 310 mg; Cu,6 mg; I, 2'3 mg; CO, 0'4 mg; Mo, 0'1 mg; Se, 0'1 mg; F, 64 mg, Vitamins: A, 6750 VSP; D., 2250 USP; E, 2'5 IV; Menadione, 5,6; Riboflavin, 9'1; Thiamin HCl, 4'5 mg; Pantothenic acid, 16'7 mg; Niacin, 45'1 mg; Choline chloride, 1225 mg; B ... 0'025 mg ; Folic acid, 3'4 mg; Pyridoxine, 3,6 mg; Biotin, 2'2 !Lg, Antibiotic: Bacitracin (from bacitracin methylene disalicylate) 22 mg,
In the experiment six Duroc gilts with an approximate initial weight of 45 kg were housed in a temperature-controlled room in individual pens. Water was provided ad libitum from automatic drinkers throughout the experiment. Initially the 20 per cent casein diet was fed on its own for a four-day adjustment period to the synthetic diet. At the beginning of the experimental period two feed boxes were placed in the pens with the protein-free diet offered in one and the 20 per cent casein offered in the other for a seven-day test period. After the first seven days the second seven-day test period began immediately with 30 per cent casein now replacing the 20 per cent casein and in subsequent weeks the other casein diets were offered to the same gilts, each week the casein being raised 10 per cent. The protein free diet was always offered in the same box and the same location within the pens. Feed was weighed out daily and the unconsumed feed was weighed at the end of each weekly experimental period so that an average daily food intake value was then calculated. A sample of each feed and a sample from the unconsumed feed of each pig was dried at 70°C in a forced air oven for 4.8 h so that food intake could be expressed on a dry matter basis. All pigs were weighed at the beginning of the trial and subsequently at the end of each week RESULTS AND DISCUSSION
The results are summarized in Fig. I with the standard error of the mean for six pigs shown at each data point. There is a gradual shift in preference from the casein diets to the protein free. However, between dietary casein levels of 30 and 60 per cent preference for the casein diets remained at near 60-70 per cent of total daily food intake in spite of an apparent depression of total food intake and growth which was most noticeable at the 60 per cent casein level. It was not until the casein level was raised to 70 per cent that the pigs began to select more of the protein-free diets. There appeared to be a gradual recovery in food intake and of growth as the pigs diluted the high protein with the protein-free diet.
BRITISH VETERINARY JOURNAL, 130, 6
- - - Casein diet - - - - Protein-free diet
I
100
SE of mean
~
.e
.!:
8.....
.. .e'" ..
!"'H"--I--I )---1
75
b c
50
~ lL
--1--+---!----( ____ 1 y/ I
25
o
70
80
Percentage of d ietary casein
Fig.
I.
Voluntary diet selection by gilts.
There was considerable variation between pigs in their preference as the casein was increased. The extent of this variability is demonstrated in Fig. 2 where the data from two extreme pigs are plotted. One pig consumed more of the protein-free diet when the casein level reached 40 per cent; the other continued to consume the 80 per cent casein diet rather than consume the
100
e __e
....o .,
0' c.,o 50 .,~
I
lL
25
if"
//
I
I
/>---~--.. / / /
__e /
e --
o Percentage of dietary casein
e- e e ---e
Pig Pig 0----0 Pig O---
Fig.
I I 2 2
2.
consumption consumption consumption consumption
of of of of
casein diets PFdiet casein diets PFd iet
Voluntary diet selection by two gilts.
FOOD INTAKE REGULATION IN PIGS. III.
protein-free. This latter individual consumed over 1 kg of casein a day at one point without any noticeable depression of her total food intake. The d a ta points at 50, 60 and 70 per cent dietary casein in Fig. 1 are not significantly different owing to this large variation; all other points in Fig. 1 are (P < 0'05 ). Fig. 3 reports the food and protein consumption per unit of metabolic weight (kg 3 /4 power). The marked depression in intake is still apparent with the slight recovery occurring at the higher casein level. Protein intake was far more variable than total food intake, but increased, plateaued, and then dropped precipitously as the pigs began to reject the diets of high protein concentration in favour of the protein-free diet. It would appear that the pigs had an initial tendency to overdilute the protein as they began to reject the high casein diets which is indicated by the depression of both food intake and growth in the week their preference changed. Subsequently, in the following week they became more proficient in adjusting their protein intake so that both food intake and growth recovered. It can be concluded that growing pigs will select a 20 per cent casein diet fortified with methionine over one devoid of protein. The preference for the casein diet at the 20 per cent level was the same as for a 9 per cent casein methionine diet (Jackson, Robinson & Khalaf, 1970) at 84 per cent of the total dry matter intake in both cases when offered together with a protein-free diet. However, the pig does not seem very adept in diluting the higher levels of protein (60 p er cent casein) a nd tends to consume excessive amounts of protein .140
120
80
:30
OJ
-""
20
E
,!: c ';;;
e 10 Cl.
0
10
20
:30
40
50
Percentage of dietary cosein
Fig. 3. Food and protein intake (g/day/wt. kg 0.70).
BRITISH VETERINARY JOURNAL, 130,6
with the result that food intake and growth are curtailed. When the casein is raised to 70 per cent and higher, then the pigs' ability to dilute the high concentration of protein improves. On average, at the 70 per cent casein level the pig will begin to reject the protein-containing diet and consume a greater proportion of a protein-free diet. There is a considerable variation in the individual response of pigs however. One pig refused the 40 per cent casein diet and on the other hand, another pig continued to consume more of the 80 per cent casein diet than the protein-free. The concentration of protein was increased in successive weeks, so that the pigs may have adapted to the high levels of protein. This could affect their preference and have enabled them to reject the protein-free diet to a greater extent than if the protein level had been decreased to 80 per cent at one time. Studies of this nature where a protein-free diet is offered together with a protein containing diet have been most commonly performed where the protein diet has a disproportionate distribution of amino acid. These have been predominantly with the rat (Sanahuja & Harper, 1962; Leung, Rogers & Harper, 1968) although recently this approach has been applied to the pig (J ackson, Robinson & Khalaf, 1970 ; Devilat, Pond & Miller, 1970). It has been shown conclusively that the rat will prefer a protein-free diet to one low in protein and with a disproportionate distribution of amino acids and the pig appears to behave in the same way (Robinson, 1974). The rat offered a choice of a protein-free diet and one of high protein concentration will not select the protein-free diet until the protein is raised over 60 per cent (Rogers, 1970, personal communication). This is slightly lower than our data show for the pig, but it is in a comparable range. ACKNOWLEDGEMENTS
This study was financed by Grant No. 427 from the Nutrition Foundation, New York, and by generous donations from the Tanabe-Seiyaku Co. Ltd., of Osaka, Japan. The expert technical assistance of Karen Hazelwood, Mike Broderick and Jim Robb is gratefully acknowledged. REFERENCES
w.
J.
DEVILAT,J., POND, G. & MILLER, P. D. ( 1970). animo Sci. 31, 536. JACKSON, H . M., ROBINSON, D. W. & KHALAF, F. (1970). animo Sci. 31, 204 LEUNG, P. M. B., ROGERS, R. & HARPER, A. E. (1968). Nutr. 95, 483. ROBINSON, D. W. (1974). Br. vet. 130, 522. SANAHUJA, J . C. & HARPER, A. E. (1962). Am. Physiol. 202, 165.
Q.
J.,
J.
J.
(Abstr. ).
J.
(Acceptedfor publication 7 June 197 3) Regulation de la ration allulDentaire chez les pores. m. Selection aliJDentaire volontaire entre des regimes protidiques libres et des regimes riches en pro tides (Robinson) ResulDe. On logea six truies de race Duroc pesant 45 Kg, individuellement dans une piece ou la temperature est controlee. On leur offrit deux regimes isocaloriques semi-purifies; un
FOOD INTAKE REGULATION IN PIGS. III. regime protidique libre (PL) etait constamment utilisable au cours de la periode experimentale de sept semaines. On donna aux truies au COUTS des sernaines se succedant, des regimes alternatifs avec des taux croissants de caseine renforces avec 0·2 pour cent de DL-methionine (CM), a des taux d e pourcentage de 20 (CM 20), 30 (CM 30),40 (CM40), 50 (CM 50), 60 (CM 60), 70 (CM 70), Bo (CM Bo). La consommation volontaire concernant chaque regime, exprime en tante que pourcentage de la prise totale moyenne etait la premiere semaine, PL 16, CM20 B4; la deuxieme semaine PL 2B, CM30 72; la troisieme semaine PL 29, CM40 71 ; la quatrieme semaine PL 37, CM50 63; La cinquieme semaine PL 33, CM60 67; la sixieme semaine PL 71, CM70 29; la septieme semaine PL 77, CMBo 23. La concentration protidique moyenne atteignit 70 pour cent avant que Ie regime protidique ne soit ecarte pour etre remplace par un regime depourva de proteines, ceci malgre la variation individuelle existant parmi les pores et qui etait considerable.
Regelung der Futterzufuhr bei Schweinen. m. Selbstandige Futterwahl zwischen proteinfreieln und proteinreicheln Futter (Robinson) Zusalnlnenfassung. Sechs junge Duroc Saue wurden einzeln in Stallen untergebracht, deren Temperatur kontrolliert wurde. Es wurden ihnen zwei isokalorische halbgereinigte Arten von Futter zur Verftigung gestellt. Proteinfreies Futter (PF) war wahrend der gesamten siebenwochigen Versuchszeit vorhanden. In aufeinander folgenden Wochen wurde den jungen Siiuen abwechelnde Futterarten mit zunehmendem Gehalt von Kasein plus 0,2 % DL-Methionin (CM ) in einer prozentualen Konzentration von 20% (CM20), 30% (CM30), 40 % (CM40), 50 % (CM50), 60% (CM60), 70 % (CM70), Bo% (C MBo ) angeboten. Die Entscheidung fUr eine der Futterarten, ausgedriickt als Prozentsatz des durchschnittlichen gesamten Konsums, war in der I. Woche PF 16: CM20, B4; in d er 2. Woche PF 2B: CM30, 72 ; in der 3. Woche PF 29: CM40, 71; in der 4. Woche PF 37: CM50, 63; in der 5. Woche PF33: CM60, 67; in der 6. Woche PF 71 : CM70, 29; in der 7. Woche PF 77: CMBo, 23. Die durchschnittliche Proteinkonzentration erreichte einen prozentgehalt von 70 % beY~r das proteinhaltige Futter abgelehnt und das proteinfreie vorgezogen wurde, obwohl bei den verschiedenen Schweinen erhebliche Unterschiede beobachtet wurden. Regulacion de la ingestion de aliInentos en los cerdos. m. Seleccion voluntaria de alhnentos entre dietas ricas en proteinas y libres de proteinas (Robinson) Resumen. Se aislaron individualmente seis cerdas jovenes Duroc con un peso de 45 Kg en una temperatura ambiente controlada. Una vez aisladas se les afrecio dos dietas isocaloricas semipurificadas; durante el periodo experimental de siete semanas se dispuso constantemente de una dieta libre de protein as (PF). En las siguientes semanas se proporciono a los animales otras dietas conteniendo niveles cada vez mayores d e caseina fortificada con 0,2 por ciento de DL-metionina (CM ) a unos porcentajes de 20 (CM20), 30 (CM30), 40 (CM40), 50 (CM50), 60 (CM60), 70 (CM70), Bo (C MBo ). EI consumo voluntario de cada dieta expresado en porcent~ es d e la ingestion total promedia de cada dieta resp ectiva fu e el siguiente: Semana I, PF 16: CM20 84; Semana 2, PF 28: CM30 72; Semana 3, PF 29: CM40 71; Semana 4, PF37: CM50 63; Semana 5, PF 33: CM60 67; Semana 6, PF 71: CM70 29; Semana 7, PF 77: CM80 23. La con centra cion proteica media alcanzo un nivel del 70 por ciento antes de que la dieta con protein as fuese rechazada en favor de la otra dieta sin proteinas, aunque las variaciones individuales entre los distintos cerdos fue considerable.