Digestive Diseases and Sciences, Vol. 37, No. 1 (January 1992), pp. 40-46
Activity Distribution of Seven Digestive Enzymes along Small Intestine in Calves during Development and Weaning ISABELLE LE H U E R O U , PhD, PAUL GUILLOTEAU, PhD, CATHERINE WICKER, PhD, AZIZ MOUATS, PhD, JEAN-ALAIN CHAYVIALLE, PhD, CHRISTINE BERNARD, PhD, JOHN BURTON, PhD, RENE TOULLEC, PhD, and ANTOINE PUIGSERVER, PhD
Ten groups o f calves were used to study the changes in activity levels and distribution o f seven hydrolases in the intestinal mucosa during deVelopment and weaning. The calves in the first group were sacrificed at birth while those in the remaining nine groups were either milk-fed until slaughter on days 2, 7, 28, 56, 70, and 119; or weaned between days 28 and 56 and then slaughtered on days 56, 70, and 119, respectively. The small intestine was immediately cut off and divided into five segments, ie, duodenum, proximal jejunum, median jejunum, distal jejunum, and ileum. In the milk-fed animals, the activity levels of aminopeptidases A and N, alkaline phosphatase, lactase, and isomaltase were maximum at 2 days of age, and then declined sharply between days 2 and 7 but did not change significantly thereafter. By contrast, the maltase activity increased between days 7 and 119, while no sucrase activity was detected. Weaning resulted in a decrease in the activity o f lactase and an increase in that o f aminopeptidase N, maltase, and isomaltase. The distribution o f all these enzymes along the small intestine was slightly influenced by age but not at all by weaning. KEY WORDS: intestinal enzymes; calf; development; milk-feeding; weaning.
During the first four to six months of postnatal life, calves can be either maintained at the preruminant stage if they are entirely milk-fed, or weaned and thus transformed into ruminants. Many studies have been devoted to the changes in the activity levels of disaccharidases that occur during development and weaning in the young ruminant small intestine (1, 2). The overall activity of lactase, per unit of empty live Manuscript received October 30, 1990; revised manuscript received March 7, 1991; accepted March 11, 1991. From the Institut National de la Recherche Agronomique, 65, rue de St-Brieuc, 35042 Rennes C6dex; Institut National de la Sant6 et de la Recherche M6dicale, H6pital Edouard Herriot, 69374 Lyon C6dex; and Centre National de la Recherche Scientifique, 13402 Marseille C6dex 9, France. The financial support of the European Community (No. 4 111 A) is gratefully acknowledged. Address for reprint requests: Isabelle Le Hu6rou, INRA Jeune Ruminant, 65, rue de St-Brieuc, 35042 Rennes C6dex, France.
40
weight, was high at birth and then decreased with age and upon weaning, whereas the maltase activity was very low at birth but increased with age as well as after weaning. By contrast, no sucrase activity was detected in the small intestine and no data are so far available on the aminopeptidase A and N activities or the alkaline phosphatase activity during development and weaning in the calf. Little is known either about isomaltase activity (2). The purpose of the present study was to investigate the effects of age and weaning on the activity levels of seven intestinal hydrolaseS as well as their distribution along the small intestine in the calf. The development of intestinal digestive function was tentatively correlated with the changes in the plasma and tissue concentrations of some gut hormones. Digestive Diseases and Sciences, Vol. 37, No. 1 (January 1992)
0163-2116/92/0100-0040506.50/09 1992PlenumPublishingCorporation
I N T E S T I N A L E N Z Y M E LEVELS IN CALVES TABLE 1. EMPTY LIVE WEIGHT, LIVE WEIGHT GAIN, INTESTINAL MUCOSA WEIGHT, AND INTESTINAL PROTEIN CONTENT OF PRERUMINANT AND RUMINANT CALVES BETWEEN BIRTH AND SLAUGHTER* Stage
Preruminant
Age at slaughter (day) Live weight gain (g/day) Empty live weight (kg) Intestinal mucosa weight (g/kg ELW) Intestinal protein content (mg/kg ELW) Dry matter intake (g/day)
0 45.8 • 2.5 5.5 --- 0.5 357 • 26
Stage
-210 33.8 6.0 455 436
2 • 248 1.5 -+ 0.3 • 25 --- 54(a)
-343 42.4 2.9 164 371
7 • 132 -+ 4.7 • 0.3 • 17 - 25
Preruminant
Age at slaughter (day) Live weight gain (g/day) Empty live weight (kg) Intestinal mucosa weight (g/kg ELW) Intestinal protein content (mg/kg ELW) Dry matter intake(g/day)
70 843 -+ 52 98.5 --- 4.6 1.7 -+ 0.2 119 - 9 1842 + 42
28 400 • 41 51.5 --- 3.3 3.1 • 0.4 187 • 35 1013 • 31
56 711 • 36 82.4 -+ 3.2 2.4 -+ 0.2 162 • 10 1585 • 53
Ruminant
119 1081 --- 54 172.3 • 4.1 1.7 - 0.3 116 -- 21 2681 • 81
56 446 - 62 65.6 -+ 3.2 2.2 -+ 0.2 137 • 13 1205 -+ 173
70 594 - 34 74.5 -+ 2.7 2.6 -+ 0.1 167 +- 14 2212 -+ 119
119 766 + 36 117.6 -+ 2.9 1.4 +- 0.1 83 • 9 3827 +- 203
*Means and standard errors, n = 5. Dry matter intake was the mean of the values obtained during the week prior to slaughter or (a) between birth and 2 days of age.
M A T E R I A L S AND M E T H O D S Animals and Diet. Fifty newborn Holstein-Friesian male calves were randomly distributed into 10 groups of five animals each. The calves in the first group were slaughtered less than 1 hr after birth prior to any milk intake, while those in the second group were sacrificed at 2 days of age after being given two colostrum meals (25 g/kg live weight/meal) during the first day. The calves in the third to seventh groups were given colostrum for the first two days of life, and then a milk substitute twice daily until slaughter on days 7, 28, 56. 70, and 119, respectively. The milk substitute was based on spraydried skim milk and tallow, and contained 25% crude protein, 22% fat, 43% lactose, 3% starch, and 7% minerals on a dry matter (DM) basis. The calves in the eighth to tenth groups were progressively weaned on hay and concentrate diet between days 29 and 55 before being slaughtered on days 56, 70, and 119, respectively. The hay contained 14% crude protein, 3% fat, 31% cellulose. and 9% ash while the concentrate contained 23% crude protein, 2% fat, 60% starch, 5% cellulose, and 10% ash (DM basis). The amount of milk substitute was gradually reduced to nil between days 29 and 56, ie, from 950 to 710, 475, 235, and 0 g DM/day between days 29-35, 36-42, 43-49, 50-56, and onwards, respectively. The calves in the first seven groups were therefore preruminants, while those in the last three groups were ruminants. Except for those in the first group, all the calves were slaughtered 16-17 hr after the last meal. Removal and Storage of Tissues. The whole digestive tract was immediately removed after slaughter, and the small intestine was gently emptied of its contents, rinsed with an ice-cold 0.9% NaCI solution, gently blotted with filter paper, defatted, weighed, and finally spread onto a glass plate placed on chopped ice. It was then divided into five segments, ie, duodenum; j e j u n u m as three equal parts corresponding to proximal, median, and distal j e j u n u m ; and ileum. Each intestinal segment Digestive Diseases and Sciences, Vol. 37, No. 1 (Janua~. 1992)
was weighed and rinsed three times with a 50 mM phosphate buffer, pH 7.6, containing 2 mM benzamidine hydrochloride. The mucosa was scraped off by means of a microscope slide, weighed, and deep frozen in liquid nitrogen. The resulting samples were subsequently stored at - 1 8 ~ until analysis. Enzyme Activity Determination. After thawing, the intestinal mucosa was homogenized in cold water (100 mg/ml) and centrifuged for 5 rain at 1000g and 4~ C. The protein content was then determined as described by Hartree (3), using bovine serum albumin as a standard, while the activities of aminopeptidases A and N and that of alkaline phosphatase were assayed with L-glutamyl-pnitroanilide, L-leucyl-p-nitroanilide (4), and p-nitrophenylphosphate (5) as substrates, respectively. The resulting enzymatic units were expressed as micromoles of p-nitroanilide or p-nitrophenol released per minute at 37~ C. Lactase. maltase, isomaltase, and sucrase activities were determined using lactose in the absence of p-chloromercuribenzoate, maltose, isomaltose, and sucrose as substrates, respectively (6). One disaccharidase unit was taken to correspond to the release of one micromole of glucose per minute at 37~ C. Statistical Analysis. Analysis of variance was used to assess the effects of age in both preruminant and ruminant groups, and Newman-Keuls' test to classify the means. The significance (P -< 0.05) of the differences observed between preruminant and ruminant calves at 56, 70, and 119 days of age was determined using Mann-Whitney's test. Correlation coefficients were used to study the relationships between enzyme activities and the tissue or plasma concentrations of the gut hormones that were determined in a previous study (7). RESULTS
Growth and Food Intake. A f t e r a live weight loss d u r i n g the first w e e k o f life, a live weight gain as
41
LE HUEROU ET AL TABLE 2. DIETARY COMPONENTS INGESTED BY PRERUMINANT AND RUMINANT CALVES AND METABOLIZABLE ENERGY AVAILABLE DURING WEEK PRIOR TO SLAUGHTER* Stage
Preruminant
A g e at slaughter 2(a) 7 28 (day) Protein (g/kg 8.0 -+ 0.0 2.2 --- 0.3 4.9 ELW/day) Fat(g/kg 2.5-+0.0 2.0+-0.3 4.3-+ ELW/day) Lactose(g/kg 1.5• 3.9-+0.5 8.7--ELW/day) Starch(g/kg 0.3 • 0.6-+ ELW/day) Cellulose (g/kg ELW/day) Metabolizable 65.2 - 0.0 44.6 --- 5.9 99.2 --energy (kcal/kg ELW/day)
Ruminant
56
70
119
56
70
0.6
4.8 -+ 0.4
4.6 • 0.4
3.8 -+ 0.3
3.9 -+ 1.2
5.8 • 0.4
6.4 --- 0.7
1.9
4.2•
4.1-+0.4
3.4•
0.9-+
0.1
0.2•
0 . 2 -+
1.1
8.3 •
8.2-0.7
6.8•
1.7-
0.2
0.1
0.6-0.1
0.6•
0.5-+0.1
7.2-
2.9
1.7 -
0.7
13.5•
119
1.1
3.5 • 0.5
12.1 96.2 • 3.7 93.8 --- 8.2 79.1 -+ 6.1 70.7 -+ 21.7 104.7 --- 5.1
0.1
14.7 -+ 1.6 4.1 •
0.5
114.4 • 12.1
*Means a n d standard errors, n = 5; (a) b e t w e e n birth and 2 days of age.
high as 1081 g/day and 766 g/day was observed on day 119 in preruminants and ruminants, respectively (Table 1). The DM intake also increased progressively from 371 g/day to 2681 and 3827 g/day between days 7 and 119 in milk-fed and weaned calves, respectively. Table 2 shows that the preruminant calves ingested higher amounts of protein, fat, lactose, and starch per meal during the fourth week of life than during the first week except for the first meals of colostrum, which contained the highest amounts of protein. The intakes of all these dietary components subsequently either remained unchanged or were slightly reduced during the last week of life. During the weaning period from day 29 to day 56, lower amounts of fat and lactose, but higher amounts of starch were ingested. Thereafter, the ingestion of starch was further increased while that of fat decreased and that of lactose became nil. Organ Development. Because the live weights and digestive contents generally differed between the groups of prernminant and ruminant calves, the intestinal mucosa weights on the one hand, and the protein contents on the other hand were compared on an empty live weight (ELW) basis (Table 1). In the preruminant calves, the intestinal mucosa weight and protein content were maximum at two days of age and declined thereafter whereas both parameters were unchanged by weaning. Enzymatic Activities in Whole Small Intestine. In preruminant calves, the specific activity patterns of aminopeptidases A and N, and alkaline phosphatase were fairly similar (Figure 1). The activity levels were higher both at birth and on day 2 than on
42
day 7 (P -< 0.05 with aminopeptidase N alone), but further increased up to day 119. The lactase activity exhibited a similar trend during the first week of life but did not change significantly thereafter, while the maltase and isomaltase activities increased regularly with age, except from birth to days 2 and 28 (Figure 2). The activity of maltase was enhanced 10-fold between birth and day 119 and that of isomaltase was five- to sixfold higher at 70 and 119 days of age than on day 7. No sucrase activity was detected in the small intestine, however. When the enzyme activities were expressed on an ELW basis, the levels of aminopeptidases A and N and lactase increased 1.2- to 1.6-fold between birth and two days of age, but decreased sharply 4.6- to 8.0-fold between days 2 and 7 and did not change significantly thereafter. A similar pattern was observed in the case of alkaline phosphatase, but the variations were not significant. As regards maltase, no significant change was detected between birth and day 70, while a 2.5-fold enhancement was observed between days 70 and 119. The isomaltase activity was 4.6-fold lower on day 7 than on day 2 and increased thereafter slowly, but not significantly, with age. In ruminant calves, the specific activities of aminopeptidase N and maltase increased 1.6-fold and 2.2-fold between 70 and 119 days of age, and between 56 and 119 days of age, respectively. The activities of aminopeptidase N, maltase, and isomaltase were 2.1-, 3.2-, and 2.0-fold those recorded in unweaned animals on days 70, 70, and 56, respectively, while the activity of lactase was 1.7-fold Digestive Diseases and Sciences, Vol. 37, No. 1 (January 1992)
INTESTINAL ENZYME LEVELS IN CALVES LACTASE
AMINOPEPTIDASE A
12
250"
3
b
~" 200:
r
aI
o
,.? c
al la
E c
0
MALTASE
AMINOPEPTIDASE N b
120
6
t
a
~ 6O
c
*
b
a, 20'
2O c
'?, be ~
a
\
,
0
ISOMALTASE
ALKALLNEPHOSPHATASE 30"
a,
4"
5.0-
0.6
A 9 o
~ 2.5
~- 15 B
2" "
%
,
0.3
~
? a
a
a[ 0
0
40
80
120
40
80
120
AGE (day)
40
80
120
40
00
120
AGE ( d a y )
Fig 1. Changes in the overall specific activities and activities per kg E L W of aminopeptidases A and N and alkaline phosphatase
Fig 2. Changes in the overall specific activities and the activities per kg E L W of lactase, maltase, and isomaltase in the whole
in the whole small intestine during development and weaning (means and standard errors, n = 5) ([2, p r e r u m i n a n t s ; II, ruminants), a, b . . . . : Within each group values bearing only unlike letters differed significantly (P -< 0.05). *Significant diff e r e n c e between preruminants and ruminants (P -< 0.05).
small intestine during development and weaning (means and standard errors, n = 5) (D, p r e r u m i n a n t s ; I , r u m i n a n t s ) , a, b, 9 . .: Within each group values bearing only unlike letters differed significantly (P -< 0.05). *Significant difference between preruminants and ruminants (P
Activity Distribution of Seven Digestive Enzymes along Small Intestine in Calves during Development and Weaning ISABELLE LE H U E R O U , PhD, PAUL GUILLOTEAU, PhD, CATHERINE WICKER, PhD, AZIZ MOUATS, PhD, JEAN-ALAIN CHAYVIALLE, PhD, CHRISTINE BERNARD, PhD, JOHN BURTON, PhD, RENE TOULLEC, PhD, and ANTOINE PUIGSERVER, PhD
Ten groups o f calves were used to study the changes in activity levels and distribution o f seven hydrolases in the intestinal mucosa during deVelopment and weaning. The calves in the first group were sacrificed at birth while those in the remaining nine groups were either milk-fed until slaughter on days 2, 7, 28, 56, 70, and 119; or weaned between days 28 and 56 and then slaughtered on days 56, 70, and 119, respectively. The small intestine was immediately cut off and divided into five segments, ie, duodenum, proximal jejunum, median jejunum, distal jejunum, and ileum. In the milk-fed animals, the activity levels of aminopeptidases A and N, alkaline phosphatase, lactase, and isomaltase were maximum at 2 days of age, and then declined sharply between days 2 and 7 but did not change significantly thereafter. By contrast, the maltase activity increased between days 7 and 119, while no sucrase activity was detected. Weaning resulted in a decrease in the activity o f lactase and an increase in that o f aminopeptidase N, maltase, and isomaltase. The distribution o f all these enzymes along the small intestine was slightly influenced by age but not at all by weaning. KEY WORDS: intestinal enzymes; calf; development; milk-feeding; weaning.
During the first four to six months of postnatal life, calves can be either maintained at the preruminant stage if they are entirely milk-fed, or weaned and thus transformed into ruminants. Many studies have been devoted to the changes in the activity levels of disaccharidases that occur during development and weaning in the young ruminant small intestine (1, 2). The overall activity of lactase, per unit of empty live Manuscript received October 30, 1990; revised manuscript received March 7, 1991; accepted March 11, 1991. From the Institut National de la Recherche Agronomique, 65, rue de St-Brieuc, 35042 Rennes C6dex; Institut National de la Sant6 et de la Recherche M6dicale, H6pital Edouard Herriot, 69374 Lyon C6dex; and Centre National de la Recherche Scientifique, 13402 Marseille C6dex 9, France. The financial support of the European Community (No. 4 111 A) is gratefully acknowledged. Address for reprint requests: Isabelle Le Hu6rou, INRA Jeune Ruminant, 65, rue de St-Brieuc, 35042 Rennes C6dex, France.
40
weight, was high at birth and then decreased with age and upon weaning, whereas the maltase activity was very low at birth but increased with age as well as after weaning. By contrast, no sucrase activity was detected in the small intestine and no data are so far available on the aminopeptidase A and N activities or the alkaline phosphatase activity during development and weaning in the calf. Little is known either about isomaltase activity (2). The purpose of the present study was to investigate the effects of age and weaning on the activity levels of seven intestinal hydrolaseS as well as their distribution along the small intestine in the calf. The development of intestinal digestive function was tentatively correlated with the changes in the plasma and tissue concentrations of some gut hormones. Digestive Diseases and Sciences, Vol. 37, No. 1 (January 1992)
0163-2116/92/0100-0040506.50/09 1992PlenumPublishingCorporation
I N T E S T I N A L E N Z Y M E LEVELS IN CALVES TABLE 1. EMPTY LIVE WEIGHT, LIVE WEIGHT GAIN, INTESTINAL MUCOSA WEIGHT, AND INTESTINAL PROTEIN CONTENT OF PRERUMINANT AND RUMINANT CALVES BETWEEN BIRTH AND SLAUGHTER* Stage
Preruminant
Age at slaughter (day) Live weight gain (g/day) Empty live weight (kg) Intestinal mucosa weight (g/kg ELW) Intestinal protein content (mg/kg ELW) Dry matter intake (g/day)
0 45.8 • 2.5 5.5 --- 0.5 357 • 26
Stage
-210 33.8 6.0 455 436
2 • 248 1.5 -+ 0.3 • 25 --- 54(a)
-343 42.4 2.9 164 371
7 • 132 -+ 4.7 • 0.3 • 17 - 25
Preruminant
Age at slaughter (day) Live weight gain (g/day) Empty live weight (kg) Intestinal mucosa weight (g/kg ELW) Intestinal protein content (mg/kg ELW) Dry matter intake(g/day)
70 843 -+ 52 98.5 --- 4.6 1.7 -+ 0.2 119 - 9 1842 + 42
28 400 • 41 51.5 --- 3.3 3.1 • 0.4 187 • 35 1013 • 31
56 711 • 36 82.4 -+ 3.2 2.4 -+ 0.2 162 • 10 1585 • 53
Ruminant
119 1081 --- 54 172.3 • 4.1 1.7 - 0.3 116 -- 21 2681 • 81
56 446 - 62 65.6 -+ 3.2 2.2 -+ 0.2 137 • 13 1205 -+ 173
70 594 - 34 74.5 -+ 2.7 2.6 -+ 0.1 167 +- 14 2212 -+ 119
119 766 + 36 117.6 -+ 2.9 1.4 +- 0.1 83 • 9 3827 +- 203
*Means and standard errors, n = 5. Dry matter intake was the mean of the values obtained during the week prior to slaughter or (a) between birth and 2 days of age.
M A T E R I A L S AND M E T H O D S Animals and Diet. Fifty newborn Holstein-Friesian male calves were randomly distributed into 10 groups of five animals each. The calves in the first group were slaughtered less than 1 hr after birth prior to any milk intake, while those in the second group were sacrificed at 2 days of age after being given two colostrum meals (25 g/kg live weight/meal) during the first day. The calves in the third to seventh groups were given colostrum for the first two days of life, and then a milk substitute twice daily until slaughter on days 7, 28, 56. 70, and 119, respectively. The milk substitute was based on spraydried skim milk and tallow, and contained 25% crude protein, 22% fat, 43% lactose, 3% starch, and 7% minerals on a dry matter (DM) basis. The calves in the eighth to tenth groups were progressively weaned on hay and concentrate diet between days 29 and 55 before being slaughtered on days 56, 70, and 119, respectively. The hay contained 14% crude protein, 3% fat, 31% cellulose. and 9% ash while the concentrate contained 23% crude protein, 2% fat, 60% starch, 5% cellulose, and 10% ash (DM basis). The amount of milk substitute was gradually reduced to nil between days 29 and 56, ie, from 950 to 710, 475, 235, and 0 g DM/day between days 29-35, 36-42, 43-49, 50-56, and onwards, respectively. The calves in the first seven groups were therefore preruminants, while those in the last three groups were ruminants. Except for those in the first group, all the calves were slaughtered 16-17 hr after the last meal. Removal and Storage of Tissues. The whole digestive tract was immediately removed after slaughter, and the small intestine was gently emptied of its contents, rinsed with an ice-cold 0.9% NaCI solution, gently blotted with filter paper, defatted, weighed, and finally spread onto a glass plate placed on chopped ice. It was then divided into five segments, ie, duodenum; j e j u n u m as three equal parts corresponding to proximal, median, and distal j e j u n u m ; and ileum. Each intestinal segment Digestive Diseases and Sciences, Vol. 37, No. 1 (Janua~. 1992)
was weighed and rinsed three times with a 50 mM phosphate buffer, pH 7.6, containing 2 mM benzamidine hydrochloride. The mucosa was scraped off by means of a microscope slide, weighed, and deep frozen in liquid nitrogen. The resulting samples were subsequently stored at - 1 8 ~ until analysis. Enzyme Activity Determination. After thawing, the intestinal mucosa was homogenized in cold water (100 mg/ml) and centrifuged for 5 rain at 1000g and 4~ C. The protein content was then determined as described by Hartree (3), using bovine serum albumin as a standard, while the activities of aminopeptidases A and N and that of alkaline phosphatase were assayed with L-glutamyl-pnitroanilide, L-leucyl-p-nitroanilide (4), and p-nitrophenylphosphate (5) as substrates, respectively. The resulting enzymatic units were expressed as micromoles of p-nitroanilide or p-nitrophenol released per minute at 37~ C. Lactase. maltase, isomaltase, and sucrase activities were determined using lactose in the absence of p-chloromercuribenzoate, maltose, isomaltose, and sucrose as substrates, respectively (6). One disaccharidase unit was taken to correspond to the release of one micromole of glucose per minute at 37~ C. Statistical Analysis. Analysis of variance was used to assess the effects of age in both preruminant and ruminant groups, and Newman-Keuls' test to classify the means. The significance (P -< 0.05) of the differences observed between preruminant and ruminant calves at 56, 70, and 119 days of age was determined using Mann-Whitney's test. Correlation coefficients were used to study the relationships between enzyme activities and the tissue or plasma concentrations of the gut hormones that were determined in a previous study (7). RESULTS
Growth and Food Intake. A f t e r a live weight loss d u r i n g the first w e e k o f life, a live weight gain as
41
LE HUEROU ET AL TABLE 2. DIETARY COMPONENTS INGESTED BY PRERUMINANT AND RUMINANT CALVES AND METABOLIZABLE ENERGY AVAILABLE DURING WEEK PRIOR TO SLAUGHTER* Stage
Preruminant
A g e at slaughter 2(a) 7 28 (day) Protein (g/kg 8.0 -+ 0.0 2.2 --- 0.3 4.9 ELW/day) Fat(g/kg 2.5-+0.0 2.0+-0.3 4.3-+ ELW/day) Lactose(g/kg 1.5• 3.9-+0.5 8.7--ELW/day) Starch(g/kg 0.3 • 0.6-+ ELW/day) Cellulose (g/kg ELW/day) Metabolizable 65.2 - 0.0 44.6 --- 5.9 99.2 --energy (kcal/kg ELW/day)
Ruminant
56
70
119
56
70
0.6
4.8 -+ 0.4
4.6 • 0.4
3.8 -+ 0.3
3.9 -+ 1.2
5.8 • 0.4
6.4 --- 0.7
1.9
4.2•
4.1-+0.4
3.4•
0.9-+
0.1
0.2•
0 . 2 -+
1.1
8.3 •
8.2-0.7
6.8•
1.7-
0.2
0.1
0.6-0.1
0.6•
0.5-+0.1
7.2-
2.9
1.7 -
0.7
13.5•
119
1.1
3.5 • 0.5
12.1 96.2 • 3.7 93.8 --- 8.2 79.1 -+ 6.1 70.7 -+ 21.7 104.7 --- 5.1
0.1
14.7 -+ 1.6 4.1 •
0.5
114.4 • 12.1
*Means a n d standard errors, n = 5; (a) b e t w e e n birth and 2 days of age.
high as 1081 g/day and 766 g/day was observed on day 119 in preruminants and ruminants, respectively (Table 1). The DM intake also increased progressively from 371 g/day to 2681 and 3827 g/day between days 7 and 119 in milk-fed and weaned calves, respectively. Table 2 shows that the preruminant calves ingested higher amounts of protein, fat, lactose, and starch per meal during the fourth week of life than during the first week except for the first meals of colostrum, which contained the highest amounts of protein. The intakes of all these dietary components subsequently either remained unchanged or were slightly reduced during the last week of life. During the weaning period from day 29 to day 56, lower amounts of fat and lactose, but higher amounts of starch were ingested. Thereafter, the ingestion of starch was further increased while that of fat decreased and that of lactose became nil. Organ Development. Because the live weights and digestive contents generally differed between the groups of prernminant and ruminant calves, the intestinal mucosa weights on the one hand, and the protein contents on the other hand were compared on an empty live weight (ELW) basis (Table 1). In the preruminant calves, the intestinal mucosa weight and protein content were maximum at two days of age and declined thereafter whereas both parameters were unchanged by weaning. Enzymatic Activities in Whole Small Intestine. In preruminant calves, the specific activity patterns of aminopeptidases A and N, and alkaline phosphatase were fairly similar (Figure 1). The activity levels were higher both at birth and on day 2 than on
42
day 7 (P -< 0.05 with aminopeptidase N alone), but further increased up to day 119. The lactase activity exhibited a similar trend during the first week of life but did not change significantly thereafter, while the maltase and isomaltase activities increased regularly with age, except from birth to days 2 and 28 (Figure 2). The activity of maltase was enhanced 10-fold between birth and day 119 and that of isomaltase was five- to sixfold higher at 70 and 119 days of age than on day 7. No sucrase activity was detected in the small intestine, however. When the enzyme activities were expressed on an ELW basis, the levels of aminopeptidases A and N and lactase increased 1.2- to 1.6-fold between birth and two days of age, but decreased sharply 4.6- to 8.0-fold between days 2 and 7 and did not change significantly thereafter. A similar pattern was observed in the case of alkaline phosphatase, but the variations were not significant. As regards maltase, no significant change was detected between birth and day 70, while a 2.5-fold enhancement was observed between days 70 and 119. The isomaltase activity was 4.6-fold lower on day 7 than on day 2 and increased thereafter slowly, but not significantly, with age. In ruminant calves, the specific activities of aminopeptidase N and maltase increased 1.6-fold and 2.2-fold between 70 and 119 days of age, and between 56 and 119 days of age, respectively. The activities of aminopeptidase N, maltase, and isomaltase were 2.1-, 3.2-, and 2.0-fold those recorded in unweaned animals on days 70, 70, and 56, respectively, while the activity of lactase was 1.7-fold Digestive Diseases and Sciences, Vol. 37, No. 1 (January 1992)
INTESTINAL ENZYME LEVELS IN CALVES LACTASE
AMINOPEPTIDASE A
12
250"
3
b
~" 200:
r
aI
o
,.? c
al la
E c
0
MALTASE
AMINOPEPTIDASE N b
120
6
t
a
~ 6O
c
*
b
a, 20'
2O c
'?, be ~
a
\
,
0
ISOMALTASE
ALKALLNEPHOSPHATASE 30"
a,
4"
5.0-
0.6
A 9 o
~ 2.5
~- 15 B
2" "
%
,
0.3
~
? a
a
a[ 0
0
40
80
120
40
80
120
AGE (day)
40
80
120
40
00
120
AGE ( d a y )
Fig 1. Changes in the overall specific activities and activities per kg E L W of aminopeptidases A and N and alkaline phosphatase
Fig 2. Changes in the overall specific activities and the activities per kg E L W of lactase, maltase, and isomaltase in the whole
in the whole small intestine during development and weaning (means and standard errors, n = 5) ([2, p r e r u m i n a n t s ; II, ruminants), a, b . . . . : Within each group values bearing only unlike letters differed significantly (P -< 0.05). *Significant diff e r e n c e between preruminants and ruminants (P -< 0.05).
small intestine during development and weaning (means and standard errors, n = 5) (D, p r e r u m i n a n t s ; I , r u m i n a n t s ) , a, b, 9 . .: Within each group values bearing only unlike letters differed significantly (P -< 0.05). *Significant difference between preruminants and ruminants (P
