C h a n g i n g M e a l P a t t e r n s a n d S u p p r e s s i o n o f Feed I n t a k e w i t h
Increasing Amounts of Dietary Nonprotein Nitrogen in Ruminants ~ H. R. CONRAD Department of Dairy Science Ohio Agricultural Research and Development Center Wooster 44691 and C. A. BAILE 2 and J. MAYER 3 Department of Nutrition Harvard School of Public Health Boston, MA 02115 ABSTRACT
determined for mounting degrees of intoxication (25). In ruminants, ammonia may pass directly from the rumen into the portal system, a process which is pH dependent (15, 19). When ammonia concentration reached 30 /amole per ml or more in the rumen of lambs, ammonia concentration of peripheral blood increased (18). Acute conditions developed when ammonia was increased to between 60 and 90 /~moles per ml, resulting in severe disturbance of the central nervous system, tetany, and death. In sublethal ammonium intoxication, several physiological mechanisms have been impaired (25). Noteworthy are reduced feed intake (8, 12, 25) and diminished absorption of intermediary metabolites due to damaged intestinal tissue (25). In diets having an abundance of potential ammonium ions, such as ammonium salts, urea, or the salts of organic acids in ensiled forages, protection against intoxication may be afforded by reducing feed intake or changing meal pattern (11, 20, 25). Animals fed large amounts of urea ate smaller quantities of their daily intake at any one time and increased their frequency of eating (9, 11, 25). This leads to the inference that an animal is affected within the time lapsing during a single meal.
Goats were injected intraruminally during spontaneous meals with ammonium chloride, urea, ammonium lactate, or sodium lactate arranged in a Latin square experimental design randomized for order of treatments. Urea and ammonium injections shortened meal length by 20 to 30%. Rate of eating and meal frequency were reduced. Sodium lactate injections reduced meal size. In cows, meal length and meal size also were measured. Grain concentrate, corn silage, and chopped hay were fed as complete mixed rations. In the concentrates 58% of the nitrogen was either from soybean meal or urea. Length of the first meal after feeding was reduced from 24.3 min with soybean meal to 12.4 with urea. Meal size was reduced from 3.2 kg to 1.8 kg when urea was fed. Total feed intake was similar, 12.0 kg/day (soybean meal) and 11.6 kg/day (urea) since spontaneous meal number and size were 17 and .30 kg for soybean meal but increased to 23 and .36 kg for urea. The physiological basis for the limit on meal length with urea rations is unknown but is an important factor in successful feeding of urea when eating time is limited for cows. INTRODUCTION
The metabolic consequences of excessive ammonium ions in the digestive tract have been
Received April 12, 1977. 1Journal article No. 44-77, Ohio Agricultural
Research and DevelopmentCenter, Wooster 44691. 2 University of Pennsylvania, Kennett Square, PA 19348. 3Office of President, Tufts University, Medford, MA 02153. 1977 J Dairy Sci 60:1725--1733
Sensory evaluation of degradation products in silage appears to occur at some level of metabolism since feeding ensiled forages depressed feed intake (7). The cause and effect relationship is not known in this condition. One possibility is that the fermentation acids, lactic and acetic, depress feed consumption as the result of increased concentration of ruminal acids during meals since either acid when injected into the rumen concomitantly with meal ingestion depressed feed intake (4, 5). On the other hand, Thomas et al. (24) concluded that diminished intake of ensiled forages was
1725
1726
CONRAD ET AL.
associated with increased ammonium ions in ensiled feeds. More recently Clancy et al. (6) found that ammonia and organic acids accounted for only 40% of the depression of feed intake. Histamine and other amines could contribute as much to depressing feed intake in sheep as ammonia. In ruminants depressants of feed intake may be studied independently of their effect on the palatability component of regulation of feed intake by administering the material directly into the rumen. In this study we have investigated the importance of ammonium salts and urea relative to lactate as depressants of feed intake when they were injected directly into the rumen of goats during meals and to urea fed in the general diet of dairy cows. MATERIALS AND METHODS Experiment 1
Four goats, 40 kg in average weights, were prepared for experimental treatment as follows: 1) surgically prepared with ruminal fistula and fitted with a cannula with entry ports for injection; 2) allowed to adjust to the restraining stalls; and 3) adapted to the high concentrate diet (Omolene, Ralston Purina Company, St. Louis, MO) which contained mostly rolled grains and was 1.7% N. The goats were fed ad lib and were permitted to eat spontaneously. F o r t y grams of timothy hay were fed each goat daily at 0700 h. Treatment solutions were pumped (Model 1200 peristaltic pump, Harvard Apparatus) from graduated cylinders to the ruminal plug ports. Each goat when eating from the feed container ports broke a light beam impinging on a photo cell which in conjunction with relay switches activated the injection pump and event recorder. This permitted moni-
toring the time spent prehending feed and the injection of treatment solutions during spontaneous meals (3). Injection rates and treatments are listed in Table 1 for the first trial. A Latin square arrangement randomized for order of treatments and sequence of goats was used in the experiments. Each condition of the experiment was replicated by observing each goat for 2 consecutive days. Within treatment cells of the experimental design, the sequence of 2-day observations was control period, treatment period, and recovery period. Each goat received the treatments listed in Table I in replicated 2-day periods. Injections occurred during the time of eating only in the treatment period. Goats were allowed up to 7 days for recovery of pretreatment feed intake before subsequent treatments were initiated. In the second trial, the ammonium chloride treatment was repeated with two goats in four replications at one-half (3 meq N/min) the previous injection rate. In the final phase of experiment 1 injection rates were increased in individual goats to between 1 and 2 meq per gram of feed inducing severe toxicity. Since injections occurred only while goats were eating, amounts injected were computed for individual goats as milliequivalents of N/g DM. Experiment 2
With the aim of discerning further application of results in experiment 1, comparative effects of feeding urea or soybean meal (SBM) as the nitrogen and/or protein supplement were determined in lactating cows eating ad libitum with respect to time. Meal length, meal size, and intervals between meals were measured in mangers suspended on pressure transducers connected electronically to a recorder. The recorder was calibrated for
•TABLE 1. Treatments and planned injection rates.
Treatment
Goats
Observations
Ammonium chloride Ammonium chloride Urea Sodium lactate Ammonium lactate
4 2 4 4 4
8 8 8 8 8
Journal of Dairy Science Vol. 60, No. 11, 1977
pH
Planned intraruminal injection rate
6.0 6.0 6.0 4.4 4.4
6 meq N/min 3 meq N/min 6 meq N/min 6 meq lactate/min 6 meq lactate/min
UREA AND MEAL PATTERNS linear changes with increasing weight up t o 25 kg, and precision of a single measurement on feed consumption was about + 50 g. A decreasing voltage signified the amount of feed eaten per minute. Variability from coincidental pressures on the manger during eating clearly defined the period of meals, and the a m o u n t and rate consumed were determined from the slope and mean difference. A minimum meal size of 100 g and a minimum intermeal interval of 2 min were arbitrary criteria for defining meals. Minimum intermeal intervals used for sheep and goats have been 10 and 20 min (2, 26). The short intermeal interval was used in experiment 2 because the rate of eating, 19 mg/min per kg weight, in eating bouts occurring 2 to 5 min after a previous bout was above the average for all other spontaneous meals. Two lactating cows weighing 449 and 533 kg were used in switchback trials. The feeding pattern was monitored in each cow during five 24-h periods. After change in source of nitrogen, adjustment periods of 9 to 11 days were allowed before recording meal pattern. The concentrates (Table 2) were similar except for source of nitrogen. Fifty-eight percent of the supplemental nitrogen in the concentrate portion of the diet was either from soybean meal or a combination of 33% urea and 67% dehydrated alfalfa meal. In the urea-dehy ration urea comprised 1.3% of the total dry matter. One part concentrate was mixed at feeding with one part corn silage and one part chopped hay
TABLE 2. Composition of rations in a diet composed of concentrates containing urea or soybean meal, corn silage, and hay (orchardgrass). Urea
Concentrate Corn silage Hay Nitrogen content Urea content
SBM
(% of dry matter) 42.8a 42.8 b 17.2 17.2 4O.0 40.0 2.6 2.6 t.3
...
aurea concentrate contained 50% corn, 37.4% oats, 6% alfalfa meal, 3% urea, 2.0% dicalcium phosphate, and .6% salt. bSBM concentrate contained 50% corn, 21.0% oats, 27.4% soybean meal, 1.0% dicalcium phosphate, and .6% salt.
1727
(orchard grass, 2.1% N). The mixture was fed as a complete ration twice daily. The contribution of the two sources of nitrogen to the amount of ammonia was determined in separate complementary experiments. The concentration of ruminal ammoniacal N was measured in two fistulated cows at 15-rain intervals during an initial feeding period. The lactating cows were eating 14.5 and 15.3 kg of dry matter and weighed 582 and 636 kg, respectively. Trials were replicated for each of the nitrogen sources, SBM and urea. Samples of rumen content were taken from dorsal anterior, dorsal posterior, ventral posterior, and ventral anterior regions, composited by volume, acidified with metaphosphoric acid to a concentration of 5% acid, and clarified by centrifugation. The colorimetric method of Fawcett and Scott (10) was adapted for ammonia determinations with modifications cited in (21, 22). R ESU LTS
A summary of results of experiment 1 is in Table 3. Among the four compounds injected, ammonia chloride depressed feed intake most severely. Feed intake was reduced markedly in goats receiving more than .5 mmole of ammonium chloride per g of feed, and hypophagia persisted in all goats after a 2-day treatment was completed. Two goats are little for 7 days and eventually succumbed from respiratory infections. Feed intake in the recovery period (2 days post treatment) was only 27% of normal feed consumption. The reduction in feed intake was the consequence of fewer meals per day, a slower rate of eating, and shorter length of time per meal; but average amount of time spent consuming a meal returned to normal immediately on cessation of the ammonium chloride injection. When the injection rate was changed from 6 to 3 meq of N per min in the second trial, feed intake was n o t suppressed significantly. Intraruminal urea injections also depressed feed intake but only when nitrogen injections were equivalent to at least 1.1 mmole of ammonia per g of feed consumed (Fig. 1). This was double the amount required for intoxication effects with ammonium chloride and occurred at a point equivalent to a feeding rate of 3.8% of the dietary dry matter as urea. Average meal length was reduced markedly from 9.1 Journal of Dairy Science Vol. 60, No. 11, 1977
TABLE 3. Changes in meal patterns associated with injections o f a m m o n i u m chloride, urea, a m m o n i u m lactate, or s o d i u m lactate intraruminally into goats during s p o n t a n e o u s meals.
ba 0o
Treatment ~"
Period and observation Injection rates, m e q / g c Observations, no. Grain intake Control, g / d Treatment, g/d Recovery, g/d
Rate of eating Control, g / m i n Treatment, g/rain Recovery, g/rain
Meals Control, n o / d Treatment, n o / d Recovery, n o / d
Time per meal Control, m i n Treatment, min Recovery, min
A m m o n i u m chloride (6 mmole)
(3 m m o l e a )
.94
.38
8
932 e 600Y 247 x
Urea (3 m m o l e b)
8
1253 1115 1160
10.0 x 9.6 x 4.1Y
12.2 x 8.5Y 7.8Y
7.73 x
7.28 x 9.28Y
17.2 16.9 17.3
10.0 9.3 10.0
7.39 6.44 7.35
.79 8
912 795 904 (SEd = 108, n = 8)
783 x 521Y 877Y
12.9 x 7.6Y 8.4Y
11.0 10.5 12.0 (SE = 1.2, n = 8)
10.6 9.9 11.7
9.05 x 6.65Y 8.51 x (SE = .84, n = 8)
aAdditional observations at the conclusion o f e x p e r i m e n t . CInjections were made during " t r e a t m e n t " period only. Milliequivalents o f nitrogen or lactate per g r a m o f feed eaten. eMeans having different letters as superscripts were different, P
Increasing Amounts of Dietary Nonprotein Nitrogen in Ruminants ~ H. R. CONRAD Department of Dairy Science Ohio Agricultural Research and Development Center Wooster 44691 and C. A. BAILE 2 and J. MAYER 3 Department of Nutrition Harvard School of Public Health Boston, MA 02115 ABSTRACT
determined for mounting degrees of intoxication (25). In ruminants, ammonia may pass directly from the rumen into the portal system, a process which is pH dependent (15, 19). When ammonia concentration reached 30 /amole per ml or more in the rumen of lambs, ammonia concentration of peripheral blood increased (18). Acute conditions developed when ammonia was increased to between 60 and 90 /~moles per ml, resulting in severe disturbance of the central nervous system, tetany, and death. In sublethal ammonium intoxication, several physiological mechanisms have been impaired (25). Noteworthy are reduced feed intake (8, 12, 25) and diminished absorption of intermediary metabolites due to damaged intestinal tissue (25). In diets having an abundance of potential ammonium ions, such as ammonium salts, urea, or the salts of organic acids in ensiled forages, protection against intoxication may be afforded by reducing feed intake or changing meal pattern (11, 20, 25). Animals fed large amounts of urea ate smaller quantities of their daily intake at any one time and increased their frequency of eating (9, 11, 25). This leads to the inference that an animal is affected within the time lapsing during a single meal.
Goats were injected intraruminally during spontaneous meals with ammonium chloride, urea, ammonium lactate, or sodium lactate arranged in a Latin square experimental design randomized for order of treatments. Urea and ammonium injections shortened meal length by 20 to 30%. Rate of eating and meal frequency were reduced. Sodium lactate injections reduced meal size. In cows, meal length and meal size also were measured. Grain concentrate, corn silage, and chopped hay were fed as complete mixed rations. In the concentrates 58% of the nitrogen was either from soybean meal or urea. Length of the first meal after feeding was reduced from 24.3 min with soybean meal to 12.4 with urea. Meal size was reduced from 3.2 kg to 1.8 kg when urea was fed. Total feed intake was similar, 12.0 kg/day (soybean meal) and 11.6 kg/day (urea) since spontaneous meal number and size were 17 and .30 kg for soybean meal but increased to 23 and .36 kg for urea. The physiological basis for the limit on meal length with urea rations is unknown but is an important factor in successful feeding of urea when eating time is limited for cows. INTRODUCTION
The metabolic consequences of excessive ammonium ions in the digestive tract have been
Received April 12, 1977. 1Journal article No. 44-77, Ohio Agricultural
Research and DevelopmentCenter, Wooster 44691. 2 University of Pennsylvania, Kennett Square, PA 19348. 3Office of President, Tufts University, Medford, MA 02153. 1977 J Dairy Sci 60:1725--1733
Sensory evaluation of degradation products in silage appears to occur at some level of metabolism since feeding ensiled forages depressed feed intake (7). The cause and effect relationship is not known in this condition. One possibility is that the fermentation acids, lactic and acetic, depress feed consumption as the result of increased concentration of ruminal acids during meals since either acid when injected into the rumen concomitantly with meal ingestion depressed feed intake (4, 5). On the other hand, Thomas et al. (24) concluded that diminished intake of ensiled forages was
1725
1726
CONRAD ET AL.
associated with increased ammonium ions in ensiled feeds. More recently Clancy et al. (6) found that ammonia and organic acids accounted for only 40% of the depression of feed intake. Histamine and other amines could contribute as much to depressing feed intake in sheep as ammonia. In ruminants depressants of feed intake may be studied independently of their effect on the palatability component of regulation of feed intake by administering the material directly into the rumen. In this study we have investigated the importance of ammonium salts and urea relative to lactate as depressants of feed intake when they were injected directly into the rumen of goats during meals and to urea fed in the general diet of dairy cows. MATERIALS AND METHODS Experiment 1
Four goats, 40 kg in average weights, were prepared for experimental treatment as follows: 1) surgically prepared with ruminal fistula and fitted with a cannula with entry ports for injection; 2) allowed to adjust to the restraining stalls; and 3) adapted to the high concentrate diet (Omolene, Ralston Purina Company, St. Louis, MO) which contained mostly rolled grains and was 1.7% N. The goats were fed ad lib and were permitted to eat spontaneously. F o r t y grams of timothy hay were fed each goat daily at 0700 h. Treatment solutions were pumped (Model 1200 peristaltic pump, Harvard Apparatus) from graduated cylinders to the ruminal plug ports. Each goat when eating from the feed container ports broke a light beam impinging on a photo cell which in conjunction with relay switches activated the injection pump and event recorder. This permitted moni-
toring the time spent prehending feed and the injection of treatment solutions during spontaneous meals (3). Injection rates and treatments are listed in Table 1 for the first trial. A Latin square arrangement randomized for order of treatments and sequence of goats was used in the experiments. Each condition of the experiment was replicated by observing each goat for 2 consecutive days. Within treatment cells of the experimental design, the sequence of 2-day observations was control period, treatment period, and recovery period. Each goat received the treatments listed in Table I in replicated 2-day periods. Injections occurred during the time of eating only in the treatment period. Goats were allowed up to 7 days for recovery of pretreatment feed intake before subsequent treatments were initiated. In the second trial, the ammonium chloride treatment was repeated with two goats in four replications at one-half (3 meq N/min) the previous injection rate. In the final phase of experiment 1 injection rates were increased in individual goats to between 1 and 2 meq per gram of feed inducing severe toxicity. Since injections occurred only while goats were eating, amounts injected were computed for individual goats as milliequivalents of N/g DM. Experiment 2
With the aim of discerning further application of results in experiment 1, comparative effects of feeding urea or soybean meal (SBM) as the nitrogen and/or protein supplement were determined in lactating cows eating ad libitum with respect to time. Meal length, meal size, and intervals between meals were measured in mangers suspended on pressure transducers connected electronically to a recorder. The recorder was calibrated for
•TABLE 1. Treatments and planned injection rates.
Treatment
Goats
Observations
Ammonium chloride Ammonium chloride Urea Sodium lactate Ammonium lactate
4 2 4 4 4
8 8 8 8 8
Journal of Dairy Science Vol. 60, No. 11, 1977
pH
Planned intraruminal injection rate
6.0 6.0 6.0 4.4 4.4
6 meq N/min 3 meq N/min 6 meq N/min 6 meq lactate/min 6 meq lactate/min
UREA AND MEAL PATTERNS linear changes with increasing weight up t o 25 kg, and precision of a single measurement on feed consumption was about + 50 g. A decreasing voltage signified the amount of feed eaten per minute. Variability from coincidental pressures on the manger during eating clearly defined the period of meals, and the a m o u n t and rate consumed were determined from the slope and mean difference. A minimum meal size of 100 g and a minimum intermeal interval of 2 min were arbitrary criteria for defining meals. Minimum intermeal intervals used for sheep and goats have been 10 and 20 min (2, 26). The short intermeal interval was used in experiment 2 because the rate of eating, 19 mg/min per kg weight, in eating bouts occurring 2 to 5 min after a previous bout was above the average for all other spontaneous meals. Two lactating cows weighing 449 and 533 kg were used in switchback trials. The feeding pattern was monitored in each cow during five 24-h periods. After change in source of nitrogen, adjustment periods of 9 to 11 days were allowed before recording meal pattern. The concentrates (Table 2) were similar except for source of nitrogen. Fifty-eight percent of the supplemental nitrogen in the concentrate portion of the diet was either from soybean meal or a combination of 33% urea and 67% dehydrated alfalfa meal. In the urea-dehy ration urea comprised 1.3% of the total dry matter. One part concentrate was mixed at feeding with one part corn silage and one part chopped hay
TABLE 2. Composition of rations in a diet composed of concentrates containing urea or soybean meal, corn silage, and hay (orchardgrass). Urea
Concentrate Corn silage Hay Nitrogen content Urea content
SBM
(% of dry matter) 42.8a 42.8 b 17.2 17.2 4O.0 40.0 2.6 2.6 t.3
...
aurea concentrate contained 50% corn, 37.4% oats, 6% alfalfa meal, 3% urea, 2.0% dicalcium phosphate, and .6% salt. bSBM concentrate contained 50% corn, 21.0% oats, 27.4% soybean meal, 1.0% dicalcium phosphate, and .6% salt.
1727
(orchard grass, 2.1% N). The mixture was fed as a complete ration twice daily. The contribution of the two sources of nitrogen to the amount of ammonia was determined in separate complementary experiments. The concentration of ruminal ammoniacal N was measured in two fistulated cows at 15-rain intervals during an initial feeding period. The lactating cows were eating 14.5 and 15.3 kg of dry matter and weighed 582 and 636 kg, respectively. Trials were replicated for each of the nitrogen sources, SBM and urea. Samples of rumen content were taken from dorsal anterior, dorsal posterior, ventral posterior, and ventral anterior regions, composited by volume, acidified with metaphosphoric acid to a concentration of 5% acid, and clarified by centrifugation. The colorimetric method of Fawcett and Scott (10) was adapted for ammonia determinations with modifications cited in (21, 22). R ESU LTS
A summary of results of experiment 1 is in Table 3. Among the four compounds injected, ammonia chloride depressed feed intake most severely. Feed intake was reduced markedly in goats receiving more than .5 mmole of ammonium chloride per g of feed, and hypophagia persisted in all goats after a 2-day treatment was completed. Two goats are little for 7 days and eventually succumbed from respiratory infections. Feed intake in the recovery period (2 days post treatment) was only 27% of normal feed consumption. The reduction in feed intake was the consequence of fewer meals per day, a slower rate of eating, and shorter length of time per meal; but average amount of time spent consuming a meal returned to normal immediately on cessation of the ammonium chloride injection. When the injection rate was changed from 6 to 3 meq of N per min in the second trial, feed intake was n o t suppressed significantly. Intraruminal urea injections also depressed feed intake but only when nitrogen injections were equivalent to at least 1.1 mmole of ammonia per g of feed consumed (Fig. 1). This was double the amount required for intoxication effects with ammonium chloride and occurred at a point equivalent to a feeding rate of 3.8% of the dietary dry matter as urea. Average meal length was reduced markedly from 9.1 Journal of Dairy Science Vol. 60, No. 11, 1977
TABLE 3. Changes in meal patterns associated with injections o f a m m o n i u m chloride, urea, a m m o n i u m lactate, or s o d i u m lactate intraruminally into goats during s p o n t a n e o u s meals.
ba 0o
Treatment ~"
Period and observation Injection rates, m e q / g c Observations, no. Grain intake Control, g / d Treatment, g/d Recovery, g/d
Rate of eating Control, g / m i n Treatment, g/rain Recovery, g/rain
Meals Control, n o / d Treatment, n o / d Recovery, n o / d
Time per meal Control, m i n Treatment, min Recovery, min
A m m o n i u m chloride (6 mmole)
(3 m m o l e a )
.94
.38
8
932 e 600Y 247 x
Urea (3 m m o l e b)
8
1253 1115 1160
10.0 x 9.6 x 4.1Y
12.2 x 8.5Y 7.8Y
7.73 x
7.28 x 9.28Y
17.2 16.9 17.3
10.0 9.3 10.0
7.39 6.44 7.35
.79 8
912 795 904 (SEd = 108, n = 8)
783 x 521Y 877Y
12.9 x 7.6Y 8.4Y
11.0 10.5 12.0 (SE = 1.2, n = 8)
10.6 9.9 11.7
9.05 x 6.65Y 8.51 x (SE = .84, n = 8)
aAdditional observations at the conclusion o f e x p e r i m e n t . CInjections were made during " t r e a t m e n t " period only. Milliequivalents o f nitrogen or lactate per g r a m o f feed eaten. eMeans having different letters as superscripts were different, P
