Energy and Nitrogen Utilization of High Versus Low Producing Dairy Cows1 R. L. BELYEA and M. W. ADAMS2 Department of Dairy Science University of Missouri Columbia 65211 ABSTRACT
(Key words: nittogen utilization, energy metabolism, efficiency)
Six high and 6 low producing cows were fed com silage, alfalfa hay, com, and soybean meal diets to evaluate the cow's ability to metabolize energy and N. High producers consumed more feed and gave more milk than low producers. Energy digestibility (.70), conversion of digestible to metabolizable energy (.90), and absorption of N (.70) were not different between groups. For low producers, heat production (249 kcallkg BW 75 ) and loss of metabolizable energy as heat (.62) were greater than for high producers (238 kCallkg BW·75 and .53), suggesting a less efficient intennediary metabolism of the fonner. Body composition was unaffected by tteatment. Body fat mobilized during periods I, 2, and 3 was replaced during period 4. Change in body energy (fat) and change in energy balance (calorimetric) data were in the same direction, but absolute values did not agree; change in energy as body fat lagged behind change in energy balance detennined by calorimetry. Body protein was used in early lactation and was replaced immediately in spite of negative energy balance; this suggests that protein (amino acids) may play a significant role in meeting short-tenn energy needs during the first few weeks of lactation.
INTRODUCTION
Received May 15, 19&9. Accepted October 12. 1989. IContribution of the Agricultwe Experiment SllItion. Approved by the director. Jownal Series Number 10833. 2Present address: Louisiana Technical University. PO Box 10198, T. S.. RustOll. LA 71272-0045. 1990 J Dairy Sci 73:1023-1030
High producing dairy cows must consume and digest large amounts of feed to provide nutrients for milk production. Many factors affect digestive efficiency and animal productivity. Amount of feed consumed has a major influence on digestibility (16, 17, 26). Type of dietary ingredients. physical form, nutrient concentrations (energy, protein. minerals, vitamins), and feeding sttategy (separate versus mixed ingredients, multiple feedings per day) also may affect digestion or productivity (8, 24). Use of metabolizable energy (ME) for maintenance or for milk energy is affected by forage:concentrate, VFA ratio or both (9. 25). Efficiency of use of ME by the lactating cow is affected by that which is partitioned into heat (maintenance) versus that which is partitioned into milk or into (from) body tissue (2). Thus, manipulating ME utilization (i.e.• reducing heat production loss) appears to be one avenue for increasing efficiency of milk production (2). Smith and Baldwin (23) and Baldwin et al. (2) suggested that, compared with nonlactating cows, lactating cows have increased hepatic, gut mucosal. and renal tissue masses and increased metabolic activity. Their data show that the lactating cow has an increased maintenance requirement associated with increase in tissue mass and increase in metabolic activity of these tissues. which are responsible for absorbing, synthesizing and interconverting the precursors of milk components. Auburn researchers (21) reported that high producers have higher plasma somatottopin concenttations than low producers. In very few studies have differences in the genetic ability to produce milk been related to utilization of nutrients. The objective of this research was to determine if high producers are more efficient in using energy and nittogen than low producers.
1023
1024
BELYEA AND ADAMS
MATERIALS AND METHODS
h postfeeding) on d I, 3, and 5 of collection using equipment and methods of Belyea et al. (5). A 3- to 4-L sample was taken in a rubber experiment 1 anesthesia bag during a 3.0-min sampling Six Holstein cows, 4 wk postpartum and in period. Gas samples were analyzed for 02, second or third lactation, were chosen from the C02, and Cl-4 concentrations (5). During adUniversity of Missouri-Columbia (UMC) dairy justment periods, animals were trained to gas herd. Three cows had previous DHI lactation coUection equipment and techniques to minirecords (305 d, twice daily milking, mature mize stress during collection periods. equivalent) that averaged 8124 kg (Highs, H) Cows were milked twice daily with a portaand three averaged 6574 kg (Lows, L). While ble bucket-type system. Two milk samples at the farm, they were fed blended diets of com were taken during the a.m. and two during the silage, chopped alfalfa hay, and concentrate and p.m. of each collection day; one set of samples were group-housed. They were housed at the was sent to the Missouri DHI milk testing metabolic facility on campus in tie stalls lined laboratory for milk fat analyses. The other set with rubber floor mats. A I2-h light: 12 h was composited by cow and a subsample was darkness schedule was maintained, and temper- frozen for protein and energy determination. At ature was kept at about 13°C. Water was al- the end of each collection period cows were ways available. washed; body composition was estimated with The experiment lasted 16 wk with four the Whole Body Counter. Our facility contains periods of 4 wk each. Each period had 3 wk of a 40K liquid scintillation detector and associadjusttnent, followed by 1 wk for input and ated data integrator, which were described earoutput measurements. lier (3, 4, 6). A blended diet of com silage, chopped alfalfa hay, and concentrate (com, soybean meal, Experiment 2 and minerals) was fed (Table 1). Propionic acid (1.5% wt/wt) was added during mixing to preSix lactating Holsteins (about 2 wk postparvent spoiling and to permit long-term storage. tum) were selected from the UMC dairy herd Feed was offered for ad libitum access to result and fed a blended diet of com silage, alfalfa in 10% refusal during the first period and to hay, and a com-soybean meal concentrate. meet NRC (20) recommendations for BW and Standardized DHI lactation records averaged milk yield for the remainder of the trial. Feeds 9036 kg for the H and 7830 for the L producwere offered in equal portions at 0700 and ers. The study consisted of four periods of 5 wk 1900 h. Intake was adjusted every 4 wk, depending upon milk yield and BW. each. For 3 wk of each period cows were kept During the 3 wk of adjustment, samples of at the dairy farm; they were group-housed (free feed were taken from each batch of blended stalls) and were fed their diets individually with feed. During the input and output measure- an electronic gate system. During the last 2 wk ments, samples of feed were taken daily. Feces of each period, cows were brought to the metawere collected daily in gutter pans, weighed, bolic facility; wk 1 was for adjustment and wk and sampled (l % wt/wt). Feed and fecal sam- 2 for collections. Both production groups were ples were dried at 50T, ground coarsely, fed the same diet, formulated from com silage, mixed thoroughly, and composited by animal alfalfa hay, and concentrate (com, soybean for the 5 d of collection. A subsample was meal, minerals, and vitamins) (Table 1). Propiground through a I.o-mm screen and used for onic acid was added to stabilize the feed. Diets analyses. Urine was collected via urinary cathe- were offered for ad libitum intake to give 10% ter, weighed, and sampled daily. Urine samples refusal during the first period and 110% of were composited for the 5 d of collection, and a NRC (20) recommendations, based on BW and subsample (iOO ml) was taken and frozen. Gas milk yield in the second and subsequent analyses are subject to sampling errors, analyti- periods. Feed allottnents were adjusted every 5 cal errors, and significant variation (5). To min- wk. Amounts and samples of feeds, feces, imize variation, we measured respiratory gas urine, milk, and gas were taken and processed volume at 1000, 1400, and 1800 h (3, 7, and 11 as in Experiment 1. Body composition was Journal of Dairy Science Vol. 73.
No.4, 1990
1025
ENERGY UTILIZATION VERSUS MILK YIELO TABLE I. Fonnulation and nutrient content of diets. Ingredient
Experiment I
Experiment 2
Com silage. % of diet OM Chopped alfalfa hay. % of diet OM Concentrate. % of diet OM Com. % of concentrate OM Soybean meal. % of concentrate OM Oicalciwn phosphate. % of concentrate OM Limestone. % of concentrate OM Dynamate. % of concentrate OM MgO, % of concentrate OM TMS + AOE. + % of concentrate OM NDF, % of diet OM ADF. % of diet OM Protein, % of diet OM Ca. % of diet OM P, % of diel OM Mg. % of diet DM K. % of diet OM
20.5 17.7 61.8 73.2 25.1 .4
24.5 30.6 44.9 63.7 30.8 1.1
.3 .2
.7 .6 .2 1.5
.1
.7
42.2
30.4 18.4 17.5 .61 .40 .26 1.12
22.6 17.7
.93 .56
.25 .92
ITrace-minerai sall plus vitamin A. O. and E premix.
detennined as in Experiment 1. In both experiments, feed and feces were analyzed for DM and detergent fiber (14). Nitrogen content of feeds, feces, urine, and milk: was detennined according to Watkins et al. (27). Energy content of feeds, feces, and urine was detennined using a calorimeter. Respiratory gases were analyzed for 02, C02, and Cf4 concentration (7) and heat production was estimated using Brouwer's equation (7). Body composition was estimated from 40K concentration (3, 4, 6). Data were analyzed statistically as a duplicated split plot in time (11, 22). The specific model was: Y
= j.l
+ Ei + Pj + T k + q(fk) + Tk x Pj + T k X Ei + Pj X Ei + T k X Ei X Pj + C(T x E).
where:
Y = expected response, j.l = mean response, Ei = effect of experiment i, Tk = effect of treatment k, Pj = effect of period j, CI(Tk) = effects of cow 1 within treatment k, Tk x Pj = treatment x period effects, Tk x Ei = treatment x experiment effects,
= period
x experiment effects,
= treatment =
x period x experiment effect, and cow within treatment x experiment.
Our original goal was to pool data across experiments, even though experiments varied in diet, stage of lactation of the cows, etc. There were no significant treatment x experiment interactions, thus allowing us to pool data as originally planned. RESULTS
Intake and Milk Production
Dietary fonnulations and chemical composition of the diets in each experiment are in Table 1. In Experiment 1, forage:concentrate was 38: 62; the diet appeared to be marginal in fiber for proper rumination, based upon NDF (30%) and ADF (18%) concentrations. In Experiment 2 forage:concentrate was increased to 55:45, raising NDF and ADF concentrations (Table 1). Diets were fonnulated to contain appropriate amounts of minerals and vitamins. The H cows consumed more feed (P
(Key words: nittogen utilization, energy metabolism, efficiency)
Six high and 6 low producing cows were fed com silage, alfalfa hay, com, and soybean meal diets to evaluate the cow's ability to metabolize energy and N. High producers consumed more feed and gave more milk than low producers. Energy digestibility (.70), conversion of digestible to metabolizable energy (.90), and absorption of N (.70) were not different between groups. For low producers, heat production (249 kcallkg BW 75 ) and loss of metabolizable energy as heat (.62) were greater than for high producers (238 kCallkg BW·75 and .53), suggesting a less efficient intennediary metabolism of the fonner. Body composition was unaffected by tteatment. Body fat mobilized during periods I, 2, and 3 was replaced during period 4. Change in body energy (fat) and change in energy balance (calorimetric) data were in the same direction, but absolute values did not agree; change in energy as body fat lagged behind change in energy balance detennined by calorimetry. Body protein was used in early lactation and was replaced immediately in spite of negative energy balance; this suggests that protein (amino acids) may play a significant role in meeting short-tenn energy needs during the first few weeks of lactation.
INTRODUCTION
Received May 15, 19&9. Accepted October 12. 1989. IContribution of the Agricultwe Experiment SllItion. Approved by the director. Jownal Series Number 10833. 2Present address: Louisiana Technical University. PO Box 10198, T. S.. RustOll. LA 71272-0045. 1990 J Dairy Sci 73:1023-1030
High producing dairy cows must consume and digest large amounts of feed to provide nutrients for milk production. Many factors affect digestive efficiency and animal productivity. Amount of feed consumed has a major influence on digestibility (16, 17, 26). Type of dietary ingredients. physical form, nutrient concentrations (energy, protein. minerals, vitamins), and feeding sttategy (separate versus mixed ingredients, multiple feedings per day) also may affect digestion or productivity (8, 24). Use of metabolizable energy (ME) for maintenance or for milk energy is affected by forage:concentrate, VFA ratio or both (9. 25). Efficiency of use of ME by the lactating cow is affected by that which is partitioned into heat (maintenance) versus that which is partitioned into milk or into (from) body tissue (2). Thus, manipulating ME utilization (i.e.• reducing heat production loss) appears to be one avenue for increasing efficiency of milk production (2). Smith and Baldwin (23) and Baldwin et al. (2) suggested that, compared with nonlactating cows, lactating cows have increased hepatic, gut mucosal. and renal tissue masses and increased metabolic activity. Their data show that the lactating cow has an increased maintenance requirement associated with increase in tissue mass and increase in metabolic activity of these tissues. which are responsible for absorbing, synthesizing and interconverting the precursors of milk components. Auburn researchers (21) reported that high producers have higher plasma somatottopin concenttations than low producers. In very few studies have differences in the genetic ability to produce milk been related to utilization of nutrients. The objective of this research was to determine if high producers are more efficient in using energy and nittogen than low producers.
1023
1024
BELYEA AND ADAMS
MATERIALS AND METHODS
h postfeeding) on d I, 3, and 5 of collection using equipment and methods of Belyea et al. (5). A 3- to 4-L sample was taken in a rubber experiment 1 anesthesia bag during a 3.0-min sampling Six Holstein cows, 4 wk postpartum and in period. Gas samples were analyzed for 02, second or third lactation, were chosen from the C02, and Cl-4 concentrations (5). During adUniversity of Missouri-Columbia (UMC) dairy justment periods, animals were trained to gas herd. Three cows had previous DHI lactation coUection equipment and techniques to minirecords (305 d, twice daily milking, mature mize stress during collection periods. equivalent) that averaged 8124 kg (Highs, H) Cows were milked twice daily with a portaand three averaged 6574 kg (Lows, L). While ble bucket-type system. Two milk samples at the farm, they were fed blended diets of com were taken during the a.m. and two during the silage, chopped alfalfa hay, and concentrate and p.m. of each collection day; one set of samples were group-housed. They were housed at the was sent to the Missouri DHI milk testing metabolic facility on campus in tie stalls lined laboratory for milk fat analyses. The other set with rubber floor mats. A I2-h light: 12 h was composited by cow and a subsample was darkness schedule was maintained, and temper- frozen for protein and energy determination. At ature was kept at about 13°C. Water was al- the end of each collection period cows were ways available. washed; body composition was estimated with The experiment lasted 16 wk with four the Whole Body Counter. Our facility contains periods of 4 wk each. Each period had 3 wk of a 40K liquid scintillation detector and associadjusttnent, followed by 1 wk for input and ated data integrator, which were described earoutput measurements. lier (3, 4, 6). A blended diet of com silage, chopped alfalfa hay, and concentrate (com, soybean meal, Experiment 2 and minerals) was fed (Table 1). Propionic acid (1.5% wt/wt) was added during mixing to preSix lactating Holsteins (about 2 wk postparvent spoiling and to permit long-term storage. tum) were selected from the UMC dairy herd Feed was offered for ad libitum access to result and fed a blended diet of com silage, alfalfa in 10% refusal during the first period and to hay, and a com-soybean meal concentrate. meet NRC (20) recommendations for BW and Standardized DHI lactation records averaged milk yield for the remainder of the trial. Feeds 9036 kg for the H and 7830 for the L producwere offered in equal portions at 0700 and ers. The study consisted of four periods of 5 wk 1900 h. Intake was adjusted every 4 wk, depending upon milk yield and BW. each. For 3 wk of each period cows were kept During the 3 wk of adjustment, samples of at the dairy farm; they were group-housed (free feed were taken from each batch of blended stalls) and were fed their diets individually with feed. During the input and output measure- an electronic gate system. During the last 2 wk ments, samples of feed were taken daily. Feces of each period, cows were brought to the metawere collected daily in gutter pans, weighed, bolic facility; wk 1 was for adjustment and wk and sampled (l % wt/wt). Feed and fecal sam- 2 for collections. Both production groups were ples were dried at 50T, ground coarsely, fed the same diet, formulated from com silage, mixed thoroughly, and composited by animal alfalfa hay, and concentrate (com, soybean for the 5 d of collection. A subsample was meal, minerals, and vitamins) (Table 1). Propiground through a I.o-mm screen and used for onic acid was added to stabilize the feed. Diets analyses. Urine was collected via urinary cathe- were offered for ad libitum intake to give 10% ter, weighed, and sampled daily. Urine samples refusal during the first period and 110% of were composited for the 5 d of collection, and a NRC (20) recommendations, based on BW and subsample (iOO ml) was taken and frozen. Gas milk yield in the second and subsequent analyses are subject to sampling errors, analyti- periods. Feed allottnents were adjusted every 5 cal errors, and significant variation (5). To min- wk. Amounts and samples of feeds, feces, imize variation, we measured respiratory gas urine, milk, and gas were taken and processed volume at 1000, 1400, and 1800 h (3, 7, and 11 as in Experiment 1. Body composition was Journal of Dairy Science Vol. 73.
No.4, 1990
1025
ENERGY UTILIZATION VERSUS MILK YIELO TABLE I. Fonnulation and nutrient content of diets. Ingredient
Experiment I
Experiment 2
Com silage. % of diet OM Chopped alfalfa hay. % of diet OM Concentrate. % of diet OM Com. % of concentrate OM Soybean meal. % of concentrate OM Oicalciwn phosphate. % of concentrate OM Limestone. % of concentrate OM Dynamate. % of concentrate OM MgO, % of concentrate OM TMS + AOE. + % of concentrate OM NDF, % of diet OM ADF. % of diet OM Protein, % of diet OM Ca. % of diet OM P, % of diel OM Mg. % of diet DM K. % of diet OM
20.5 17.7 61.8 73.2 25.1 .4
24.5 30.6 44.9 63.7 30.8 1.1
.3 .2
.7 .6 .2 1.5
.1
.7
42.2
30.4 18.4 17.5 .61 .40 .26 1.12
22.6 17.7
.93 .56
.25 .92
ITrace-minerai sall plus vitamin A. O. and E premix.
detennined as in Experiment 1. In both experiments, feed and feces were analyzed for DM and detergent fiber (14). Nitrogen content of feeds, feces, urine, and milk: was detennined according to Watkins et al. (27). Energy content of feeds, feces, and urine was detennined using a calorimeter. Respiratory gases were analyzed for 02, C02, and Cf4 concentration (7) and heat production was estimated using Brouwer's equation (7). Body composition was estimated from 40K concentration (3, 4, 6). Data were analyzed statistically as a duplicated split plot in time (11, 22). The specific model was: Y
= j.l
+ Ei + Pj + T k + q(fk) + Tk x Pj + T k X Ei + Pj X Ei + T k X Ei X Pj + C(T x E).
where:
Y = expected response, j.l = mean response, Ei = effect of experiment i, Tk = effect of treatment k, Pj = effect of period j, CI(Tk) = effects of cow 1 within treatment k, Tk x Pj = treatment x period effects, Tk x Ei = treatment x experiment effects,
= period
x experiment effects,
= treatment =
x period x experiment effect, and cow within treatment x experiment.
Our original goal was to pool data across experiments, even though experiments varied in diet, stage of lactation of the cows, etc. There were no significant treatment x experiment interactions, thus allowing us to pool data as originally planned. RESULTS
Intake and Milk Production
Dietary fonnulations and chemical composition of the diets in each experiment are in Table 1. In Experiment 1, forage:concentrate was 38: 62; the diet appeared to be marginal in fiber for proper rumination, based upon NDF (30%) and ADF (18%) concentrations. In Experiment 2 forage:concentrate was increased to 55:45, raising NDF and ADF concentrations (Table 1). Diets were fonnulated to contain appropriate amounts of minerals and vitamins. The H cows consumed more feed (P
