INFLUENCE OF DIETARY ENERGY DURING GESTATION ON LAMBING PERFORMANCE, AND GLUCOSE METABOLISM IN FINN-CROSS EWES 1,2
U.S. Department of Agriculture s and University o f Nebraska, Clay Center, NE 68933
SUMMARY
The effect of three levels of dietary energy on maternal glucose metabolism, fetal liver and heart glycogen, DNA, RNA and protein concentrations and early neonatal survival was studied in 227, 2- and 3-year-old Finnish Landrace crossbred (1/2) ewes. Increasing the level of dietary energy intake during late gestation increased average lamb birth weight, ewe plasma glucose and insulin, and decreased plasma free fatty acids. Rates of glucose appearance were lower in ewes fed the low dietary energy level than in ewes fed the medium or the high energy level. Plasma glucose and glucose appearance rates tended to increase during an intravenous infusion of propionate (1 mmole/min) in ewes fed the low energy level but not in ewes fed the medium or the high energy level. Ewe plasma glucose increased approximately threefold within 30 min after parturition. Lambs born to ewes fed the low energy level had a lower concentration of liver DNA, but level of dietary energy did not significantly affect heart DNA concentrations nor liver or heart tissue concentrations of RNA, protein, or glycogen. Level of dietary energy during late gestation did
1Published as Paper Number 5043, Journal Series, Nebraska Agricultural Experiment Station, Lincoln. 2The authors wish to express appreciation to Ms. B. DeChiaro, Ms. M. Chambers, Ms. S. Schiefelbein, Mr. P. Ziemba and Mr. T. Katen for assistance with the laboratory analyses; to Mr. B. Knapp for assistance with statistical analyses and in the development of the computer programs used to evaluate glucoregulatory responses; and to Mr. B. Larsen and Mr. R. Kouba for the care of the experimental animals. a U.S. Meat Animal Research Center, Agricultural Research Service. 4Department of Animal Science, University of Nebraska, U.S. Meat Animal Research Center. s Mention of a trade name, proprietary product, o r specific equipment does not constitute a guarantee or warranty by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.
not significantly alter early neonatal survival of lambs. However, lambs born as triplets had lighter birth weights and a decreased survival at weaning than lambs born as singles. (Key Words: Energy, Glucose, Insulin, Pregnancy, Sheep.)
INTRODUCTION
Experiments have shown that nutritional treatments resulting in subnormal live-weight gain in the ewe during the last 6 to 8 weeks of pregnancy cause a reduction in the birth weight of Iambs, particularly twin lambs (Wallace, 1948; Gardner and Hogue, 1963; Treacher, 1970; Thomson and Thomson, 1973). Thus, nutritional considerations appear to be of increased importance for proper intrauterine development of multiple fetuses. We do not know whether the decrease in birth weights due to decreased nutrient intake influences intrauterine fetal development to such an extent that neonatal lamb survival is altered. Glycogen may be of vital importance to the fetus and new-born animal since it is a primary energy reserve in the fetus. In early gestation very little glycogen is present in liver and skeletal muscle of the fetus, but in late gestation, glycogen increases quite rapidly and in liver of the fetus reaches at least twice adult concentrations. The rapid decline in tissue glycogen in new-born animals suggests that both liver glycogen and skeletal muscle glycogen are important energy sources for use immediately after birth. Lambs from ewes on a low plane of nutrition are less able to maintain their body temperature at birth (Alexander et al., 1956) and probably have less muscle glycogen than lambs from ewes on a high plane of nutrition. We do not know the extent to which maternal dietary energy intake can influence fetal energy stores (such as glycogen). The objectives of these experiments were to determine (1) the effect of maternal dietary
1114 JOURNAL OF ANIMAL SCIENCE, Vol. 43, No. 5 (1976)
Downloaded from https://academic.oup.com/jas/article-abstract/43/5/1114/4697297 by Iowa State University user on 23 January 2019
R. L. Prior 3 and R. K. Christenson4
LAMBING PERFORMANCE AND GLUCOSE METABOLISM IN EWES energy level on maternal glucose entry rate and fetal energy reserves and (2) the extent to which maternal dietary energy level and lamb energy reserves at birth affect early neonatal survival.
Beginning on October 17, 66 2-year-old Finn-Targhee cross (1/2) and 161 3-year-old Finn-cross ewes previously described by Christenson et al. (1976) were bred to Suffolk rams. All rams were equipped with marking harnesses and crayons; breeding marks were recorded three times weekly. After the breeding season, ewes were moved to grass pasture that was supplemented with alfalfa hay. On January 13, approximately 50 ewes were palpated for pregnancy by rectal-abdominal palpation (Hulet, 1972). All ewes were shorn before weighing and assigning to treatment. At lambing the third lamb of those born as triplets was reared artificially in a nursery. Thus, with only a few exceptions, no ewe raised more than two lambs. Experiment I. On January 15, a total of 36 3-year-old ewes, previously diagnosed as pregnant, were assigned to one of three dietary treatments (table 1). The ewes were housed indoors in an unheated building in individual
1.2- • 1.2-m pens with expanded metal floors and fed 1.06, 1.61 and 2.19 kg/ewe/day (as fed basis) for energy treatments 1 (low), 2 (medium), and 3 (high), respectively. After 4 days on experimental rations, quantitites fed of all treatments were reduced to .71, 1.31 and 1.89 kg/ewe/day for treatments 1, 2 and 3, respectively. These quantities of rations for treatments 1, 2 and 3 provided approximately 60, 100 and 140%, respectively, of the recommended daily digestible energy requirements of ewes during the last 6 weeks of gestation (N.R.C., 1968) and equal amounts of protein, calcium and phosphorus. Treatment 3 approximated ad libitum consumption. Feed not consumed was weighed back daily. All ewes were weighed on January 15 and February 12 (Period 1) which corresponded to approximately day 81 and day 109 of gestation, respectively. Blood samples were collected from the jugular vein from all ewes before feeding on February 5 and February 25 which were approximately day 102 and day 122 of gestation, respectively. In addition, jugular blood samples were collected from 23 ewes and 34 lambs within 30 rain after lambing and before the lambs nursed. Liver and heart samples were obtained from 34 lambs within 30 rain after
TABLE 1. COMPOSITIONOF RATIONS FED TO PREGNANT EWES
Item Ration composition, % of dry matter Alfalfa, hay, S-C grnd, (1) Corn, yellow, grain, grnd, (4) Soybean, seeds, grnd, max 7% fiber, solv-extd, (5) Limestone, grnd, mn 33% calcium (6) Calcium phosphate, dibasic, commercial, (6) Trace mineral salta Nutrient analysis, % of dry matter Dry matterb Crude proteinb Digestible energy (keal/kg)c Cac pc
International Reference No.
1~0-111 4~2~92 5~4~04 6~2~32 6~1~80
Low
49.7 24.7 22.4 "il4 1.9
Energy level Medium
High
33.6 56.4 7.8
25.5 73.0
~4 .5
" " .'6
1.3
... 1.0
100.0
100.0
100.0
87.7 23.5 3878 1.10 964
87.6 16.1 3873 .74 .43
87.6 11.3 3889 .54 .32
aprovided in addition to NaCI the following as a percentage of the salt mix: iodine, .007; manganese, .24; iron, .24; magnesium, .05 ; copper, .032; cobalt, .001 ; and zinc, .005. bLaboratory determinations. CCalculated from feed composition tables (National Academy of Science -- Atlas of nutritional data on United States and Canadian Feeds).
Downloaded from https://academic.oup.com/jas/article-abstract/43/5/1114/4697297 by Iowa State University user on 23 January 2019
EXPERIMENTAL METHODS
1115
1116
PRIOR AND CHRISTENSON TABLE 2. EFFECT OF DIETARY ENERGY LEVEL ON EWE PLASMA GLUCOSE, INSULIN AND FREE FATTY ACIDS, WEIGHT GAINS AND NUMBER AND WEIGHT OF LAMBS BORN TO FINN-CROSS EWES (EXP. 1) Dietary energylevel Lo w
Nutrient intake a Total feed, g/ewe/day Dry matter, g/ewe/day Digestible energy, Mcal/ewe/day Crude protein, g/ewe/day Ca, g/ewe/day P, g/ewe/day
776 f 681 2.6 182 8.5 5.0
Medium
1319 g 1155 4.5 212 8.7 5.0
High
SE
1704 h 1497 5.8 193 8.2 4.9
44.1
Ewe weight Initial weight, kgb Gain, kgc
59.4 .48 f
59.3 3.88g
59.5 7.86 h
.50 .64
Lambing date d No. ewes lambing No. lambs born alive Avg lamb birth weight, kg Total lamb birth weight, kg
11 2.17 3.53 f 7.54
12 2.27 4.03g 8.86
11 2.0 4.97 h 9.17
.21 .26 .67
Ewe plasma glucose, mg/lO0 ml Day 102 of gestation Day 122 of gestation Average Iambinge
43.0 f 37.9 f 163.9
50.4g 44.8 f 155.3
59.1 h 61.4g 112.7
1.6 3.2 18.2
Ewe plasma insulin, ng/ml Day 102 of gestation Day 122 of gestation After lambinge
.59 f .74 f 1.67
1.20g .93 f 5.80
1.44g 2.52g 4.68
.12 .17 2.49
Ewe plasma free fatty acids, #moles/ml Day 102 of gestation Day 122 of gestation After lambinge
1.06g 1.51 2.09
.64 f 1.31 1.93
.61 f 1.16 2.00
.08 .13 .22
aAverage intake (on as fed basis) from January 15 through day of lambing. bEwes were started on their dietary treatments on January 15 (approximately day 81 of gestation). Cperiod 1 ; Day 81 through 109 of gestation. dExpressed as per ewe lambing. f'g'hMeans without a common superscript differ (P
U.S. Department of Agriculture s and University o f Nebraska, Clay Center, NE 68933
SUMMARY
The effect of three levels of dietary energy on maternal glucose metabolism, fetal liver and heart glycogen, DNA, RNA and protein concentrations and early neonatal survival was studied in 227, 2- and 3-year-old Finnish Landrace crossbred (1/2) ewes. Increasing the level of dietary energy intake during late gestation increased average lamb birth weight, ewe plasma glucose and insulin, and decreased plasma free fatty acids. Rates of glucose appearance were lower in ewes fed the low dietary energy level than in ewes fed the medium or the high energy level. Plasma glucose and glucose appearance rates tended to increase during an intravenous infusion of propionate (1 mmole/min) in ewes fed the low energy level but not in ewes fed the medium or the high energy level. Ewe plasma glucose increased approximately threefold within 30 min after parturition. Lambs born to ewes fed the low energy level had a lower concentration of liver DNA, but level of dietary energy did not significantly affect heart DNA concentrations nor liver or heart tissue concentrations of RNA, protein, or glycogen. Level of dietary energy during late gestation did
1Published as Paper Number 5043, Journal Series, Nebraska Agricultural Experiment Station, Lincoln. 2The authors wish to express appreciation to Ms. B. DeChiaro, Ms. M. Chambers, Ms. S. Schiefelbein, Mr. P. Ziemba and Mr. T. Katen for assistance with the laboratory analyses; to Mr. B. Knapp for assistance with statistical analyses and in the development of the computer programs used to evaluate glucoregulatory responses; and to Mr. B. Larsen and Mr. R. Kouba for the care of the experimental animals. a U.S. Meat Animal Research Center, Agricultural Research Service. 4Department of Animal Science, University of Nebraska, U.S. Meat Animal Research Center. s Mention of a trade name, proprietary product, o r specific equipment does not constitute a guarantee or warranty by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.
not significantly alter early neonatal survival of lambs. However, lambs born as triplets had lighter birth weights and a decreased survival at weaning than lambs born as singles. (Key Words: Energy, Glucose, Insulin, Pregnancy, Sheep.)
INTRODUCTION
Experiments have shown that nutritional treatments resulting in subnormal live-weight gain in the ewe during the last 6 to 8 weeks of pregnancy cause a reduction in the birth weight of Iambs, particularly twin lambs (Wallace, 1948; Gardner and Hogue, 1963; Treacher, 1970; Thomson and Thomson, 1973). Thus, nutritional considerations appear to be of increased importance for proper intrauterine development of multiple fetuses. We do not know whether the decrease in birth weights due to decreased nutrient intake influences intrauterine fetal development to such an extent that neonatal lamb survival is altered. Glycogen may be of vital importance to the fetus and new-born animal since it is a primary energy reserve in the fetus. In early gestation very little glycogen is present in liver and skeletal muscle of the fetus, but in late gestation, glycogen increases quite rapidly and in liver of the fetus reaches at least twice adult concentrations. The rapid decline in tissue glycogen in new-born animals suggests that both liver glycogen and skeletal muscle glycogen are important energy sources for use immediately after birth. Lambs from ewes on a low plane of nutrition are less able to maintain their body temperature at birth (Alexander et al., 1956) and probably have less muscle glycogen than lambs from ewes on a high plane of nutrition. We do not know the extent to which maternal dietary energy intake can influence fetal energy stores (such as glycogen). The objectives of these experiments were to determine (1) the effect of maternal dietary
1114 JOURNAL OF ANIMAL SCIENCE, Vol. 43, No. 5 (1976)
Downloaded from https://academic.oup.com/jas/article-abstract/43/5/1114/4697297 by Iowa State University user on 23 January 2019
R. L. Prior 3 and R. K. Christenson4
LAMBING PERFORMANCE AND GLUCOSE METABOLISM IN EWES energy level on maternal glucose entry rate and fetal energy reserves and (2) the extent to which maternal dietary energy level and lamb energy reserves at birth affect early neonatal survival.
Beginning on October 17, 66 2-year-old Finn-Targhee cross (1/2) and 161 3-year-old Finn-cross ewes previously described by Christenson et al. (1976) were bred to Suffolk rams. All rams were equipped with marking harnesses and crayons; breeding marks were recorded three times weekly. After the breeding season, ewes were moved to grass pasture that was supplemented with alfalfa hay. On January 13, approximately 50 ewes were palpated for pregnancy by rectal-abdominal palpation (Hulet, 1972). All ewes were shorn before weighing and assigning to treatment. At lambing the third lamb of those born as triplets was reared artificially in a nursery. Thus, with only a few exceptions, no ewe raised more than two lambs. Experiment I. On January 15, a total of 36 3-year-old ewes, previously diagnosed as pregnant, were assigned to one of three dietary treatments (table 1). The ewes were housed indoors in an unheated building in individual
1.2- • 1.2-m pens with expanded metal floors and fed 1.06, 1.61 and 2.19 kg/ewe/day (as fed basis) for energy treatments 1 (low), 2 (medium), and 3 (high), respectively. After 4 days on experimental rations, quantitites fed of all treatments were reduced to .71, 1.31 and 1.89 kg/ewe/day for treatments 1, 2 and 3, respectively. These quantities of rations for treatments 1, 2 and 3 provided approximately 60, 100 and 140%, respectively, of the recommended daily digestible energy requirements of ewes during the last 6 weeks of gestation (N.R.C., 1968) and equal amounts of protein, calcium and phosphorus. Treatment 3 approximated ad libitum consumption. Feed not consumed was weighed back daily. All ewes were weighed on January 15 and February 12 (Period 1) which corresponded to approximately day 81 and day 109 of gestation, respectively. Blood samples were collected from the jugular vein from all ewes before feeding on February 5 and February 25 which were approximately day 102 and day 122 of gestation, respectively. In addition, jugular blood samples were collected from 23 ewes and 34 lambs within 30 rain after lambing and before the lambs nursed. Liver and heart samples were obtained from 34 lambs within 30 rain after
TABLE 1. COMPOSITIONOF RATIONS FED TO PREGNANT EWES
Item Ration composition, % of dry matter Alfalfa, hay, S-C grnd, (1) Corn, yellow, grain, grnd, (4) Soybean, seeds, grnd, max 7% fiber, solv-extd, (5) Limestone, grnd, mn 33% calcium (6) Calcium phosphate, dibasic, commercial, (6) Trace mineral salta Nutrient analysis, % of dry matter Dry matterb Crude proteinb Digestible energy (keal/kg)c Cac pc
International Reference No.
1~0-111 4~2~92 5~4~04 6~2~32 6~1~80
Low
49.7 24.7 22.4 "il4 1.9
Energy level Medium
High
33.6 56.4 7.8
25.5 73.0
~4 .5
" " .'6
1.3
... 1.0
100.0
100.0
100.0
87.7 23.5 3878 1.10 964
87.6 16.1 3873 .74 .43
87.6 11.3 3889 .54 .32
aprovided in addition to NaCI the following as a percentage of the salt mix: iodine, .007; manganese, .24; iron, .24; magnesium, .05 ; copper, .032; cobalt, .001 ; and zinc, .005. bLaboratory determinations. CCalculated from feed composition tables (National Academy of Science -- Atlas of nutritional data on United States and Canadian Feeds).
Downloaded from https://academic.oup.com/jas/article-abstract/43/5/1114/4697297 by Iowa State University user on 23 January 2019
EXPERIMENTAL METHODS
1115
1116
PRIOR AND CHRISTENSON TABLE 2. EFFECT OF DIETARY ENERGY LEVEL ON EWE PLASMA GLUCOSE, INSULIN AND FREE FATTY ACIDS, WEIGHT GAINS AND NUMBER AND WEIGHT OF LAMBS BORN TO FINN-CROSS EWES (EXP. 1) Dietary energylevel Lo w
Nutrient intake a Total feed, g/ewe/day Dry matter, g/ewe/day Digestible energy, Mcal/ewe/day Crude protein, g/ewe/day Ca, g/ewe/day P, g/ewe/day
776 f 681 2.6 182 8.5 5.0
Medium
1319 g 1155 4.5 212 8.7 5.0
High
SE
1704 h 1497 5.8 193 8.2 4.9
44.1
Ewe weight Initial weight, kgb Gain, kgc
59.4 .48 f
59.3 3.88g
59.5 7.86 h
.50 .64
Lambing date d No. ewes lambing No. lambs born alive Avg lamb birth weight, kg Total lamb birth weight, kg
11 2.17 3.53 f 7.54
12 2.27 4.03g 8.86
11 2.0 4.97 h 9.17
.21 .26 .67
Ewe plasma glucose, mg/lO0 ml Day 102 of gestation Day 122 of gestation Average Iambinge
43.0 f 37.9 f 163.9
50.4g 44.8 f 155.3
59.1 h 61.4g 112.7
1.6 3.2 18.2
Ewe plasma insulin, ng/ml Day 102 of gestation Day 122 of gestation After lambinge
.59 f .74 f 1.67
1.20g .93 f 5.80
1.44g 2.52g 4.68
.12 .17 2.49
Ewe plasma free fatty acids, #moles/ml Day 102 of gestation Day 122 of gestation After lambinge
1.06g 1.51 2.09
.64 f 1.31 1.93
.61 f 1.16 2.00
.08 .13 .22
aAverage intake (on as fed basis) from January 15 through day of lambing. bEwes were started on their dietary treatments on January 15 (approximately day 81 of gestation). Cperiod 1 ; Day 81 through 109 of gestation. dExpressed as per ewe lambing. f'g'hMeans without a common superscript differ (P
