Decreased Plasma Retinol, a-Tocopherol, and Zinc Concentration During the Periparturient Period: Effect of Milk Fever JESSE P. GOFF and JUDITH R. STABEL USDA, AgrlcUtural Research Service National Animal Disease Center Ames. JA 50010 ABSTRACT
Retinol (vitamin A), a-tocopherol (vitamin E), and Zn are micronutrients essential for health and perfonnance. We detennined the effects of parturition, lactation, and periparturient Ca status on plasma retinol, a-tocopherol, and Zn in 18 Jersey cows during the 2 wk before and after parturition. Six cows developed clinical milk fever. Prepartum plasma concentrations of retinol, a-tocopherol, and Zn decreased progressively in all animals. A nadir was reached at 1 d postpartum when concentrations declined to 38, 47, and 67%, respectively, of prepartal baseline concentrations. Plasma Zn returned to baseline concentrations within 3 d of calving, and plasma atocopherol returned toward baseline about 10 d after calving. Plasma retinol remained below baseline concentrations throughout the first 2 wk of lactation. 1be decline in plasma Zn observed at calving was more severe in cows with milk fever (parturient paresis) than in cows without milk fever. The decrease in plasma retinol and a-tocopherol observed at parturition was similar in cows with or without milk fever. These data document an acute decline in plasma retinol, a-tocopherol, and Zn in the immediate periparturient period and indicate that the decline in plasma Zn is more severe in cows with milk fever. (Key words: a-tocopherol, retinol, zinc) INTRODUCTION
Retinol (vitamin A), a-tocopherol (vitamin E), and Zn are essential for optimal health and
Received 1anuary 19, 1990. Accepled April 19, 1990. 1990 1 Dairy Sci 73:3195-3199
perfonnance, and all three nutrients are now recognized. as important factors in maintenance of a functional immune system. During retinol deficiency, epithelial tissues become keratinized and dry, making these tissues more susceptible to infection (18). Lymphocyte and neutrophil function also are impaired in the retinol deficient animal (26). a-Tocopherol deficiency reduces phagocytic cell function (1, 19,23) and results in altered arachidonic acid metabolism to prostaglandins and leukotrienes (3, 16) influencing the inflammatory response to infection. Zinc deficiency can cause rapid thymic atrophy, loss of T-cell function, and reduced thymic honnone concentrations (7). The dairy cow is more susceptible to infection and clinical disease (mastitis, metritis) during the 2 wk before and after parturition than during the rest of lactation or the dry period (17, 20). This appears to be due to a loss in immune cell function, which has been observed during the periparturient period (9, 10, 15), but the factor or factors responsible for this loss of immune cell function are not well understood. Metabolic stressors such as negative energy, protein, and Ca balance associated with parturition and the onset of lactation may play a role in the loss of immune cell function observed around parturition. For example, although a causal relationship has not been established, epidemiological studies indicate that cows developing milk fever (parturient paresis) have a five to nine times greater chance of developing mastitis and metritis than do nonmilk fever cows (4). Johnston and Cbew (14) and Pryor (21) have reported an acute decrease in plasma concentrations of retinol and Zn at parturition in cattle. Plasma concentrations of a-tocopherol in the immediate periparturient period have not previously been detennined, nor has the interaction between a metabolic disease, such as milk fever, and plasma concentrations of these micronutrients been studied. We detennined concentrations of retinol, a-tocopherol, and Zn before and after parturition in order to define
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better the effects of parturition on plasma levels of these important modulators of the immune system. In addition, the effects of hypocalcemia and milk fever on these parameters were also studied.
12
MATERIALS AND METHODS
Plasma samples from 18 Jersey cows were analyzed retrospectively in this study. The cows were divided into three groups based on plasma Ca status near parturition. Six of the cows used in the study had developed milk fever (severely hypocalcemic) and six cows had not developed milk fever (moderately hypocalcemic) during the periparturient period. Six cows were treated with intramuscular injections of synthetic b0vine parathyroid hormone (bPTH 1-34, Peninsula Laboratories, Inc., San Carlos, CA) before parturition and during the first days of lactation using a protocol (9) to prevent milk fever and to maintain relatively normal plasma Ca concentrations in the immediate periparturient period. Cows began receiving PTH on average 5 d before calving and ending 6 d after calving. All cows were from the research herd at the National Animal Disease Center, and calvings occurred in all four seasons. Cows were entering their third or greater lactation. Beginning 4 to 6 wk prepartum, cows were placed in a drylot and fed alfalfa hay for ad libitum intake plus 4.0 kg of a concentrate. Approximately 2 wk prepartum, the cows were offered an additional 6.5 kg of grain daily, which was continued through the first 2 wk of lactation (8). The concentrate was supplemented to supply 78,000 ill of vitamin A, 9 ill of vitamin E, and 263 mg of Zn each day. Plasma samples were 0btained at 14, 10, 7, 5, 4, 3, 2, 1, and 0 d before and after parturition and stored frozen at -27'C until assayed. Plasma Ca and Zn concentrations were determined by atomic absorption spectrophotometry (22). Plasma concentrations of retinol and a-tocopherol were detennined by reverse-phase HPLC (2) using a-tocopherol acetate to determine recovery of both retinol and a-tocopherol during hexane extraction of the plasma. A baseline value for each plasma component for each animal was detennined by averaging the value obtained on d 14, 10, and 7 before parturition. Student's t test was used to test the significance of the difference between mean Journal of Dairy Science Vol. 73,
No. II, 1990
DAYS AROUND PARTlRITlON
Figure 1. Mean ± SE plasma Ca concentrations during the immediate periparturient period in cows wilh milk feva, cows without mille fever (control cows), and cows treated with paralhyroid hormone to prevent milk fever (PIH-treated cows). a.b·"Diffcn:nt from control at P
Retinol (vitamin A), a-tocopherol (vitamin E), and Zn are micronutrients essential for health and perfonnance. We detennined the effects of parturition, lactation, and periparturient Ca status on plasma retinol, a-tocopherol, and Zn in 18 Jersey cows during the 2 wk before and after parturition. Six cows developed clinical milk fever. Prepartum plasma concentrations of retinol, a-tocopherol, and Zn decreased progressively in all animals. A nadir was reached at 1 d postpartum when concentrations declined to 38, 47, and 67%, respectively, of prepartal baseline concentrations. Plasma Zn returned to baseline concentrations within 3 d of calving, and plasma atocopherol returned toward baseline about 10 d after calving. Plasma retinol remained below baseline concentrations throughout the first 2 wk of lactation. 1be decline in plasma Zn observed at calving was more severe in cows with milk fever (parturient paresis) than in cows without milk fever. The decrease in plasma retinol and a-tocopherol observed at parturition was similar in cows with or without milk fever. These data document an acute decline in plasma retinol, a-tocopherol, and Zn in the immediate periparturient period and indicate that the decline in plasma Zn is more severe in cows with milk fever. (Key words: a-tocopherol, retinol, zinc) INTRODUCTION
Retinol (vitamin A), a-tocopherol (vitamin E), and Zn are essential for optimal health and
Received 1anuary 19, 1990. Accepled April 19, 1990. 1990 1 Dairy Sci 73:3195-3199
perfonnance, and all three nutrients are now recognized. as important factors in maintenance of a functional immune system. During retinol deficiency, epithelial tissues become keratinized and dry, making these tissues more susceptible to infection (18). Lymphocyte and neutrophil function also are impaired in the retinol deficient animal (26). a-Tocopherol deficiency reduces phagocytic cell function (1, 19,23) and results in altered arachidonic acid metabolism to prostaglandins and leukotrienes (3, 16) influencing the inflammatory response to infection. Zinc deficiency can cause rapid thymic atrophy, loss of T-cell function, and reduced thymic honnone concentrations (7). The dairy cow is more susceptible to infection and clinical disease (mastitis, metritis) during the 2 wk before and after parturition than during the rest of lactation or the dry period (17, 20). This appears to be due to a loss in immune cell function, which has been observed during the periparturient period (9, 10, 15), but the factor or factors responsible for this loss of immune cell function are not well understood. Metabolic stressors such as negative energy, protein, and Ca balance associated with parturition and the onset of lactation may play a role in the loss of immune cell function observed around parturition. For example, although a causal relationship has not been established, epidemiological studies indicate that cows developing milk fever (parturient paresis) have a five to nine times greater chance of developing mastitis and metritis than do nonmilk fever cows (4). Johnston and Cbew (14) and Pryor (21) have reported an acute decrease in plasma concentrations of retinol and Zn at parturition in cattle. Plasma concentrations of a-tocopherol in the immediate periparturient period have not previously been detennined, nor has the interaction between a metabolic disease, such as milk fever, and plasma concentrations of these micronutrients been studied. We detennined concentrations of retinol, a-tocopherol, and Zn before and after parturition in order to define
3195
3196
GOFF AND STADEL
better the effects of parturition on plasma levels of these important modulators of the immune system. In addition, the effects of hypocalcemia and milk fever on these parameters were also studied.
12
MATERIALS AND METHODS
Plasma samples from 18 Jersey cows were analyzed retrospectively in this study. The cows were divided into three groups based on plasma Ca status near parturition. Six of the cows used in the study had developed milk fever (severely hypocalcemic) and six cows had not developed milk fever (moderately hypocalcemic) during the periparturient period. Six cows were treated with intramuscular injections of synthetic b0vine parathyroid hormone (bPTH 1-34, Peninsula Laboratories, Inc., San Carlos, CA) before parturition and during the first days of lactation using a protocol (9) to prevent milk fever and to maintain relatively normal plasma Ca concentrations in the immediate periparturient period. Cows began receiving PTH on average 5 d before calving and ending 6 d after calving. All cows were from the research herd at the National Animal Disease Center, and calvings occurred in all four seasons. Cows were entering their third or greater lactation. Beginning 4 to 6 wk prepartum, cows were placed in a drylot and fed alfalfa hay for ad libitum intake plus 4.0 kg of a concentrate. Approximately 2 wk prepartum, the cows were offered an additional 6.5 kg of grain daily, which was continued through the first 2 wk of lactation (8). The concentrate was supplemented to supply 78,000 ill of vitamin A, 9 ill of vitamin E, and 263 mg of Zn each day. Plasma samples were 0btained at 14, 10, 7, 5, 4, 3, 2, 1, and 0 d before and after parturition and stored frozen at -27'C until assayed. Plasma Ca and Zn concentrations were determined by atomic absorption spectrophotometry (22). Plasma concentrations of retinol and a-tocopherol were detennined by reverse-phase HPLC (2) using a-tocopherol acetate to determine recovery of both retinol and a-tocopherol during hexane extraction of the plasma. A baseline value for each plasma component for each animal was detennined by averaging the value obtained on d 14, 10, and 7 before parturition. Student's t test was used to test the significance of the difference between mean Journal of Dairy Science Vol. 73,
No. II, 1990
DAYS AROUND PARTlRITlON
Figure 1. Mean ± SE plasma Ca concentrations during the immediate periparturient period in cows wilh milk feva, cows without mille fever (control cows), and cows treated with paralhyroid hormone to prevent milk fever (PIH-treated cows). a.b·"Diffcn:nt from control at P
