Wichtel J J, Freeman D A, Craigie A L, Varela-Alvarez H, Williamson N B
Department of Veterinary Clinical Sciences, Massey University, Palmerston North, New Zealand.
N Z Vet J. 1996 Feb;44(1):15-21. doi: 10.1080/00480169.1996.35925.
The objectives of this study were to provide baseline data for alpha-tocopherol, selenium and polyunsaturated fatty acid concentrations in the serum and feed of New Zealand dairy cattle, and to assess the likelihood that abnormal peroxide metabolism has a role in the impaired lactational and reproductive performance noted in selenium-deficient cattle. Twenty-four Friesian heifers were randomly allocated one of four winter diets consisting of hay with or without selenium supplementation, or pasture and silage with or without selenium supplementation. A winter diet consisting exclusively of hay (alpha-tocopherol concentration 19 mg/kg of dry matter) resulted in a pre-calving serum alpha-tocopherol concentration of 1.2 mg/l compared to 4.5 mg/l for pastured heifers (p<0.01). The pre-calving alpha-tocopherol concentration for the heifers fed hay fell into the range considered deficient (<2.0 mg/l), whereas heifers fed pasture and silage remained in the range considered adequate throughout the study period. Serum fatty acid concentration, and the proportion of fatty acids that were polyunsaturated, were lowest in the hay-fed heifers before calving (1.0 mg/ml, 37.1% respectively), and remained unchanged following re-introduction to pasture after calving in late July and August. Serum fatty acid concentration did not increase following the re-introduction of the heifers to pasture because of the unexpectedly low fatty acid concentration (4.8 g/kg of dry matter) of the mature winter pasture. In October, however, the proportion of fatty acids in serum that were polyunsaturated increased (50%) as did serum cy-tocopherol concentrations (greater than 13 mg/l). Mean serum selenium concentrations in the unsupplemented heifers ranged from 139 to 204 nmol/l, being lowest in October (p<0.01). Supplementation with intraruminal selenium pellets (two pellets delivering about 3 mg of selenium/day) increased serum selenium concentration and glutathione peroxidase activity (p<0.01) whereas the type of winter diet had no effect (p>0.05). These results suggest that dairy cattle wintered on hay can become Vitamin E-depleted, whereas the feeding of pasture and silage should provide adequate Vitamin E. The pasture offered following calving during July and August provided a low dietary polyunsaturated fatty acid challenge, suggesting that abnormal peroxide metabolism is unlikely to be an important mechanism in the impaired performance of selenium-deficient adult cattle which calve at this the of year.
本研究的目的是提供新西兰奶牛血清和饲料中α-生育酚、硒和多不饱和脂肪酸浓度的基线数据，并评估异常的过氧化物代谢是否在缺硒奶牛泌乳和繁殖性能受损中起作用。24头弗里生小母牛被随机分配到四种冬季日粮之一，日粮包括添加或不添加硒的干草，或添加或不添加硒的牧草和青贮饲料。仅由干草组成的冬季日粮（α-生育酚浓度为19毫克/千克干物质）导致产犊前血清α-生育酚浓度为1.2毫克/升，而放牧的小母牛为4.5毫克/升（p<0.01）。饲喂干草的小母牛产犊前的α-生育酚浓度处于被认为缺乏的范围（<2.0毫克/升），而在整个研究期间，饲喂牧草和青贮饲料的小母牛的α-生育酚浓度仍处于被认为充足的范围内。产犊前，干草饲喂的小母牛血清脂肪酸浓度以及多不饱和脂肪酸的比例最低（分别为1.0毫克/毫升和37.1%），在7月下旬和8月产犊后重新放牧后保持不变。由于成熟冬季牧草的脂肪酸浓度意外较低（4.8克/千克干物质），小母牛重新放牧后血清脂肪酸浓度并未增加。然而，在10月，血清中多不饱和脂肪酸的比例增加了（50%），血清α-生育酚浓度也增加了（大于13毫克/升）。未补充硒的小母牛血清硒平均浓度在139至204纳摩尔/升之间，10月最低（p<0.01）。瘤胃内补充硒颗粒（每天两粒，约提供3毫克硒）可提高血清硒浓度和谷胱甘肽过氧化物酶活性（p<0.01），而冬季日粮类型则无影响（p>0.05）。这些结果表明，以干草越冬的奶牛可能会出现维生素E缺乏，而饲喂牧草和青贮饲料应能提供充足的维生素E。7月和8月产犊后提供的牧草对日粮多不饱和脂肪酸的挑战较低，这表明异常的过氧化物代谢不太可能是在一年中的这个时候产犊的缺硒成年奶牛性能受损的重要机制。
