Thamsborg S M, Jørgensen R J, Nansen P
Department of Clinical Studies, Large Animal Medicine, Royal Veterinary and Agricultural University, Frederiksberg, Denmark.
Acta Vet Scand. 1998;39(3):311-23. doi: 10.1186/BF03547779.
Eighty-four first-year grazing Holstein-Friesian steers were observed through 2 years on 40 ha of reclaimed unfertilized grassland with the objective of investigating the influence of stocking rate (SR) on internal parasitism under extensive grazing conditions. Three groups of steers were grazed each year at low, medium and high SR in separate paddocks (0.53, 1.05 and 1.55 steers/ha). The faecal egg counts of predominantly Cooperia and Ostertagia spp. were influenced by SR in the first year (p < 0.05) with maximum geometric means of 135, 182 and 217 epg in the low, medium and high SR groups, respectively, and part of the second year (p = 0.08) with maximum geometric means of 88, 134 and 195 epg. In the second year, all steers were treated with levamisole by 26 July due to diarrhoea, being particularly severe at high SR and 7 steers were withdrawn from this group at the same time. Serum pepsinogen levels indicated a higher rate of uptake of Ostertagia larvae in higher SR groups in the second season before treatment (p < 0.01). The mean weight gains (+/- s.d.) for the first year were 630 +/- 58, 341 +/- 97 and 300 +/- 151 g/day in the low, medium and high SR groups, respectively, and in the second year the corresponding figures were 565 +/- 109, 357 +/- 135 and 247 +/- 129 g/day. Although the SRs were much lower than commonly found on improved pastures, we conclude that feed on offer was a limiting factor in late season and secondly, that the levels of exposure and uptake of nematodes in steers were affected by SR. The levels of parasitism at the medium and high SR were high enough to have affected production.
84头初产放牧的荷斯坦-弗里生公牛在40公顷未施肥的开垦草地上进行了为期2年的观察，目的是研究粗放放牧条件下饲养密度（SR）对体内寄生虫感染的影响。每年将三组公牛分别在低密度、中等密度和高密度饲养密度下，在不同的围场中放牧（每公顷0.53、1.05和1.55头公牛）。第一年，主要是库珀属和奥斯特他属的粪便虫卵计数受饲养密度影响（p<0.05），低密度、中等密度和高密度饲养密度组的最大几何平均数分别为每克粪便135、182和217个虫卵，第二年部分时间也受影响（p = 0.08），最大几何平均数分别为每克粪便88、134和195个虫卵。第二年，由于腹泻，所有公牛在7月26日前都用左旋咪唑进行了治疗，腹泻在高密度饲养密度下尤为严重，同时有7头公牛从该组中撤出。血清胃蛋白酶原水平表明，在治疗前的第二季，高密度饲养密度组中奥斯特他属幼虫的摄取率更高（p<0.01）。第一年，低密度、中等密度和高密度饲养密度组的平均日增重（±标准差）分别为630±58、341±97和300±151克，第二年相应数字分别为565±109、357±135和247±129克。虽然饲养密度远低于改良牧场常见的密度，但我们得出结论，后期可利用的饲料是一个限制因素，其次，公牛体内线虫的暴露和摄取水平受饲养密度影响。中等密度和高密度饲养密度下的寄生虫感染水平高到足以影响生产。
