Steelman C D, Brown C J, McNew R W, Gbur E E, Brown M A, Tolley G
Department of Entomology, University of Arkansas, Fayetteville, AR 72701, USA.
Med Vet Entomol. 1996 Apr;10(2):129-36. doi: 10.1111/j.1365-2915.1996.tb00718.x.
Statistically significant differences were observed in the population density of the horn fly, Haematobia irritans irritans L., on Angus cows having significantly different frame sizes. Angus cows, averaging < 112.5 cm in height at the hip, had significantly lower numbers of horn flies than Angus cows that measured 112.5-117.5 cm, 117.5-120 cm, 120-126 cm and > 126 cm in height at the hip. The Angus I cows ( < 112.5 cm in height at the hip) were significantly shorter in length (mean distance from the withers to the hip bone) and were smaller in girth than the Angus II (112.5-126 cm) and Booneville Angus cows ( > 126 cm). The estimated heritability (h2) of horn fly resistance was 0.43 +/- 0.07 and 0.95 +/- 0.31 for 1989 and 1990, respectively. Horn fly counts on the Angus I herd ( < 112.5 cm in height) was 118.1 (probable breeding value, PBV = -20.69) to 165 horn flies per cow (PBV = 26.9 flies per cow in 1989) and from 75.9 (PBV = -29.1) to 134.5 (PBV = 29.5) flies per cow in 1990. Angus I bulls had PBV = -23.7 to 13.4 and from -26.5 to 14.75 in 1989 and 1990, respectively. The Angus II cows had horn fly counts that ranged from 159.6 (PBV of -23.5) to 208.1 (PBV of 25) per cow in 1989 and from 232.3 (PBV of -56.2) to 378.7 (PBV of 90) per cow in 1990. Angus II bulls had PBVs that ranged from -17.1 to 18.9 in 1989 and from -28.1 to 48.8 in 1990. The Angus I cows had significantly (P < 0.0001) lower numbers of horn flies (mean of 63.8 horn flies per m2) than the small, medium or large Angus II cows (mean of 129.4, 149.6 and 145.5 horn flies per m2, respectively). The data indicated that some specific factor(s) associated with cow size contribute(s) to innate resistance of cattle to the horn fly.
在体型显著不同的安格斯母牛身上，观察到角蝇（Haematobia irritans irritans L.）的种群密度存在统计学上的显著差异。臀部高度平均小于112.5厘米的安格斯母牛，其角蝇数量显著低于臀部高度为112.5 - 117.5厘米、117.5 - 120厘米、120 - 126厘米以及大于126厘米的安格斯母牛。臀部高度小于112.5厘米的安格斯I型母牛，其体长（从肩部到髋骨的平均距离）显著较短，胸围也比安格斯II型（112.5 - 126厘米）和布恩维尔安格斯母牛（大于126厘米）小。1989年和1990年，角蝇抗性的估计遗传力（h2）分别为0.43±0.07和0.95±0.31。1989年，安格斯I型牛群（臀部高度小于112.5厘米）每头牛的角蝇数量为118.1只（可能育种值，PBV = -20.69）至165只（1989年每头牛的PBV = 26.9只），1990年为每头牛75.9只（PBV = -29.1）至134.5只（PBV = 29.5）。1989年和1990年，安格斯I型公牛的PBV分别为 -23.7至13.4以及 -26.5至14.75。1989年，安格斯II型母牛每头牛的角蝇数量在159.6只（PBV为 -23.5）至208.1只（PBV为25）之间，1990年在232.3只（PBV为 -56.2）至378.7只（PBV为90）之间。1989年和1990年，安格斯II型公牛的PBV分别在 -17.1至18.9以及 -28.1至48.8之间。安格斯I型母牛的角蝇数量（每平方米平均63.8只角蝇）显著（P < 0.0001）低于小型、中型或大型安格斯II型母牛（每平方米分别平均为129.4只、149.6只和145.5只角蝇）。数据表明，与母牛体型相关的某些特定因素对牛对角蝇的先天抗性有影响。
