Simerl N A, Wilcox C J, Thatcher W W
Dairy Science Department, University of Florida, Gainesville 32611-0701.
J Dairy Sci. 1992 Feb;75(2):590-5. doi: 10.3168/jds.S0022-0302(92)77796-0.
Records from Florida Agricultural Experiment Station dairy herd for 1144 heifers freshening from 1959 to 1979 were studied to evaluate effects of age and problems at parturition on subsequent yield and reproduction. Statistical analysis was by method of ordinary least squares analysis of variance; five measures of reproduction, survival to second lactation, and 15 measures of yield were studied. Mean first parturition age was 25.8 mo with 40% of individuals less than or equal to 23 mo; survival to second parturition was 67%. No effects of age at first parturition were detected on survival, postpartum reproductive performance, or milk composition other than lactose-mineral, chloride, and acidity percentages; effects on yield were similar to previous reports. Stillbirth did not affect subsequent reproductive performance but was associated with decreased milk yield: 181 kg or 5.2% of overall mean. Milk yield was depressed by 239 kg for retained fetal membrane, 173 kg for dystocia, and 98 kg for metritis; milk composition essentially was unaltered. Heritability of postpartum days to first estrus was .14; estimates were 0 for days to first service, days open, and calving interval. Additional research is needed on interrelationships of gestation length with subsequent yield and reproduction and in alleviating detrimental effects of problems at parturition.
对佛罗里达农业试验站1959年至1979年期间产犊的1144头小母牛的记录进行了研究，以评估年龄和分娩问题对后续产奶量和繁殖性能的影响。采用普通最小二乘方差分析方法进行统计分析；研究了五项繁殖指标、到第二次泌乳的存活率以及十五项产奶量指标。首次分娩的平均年龄为25.8个月，40%的个体小于或等于23个月；到第二次分娩的存活率为67%。除乳糖、矿物质、氯和酸度百分比外，未检测到首次分娩年龄对存活率、产后繁殖性能或牛奶成分有影响；对产奶量的影响与先前报道相似。死产不影响后续繁殖性能，但与产奶量下降有关：下降181千克，占总平均值的5.2%。胎膜滞留使产奶量降低239千克，难产使产奶量降低173千克，子宫炎使产奶量降低98千克；牛奶成分基本未改变。产后至首次发情天数的遗传力为0.14；首次配种天数、空怀天数和产犊间隔的估计值为0。需要进一步研究妊娠期长度与后续产奶量和繁殖性能之间的相互关系，以及减轻分娩问题的有害影响。
