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61.
Linear models were developed and evaluated for the estimation of daily (24 h) and total lactation milk yield of dairy sheep from single morning (am) or evening (pm) milking records. A total of 22,908 individual test-day milk records of 5110 ewes of the Chios breed, raised in 46 flocks, were used. Depending on the model, different daily milk yield estimates were derived for each ewe, accounting for lactation number, stage of lactation, season of previous lambing and interval between successive milkings. Daily milk yield was also estimated from doubling the single am or pm record. Actual and estimated yields were compared using root mean square errors (RMSEs), mean absolute differences, an accuracy parameter defined as the ratio of the actual yield variance over the sum of the variances of actual yield and absolute difference, and the product moment correlation between estimated and actual yield. Results were validated on independent datasets. Linear models resulted in less biased and more accurate estimates of the daily milk yield than simply doubling the am or pm record. Root mean square errors decreased by 7-37% and the mean absolute difference was reduced by 1-4% of the average daily yield. Higher accuracy and correlation were obtained from linear model application than doubling. Total lactation milk yield was predicted based on actual daily yield and compared to predictions based on estimated daily yield from am or pm records, as well as directly on single milking records. Root mean square errors obtained when daily yield had been estimated with linear models were 26-35% lower compared to doubling the am or pm yield and 0-13% lower compared to estimating the total lactation yield directly from single milking records. Linear model application also resulted in lower mean absolute difference and higher accuracy and correlation than doubling the am or pm record. Recording the yield of a single milking (am or pm) instead of both can benefit milk recording by reducing its cost and increasing farmer participation. In this context, linear models developed in the present study can be used for the accurate estimation of daily (24 h) and total lactation milk yield from single milking records. 相似文献
62.
63.
本试验选用3头6月龄左右断奶中国荷斯坦公牛,在试验全程喂以相对稳定的日粮,从2003年11月1日开始,到2004年6月20日结束,用以测定中国荷斯坦生长公牛在不同生长期对饲粮中各营养成分的代谢情况。试验结果表明:日粮中的DM、OM、NDF、ADF、淀粉和粗蛋白质的表观消化率随着生长犊牛的月龄的增加而增加(P<0.05);并且9月龄以后,DM、OM、NDF、ADF和粗蛋白质的表观消化率增长不明显(P>0.05),淀粉的表观消化率则在11月龄以后增长不明显(P>0.05)。氮的净吸收率随着生长犊牛的月龄的增加而下降(P<0.05),且在9月龄以后下降不明显(P>0.05)。 相似文献
64.
水稻旱作对其生长量和经济产量的影响 总被引:11,自引:0,他引:11
1998~1999年,研究了水稻旱作条件下,不同生育时期受水分胁迫后对作物生长量的影响。结果表明:不同指标对水分胁迫时期的敏感性不一,植株高度对抽穗期水分胁迫最敏感;单株绿叶面积和单株地上部干重对幼穗分化后期水分胁迫最敏感;根系干重和根冠比对幼穗分化前期水分胁迫最敏感;幼穗分化后期水分胁迫对经济产量影响程度最大,无效分蘖期水分胁迫对产量影响程度最小。 相似文献
65.
关中平原小麦产量对气候变化区域响应的评价模型研究 总被引:4,自引:0,他引:4
根据关中地区宝鸡、西安、渭南与咸阳 4地 (市 )的 1 949~ 1 999年的逐年小麦单产记录序列以及 4地 (市 )的气象观测站点自建站以来至 2 0 0 0年近 5 0年的气象记录序列 ,对关中地区小麦产量与年均温、年降水作相关分析 ;探讨了关中地区小麦单产对气候变化区域响应的评价模型。结果发现 :关中平原气候具有暖干化趋势 ;随着气温变暖 ,小麦产量增加幅度减小 ;小麦产量对降水波动的响应比对气温波动的响应显著。 相似文献
66.
Z. Ngoko K.F. Cardwell W.F.O. Marasas M.J. Wingfield R. Ndemah F. Schulthess 《European journal of plant pathology / European Foundation for Plant Pathology》2002,108(9):893-902
The aim was to identify biological and physical factors responsible for reducing maize yield in Cameroon. Two surveys were conducted in 137 fields in two agroecological zones in 1995–1997. In the Humid Forest (HF), Bipolaris maydis, Stenocarpella macrospora, Puccinia polysora, Rhizoctonia solani and soil fertility were factors that reduced maize production in 1995 and 1996. In the Western Highlands (WHL), Cercospora zeae-maydis, and the interaction between soil fertility and maize variety were the most important constraints to maize production in 1996. In 1997, C. zeae-maydis, S. macrospora, physiological spot and stem borer damage (Busseola fusca) were negatively related to ear weight. The combination of these biological factors (diseases and insects), and the physical parameter of soil fertility were responsible for reducing maize yield in these selected benchmarks of Cameroon. Maximum potential yield reductions were estimated at 68% due to B. maydis and 46% due to S. macrospora, respectively, in the HF in 1995. In 1996, maximum potential yield reductions in the HF were estimated at 34%, 41% and 30% due to S. macrospora, P. polysora and R. solani, respectively. In the WHL, C. zeae-maydis had the potential to cause a yield reduction of 79% in 1996. In the WHL in 1997, the interaction between C. zeae-maydis and B. fusca, stem diseases and the physiological spot caused potential reductions of 52%, 34% and 39%, respectively. 相似文献
67.
20%多效唑·甲哌 FEE7 微乳剂防止小麦倒伏和增产机理研究 总被引:1,自引:0,他引:1
冬小麦二棱期喷施植物生长调节剂20%多效唑·甲哌鎓微乳剂375 mL/hm2,可以显著抑制茎秆基部节间伸长,增加各节间充实度,其中赤霉素(Gas)和生长素(IAA)降低,可显著增强小麦抗倒伏能力和降低田间倒伏率.处理还协调了穗数、穗粒数和粒重的关系,增产幅度6.2%~28.6%.增产原因可能在于促进籽粒灌浆强,增加籽粒中内源Gas、IAA、细胞分裂素(CTKs)的水平,增强了籽粒库活性,同时促进茎叶中干物质向籽粒运转. 相似文献
68.
20%多效唑·甲哌Wong微乳剂防止小麦倒伏和增产机理研究 总被引:2,自引:0,他引:2
冬小麦二棱期喷施植物生长调节剂20%多效唑·甲哌鎓微乳剂375 mL/hm2,可以显著抑制茎秆基部节间伸长,增加各节间充实度,其中赤霉素(Gas)和生长素(IAA)降低,可显著增强小麦抗倒伏能力和降低田间倒伏率.处理还协调了穗数、穗粒数和粒重的关系,增产幅度6.2%~28.6%.增产原因可能在于促进籽粒灌浆强,增加籽粒中内源Gas、IAA、细胞分裂素(CTKs)的水平,增强了籽粒库活性,同时促进茎叶中干物质向籽粒运转. 相似文献
69.
70.