首页> 外文期刊>Animal >N-alkanes v. ytterbium/faecal index as two methods for estimating herbage intake of dairy cows fed on diets differing in the herbage:maize silage ratio and feeding level.
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N-alkanes v. ytterbium/faecal index as two methods for estimating herbage intake of dairy cows fed on diets differing in the herbage:maize silage ratio and feeding level.

机译:N-烷烃v y /粪便指数是两种以不同日粮饲喂日粮的奶牛牧草摄入量的估算方法:玉米青贮比和饲喂水平。

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The aim of this study was to compare the n-alkanes and the ytterbium (Yb)/faecal index techniques as two methods for estimating the herbage intake of dairy cows fed indoors on different herbage:supplement ratios and feeding levels. The supplement was a mixture of maize silage and soyabean meal (ratio of 87:13 on a dry matter (DM) basis). In all, four treatments were studied. The herbage:supplement ratio in the diet was 25:75, 50:50, 75:25 and 50:50 for treatments 1, 2, 3 and 4, respectively. Animals were offered for treatments 1, 2 and 3, 100% of ad libitum intake measured before the experiment and 70% of ad libitum intake for treatment 4. Cows were fed herbage in the morning and supplement in the evening. A total of six lactating Holstein dairy cows were used in a 4*4 Latin square with four 14-day periods. Herbage and supplement intakes, faecal output (FO), in vivo organic matter (OM) digestibility and faecal recovery of markers were measured on the last 5 days of each period. Intake was estimated with the two methods and from two faecal sampling techniques, that is, total faecal collection v. grab sampling during milking. Mean herbage intake as fed, or estimated from n-alkanes or from the Yb/faecal index was 7.7, 8.1 and 10.2 kg DM, respectively. The mean prediction error, expressed as a fraction of actual herbage intake, was 0.10 and 0.50 for the n-alkanes and Yb/faecal index methods, respectively. The n-alkanes method clearly showed much better accuracy than the Yb/faecal index method for estimating intake, irrespective of the faecal sampling method, herbage:silage proportion or feeding level. For the n-alkanes method, herbage intake was slightly overestimated (7%) when herbage proportion in the diet was high, due to a ratio of faecal C 33:C 32 recovery >1. The high bias for the Yb/faecal index was due to the cumulative effect of overestimation of FO (mean recovery of Yb=0.92) and underestimation of the diet indigestible fraction (-8%). Between-treatment variations of FO were on average well estimated by Yb. Between-treatment variations of OM digestibility estimated using the faecal index technique were lower than those observed in vivo. It is concluded that intake of grazing dairy cows receiving high levels of maize silage supplement should be estimated using the n-alkanes method.
机译:这项研究的目的是比较正构烷烃和the(Yb)/粪便指数技术,这两种方法可以估算在不同牧草条件下在室内饲养的奶牛的牧草摄入量:补充比例和饲喂水平。补充剂是玉米青贮饲料和大豆粉的混合物(以干物质(DM)为基准的比率为87:13)。总共研究了四种治疗方法。处理1、2、3和4的日粮中牧草:补充比例分别为25:75、50:50、75:25和50:50。为动物提供治疗1、2和3,在实验前测得的自由采食量为100%,为治疗4测得的采食量为70%。早晨给牛喂草,晚上给牛补饲。在4 * 4的拉丁方广场上总共使用了6头泌乳的荷斯坦奶牛,每4天14天。在每个时期的最后5天,测量草本和补充剂的摄入量,粪便的排泄量(FO),体内有机物(OM)的消化率和粪便中标志物的回收率。通过两种方法和两种粪便采样技术(即,挤奶期间的总粪便收集量与抓取采样数)估算摄入量。饲喂或根据正构烷烃或Yb /粪便指数估算的平均牧草摄入量分别为7.7、8.1和10.2 kg DM。对于正构烷烃法和Yb /粪便指数法,平均预测误差(表示为实际牧草摄入量的一部分)分别为0.10和0.50。不管粪便采样方法,草料,青贮饲料的比例或饲喂水平如何,正构烷烃方法在估计摄入量方面均明显优于Yb /粪便指数方法。对于正构烷烃法,当日粮中的草料比例较高时,由于粪便中C 33:C 32的回收率> 1,草料的摄入量被高估了(7%)。 Yb /粪便指数的偏高归因于对FO的高估(Yb的平均回收率= 0.92)和饮食中难消化成分(-8%)的低估的累积效应。 Yb平均很好地估计了FO之间的治疗间差异。使用粪便指数技术估算的处理间OM消化率差异低于体内观察到的差异。结论是,应使用正构烷烃方法估算接受高水平玉米青贮饲料的放牧奶牛的摄入量。

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