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Investigations into the nutritional efficiency of dairy heifers limit fed diets containing different levels of forage and concentrate.

机译：对奶牛小母牛营养效率的研究限制了饲喂日粮中含有不同水平的饲料和精料。

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摘要

Limit feeding high concentrate or high digestibility diets for growing dairy heifers may offer an economical alternative to ad libitum consumption of high forage, low digestibility diets that are traditionally fed to dairy heifers. Literature pertaining to economic, physiological, and nutritional responses to alterations in feeding level and dietary concentrate level are reviewed. It is concluded that limit feeding higher concentrate diets do not affect growth or first lactation milk production compared to dairy heifers fed high forage diets when equivalent levels of gain are obtained. It is also concluded that limit feeding high concentrate diets does not need to be excluded as a management option and may offer an opportunity for heifer growers to reduce feed costs and environmental output under certain circumstances. The level of dietary crude protein resulting in maximum efficiency of nutrient utilization under a limit feeding, high concentrate management system and differences from limit-fed high forage feeding are not available from the literature. Therefore, the objective of the reported experiment was to evaluate efficiency of nutrient and N utilization of dairy heifers limit-fed a low forage/high concentrate and high forage diets at equal ME intakes and 4 levels of N intake.;The hypothesis of this experiment is that a low forage (LF) ration will be utilized with a greater efficiency than a high forage ration (HF) by dairy heifers and that the response will be affected by level of N intake. To test this hypothesis, 8 Holstein heifers (beginning at 362 +/- 7 kg and 12.3 +/- 0.4 mo) were fed eight rations according to a split-plot, 4 x 4 Latin square design. Treatments were formulated to contain 25% or 75% forage (corn silage and chopped wheat straw) and fed at 4 levels of N intake [0.94 (Low), 1.62 (MLow), 2.30 (MHigh), 2.96 (High) g N/kg BW0.75 per d]. Diets were limit-fed to maintain equal ME intake. Organic matter (OM) intake was greater for heifers fed HF, but, due to increased OM digestibility of LF (74.0 vs 67.6% +/- 0.9; P 0.01), digestible OMI was unaffected by forage level (P > 0.50). OM digestibility was affected by an interaction between forage level and N intake (P 0.01); increasing to a plateau of 78.01% at 18.43 %CP for LF and 68.78% at 13.90 %CP for HF fed heifers. Apparent N digestibility was greater for heifers fed LF and increased from 47.7% to 80.8% between Low and High N intake. Less N appeared in the feces of heifers fed LF than HF (45.56 vs 52.60 g per d). Urea-N excretion was not different between forage levels, but increased linearly with N intake. Concentration of plasma urea N (PUN) was significantly higher for LF and with increasing N intake. Like urea-N excretion, daily urinary N excretion was affected only by N intake. Retained N responded linearly to increased levels of NI. As a result of a significant interaction between forage level and NI on fecal N excretion and numerical differences in urine N, retained N at maximum N intake was greater for LF than HF. In spite of this observation, the percent of N intake that was retained only tended to be affected by an interaction and was not significantly affected by forage level. It is concluded that increasing N intake increases the digestibility of OM, the magnitude of which depends on the level of dietary forage provided. Furthermore, differences in N utilization between LF and HF in this trial were small and were not evident until N intake increased to impractical levels.
机译：限制饲喂生长中的奶牛的高浓缩或高消化率的饮食，可以提供经济的替代方式，以替代传统上饲喂奶牛的高饲草，低消化率的饮食。综述了有关饲喂水平和膳食浓缩水平变化的经济，生理和营养反应的文献。结论是，与饲喂高饲粮日粮的奶牛相比，限饲高浓缩日粮不会影响生长或第一次泌乳的奶产量。得出的结论是，不必排除限制饲喂高浓缩日粮的管理办法，并且可以在某些情况下为小母牛种植者提供降低饲料成本和环境产出的机会。从文献中无法获得在限制饲喂，高浓缩饲料管理系统下导致最大的养分利用效率的日粮粗蛋白水平以及与限制饲喂高饲草饲喂的区别。因此，本实验的目的是评估在相同的ME摄入量和4 N摄入量的情况下，限制饲喂低牧草/高浓缩饲料和高饲粮的奶牛的营养和氮素利用效率。这是因为奶牛的低饲草（LF）比高饲草（HF）的利用率更高，并且氮素摄入量会影响其响应。为了检验这一假设，根据剖分式4 x 4拉丁方形设计，为8个口粮喂了8个荷斯坦小母牛（始于362 +/- 7 kg和12.3 +/- 0.4 mo）。配制的饲料含有25％或75％的草料（玉米青贮饲料和切碎的麦草），并以4种水平的氮摄入量喂养[0.94（低），1.62（MLow），2.30（MHigh），2.96（High）g N /千克BW0.75 /天]。限制饮食以维持相等的ME摄入量。饲喂HF的小母牛的有机质（OM）摄入量较大，但是，由于LF的OM消化率增加（74.0对67.6％+/- 0.9； P <0.01），可消化的OMI不受饲草水平的影响（P> 0.50）。 OM消化率受饲草水平和氮摄入之间的相互作用的影响（P <0.01）；对于LF饲喂的小母牛，在18.43％CP时增加到78.01％的平稳期，在13.90％CP时增加到68.78％的平稳期。饲喂LF的小母牛的表观氮消化率更高，低氮和高氮摄入之间的表观氮消化率从47.7％增加到80.8％。饲喂LF的小母牛的粪便中出现的氮少于HF（45.56 vs. 52.60 g / d）。饲草水平之间的尿素氮排泄量没有差异，但随氮素摄入量线性增加。 LF的血浆尿素氮（PUN）浓度显着较高，并且随着氮摄入的增加而增加。像尿素氮的排泄一样，每日尿中氮的排泄仅受氮摄入的影响。保留的氮对NI水平升高呈线性反应。由于饲草水平和NI在粪便N排泄和尿液N的数量差异之间存在显着的相互作用，LF的最大氮摄入量保留的N大于HF。尽管有此观察，但保留的氮摄入量百分比仅受相互作用的影响，而不受草料水平的显着影响。结论是，增加的氮摄入量会增加OM的消化率，而OM的消化率取决于所提供的饮食饲料水平。此外，在该试验中，LF和HF之间的氮利用差异很小，并且直到氮摄入增加到不切实际的水平时才明显。

著录项

  • 作者

    Zanton, Geoffrey I.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Agriculture Animal Culture and Nutrition.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 94 p.
  • 总页数 94
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 饲料;
  • 关键词

  • 入库时间 2022-08-17 11:38:25

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