Universidade Federal de Viçosa, Departamento de Zootecnia, 36571-000, Viçosa, MG, Brazil.
J Anim Sci. 2013 Aug;91(8):3836-46. doi: 10.2527/jas.2012-5636. Epub 2013 May 8.
The objective of this study was to use (15)N to label microbial cells to allow development of equations for estimating the microbial contamination in ruminal in situ incubation residues of forage produced under tropical conditions. A total of 24 tropical forages were ruminal incubated in 3 steers at 3 separate times. To determine microbial contamination of the incubated residues, ruminal bacteria were labeled with (15)N by continuous intraruminal infusion 60 h before the first incubation and continued until the last day of incubation. Ruminal digesta was collected for the isolation of bacteria before the first infusion of (15)N on adaptation period and after the infusion of (15)N on collection period. To determine the microbial contamination of CP fractions, restricted models were compared with the full model using the model identity test. A value of the corrected fraction "A" was estimated from the corresponding noncorrected fraction by this equation: Corrected "A" fraction (A(CP)C) = 1.99286 + 0.98256 × A" fraction without correction (A(CP)WC). The corrected fraction "B" was estimated from the corresponding noncorrected fraction and from CP, NDF, neutral detergent insoluble protein (NDIP), and indigestible NDF (iNDF) using the equation corrected "B" fraction (B(CP)C) = -17.2181 - 0.0344 × fraction "B" without correction (B(CP)WC) + 0.65433 × CP + 1.03787 × NDF + 2.66010 × NDIP - 0.85979 × iNDF. The corrected degradation rate of "B" fraction (kd)was estimated using the equation corrected degradation rate of "B" fraction (kd(CP)C) = 0.04667 + 0.35139 × degradation rate of "B" fraction without correction (kd(CP)WC) + 0.0020 × CP - 0.00055839 × NDF - 0.00336 × NDIP + 0.00075089 × iNDF. This equation was obtained to estimate the contamination using CP of the feeds: %C = 79.21 × (1 - e(-0.0555t)) × e(-0.0874CP). It was concluded that A and B fractions and kd of CP could be highly biased by microbial CP contamination, and therefore these corrected values could be obtained mathematically, replacing the use of microbial markers. The percentage of contamination and the corrected apparent degradability of CP could be obtained from values of CP and time of incubation for each feed, which could reduce cost and labor involved when using (15)N.
本研究的目的是使用（15）N 标记微生物细胞，以便为估计热带条件下生产的饲料瘤胃原位培养残渣中的微生物污染开发方程。总共 24 种热带饲料在 3 头牛中进行了 3 次瘤胃孵育。为了确定孵育残渣中的微生物污染，在第一次孵育前 60 小时连续瘤胃内输注（15）N 标记瘤胃细菌，并持续到孵育的最后一天。在适应期第一次输注（15）N 之前和收集期输注（15）N 后，收集瘤胃液以分离细菌。为了确定 CP 分数的微生物污染，使用模型身份检验比较了受限模型和全模型。通过以下方程从相应的未校正分数估计校正分数“A”：校正分数“A”（A（CP）C）= 1.99286 + 0.98256×A“无校正分数（A（CP）WC）。使用以下方程从相应的未校正分数和 CP、NDF、中性洗涤剂不溶性蛋白（NDIP）和不可消化 NDF（iNDF）中估计校正分数“B”：校正分数“B”（B（CP）C）= -17.2181-0.0344×无校正分数“B”（B（CP）WC）+ 0.65433×CP + 1.03787×NDF + 2.66010×NDIP-0.85979×iNDF。使用以下方程估计校正分数“B”的校正降解率（kd）：校正分数“B”的校正降解率（kd（CP）C）= 0.04667+0.35139×无校正分数“B”的降解率（kd（CP）WC）+0.0020×CP-0.00055839×NDF-0.00336×NDIP+0.00075089×iNDF。该方程用于估计饲料 CP 的污染：%C=79.21×（1-e（-0.0555t））×e（-0.0874CP）。结果表明，A 和 B 分数和 CP 的 kd 可能受到微生物 CP 污染的高度影响，因此可以通过数学方法获得这些校正值，从而取代使用微生物标记物。可以从每个饲料的 CP 值和孵育时间获得污染百分比和 CP 的校正表观降解率，这可以降低使用（15）N 时的成本和劳动力。
