Ileal and total tract digestibility in local (Mong Cai) and exotic (Landrace × Yorkshire) piglets fed low and high-fibre diets, with or without enzyme supplementation

Ileal and total tract digestibility of low and high-fibre diets (100 and 200 g/kg neutral detergent fibre), with or without enzyme supplementation (mixture of cellulase, β-glucanase, α-amylase and protease) was determined in piglets of two breeds weaned at 30 days of age. The breeds were local (pure-breed Mong Cai, MC) and exotic (Landrace × Yorkshire, LY). The experimental diets were based on maize meal, soybean meal, fish meal, cassava residue meal, and rice bran. Cassava residue meal and rice bran were the main fibrous feeds in the high-fibre diet. The experiment was arranged according to a 2 × 2 × 2 factorial, completely randomized design with 4 replications, and lasted for 30 days. The coefficient of ileal apparent digestibility (CIAD) was measured by analyzing ileal digesta collected from piglets killed at 60 days of age. The coefficient of total tract apparent digestibility (CTTAD) was measured by analyzing faecal samples collected for 5 consecutive days immediately before the experiment finished. The CIAD and CTTAD of organic matter, crude protein, crude fibre, neutral detergent fibre, acid detergent fibre and amino acids in the high-fibre diet were lower than in the low-fibre diet (P < 0.01). The CIAD of nutrients and amino acids was similar (P > 0.05) between MC and LY, while the CTTAD of nutrients was higher for the MC than for LY (P < 0.05). Enzyme supplementation of the high-fibre diet improved daily gain and the digestibility of all dietary components at the ileum and in the total tract (P < 0.05), but there was no effect of enzyme supplementation of the low-fibre diet (P > 0.05).     

Association between butyrate and short-chain fatty acid concentrations in gut contents and faeces in weaning piglets

The concentration and composition of short-chain fatty acids (SCFA) in gastrointestinal and faecal samples were studied in weaning pigs fed different amounts and composition dietary fibre (DF). In Trial 1 a total of 50 castrated piglets were fed five experimental diets with varying contents of citrus pectin (soluble fibre) and barley hulls (insoluble fibre) and gastrointestinal contents were collected at euthanasia 9 days after weaning. In Trial 2, 120 pair-wise penned piglets were allocated to the same experimental diets as in Trial 1 (24 piglets per treatment), and fresh faecal samples were collected 5 and 32 days after weaning.

There was no difference in the concentrations of SCFA caused by dietary treatments, but across treatments there was a correlation between concentration of SCFA and the proportion of butyrate. The correlation was lowest in the caecum (r² = 0.22, P = 0.0007) and highest in the distal colon (r² = 0.45, P = 0.0001). In faeces there was no relationship 5 days after weaning (r² = 0.004. P = 0.64) but a correlation of r² = 0.25 (P = 0.0001) 32 days after weaning. The results suggest that adaptive changes and differences between piglets in fermentative capacity immediately after weaning are associated not only with a higher concentration of SCFA but also a changed fermentation profile.     

Effect of cooking and fermentation of a pig diet on gut environment and digestibility in growing pigs

The effect of pre-feeding treatment of a pig diet on gut environment and digestibility was studied in a double 3 × 3 Latin-square experiment using growing castrated PVTC cannulated male pigs. The diets were based on local feed resources and were fed raw (R), cooked (C) or naturally fermented (F). There were no differences (P > 0.05) in pH and butyric acid concentration of ileal digesta between diets. However, on diet F concentrations of acetic, lactic and propionic acid in ileal digesta were higher (P < 0.05) than on diets R and C. The relative proportions of individual organic acids in ileal digesta were not a reflection of the fermentation profile found in diet F. The ileal apparent digestibility of crude protein, crude fiber and NDF were higher (P < 0.05) on diet F than on diets R and C. The total tract apparent digestibility of crude protein was higher (P < 0.05) on diet F diet than on diets R and C, while there were no differences in total tract apparent digestibility between diets for any other dietary component. In conclusion, when compared with a pig diet in the raw form, fermentation influenced the gut environment and improved the digestibility of some dietary component, while cooking prior to feeding had no measurable effects.     

强氯精浸渍苎麻对纤维品质影响的初步研究

试验结果表明 ,用 5%的强氯精浸渍苎麻原麻 1～ 2h的效果最好 ,可以脱去9.2 4%～ 1 0 .58%的胶质 ,并使纤维强度达到 0 .595～ 0 .6 1 2N/tex。     

广东樟科主要属种的木材系统解剖

本文研究了广东樟科植物9属26种的木材构造。 研究表明,在地处热带北缘及亚热带的广东,樟科木材的成熟年龄在18～45年之间,在同属不同种之间,其木材成熟所需的时间比较接近,表明了各属植物遗传上的相近性。 樟科植物从木材解剖特征来看,无论是幼态材或者成熟材都不是原始的。 樟科是一个自然的分类群,各属间木材解剖特征区别不很明显。鳄梨族的琼楠属和厚壳桂族的厚壳桂属在木材构造上比较相似,很可能是鳄梨族通过琼楠亚族向厚壳桂族发展。木姜子族的木姜子属、新木姜子属和山胡椒属的木材解剖特征很接近,形成了自然的类群。     

Changes in the composition of sugarcane harvest residues during decomposition as a surface mulch

Many sugarcane crops in northeastern Australia are now harvested without prior burning and large masses of leafy residues are thus available for use as a surface mulch, or for incorporation into the mineral soil. The standing crop biomass of harvest residues at the present study site was estimated at 1583 g/m^-2 on the day of harvest and was followed for 338 days, at which time approximately 19% of the initial mass of residues remained. Decomposition did not depart from simple exponential kinetics. Concentrations of K and Mg declined rapidly with age of the residues. N and Ca initially declined but increased again after 75 days; the increased Ca was attributed to the presence of Ca-enriched earthworm casts. P and C concentrations varied little throughout the study. The C: N ratio started at 170, increased to 240, and subsequently diminished to a minimum of ca. 70. Proximate lignin increased and neutral detergent fibre concentrations decreased with time of decomposition. Decomposition occurred in two phases; an initial phase of rapid leaching was followed by a period of soil mixing resulting from earthworm casting into the decomposing residues.     

Selection response to fleece weight,wool characteristics,and heritability estimates in yearling Romney sheep

The juvenile live weights, yearling fleece weight and wool characteristics of 2987 Romney progeny of 114 sires born over 9 breeding seasons in a fleece-weight-selected and a random control line were analysed. The high fleece weight-selected flock performance was higher (P < 0.001) for weaning weight and spring weight (6.9 and 8.4%), higher (P < 0.001) for greasy and clean fleece weight (23.8 and 24.3%), and also higher (P < 0.001) for FD by 1 μm, staple length by 6 mm, and wool yellowness by 0.3 unit than random control yearling sheep. Heritability estimates for weaning and spring live weight, greasy fleece weight, clean fleece weight, yield, fibre diameter, staple length, staple strength, loose wool bulk, brightness and yellowness were 0.15, 0.51, 0.35, 0.36, 0.40, 0.57, 0.41, 0.24, 0.46, 0.12 and 0.14 respectively. The heritability estimates are within the range of the long wool sheep breeds studied previously. The high selection differential achieved in the initial screening commercial flocks however facilitated to approach a selection response peak in a shorter selection duration and thus resulted in a non-significant genetic gain in greasy fleece weight when averaged over the 9 years of selection.     

饲粮精粗比对瘤胃内纤维消化动力学参数的影响

用三头瘘管牛、三种精料水平的饲粮(其精料比分别为:5％、40％和75％),按3×3拉丁方设计,测定了放置在瘤胃内的尼龙袋中的氨化麦秸粉在8—96小时间的中性洗涤纤维的残留率。按照 Waldo 及 Mertens 的纤维消化动力学模型配合回归曲线,以检验饲粮的不同精粗比对瘤胃内纤维消化动力学参数的影响。同时用铬媒染纤维法测定了瘤胃食糜的流通速度常数(Kp)。结果表明:①瘤胃内饲料纤维的消化动力学参数受饲粮精料比的影响,消化停滞期 L 有随精料比的增加而延长的趋势。消化速度常数(Kd)和可消化度(PED)在低、中(5％、40％)精料比水平间差异不显著,而高(75％)精料水平与低中精料水平比,Kd 和 PED 有显著的减少。在限量饲喂的情况下,各精料水平间,Kp 的差异不显著,但高精料水平的 Kp有降低的趋势。②在为体重1.7％的进食水平下,饲料纤维在瘤胃内的有效消化度(EED),有随精料水平增加而降低的趋势。③使用尼龙袋法,不同时间点的纤维残留率(Rt)对 EED 的线性回归,以 R_(48)对 EED 的相关最好(r=0.82)。     

柳树纤维性状遗传变异的研究

柳树的纤维长与纤维素含量在苗期即有显著差异，其纤维长的遗传变异，无论是在杂种（家系）间，还是在杂种（家系）内无性系间都是显著的。纤维直径和长径比尽管在苗期的差异不显著，但在林期与纤维长一样，无性系间的差异是极显著的。通过杂交组合和无性系选择改良柳树的纤维性状是可行的。无性系内不同年龄间纤维性状的差异是显著的，这为确定纸浆林的轮伐期提供了参考依据。     

羊毛纤维直径与其他经济性状的相关性研究

对羊毛纤维直径与毛量、体重、毛量组成成分、羊毛弯曲度、羊毛纤维强度、体脂含量、繁殖性能等性状的相关性研究进展及现状进行了综述。