Effect of different levels of dietary fiber on intestinal development and caecum fermentation traits of weaning rabbits

A common problem in rabbit production is the occurrence of digestive disorders just after weaning, and fiber is well known to be bcncficiai for rabbit gastrointestinal health. In order to test the hypothesis that whether the good points of fiber increases with its dietary content, three isoenergetic and isonitrogenous diets and ninety mixed-sex New Zealand rabbits weaned 35-d-old were used. The results can be concluded as following： （1） Average daily feed intake （ADFI） tended to increase （i〉=0.058） while average daily gain （ADG） （p=0.001） and feed conversion ratio （FCR） （p〈0.001） deteriorated with increasing dietary ADF content. The highest morbidity was observed in the rabbits fed the highest dietary ADF concentration. （2）A decreasing coefficient of total tract apparent digestibility （CTTAD） of dry matter （DM） and crude protein （CP） was obtained with the increase of dietary fiber level （p〈0.001 and =0.003）. （3） A significant negative effect of treatments on sucrase and maltase activities in the jejunum was observed （p=0.001 and 0.003）. （4） The volatile fatty acid （VFA） concentration （p=0.011） and butyric acid （% total VFA） （P=0.001） dropped while the NH3-N concentration （P〈0.001）, pH （P=0.004） and acetic acid （% total VFA） （P〈0.001） increased with increasing dietary ADF. It was concluded that high fiber level was unfavorable to the rabbits in the first two weeks after weaning.

QTL Analysis for Traits Associated with Feeding Value of Straw in Rice (Oryza sativa L.)

Genetic improvement of the digestibility of rice straw for increasing the utilization of the whole rice plant as feedstuffs is an important way to solve the feedstuffs shortage in southeastern China. To elucidate the genetic basis of the traits affecting the digestibility of rice straw, a rice population of 111 recombinant inbred lines （RILs） derived from a cross of Nekken 2xGaya was used to map the quantitative traits loci （QTLs） for in vitro dry matter digestion （IVDMD）, the percentages of nonstructural carbohydrate （NSC） and acid detergent fiber （exclusive of residual ash, ADFom） in 2005 and 2006. IVDMD was positively correlated with NSC, and negatively correlated with ADFom. A total of 16 QTLs were detected in the two years, and the amounts of variation explained by individual QTLs ranged from 6.9% to 15.5%. Some QTLs for IVDMD and ADFom on chromosome 2 were detected in the two years. On chromosome 2, the interval RM475-RM3515 contained QTLs for IVDMD in the two years and for NSC in 2006 only, while the interval RM3874-RM5305 influenced ADFom in the two years and NSC in 2005 only. At those loci, Gaya contributed favorable alleles to IVDMD and NSC, while Nekken 2 contributed positive alleles to ADFom.

Analysis of Some Important Forage Quality Attributes of Southeastern Wildrye (Elymus glabriflorus) Using Near-Infrared Reflectance Spectroscopy

Southeastern wildrye (Elymus glabriflorus, Vasey ex L.H. Dewey) is a cool-season, perennial grass native to southeastern United States. Recently, there is a growing interest in its development as a grazing and haying forage crop due to its wide area of adaptation across this region. Consequently, there is a great need for the evaluation of its forage quality by rapid, but accurate analytical methods like Near-Infrared Reflectance Spectroscopy (NIRS). In this study, acceptable NIRS calibration models were developed for: dry matter, DM (n = 113, R2 = 0.904, RSCD = 2.54, RSCIQ = 4.65);crude protein, CP (n = 113, R2 = 0.974, RSCD = 5.16, RSCIQ = 5.92);acid detergent fiber, ADF (n = 116, R2 = 0.896, RSCD = 2.35, RSCIQ = 1.28);neutral detergent fiber, NDF (n = 118, R2 = 0.934, RSCD = 2.53, RSCIQ = 3.38);digestible dry matter, DDM (n = 116, R2 = 0.895, RSCD = 2.36, RSCIQ = 1.35);dry matter intake, DMI (n = 115, R2 = 0.924, RSCD = 2.40, RSCIQ = 2.53);and relative feed value, RFV (n = 114, R2 = 0.932, RSCD = 2.94, RSCIQ = 2.81). Prediction of independent validation sets yielded good agreement between the NIRS predicted values and the laboratory reference values for each of: DM (n = 53, R2 = 0.831, RPD = 2.45, RPIQ = 4.24);CP (n = 57, R2 = 0.967, RPD = 5.37, RPIQ = 7.16);ADF (n = 49, R2 = 0.895, RPD = 2.97, RPIQ = 1.51);NDF (n = 53, R2 = 0.928, RPD = 3.75, RPIQ = 4.22);digestible dry matter, DDM (n = 55, R2 = 0.860, RSCD = 265, RSCIQ = 1.15);dry matter intake, DMI (n = 156, R2 = 0.845, RSCD = 2.48, RSCIQ = 2.11);and relative feed value, RFV (n = 55, R2 = 0.916, RSCD = 3.45, RSCIQ = 3.04) contents, indicating that all seven calibration models had good quantitative information. Therefore, precise, accurate, and rapid analysis of these important forage quality attributes of southeastern wildrye can be routinely done using the developed NIRS calibration models.

Mapping of quantitative trait loci for fiber and lignin contents from an interspecific cross Oryza sativa×Oryza rufipogon

Rice straw is always regarded as a by-product of rice production,but it could be a significant energy source for ruminant animals.Knowledge of the genetic variation and genetic architecture of cell wall traits will facilitate rice breeders by improving relevant traits through selective breeding and genetic engineering.The common wild rice,Oryza rufipogon Griff.,which is considered to be the progenitor of Oryza sativa,has been widely utilized for the identification of genes of agronomic importance for rice genetic improvement.In the present study,the mapping of quantitative trait loci (QTLs) for acid detergent fiber (ADF),neutral detergent fiber (NDF),acid detergent lignin (ADL),and ADL/NDF ratio was carried out in two environments using a backcrossed inbred line (BIL) population derived from a cross between the recurrent parent Xieqingzao B (XB) and an accession of Dongxiang wild rice (DWR).The results indicated that all four traits tested were continuously distributed among the BILs,but many BILs showed transgressive segregation.A total of 16 QTLs were identified for the four traits,but no QTLs were in common in two environments,suggesting that environment has dramatic effects on fiber and lignin syntheses.Compared to the QTL positions for grain yield-related traits,there were no unfavorable correlations between grain yield components and cell wall traits in this population.The QTLs identified in this study are useful for the development of dual-purpose rice varieties that are high in grain yield and are also high in straw quality.

Effect of Long-term Experimental Warming on the Nutritional Quality of Alpine Meadows in the Northern Tibet

The nutritional quality of grasslands is closely related to recruitment of young and population dynamics of livestock and wild herbivores. However, the response of nutritional quality to climate warming has not been fully understood in the alpine meadow on the Tibetan Plateau, especially in the Northern Tibet. Here, we investigated the effect of experimental warming(beginning in 2008) on nutritional quality in three alpine meadows(site A: 4313 m, B: 4513 m and C: 4693 m) in the Northern Tibet. Crude protein(CP), neutral detergent fiber(NDF), acid detergent fiber(ADF), crude ash(Ash), ether extract(EE) and water-soluble carbohydrate(WSC) were examined in 2018–2019. Experimental warming only increased the content of CP by 27.25%, ADF by 89.93% and NDF by 41.20%, but it decreased the content of Ash by 57.76% in 2019 at site B. The contents of CP and WSC both increased with soil moisture(SM). The content of CP decreased with vapor pressure deficit(VPD). The combined effect of SM and VPD was greater than air temperature(Ta) in controlling the variations of the CP content, ADF content and nutritional quality. Compared to Ta, VPD explained more of the variation in NDF and Ash content. All of these findings suggest that warming effects on nutritional quality may vary with site and year, and water availability may have a stronger effect on the nutritional quality than temperature in the alpine meadow of the Northern Tibet.