A comparative study of the effect of dietary nitrogen (N) content [Low: 11·0; Medium-Low (MLow): 16·7; Medium-High (Mhigh): 23·1; High: 29·2 N g/kg dry matter (DM)] on apparent digestibilities, rumen fermentation and N balance was conducted in coarse wool Tibetan sheep and Gansu Alpine fine-wool sheep at Wushaoling in the northeast of the Qinghai-Tibetan Plateau. It was hypothesized that responses would differ between breeds and that responses would favour Tibetan over fine-wool sheep at low N intakes. Eight wethers [four Tibetan sheep and four fine-wool sheep, 20–24 months old; body weight ± standard deviation was 52 ± 3·2 kg] were used in two concurrent 4 × 4 Latin square designs. Dry matter, organic matter, neutral detergent fibre and acid detergent fibre digestibilities were higher in Tibetan than fine-wool sheep when fed the Low, MLow and High N diets while N retention was higher when the animals were fed the Low and MLow N diets. Tibetan sheep had a higher rumen pH than fine-wool sheep; however, total volatile fatty acids were similar between breeds. Molar proportions of acetate were higher but propionate and butyrate lower in Tibetan than fine-wool sheep. In addition, Tibetan sheep had higher concentrations of ruminal free amino acid-N and soluble protein-N than fine-wool sheep. Plasma and saliva urea-N concentrations were higher in Tibetan than fine-wool sheep when supplied with the Low N diet. It was concluded that Tibetan sheep were better able to cope with low N feed than fine-wool sheep because of the higher N retention and higher DM and fibre digestibilities with Low and MLow diets.

In members of the Bocavirus genus, that contain three open reading frames (ORFs) of the Parvovirinae subfamily, porcine bocaviruses (PoBoVs) exhibit the most genetic diversity. Based on the ORF2-encoded viral protein (VP1) classification, the six reported porcine bocaviruses were grouped into four species: PoBoV1 (porcine boca-like virus or PBoLV), PoBoV2 (porcine parvovirus 4 or PPV4), PoBoV3 (PBoV1/PBoV2) and PoBoV4 (6V/7V), with PoBoV3 and PoBoV4 each having two genotype viruses. All four PoBoV species were detected in the 166 samples collected in 2010 from swine herds located in ten provinces of China. The detection rates for PoBoV1-4 were 28·9%, 6·6%, 19·3% and 39·7%, respectively. The co-infection combinations involving these six porcine bocaviruses in the collected samples were very complex. Furthermore, mixed infections with viruses from other families (porcine reproductive and respiratory syndrome virus, classic swine fever virus and porcine circovirus type 2) were also detected.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Grasslands are the most extensive terrestrial landscapes and ecosystems in China and face growing degradation. A policy to protect the grasslands established in 2001 (the Grassland Ban Policy [GBP]), involves four management practices including grazing bans, keeping grasslands fallow, grazing rotations and rearing livestock in sheds. A questionnaire was developed and used to establish attitudes towards and beliefs about the GBP in different sectors (farming households, local officials and extension workers), assess problems with GBP implementation and identify possible solutions. Acceptance of the GBP by farmers varied from 64% in the north to 95% in the north-west region. The responses of both local officials and extension workers indicated that GBP implementation was greater in the central region than in the north-west region. Most farmers changed their livestock production system from grazing to stall feeding after implementation of the GBP, while both farmers and extension workers reported that high input costs were the most serious problem in stall feeding. Incentives need to be provided for sustainable implementation of the GBP by different stakeholders. Improved collaboration among farmers, local officials and extension workers is needed for technology transfer and policy implementation. Furthermore, the role of non-governmental organizations needs to be strengthened in implementation of the GBP.

Field experiments were conducted at the farm of Qinghai Academy of Animal and Veterinary Science, Xining, China during 1996/97 to determine the effects of level of food intake on the urinary excretion of purine derivatives (PD), creatinine and nitrogen in yaks (Bos grunniens). Two experiments were carried out with three female yaks (initial body weight 173–187 kg, age 5 years). For Expt 1 a 3×3 Latin square experimental design was used with three levels of oat hay (nitrogen 13·5 g/kg dry matter (DM)) intake treatments, i.e. 0·3, 0·6 and 0·9 of voluntary intake (1·3–3·5 kg DM/d). Each treatment lasted for 17 days and the samples were collected during the last 7 days of each period. For Expt 2 the animals were fed the same oat hay as in Expt 1 for 3 weeks at a level equivalent to the estimated energy maintenance requirement (M) (1·5–2·2 kg DM/d). The intake was then reduced to 0·6 M on day 1, 0·3 M on day 2 and zero from day 3 until day 10. The animals were re-fed in the reverse order for 3 days. Of the PD, only allantoin and uric acid were present in the urine. The proportions of allantoin and uric acid were 0·86 and 0·14 respectively for both experiments. There was no response of creatinine and nitrogen excretions to feed intake. The rates of PD excretion per kg digestible organic matter (DOM) or digestible dry matter (DDM) were 13·5 and 13·6 mmol respectively. As expected, urinary PD excretion increased significantly (P<0·001) with increasing intake of DDM and DOM. The daily fasting PD, creatinine and nitrogen excretions amounted to 0·22±0·02 (S.E.), 0·25±0·01 mmol/kg W0·75 and 314±24·2 mg/kg W0·75 respectively. The results suggest that it is possible to establish a method for estimating intestinal microbial protein flow based on PD excretion in yaks.

Previous studies in sheep and cattle have demonstrated that the urinary excretion of purine derivatives (PD) provides an index of the intestinal flow of microbial protein (Chen et al. 1990). Yak is the most important ruminant species in Tibetan Plateau. It was of interest to establish whether the approach of PD excretion to estimate microbial protein supply is applicable in yaks. The objective of this work is to measure the effect of fasting and different levels of feeding on PD excretion in yaks.

The feeding experiments were carried out in Xi-ning, China at an altitude of 3100m and a latitude of 36.8° N. Six 5-year old female yaks were used and 3 experiments were completed.