John Piltz

Annual ryegrass (Lolium rigidum) seed survival and digestibility in cattle and sheep

A trial was conducted to investigate the survival and digestibility of annual ryegrass (ARG) seed (Lolium rigidum L.) eaten by sheep and cattle. Sheep (n= 8) and cattle (n = 8) were fed a basal diet containing 1:1 lucerne chaff:oaten chaff with (ARG) or without (control) the inclusion of 20% total dry matter of annual ryegrass seed in a changeover design. Intake was restricted to 17 g/kg liveweight. Digestibility of the control diet was lower (P<0.01) for sheep than cattle. Annual ryegrass seed was present (P<0.01) in the faeces of both sheep and cattle within 24 h of first ingestion. Some 10.8 and 32.8% of seed ingested was excreted by sheep and cattle respectively, with 3.9% (sheep) and 11.9% (cattle) remaining germinable. Annual ryegrass seed continued to be excreted by both sheep and cattle up to 5 days after removal from the diet. Dry matter digestibility of the annual ryegrass diet was 53% in cattle.

Use of delactose whey permeate as a supplement for cattle on a cereal straw based diet

The potential use of delactose whey permeate (delac) as an energy supplement for cattle offered low quality roughage was investigated. Young steers (initial liveweight 267 kg) were fed delac at 0, 0.25, 0.5 or 0.75% of liveweight. The steers had ad libitum access to oaten straw and were fed a protein supplement (cottonseed meal) at 1.33 kg/head once daily with the delac. Total intakes increased with increasing levels of delac. During the first half of the experiment, cattle offered delac had higher intakes than those not offered delac, but intake did not differ between delac supplemented groups. Furthermore, liveweight gain did not differ between groups. In the second half of the experiment, intake and liveweight gain increased with increasing level of delac in the diet. Intake of oaten straw over the whole experiment was greater with 0.25% delac than with no delac, but declined at higher levels of delac as animals substituted delac for straw in the diet. A storage study, conducted over 6 weeks, indicated a higher rate of microbial spoilage in delac with a lower solids content, however pH remained low. Calculations, based on the actual liveweight, liveweight gain and feed intake results, indicate that delac has a metabolisable energy content of about 11 MJ/kg DM. These results indicate that delac has potential as an energy supplement for cattle on low quality roughage diets and could be used on commercial farms if composition (especially solids content) is consistent and storage issues are addressed. Further investigations into the use of delac, in combination with low cost nitrogen supplements such as urea, are also recommended.

Development of a model for investigation of perennial ryegrass toxicosis in sheep

AIMS To develop a clinical model of perennial ryegrass toxicosis (PRGT) based on feeding a known dose of lolitrem B and ergotamine, and to produce a consistent clinical presentation for assessment of disease pathophysiology, neurological changes and neurohistopathology. METHODS Male lambs, aged between 10–12 months, were randomly assigned to either Treatment (n=9) or Control (n=9) groups. Lambs in the Treatment group received feed containing a novel endophyte-infested perennial ryegrass seed, commencing on Day 0 of the Feeding phase with a low induction dose, then increasing after 3 days to provide 0.16 mg/kg live bodywight (LBW)/day of lolitrem B and 0.054 mg/kg LBW/day ergotamine. Lambs were examined daily and when defined signs of PRGT were observed they were transferred to the Testing phase. Neurological examinations, assessment of gait, surface electromyography (EMG) and mechanosensory nociceptive threshold testing were carried out and blood samples collected during both phases of the trial, with a full necropsy, histopathological examination and measurement of faecal cortisol metabolites (FCM) performed on Day 2 of the Testing phase. RESULTS Typical clinical signs of PRGT, including ataxia of vestibulocerebellar origin leading to stumbling, were observed in all Treatment lambs. The median interval from the start of the Feeding phase to entry into the Testing phase was 21 (min 18, max 34) days. Histopathological characterisation of neurological lesions included the presence of Purkinje cell vacuolation, pyknotic granular layer neurons and proximal axonal Purkinje cell spheroids. Lesions were most apparent within the vestibulocerebellum. Mean root-mean-square voltages from triceps EMG increased in Treatment lambs between Feeding phase Day 0 and Testing phase Day 2 (p<0.001). Daily water intake during the Testing phase for the Treatment group was less than in Control group lambs (p=0.002), and concentrations of FCM at necropsy were higher in Treatment compared to Control lambs (p=0.02). CONCLUSIONS AND CLINICAL RELEVANCE Lolitrem B and ergotamine dosing in feed on a live weight basis combined with neurological/gait assessment provides an effective model for investigation of PRGT and potential therapeutics. Assessment of gait changes using defined criteria and RMS voltages from EMG appear to be useful tools for the assessment of the severity of neurological changes.