Motility of the reticulum and rumen of sheep given juice-extracted pasture

1. Sheep were fed on different diets of juice-extracted herbage to determine what effect juice-extraction had on reticulo-rumen motility. 2. The frequency of A and B sequences of contraction of the reticulo-rumen were recorded during eating, rumination and inactivity for continuous periods of 24–72 h by using integrated electromyograms obtained from electrodes implanted in the musculature of the reticulum and cranial dorsal rumen. 3. Animals were fed on herbage in which approximately 200 g/kg dry matter had been removed in juice extracted from ryegrass (Lolium perenne), white clover (Trifolium repens), mixed ryegrass–white clover and lucerne (Medicago saliva). 4. Over all the frequency of A sequences of contraction did not differ in animals fed on pressed herbage or the unpressed material from which it was derived, although it was slower during rumination on some of the pressed material. In contrast, the frequency of B sequences was higher on the pressed material. The frequencies of contraction of A and B sequences in animals fed on pressed herbage was related to the activity of the animals in the order eating > rumination > inactivity. 5. Changes in reticulo-rumen motility due to juice extraction were small and the frequencies of A and B sequences of contraction in sheep fed on pressed herbage were in the range encountered in ruminants consuming more conventional foods

Effect of previous handling experiences on responses of dairy calves to routine husbandry procedures

The nature of human–animal interactions is an important factor contributing to animal welfare and productivity. Reducing stress during routine husbandry procedures is likely to improve animal welfare. We examined how the type of early handling of calves affected responses to two common husbandry procedures, ear-tagging and disbudding. Forty Holstein–Friesian calves (n = 20/treatment) were exposed to one of two handling treatments daily from 1 to 5 weeks of age: (1) positive (n = 20), involving gentle handling (soft voices, slow movements, patting), and (2) negative (n = 20), involving rough handling (rough voices, rapid movements, pushing). Heart rate (HR), respiration rate (RR) and behaviour (activity, tail flicking) were measured before and after ear-tagging and disbudding (2 days apart). Cortisol was measured at −20 (baseline), 20 and 40 min relative to disbudding time. There were no significant treatment differences in HR, RR or behaviour in response to either procedure. However, the following changes occurred across both treatment groups. HR increased after disbudding (by 14.7 ± 4.0 and 18.6 ± 3.8 bpm, positive and negative, respectively; mean ± s.e.m.) and ear-tagging (by 8.7 ± 3.1 and 10.3 ± 3.0 bpm, positive and negative, respectively). After disbudding, there was an increase in RR (by 8.2 ± 3.4 and 9.3 ± 3.4 breaths/min, positive and negative, respectively), overall activity (by 9.4 ± 1.2 and 9.9 ± 1.3 frequency/min, positive and negative, respectively) and tail flicking (by 13.2 ± 2.8 and 11.2 ± 3.0 frequency/min, positive and negative, respectively), and cortisol increased from baseline at 20 min post procedure (by 10.3 ± 1.1 and 12.3 ± 1.1 nmol/l positive and negative, respectively). Although we recorded significant changes in calf responses during ear-tagging and disbudding, the type of prior handling had no effect on responses. The effects of handling may have been overridden by the degree of pain and/or stress associated with the procedures. Further research is warranted to understand the welfare impact and interaction between previous handling and responses to husbandry procedures

Reduced Cortisol and Metabolic Responses of Thin Ewes to an Acute Cold Challenge in Mid-Pregnancy: Implications for Animal Physiology and Welfare

Background: Low food availability leading to reductions in Body Condition Score (BCS; 0 indicates emaciation and 5 obesity) in sheep often coincides with low temperatures associated with the onset of winter in New Zealand. The ability to adapt to reductions in environmental temperature may be impaired in animals with low BCS, in particular during pregnancy when metabolic demand is higher. Here we assess whether BCS affects a pregnant animal’s ability to cope with cold challenges. Methods: Eighteen pregnant ewes with a BCS of 2.760.1 were fed to attain low (LBC: BCS2.360.1), medium (MBC: BCS3.260.2) or high BCS (HBC: BCS3.660.2). Shorn ewes were exposed to a 6-h acute cold challenge in a climate-controlled room (wet and windy conditions, 4.460.1uC) in mid-pregnancy. Blood samples were collected during the BCS change phase, acute cold challenge and recovery phase. Results: During the BCS change phase, plasma glucose and leptin concentrations declined while free fatty acids (FFA) increased in LBC compared to MBC (P,0.01, P,0.01 and P,0.05, respectively) and HBC ewes (P,0.05, P,0.01 and P,0.01, respectively). During the cold challenge, plasma cortisol concentrations were lower in LBC than MBC (P,0.05) and HBC ewes (P,0.05), and FFA and insulin concentrations were lower in LBC than HBC ewes (P,0.05 and P,0.001, respectively). Leptin concentrations declined in MBC and HBC ewes while remaining unchanged in LBC ewes (P,0.01). Glucose concentrations and internal body temperature (Tcore) increased in all treatments, although peak Tcore tended to be higher in HBC ewes (P,0.1). During the recovery phase, T4 concentrations were lower in LBC ewes (P,0.05). Conclusion: Even though all ewes were able to increase Tcore and mobilize glucose, low BCS animals had considerably reduced cortisol and metabolic responses to a cold challenge in mid-pregnancy, suggesting that their ability to adapt to cold challenges through some of the expected pathways was reduced

Inhibitory effects of short intravascular infusions of propionate on reticulo-rumen motility in the sheep

The effect of short infusions into the hepatic portal vein of propionate on reticulo-rumen motility was examined in conscious sheep. Infusions of 10 min duration of propionate at 1-6 mmol.min into the portal vein reduced the frequency and amplitude of reticulum and rumen contractions, especially the amplitude of rumen contractions. Inhibitory effects were not confined to the portal route and were also obtained via the jugular vein, carotid artery, coeliac artery and anterior mesenteric artery. Butyrate was also effective, but acetate much less so and NaCl almost without effect. The inhibitory responses remained after section of nerves to the liver. It appears unlikely the effects reflexly originate from the liver or are derived centrally

Aconitine induces prolonged seizure-like events in rat neocortical brain slices

Aconitine effects on the hippocampal slice preparation have been well documented and include acute inhibitory and prolonged excitatory effects. To date, the effect of aconitine on neocortical activity has not been investigated. The aim of this study was to characterise the acute and long term effects of aconitine on cortical local field potential activity. Neocortical slices from juvenile Sprague–Dawley rats were perfused at room temperature with aconitine in normal artificial cerebrospinal fluid (aCSF) (n = 10). Spontaneous local field potential activity was recorded from the somatosensory cortex. The calcium dependence of aconitine-induced activity was investigated using low-calcium aCSF (n = 8). To isolate sodium and N-methyl-d-aspartate (NMDA) channel effects, phenytoin (n = 4) and 2-amino-5-phosphono-pentanoic acid (APV) (n = 6) were co-administered with aconitine, respectively. Aconitine consistently induced a dramatic increase in population “spike” activity after prolonged (89.5 ± 36.6 min) application in normal aCSF. This activity surge was eliminated in low-calcium aCSF and when aconitine was co-administered with phenytoin and APV. The acute effects of aconitine application were variable and included an increase in the frequency of population spikes, appearance of oscillatory seizure-like activity and prolonged bursts of multiunit activity. No acute inhibitory effects were observed. Aconitine has acute and prolonged excitatory effects on neocortical activity. The latter is effected by calcium-dependent mechanisms, in keeping with known effects of aconitine on hippocampal slices. Both sodium and NMDA channels are involved in mediating the calcium-dependent aconitine effects

Measurement of feeding motivation in sheep and the effects of food restriction

The availability of food is a crucial factor determining the health and growth of animals. Prolonged or severe food restriction will trigger the subjective state of hunger, which could potentially reduce welfare. We refined a methodology for the measurement of feeding motivation as an indicator of hunger, evaluated the effects of food restriction on feeding motivation in ewes (Ovis aries) and applied a behavioural demand analysis to the data. Sixteen ewes were exposed to five different cost levels (i.e., 2, 6.6, 12.1, 22, or 40 m walking distances per reward) and two feeding levels (24 h restriction and an un-restricted control). We found that 24 h restricted ewes worked for a higher number of rewards (P < 0.001), walked a greater total distance (P < 0.001) and approached the feeding station faster on the first visit (P < 0.001). Therefore, the methodology was able to detect differences in feeding motivation between restricted and control ewes and is a potential indirect indicator of hunger. A generic demand function fitted to the data showed that the elasticity of demand, the maximum price paid (Pmax) and maximum expenditure (Omax) were not sensitive indicators of motivation, probably because we did not generate a complete demand curve. Imposing a cost by providing sheep with the opportunity to walk for their food could be a valuable tool in establishing acceptable feeding levels from an animals’ perspective. However, more research on validating behavioural demand measures as indicators of motivation is needed

Motivation to obtain a food reward of pregnant ewes in negative energy balance: Behavioural, metabolic and endocrine considerations

Low food availability often coincides with pregnancy in grazing animals. This study investigated how chronic reductions in food intake affected feeding motivation, and metabolic and endocrine parameters in pregnant sheep, which might be indicative of compromised welfare. Ewes with an initial Body Condition Score of 2.7 +/- 0.3 (BCS: 0 indicates emaciation and 5 obesity) were fed to attain low (LBC 2.0 +/- 0.0,), medium (MBC 2.9 +/- 0.1) or high BCS (HBC 3.7 +/- 0.1) in the first trimester of pregnancy. A feeding motivation test in which sheep were required to walk a set distance for a palatable food reward was conducted in the second trimester. LBC and MBC ewes consumed more rewards (P=0.001) and displayed a higher expenditure (P=0.02) than HBC ewes, LBC ewes also tended to consume more rewards than MBC ewes (P=0.09). Plasma leptin and glucose concentrations were inversely correlated to expenditure (both P<0.05) and appear to be associated with hunger in sheep. LBC ewes were in negative energy balance, with lower muscle dimensions, plasma glucose, leptin, insulin, cortisol, and insulin-like growth factor-1 concentrations and higher free fatty acids concentrations compared to HBC ewes; metabolic and endocrine parameters of the MBC ewes were intermediate. The high feeding motivation and negative energy balance of low BCS ewes suggested an increased risk of compromised welfare. Imposing even a small cost on a food reward reduced motivation substantially in high BCS ewes (despite high intake when food was freely available). Assessment of a willingness to work for rewards, combined with measures of key metabolic and endocrine parameters, may provide sensitive barometers of welfare in energetically-taxed animals