Sheltering behaviour of shorn and unshorn sheep in mixed or separate flocks

Lambing ewes or wethers in mixed flocks of unshorn and recently shorn sheep, in small gently-sloping (1 in 76) paddocks, were examined for evidence of mutual interaction in their sheltering behaviour. Their distribution in paddocks containing a small sheltered area of grass hedges, sited centrally or at the higher or lower boundaries, was compared with that in paddocks without shelters.During calm weather, in daylight, the sheep largely behaved as one flock, but in windy weather, and at night, most shorn sheep congregated in shelter, while unshorn sheep remained away from shelter. There was no evidence that the inclusion of shorn sheep in a flock of unshorn sheep increased the use of shelter by the unshorn sheep; evidence that the presence of unshorn sheep reduced the sheltering behaviour by shorn sheep was equivocal.Both shorn and unshorn ewes and wethers tended to congregate at the higher end of the paddocks, and the use of shelter by shorn sheep declined as the distance of the shelter from the higher end of the paddock increased, despite the absence of alternative shelter. Clearly, the selection of sites on which to establish shelter will have marked effects on the use that sheep make of shelter.     

Sheltering behaviour and lamb mortality amongst shorn Merino ewes lambing in paddocks with a restricted area of shelter or no shelter

A flock of 380 pregnant Merino ewes was shorn and randomised between two 12-ha paddocks. An area of shelter containing five grass hedges 90 m long, 0.5 m wide and 10 m apart was located in the middle of one paddock at a site that was not previously used as a preferred resting area (camp). The sheep in this paddock used the shelter extensively at night and also during the day when the weather was cold and windy. This use of shelter continued for seven weeks and subsequently some use of the shelter was made when the sheep were returned to the paddock after an absence of eight days. Sheep from the un-sheltered paddock given access to the shelter for these eight days made no use of it.Lamb mortality in the sheltered paddock (about 20%) was half that in the unsheltered paddock; about 50% of lambs born appeared to be twins. Deaths of lambs from apparent hypothermia were much more frequent during several days of windy weather than during calm weather, and were higher in the unsheltered paddock (12%) than in the sheltered paddock (5%). Significant wet weather was not experienced.It may be possible to train sheep to spend resting periods in sheltered areas by shearing during the cooler months; subsequently a high proportion may lamb in shelter, thereby reducing lamb mortality.     

Use of shelter and selection of lambing sites by shorn and unshorn ewes in paddocks with closely or widely spaced shelters

This paper extends previous findings that recently shorn ewes make extensive use of the shelter provided by grass hedges, of a phalaris hybrid, 20 m apart, whereas unshorn ewes make no use of the available shelter. In the present study, shorn sheep were observed sheltering near phalaris hedges, 240 m apart, for about 30% of the time during the day and 60% of the time during the night, compared with 60% and 80%, respectively, for shelters 20 m apart. These differences can only partly be accounted for on the basis of chance occupancy of shelter, since 10% fewer sheep appeared to move to shelter with the spacing of 240 m than with a spacing of 20 m. Shelters were also used extensively by shorn ewes during periods of inclement weather during the day. Lambs made slightly more use of shelter than their mothers. The use made of shelters in the form of fences of black, plastic mesh (60% porosity), 240 m apart, was only 70% of the use made of similarly spaced phalaris hedges. Ewes, with the exception of unshorn ewes that were still to lamb, spent a disproportionately large amount of the time at the eastern or up-hill end of the paddocks.During the day, the proportion of shorn ewes lambing in the lee of the widely spaced shelters was similar to the proportion of ewes in shelter (about 30%), but during the night when 50–70% of the ewes were in shelter, the proportion of lambing sites in shelter was well below this range. In contrast, while only 10–20% of unshorn ewes lambed near the widely spaced shelters, this was several fold higher than the small proportion of non-lambing unshorn ewes in shelter. In addition, of the shorn and unshorn sheep that lambed away from shelter in these paddocks, some 50% more than expected on the basis of even distribution lambed in close proximity to the boundary fences; this disproportionate distribution was not seen in ewes that had not lambed.These results indicate that perhaps half of these Merino ewes isolated themselves from high concentrations of other sheep, for lambing, and in the process lambed near boundary fences or shelters. It is not clear whether the movement to isolated lambing sites is deliberate or fortuitous due to restlessness arising from physical discomfort.Lambing sites of both shorn and unshorn ewes were more concentrated near the eastern or up-hill end of the paddocks than the positions of ewes that had not lambed; the eastern end was clearly a preferred lambing area.The provision of ample shelter near any preferred lambing areas in large paddocks could lead to many lambs being born in shelter and hence to a reduction in mortality of lambs born during inclement weather.     

Behaviour of the ewe and lamb at lambing and its relationship to lamb mortality

A number of behavioural traits associated with the maternal instinct of sheep were studied under paddock conditions over a range of breeds, age, climate, nutrition and locations in five lambings in south Western and north Western Australia. There was very considerable variation between ewes in any group in the occurrence and timing of each trait. There were few differences due to breed, age of ewe, nutrition, climate or location in the behaviour of the ewe before and during parturition. Nearly all the differences that occurred were in the frequency of pawing the ground before and during labour. Fewer Southdowns and Merinos pawed the ground than ewes of other breeds. Also this trait occurred more in summer than in winter in south Western Australia, and less here than in north Western Australia.The behaviour of the ewe during the post partum period was highly predictable. She normally stood and commenced cleaning within 1 min of birth. Cleaning commenced at the head and progressed down the body. Desertions and other forms of aberrant behaviour were uncommon.There were no biologically significant differences in length of labour, time from birth to stand and time from stand to first drink due to breed, age, pre-lambing nutrition, climatic conditions or location.Second-born twins were delivered after a significantly shorter labour than first-born twins. In one series of observations twins took longer to drink than singles. Type of birth did not influence the time taken for the lamb to stand.Rectal temperature three hours after birth dropped significantly when rainfall exceeded 2 mm during the 3 h.Lamb mortality increased significantly in wet weather in winter and most lambs which died more than 3 h after birth had a depressed rectal temperature at 3 h. The ewes of lambs which died after standing tended to have longer than average labour. Poor maternal behaviour per se was the cause of 16% of lamb deaths and failure of the lamb to drink after standing caused 23% of lamb deaths in winter in south Western Australia. In summer in both environments heat stress was the primary cause of lamb deaths.     

The impact of lambing stress on post-parturient behaviour of sheep with consequences on neonatal homeothermy and survival

During lambing the expression of an appropriate behavioural response from both the ewe and the lamb are extremely important to lamb survival. The aim of this study was to show the effect of length and difficulty of the birth process on the expression of maternal and neonatal behaviour with consequences on homeothermy and survival of the neonate lamb. Data were collected from 61 Finnish Landrace × Rahmani crossbred (second generation) primiparous ewes and their single born lambs. Based on the average length of parturition, the ewes were grouped into short birth (less than 32.5 min) and long birth (equal to or higher than 32.5 min) classes. The data recorded include maternal and neonatal behaviour, lamb body temperature over the first 3 days of life and survival rate of the neonate lamb during the first week after birth. Blood samples were also collected from the lamb, pre-suckling and at 24 and 72 h after birth. The obtained sera were assayed for thyroid hormones (T₃ and T₄) that are associated with heat production. Ewes that had prolonged and difficult births did not show competent maternal behaviour compared to mothers with short and un-complicated deliveries, as they were slower to begin grooming their lambs after birth, spent less time licking their lambs, made less low-pitched vocalizations and nosing, were more likely to show rejection behaviour (10.34 % vs 5.4 %, P < 0.05), and were more likely to move away when the lamb sought the udder in an attempt to suck (acceptance rate, 55.5 % vs 64.79 %, P < 0.05). Similarly, lambs from a prolonged and difficult birth were significantly less vigorous after birth, as they had taken more time to stand, reach the udder and to suck successfully. These lambs had lower serum concentrations of T₃ and T₄, and they also had a reduced ability to maintain body temperature after birth. This effect persisted over the first 3 days of life and was associated with higher neonatal mortality in the first week after birth (11.54 %), compared to lambs from short and non-stressful birth processes (2.86 %, P < 0.01). From the present study, it can be concluded that, prolonged deliveries with birthing difficulty were one of the main causes of death of large, single-born lambs, as these complications cause the expression of inappropriate behavioural responses from both the ewe and neonatal lamb. Thus, interventions designed to reduce the incidence of prolonged parturitions are likely to be associated with better welfare for the ewe and the lamb and consequently improved lamb homeothermy and survival.     

Effect of time of early weaning and time of lambing on accelerated lambing in Polypay sheep

Effects of early weaning, lactation, and day-of-year lambing on the ability of Polypay ewes to rebreed following winter and summer lambings were evaluated. Winter lambing ewes did not successfully rebreed while lactating. However, when winter-born lambs were weaned at 31 days postpartum, more ewes rebred and produced summer lambs (35.7%) than when lambs were weaned at 41 days postpartum (23.6%). Ewes that lambed during the early part of the winter lambing period had an advantage over later lambing ewes in the percentage which subsequently lambed the following summer. This was apparently the result of a difference in length of breeding exposure rather than a higher fertility rate during the early part of the breeding period. When summer lambing ewes were rebred during the early part of the summer breeding period (late summer to early fall), stress associated with lactation did not affect subsequent winter lambing performance. Summer lambing ewes belonging to a late weaning (80 days) treatment group did not differ (P>0.05) from those belonging to an early weaning (31 days) treatment group in winter fertility, prolificacy, day-of-year lambing or lambing interval.     

The effects of thermoregulatory behaviour on the heat loss from shorn sheep as measured by a model ewe for micro-climate integration

A thermostatic, taxidermic model sheep was used to assess the effects of thermoregulatory behaviour of shorn sheep at night in a winter environment with mean air temperatures slightly above freezing, variable wind speeds, rain and cloud cover.Testing in a wind tunnel showed that angle of incidence to the wind had no effect on heat loss at wind speeds < 2 m s⁻¹ (7 km h⁻¹), but at wind speeds of 7 m s⁻¹ (25 km h⁻¹), heat loss was 14% greater when the model was side-on rather than tail- or head-on to the wind.In tests on pasture, standing side-on to the early morning sun reduced heat loss from the model by 33%. Three hours “lying” on the lee side of a 1-m high synthetic Sarlon windbreak on a frosty night resulted in a reduction in heat loss of 6% below that when standing or 11% below that in a standing position in the open. When the model was placed in the centre of a tight group of 16 shorn sheep, its heat loss was reduced by an average of 14%.Heat loss was also reduced if the model was moved from the open, to regions of lower wind speed adjacent to windbreaks; the effect was greater on the leeward than the windward side.The reduction one metre leeward of a grass hedge (hybrid Phalaris) was 15% compared with 12% one metre leeward of a synthetic (Sarlon) windbreak, which is consistent with the preference of shorn sheep to shelter by Phalaris rather than Sarlon windbreaks.The microclimates where heat loss from the model were lowest correspond to those sought by shorn sheep in cold weather, and the results indicate that shorn sheep have very sensitive thermosensing mechanisms and efficient thermoregulatory behaviour.     

The genetics of resistance and resilience to Haemonchus contortus infection in young merino sheep

Young Merino sheep in 60 half-sib groups, totalling over 1000 lambs, were given a single dose of 11,000 Haemonchus contortus larvae. Resistance was measured, together with productivity during infection and when uninfected. One half-sib group exhibited an extremely high level of resistance; its sire was postulated to be the carrier of a major resistance gene. Genetic parameters were estimated for productivity during infection and in the absence of infection, for resistance as measured by faecal egg count and haematocrit, and for resilience as measured by the depression of productivity due to infection. The heritability of faecal egg count was estimated at 0.3, that for haematocrit after infection at 0.4. The heritability of resilience was too low to allow substantial progress by direct selection for this trait. Genetic correlations between resistance to infection and production traits when uninfected were not significantly different from zero. It was concluded that selection for polygenically controlled resistance would lead to substantial progress for this trait and would also increase productivity of infected animals.     

The effect of clenbuterol on time of lambing and neonatal death loss

Two experiments were conducted to test the ability of clenbuterol, a beta-sympathomimetic agonist, to delay lambing. Ewes in all experiments were induced to lamb with 2.5 mg of flumethasone given intramuscularly on Day 141, 142 or 143 of gestation. Beginning on the day of flumethasone administration and continuing daily until lambing, ewes in Experment 1 were given injections intramuscularly (i.m.) with either 1) vehicle solution at 2200 h, 2) 240 ug of clenbuterol at 2200 h or 3) 240 ug of clenbuterol at 1600 and at 2200 h. There was a greater proportion of ewes lambing between 0800 h and 1600 h (P<0.01) and more stillbirths (P=0.05) in the groups which received clenbuterol than in the vehicle control group. Experiment 2 was conducted to determine if a lower dosage of clenbuterol, given as a single injection 37 h after flumethasone, would delay lambing without increasing the proportion of stillbirths. Ewes received either the vehicle solution, or 36 or 146 ug of clenbuterol. Lambing was delayed in the group which received 146 ug but not 36 ug of clenbuterol. There were no adverse effects of treatment on lamb survival in Experiment 2.     

The enzymes of glutathione synthesis in erythrocytes from gsh-high and gsh-low type australian merino sheep

• 1.1. The activity of γ-glutamylcysteine synthetase and glutathione synthetase was determined in erythrocytes from Australian Merino sheep of different erythrocyte haemoglobin, potassium and GSH types.
• 2.2. The activity of γ-glutamylcysteine synthetase was diminished in GSH-low type erythrocytes, but glutathione synthetase had a similar activity in erythrocytes of both GSH types.
• 3.3. γ-Glutamylcysteine synthetase from erythrocytes of both GSH types was inhibited by physiological concentrations of GSH, but a greater inhibition of the enzyme from GSH-low type erythrocytes occurred at low GSH concentrations.

     

Biologic activity of the tachykinins on lamb and sheep gallbladder

In this study, we examined the activity of the tachykinins (TKs) on lamb and sheep isolated gallbladder and whether the TKs are involved in the capsaicin-induced activity in these tissues. Substance P (SP) and physalaemin (PHYS) contracted lamb gallbladder, PHYS-induced striking tachyphylaxis. This tissue was nearly insensitive to neurokinin A (NKA), neurokinin B (NKB), septide, and capsaicin. As in lamb tissues, SP and PHYS both contracted sheep gallbladder although PHYS induced no tachyphylaxis. At doses that had no effect on lamb tissue, NKA, NKB, septide, and capsaicin contracted sheep gallbladder. Our findings indicate that TK receptors differ in adult and young ovine gallbladder. The activity of PHYS on lamb gallbladder could depend on the existence of an unusual binding site, carrying one or more residues critical for the N-terminal sequence present in PHYS but not in SP.     

Climatic influences on the mortality of sheep during long-distance sea transport

Research on the causes of sheep death in sea voyages from Australia to the Middle East is limited, in particular little is known about the influence of climatic factors. Mortality data from 417 shipments of sheep exported over an 11-year period (November 2004 to June 2015) were modelled retrospectively to determine associated climatic factors. The statistical analysis were performed for both the full data set with 417 voyages based on actual and estimated departure and arrival dates and a restricted data set with 71 voyages based on actual dates. The results of the full data set demonstrated a seasonal mortality pattern, with more deaths occurring on sea voyages leaving Australia in the southern hemisphere winter or spring than those departing in Australian summer or autumn. Heat stress and inadequate fat mobilisation for energy supply when sheep are inappetant on shipments may explain this seasonality. Based on these two models, the voyage and weather factors associated with sheep mortalities included departure year, autumn departure in the southern hemisphere, voyage duration, single or multiple loading port(s), weekly mean dry bulb temperature and wind speed at departure ports, and humidity at destination ports. Significant correlations were observed between weather variables at the departure ports in the Australian winter and a high sheep mortality rate during voyages. This, together with the anticipated increased heat stress risk as a result of climate change, suggests that there could be review of the trade from Australia in the southern hemisphere winter. The influence of weather at the departure ports should be considered in sheep mortality prediction models, especially Australia’s heat stress risk assessment model.     

The insect faunas of pear and apple orchards and the effect of windbreaks on their distribution

Two coir netting windbreaks, each 7 m tall and 46 m long, were erected in a pear and an apple orchard, to try to increase the number of insect pollinators present at blossom time. The flying insects were sampled with suction traps and insects visiting trees were sampled by examining marked clusters of blossom. The mean aerial density was calculated for each of the forty-two taxa, mainly families, identified from the aerial population. There were about 50% more insects flying in the pear than in the apple orchard. The distribution of flying insects was greatly affected by the windbreaks, and the sheltered zone contained three times as many of most species, and more than three times as many Chironomidae, Psychodidae and Bibionidae as elsewhere. Small flies were the most abundant insects in the air, in both orchards. In the pear orchard large insects comprised only about 7 % of the total aerial population, of which honeybees constituted 0–7% and wild bees 0–3%. By contrast, large insects accounted for a greater proportion of the population on blossom. The reasons for this are discussed. On apple blossom Syrphidae and honeybees were the insects most often seen, and on pear blossom Bibionidae and Mycetophilidae.     

Nursing behaviour of bighorn sheep: correlates of ewe age,parasitism, lamb age,birthdate and sex

The nursing behaviour of marked bighorn ewes, Ovis canadensis, and their lambs was observed in Alberta, Canada, for 2 years. Suckle duration decreased as lambs grew older. Nursing behaviour in midlactation was correlated with maternal condition; young ewes, ewes with high faecal counts of lungworm (Protostrongylus spp.) larvae, and ewes whose lambs were born late allowed shorter suckles and were less likely to nuzzle their lamb's rump during a suckle. Sons did not appear to receive more milk than daughters. Suckle duration in mid-lactation was correlated with survival for female lambs but not for males. Lambs born late were disadvantaged, probably because nutritious forage was accessible to their mothers only in early lactation.     

Polymorphism at the beta-adrenergic receptor (ADRB3) locus of Merino sheep and its association with lamb mortality

Beta3-adrenergic receptors are predominantly found on the surface of adipocytes and are major mediators of the lipolytic and thermogenic effects of high catecholamine concentrations. Recently, variation in the ovine beta3-adrenergic receptor (ADRB3) gene has been reported to be associated with lamb survival. In this study, polymerase chain reaction-single strand conformational polymorphism analysis of part of the ADRB3 intron was used to genotype 4488 Merino lambs born at 10 farms throughout the South Island of New Zealand. Univariate and multivariate odds ratios for each allele revealed a significant association of the E allele with cdd survival and of the D allele with mortality. This variation at the ADRB3 locus may assist in the genetic selection for survival in Merino sheep.     

Effects of sire breed on ewe dystocia, lamb survival and weaned lamb output in hill sheep systems

A study was carried out on six hill farms, located in the main hill regions of Northern Ireland, over three breeding seasons to investigate the effect of sire breed on ewe dystocia, lamb survival and weaned lamb output. On each farm, groups of 26 to 40 purebred Scottish Blackface ewes (n = 3174) were crossed with Blackface, Swaledale, North Country Cheviot, Lleyn and Texel sires by natural service (year 1) and artificial insemination (years 2 and 3). Each of the mating groups was initially balanced for ewe age, live weight and condition score, and a total of 15 sires of each breed were used over the 3 years. In total, 2272 ewes were recorded at lambing, producing 3451 lambs, over the 3 years. Sire breed had a significant effect (P < 0.001) on lamb birth weight with Blackface and Swaledale the lowest and Texel the highest. The proportion of ewes with dystocia was higher with Texel sires compared with Lleyn, Swaledale and Blackface sires (P < 0.05). Ewes mated to Cheviot sires had more dystocia than those mated to Blackface and Swaledale sires (P < 0.05), while ewes mated to Lleyn sire breed had more dystocia (P < 0.05) than those mated to Blackface sire breed. Most of the incidence of dystocia was attributable to increased lamb birth weight (P < 0.001), and some to litter size (P < 0.05). Swaledale, Cheviot, Lleyn and Texel sire breeds increased the incidence of malpresentations (P < 0.05). Lamb live weight at weaning was higher with Texel- and Cheviot- and Lleyn-sired lambs compared with Blackface- and Swaledale-sired lambs (P < 0.01). The level of lamb mortality at birth was not affected by sire breed. However, lamb mortality at weaning was lower for Lleyn-sired lambs compared with the other lamb genotypes (P < 0.05). These results indicate that the use of sires from larger breeds, such as Lleyn and Texel, within the Blackface ewe flocks can increase lamb output, with no apparent detrimental effects on lamb mortality or ewe survival, but increased assistance at lambing will be required.     

The effect of hypoxia on locomotor performance and behaviour during escape in Liza aurata

Escape performance was investigated in the golden grey mullet Liza aurata exposed to various levels of oxygen: >85 ( i.e. normoxia), 50, 20 and 10 % air saturation. Since the golden grey mullet performed aquatic surface respiration when air saturation approached 15–10 %, escape performance was tested at 10 % air saturation with and without access to the surface (10 % S and 10 % C, respectively). Various locomotor and behavioural variables were measured, such as cumulative distance, maximum swimming speed, acceleration, responsiveness (per cent of responding fish), response latency and directionality. Golden grey mullet showed a decrease in responsiveness when the oxygen level was reduced to 10 % air saturation, whether the surface access was obstructed or not. Hypoxia did not have any effect on the response latency. Cumulative distance and maximum swimming speed over a fixed time were significantly different between normoxic conditions and 10 % C, while no differences were found in maximum acceleration. While the fish's 'C‐bend' was mainly directed away from the stimulus in normoxia, the proportion of away and towards 'C‐bend' was random when the oxygen was ≤20 % air saturation. This suggested an impairment of the left‐right discrimination at the initiation of the fast start. Hypoxia affected golden grey mullet escape performance mainly through an impairment of responsiveness and directionality, while locomotor performance was affected only in severe hypoxia when the surface was obstructed. The study showed that, in addition to forcing the fish to the surface as shown by previous studies, hypoxia may also reduce fish elusiveness facing a predator by directly impairing its escape performance.