Effect of water restriction on productive performance and blood parameters in comisana sheep reared under intensive condition

Differentiation of Hair Sheep Breeds Based on the Physiological and Blood Biochemical Changes in Response to Different Stressors Using Multivariate Analysis Techniques

Physiological and blood measurement changes due to high heat load, restricted feed intake, and limited drinking water availability in 135 animals of three hair sheep breeds (Dorper, Katahdin, and St. Croix) were subjected to multivariate analysis techniques. The objective of this analysis was to evaluate the ability of these variables to separate individual hair sheep into groups based on adaptation characteristics in response to three physiological stressors and identify variables with greater discriminatory power. There were 16, 8, and 13 physiological and blood variables obtained from high heat load, restricted feed consumption, and water intake studies, respectively, for multivariate analysis. Physiological variables such as respiration rate, rectal and skin temperature, and panting score were measured only in the heat stress study. The results of the cluster and canonical discriminant analyses showed the presence of wide divergence (p < 0.05) between St. Croix and other breeds in their responses to high heat loads and restricted-feed- and -water-intake conditions. Dorper and Katahdin were grouped (p > 0.05) together based on the changes in physiological variables, which were separated (p < 0.05) from those of St. Croix as a resilient group. The stepwise discriminant analysis indicated that skin temperature, panting score, rectal temperature, respiration rate, and blood urea nitrogen and oxygen concentrations were the significant (p < 0.05) discriminating variables in clustering individual sheep into groups based on their responses to the high-heat-stress condition. Under the limited feed intake condition, the significant (p < 0.05) traits responsible for the separation of St. Croix from Dorper and Katahdin were blood triglyceride and cholesterol concentrations, whereas blood hemoglobin, osmolality, protein, and albumin were most important discriminating variables under the limited water intake condition. In conclusion, the results of the present study suggest that the stress responses of Dorper and Katahdin are similar and different from that of St. Croix. This finding can be useful information for future decisions in developing climate-resilient sheep through selective breeding.

Physiological, hematological, and biochemical responses in Hararghe-highland lamb subjected to water salinity levels of Lake Basaka in a semiarid area of Ethiopia

The present study aimed to evaluate the effect of drinking salinity levels in Lake water on the growth performance, and physiological, and blood constituents of Hararghe-highland lambs. A total of 28 lambs (average IBW of 18 ± 1.18kg) were categorized into four levels of water salinity, namely freshwater (510 mg/l TDS), lake Basaka water (LBW; 2600mg TDS/L); lake Basaka water plus 100% TDS of LBW; 5200mg TDS/L) and lake Basaka water plus 200% TDS of LBW; 7900mg TDS/L). The current results suggest that increased total dissolved solid levels in lake water increase the water intake of lambs while not affecting IBW, FBW, AWG, and FCR. Additionally, drinking saline lake with increasing total dissolved solid levels increased rectal temperature and respiration rate and caused a significant (P < 0.05) change in the concentrations of glucose, albumin, urea, triglycerides, sodium, AST, and ALT. Some hematological variables and biochemical constituents like creatinine, total protein, cholesterol, chlorides, potassium, magnesium, and calcium showed no significant (P > 0.05) differences. In conclusion, Hararghe-highland lambs from Ethiopia could tolerate lake Basaka water with a high salt level (7952 mg/L TDS).

Effects of Restricted Availability of Drinking Water on Blood Characteristics and Constituents in Dorper, Katahdin, and St. Croix Sheep from Different Regions of the USA

Different hair sheep breeds originated from diverse climatic regions of the USA may show varying adaptability to water deprivation. Therefore, the objective of this study was to assess the effects of restricted availability of drinking water on blood characteristics and constituent concentrations in different breeds of hair sheep from various regions the USA. For this study, 45 Dorper (initial age = 3.7 ± 0.34 yr), 45 Katahdin (3.9 ± 0.36 yr), and 44 St. Croix (2.7 ± 0.29 yr) sheep from 45 farms in 4 regions of the USA (Midwest, Northwest, Southeast, and central Texas) were used. Ad libitum water intake was determined during wk 2 of period one, with 75% of ad libitum water intake offered during wk 2 of period two, and 50% of ad libitum water intake offered for 5 wk (i.e., wk 5−9) in period three. Water was offered at 07:00 or 07:30 h, with blood samples collected at 08:00 and(or) 14:00 h in wk 1, 2, 3, 4, 8, and 9 for variables such as hemoglobin and oxygen saturation and wk 2, 4, 6, 8, and 9 for concentrations of glucose and other constituents. The blood oxygen concentration at 08:00 h was 4.86, 4.93, and 5.25 mmol/L in period one and 4.89, 4.81, and 5.74 mmol/L in period three for Dorper, Katahdin, and St. Croix, respectively (SEM = 0.160; p = 0.001). Blood oxygen at 14:00 h was 4.37, 4.61, and 4.74 mmol/L in period one and 4.66, 4.81, and 5.46 mmol/L in period three for Dorper, Katahdin, and St. Croix, respectively (SEM = 0.154; p = 0.003). St. Croix were able to maintain a higher (p < 0.001) blood oxygen concentration than Dorper and Katahdin regardless of water availability. The pattern of change in blood concentrations with advancing time varied considerably among constituents. However, concentrations of glucose (55.3 and 56.2 mg/dL; SEM = 0.84), lactate (24.1 and 22.5 mg/dL; SEM = 0.79), total protein (7.08 and 7.17 g/dL; SEM = 0.0781), and albumin (2.59 and 2.65 g/dL in wk 2 and 9, respectively; SEM = 0.029) were similar (p > 0.05) between periods one and three. Conversely, concentrations of cholesterol (56.2 and 69.3 mg/dL; SEM = 1.33) and triglycerides (28.6 and 34.5 mg/dL in wk 2 and 9, respectively; SEM = 0.98) were greater (p < 0.05) in period three vs. 1. In conclusion, water restriction altered almost all the blood variables depending upon severity and duration of restriction, but the hair sheep breeds used from different regions of the USA, especially St. Croix, displayed considerable capacity to adapt to limited drinking water availability.

Feed digestibility, digesta passage and faecal microbial biomass in desert-adapted goats exposed to mild water restriction

In arid and semi-arid environments, extensively managed ruminants regularly experience drinking water shortage, especially in the dry season. The present study therefore investigated the effects of mild drinking water restriction on feed intake, feed digestibility, solid digesta passage and composition of faeces including faecal microbial biomass. A feeding trial was conducted in Oman, during the dry summer months. Nine adult male Batinah goats were subjected to three watering regimes in a 3 × 3 Latin Square design. Treatments were (1) water offered ad libitum (100%, W100); (2) water restricted to 85% ad libitum consumption (W85); and (3) water restricted to 70% ad libitum consumption (W70). Animals were offered Rhodes grass hay and whole barley grains (1:1 ratio) at 1.3 times maintenance energy requirements. Each of the three experimental periods comprised 16 days of adaptation and 8 days of measurements. During the latter, feed offered and refused as well as faeces were sampled and quantified. Gastrointestinal digesta passage was determined using ytterbium-labelled Rhodes grass hay. Ergosterol and amino sugars were used as markers for faecal microbial biomass, that is the sum of fungi and bacteria. Water restriction had no effect on feed intake and digesta passage. However, feed dry matter, organic matter and fibre digestibility increased (p < 0.05) in W70 compared with W85, and the excreted amount of faecal dry matter, organic matter, nitrogen and neutral detergent fibre decreased (p < 0.05) in W70 compared with W85. Even though water restriction did not affect total faecal microbial biomass carbon (C) concentration, that of fungal biomass C increased (p < 0.05) in W70 compared with W85. Therefore, mild water restriction seems unproblematic from a physiological and nutrient utilization perspective as it increases feed digestibility without compromising feed intake.

Resilience to drought in semi-desert sheep: Effects of water restriction during pregnancy on placental efficiency in the Awassi breed

Assessing the resilience of Awassi sheep to water shortages during pregnancy, thereby investigating the effects of water scarcity on gestation efficiency in animals, could provide valuable and pertinent insight into future scenarios posed by climate change risks. In this study, 40 pregnant Awassi ewes randomly allocated to free watering group (C, n = 20) received water ad libitum and the water restricted group (WR) received 50% less water than the amount provided to group C. Water restriction decreased (p < .05) lambs' birth weights, placental weights (PWs), and cotyledon numbers (CNs). Placental efficiency (PE) and cotyledon efficiency (CE) were significantly higher in the WR group (p < .05). A marked difference in cotyledon weight - an increase of 12.1% - was recorded in the C group. The body weights of the pregnant ewes in the WR group decreased significantly (p < .05) by 22% during pregnancy. Significant increases (p < .05) in plasma ADH, cholesterol, Cl^- , and Na⁺ levels were observed in the WR group ewes, indicating intense dehydration. We conclude that the Awassi breed of sheep can endure 50% water restriction during pregnancy and maintain successful parturition, a key outcome for sustainability.

Effects of water restriction on feed intake, digestion, and energy utilization by mature female St. Croix sheep

Eleven St. Croix ewes (46.9 ± 1.59 kg BW and 3.6 ± 0.67 yr age) were used in a crossover design to evaluate effects of restricted drinking water availability on intake of a 50% concentrate diet, digestion, and energy utilization. After 2 wk to determine ad libitum water consumption, there were two 4-wk periods, with measures in metabolism cages during wk 4. One treatment was water offered at the ad libitum level (CONT) and the other entailed a 25% reduction in wk 1 and 50% thereafter (REST). Although, some water was refused in wk 4, with intake of 2556 and 1707 g/day for CONT and REST, respectively (SEM=170.9). Digestibility of gross energy was greater (P = 0.034) for REST than for CONT (66.5 vs. 62.4%; SEM=1.16); however, because of a numerical difference (P = 0.448) in energy intake (15.79 and 14.66 MJ/day for CONT and REST, respectively; SEM=1.426 MJ/day), digested energy intake was similar between treatments (P = 0.870). Urinary energy was greater (P = 0.023) for CONT vs. REST (0.62 and 0.52 MJ/day; SEM=0.038) and methane energy did not differ (P = 0.213) between treatments (0.76 and 0.89 MJ/day; SEM=0.084), resulting in similar (P = 0.665) ME intake (8.50 and 8.01 MJ/day for CONT and REST, respectively; SEM=0.855). Both heat (8.60 and 8.33 MJ/day; SEM=0.437) and recovered energy (-0.10 and -0.30 MJ/day for CONT and REST, respectively; SEM=0.623) were similar between treatments (P ≥ 0.880). In conclusion, increased digestibility appears an important adaptive response to limited availability of drinking water.

Effect of water scarcity during thermal-humidity exposure on the mineral footprint of sheep

OBJECTIVE

Combination of two stressors on alteration of mineral footprints in animals needs due attention to meet maximum production and welfare, particularly in grazing sheep. This study tested whether ewes (Ovis aries) exposed to water deprivation and thermal-humidity stressors had altered mineral footprints in their wool, serum, urine, and feces.

METHODS

Nine ewes (age = 3 years; mean body weight = 41±3.5 kg) were divided among a control group with free access to water, and treatment groups with water deprivation lasting either 2 h (2hWD) or 3 h (3hWD) after feeding. Using a 3×3 Latin square design, animals were assigned to treatment groups for three sampling periods of 21 days each (n = 9). Blood was collected by jugular venipuncture. Wool was collected at the end of periods 2 and 3. Metabolic crates designed with metal grated floors were used for urine and feces collection. We measured sodium (Na), magnesium (Mg), phosphorus (P), chloride (Cl), calcium (Ca), manganese (Mn), copper (Cu), iron (Fe), and zinc (Zn).

RESULTS

The wool mineral levels did not differ between the treatment groups, although K was marginally lower (p = 0.10) in the 2hWD group. The serum and urine mineral levels did not differ between the treatments (p>0.05). Fecal K was significantly lower in the 2hWD group than in the other groups (p≤0.05).

CONCLUSION

In conclusion, water deprivation and thermal-humidity exposure altered the excretion of K, but not of other minerals, in the wool, urine, feces, or serum of ewes. Thus, no additional mineral supplementation is needed for water deprived ewes during thermalhumidity exposure.

Carcass traits and meat quality of lambs fed with cactus (Opuntia fícus-indica Mill) silage and subjected to an intermittent water supply

The present study aimed to evaluate the effect of cactus silage and an intermittent water supply for lambs on carcass traits and meat quality. Thirty-six crossbreed lambs with an initial average weight of 19.8 ± 2.1 kg and average age of 6 months were randomly assigned to a 3 × 3 factorial design comprising three addition ratios of cactus silage to the diet (0, 21, and 42% based on dry matter) and three water supply intervals (0, 24, and 48 h) with four replicates. There was no interaction (P > 0.05) between the cactus silage ratio and intermittent water supply for any of the evaluated variables, with the exception of the yield of the half carcass commercial cuts. There was no significant effect of intermittent water supply (P > 0.05) on the carcass characteristics or meat quality. The addition of forage cactus silage as a substitute for Tifton hay affected the morphometric measurements (P < 0.05) and carcass compactness index (P < 0.05). The addition of 42% cactus silage to the diet increased (P < 0.05) the rib eye area (13.98 cm²). The addition of cactus silage as a substitute for Tifton hay positively affected (P < 0.05) the carcass weight of commercial cuts of the lambs. To the physical and chemical parameters of the Longissimus lumborum, the addition of 42% cactus silage to the diet reduced the color meat parameters (P < 0.05) and pH_{0 and 24h}, cooking losses, and shear force were not affected (P > 0.05). The addition of forage cactus silage to the lambs’ diet affected (P < 0.05) the composition of some saturated fatty acids in the meat. A water supply interval of up to 48 h does not influence carcass characteristics and meat quality. Therefore, the use of cactus silage can be recommended in situations of water scarcity without harming the production or meat quality of crossbreed lambs.

Effects of restricted availability of drinking water on body weight and feed intake by Dorper, Katahdin, and St. Croix sheep from different regions of the USA

Resilience to restricted availability of drinking water was evaluated with 44 Dorper (DOR; initial age = 3.7 ± 0.34 yr), 42 Katahdin (KAT; 3.9 ± 0.36 yr), and 42 St. Croix (STC; 2.7 ± 0.29 yr) sheep from 46 farms in 4 regions of the USA (Midwest, MW; Northwest, NW; Southeast, SE; central Texas, TX). Ad libitum water intake was determined during 2 wk of period 1, with 75% of this amount offered in 2 wk of period 2 and 50% in 5 wk (i.e., 5 to 9) of period 3. Body weight and DMI in week 2 of period 1 and week 9 of period 3 were analyzed with a mixed effects model. There was a breed × period interaction (P = 0.023) in water intake relative to BW (6.17, 6.69, and 7.19 in period 1 and 3.04%, 3.26%, and 3.36% BW in period 3 for DOR, KAT, and STC, respectively; SEM = 0.219). There were 3-way interactions of breed, region, and period in BW and DMI in g/d (P < 0.010). For STC, BW was greater (P < 0.05) in period 3 vs. 1 for all regions (50.1, 47.6, 42.4, and 45.8 kg in period 1 and 51.9, 49.3, 44.5, and 47.7 kg in period 3), whereas there was only a period difference for DOR from the MW and SE (61.4, 66.0, 64.6, and 59.6 kg in period 1 and 60.6, 66.5, 65.7, and 62.4 kg) and for KAT from TX (50.1, 47.6, 42.4, and 45.8 kg in period 1 and 51.9, 49.3, 44.5, and 47.7 kg in period 3 for MW, NW, SE, and TX, respectively; SEM = 2.57). In accordance, DMI by STC was similar (P > 0.05) between periods for all regions (1.25, 1.17, 1.06, and 1.16 kg/d in period 1 and 1.12, 1.08, 1.02, and 1.02 kg/d in period 3), as was also the case for DOR from MW and SE but not from NW or TX (1.54, 1.50, 1.30, and 1.41 kg/d in period 1 and 1.41, 1.13, 1.25, and 1.18 kg/d in period 3) and KAT from TX though not from the other 3 regions (1.47, 1.52, 1.48, and 1.40 kg/d in period 1 and 1.06, 1.15, 1.30, and 1.33 kg/d in period 3 for MW, NW, SE, and TX, respectively; SEM = 0.061). In conclusion, based on BW and DMI with water intake restricted at 50% of ad libitum consumption by individual animals, STC appeared more consistent in display of high resilience to restricted water availability, although DOR from 2 regions and KAT from 1 also were relatively resilient. The results suggest benefit to breed comparisons of inclusion of animals from multiple areas and that environmental conditions of regions may have disparate effects with different breeds of hair sheep.

Small Ruminants: Farmers' Hope in a World Threatened by Water Scarcity

Simple Summary

Water is one of the most important nutrients to livestock. It is so essential that more than half the volume of the animal's body is water. However, its availability is threatened by the irreversible changes in climate, which has culminated into reduced rainfall in most regions of the world. Such an increasing threat to regular water supply, and by extension to food security and livelihood has forced a shift from large to small ruminant production, especially in regions experiencing low rainfall, with farmers taking advantage of their adaptive process and efficiency of water use. Small ruminants, especially desert goats, can adaptively survive in water-limited areas while trekking long distance in search of feed and they will regain any weight loss at the next watering point. Further research is needed on adaptive indigenous breeds of small ruminants since tolerance to water scarcity is breed dependent, so that improvements can be made through effective selection and breeding program.

Abstract

The availability and sustainability of suitable and good quality drinking water is a global concern. Such uncertainties threaten livestock production with an attendant ripple effect on food security. Small ruminants, including sheep and goats, appear to be promising to smallholder farmers in solving this problem because of their ability to survive in water-limited areas and harsh environment when compared with large ruminants. Their small body size is also seen as an advantage, because less water will be required for proper digestion and feed utilization. Therefore, this review will provide information regarding the adaptive responses of small ruminants on thermoregulation, blood metabolites, immune status, drug pharmacokinetics, reproduction and hormonal indices during the period of water stress. Adaptable and indigenous breeds are known to be more tolerant to water stress than selected breeds. A drop in feed intake and weight reduced respiratory rate and increased concentration of blood metabolites are the general effects and/or observations that are encountered by small ruminants during the period of water stress. The concept of water tolerance either as deprivation and/or restriction of indigenous and adaptable breeds of small ruminants is gaining ground in research studies around the world. However, more research, however, seeking to explore water tolerance capacity of adaptable breeds especially in arid and water limiting areas are still needed.

Body Temperature Responses and Hair Cortisol Levels in Dairy Holstein Cows Fed High- and Low-Forage Diet and Under Water Deprivation During Thermal-Humidity Exposure

Body temperature responses and hair cortisol levels in dairy Holstein cows fed high- and low-forage diet and under water deprivation during thermal-humidity exposure (THE) were evaluated. Two experiments (Exps.) were conducted between July and September 2012 and 2013 for 64 d and 74 d, respectively. First, twenty dairy Holstein cows (90±30 DIM; 37.2±1.7 l milk/d, 620±75 kg BW) were used. The practical forage:concentrate (F:C) ratios in the low forage (LF) and high forage (HF) group were 44:56 and 56:44, respectively, while they were designed to be 40:60 and 60:40. Second, thirty dairy cows (53.5±30.4 DIM; 41.7±1.5 l milk/d,650±53 kg BW) were allotted into two groups of free access to water (FAW) and 2 h water deprivation (2hWD) following feeding. The animals were subjected to having the hair cut (1 to 2 g) from their foreheads at the same time (12:00 h) twice at the beginning (prior to the beginning of heat stress) and the end of the experiment when the cows were under THE. Hair cortisol levels (initial hair cut as the baseline and re-grown hair) were measured using ELISA method. Body temperature (BT) was measured twice daily at 7 body points of cows including rectum, vagina, hip, udder, rumen-side (flank), ear, and forehead using non-contact forehead infrared thermometer (infrared gun having two modes: inner and skin) on the 7 d of the beginning and the last 7 d of the experiment at 1000 and 1400 h. Statistical analyses were carried out using the MIXED model of SAS as repeated measurements. The intra-assay and inter-assay coefficients of variations for hair cortisol measurements were 3.15 and 10.05, respectively. Hair cortisol (HC) levels were not different within the two groups in both Exps. (P>0.05); however, HC level was lower (P<0.0001) prior to temperature-humidity exposure (THE). Results of Exp. 1 showed that vagina inner temperature was higher (P=0.041) and rectal temperature tended to be higher (P=0.083) in the HF compared to the LF group. The inner ear temperature was lower and ear skin temperature was higher (P=0.032) in the HF compared to the LF group. Forehead inner temperature was higher (P=0.048) in the LF group than in the HF group while forehead skin temperature was lower in the HF group (P=0.041). No differences were observed in the hip, udder and rumen-side (flank) temperature (both in body and skin) between the HF and LF group (P=0.012). In Exp. 2, no temperature differences were observed at all of the body points, inner and skin, between the two groups (P>0.05). However, the skin temperature in the 2hWD groups tended to be higher than in the FAW group (P=0.093). Conclusions drawn indicate the beneficial use of measuring BT at different body points of the cow in addition to RT under THE.

The effect of water restriction on physiological and blood parameters in lactating dairy cows reared under Mediterranean climate

OBJECTIVE

This study was conducted to evaluate the effect of water restriction (WR) on physiological and blood parameters in lactating dairy cows reared under Mediterranean climate.

METHODS

The trial lasted 16 days preceded by two weeks of adaptation to the experimental condition in spring 2014 on 6 dairy cows in mid-lactation. These cows were allowed water ad libitum for 4 days (W100) (hydration period), then split into 2 groups, one group has received 25% and the other 50% of water compared to their mean water consumption during the hydration period; then rehydrated for 4 days. Feed intake and physiological parameters: respiratory rate (RR), heart rate (HR), and rectal temperature (RT) were recorded twice a day. Blood was collected once a day and analyzed for serum concentration of glucose (Glc), triglycerides (TG), cholesterol (Chol), urea (Ur), creatinine (Crea), and total protein (TP) by enzymatic colorimetric method and cortisol (Cort) by radioimmunoassay.

RESULTS

Total dry matter intake (TDMI) was affected by WR. A decrease in TDMI was observed in WR groups compared to W100 group (effect, group, period, day, group×day, period× day: p<0.001). Also, WR resulted in a significant increase in RR, HR, RT in WR groups than in W100 group (effect, group: p<0.001). In addition, an increase in the serum concentration of Glc, TG, Chol, Ur, Crea, TP, and Cort was noted in WR groups (effect, group, period, day: p<0.001).

CONCLUSION

This study has shown the ability of cows raised in a Mediterranean climate to cope with different levels of WR and thus reach a new equilibrium. As result, elucidates the important role of water as a limiting factor for livestock in environments with low water availability.

An assessment of sire-breed effects on carcass and meat quality traits of lambs at the ages of 40 and 100 days from Comisana ewes crossed with Suffolk or Bergamasca rams

The aim was to compare lambs at two different ages at slaughter (40 vs 100 days) and three breeds or crossbreeds including an Italian dairy breed (Comisana (Com)) and its crosses with the two meat breeds of Bergamasca (Ber × Com) and Suffolk (Suf × Com) with 20 male lambs per age per breed group. At both slaughter ages, crossbreeds were more productive, with higher liveweight (P = 0.02), carcass weight (P = 0.03) and dressing percentage (P = 0.04) than the Com group. Meat from the younger lambs showed lower C10:0, C14:0 and C22:0 (P < 0.05) and higher C18:1 (P < 0.01) concentrations, resulting in higher monounsaturated fatty acid (P < 0.01) and lower saturated fatty acid (P < 0.01) content. Moreover, their meat has lower redness (a*), yellowness (b*) and chroma (C*) values (P < 0.01). Crossbreeding dairy breed ewes with sires of high meat production breeds improves liveweight and carcass weight. Meat from younger lambs had lower intramuscular fat content and higher concentrations of polyunsaturated fatty acid.

Effect of water restriction on milk yield and quality in Lacaune breed ewes

The effect of water restriction on body weight, body condition score, milk yield, and milk composition and rheological characteristics in intensively reared Lacaune ewes was evaluated. After 7 days of adaptation, the trial lasted 28 days. Thirty lactating ewes (48 ± 5 months of age; mean value ± standard deviation) at the beginning of third lactation month were divided into three groups (n = 10), corresponding to the following water restriction treatment: a group control received no drinking water restriction (W100), and two groups received water to the extent of 80% and 60% of W100 daily consumption (W80 and W60 group respectively). The effects of water restriction were assessed at the beginning of experiment (D0), at D14 and D28. The W60 group resulted in a significant decrease in body weight, body condition score, milk yield and feed consumption of hay due to the experimental treatment; whereas a marked increase in both W60 and W80 groups of milk lactose, urea, sodium, sodium chloride content and titratable acidity was observed. Rheological parameters of milk, rennet coagulation time and curd-firming time were positively affected by water restriction treatments, with a decrease in both experimental groups of the time required for the formation of a stable and firm curd. Results highlight the importance of water consumption in dairy sheep. The scarce availability of water, significantly affecting ewes milk production, is worthy of particular attention in arid area where water stress-resistant breeds should be considered. This study underlines that milk yield, being closely linked to the availability of water of the breeding habitat due to its high water content (about 81%), could be reached in area where water is not a limiting factor without reducing the genetic expression of the animals. Less severe water restrictions, such as 20% of daily voluntary water intake, produce no detrimental effect on milk yield.

Evidence of dehydration and electrolyte disturbances in cases of perennial ryegrass toxicosis in Australian sheep

CASE REPORT

Perennial ryegrass toxicosis (PRGT) is a common disease entity in Australia, presenting as an association of clinical signs including alterations in normal behavioural, ataxia ('staggers'), ill thrift and gastrointestinal dysfunction ('scours'). Clinical signs can range in severity from mild (gait abnormalities and failure to thrive) to severe (seizures, lateral recumbency and death). Presentation across the flock is usually highly variable. PRGT is caused by toxins produced by the endophytic fungus Neotyphodium lolii, a symbiont of perennial ryegrass that is present in pastures across the temperate regions of Australia and Tasmania. A particular feature of PRGT in Australia is the occasional occurrence of large-scale sheep losses, suggesting other factors are influencing mortality rates compared with other PRGT risk zones such as North America and New Zealand. During 2011, producers in the state of Victoria experienced a mild outbreak of PRGT that affected large numbers of animals but with limited mortalities. Clinical samples taken from affected sheep showed a high incidence of dehydration and electrolyte abnormalities.

CONCLUSION

We speculate that changes in hydration status may be a contributory aetiological factor in those years in which high numbers of deaths are associated with PRGT outbreaks in Australia.

Relative bioavailability of soil-bound chlordecone in growing lambs

The pollution of soil with the pesticide chlordecone (CLD) is a problem for the use of agricultural surfaces even years after its use has been forbidden. Therefore, the exposure of free-ranged animals such as ruminants needs to be investigated in order to assess the risk of contamination of the food chain. Indeed, measured concentrations could be integrated in a lowered extent if the soil binding would reduce the bioavailability of the pesticide. This bioavailability of soil-bound CLD in a heavily polluted andosol has been investigated relatively of CLD given via spiked oil. Twenty-four weaned lambs were exposed to graded doses of 2, 4 or 6 μg CLD/kg body weight during 15 days via the contaminated soil in comparison to spiked oil. The concentration of this pesticide has been determined in two target tissues: blood serum and kidney fat. The relative bioavailability (RBA) corresponds to the slope ratio between the test matrix-contaminated soil- in comparison to the reference matrix oil. The RBA of the soil-bound CLD was not found to significantly differ from the reference matrix oil in lambs meaning that the pesticide ingested by grazing ruminants would not be sequestered by soil binding. Therefore, CLD from soil gets bioavailable within the intestinal level and exposure to contaminated soil has to be integrated in risk assessments.

Review: Water stress in sheep raised under arid conditions

Chedid, M., Jaber, L. S., Giger-Reverdin, S., Duvaux-Ponter, C. and Hamadeh, S. K. 2014. Review: Water stress in sheep raised under arid conditions. Can. J. Anim. Sci. 94: 243–257. Sheep breeds which are indigenous to arid and semi-arid regions are known for their ability to adapt to rustic environments, to climatic variations as well as to shortages in resources. Water scarcity, often combined with heat stress, is a common challenge facing these animals, causing physiological perturbations and affecting the animal's productivity. This review reports the effect of different forms of water stress on physiological indicators, blood parameters, thermoregulation and immunological status in sheep. Although the breed effect may be significant, the following are generally observed common responses: drop in feed intake and weight loss, increase in evaporative cooling through panting, production of a small volume of highly concentrated urine, haemoconcentration, high blood osmolality, and immunosuppression. Prolonged water shortage may affect lamb birth weight and survival, and lead to a decrease in milk production, especially in non-adapted breeds, which could lead to important economic losses, as reported in heat-stressed sheep husbandries. Novel stress alleviation approaches are also presented, such as vitamin C supplementation.