Sparse Pasture Research Articles

The adaptive strategies of yaks to live in the Asian highlands.

The yak (Bos grunniens), an indigenous herbivore raised at altitudes between 3,000 and 5,000 m above sea level, is closely linked to more than 40 ethnic communities and plays a vital role in the ecological stability, livelihood security, socio-economic development, and ethnic cultural traditions in the Asian highlands. They provide the highlanders with meat, milk, fibres, leather and dung (fuel). They are also used as pack animals to transport goods, for travel and ploughing, and are important in many religious and traditional ceremonies. The Asian highlands are known for an extremely, harsh environment, namely low air temperature and oxygen content and high ultraviolet light and winds. Pasture availability fluctuates greatly, with sparse pasture of poor quality over the long seven-month cold winter. After long-term natural and artificial selections, yaks have adapted excellently to the harsh conditions: 1) by genomics, with positively selected genes involved in hypoxia response and energy metabolism; 2) anatomically, including a short tongue with a weak sense of taste, and large lung and heart; 3) physiologically, by insensitivity to hypoxic pulmonary vasoconstriction, maintaining foetal haemoglobin throughout life, and low heart rate and heat production in the cold season; 4) behaviourlly, by efficient grazing and selecting forbs with high nutritional contents; 5) by low nitrogen and energy requirements for maintenance and low methane emission and nitrogen excretion, namely, ‘Low-Carbon’ and ‘Nitrogen-Saving’ traits; 6) by harboring unique rumen microbiota with a distinct maturation pattern, that has co-evolved with host metabolism. This review aims to provide an overview of the comprehensive adaptive strategies of the yak to the severe conditions of the highlands. A better understanding of these strategies that yaks employ to adapt to the harsh environment could be used in improving their production, breeding and management, and gaining benefits in ecosystem service and a more resilient livelihood to climate change in the Asian highlands.

Effect of air temperature on growth performance, apparent digestibilities, rumen fermentation and serum metabolites in Altay and Hu lambs.

Fat-tailed Altay sheep are indigenous to the Altay prefecture and well adapted to severe cold and sparse pasture of poor quality. Hu sheep were introduced to this region in the 1970s and are raised mainly in feedlots. We hypothesized that the dietary energy utilization would differ between breeds and predicted that Altay sheep would be more efficient than Hu sheep, in particular at a low air temperature. To test this prediction, we examined growth performance, apparent digestibilities, rumen fermentation and serum metabolites in Altay (32±2.6kg) and Hu sheep (31±2.7kg) at air temperatures of -5 and 20°C. Average daily gain (ADG), feed and metabolizable energy intakes were greater in Altay than in Hu sheep (p<.01), and all were greater at -5°C than 20°C (p<.01). Body mass gain-to-feed intake ratio was higher in Altay than in Hu sheep (p<.001), but was not affected by air temperature (p>.10). Rumen total volatile fatty acid (VFA) concentration was greater in Hu than in Altay sheep (p<.05) and was greater at 20°C than at -5°C (p<.05), while rumen microbial protein concentration was greater in Altay than in Hu sheep (p<.05). Rectal temperature was higher at -5°C than 20°C (p<.05) and was similar between breeds (p>.05). Serum glucose, non-esterified fatty acid (NEFA) and urea-N concentrations were higher in Hu than in Altay sheep (p<.05). It was concluded that Altay sheep are better able to cope with poor quality diets as they had higher digestibility of nutrients, ADG and body mass gain-to-feed intake ratio than Hu sheep.

Predicting pasture and sheep production in the Victorian Mallee with the decision support tool, GrassGro

The GrassGro decision support tool was designed to quantify sheep and pasture production in response to management and climate variability in temperate Australia, and has been tested in temperate but not low-rainfall Australian conditions. Data from field experiments and from on-farm monitoring was used to test GrassGro predictions of annual and perennial pasture production, and sheep production at 4 locations throughout the Victorian Mallee, which is a low-rainfall area (275–375 mm annually). Predictions of long-term pasture production were then made. Predictions of the herbage biomass of annual pastures closely matched observed data for both a sandy loam (1991–2002 data) and a whole paddock (combining sandy loam and loam and sand) (2001–2002 data) soil type, at several locations across the Victorian Mallee. Linear regression between observed and simulated (April to September) data produced coefficients, significance and root mean square error of r2 = 0.81, P&lt;0.001, 217 kg DM/ha, respectively, for sandy loam soil types and r2 = 0.94, P&lt;0.001, 72 kg DM/ha, respectively, for whole paddock soil types. A series of simulations for individual years from 1970 to 2002 quantified the large impact of climate variability and demonstrated that seedbank and location, but not soil fertility, had a large influence on annual pasture production. However, GrassGro underestimated the production of the perennial pasture, lucerne (r2 = 0.2). GrassGro was also unable to adequately predict sheep production because it failed to take into account the sparse, clumpy structure of the low biomass pastures typical of this region. Methods to improve GrassGro were identified and included: (i) the need to adjust sheep intake from low biomass, sparse pastures, (ii) the ability to predict summer growing and autumn growing plant species, (iii) the ability to graze crop stubbles and (iv) refinements to the coefficients of equations used to model lucerne growth.

Oviposition site selection and effect of meteorological conditions on flight of Eudonia sabulosella (Lepidoptera: Scopariinae) with implications for pasture damage

Eudonia sabulosella (Walker) is economically the most important hill country sod webworm in New Zealand. Female moths selected long, sparse pasture cover for oviposition. Adult flight patt...

Factors affecting diet selection by sheep. 2. Height and density of pasture

Boards of artificial pasture were prepared by threading the top two leaves of tillers from either ryegrass or kikuyu grass, in their vegetative stage of growth, through 5-mm-diameter holes in pressed hardwood sheets. The holes were spaced in rows from 10 to 50 mm apart, and, with one, two or three tillers per hole, tiller density ranged from 346 to 25 980/m2. Sward height was varied by pulling tillers different distances through the holes before they were fastened to the underside of the boards, and the mass of herbage dry matter ranged from 0.04 to 7.61 t/ha. In series I experiments, the effects of sward characteristics on ingestive behaviour of two sheep were examined, whereas, in series I1 experiments, pastures that were consumed at different rates were offered in pairs and the preference of one sheep observed. The rate of pasture intake was related to sward height only when tiller density was constant and to herbage mass per unit volume (bulk density) only at similar sward heights. Intake rate was better described by herbage mass per unit area but, at herbage availabilities of less than 1 t/ha, intake rate was several-fold greater when sheep grazed tall, sparse pastures than short, dense pastures. The best predictor of pasture intake rate was herbage mass per area effectively covered by one bite. Intake per prehending bite declined with a reduction in both sward height and density, and was also best described by herbage mass per area effectively covered by one bite. Prehending bite rate doubled as intake per bite declined from 200 to 10 mg dry matter. The rate of jaw movements during grazing was virtually unaffected by sward characteristics; prehending bites accounted for 20% of jaw movements when intake per bite was 200 mg dry matter and 80% of jaw movements with short, widely spaced swards. When two pastures with different sward characteristics were offered together, sheep generally preferred the one they could eat faster.

Effects of pasture availability and liveweight on the feeding of grass hay to grazing sheep

In the first of two experiments the amount of hay (69% organic matter digestibility) eaten by 1.5 -year-old Corriedale wethers when fed every 2 d was measured in a series of grazing trials to study the effects of pasture availability and liveweight. The greatest amount of hay (1 .8 kg/head. 2 d) was eaten on dry summer pasture, but consumption fell when green growth appeared. During winter, on slow growing pastures, hay consumption (1.3 kg/head .2 d) was highest at about 0.7 t herbage (DM)/ha, but less hay was consumed on plots with lower amounts of pasture. On pasture more abundant than 0.7 t DM/ha hay intake decreased, but small amounts were still eaten at very high yields (about 5 . 0 t DM/ha). Pooled data of all winter observations yielded the following expression for predicting the organic matter intake of hay voluntarily eaten when fed every 2 d (y, g/2 d) from the quantity of pasture available (x, t DM/ha): Y = 330 + 738exp (- 0.0322x4) : r2 = 0.87 ; P &lt; 0.01 Various weather conditions experienced in different periods of one trial changed the responses slightly. Wet or frosty weather reduced hay consumption on sparse pasture relative to that on fine days. Heavy animals (49-57 kg) ate more hay (450 vs 170 g/d) at high availabilities than light animals (44 kg) and spent less time grazing than light animals (5 vs 7 h) indicating a preference by lighter animals for a high quality diet from pasture. In the second experiment, daily consumption of hay (61 % organic matter digestibility) and pasture were estimated at a range of pasture availabilities (0.5- 1.5 t DM/ha). When hay was fed, each 100 kg increment in pasture dry matter availability decreased the voluntary organic matter intake of hay by 57 g/d, while apparent consumption of pasture organic matter increased by 92 g/d. Grazing time was not reduced as much as expected from the substitution of hay for pasture, from 10 h with no hay to 9 h when fed, and suggests a slow rate of pasture intake with selection of higher quality material to complement the hay diet. A practical implication of these results is that heavy animals in good condition will eat hay in preference to grazing pasture, while lighter animals which are assumed to have a greater need for supplement prefer to consume the higher quality pasture.

Separation of ewes from twin lambs: Incidence in several sheep breeds

The ability of ewes and their lambs to keep together during the first day or two of life, when the mother—offspring bond is consolidating, was examined in fine-wool Merino, Dorset Horn and Crossbred (Border Leicester × Merino ewes mated to a Suffolk ram) sheep, lambing on a sparse pasture in the Armidale district of N.S.W., and in a Romney flock, lambing on good pasture in the Mangakino district of New Zealand. Ewes in the N.Z. flock had been selected for their ability to rear more than one lamb. 46% of the twin-bearing Merinos became permanently separated from a lamb, mostly on the day after giving birth, and in at least 54% of these cases these was no obvious precipitating factor such as birth difficulties or interference by other sheep. In addition, a further 34% of twin-bearing Merinos experienced temporary separation from one lamb. By contrast, in the other flocks, permanent separations were 17, 0 and 8%, respectively, and some precipitating factor could always be identified. Few separations were associated with human interference. The sheep at Armidale moved from the birth-site much more rapidly than the Romneys (means of 2 h versus 6.5 h), possibly due to sparse pasture conditions. In the Merinos, the proportion of separations decreased as the time that ewes remained near the birth-site increased. The observations indicate that fine-wool Merino ewes are slow to recognize the size of their litters and inherently poor at maintaining contact with more than one lamb in the neonatal period.

With the Peace Corps, Half a World Away

Baghlan Province, Afghanistan, where I work as a Peace Corps nurse, lies north of the Hindu Kush Mountains, which bisect the country. It is an area of dust and sparse pasture lands; only the Kunduz River valley is green from the extensive irrigation system radiating through it. The village houses crouch against the hillsides, for every plot of arable land is precious. Although this is a predominantly agricultural community, food as well as fuel and water are scarce.

Effect of body condition on the intake of food by mature sheep

Mature Merino wethers were changed in liveweight by grazing treatments or by feeding in pens and their intake of food over the next 5 weeks was then measured at two levels of pasture availability or in pens. Of nine groups of six sheep with mean initial fleece-free liveweight of 33 kg, three groups were increased to 37 kg (389 MJ energy) in 6 weeks by grazing abundant pasture, another three were reduced to 28 kg (220 MJ) on sparse pasture, and those remaining were reduced to 30 kg (268 MJ) by restricted feeding in pens. The three groups from each treatment were then moved to abundant pasture, to sparse pasture or to pens where food was offered ad lib. Energy status, within the range imposed here, had no effect on the intake of pasture or on the time spent grazing; both of these variables depended solely on the herbage currently available. Nor did energy status affect food intake when sheep were removed from pasture and compared in pens with a standard food. Sheep moved from sparse pasture to abundant pasture gained at least as much liveweight, but only 20% as much energy as sheep in better condition because more of their gain was water. These results suggest that short-term changes in the body condition of mature grazing sheep will have no effect on their intake of food and that their subsequent changes in fasted liveweight may give a misleading impression of changes in energy status.

Maintenance energy requirement of grazing sheep in relation to herbage availability. II.* Observations on grazing intake

Grazing pressure on three pastures was adjusted so that the mean liveweights (W) of three groups of 10 Merino wethers, initially uniform, were kept at nominally 45, 35, and 25 kg (groups H, M, and L respectively). Grazing intakes of each sheep were estimated over eight 7-day periods during 6 months. The organic matter (OM) content of the faeces decreased to less than 40% with dccreasing W, but concentrations of nitrogen (FN) and chromium sesquioxide (Cr2O3) in the OM increased. Sheep in groups M and L re-ingested with herbage, Cr2O3 they had previously excreted on their pastures. Faecal Cr2O3 concentrations were adjusted for this recycling, which otherwise would have resulted in underestimation of faecal OM outputs by up to 10% (group M) or 15% (group L). The digestibility in vitro was determined of herbage grazed from each pasture by a sheep with an oesophageal fistula. The values obtained for group H showed some differences, but not in a consistent manner, from those predicted from FN. For groups M and L, the in vitro digestibility values were consistently lower than those predicted from FN, on average by 12.5 percentage units with a maximum discrepancy of 18.5 units. It is shown that when sheep graze sparse pastures, as did groups M and L, the ingestion of large amounts of soil can lead to biased estimates of digestibility from FN, resulting in gross overestimation of digestible OM intakes. It is suggested that this bias may account for the apparently high maintenance feed intakes reported by other workers for sheep in these conditions, and that the calorimetric studies made on groups H, M, and L reported earlier gave more reliable estimates of maintenance requirements. ___________________ *Part I, Aust. J. Agric. Res., 23: 57 (1972)

The determinants of herbage intake by grazing sheep: The interrelationship of factors influencing herbage intake and availability

The interrelationship of characters of the pasture (herbage yield, height of sward) and of the animal (size of animal, rate of intake, rate of biting, size of bite, and time spent grazing) which influence the consumption of herbage by the grazing sheep was examined in three short-term experiments. In one study the high correlation usually observed between herbage yield per unit of land area and plant height was disturbed by manipulating the spatial relations of the sward; it was observed that the rate of intake of pasture by grazing animals was closely associated with plant height (estimated from tiller length) there being little relation between herbage yield and intake. Size of bite increased almost linearly with changing tiller length, whereas after a small initial increase the rate of biting decreased. These differences produced a sevenfold change in the rate of herbage consumption between sheep grazing pastures of 3.7 cm tiller length (1.0 g dry matter/min) and 7.7 cm (7.1 g/min). At greater tiller lengths the size of bite and rate of biting varied inversely to maintain a constant rate of intake. When accessibility of herbage imposed limitations on the rate at which the animal was able to prehend its feed, it was shown that the sheep was able partially to compensate for the reduced amount of herbage present by an increase in grazing time (from 6 to 13 hr/day). However, as the animal extended its period of grazing the compensation became progressively more incomplete. Under sparse pasture conditions lambs were able to consume feed at a significantly greater rate than yearlings but as pasture availability increased the situation was reversed. The role of short-term grazing studies in relation to problems of grazing management is discussed.