Efficiency Of Wool Growth Research Articles

Increasing dietary sodium chloride increases wool growth but decreases in vivo organic matter digestibility in sheep across a range of diets

For 8 weeks, 64 Merino wethers, 18 months of age, were individually penned and offered 1 of 16 treatment feeds (n = 4). The 16 feeds were formulated to contain levels of added sodium chloride (0, 7, 14, 21%) and levels of organic matter digestibility (55, 62, 69, 76%), in a 4 × 4 factorial design. The treatment feeds were offered ad libitum for 7 weeks and at maintenance for the final week. Clean wool growth, corrected for digestible organic matter intake, increased by 16, 18 and 27% as added sodium chloride was increased (7, 14, and 21%). The increase in wool growth was similar for diets at all levels of formulated organic matter digestibility. Feed digestibility in sheep decreased when added dietary sodium chloride was 14% or higher. The decrease in organic matter digestibility was ~5 percentage units at the highest level (21%) of dietary sodium chloride. Liveweight gain in sheep was reduced from 143 to 134, 65 and 1 g/day with 7, 14 and 21% added dietary sodium chloride, respectively. Therefore, improvement in wool growth efficiency appears to occur at the expense of liveweight gain, and was probably related to a shift in digestion of feed from the stomach to the small intestine. Higher corrected clean wool growth associated with lower levels of purine derivatives (an indicator of microbial protein synthesis) supported the conclusion that increased dietary salt resulted in an increase in dietary protein being digested in the small intestine. A shift in feed utilisation towards increased wool growth as dietary salt increases may be a management tool of particular interest to specialist wool producers. In areas of saline land where salt-accumulating shrubs are often the most productive vegetation, an increase in wool production efficiency, even if liveweight is only maintained, may improve the profitability of incorporating these shrubs into a feeding strategy.

Feed intake and production in sheep fed diets high in sodium and potassium

Salinity is a problem facing many crop and livestock producers in southern Australia. One management option is to revegetate with salt-tolerant plants suitable for animal production. These plants are often halophytic shrubs containing up to 30% ash, predominantly as sodium, potassium, or chloride. This experiment examines the consequences of a high intake of sodium and potassium separately or together on feed intake, digestibility, liveweight change, and wool growth. Twelve groups of 6 weaner wethers were allocated to treatments according to a balanced 3 × 4 factorial design with 3 levels of added potassium (0, 0.38, and 0.77 mol/kg DM equivalent to 0, 15, and 30 g/kg DM) and 4 levels of added sodium (0, 0.87, 2.18, and 3.48 mol/kg DM, equivalent to 0, 20, 50, and 80 g/kg DM) as the chloride salts. The treatment diets were fed to sheep for 6 weeks. Increasing sodium in the diet significantly decreased feed intake, digestibility, liveweight gain, and wool growth either as a main effect or through an interaction with potassium. Organic matter intake was reduced from 1.35 kg at the lowest levels of sodium and potassium to 0.67 kg at the highest levels. Comparing the same 2 groups, liveweight gain was reduced from 144 to 0 g/day, organic matter digestibility from 59.1% to 57.3%, and wool growth from 1.21 to 1.04 mg/cm2.day. The response surfaces indicate that production was depressed even at the lower levels of sodium, whereas high potassium depressed intake, digestibility, and liveweight gain at high levels of sodium only. The interaction between sodium and potassium was always negative at high levels of sodium, indicating that manipulation of the proportions of the 2 elements is unlikely to provide benefits for animal production when total salt levels are high. Although wool growth was depressed at high sodium and potassium, the efficiency of wool growth increased from 10.0 to 15.4 g/kg organic matter intake when the lowest and highest levels of the sodium and potassium were compared. This result may present significant opportunities for the use of saline land to grow fine wool.

Pasture intake and digestibility by young and non-breeding adult sheep: the extent of genetic variation and relationships with productivity

The objectives of this study were to estimate the genetic variation in pasture intake and digestibility of the selected diet by young and by adult sheep, and to determine the genetic relationships between pasture intake and productivity traits. The pasture intakes of groups of young and adult sheep, each containing sheep from 11 bloodlines, were measured using the paired alkane technique. The wool grown, and its fibre diameter, over the intake measurement period were also estimated, as were liveweight and fat depth. Differences in pasture intake between bloodlines were largely related to liveweight in both groups of sheep, and were repeatable ( t=0.8) between the groups. The repeatability of wool growth and wool growth efficiency was a little higher ( t>0.9). Combining all the known estimates improved the precision of the genetic parameter estimates. The pooled estimates of heritability of DOMI, wool growth, wool growth efficiency and fibre diameter were 0.12±0.04, 0.37±0.05, 0.25±0.05 and 0.66±0.08, respectively. The genetic relationships of wool growth efficiency with wool growth and fibre diameter were 0.84±0.20 and −0.03±0.12, respectively, while those for feed intake (as DOMI) with wool growth and fibre diameter were −0.02±0.17 and 0.40±0.15.

Increased efficiency of wool growth and live weight gain in Merino sheep fed transgenic lupin seed containing sunflower albumin

Increased efficiency of wool growth and live weight gain in Merino sheep fed transgenic lupin seed containing sunflower albumin

Increased efficiency of wool growth and live weight gain in Merino sheep fed transgenic lupin seed containing sunflower albumin

The aim of this experiment was to assess, using sheep, the nutritive value of lupin seed transgenically modified to contain sunflower seed albumin. Eighty Merino wether sheep of mean live weight 32.3 kg were divided into two groups and fed 796 g dry matter (DM) day−1 of a cereal hay-based diet containing 350 g kg−1 of either the transgenic or parent (unmodified) lupin seed for 6 weeks. Measurements were made of wool growth and live weight gain. After 6 weeks, half the sheep in each group were selected for a urine and faeces balance study in which organic matter (OM), nitrogen (N) and urinary purine metabolites were measured. Blood samples were taken from all sheep at the beginning and end of treatment and analysed for amino acids and plasma metabolites. A comprehensive chemical analysis of the grains showed that there was little difference between them in terms of most nutritional components, but the transgenic lupin seed contained a 2.3-fold higher methionine concentration and 1.3-fold higher cysteine than did the parent. There were no significant differences between grains in OM digestibility, rumen microbial protein synthesis or in sacco degradability of dry matter. Sheep fed the transgenic lupin grain had an 8% higher rate of wool growth (P 0.1). Plasma urea N was lower in the sheep fed the transgenic grain than those fed the parent grain (6.5 vs 6.8 mmol l−1, P < 0.05). The results show that genetic modification of a feed grain can improve its nutritive value for ruminants. The size and nature of the responses were consistent with the transgenic lupins providing more methionine to the tissues, a first-limiting amino acid for sheep. © 2000 Society of Chemical Industry

Variation between Merino ewes in pasture intake 2. Within-flock genetic parameters for intake and some production traits

Abstract Genetic parameters were estimated for pasture feed intake, liveweight, ultrasonic fat depth, clean wool growth and clean wool growth efficiency of approx. 300 grazing adult Merino ewes in each of 2 years, over four seasons representing different stages of the annual reproductive cycle. Measurements were made on a total of 515 individual ewes (with 87 measured in both years), the progeny of 126 sires. The genetic parameters were estimated using a sire model REML analysis. Digestible organic matter intake (DOMI) had a heritability of 0.12 ± 0.07, pooled across seasons. Adjusting for liveweight did not affect the pooled heritability estimate. The pooled heritability estimates for liveweight, fat depth, clean wool growth and wool growth efficiency were 0.67, 0.47, 0.41 and 0.21, respectively. Clean wool growth, liveweight and fat depth had moderate to strong positive genetic correlations with DOMI in all seasons except spring (mid-lactation). Wool growth rate and wool growth efficiency had a strong positive genetic association (0.77 ± 0.34, pooled across seasons), as did liveweight and fat depth (0.54 ± 0.14). It was concluded that selection for wool growth will result in genetic improvement in efficiency and some increase in intake. Optimising responses in efficiency will require more precise estimates of genetic parameters.

Consequences of reproduction on the liveweight, fat depth, wool growth, and intake of grazing Merino ewes in the short and long term

Effects of the current and previous year's reproductive performance on liveweight, fat depth, pasture intake, and wool growth were estimated in breeding Merino ewes in each of 2 years and in 4 seasons corresponding with stages of the annual reproductive cycle. Ewes bearing multiple lambs were heavier in early pregnancy (autumn, by 1.5 kg) and in late pregnancy (winter, by 2.5 kg) than single-bearing ewes, with both being heavier than nonpregnant (dry) ewes in winter (by 1.7-4.2 kg). Pregnancy had no effect on fat depth or intake in autumn or winter. Lactating ewes were leaner (by 1.0-1.7 mm), had lower liveweights (by 6.4-8.6 kg), and had substantially higher intakes [by 286-348 g digestible organic matter intake (DOMI)/day] than non-lactating ewes. From summer to winter, ewes that had previously reared a lamb, or lambs, to weaning weighed less, were leaner, and had higher intakes than ewes that were previously dry. Pregnant ewes grew significantly less clean wool and grew it less efficiently (g wool/kg DOMI) in autumn (7-9% less) and winter (11-18% less) than non-pregnant ewes. Similarly, lactating ewes grew less wool (by 23-30%) less efficiently than ewes not suckling, the effect being greater in ewes with multiple lambs. Post-weaning, however, ewes that had reared a lamb to weaning grew significantly more wool (by 6-15%) up to 4 months post-weaning, although efficiency of wool growth was still impaired. The effects of reproductive status on the fibre diameter of wool reflected those for wool growth. Effects of reproduction on productivity are long term and recovery may not be achieved before the next reproductive cycle.

The effect of trenbolone acetate and trenbolone acetate plus oestradiol-17β on wool growth

There is currently considerable interest in the use of anabolic compounds to improve the efficiency of animal growth and to produce leaner carcasses. While the majority of work has centred on beef production, the growth performance of sheep is also improved (Galbraith &amp; Topps, 1981). However, little is known of the effects of anabolic steroid hormone administration on wool growth. The few experiments which have been conducted indicate that exogenous oestrogens depress wool output (Slen &amp; Connell, 1958) while exogenous testosterone has consistently enhanced both greasy and clean wool yields (Slen &amp; Connell, 1958; Osborne, 1968; Southcott &amp; Royal, 1971). Little is known, however, of the effects of the synthetic steroids on wool growth. Coehlo, Galbraith &amp; Topps (1981) reported a reduction in wool per unit body weight in sheep implanted with trenbolone acetate and oestradiol-17β, suggesting lowered efficiency of wool growth. Similarly Yasin &amp; Galbraith (1981) noted that trenbolone acetate, in combination with either oestradiol-17β or zeranol, reduced wool output per unit body weight. Neither of these trials attempted to isolate the effects of trenbolone acetate alone from those of the androgenplus-oestrogen combination.

Rape and sunflower seed meals as supplements for sheep fed on oat straw

Rapeseed meal (RSM), sunflower meal (SFM) and formaldehyde-treated (F) forms of these were compared with urea- and formaldehyde-treated casein (FCAS) as N supplements for sheep fed pelleted diets containing c. 80% oat straw. Sufficient supplement was added to bring the N content of each diet to c. 1.7%, and starch was added to the urea and FCAS diets to make all supplements equal in metabolizable energy content. Based on an assumed fractional outflow rate from the rumen of 0.06 h-1, the ruminal degradability of dietary N varied from a mean of 0.42 for diets containing formaldehydetreated supplements to 0.74 for non-treated supplements. The diets were fed to Crossbred wethers weighing c. 40 kg in a production experiment lasting 12 weeks, and in a metabolism experiment. In the production experiment, penned sheep fed the urea diet ate 1300 g DM day-1, gained 30 g Day-1 and grew 4.5 g clean dry wool (CDW) day-1 . Each of the protein supplements increased DM intake (mean 1860g day-1 P &lt; 0-0l), liveweight gain (mean 148 g day -I, P &lt; 0-001) and wool growth (mean 10.5 g CDW day-1; P &lt; 0.01). Intake and liveweight gain were higher, and wool growth rate lower, on the SFM than on the RSM diet, while formaldehyde treatment of both meals stimulated intake, gain and wool growth although these differences were not always significant. Efficiency of wool growth, expressed as g CDW per g N digested, was least for the urea and SFM diets (mean 0.30), higher for the FCAS, RSM and FSFM diets (mean 0.40) and highest for the FRSM diet (0.48, P &lt; 0.05). Mean digestibilities of organic matter (OM) and cell wall constituents for all diets were 0.47 and 0.44 respectively, with few significant differences between diets. Apparent N digestibility varied from 0.41 to 0.61 for the FRSM and FCAS diets respectively, while estimated true N digestibility varied from 0.72 to 0.88 for the same two diets. Nitrogen balance for the protein-supplemented diets (mean 2.68 g day-1) was higher (P &lt; 0.001) than for the urea diet (-3.77 g day-1). During 6 h post-feeding, the mean rumen pH (6.50) and volatile fatty acid levels (60.9 mM ) showed few differences between diets, whereas rumen ammonia concentrations were significantly reduced by formaldehyde treatment of the protein supplements. It was concluded that RSM and SFM were effective supplements for sheep offered straw, with little difference between them except for wool growth. Formaldehyde treatment to confer resistance to ruminal degradation reduced N digestibility, but increased the efficiency of utilization of digested N for wool growth.

The effect of birth status on the level and efficiency of wool production by new zealand corriedale two-tooth rams and ewes

ABSTRACTForty-four single- and twin-born New Zealand Corriedale two-tooth ewes and rams aged 14 months were fed individually, in pens, a pelleted ration adjusted to maintain body weight after allowing for wool growth. The sheep were fed for a 3-month settling period, followed by a 3-month experimental period, during which wool growth, fibre diameter, fibre length and net efficiency of wool growth were measured.Since the wool-growth cycles of the two sexes were found to be out of phase, a valid comparison of the sex data was not possible. Such phase differences may be important in some experimental designs. Significant sex by birth status interactions were identified for all wool production parameters except fibre length, confirming that care must be taken in assigning correction factors during selection of rams and ewes. The general trend was for single-born ewes to produce more and coarser wool more efficiently than twin-born ewes, while the differences between single- and twin-born rams were much smaller. Single-born animals were heavier than twin-born (P&lt;0·01).Individual values for wool growth and net efficiency varied by a factor of three within sex groups, indicating a considerable scope for selection

The wool growth response to the annual cycle of grazing intake in Cheviot wethers

Wool-growth rates were measured at monthly intervals on eight free-grazing Cheviot wethers. Nutrient intakes provided by the upland environment were measured at the same intervals during the 2½ years. Analysis of periodic regression disclosed that both intake and wool growth had similar seasonal cycles but were slightly out of phase. It was concluded that the similarity was largely due to the relationship of both characters with some independent seasonal variable. The seasonal cycle of efficiency of wool growth depends on the time relationship between its two components, but it was found that variation amongst sheep in wool production was greater in the summer months and this depended more on variation in overall efficiency than on variation in grazing intake.

Selection for weaning weight in Merino sheep. 3. Maintenance requirements and the efficiency of conversion of feed to wool in mature ewes

Net and gross efficiencies of wool growth have been estimated for ewes from three Trangie selection flocks, one selected for high weaning weight (Weight Plus), one for low weaning weight (Weight Minus), and a random control flock. Weight Plus ewes had 15 and 11 per cent heavier body weights than Weight Minus ewes at maintenance and unlimited levels of feeding respectively. At each level, feed intake was proportional to body weight both between and within flocks. In addition, the feed costs of a unit gain and loss of body weight were the same for each flock at each level of feeding. The Weight Plus ewes grew 7 and 10 per cent more wool than Weight Minus ewes at maintenance and unlimited levels of feeding. Consequently, there was only a small difference between the flocks in efficiency of conversion of feed to wool at maintenance, and there was no difference on unlimited intake. These results indicate that there is no genetic correlation between weaning weight and efficiency of conversion of feed to wool. At the three levels of controlled feeding (543, 725, 902 grams of dry matter a day) there were no differences in gross efficiency of wool growth, either between flocks or between levels within flocks, despite differing changes in body weight. During unlimited feeding, gross efficiency of wool growth was lower than that during controlled feeding. This was due to a reduced response in wool growth, as feed costs per unit body weight change were constant. As both production and feed intake changed in proportion to body weight, it is concluded that attention to weaning weight has little place in a Merino breeding program aimed at increasing wool production. However, selection for high weaning weight may be a useful tool in selecting ewes for crossbreeding because of the associated increases in milk production and lamb growth rate.