Wool Growth In Sheep Research Articles

Increasing GSH-Px Activity and Activating Wnt Pathway Promote Fine Wool Growth in FGF5-Edited Sheep.

Fibroblast growth factor 5 (FGF5) plays key roles in promoting the transition from the anagen to catagen during the hair follicle cycle. The sheep serves as an excellent model for studying hair growth and is frequently utilized in various research processes related to human skin diseases. We used the CRISPR/Cas9 system to generate four FGF5-edited Dorper sheep and only low levels of FGF5 were detected in the edited sheep. The density of fine wool in GE sheep was markedly increased, and the proportion of fine wool with a diameter of 14.4-20.0 μm was significantly higher. The proliferation signal in the skin of gene-edited (GE) sheep was stronger than in wild-type (WT) sheep. FGF5 editing decreased cortisol concentration in the skin, further activated the activity of antioxidant enzymes such as Glutathione peroxidase (GSH-Px), and regulated the expression of Wnt signaling pathways containing Wnt agonists (Rspondins, Rspos) and antagonists (Notum) in hair regeneration. We suggest that FGF5 not only mediates the activation of antioxidant pathways by cortisol, which constitutes a highly coordinated microenvironment in hair follicle cells, but also influences key signals of the Wnt pathway to regulate secondary hair follicle (SHF) development. Overall, our findings here demonstrate that FGF5 plays a significant role in regulating SHF growth in sheep and potentially serves as a molecular marker of fine wool growth in sheep breeding.

Seasonal pattern of skin follicles activity and fibre growth in grazing fat-tailed Kermani sheep in the South of Iran

Photoperiod is known to be important in regulating the pattern of wool growth in sheep. The aim of this study was to investigate the effect of natural changes in photoperiod on live weight, skin follicle activity and fiber characteristics of grazing Kermani sheep in the south of Iran, Jiroft (28° 40′ N and 57° 44′ E, elevation 650m). Ten male and 10 female Kermani sheep with initial live weights of 31.9±0.8 and 30.7±0.9kg (mean±s.e.) respectively, were used in a 365day study. Percentage of active primary (PAP) and percentage of active secondary (PAS) follicles, ratio of secondary to primary follicles (S/P) and follicle density (FD) were measured in skin samples, taken from the right mid-side of the animals at monthly intervals. Greasy and clean wool growth rates and fibre diameter were determined from patch samples (10cm×10cm) harvested at the end of every month. The value for PAP was greatest (p<0.05) in summer and spring and lowest (p<0.05) in winter (98.2±0.8, 84.1±0.9, 75.6±0.8 and 97.0±1.1% for summer, autumn, winter and spring, respectively); seasonal differences in PAS were similar (99.3±0.8, 88.5±0.7, 82.9±0.8 and 98.9±0.7% for summer, autumn, winter and spring, respectively). Clean wool growth rate was greatest (p<0.001) in summer and spring, and lowest (p<0.001) in winter (0.7±0.03, 0.4±0.04, 0.3±0.01 and 0.7±0.05mg/cm2/day for summer, autumn, winter and spring, respectively). Fibre diameter was greatest in spring (34.8±0.3μm) and lowest in winter (29.1±0.2μm). The values for wool growth rates and fibre diameter were greater (p<0.05) in male rather than those observed in female sheep. Fibre and skin follicle characteristics were not affected by a season×sex interaction. These results demonstrated that there is a seasonal pattern in fibre follicles activity and wool growth in grazing Kermani sheep.

Trial of human laser epilation technology for permanent wool removal in Merino sheep.

To assess whether human laser epilation technology can permanently prevent wool growth in sheep. An observational study. Two commercial human epilation lasers (Sharplan alexandrite 755 nm laser, and Lumenis LightSheer 800 nm diode laser) were tested at energies between 10 and 100 J/cm2 and pulse widths from 2 to 400 ms. Wool was clipped from flank, breech, pizzle and around the eyes of superfine Merino sheep with Oster clippers. After initial laser removal of residual wool to reveal bare skin, individual skin sites were treated with up to 15 cycles of laser irradiation. Behavioural responses during treatment, skin temperature immediately after treatment and skin and wool responses for 3 months after treatment were monitored. A clear transudate was evident on the skin surface within minutes. A dry superficial scab developed by 24 h and remained adherent for at least 6 weeks. When scabs were shed, there was evidence of scarring at sites receiving multiple treatment cycles and normal wool growth in unscarred skin. There was no evidence of laser energy level or pulse width affecting the response of skin and wool to treatment and no evidence of permanent inhibition of wool growth by laser treatment. Laser treatment was well tolerated by the sheep. Treatment of woolled skin with laser parameters that induce epilation by selective photothermolysis in humans failed to induce permanent inhibition of wool growth in sheep. Absence of melanin in wool may have contributed to the result.

Sheep of divergent genetic merit for wool growth do not differ in digesta kinetics while on restricted intakes

Sheep selected for high wool growth were previously shown to exhibit higher microbial protein outflow from the rumen and higher uptake of amino nitrogen in portal blood than those selected for low wool growth. This suggests that genetic selection for wool growth may induce changes in foregut physiology. This study was undertaken to determine whether differences in digesta kinetics, especially mean retention mime (MRT), are associated with differences in fleece production between sheep with low or high estimated breeding values (EBVs) for fleece weight. Twenty mature Merino wethers with uniform EBVs for liveweight were allocated to two groups of 10 animals on the basis of high or low EBVs for yearling fleece weight. Five sheep with low-EBVs and five sheep with high-EBVs for fleece weight groups were allocated in a crossover design to low and high feeding-level treatments, which comprised a blended hay diet fed at maintenance or 1.5 times maintenance. All sheep were given single doses of chromium-mordanted fibre and cobalt-EDTA as inert, non-digestible markers. Digesta kinetics was determined by analysis of the faecal marker excretion patterns using a compartmental model. Higher feed intakes from animals fed 1.5 times maintenance were associated with higher rates of wool growth and higher masses of indigestible fibre in the gut, but reduced MRT of digesta. Although sheep with higher EBVs for fleece weight had higher wool growth rates, there was no indication that these wool growth differences were associated with differences in digesta kinetics. The lack of interaction between feeding level and genotype suggests that MRT did not contribute to genotype differences in wool growth in sheep fed restricted intakes. The differences in wool growth among commercial Merino sheep with divergent fleece weight EBVs achieved by multi-trait selection are not attributable to differences in digesta kinetics, at least when feed is not available ad libitum.

Genetic engineering to improve quality, productivity and value of crops

Over the next 25 years, we believe that the most significant changes in crops will come about by applying genetic engineering tools. Crops may be bioengineered to produce modified kinds of starch, oils and high-value proteins for better nutrition, medical diagnostics and industrial uses. For example, walnuts and peanuts containing healthier oils, along with oxidative stability, could become available to consumers. Seedless vegetables and other fruits should appear in the marketplace within 10 years. Oil-producing seed crops may be modified to create specialty oils for a variety of nonfood products such as detergents, lubricants, inks and dyes. Feed seeds engineered to produce higher concentrations of sulfur-containing amino acids could improve wool growth in sheep. Plants could be modified to deliver oral vaccines that prevent diseases such as hepatitis and influenza. Strawberries are being targeted by genetic engineering to extend their shelf life, and within 25 years fields may be planted with varieties that allow farmers to control the timing of fruit production. Although currently controversial, we believe genetic engineering will prove to be invaluable to the future improvement of agricultural systems. To enhance the competitiveness of California agriculture, government, university scientists and industry must work together to ensure the application of genetic engineering tools to improve crops.

Long-term effects of short-term provision of protein-enriched diets on resistance to nematode infection, and live-weight gain and wool growth in sheep

Weaner sheep that had been hand-fed on diets containing increasing concentrations of protein for a 9-week period (when uninfected, or infected with Haemonchus contortus) were studied during the next 69 weeks when put on to pasture as a single, unsupplemented flock. During the 9-week period, groups of 12 sheep (six infected, six uninfected) were offered one of five iso-energetic (9.0 MJ kg −1) diets containing 10, 13, 16, 19 or 22% crude protein. All sheep were treated with anthelmintic at the end of the 9 weeks and then put out to pasture for 69 weeks, where they were all subject to the same environmental variables including nematode larval challenge. During the grazing period, animals that had previously received the higher protein diets consistently had higher live-weight gain and wool production, higher antibody responses to both H. contortus and Trichostrongylus colubriformis antigenic challenge in vitro, and lower faecal nematode egg counts than did the lambs previously offered the lower protein diets. Faecal egg counts of the grazing sheep that had been artificially infected with H. contortus while being hand-fed were similar to those of the uninfected sheep and there was no interaction between previous infection and dietary protein concentration. We conclude that short periods of enhanced post-weaning nutrition can have long-term and perhaps life-long effects on production.

Spray-topping annual grass pasture with glyphosate to delay loss of feeding value during summer. IV. Diet composition, herbage intake, and performance in grazing sheep

We report the effects of spray-topping annual grass pasture with glyphosate (180 g a.i./ha as Roundup CT, at the seed head emergence stage) on the nutritive value of herbage and on subsequent performance of grazing sheep. Eight 1-ha plots, consisting of 4 sprayed and 4 unsprayed (control) plots, were set-stocked with Merino wethers (18 months old, 12 sheep/ha) from 8 days after anthesis in the control plots (late spring) until 165 days after anthesis (mid-autumn). In 4 periods (15–20, 36–41, 71–76, and 99–104 days after anthesis; Periods 1–4, respectively) sheep were dosed with synthetic alkanes and herbage and faecal samples were taken, in order to estimate diet composition (in terms of plant parts), faecal output, herbage intake, and the digestibility of the whole diet. As described in our earlier papers, spray-topping reduced the yield of pasture dry matter, but also slowed the loss of water-soluble carbohydrate (WSC) and digestibility during pasture senescence. The present paper shows that as a result, sheep grazing sprayed herbage in Periods 1 and 2 consumed significantly more organic matter (OM) and digestible OM (DOM) than sheep grazing the control pasture. Their diet contained a higher proportion of stem with a higher WSC concentration than that of the sheep grazing the control plots. The proportions of different plant parts (leaf blade+sheath, stem, seed head) in the diet of both the plot sheep and oesophageally fistulated (OF) sheep, which grazed treatments for short periods, differed significantly between treatments in all periods. However, the compositions of the diets selected by plot and OF sheep were similar. These results confirmed diet preferences measured using housed sheep and demonstrate the usefulness of alkane-based procedures for quantifying diet composition and intake in grazing animals. As a result of their higher intake of DOM, sheep grazing sprayed herbage had a significantly higher liveweight gain over the first 2 periods (40 g/day). In Period 3, sheep grazing sprayed herbage consumed more OM than sheep grazing control herbage. However, DOM intakes from sprayed or control plots were not significantly different in either Period 3 or Period 4, and were lower than in Periods 1 and 2. Sheep grazing both treatments lost liveweight at a similar rate over this time. Wool growth in sheep grazing sprayed herbage was improved by 10% during the experimental period; wool strength was also improved significantly. The implications for the management of sheep grazing spray-topped pastures over summer are discussed.

Phenotypic characterization of rambouillet sheep expressing the callipyge gene: I. Inheritance of the condition and production characteristics.

The objectives of this study were to determine the model of inheritance of the callipyge gene and to evaluate the growth, ADFI, feed efficiency, reproductive performance, and wool growth of sheep that are heterozygous for the callipyge gene. Ewes (n = 236) with a normal muscle phenotype and genotype were mated to three heterozygous rams that expressed the callipyge gene. Lambs (n = 311) were subjectively classified at weaning (90 to 120d) according to muscle phenotype by a panel of three evaluators working independently. The callipyge muscle phenotype was expressed in 150 lambs, whereas 161 lambs expressed a normal muscle phenotype. The percentage of lambs expressing the callipyge muscle phenotype (48.2%) did not differ (P > .1) from the expected 50%. Growth rate was similar for lambs of both phenotypes regardless of sex. Feed efficiency was superior (P < .05) for both male and female lambs with the callipyge muscle phenotype. Average daily feed intake was lower for male (P < .02) and female (P < .004) lambs with the callipyge muscle phenotype. Grease fleece weight and staple length at 12 mo were superior (P < .03) for ewes with a normal muscle phenotype. These results indicate that the callipyge gene in sheep is dominant when inherited from the paternal parent and lambs expressing the callipyge gene have increased feed efficiency and reduced ADFL.

The Condensed Tannin Content of a Range of Subtropical and Temperate Forages and the Reactivity of Condensed Tannin with Ribulose- 1,5-bis-phosphate Carboxylase (Rubisco) Protein

A series of subtropical grasses and temperate grasses, herbs and legumes were analysed for the presence of extractable and bound condensed tannin (CT) using colorimetric analysis by the butanol–HCl method. Condensed tannins are routinely purified using affinity chromatography with Sephadex LH-20 as a matrix. Therefore, Sephadex LH-20 extracts were further analysed for the presence of CT by 13C nuclear magnetic resonance, for anthocyanidin formation after butanol–HCl treatment and for their ability to precipitate ribulose-1,5-bisphosphate carboxylase (Rubisco) protein from lucerne, at pH 7·0. Criteria for the presence or absence of CT were defined. Trace amounts of CT (0·2–2·5 g kg−1 dry matter; DM) were identified and confirmed in summer grass (Digiteria sanguinalis), perennial ryegrass (Lolium perenne) and red clover (Trifolium pretense), with chicory (Chicorium intybus), lucerne (Medicago sativa) and plantain (Plantago lanceolata) identified as probably containing CT. It was concluded that the subtropical grasses kikuyu (Pennisetum clandestinum), paspalum (Paspalum diatatum), smooth witchgrass (Panicum dichotomiflorum) and crowfoot (Eleusine indica) and the temperate grass, Yorkshire fog (Holcus lanatus) probably did not contain CT. Analysis of the extractable fractions by vanillin–HCl gave higher values for CT than analysis by butanol–HCl and wrongly identified some forages as containing trace levels of CT. It was concluded that vanillin–HCl was not specific enough for the detection of trace levels of CT in forages. These results raise the possibility of plant selection programmes to increase the level of CT in grazed forages to approximately 5 g kg−1 DM, the suggested minimum level required to prevent bloat in cattle and to increase wool growth in sheep. It is suggested that this be considered for perennial ryegrass, chicory, red clover and lucerne.

Development of an In Vitro technique to investigate the role of biotin in regulating wool growth in sheep

The development of in vitro culture techniques (Ibraheem et al, 1993, 1994) for the study of caprine hair follicles has proved useful in elucidating aspects of the control of cashmere and mohair fibre production. There is a similar need to investigate nutritional and other factors which regulate the growth of sheep wool. The aim of the present study was to develop an in vitro technique to study the role of the B-vitamin biotin in controlling growth and viability of sheep wool follicles.

Development of an In Vitro technique to investigate the role of biotin in regulating wool growth in sheep

The development of in vitro culture techniques (Ibraheem et al, 1993, 1994) for the study of caprine hair follicles has proved useful in elucidating aspects of the control of cashmere and mohair fibre production. There is a similar need to investigate nutritional and other factors which regulate the growth of sheep wool. The aim of the present study was to develop an in vitro technique to study the role of the B-vitamin biotin in controlling growth and viability of sheep wool follicles.

A biotechnological approach to improving the nutritive value of alfalfa.

The postruminal supply of the sulfur-containing amino acids, methionine and cysteine, has been reported to be a major limitation to wool growth in sheep. We aim to improve the protein quality of forage for ruminants by introducing into alfalfa chimeric genes encoding a ruminally stable, sulfur amino acid-rich protein from sunflower seeds. Four gene constructs were transferred to Australian commercial cultivars of alfalfa using Agrobacterium tumefaciens-mediated transformation and selection with phosphinothricin (PPT). Modification of the sunflower seed albumin protein-coding region by addition of the coding information for an endoplasmic reticulum (ER) retention signal was found to greatly increase the level to which the sulfur amino acid-rich protein accumulated in the leaves of transgenic alfalfa plants. The Cauliflower Mosaic Virus (CaMV) 35S promoter and two light-regulated plant gene promoter regions were compared for their ability to direct high-level expression of the introduced genes in alfalfa leaves. The highest expression of sunflower seed albumin was found in transformants bearing a gene incorporating the promoter from the Arabidopsis thaliana ats1A gene, which encodes the ribulose bisphosphate carboxylase small subunit. The highest level of sunflower seed albumin found in transgenic alfalfa leaves was estimated to constitute .1% of soluble leaf protein. This level of accumulation of the foreign protein would be predicted to supply an extra 40 mg of sulfur amino acids daily to sheep fed the modified forage. Published studies in which wool growth rates were significantly increased employed supplementation of approximately 1 to 2 g of sulfur amino acids daily.

Nutritional responses in wool growth by four Merino genotypes of differing wool growth performance

Sheep from four Merino flocks, different in annual clean fleece production when grazed together, were offered a range of nutritional treatments to compare their ability to digest dietary organic matter (experiment 1) and to compare the relationships of wool growth and fibre diameter with nutrient intake (experiment 2). The sheep were selected from a finewool (Fl), a strong wool (S), and two medium-Peppin (MP6 and MP10) flocks. The nutritional treatments varied intakes of two pelleted diets-B and F. Diet B consisted of oat grain, lucerne chaff, and oaten straw, while diet F was as for B but fortified with fishmeal. The digestibility of both diets was negatively related to the level of intake, and there were some differences between the flocks in their ability to digest organic matter. Clean wool growth per unit area of skin was curvilinearly related (P &lt; 0.001) to N intake, but was not influenced by diet per se. The regression coefficient for the relationship of clean wool growth with N intake and the estimated maximum wool growth rate of flock F1 were less than the other flocks. However, flock MP10 grew less wool than flocks S and MP6 at any given intake. Variation in (fibre diameter)2 accounted for 0.6 of the variation in wool growth, with responses in fibre diameter to intake being similar to those observed in wool growth. The responses in plasma cystine of the flocks to N intake differed, with the relationship for flock F1 being curvilinear and reaching a maximum at an intake of 27 g N day-1, while the responses of the other flocks were essentially linear. The relationships between plasma cystine level and wool growth differed between the flocks such that wool growth of sheep from flocks S and MP6 was more responsive to increased plasma concentration of cystine.

Effects of pinealectomy on wool growth and wool follicle density in merino sheep.

There is evidence to indicate that pinealectomy may enhance wool growth in the sheep. The aim of this study was to determine the effect of pinealectomy on wool growth and wool follicle density in Merino sheep. Castrated Merino rams (4 months old) were either pinealectomized (P), sham-pinealectomized (S) or not treated (C). Wool growth on mid-side patches was measured every 4 weeks and follicle density was monitored in skin biopsies collected before treatment and at regular intervals for 60 weeks. Venous blood samples were taken on each of these occasions for prolactin analysis. Melatonin concentrations were determined in venous blood collected pre- and posttreatment from samples taken over a 24-hr period during the winter solstice. Pre- and posttreatment plasma melatonin levels (mean +/- SEM) 65 +/- 17 and < 13 pg/ml for P, 86 +/- 21 and 69 +/- 20 pg/ml for S, and 94 +/- 41 and 122 +/- 37 pg/ml for C, respectively, indicated that the pineal glands had been successfully removed. Wool growth, total follicle density and liveweight (mean +/- SEM) did not differ between treatment groups. Measurements at week 60 were 3.9 +/- 0.3, 4.1 +/- 0.2, and 3.8 +/- 0.3 gm clean wool/100 cm2; 66 +/- 6, 69 +/- 7, and 64 +/- 3 follicles/mm2; and 50.4 +/- 1.3, 50.8 +/- 1.4, and 52.6 +/- 1.1 kg liveweight for groups P, S, and C, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of bentonite on wool growth and nitrogen metabolism in fauna-free and faunated sheep.

Two experiments were carried out with sheep that originated from a fauna-free flock and were fed a soybean meal-corn silage diet with or without a bentonite supplement. One-half of the sheep fed each diet in each experiment were faunated with a mixed population of ruminal protozoa, whereas the other half of the sheep remained fauna-free until the end of both experiments. Wool growth and daily gain were measured in Exp. 1. (eight rams per treatment), which lasted 110 d, and the metabolic effects in the rumen and intestinal tract of protozoa and dietary bentonite supplement were tested with cannulated wethers (four wethers per treatment) in Exp. 2. The results of Exp. 1 showed decreased wool growth (P less than .05) due to the presence of protozoa in the rumen. Dietary supplementation with bentonite partly offset the decreased wool growth in sheep with protozoa, but there were no effects of dietary bentonite and no protozoa x bentonite interaction (P greater than .05). Daily gain was decreased by the dietary bentonite (P less than .05) supplement but was not affected (P greater than .05) by the ruminal presence of protozoa. In Exp. 2, protozoa increased (P less than .01) the ruminal concentrations of ammonia and decreased (P less than .05) the acetic:propionic acid molar ratio. Fractionation of N in the duodenal digesta flowing from the stomach to the small intestine showed that protozoa decreased (P less than .05) the flow of nonammonia N and bacterial N, and there was a protozoa x bentonite interaction for these effects (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dry or hydrated bentonite on the wool growth and liveweight gain of sheep fed wheat chaff

Many reports on the use of bentonite to increase wool growth indicate variable responses and it is often claimed that this variability is related to the chemical characteristics or the form in which the bentonite is fed. This paper describes 3 experiments in which there was consistency in the type and form of the clay. There was also comparison of the effects of dry and hydrated bentonite. In the first experiment, 64 sheep were individually penned and fed wheat chaff ad libitum. Thirty sheep were fed chaff only, 17 sheep received dry bentonite added to their chaff (20 g/kg chaff) and another 17 sheep had 23.7 g/day of bentonite added to their drinking water. Inclusion of bentonite in the drinking water significantly increased wool growth (P&lt;0.05, 14.8%) and increased chaff intake (P = 0.08, 6%). In the second experiment, 105 sheep were penned in groups of 7 and each pen fed wheat chaff ad libitum. Five pens of sheep had dry bentonite added to their chaff (20 g/kg chaff) while another 5 pens had bentonite added to their drinking water (23.7 g/sheep.day). There were 5 pens of sheep which received no bentonite. Inclusion of bentonite either in the drinking water or in the chaff, significantly increased chaff intake (P&lt;0.05, 6%), but had no effect on wool growth. In the third experiment, 60 sheep were divided into 12 groups and each group grazed individual 0.7 ha of cereal stubble. All groups were supplemented with the equivalent of 200 g of lupin grain/sheep.day fed twice weekly and 6 of the groups were watered by buckets containing hydrated bentonite (11.8 g bentonite/L). In experiments 2 and 3, inclusion of bentonite in the diet or in the drinking water had no effect on wool growth (P&gt;0.05) but liveweight gain was significantly increased (P&lt;0.05). It was concluded that the variability in the response to bentonite was not related to its chemical composition or the form in which it is administered and that, on balance, bentonite does not offer a practical or reliable means of increasing wool growth in sheep.

Wool growth in sheep fed diets based on wheat straw and protein supplements

Wool growth of sheep fed wheat straw and various nitrogen (N) supplements was studied in two experiments lasting 16-20 weeks. In experiment 1, penned Crossbred wethers were fed wheat straw supplemented with urea (36 g kg-1 straw) and starch, or equivalent (N basis) amounts of formaldehyde-treated (F) casein (FCAS), rapeseed meal (RSM) or F-treated RSM or sunflower meal (FRSM and FSFM), all at the same total DM intake of c. 1240 g day-1. They produced from 7.9 to 13.9 g clean dry wool (CDW) day-1, and gained from 40 to 100 g day-1 for the urea and FCAS diets respectively. Mean digestibilities of organic matter (OM) and cell wall constituents were 0.53 and 0.42, with few differences between diets, while N digestibility of the FRSM diet (0.76) was significantly (P &lt; 0.05) lower than all others (mean 0.89). During 1-6 h post-feeding, mean rumen pH and volatile fatty acid levels (6.43 and 55.2 mM respectively) were similar for all diets, whereas rumen ammonia levels were significantly (P &lt; 0.01) higher with the urea and RSM supplements compared with the F-treated supplements. In experiment 2, penned Merino wethers fed 770 g DM day-1 of the urea-supplemented diet produced 5.0 g CDW day-1 and lost 50 g live weight day-1. In other sheep, fed at the same DM intake on wheat straw plus increasing levels (c. 70-350 g sheep-1 day-1) of an FRSM supplement, wool growth was quadratically related to supplement-N intake, with a maximum of 10.1 g CDW day-1 at a N intake of 15.6 g day-1. Digestibility of OM and N balance were significantly (P &lt; 0.05) reduced at FRSM levels &lt; 127 g sheep-1 day-1, while mean rumen ammonia levels during 6 h post-feeding remained &lt; 70 mg N L-1 at FRSM levels &lt; 183 g sheep-1 day-1. It was concluded that protein supplements resistant to ruminal degradation will substantially increase wool production in sheep fed straw diets at approximately maintenance levels.

Liveweight gain and wool growth in sheep fed rations containing virginiamycin

The feed additive virginiamycin was evaluated for its potential to improve wool growth and liveweight gain in Merino sheep in 2 experiments. In the first experiment 84 wethers (about 10 months old) were housed individually and fed ad libitum a pelleted diet based on lucerne chaff, lupin, and barley grain. Control sheep (28) were fed an unmedicated diet, and 14 in each of 4 groups were given diets containing 10, 20, 40, or 60 mg virginiamycin/kg pellets. Virginiamycin was found to reduce feed intake during the first 4-5 weeks of the experiment when included at levels 220 g/t. There was a dose-related reduction in liveweight gain. There was no significant effect of virginiamycin on wool growth. In the second experiment, weaners and adults from 2 locations in Western Australia, Mount Barker (relatively high rainfall) and Wongan Hills (relatively low rainfall and shorter pasture-growing period), were housed individually in a shed and fed a pelleted diet at rates equivalent to 3.5 and 3.1%, respectively, of liveweight for weaners and adults. The pelleted ration was based on wheat and lucerne chaff, lupin grain, and fishmeal. Virginiamycin was included at 20 mg/kg pellets for 16 of 40 sheep of each age and location. The remaining sheep were fed the unmedicated diet. Feed conversion and liveweight gain improved (P&lt;0.05) in response to the inclusion of virginiamycin during the first 4 weeks of the trial, but wool growth was reduced over the same period. Virginiamycin had no effect on fibre diameter in sheep in either experiment.

The effect of footrot on body weight and wool growth of sheep

Body weight and traits associated with production of wool were measured over a 2-year period between 1985 and 1987 in south-western New South Wales in a flock of Merino wethers experimentally infected with footrot. The disease was allowed to spread freely amongst 150 of the flock but kept at very low prevalence in the remaining 50 by preventive footbathing during transmission periods. Severe, underrunning footrot had a significant adverse effect on body weight, for each year of the trial. Body weight was most severely reduced at times of the year when footrot was spreading among animals and lesions were severe. The mean body weight of the infected group at the end of the 2 years of observation was 7.3 kg (11.6%) below that of the control group. Footrot also depressed wool growth, with the mean clean fleece weight of the infected group being 0.4 kg (8%) lighter than that of the controls at each of the 2 annual shearings. There were no consistent differences between the groups for the other wool characteristics measured.

The effect of bentonite on wool growth, liveweight change and rumen fermentation in sheep

An experiment was conducted to evaluate the use of 3 bentonite clays in sheep. Seventy-eight Merino ewes (about 20 months of age) were housed individually and fed either a pelleted diet based on lucerne, lupins and barley or chaffed wheat-hay. The experiment consisted of an initial period (8 weeks) during which all animals received these diets without bentonite, followed by a 9-week experimental period when bentonite clays were included in the feed at a level of 25 g/kg. None of the 3 bentonite clays had any significant effect on liveweight change or wool growth in sheep fed either diet. There was also no significant effect of the clays on rumen ammonia or volatile fatty acids concentrations in sheep fed wheat chaff. In sheep fed the pelleted diet, 2 of the clay samples increased the molar proportions of acetate and decreased the molar proportion of propionate relative to the control group.