Effect of the Shearing Date on Wool Growth on Native Pasture in Merino Sheep

Fernandez Abella D*, Irabuena O, Sterla S and Hernandez Ruso Z

Keywords: Sheep; Merino; Shearing Date; Wool Growth

Introduction

Is know the effects of time of shearing (twice or three time of year) [1, 2] or autumn versus spring [3, 4, 5], or shearing period of gestation (before or after lambing) [3, 6] on the quality and production of wool, and lamb survival [6, 7, 8]. However, little information is available on the effect of the shearing date on wool growth. Previously, in the Powarth breed has been shown the effect of different date in the spring of shearing in wool production on basaltic nature pastures [9]. In late winter, shearing determine lower wool growths corresponding to lower supply of native pastures [9]. This indicates that the shearing date can sharply infer in the production of wool from a farm, economically affecting its returns.

Thus, the aim of the present work was to study the effect Investigation Paper

of date shearing in another type of nature pasture (crystalline basement soil) on wool production.

Materials and Methods

The experiments took place in a farmer situated in the south part of Uruguay (latitude of 43° 39’ South, longitude of 54°40’ West), on native pasture (crystalline basement soil).

Thirty Merino Australian castrated males similar in age (3-year-old), body weight, quality and quantity of wool were randomly separated into three experimental groups: shearing September 15, October 15 and November 15.

Tattoo Patch method [10, 11] was used to determine wool growth, taking samples (10 x 10 cm) every 60 days in the right rib of the animal. Wool yield was determined and fiber diameter was determined by AIR Flow [12]. Body weight was measured monthly; the weight of live weight without wool is calculated through the calculation of existing wool according to that obtained in the Patch. The fleece weight was determined with a precision balance (+0.100 Kg).

Pasture growth (exclusion cages), protein (Microkjeldhal) and dry matter were determined in the pasture [13, 14].

During the treatment period the wethers had good body condition and received drug treatments to minimize the parasitic burden.

Statistical analyses were computed using the GLM or FREQ procedures of the SAS (2008) System for Linear Models. The significance level was considered for values of P < 0.05 (Figure 1).

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Results and Discussion

The results show differences between shearing dates increasing the weight of fleece when the shearing is already made in the spring (Table 1). The maximum wool growth that occurs three weeks post shearing was enhanced by the quantity and quality of pastures existing in November, as well as by a favorable photoperiod (long days) [15, 16]. Similar data have been reported by Fernandez Abella, et al. [9] in Polwarth breed on Basalt nature pasture, who obtained higher wool production in October-November versus August (3.86 vs 4.29 Kg, fleece weight), being a value for intermediate September (4.01 Kg).

In this work, results indicate an interaction between shearing date and nutrition, found by the correlation obtained between the weight of clean wool of the patch square (WCWPS) and the growth of the pasture (r=0.45; p<0.05). Significant differences were observed between shearing dates and wool growth (11.8g day-1 for September and 13.1g day-1 for October-November (p<0.05), explained by increased growth in spring-summer, which determined greater animal weight, as well as fleece weight. However, there were no different in fiber diameter (p >0.05) (Table 1).

There were different in body weight and fleece weight (p< 0.05; Table 1). Body weight follows the pasture production curve, with highs in summer-early autumn and lows in winter-early spring. These results are consistent with those obtained by Williams, et al. [16]; Hawker, et al. [17] who confirm that body weights accompany the growth curve of pastures. However, wool growth is delayed by 3-4 weeks in response to nutrition changes [19].

There were annual differences in wool growth rate, being in the second year largest due to higher growth during autumn, compared to the first year (Table 2). The average daily growth rate for the two years was 1.38; 1.70 and 1.73 mg/cm2 for each group (September, October and November, respectively). The maximum potential rate was not reached (2.0 mg/cm2) [19]. Similar resultants were observed on basaltic pasture [9].

The wool yield evaluated in the Patches shows a decrease in the winter, due to lower precipitation, lower diameter and increase in greasy content according to results observed by Hemsley, et al. [20]. Fiber diameter increases in all groups from the shearing to the maximum at the end of summer, then decreases to become minimal in the winter. There were differences in the diameter of the fibers, September shearing determined lower values (p<0.05). The length of wool fibers has seasonal variations, but not as marked as the diameter (multiple correlation WCWPS, diameter and length of the fibers 0.94). The correlation obtained between fleece weight and annual WCWPS was 0.49 and 0.60, for each year. The low correlation is based on the surface of the Patch performed is the same in all animals, however the body surface is different between individuals.

a versus b : p <0.05 Table 2: Wool growth (mg/cm2 day -1) determined by Tattoo Patch every 60 days according to shearing date.

The decrease in the digestibility and protein percentage of the pasture (Table 3) reduce the wool growth. Formoso, et al. [14] reported in the same native pastures (crystalline basement soil) pasture digestibility of 67.3; 57.7; 60.0 and

57.7% for spring, summer, autumn and winter respectively. Changes in pasture growth determine changes in wool growth; however other environmental factors such as temperature and photoperiod also get involved [21, 22, 23].

Conclusion

In conclusion, in our conditions (breed and native pasture) spring shearing date affect wool growth. There are no reports in the literature on the effect of shearing date on wool growth; except for an experiment conducted on another type of native pasture (Basalt) in our country [9]. Both confirm that in sheep feed pastures, shearing date change the quantity of wool produced.