We examined the influence of the dose of oxytocin i n measurement of milk production in Merino ewes and its effect on fat content. Eight ewes were milked after an intra-venous injection of 2.0 International Units (I.U.) of oxytocin, then milked again after a further intra-venous injection of 0, 0.5, 1.0 and 5.0 I.U. of oxytocin, with the treatments allocated to a double Latin square design. The milk yielded at each treatment was recorded and samples of the milk were analysed for fat content. All oxytocin treatments significantly increased the amount of milk extracted (P<0.01), but did not affect the fat content of the milk. The dose-response curve showed a plateau at the 1 I.U. level. It was therefore concluded that 1 I.U. is the most suitable dose for measuring milk output in Merino ewes and that, within the range of doses tested, oxytocin does not affect the fat content of the milk withdrawn.
This study examined differences in fibre diameter profiles (FDPs) and midside
characteristics of Merino sheep in 2 environments, 4 bloodlines, 3 years, and
44 sire groups. Environment significantly (P < 0.05)
influenced all characteristics except one measure of fibre diameter change and
staple length. Bloodline also significantly (P <
0.05) influenced all characteristics except staple strength. The maximum fibre
diameter, one measure of fibre diameter change, and staple length were
significantly different (P < 0.05) between sires.
Variation in fibre diameter profile characteristics between bloodlines and
sires changed across the environment in which the sheep are maintained.
Despite these differences between bloodlines and sires in the FDP, midside
mean fibre diameter, fibre diameter variation, and staple length, there were
no significant differences between bloodlines in staple strength.
The relationships between the FDP and midside characteristics with staple
strength were also examined over these bloodlines and environments.
Along-staple variation in fibre diameter (r =
–0.32 to –0.50), between-fibre fibre diameter variation
(r = –0.25 to –0.48), rate of fibre
diameter change (r = –0.16 to –0.38),
and midside variation in fibre diameter (r =
–0.25 to –0.51) were all negatively correlated with staple
strength. Maximum fibre diameter (r = 0.08 to
0.18), minimum fibre diameter (r = 0.25 to 0.49),
and midside mean fibre diameter (r = 0.09 to
0.35) were positively associated with staple strength. FDP characteristics
explained 5–30% more variation in staple strength than could be
explained using the standard midside characteristics of mean fibre diameter,
fibre diameter variation, and staple length alone. These relationships were
also different between environments and bloodlines. The inclusion of the FDP
characteristics as explanatory variables provided an alternative
interpretation for how absolute fibre diameter and fibre diameter variation
combine to explain staple strength. These results suggested that animals and
sires might be able to be selected on FDP characteristics to improve staple
strength. More detailed genetic studies are required before these selection
strategies can be recommended.
An investigation is reported in which the core-test yield was compared with the achieved mill yield for 90 commercial batches cf Australian wool. Eight Australian mills participated in the trial. It was found that the wool hase of the greasy wool (5g%) was directly proportional to the achieved niill yield. The carhonizing loss, which was on the average 3.05% (on an oven-dry basis), was negatively correlated with the vegetahle-matter base of the greasy wool (VMBg/O. The most precise prediction of the achived mill yield was given by the equation: £CCy%= 1.1972 B8%-h 0.1616 VMBg% -5.12, where ECCY% is the estimated commercial carbonizing yield. For the 90 batches in the trial, the standard error of the prediction was 1.95%.
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