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ABSTRACT
[ Vol. XXII, Part IV
on dams was carried out and to compensate for the possible effect due to variation
in total number of classified dams and the proportion of dams in the 2 groups, weigh-
ing of data was carried out. The weight finally selected was nk/n+k, where n and
k are number of susceptible and resistant dams respectively.
The average inter-herd regression of daughters on dams using the method was
0.259 for the 15 Canterbury herds and 0.161 for the 12 Manawatu herds. The overall
average for the 2 groups was 0.191. The calculated estimate of heritability of
individual differences in susceptibility to mastitis comes to 0.38 with a range of
0.06—0.70 for 95 per cent confidence interval. Though the author admits that the
data are scanty to draw conclusion within narrow limits. The results obtained,
indicate good evidence that heredity plays a moderately large part in cow developing
mastitis. Selection against cows which are severely affected, or have severely
affected sisters or daughters, is suggested as a genetic method of controlling the
incidence of mastitis.—[S.S.P.].
Rearing Chicks on Home Grown Feeding-stuffs. SHAW, R. B. AND NIGHT-
HALL , E. W. World's Poultry Science Journal 6, 3, 201-206
T HE results indicate that chicks can be reared on a ration without any protein-
rich supplement provided they have access to good grass. A hatch of 192
chicks was divided into three equal groups. Group ' A ' was fed on Sussex Ground
Oats plus minerals, Group ' B ' on Sussex Ground Oats, Bean Meal plus minerals,
and control Group ' C ' on a more normal rearing ration. Cod Liver Oil was included
in all rations for the first ten weeks. All mashes were fed dry with grain fed in the
evening. The chicks were allowed on to the grass in covered wire runs at ten days
old and were moved daily. The average growth of chickens in Groups A and B were
slow in the early stages but improved fairly rapidly as maturity was reached. At
eight weeks the average weight per-chicken in Group ' C ' was 9.85 oz. more then in
Group ' B ' and 8.26 oz. more than Group ' A ' (no protein supplement). At twelve
weeks the differences in weight were not much greater and at 24 weeks the average
body weight of the pullets in Groups A, B and C were 58.94, 60.77 and 71.70 ozs.
respectively. Better early growth would probably be obtained if a more palatable
vegetable protein were used. It was observed that growing chickens would not
graze well unless they were given sufficient palatable foods to keep them contended.—
[S.B.].
Significance of the Differences in Digestibility of Feeds by Cattle and Sheep.
CIPOLLON, M. A., SCHNEIDER ,B. H., LUCAS, H. L.,AND PAVLECH , H. M. (1951).
J. Anim. Sci. 10, 337-343
I N the United States, although cattle account for 94 per cent of the total feed
consumption by ruminants, as many as 71.5 per cent of the digestion trials
with ruminants have been conducted on sheep. Generally the efficiency of digestion
of feeds by cattle and sheep has been taken to be essentially the same. But on
critical investigation of the published data allowing direct comparison of the diges-
tive efficiency of cattle and sheep fed identical rations, it seems that the digestion
coefficients for the two species may not be quite interchangeable.