- The present study was designed to investigate the relationship
of milk production and milk quality to growth rate and certain organ-oleptic
measurements of lambs of mutton breeds, Nine mature ewes
in their fourth lactation of the Border Cheviot, Dorset Horn,
Columbia, Suffolk, and Willamette breeds were acquired making a
total of 45 ewes.
An attempt was made to synchronize parturition, The reason
for synchronizing parturition was to have all the ewes lamb during a
narrow interval of days so that milk production and its effects on
growth could be measured under environmental conditions that were as
similar as possible.
The ewes were milked by use of oxytocin to cause them to
eject the milk in the udder after which they were kept separate from
their lambs for six hours and milked again. The milk obtained for the six-hour period was weighed and the quantity recorded. A
representative sample was taken from milk of each ewe for composition
analyses. The average percentage composition of the milk from
ewes was found to be: protein, 5.46; lactose + ash, 5.40; solids-not-fat,
10.86; fat, 8.43, total solids, 19.29; and water, 80.71. There
were no significant differences (P >.05) between breeds for the percentage
of milk components studied.
During the first eight weeks of lactation the breeds studied
had produced 74 percent and by ten weeks they had produced 87 percent
of the milk yield for the total lactation period. The breeds
ranked in the following order on the basis of milk yield and milk
quality: Suffolk, Willamette, Dorset Horn, Border Cheviot, and
Columbia. The latter two breeds were approximately equal. Ewes
nursing twin lambs produced 25 percent more milk than ewes nursing
single lambs, The peak of lactation occurred in the third and fourth
weeks of lactation, The average grams of milk produced per day for
ewes nursing single and twin lambs, respectively, are as follows for
the five breeds: Border Cheviot 1, 016, 1, 669; Dorset Horn 1, 617,
1, 778; Columbia 1,366, 1,684; Suffolk 1,527, 2,287; and Willamette
1, 552, 1, 951.
A set of twins gained on the average 40.7 percent more than
a single lamb. Single lambs gained 15.7 percent rnore weight than
the average of a set of twins. The Willamette had the highest average daily gain and was followed in order by the Suffolk, Columbia, Dorset
Horn, and Border Cheviot.
The average grams of milk consumed for each gram of
gain for single and twin lambs, respectively, are as follows; Border
Cheviot 3.964, 3.455; Dorset Horn 5.472, 3.424; Columbia 4.406,
3.716; Suffolk 4.326, 3.882; and Willamette 4.193, 3.114. It was
concluded that a large portion of the nutrients required for lamb
growth and fattening must be supplied by foods other than milk.
Highly significant differences among breeds of sheep (P <.01)
were found to exist for weaning weight. Weight differences between
sexes within a breed were not significant, and there appeared to be
no significant interaction between breed and sex.
A correlation coefficient of 0.84 between total gain of the lamb
and total grams of milk produced by its dam was highly significant.
Seventy percent of the variation in total gain is accounted for by variation
in total milk yield.
The breeds ranked in the following order for carcass tenderness
and composite preference of meat; Columbia, Willamette,
Dorset Horn, Border Cheviot, and Suffolk.
It was postulated that lamb weight at eight to ten weeks of age
would be a better criterion by which to cuIl low producing ewes and to
select replacement females and males than the 120-day weight. The
conformation score, composite preference score, tenderness score, and the percentage of protein, solids-not-fat, milk fat, and total
days nursed, were not affected by the breed, sex or rearing of the
lambs studied. Only 100-day weight and condition scores were
affected by breed. Total gain of the lamb was affected by the quantity
of milk and milk components produced by the dam.