USMARC GERMPLASM EVALUATION PROGRAM:

Comparative studies into the performance of South Devon crosses conducted by the United States Department of Agriculture at the Meat Animal Research Centre, Clay Centre, Nebraska.

In 1969, the first live imports of South Devon cattle from England arrived in North America. From these, the US Department of Agriculture selected 27 bulls to be used over Hereford and Angus cows in a major cross breeding trial which is still on-going. In this particular phase of the trial (MARC, Cycle I), the progeny of the South Devon were compared with those sired by selected Hereford, Angus, Limousin, Simmental and Charolais bulls.

References:

Notes:

a. HxA: Hereford over Angus and Angus over Hereford.
......SDx: South Devon cross.
......Lx: ...Limousin cross.
......Sx: ...Simmental cross.
......Cx: ...Charolais cross.
The dams were a mixture of purebred Angus and Hereford cows with ages varying from 2 to 7 years. Back

b. The length of gestation of the SDx was not significantly different from that of the Sx and Cx, but was longer than the HxA and shorter than the Lx. Back

c. Mean birth weights of the SDx and Lx were similar, but greater than those of the HxA and less than those of the Sx and Cx. Back

d. Calving difficulty experienced by the SDx was significantly greater than that experienced by the HxA, but similar to that of the Lx Sx and Cx. The amount of dystocia was a function of both birth weight and age of dam; in SDx, it was <10% in cows calving at 4 years of age or older. Back

e. Early mortality is defined as death of the calf within 24 hrs of birth. Early mortality in the SDx calves was similar to that of the Lx and Sx calves, but greater than that in the HxA and less than that in the Cx calves. It appeared to be related to dystocia alone. Back

f. Late mortality is defined as death of the calf from 24 hrs post-partum to weaning. Late mortality in the SDx calves was similar to that in the Lx and Sx calves, but greater than that in the HxA and less than that in the Cx calves. Back

g. The mean adjusted 200 day (weaning) weight of the SDx calves was similar to that of the HxA and Lx calves, but approximately 10Kg less than those of the Sx and Cx calves. While sire breed had an influence, so too did the breed and age of the dam, reaffirming the importance of maternal milk production. Back

h. Pre-weaning average daily gain (ADG) followed similar trends to the 200 day weight. Back

i. Pre-weaning relative growth rate (RGR) is defined as the percentage change in body weight per day, and is a measure of the rate at which the calf is maturing. It was highest in the HxA calves and although the SDx calves ranked next, the difference between them and the European crosses was not significant. Back

j. The post-weaning average daily gain (ADG) was highest in the Sx and Cx calves, with the SDx calves not far behind. The Lx and HxA calves had the lowest ADG and were not significantly different from one another. Back

k. Although the SDx calves had the highest post-weaning relative growth rate (RGR), it was not significantly different to that of the Cx calves. Both however were greater than the other crosses examined, with the Lx calves again having the lowest RGR. Back

l. The amount of fat present in the longissimus muscle is an objective measure of marbling. A level of 5% corresponds to the minimum required for the USDA choice grade. The SDx calves started to marble significantly earlier than the European cross calves, and not far behind the HxA calves. Back

m. See note (l). Back

n. At 15 months of age, the HxA steers weighed 453Kg, had a hot carcass weight (HCW) of 288Kg, and had 6.0% fat in the longissimus muscle. At both a similar age and carcass weight, the SDx steers had over 5%, an amount which was significantly greater than the European cross steers. Back

o. At similar age and carcass weights, the European cross steers had a larger mean eye muscle area, with that of the SDx steers being intermediate between them and the HxA steers. Back

p. The SDx steers had a subcutaneous fat thickness which was intermediate between that of the HxA and European cross steers. When, however, this was adjusted to the total fat content, the SDx steers displayed relatively less subcutaneous fat than all the other crosses. Back

q. Dressing percentage did not differ significantly among the sire breed groups. Back

r. At similar age and carcass weights, the European cross steers had a significantly higher retail yield than did the British cross steers, however the yield from the SDx steers was greater than that from the HxA steers. Back

s. SDx and HxA steer carcases were graded prime whereas those of the European cross steers were graded significantly lower. Back

t. Breed group means for marbling were closely correlated (r=0.96) with the means for fat percentage in the longissimus muscle (see note n). Back

u. The Warner-Bratzler shear test is an objective measurement of meat tenderness. Beef from the SDx steers was significantly more tender than that from the other crosses. Back

v. Subjective evaluation of tenderness by a taste panel yielded similar results to that of the Warner-Bratzler shear test, namely that the meat from SDx steers was significantly more tender than that from the other crosses. There were however no significant differences between the various groups in either flavour or juiciness. Back

w. SDx heifers reached puberty (defined as the date of first standing oestrus) earlier than any of the other crosses, and significantly earlier than the Lx and Cx heifers. When subsequently joined between 14 and 18 months of age, there was no significant effect of the sire breed on the percentage of pregnancies achieved. Back

x. HxA and SDx heifers were lightest at puberty, followed by Sx, Lx and Cx. Lx crosses reached a similar stage of sexual maturity at a later age and heavier weight relative to their rate of growth. Back

y. When having their second calf as a three year old, the birth weights of the calves from the SDx, Lx, Sx, and Cx cross cows were similar, but were heavier than those from HxA cows. Back

z. The mean length of gestation in three year old SDx and European cross cows was identical at 286 days, but was 2 days longer than that in the HxA cows. The length of gestation in heifer calves tended to be one day less than the mean, while that in bull calves tended to be one day longer. Back

aa. The amount of dystocia in three year old cross cows joined to another breed was similar in the various crosses with the exception of the Lx cross cows in whom it was significantly lower. The reason for this is not readily apparent, as dystocia was linearly dependent on birth weight, increasing by 1.5% for every Kg in excess of 32Kg. Back

bb. The overall mortality (birth to weaning) in calves from three year old cross cows was 8%, and did not differ significantly with the breed of the cow, although that in calves from SDx dams tended to be the lowest, whilst that in calves from Lx dams tended to be the highest. Back

cc. The pre-weaning average daily weight gain (ADG) of calves from three year old Sx cows was significantly greater than that in calves out of the other cross-bred cows. Back

dd. The estimated average milk production in three year old cows was significantly greater in the Sx cows than in the others. This, however, was largely due to an excessive amount of milk early in the lactation, as after five months the amount produced was not significantly different from that of the SDx cows, but was still greater than that of the other crosses. Back

ee. The post-weaning average daily weight gain of steer calves was not affected by the breed of the dam's sire. Back

ff. At 15 months of age, the cross-sectional area of the longissimus muscle of steers from SDx, Lx, Sx and Cx dams was similar, but significantly greater than that of steers out of HxA dams. Back

gg. Following slaughter at 15 months of age, steers of HxA dams had significantly more subcutaneous fat than steers from other cross-bred dams. Those from SDx and Lx dams had similar amounts of fat, but significantly more than than those from Sx and Cx dams. Back

hh. Following slaughter at 15 months of age, steers from SDx, Lx, Sx and Cx dams yielded a similar percentage of retail product which in turn was significantly greater than that of steers out of HxA dams. Back

ii. At 15 months of age, steers with British maternal grandsires tended to have better quality meat, although this difference did not reach statistical significance. Back

jj. At 15 months of age steers out of HxA dams had significantly more marbling than those out of Lx and Cx dams. Steers from SDx and Sx dams had intermediate levels of marbling. Back

kk. Heifers out of SDx and Sx dams tended to reach puberty (defined as the date of first standing oestrus) three to four weeks earlier than heifers out of other first-cross dams (ie. HxA, Lx and Cx dams). When joined at approximately fifteen months of age, heifers out of HxA, SDx, Sx and Cx dams achieved pregnancy rates of 90%, whereas those out of Lx dams managed only a 70% pregnancy rate (cf note (x)). Back

ll. Heifers out of HxA and SDx dams were lightest at puberty, followed by those out of Lx, Sx, and Cx dams. Back

References:

Smith GM, Laster DB, Gregory KE. Characterization of biological types of cattle: I. Dystocia and preweaning growth. J. Anim. Sci. 1976; 43:27-36.

Smith GM, Laster DB, Cundiff LV, Gregory KE. Characterization of biological types of cattle: II. Postweaning growth and feed efficiency of steers. J. Anim. Sci. 1976; 43:37-47.

Kock RM, Dikeman ME, Allen DM, May M, Crouse JD, Campion DR. Characterization of biological types of cattle: III. Carcass composition, quality amnd palatability. J. Anim. Sci. 1976; 43:48-62.

Laster DB, Smith GM, Gregory KE. Characterization of biological types of cattle: IV. Postweaning growth and puberty of heifers. J. Anim. Sci. 1976; 43:63-70.

Kock RM, Dikeman ME. Characterization of biological types of cattle: V. Carcass wholesale cut composition. J. Anim. Sci. 1977; 45:30-42.

Notter DR, Cundiff LV, Smith GM, Laster DB, Gregory KE. Characterization of biological types of cattle: VI. Transmitted and maternal effects on birth and survival traits in progeny of young cows. J. Anim. Sci. 1978;46:892-907.

Notter DR, Cundiff LV, Smith GM, Laster DB, Gregory KE. Characterization of biological types of cattle: VII. Milk production in young cows and transmitted and maternal effects on preweaning growth of progeny. J. Anim. Sci. 1978;46:908-921.

Young LD, Cundiff LV, Crouse JD, Smith GM, Gregory KE. Characterization of biological types of cattle: VIII. Postweaning growth and carcass traits of three-way cross steers. J. Anim. Sci. 1978;46:1178-1191.

Young LD, Laster DB, Cundiff LV, Smith GM, Gregory KE. Characterization of biological types of cattle: IX. Postweaning growth and puberty of three-breed cross heifers. J. Anim. Sci. 1978;47:843-852. Back