Twenty first-calf heifers and 24 cows in their second or greater lactation were randomly assigned to 4 dietary treatments from day 15 to day 61 postpartum. Mixed diets consisted of corn silage, alfalfa haylage, orchard grass hay, and a pelleted concentrate. Concentrates were control (C), C + additional corn (H), C + 4% calcium stearate (S), or C + 4% tallow (T). C, S, and T contained 50:50 forage and concentrate dry matter and H contained 40:60. / Master of Science

These studies were conducted to define calf body shape, to test for relationships between calf shape and sire expected progeny differences for birth weight (BWTEPD) and first-calf calving ease (CEEPD) and to evaluate the efficacy of calf shape as a selection criterion for reduction of calving difficulty. Birth weight (BW), head circumference (HC), hip width (HW), shoulder width, body length (BL), cannon circumference (CC), cannon length (CL) and heart girth (HG) were measured at birth on 1,016 calves sired by Angus, Polled Hereford and Simmental bulls. In the Angus- and Polled Hereford-sired calves, sire effects were present for BW-adjusted residuals of CC. Additionally, HW, BL and HG residuals differed among half-sib groups for the Polled Hereford-sired calves. Thus, calf body measure differences independent of BW were in part attributable to sire. Multivariate factor analysis was used to identify underlying skeletal width and frame dimensions of calf shape in both breeds. After adjustment of body measures for differences in BW, a positive relationship of BWTEPD with HC and CC and a negative relationship between CEEPD and CC existed. Further adjustment for BWTEPD removed effects of CEEPD on CC. Thus, BWTEPD influenced calf shape independent of BW, but shape was not related to CEEPD independent of BWTEPD. Simmental bulls were divergently selected on CEEPD relative to BWTEPD so that body measures of calves from sires whose progeny tended to be born with more or with less dystocia than expected from BWTEPD could be obtained. Differences in CL and CC at constant BW were in part attributable to sire. Underlying shape factors were similar to those of the other breeds. Sire BWTEPD was positively related to CC and HC independent of BW. However, a relationship between body measures and CEEPD existed only at constant BW and BWTEPD. Calf shape independent of BW was also not different among calves born unassisted and assisted. Estimates of heritability, repeatability and birth to weaning relationships for each BW-residual body measure were generally not significant. Overall, sire BWTEPD was related to calf shape independent of BW. However, increases in skeletal dimensions were not related to either observed calving difficulty nor sire CEEPD independent of BW. Selection for reduced calving difficulty should not be based on calf body shape. / Ph. D.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 5 uppsatser.

No description available.

Variation among sires in daughters' reproductive performance was analyzed using data on 4,360 cows from nine herds obtained from the American Simmental Association. Cows were required to have at least 50% Simmental breeding, to have calved first at 2 yr of age and to have been born and subsequently calved in the same herd and season. Traits analyzed included first and second calving dates, first calving interval and the percentage of cows that returned to calve in the same season as 3-yr-olds. Data were adjusted for effects of percentage Simmental and first-calf calving ease score. At second calving, purebred Simmentals calved 1.7 ± 1.2 d later than 75% Simmental cattle and 5.1 ± 1.4 d later than 50% Simmental cattle. When compared to cows that calved without assistance at first calving, cows experiencing easy pulls were 1.7 ± 1.4% less likely to calve as 3-yr-olds and had 4.9 ± 1.0 d longer calving intervals. Cows with hard pulls were 9.0 ± 2.1% less likely to return and had 6.5 ± 1.6 d longer calving intervals. Cows requiring Cesarean section were 23.1± 2.5% less likely to return and had 19.6 ± 2.4 d longer calving intervals. Heritability estimates were .17 ± .04 for first calving date, .07 ± .06 for second calving date, .04:105 for calving interval and .11 ± .04 for percent return. Calving interval does not appear to be a useful selection criterion to improve reproduction. Phenotypic and genetic correlations of first calving date with calving interval were -.58 and -.83 ± .37, respectively. The genetic correlation between first and second calving dates was .66 ± .41. Given current data recording procedures, calving date appears to be the most useful potential selection criterion to improve reproductive fitness. / Master of Science

Call number: LD2668 .T4 1985 C34 / Master of Science

No description available.