This study was conducted to determine the relationships among the
linear type traits of rump angle, rump width, rump length, rear legs
side view, rear legs position, rear legs rear view, tailhead, vulva
angle, mobility, pasterns, foot angle, and toes with reproductive
performance (days open and times bred) in Holstein cows and to develop
indices to predict reproductive performance from mathematical functions
of the anatomical traits. Two trials were conducted. The first trial
involved 7630 registered Holstein cows from Oregon and California. The
regression analysis (R²) showed only 1.1% of the variability of times
bred and 1.3% of the variability of days open was accounted for by the
rump and rear leg type traits.
In the second trial, 8155 Holstein cows, both registered and
grade, were analyzed using the linear type traits of rump angle, rump
width, rear legs side view, rear legs position, rear legs rear view
and foot angle.. Grade and registered cows were analyzed separately to
determine if differences in management between them would be reflected
in the statistical analysis. Evaluator, lactation number (parity),
season, geographic location, and the interaction of evaluator and
lactation number had a significant effect on most of the type traits and
the scorecard category (General Appearance, Mammary System, Dairy
Character and Body Capacity) scores examined. The effects of these
variables were statistically removed and the residuals of the type
traits were used in the final regression analysis. Using stepwise
regression analysis, several non-significant traits were omitted from
the final model. The analysis used days open and times bred as
dependent variables. Lactation number, mature equivalent milk, foot
angle, rump width and their respective quadratics were independent
variables, as were season calved and geographic location. The
regression analysis (R²) indicated that 5.3% of the variability in days
open and 4.7% of the variability in times bred in registered cows was
accounted for by the type traits, foot angle and rump width,
respectively, when the effects of season calved, geographic location,
lactation number and mature equivalent milk were included in the model.
For the grade cows the regression analysis (R²) indicated that 3.5% of
the variability in days open was accounted for by foot angle. None of
the type traits examined had a significant effect on times bred. This
study detected no significant influence of rump angle or rear leg position,
as described by the HFA linear classification program, on
reproductive performance. However, our analysis indicated that
fertility decreased as rear foot angles became more steep in grade and
registered cows and as rump width increased in registered cows. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37429 |
| Date | 20 December 1990 |
| Creators | Shapiro, Leland Sanford |
| Contributors | Swanson, Lloyd V. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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