Date of Award

1981

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

Data from the Southern Regional Dairy Cattle Breeding project (S-49) were analyzed by least square methods to evaluate genetic and environmental effects upon body weight and body weight gain. Data consisted of records on 1,352 purebred Ayrshire (A), Brown Swiss (S), Holstein (H) and Jersey (J) and 1,224 crossbred females. Sixty-one different major breed combinations were represented. Breed groups (PLB) represented proportion of a large breed (Brown Swiss and Holstein). According to this classification, six PLB groups existed at USDA, ARC, Beltsville, Maryland, four at Iberia Livestock Experimental Station, Jeanerette and eight at Georgia Coastal Plains Experimental Station, State Prison Farm, Reidsville, Georgia. Six linear body measurements were studied at 6, 12, 18 and 30 months of age at Beltsville and 6, 12, 18 and 24 months of age at Jeanerette. Linear measurements (cm) were wither height (WH), forechest depth (FCD), forechest girth (FCG), length from withers to pins (LWP), length from withers to hips (LWH) and length from hips to pins (LHP). Body weights were taken at birth and at 3-month intervals up to 21 months of age at Reidsville and up to 42 months at Beltsville and Jeanerette. Heterosis for body weight based upon overall mean of reciprocals (A x H, H x A, H x S, S x H, S x A and A x S) were 1.69% at birth, 4.68% at 6 months, 4.44% at 12 months, 5.90% at 18 months and 3.67% at 30 months for Beltsville. At Beltsville heterosis for linear body measurements ranged from 1.33% to 3.07% at 6 months, 0.58% to 1.45% at 12 months, 1.13% to 1.85% at 18 months and from 0.28% to 1.51% at 30 months of age. Birth weight (kg) least squares means and standard errors for PLB breed groups 0, 0.375, 0.5, 0.75, 0.875 and 1 were: 34.5 (+OR-) 0.7, 34.0 (+OR-) 1.1, 38.3 (+OR-) 0.6, 40.0 (+OR-) 0.7, 40.7 (+OR-) 1.3 and 39.6 (+OR-) 0.6. Body weight (kg) least squares means and standard errors at 15 months of age were: 308.7 (+OR-) 4.7, 341.4 (+OR-) 9.6, 347.0 (+OR-) 4.4, 365.1 (+OR-) 5.0, 371.4 (+OR-) 11.0 and 359.1 (+OR-) 3.8 at Beltsville. At Jeanerette, breed groups (PLB = 1) surpassed PLB = 0.5, PLB = 0.75 and PLB = 0.875 groups at all ages for linear body measurements and body weight. Birth weight (kg) least squares means and standard errors for PLB breed groups 0.5, 0.75, 0.875 and 1 were: 31.1 (+OR-) 0.9, 35.0 (+OR-) 0.9, 37.6 (+OR-) 1.3 and 36.1 (+OR-) 0.6. Body weight (kg) least squares means and standard errors at 15 months of age were: 263.4 (+OR-) 4.3, 278.4 (+OR-) 4.3, 281.0 (+OR-) 6.3 and 288.7 (+OR-) 3.4. Body weight (kg) taken at birth, 6, 12 and 18 months of age at Reidsville indicated that females of PLB group 1 were significantly heavier (P < .01) than other PLB groups. The difference in weight between the PLB = 1 and PLB = 0 groups was approximately 40% at birth and 27% at 18 months of age. Birth weight (kg) least squares means and standard errors for PLB groups 0, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875 and 1 were: 23.4 (+OR-) 0.2, 27.9 (+OR-) 0.5, 29.9 (+OR-) 0.6, 30.8 (+OR-) 0.3, 31.8 (+OR-) 0.8, 34.6 (+OR-) 0.4, 35.9 (+OR-) 0.5 and 38.5 (+OR-) 0.2. Body weight (kg) least squares means and standard errors at 15 months of age were: 224.3 (+OR-) 1.8, 246.2 (+OR-) 3.0, 268.6 (+OR-) 4.3, 273.7 (+OR-) 2.2, 277.7 (+OR-) 5.0, 292.2 (+OR-) 2.5, 298.8 (+OR-) 3.5 and 299.9 (+OR-) 1.6 at Reidsville. The major cause of variation was due to PLB group size for all three stations. Pooled data (Jeanerette and Reidsville) analysis indicated that year by season interaction effects were significant (P < .01) for all traits except weight at 3 months. Phenotypic correlations among body weight at different ages ranged from 0.573 to 0.902 at Reidsville.

Pages

163

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