Calving difficulty (CD) records (0 = no difficulty, 1 = difficult calving) were collected over a 10-yeax period from 1987 to 1996 from a dairy herd used to develop two genetic lines of Holstein-Friesian (F) cows differing in mature live weight (LW). Cows from the base herd (B, n = 157), the heavy (H, n = 53), and light (L, n = 49) LW selection lines provided 508, 110, and 101 calvin° records, respectively. Nationally evaluated across breeds, the average breeding values (BV’s) for LW were 41.3 kg (B), 18.5 kg (L), and 92.5 kg (H), for maternal grandsires (MGS), and 47.4 kg (B), 32.1 kg (L), and 87.3 kg (H) for sires. Stepwise logistic regression was used for variable selection and to estimate the regression coefficients and odds ratio (OR) of variables related to CD. Variables considered were calf sex, parity, age, genetic line, sire of calf breed, an index for farm profitability termed “Breeding Worth” (BW), and the BV’s for production traits and traits other than production (TOP) for sires and MGS. Primiparous (n - 229 calvinsts) and multiparous (n = 490 calvings) cows were analysed separately. There was no effect of genetic line (H or L) on CD of primiparous or multiparous cows. For primiparous cows calves were more difficult to deliver if i) sired by F than by Jersey (J) bulls (P < 0.05; OR = 2 3) ii) if they were males (P < 0.005; OR = 2.7), or iii) if their MGS BV for rump angle was one standard deviation (SD) below average (P < 0.005; OR = 1.5). For multiparous cows, males were only marginally (P < 0.11; OR = 1.7) more difficult to deliver than females. Calves were more difficult to deliver if calved by younger cows (P < 0.005; OR - 1.6), sired by bulls with BW one SD below average (P < 0.05; OR = 1.5), or if from bulls with BV for rump width one SD above average (P < 0.01; OR = 1.4).
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 25: Lactation; growth and efficiency; meat quality; role of exotic breeds in the tropics; design of village breeding programmes;, , 39–42, 1998
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