Estimates of genetic and phenotypic parameters of growth and carcass traits from closed lines of pigs on restricted feeding

Abstract

Data from two selected lines of pigs in closed herds of a breeding company were collected over a 5-year period. The lines were selected for growth rate and leanness and were housed together in the same environment. Animals were performance tested from 35 kg for about 58 days, and were fed individually according to a scale determined by time on test; the boars were more liberally fed than the gilts. At the end of test, average daily gain (ADG) values were calculated and ultrasonic measures were taken of fat depths at the shoulder (SF), loin (LF) and last rib, 4-5 cm (CF) and 8 cm (KF) off the mid line.Estimates of heritabilities, phenotypic and genetic correlations were obtained from paternal half-sib analyses. All heritability estimates were significantly different from zero and ranged from 0-18 to 0-42 for ADG and from 0-21 to 0-59 for fat depths. The genetic correlations between ADG and fat measurements in boars of the two lines were not significantly different from zero, averaging 0-08; in the gilts they were negative, averaging -0-39.After long-term selection, appreciable genetic variation remained in the closed lines studied here for growth rate and fat depths. Although sex and feeding level were confounded, it is likely that the genetic correlation between growth rate and fat depth was influenced by the level of feeding and associated with partitioning of energy between lean and fat deposition.

Genetic parameters of production and reproduetive traits in on a farm tested Danish Large White and Landrace swine in Greece

“…The result about the age is not in agreement with other literature references where LW are generally reported to grow faster than Landrace pigs (GU et al, 1989, FERRAZ andJOHNSON, 1993;BIDANEL et al, 1994;DUCOS and BIDANEL, 1996). Furthermore, LD pigs are reported to be leaner (GU et al, 1989) or fatter at standardized liveweight (FERRAZ and JOHNSON, 1993;BIDANEL and DUCOS, 1996;DUCOS and BIDANEL, 1996) as in the present study. Since the animals of the present study were kept under the same environmental conditions the observed differences may reflect strain differences of the breeds used.…”

“…Reported heritabilities for these traits are in the ränge of 0.21 to 0.59 for LD and 0.21 to 0.53 for LW SAVOIE and MTNVIELLE, 1988;GU et al, 1989;KAPLON et al, 1991;HOVENIER et al, 1992;LO et al, 1992;BRYNER et al, 1992;BIDANEL et al, 1994;LI and KENNEDY, 1994;DUCOS and BIDANEL, 1996;BRANDT and TAEUBERT, 1998). Selection on production traits has proved to be efficient in both breeds.…”

Genetic parameters and responses of performance and body composition traits in pigs selected for high and low growth rate on a fixed ration over a set time

“…Levels of food restriction have been shown by others to influence the sign and magnitude of the genetic correlation between growth rate and backfat thickness [1,12,21]. At both the genetic and phenotypic levels, the correlations between TDG and TFC are close to minus one, reflecting a low variation (CV = 2.1%) between animals in food intake during the test.…”

Selection for components of efficient lean growth rate in pigs 3. Responses to selection with a restricted feeding regime

“…To test the hypotheses of Fowler et al (1976), Smith and Fowler (1978) argued for the establishment of a comprehensive selection experiment with lines selected for different criteria on ad-libitum or restricted feeding regimes and measurement of correlated responses on the alternative feeding regimes. Performance testing of pigs on a restricted feeding regime has been used by several breeding companies (Gu, Haley and Thompson, 1989;Crump, 1992). In the current experiment, the food restriction was intended to be 0-75 g/g of the mean ad-libitum food intake to limit variation in food intake, although the restriction will be relatively greater for some animals due to genetic variation in appetite.…”