Selection for components of efficient lean growth rate in pigs 1. Selection pressure applied and direct responses in a Large White herd

Abstract

Responses to four generations of divergent selection for lean groivth rate with ad-libitum feeding (LGA), for lean food conversion (LFC) and for daily food intake (DFI) in Large White pigs were studied. The LGA (LFC) selection criterion was designed to obtain equal correlated responses in growth rate (food conversion ratio) and carcass lean content, measured in phenotypic s.d. The selection criteria had phenotypic s.d. of 27, 29 and 253 units, respectively, and results are presented in s.d. units. There was a total of 3537 pigs, with an average of 40 boars and 40 gilts performance tested in each of the high, low and control lines per generation and the lines consisted of 10 sires and 20 dams. The generation interval was equal to 13-5 months. Animals were performance tested in individual pens with mean starting and finishing weights of 30 kg and 85 kg respectively.Cumulative selection differentials in the three selection groups were 5-8, 3-6 and 3-3 phenotypic s.d. for LGA, LFC and DFI respectively. Direct responses to divergent selection were 1-7, 1-3 and 1-2 (s.e. 0-17) for LGA, LFC and DFI. The correlated response in LFC (1-6 (s.e. 0-18)) with selection on LGA was greater than the direct response in LFC. Conversely, the direct response in LGA was greater than the correlated response (1-1 (s.e. 0-18)) with selection on LFC. The response in LFC (-1-1 (s.e. 0-17)) with selection on DFI was similar in size but opposite in sign to the direct response in LFC. Responses were asymmetric about the control, as the high LGA and LFC responses were proportionately smaller (0-74 and 0-58) than low line responses. In contrast, the difference between the high DFI and control was four times greater than the difference between low line and control. Heritabilities of LGA,, when estimated by residual maximum likelihood, with common environmental effects of 0-09 (s.e. 0-02). Genetic correlations for LGA with LFC and DFI were positive, 0-76 (s.e. 0-03) and 0-23 (s.e. 0-07), but the genetic correlation between DFI and LFC was negative,. The experiment demonstrated that substantial responses to selection can be achieved in LGA, LFC and DFI. Selection on LGA resulted in larger direct and correlated responses than selection on LFC.

Genetic parameters between slaughter pig efficiency and growth rate of different body tissues estimated by computed tomography in live boars of Landrace and Duroc

“…Nevertheless, the lean meat content can be predicted from ultrasound measurements of backfat and loin, which can then be used for the prediction of lean meat growth (PLMG). In studies of PLMG, heritability estimates range from 0.37 to 0.47 (Stern et al, 1993;Cameron, 1994;Chen et al, 2002). These estimates are in the range of our estimate for Duroc, whereas Cameron and Curran (1994) found a lower heritability (0.25) at the same magnitude as our estimate for Landrace.…”

Peri-partum posture and behaviour of gilts and the location of their piglets in lines selected for components of efficient lean growth

“…straw versus no straw by Cronin and Smith, 1992). One deficiency in the breed comparisons of peri-parturient behaviour of sows is that they generally lack a clear definition of the development processes which have led to the genetic differences in productivity between the breeds.Selection for different components of efficient lean growth rate has generated a set of well-defined genetic lines (Cameron, 1994). This study examines if the different selection strategies in these lines have affected the postures and behaviours of gilts and their piglets in a period commencing two hours before and lasting until two hours after farrowing.…”

A Polymorphism in the 5′-Untranslated Region of the Porcine Cholecystokinin Type A Receptor Gene Affects Feed Intake and Growth

“…For example, the A allele (for the 1179A/G and the 1471C/G SNPs) had been completely eliminated from the LFC low line with seven generations of selection, yet this allele was substantially higher in the LGA and LGS low lines than in their complementary selection lines. The selection objective of the LFC lines was to achieve equal correlated responses in carcass lean content and FCR, whereas the lean growth lines focused on carcass lean content and growth (Cameron 1994). Therefore, the CCKAR allele A may have a negative association with growth, which is supported by the association analyses in the other populations, but the B allele may negatively affect the ratio of feed conversion to lean mass in these lines.…”