Growth and body composition changes in mice selected for high post-weaning weight gain on two levels of feeding

Abstract

Two lines of mice were selected for high post-weaning weight gain (3 to 6 weeks) adjusted for 3 week weight. One line (F) was grown on freely available food and the other (S) on a feeding scale set at the same level for all mice. Food intake of the S line averaged 80% of the F line. The realised heritabilities after 6 generations of selection were 0.38±0.06 and 0.33±0.07 for the F and S lines, respectively. In generation 7, mice from the F and S lines and from an unselected control line (C) were compared on both free and set levels of feeding from 3 weeks to 9 weeks of age. Measurements taken were growth rate, appetite, food conversion efficiency (weight gain/food intake) and body composition (fat, protein, ash, water). The F and S lines grew more rapidly and efficiently than the C line on both levels of feeding, each line performing best on the level of feeding on which it was selected. The average genetic correlation between growth rates of the same line on the two feeding levels was 0.54±0.10. The F line grew 19% faster and was 9% more efficient than the S line on free feeding but the S line grew 15% faster and was 15% more efficient than the F line on set feeding. Relative to the C line, food intake per day on free feeding was 4% higher in the F line and 6% lower in the S line. There was no difference between the lines in food intake/g body weight. The rate of deposition of all body components increased in both selection lines. In the F, S and C lines respectively, efficiencies of gains in body components (10(2)x gain/food) were 1.79, 1.31 and 1.06 for fat, 1.53, 1.63 and 1.22 for protein and 5.88, 6.45 and 4.98 for protein + water. Apparently energy lost as heat was reduced in both the F and S lines. The partitioning of energy retained was altered in favour of more fat in the F line and more protein in the S line.

Genetic parameters and effect of selection for body weight in lines of mink (Neovison vison) on ad libitum and restricted feeding

“…The heritabilities estimated for weight (Table II) were in the order of those found by N'Drie et al (2007) in poultry and by Lagerkvist et al (1994) and Hansen and Berg (1997) in mink, but larger than those observed by McPhee and Trappett (1987) and Urrutia and Hayes (1988a) in mice and by Cameron (1994), , , and Nguyen and McPhee (2005a, b) in pigs. The reported heritability of 0.19 for animal size in mink (Koivula et al, 2011) is considerably smaller than the above reported heritability estimates for weight in mink.…”

“…This includes selection for growth, feed intake, or feed conversion ratio on ad libitum (AL) or restricted feeding (RF). Experiments have been performed with mice, pigs, and poultry (Sutherland et al, 1970;Pym & Nicholls, 1979;Hetzel & Nicholas, 1986;McPhee & Trappett, 1987;Cameron, 1994;Nguyen & McPhee, 2005a). Selection for growth on AL feeding is usually associated with increased feed intake and a reduced feed conversion ratio.…”

Selection in pigs for increased lean growth rate on a time-based feeding scale

“…If Hammond's (1947) performance testing method, which was a view that the regimen should give fullest modification of one proposed by Kielanowski expression to the trait is accepted, then ad (1968). Evidence in support of this expectation was found in the pig and mouse work of Falconer and Latyszewski (1952), Fowler and Ensminger (1960), Hetzel and Nicholas (1986) and McPhee and Trappett (1987). However, studies on performance test of set duration and food intake.…”

“…for GR and F respectively. In mouse lines selected for increased body-weight gain on a fixed feeding scale, McPhee, Trappett, Neill and Duncalfe (1980), Hetzel and Nicholas (1986) and McPhee and Trappett (1987) attributed the response to a reduction in the energy used for maintenance and, to a lesser degree, an improvement in the use of retained energy through an increased lean and reduced fat deposition. respectively.…”

Effect of selection for growth on normal and reduced protein diets on weight gain, feed intake, feed efficiency and body composition in mice

“…Selection has been performed for growth on diets differing in quantity, such as ad libitum and restricted feeding (Falconer & Latyszewski 1952; Park et al. 1966; Hetzel & Nicholas 1986; McPhee & Trappett 1987; Urrutia & Hayes 1988), or in quality, such as diluted (Falconer 1960) or low‐protein diets (Park et al. 1966).…”