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Effects of Energy and Dry Matter Intake on Age, Body Weight and Backfat at Puberty and on Embryo Mortality in Gilts^1,2,

Animal Research Centre, Research Branch, Agriculture Canada, Ottawa, Ontario, Canada K1A 0C6

Abstract

In the first of two experiments, a previous comparison of the effects of ad libitum and limited feeding on age at puberty was reexamined. Fifteen littermate pairs of Yorkshire gilts 113 to 122 days of age were fed the same diet. Detection of estrus in each gilt was confirmed by breeding with a boar, and the gilt was killed 30 ± 2 days later. Ovaries were examined for corpora lutea, and the uterus for embryos. Gilts fed ad libitum were younger (P<.05) and heavier at puberty (159 vs 170 days and 97 vs 92 kg) than those limit-fed, which confirmed the previous results. In the second experiment, one group (H) of 10 prepuberal gilts was fed ad libitum a high energy diet, another group (L) a low energy diet at the same daily dry matter intake as group H and the third group (HL) the high energy diet at the same daily energy intake as group L. Ultrasonic backfat probes were taken at 70 kg body weight, at 135 days of age and when gilts were bred at puberty; gilts were killed 30 ± 2 days later. At puberty, the largest differences in mean age (156 vs 166 days) between the HL and L gilts, and in mean body weight (92 vss 99 kg) between the HL and H gilts, were not significant. Depth of back-fat at the standard age and body weight was not related to age at puberty, indicating that selection for early puberty would not result in increased carcass fat content. Embryonic mortality was 18 and 21% for ad libitum and limit-fed gilts, respectively, in the first experiment, and 19, 25 and 31% for H, HL and L gilts in the second.

¹ Animal Research Centre, Contribution No. 947.

² The authors wish to acknowledge the assistance of Rick Robinson (Food Production and Inspection Branch, Agriculture Canada, Ottawa) with ultrasonic probe procedures.

³ Present address: School of Agriculture, 581 King Street, Aberdeen, Scotland AB9 1UD.