Abstract
The objectives of this work were to evaluate the environmental effects (age of dam, type of birth and sex of lamb) and genetic groups (Hampshire Down and Ile de France, ½ and ¾ Hampshire Down, Ile de France and Suffolk, and ½ Texel) on performance and morphometric characteristics (height, length and heart girth) of lambs; to test regressions to predict live weight of lambs from body measurements; and to describe the growth type of the measurements as function of the weight. Weights and measurements were collected from birth to weaning, every 14 days. For evaluations of performance in relation to environmental effects and genetic groups, only data from birth and from weaning were used; for type of growth all collected data were used. Lambs from younger ewes (2 teeth) presented smaller average for weight at birth, heart girth and height at weaning. Single-birth lambs presented greater averages than twins. Genetic group influenced all traits evaluated, except heart girth at birth and average heart girth gain. Means for birth weight were higher in ¾ Ile de France (3.93±0.16 kg) and lower in ½ Texel lambs (3.04±0.24 kg), and for weaning, they were higher in ½ Texel (14.86±0.87 kg) and lower in Ile de France lambs (11.66±0.83 kg). Year of birth influenced all traits. Heart girth and length showed a negative allometric growth in relation to weight, while between weight and height the relation was positive allometric. The factors that most influenced the performance of lambs from birth to weaning are the type of birth, genetic group and year of birth. Correlations between body weight and morphometric measurements are significant, so it is possible to predict one from the other.
Highlights
Sheep farming has been developing in Brazil, mainly due to the growth of production and consumption of highquality sheep meat (Souza, 2008), which is considered an attractive source of income to farmers.In order to be a viable economical activity, sheep farming needs to provide the lambs with conditions to externalize the most of their genetic potential
Means for birth weight were higher in 3⁄4 Ile de France (3.93±0.16 kg) and lower in 1⁄2 Texel lambs (3.04±0.24 kg), and for weaning, they were higher in 1⁄2 Texel (14.86±0.87 kg) and lower in Ile de France lambs (11.66±0.83 kg)
The objective of this study was to investigate the influence of the year of birth, type of birth, sex of the offspring, genetic group and age of dam at lambing in relation to the weight and morphometric characteristics of the lambs at birth and at weaning (70 days of age); to test linear and allometric regressions to predict live weight by means of the morphometric measurements; and to describe the type of growth of the body measurements within the study period
Summary
Sheep farming has been developing in Brazil, mainly due to the growth of production and consumption of highquality sheep meat (Souza, 2008), which is considered an attractive source of income to farmers. In order to be a viable economical activity, sheep farming needs to provide the lambs with conditions to externalize the most of their genetic potential. It is important to know the components that affect the proper development of the animals and their production (Landim et al, 2007). Morphometric measurements are obtained, and have been used to evaluate performance, to characterize genetic groups and as a way of selection for animal breeding (Sowand & Sobola, 2008).
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