A lamb is a young sheep, typically under one year of age. While the common perception is that lambs are white, based largely on commercial breeds, the true spectrum of coloration extends far beyond white. Lamb color encompasses a variety of natural hues and patterns determined by complex genetics and developmental factors.
The Predominant Coloration
The vast majority of lambs born worldwide are white, cream, or an off-white shade. This predominance results from centuries of selective breeding driven by the commercial wool industry. White wool is desired because the lack of natural pigment allows it to be easily dyed into any color, fetching a higher market price.
Commercial breeds, such as the Merino and the Suffolk, have been intentionally bred for this trait. The white coat color is genetically dominant in most modern domestic sheep populations, making it the standard and most frequently observed color.
Understanding Non-White Lambs
While white dominates the commercial landscape, lambs naturally display a wide range of colors, including black, brown, gray, and various spotted patterns. These colored lambs are biologically normal but are less common due to the selection pressure for white wool. Color is often associated with specialized or heritage breeds that have maintained a broader genetic palette.
“Colored wool” includes a spectrum of shades beyond pure black. Brown ranges from light tan, called “moorit,” to deep chocolate, while gray results from a mix of black and white fibers. Breeds like the Navajo-Churro and the Shetland sheep exhibit this natural diversity. These colors are valued by niche textile markets because they do not require dyeing.
Genetic Factors Determining Coat Hue
The color of a lamb’s coat is governed by specific genetic locations, or loci, primarily the Agouti and Extension loci. The Agouti locus controls the pattern of pigmentation, determining whether the color is distributed evenly or restricted. The most dominant allele at the Agouti locus results in a white or near-white coat, explaining why commercial breeds are predominantly unpigmented.
The Extension locus influences the expression of pigment-producing cells, controlling the base color of the wool. All sheep are technically either black (eumelanin) or brown (phaeomelanin) underneath the dominant white Agouti gene. The dominant white allele suppresses the expression of these pigment genes in the wool fibers, resulting in a white coat even if color genes are present.
When a lamb inherits the recessive alleles at the Agouti locus, the underlying black or brown pigment is expressed, leading to a colored coat. The Brown (B) locus then determines whether that expressed pigment is black (dominant) or the recessive brown, often called moorit.
Changes in Wool Color Over Time
A lamb’s initial coat color is not always permanent and can change significantly as the animal matures. One common change is the fading of dark wool, particularly on the tips of fibers exposed to sunlight. This process, called “tipping” or bleaching, causes the outer layer of a black or brown fleece to lighten over the first few months.
Conversely, some lambs born with lighter coats may develop darker wool as they age. For instance, gray or speckled lambs may show an increase in dark fibers as pigment-controlling genes fully express themselves. Certain heritage breeds, like the Navajo-Churro, are often born with a reddish or tan coat that transitions to white or cream after the first shearing. These age-related color shifts are a normal part of the sheep’s physiological maturation.