What if the sheep best suited to a hotter, harsher future are not wool sheep at all? This review shows why hair sheep are gaining ground, while also making clear that their advantages come with real trade-offs. Global warming, shrinking agricultural land for livestock farming, and an increasing human population create an urgent need for efficient and sustainable production of food animals.

At the same time, sheep agriculture is becoming more relevant, including through multi-species livestock farming and increased interest in mutton among ethnic populations in the United States. With the reduced competitiveness and value of wool, hair sheep have become the desired breed compared with wool sheep.

Hair sheep production has enormous potential for tropical and subtropical areas, including the Southern United States, because these resilient animals can overcome warm and humid climates. The advantages of hair sheep create a need for more transformative and translational research on economically important production traits.

Research results and anecdotal observations suggest significant advantages, but more evidence-based knowledge is needed to advance fundamental and applied hair sheep science. This review focuses on the basic and applied science of the most common hair sheep breeds.

The resource is intended to help students and scientists advance sheep science and help producers develop efficient and sustainable hair sheep farming. Hair sheep are expanding in relevance and in their place in United States animal agriculture, and approximately ten percent of all sheep globally are hair sheep.

The breeds are widely diverse, share a common origin in tropical countries, and were often crossed with wool breeds, namely Mouflon sheep, to improve economically important traits. That genetic development has been associated with advantages in carcass quality, meat taste, litter size, leather quality, parasitic resistance, disease resistance, heat tolerance, sperm quality, and nutritional efficiency.

The review also identifies disadvantages: average or below-average scrotal circumference, lower meat yield, higher meat cholesterol than wool breeds, and susceptibility to cold stress from the lack of wool. Figure one presents four hair sheep breeds—Katahdin, Barbados Blackbelly, St.

Croix, and Dorper—alongside a summary of their reported advantages and disadvantages. The advantages include parasite resistance, heat tolerance, carcass and meat quality, leather quality, litter size, nutritional efficiency, and sperm quality; the disadvantages include lower meat yield, cold-stress susceptibility, and other reported reproductive or meat-quality concerns.

This matters because hair sheep are increasingly relevant for efficient, sustainable food-animal production as wool becomes less competitive and environmental pressures grow. Hair sheep are more productive under low-quality fibrous diets. Santa Inês hair lambs were more efficient with increasing levels of low-quality diets than F one Ideal times Ile de France wool lambs.

Among hair sheep breeds fed moderate-quality feed such as alfalfa hay, different breeds had similar dry matter intake but different performance depending on their improvement. Katahdin did not express higher growth potential than St. Croix and Barbados Blackbelly lambs.

The relevant regions include areas where summer weather has high temperatures and extreme humidity. As the environmental temperature-humidity index increases, it becomes more difficult for animals to maintain a homeostatic temperature. Hair sheep notably have higher heat tolerance, but chronic heat stress remains a limiting factor in production.

Parasitic infestation is the number one cause of lost production and fertility in sheep farming. Haemonchus contortus is the main parasite of concern, and it is a nematode that feeds on the blood of its host. Infestation with this nematode causes anemia, diarrhea, and hypoproteinemia, while high infestation levels lead to high mortality levels.

Antiparasitic drugs can be effective, but they are costly and not guaranteed because anthelmintic resistance has grown globally. Compared with infected wool lambs, hair lambs infected with Haemonchus contortus have significantly higher production of immunoglobulin A. That higher immunoglobulin A production can be related to better immunity against parasite infection.

In one comparison of hair sheep, wool sheep, and crosses, wool sheep and crosses had significantly heavier carcasses, higher wholesale-cut weight, and greater loin-eye depth. Those wool sheep and crosses also had lower levels of back fat and cholesterol.

In a Mississippi comparison of Suffolk-sired lambs from Barbados Blackbelly ewes, Dorset ewes, and crosses, Barbados Blackbelly carcasses had a lower quality grade, lower leg score, and smaller loin-eye area. Table one compares Barbados Blackbelly ewes, BBB by Dorset crosses, and Dorset ewes exposed to Suffolk rams in Mississippi.

It reports ewes lambing, lambs born and weaned, plus average litter size at birth and at sixty days: for example, the values for BBB ewes are sixty-six ewes lambing, one hundred twelve lambs born, and one point six five lambs weaned per litter. These measures matter because preweaning performance and litter size are central to evaluating reproductive and meat-production potential in hair-sheep systems.

Compared with wool sheep, hair sheep have management advantages: they are easier to lamb, more prolific as expressed by lambing per year, and have higher survival of their lambs. Hair sheep also show more tolerance to heat stress than wool sheep, although they can still be affected by heat stress.

For meat production, hair sheep have higher cholesterol levels in meat and lower yield. Hair sheep have also shown higher resistance to parasite infections compared with wool animals. With these advantages, hair sheep are increasingly popular and likely to be included in farm operations.

More efficient, profitable, and sustainable hair sheep production requires more in-depth studies through rigorous multidisciplinary research using systems science. Hair sheep offer important advantages in heat tolerance, parasite resistance, management, and low-quality-diet performance, but lower carcass yield and other limitations remain.

Sustainable production therefore depends on targeted selection and rigorous multidisciplinary research.