In the goat world, you're likely to hear a lot about copper and selenium, but there is one important mineral that I think needs more attention - zinc. I've touched on it in a few previous posts on goat nutrition because of its relationship with copper, but here is some more information about this important mineral, just in time for breeding season.
Current zinc recommendations are a minimum daily intake of 10ppm, with 45-50ppm being the requirement in a standard diet and 75ppm in diets with serious antagonists. There are no specific toxicity rates for goats, but a single dose of 1000ppm is toxic to sheep. According to a national forage study with over 300 samples from 18 states, most forages were deficient in zinc. https://newprairiepress.org/cgi/viewcontent.cgi... Hay usually has lower zinc levels than forages (4). This means a good mineral supplement is often needed to meet zinc requirements.
Little zinc is stored in the body in a readily-available form so it is best consumed daily. Absorption is highly variable. "The Agricultural Research Council proposed an absorption coefficient of 50% for pre-ruminants on milk diet, 30% for growing ruminants, and 20% for adult ruminants. However, NRC suggested a more conservative 15% for more practical cases." – Nutrient Requirements of Small Ruminants p 138. Male goats, especially bucks, often require more dietary zinc than females, especially non-lactating females. Studies have shown zinc supplementation to bucks improves semen quality and quantity because zinc is essential to spermatogenesis (5).
An older paper from the Journal of Dairy Science asserts that zinc deficient bucks skewed the sex ratio of kids in favor of females and also resulted in dwarfism in male kids (6).
Sulfur, calcium, and copper are important zinc antagonists. Cadmium, iron, and selenium influence absorption as well but likely to a lesser degree. Copper and calcium seem to be especially important antagonists. A proposed ideal ratio of zinc to copper is 4:1(2, 3).
Recently, research has also indicated that goats can exhibit zinc deficiency caused by genetics alone and might need additional oral zinc supplementation (1). Zinc can be supplemented in the form of loose minerals, lozenges, or capsules/pills. Dietary zinc deficiency might be alleviated quickly by supplementation – studies and anecdotal evidence have shown improvement in a week – but any causes (high calcium for instance) need addressed or the problem will reoccur (2). However, “goats with suspected hereditary malabsorption of zinc required 1 to 3 months [of supplementation] for complete resolution” – Sheep, Goat, and Cervid Medicine pg 238. Zinc deficiency symptoms include: - Dermatitis that is responsive to zinc supplementation - Stiffness in limbs - Hair loss, especially on the back, legs, and face. - Weeping eyes - Small testes and reduced libido in bucks - Hoof deformities, especially flaking, soft hooves
- Diminished growth in kids
- Lack of appetite On a personal note, I've dealt with some mild, temporary cases of zinc deficiency in bucks. The symptoms included dry skin, flaking hooves, and weeping eyes - all mild but noticeable. The problems corrected with 50mg additional zinc per day for a week or so. The worst case I've dealt with was a registered Pygmy buck who had been given copious amounts of copper since his tail was a "fishtail." As discussed in the previous nutritional posts on copper, there is no actual evidence fishtail is ONLY from a copper DEFICIENCY. In this particular case, the buck had a very low libido - literally would not breed a doe - weeping eyes, flaking hooves, missing hair, and dry skin. After he was brought home, he was given a thorough examination while in quarantine. His hooves were overgrown, especially in the rear, and the sparse tail was actually caused from him backing up to fences to scratch his rump because he was harboring biting lice. He was treated and trimmed and eventually was ready for the following breeding season. Or so I thought. During this time, I was still using a mineral that had less than a 4:1 Zn:Cu ratio. While he initially was enthusiastic about breeding season, the buck's libido was very low. He wouldn't actually breed a doe. After much research and learning about the zinc to copper ratio and zinc in general, I switched minerals and began supplementing zinc. The difference was remarkable. He went on to service several does and produce some very cute, chunky offspring. It was interesting to point out that he sired a total of 7 doelings and 3 bucklings - two sets of twins, one set of triplets, and three singles, so perhaps, if that older research holds true, he was still a bit zinc deficient since he sired a higher percentage of doelings. Now, his breeder was a reputable breeder who, while temporarily overwhelmed for personal reasons, had let some things go unnoticed like the hooves and lice. But as far as minerals, the breeder was just one of many many folks who did/does not know any better than to see a "fishtail" and try to treat that according to popular internet and laymen wisdom. That's why I encourage each and every breeder to seriously consider their learning sources, learn about the functions of minerals and their relationships, and at least have an idea of what minerals in what quantities your goats are intaking. If you can, get mineral panels done on forage, hay, water, and tissue samples. The more information you have and the more tools you utilize, the better you can care for your goats. Happy breeding season!
Sources:
1. Zinc-responsive dermatosis in goats suggestive of hereditary malabsorption: two field cases. Krametter-Froetscher R, et al. Vet Dermatol. 2005.
2. Smith, M., Sherman, D. and Smith., 2009. Goat Medicine. 2nd ed. Somerset: Wiley.
3. Baird, N. (Nickie), and Pugh, David G.. Sheep & Goat Medicine - E-Book. United Kingdom, Elsevier Health Sciences, 2012.
4. NRC, 2007. Nutrient requirements of small ruminants: Sheep, goats, cervids, and new world camelids. National Academy Press
5. Neathery, M. W., Miller, W. J., Blackmon, D. M., Pate, F. M., & Gentry, R. P. (1973). Effects of Long Term Zinc Deficiency on Feed Utilization, Reproductive Characteristics, and Hair Growth in the Sexually Mature Male Goat. Journal of Dairy Science, 56(1), 98–105. https://doi.org/10.3168/jds.s0022-0302(73)85121-5
6. Haenlein, G. F. W. (1980). Mineral Nutrition of Goats. Journal of Dairy Science, 63(10), 1729–1748. https://doi.org/10.3168/jds.s0022-0302(80)83133-x
7. Corah, L.; Dargatz, D.; and Peters, C. (1996) "National forage survey results: trace mineral and related nutrient levels," Kansas Agricultural Experiment Station Research Reports: Vol. 0: Iss. 1. https://doi.org/ 10.4148/2378-5977.2011