Foreword: Mycotoxins are ubiquitous in dairy feed (including concentrates and crude materials). The growth of mold not only destroys the nutrients of the grain, but also produces secondary metabolites that are highly toxic to animals, humans and plants. That is, mycotoxins. Mycotoxins enter the cows to produce biological effects that affect the health and performance of the cows. Mycotoxin damage to cows includes organ damage (liver, kidney), immunosuppression (postpartum disease and mastitis), decreased feed intake, reduced feed conversion, and low reproductive rate (abortion, embryo death, wig, etc.). In addition, mixed infections of various mycotoxins and various stresses can enhance the toxic effects of mycotoxins, causing serious health problems in animals and reducing production performance, while high-yield livestock and fast-growing animals are more sensitive to mycotoxins, which affects economic returns. One of the important reasons, therefore the control of mycotoxins in feed is crucial.
Production of mycotoxins in dairy cow feed
Grains can be infected with mold during the process of growing, harvesting, storing, processing and feeding in the field, leading to the production of mycotoxins. Mold spores are abundant in the environment, and when the grain grows in the field, it is infected with mold, which leads to reduced yield, reduced quality and mycotoxin contamination. There are three main types of molds that produce mycotoxins: Aspergillus, Fusarium and Penicillium. There are at least 400 mycotoxins. The main factors affecting dairy cows are aflatoxin, zearalenone (ZON), vomiting toxin (DON), T-2 toxin, fumarine, ochratoxin (OTA) and tobacco. Aspergillus toxin (FUM). Mycotoxins may cause problems such as acute herd disease and decreased performance, but more commonly they can cause chronic problems such as increased morbidity, reduced reproductive performance, and inability to achieve optimal milk production. Mycotoxins have a negative impact on dairy cows through the following four aspects: first, cows produce no-feed or dry matter intake; second, reduce nutrient absorption and disrupt the body's normal metabolic processes; third, change the endocrine system; Fourth, suppress the immune system.
The effects of mycotoxins on dairy cows are as follows:
Effects of different mycotoxins on dairy cows
Aflatoxin is a group of compounds produced by Aspergillus that are extremely toxic and also have mutagenic and strong carcinogenic effects. The US FDA stipulates that cow feed should not exceed 20 ppb and milk should not exceed 0.5 ppb. In general, the concentration of aflatoxin in milk is 1.7% of the dry matter concentration of the diet. In Europe, the feed for lactating cows should not exceed 20 ppb and the milk should not exceed 0.05 ppb. Therefore, according to European regulations, if the aflatoxin in the dry matter of dairy cows exceeds 3 ppb, the aflatoxin in the milk may exceed the standard. Symptoms of mammalian aflatoxin poisoning include: depression, ataxia, gross coat, enlarged liver, paleness, etc. Subclinical poisoning will show reduced feed efficiency and milk production, jaundice, loss of appetite, etc. (Nibbelink,
1986). A cow's diet aflatoxin over 0.7 ppm may affect the health and performance of the herd (Patterson and Anderson 1982 and Masri et al. 1969). Guthrie (1979) reported that when cows fed a diet containing aflatoxin more than 0.12 ppm, their reproductive performance and yield decreased. When the diet was changed to aflatoxin-free diet, milk production increased by 25%. Aflatoxins are generally found in corn and cottonseed.
Vomiting toxins are produced by Fusarium and are the most commonly detected toxins in feed. Vomiting toxins have a major impact on pigs. For dairy cows, data show that vomiting toxins are associated with decreased performance in dairy cows, but the exact quantitative model has not yet been established (Whitlow et al., 1994). Diaz et al (2001) showed that when the cow diet contains vomiting toxin (2.5ppm), the yield is reduced by 1.5kg/head. days compared to the addition of the mycotoxin adsorbent, which provides indirect supply of vomiting toxins to affect milk production. The evidence. A study by Charmley et al. (1993) showed that milk production in dairy cows fed a diet with vomiting toxin levels of 2.6 to 6.5 ppm decreased (1.5 kg, P < 0.16). However, in many studies, the addition of purified vomiting toxins to the diet did not have as much effect on the naturally occurring vomiting toxins as cows, which may be due to the synergy of several mycotoxins in nature. Vomiting toxins can be used as a marker for dietary mold contamination, as long as there is vomiting toxins, it may indicate that the diet is contaminated with a variety of mycotoxins.
T-2 toxins can cause a decrease in feed intake and yield in dairy cows, gastroenteritis, small bowel bleeding, decreased reproductive performance, and even death. (Petrie et al., 1977; Mirocha et al., 1976). Cows fed a diet containing 0.64 ppm of T-2 toxin for 20 days can cause bloody stools, enteritis, true stomach and rumen ulcers, and even death (Petrie et al., 1977; Mirocha et al., 1976). Gentry et al. (1984) found that T-2 toxins reduced the number of white blood cells and phagocytic neutrophils, suggesting that it inhibits immunity, and studies by McLaughlin et al. (1977) showed that T-2 toxin suppresses immunity mainly because it can Inhibition of protein synthesis.
Zearalenone is an estrogen-like compound produced by Fusarium that produces a hormone-like effect on animals. Zearalenone is mainly found in corn ear, decayed corn stover and wheat plants with leaf spot disease. In one study, bred cattle fed 250 mg of zearalenone reduced the conception rate of bred cattle by 25% (Weaver et al., 1986a). Many studies have shown that zearalenone has an estrogen effect on ruminants leading to miscarriage (Kellela and Ettala, 1984, Hamis et al, 1986, Mirocha et al, 1968, Mirocha et al, 1974, and Roine et al, 1971). Mixed infections of 0.66 ppm zearalenone and 0.44 ppm vomiting toxin in the field trials resulted in reduced feed intake, decreased milk production, diarrhea, reproductive tract infections, and reproductive failure (Coppock et al., 1990). A New Zealand study has shown that zearalenone, which can cause reproductive failure in dairy cows, should be around 0.44 pp.
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