The Effect of Anthelmintic Treatment in Adult Dairy Cows on Milk Production

The Effect of Anthelmintic Treatment in Adult Dairy Cows on Milk Production Page 1 of 8 More Information About This Topic From Merial: IVOMEC EPRINEX (eprinomectin) Pour-On for Beef and Dairy Cattle: A Revolutionary Design in Parasite Control J.M. Bicknese Merial Veterinary Bulletin TSB-9-99064-FTB No Product is Better for Parasite Control: IVOMEC EPRINEX Pour- On for Beef and Dairy Cattle J.M. Bicknese Merial Veterinary Bulletin TSB-0-00030-FTB TSB-9-99031- FTB IVOMEC and EPRINEX are registered trademarks of Merial. DECTOMAX is a registered The Effect of Anthelmintic Treatment in Adult Dairy Cows on Milk Production Duane E. Maye, DVM A Scientific Review The Bottom Line! Virtually all cattle on pasture are infected with parasites, usually Ostertagia ostertagi and Cooperia spp.! Cattle infected with parasites produce less milk.! When cows or heifers infected with parasites were treated with an effective anthelmintic, milk production increased by an average of 1.39 lb liquid milk per day (P<0.01). Introduction The presence of parasites in grazing calves and adult beef cattle is well established and recognized among the agriculture community. But what about adult dairy cows? As cattle mature and are exposed to parasite challenge while grazing, the effect of infection is reduced.(1,2) Thus, calves are more susceptible to the adverse effects of parasitism than are yearlings, and yearlings are more susceptible than adults.adult dairy cattle on a good nutritional program usually have some degree of immunity to parasites.(1) However, research has shown that the immunity of adult dairy cows to parasites can be lowered during periods of stress, including sickness, poor nutrition, pregnancy and lactation.(1,2) This interference with host defenses can lead to clinical disease or productivity losses related to subclinical infection.(3) The impact of gastrointestinal parasitism and anthelmintic treatment on milk production in dairy cattle has been extensively reported. Cows on Pasture and in Confinement Have Parasites Published reports of slaughter house surveys of culled dairy cows, fecal egg counts in lactating cows, serological tests, and worm counts in cull cows

The Effect of Anthelmintic Treatment in Adult Dairy Cows on Milk Production Page 2 of 8 g trademark of Pfizer Inc. CYDECTIN is a registered trademark of American Cynamid Company. 1999 Merial Limited. All rights reserved. from milk production studies have demonstrated that grazing dairy cattle are usually infected with Ostertagia ostertagi and Cooperia spp, with worm burdens often up into the thousands up to 225,500.(4-12) The seasonal fluctuations in populations of inhibited O ostertagi in these adult dairy cows are similar to those seen in young cattle.(4,7,11,13) Recently, a survey was conducted in New York, Pennsylvania, Wisconsin, and Minnesota to determine the prevalence of nematode eggs in their feces. (14) At least one animal on 108 of the 141 farms in the survey (77%) was positive for nematode eggs in the feces. The most common parasites found were Ostertagia, Cooperia, and Haemonchus. Cows and heifers in this survey were kept on pasture or in confinement. Of the cows on pasture, 46% had nematode eggs in the feces; 37% of the cows maintained in confinement had nematode eggs present in their feces. Keys to Productivity Losses The effect of gastrointestinal parasitism on dairy cattle can include appetite suppression, reduced feed digestibility, disruption of protein metabolism, interference with water and electrolyte balance, intestinal stasis, and a local hypersensitivity response at the site of infection.(3,15) Appetite Suppression Appetite suppression may be the single most important factor related to productivity losses in both dairy and beef cattle. In one study, anorexia caused by O ostertagi accounted for a weight gain difference of 73% between parasitized and non-parasitized calves.(15) In sheep, inappetence accounted for over 60% of the reduced weight gain in infected lambs, relative to parasite-free controls.(15) The reduction in appetite may result from increased gastrin levels associated with the elevated abomasal ph, consequent to parietal cells damage.(15,16) Thus, it appears the indirect effect of lower feed intake is far more important than the direct effect of physical damage on poor growth rate in parasitized animals. Feed Digestibility Reduction The digestibility of feed is expected to decrease in cattle infected with gastrointestinal parasites due to the damage caused by these parasites in the gut. Heinemann reported that a yearling steer infected with parasites demonstrated significantly (P<0.01) lower forage dry matter digestion than an uninfected animal.(17) The dry matter digestibility of high quality forage declined from 48.3% to 31.2% (a 35% reduction) when the steer was infected with nematodes. In lower quality forages, the decline in digestibility was even greater, from 25.9% to 12.2% a 53% reduction (P<0.01). The digestibility of protein followed the same pattern, with both high and low quality forages when cattle were infected with nematodes. Regardless of parasite status, cows in early lactation have total energy expenditure that is greater than energy intake.(18) Milk yield in postcalving dairy cows is closely correlated with energy balance.(1) Any reduction in appetite and/or forage digestibility in lactating dairy cows

The Effect of Anthelmintic Treatment in Adult Dairy Cows on Milk Production Page 3 of 8 would likely have an impact on milk production because nutrients are first used for maintenance. It seems that the effects of parasite treatment are greatest during the peri-parturient period.(1) The body condition of cows at calving may also have an impact on subsequent milk production because body fat reserves are a source of energy for the lactating cow.(1) The Effect of Parasites on Milk Production In reviewing the literature, 6 of 9 studies all utilizing experimental nematode infections demonstrated a negative impact of parasite infection on milk production.(19) In four separate trials conducted by Bliss, et al, cows averaging 39, 33, 73, or 134 days of lactation were each given 200,000 infective larvae of mixed nematode species, for up to three days. (20) In these four trials, uninfected cattle produced 2.2 to 6.5 lb more milk per day than did infected cows for the 30 days following infection. These results are similar to those reported by Barger and Gibbs, in which cows in week 4 of lactation were infected with a mixture of 5,000 infective larvae three times weekly for nine weeks.(21) These cows produced 4.75 lb less milk per day than did non-infected cows. Kloosterman and others reported cows infected with 200,000 infective larvae of O ostertagi produced 0.09 lb less milk per day, on average, than did non-infected controls.(22) The trend from these studies suggests that parasite infection has a detrimental effect on milk production. Parasite Treatment Can Increase Milk Production The literature contains several citations which support the premise that antiparasitic treatment of lactating adult dairy cows can increase milk production.(19) These studies utilized a variety of anthelmintics, including coumaphos, benzimidazoles (BZs), imidazothiazoles (IMZs), and avermectins. Mid-lactation Treatment In 19 studies, where cows were treated for parasites mid-lactation and followed for 60 days or less, milk production responses ranged from 2.86 lb/day to +4.64 lb/day, with a median increase of 1.76 lb/day (Figure 1). (19) Increases in milk production were noted in 15 of the 19 studies. Increases in five of the 15 studies were statistically significant (P<0.05); in the remaining four studies there were either minor (not statistically significant) decreases in milk production, or no change at all (Table 1). Pre-calving or Early-lactation Treatment There were 43 studies reported, where cows were treated one to three times during the dry period, or just before, or immediately after, calving.(19) Both seasonal and year-round calving systems were included. Increased milk production was demonstrated in 34 of the 43 studies (79%) when cows were treated between drying-off and week 2 of lactation (Table 1).(19) The increase was statistically significant (P<0.05) in 13 of the 34

The Effect of Anthelmintic Treatment in Adult Dairy Cows on Milk Production Page 4 of 8 studies that demonstrated an improvement. In these 43 studies, milk production was increased up to 4.55 lb/day, and the median change in milk production was approximately +0.92 lb/day (Figure 1). Strategic Treatment An increase in milk production was observed in 15 of 16 studies (94%) in which cows were treated multiple times over extended periods, or were treated strategically over a one-year period (Table 1).(19) The increase was significant (P<0.05) in two of the 15 studies that demonstrated an improvement. For all 16 studies, treatment of cows resulted in a median increase in production of 1.65 lb/day, ranging from -0.79 lb/day to +6.95 lb/day, comparing treated groups to control groups (Figure 1). Combined Data from All Treatment Programs When data from all 87 published studies are combined, 70 (80%) of the studies resulted in a positive response (P<0.001) to parasite treatment of adult dairy cows on milk production; with the median increase in milk yield being +1.39 lb/day (Table 1, Figure 1).(19) Using a milk price of $17.80/cwt, the average "mailbox" price paid for milk in December of 1998, over a full 300-day lactation, this additional 1.39 lb of milk per cow per day could amount to an average of 417 lb additional milk per cow treated a $74.23 value (Figure 2).(23) Table 1. Milk-production responses following anthelmintic treatment of dairy cattle (19) Results Results (multi-herd studies) Type of study Number positive/ Number studies Herds positive/ Herds in study Number of multi-herd studies Infective larvae 6/9(a) --- --- Mid-lactation 15/19(b) 8/10 1 Single treatment near 34/43(b) 236/342 19 calving Multiple or strategic treatments 15/16 24/30 4 Total 70/87 (80%) 268/382 (70%) 24 a Two studies did not report numeric results; b One study did not report numeric result

The Effect of Anthelmintic Treatment in Adult Dairy Cows on Milk Production Page 5 of 8 Figure 1. Extra milk production responses to antiparasitic treatment given on different schedules, as compared to controls Figure 2. Additional income per cow per lactation as a result of additional milk produced by cows treated for parasites, using December 1998 "mailbox" milk price ($17.80/cwt) On this basis, average projected additional earnings in milk production per cow per lactation for the different treatment programs could range from $49.13 for the single treatment near calving to $93.98 for the mid-lactation treatment (Figure 2). Anthelmintic Consistency Older anthelmintics such as coumaphos, thiabendazole and IMZs are less effective than later BZs, which in turn are less effective than avermectins, especially against immature parasites, including inhibited larvae of O ostertagi. Comparing studies using the older anthelmintics (coumaphos, thiabendazole, IMZs) with those using more modern products such as albendazole, fenbendazole, oxfendazole, and ivermectin suggests that as efficacy improves, so does reliability (97% positive response for modern products vs. 74% for older products) and consistency of response (-1.1 to +3.81 lb/day for modern products; -5.13 lb to +7.92 lb/day for older

The Effect of Anthelmintic Treatment in Adult Dairy Cows on Milk Production Page 6 of 8 products).(19) It should be noted that in the United States, ivermectin is not approved for use in female cattle of breeding age. IVOMEC EPRINEX (eprinomectin) Pour-On for Parasite Control in Dairy Cattle IVOMEC EPRINEX is the newest generation of the macrocyclic lactone family. This product resulted from an exhaustive research and development program designed to deliver a product superior to other endectocides. The active compound, eprinomectin, was selected after an initial screening of more than 500 avermectins and milbemycins. IVOMEC EPRINEX is more than 99% effective against eleven damaging internal parasites of cattle, including inhibited larvae of O ostertagi. IVOMEC EPRINEX is the only avermectin currently approved for use in dairy cattle of all ages even those in lactation. Conclusion Overall, the studies reviewed here demonstrated a positive response in milk production when adult dairy cows were treated for parasites. There was a median change of +1.39 lb milk per cow per day for cows that were given antiparasitic treatment. Over a full lactation, this could amount to as much as 417 lb of additional milk per cow treated, with a potential value of $74.23 (assumed milk price of $17.80/cwt). IVOMEC EPRINEX Pour-On for Beef and Dairy Cattle is a revolutionary design in parasite control providing more power, flexibility, convenience and confidence than ever before. IVOMEC EPRINEX has claims for 39 stages of internal and external parasites, including Chorioptes mite, which is the main culprit in "tail itch" or "barn itch." Being the only product of its class that requires no milk withholding, IVOMEC EPRINEX should be the product of choice for veterinarians and dairy producers who seek to improve overall herd efficiency, productivity, and profits. REFERENCES 1. Radostits OM, Leslie KE, Fetrow J. Internal parasites. In: Herd Health: Food Animal Production Medicine 2nd ed. Philadelphia, W.B. Saunders, 1994:323-324. 2. Armour J. The influence of host immunity on the epidemiology of trichostrongyle infections in cattle. Vet Parasitol 1989;32:5-19. 3. Hawkins JA. Economic benefits of parasite control in cattle. Vet Parasitol 1993;46:159-173. 4. Bairden K, Armour J. A survey of abomasal parasitism in dairy and beef cows in south-west Scotland. Vet Rec 1981;109:153-155.

The Effect of Anthelmintic Treatment in Adult Dairy Cows on Milk Production Page 7 of 8 5. Barth D, Bernhard D, Lamina J. The prevalence of gastro-intestinal nematodes in dairy cows. In: Nansen P, Jorgensen RJ, Soulsby EJL, eds. Epidemiology and Control of Nematodiasis in Cattle; Vol. 9 Current Topics in Veterinary Medicine and Animal Science. Boston, MA: Martinus Nijhoff Publishers;1981:117-129. 6. Bernhard D, Barth D, Lamina J. Magendarmnematoden bei Milchkühen. Berl Münch Tierärztl Wsch 1978;91:45-46. 7. Borgsteede FHM, Burg WPJ vd. Worm burdens in cows II. An analysis of the population of nematodes in the abomasa of adult dairy cows. Vet Parasitol 1982;10:323-330. 8. Burrows RO, Davison CC, Best PJ. Survey of abomasal parasitism of culled dairy cows in southern Britain. Vet Rec 1980;107:289-290. 9. Gutierres V, Todd AC, Crowley JW. Natural populations of helminths in Wisconsin dairy cows. Vet Med/SAC 1979;74:369-374. 10. Todd AC, Gutierres VC, Myers GH, et al. On the prevalence, nature and economic impact of dairy parasitisms in Wisconsin, in Proceedings 25th Ann Mtg AAVP;1980;27. 11. Vercruysse J, Dorny P, Berghen P, Geeraerts J. Abomasal parasitism in dairy cows in Belgium. Vet Parasitol 1986;22:285-291. 12. Heider LE, Courtney CH, Herd RP. The effect of thiabendazole treatment on dairy cows in Ohio, in Proceedings 25th Ann Mtg AAVP 1980;28. 13. O'Farrell KJ, Downey NE, Sherington J. The effect of anthelmintic treatment at calving on the subsequent milk production characteristics of dairy cows. Irish Vet J 1986;40:116-123. 14. Melancon, JJ. Prevalence of Internal Parasites in Northern Dairy Herds. Merial Veterinary Bulletin TSB-9-99021, 1999. 15. Fox MT, Gerelli D, Pitt SR, Jacobs DE, Gill M, Gale DL. Ostertagia ostertagi infection in the calf: Effects of a trickle challenge on appetite, digestibility, rate of passage of digesta and liveweight gain. Res Vet Sci 1989;47:294-298. 16. Fox MT, Gerelli D, Shivalkar P, Jacobs DE. Effect of omeprazole treatment on feed intake and blood gastrin and pepsinogen levels in the calf. Res Vet Sci 1989;47:280-282. 17. Heinemann W. Forage digestibility by nematode infested cattle. Washington Agr Exp Sta 1968; Circular # 491, 3.

The Effect of Anthelmintic Treatment in Adult Dairy Cows on Milk Production Page 8 of 8 18. Coppock CE. The importance of an energy-dense diet for highproducing dairy cows. Vet Med/Food Anim Pract 1990;85:429-434. 19. Gross SJ, Ryan, WG, Ploeger HW. Anthelmintic treatment of adult dairy cows and the effect on milk production. Vet Rec. 1999; 144:In Press. 20. Bliss DH, Todd AC. Milk losses in dairy cows after exposure to infective trichostrongylid larvae. Vet Med/SAC 1977;72:1612-1617. 21. Barger IA, Gibbs HC. Milk production of cows infected experimentally with trichostrongylid parasites. Vet Parasitol 1981;9:69-73. 22. Kloosterman A, Borgsteede FHM, Eysker M. The effect of experimental Ostertagia ostertagi infections in stabled milking cows on egg output, serum pepsinogen levels, antibody titres and milk production. Vet Parasitol 1985:17:299-308. 23. Hoard s Dairyman Online. Mailbox Prices. Available at: http://www.hoards.com/ Accessed April 19, 1999. Return to Table of Contents Veterinary Professional Services, Merial Limited, 2100 Ronson Road, Iselin, NJ 08830-3077. Tel 1 888 637 4251