gastrointestinal parasites presence during the peripartum decreseas total milk production in grazing dairy Holstein cows

A.F. PERRI, M.E.MEJÍA,N. LICOFF, L.LAZARO, M.MIGLIERINA, A. ORNSTEIN, D. BECÚ- VILLALOBOS, I.M. LACAU- MENGIDO

VETERINARY PARASITOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2011 vol. 178 p. 311 - 318

1514-6634

Parasitism in cattle is known to impair growth and development. Recent findings suggestthat productivity of adult animals is also affected, but little is known about the physiologicalmechanisms involved. Furthermore, development of nematode resistance to drugsmakes imperative the search of management practices that avoid whole herd treatment.Weundertook an epidemiological and endocrine study in a grass based dairy farm in Argentinato study the effect of parasites on milk production and the underlying mechanisms involved,and identify individual animals that would benefit from antiparasitic treatment. All thecows in the dairy were followed monthly for egg parasite output in feces. Samples werecultured for genera determination. Milk production and reproductive results were recordedand periodical bleedings for hormone determination were performed. Nematode egg output(EPG) was maximal in late Summer and Autumn and minimal in Spring in coincidencewith the Ostertagia inhibition–disinhibition cycle as this genus had the highest prevalencein all the study. The highest proportion of positive samples was found in the high producingherd and maximal counts were found in the peripartal period. Milk production did notcorrelate with EPG mean values but, when cows were grouped by EPG positivity aroundparturition, a significant difference in total milk production between EPG null and positivecows was observed. Positive cows produced 7%, 12% or 15% less milk than null EPGcows, depending on the sampling month/s chosen for classification. The highest differencewas seen when both prepartum and postpartum samples were taken into account. No differencein lactation length and a marginal effect on partum to first service interval wereencountered. Endocrine studies revealed a decrease in serum growth hormone (GH), type Iinsulin-like growth factor (IGF-I) and prolactin during lactation in cows with positive EPG inthe first postpartum sample with respect to null EPG cows at that time. GH levels decreasedand prolactin and IGF-I levels increased in both groups of cows from month 0 to 6 in milk.Serum insulin levels remained stable throughout lactation and were similar in both groupsof cows. In conclusion, EPG around parturition may be a useful tool for identifying cows thatwill have a decrease in productivity due to parasite effects and would possibly benefit froman antiparasitic treatment. Besides, our results suggest that detrimental effect of parasiteson milk production may be mediated by GH, IGF-I and prolactin serum levels.© 2011 Elsevier B.V. All rights reserved