Apparent Digestibility of Nutrients, Blood Parameters and Body Development of Dewormed and Not Dewormed Weanlings.

Weanlings undergo rapid body development in the first year of life and, in this period, are more susceptible to helminth infection that can impair their growth. The objective of this study was to compare the apparent digestibility of nutrients, blood parameters, and body development of deworming and not deworming weanlings. Fourteen Mangalarga Marchador weanling colts, on a farm in Northern Minas Gerais, Brazil, were divided into two groups: dewormed (D) and not dewormed (ND) groups. The weanlings were kept separately for 3 months in two pastures of Cynodon nlemfuensis cv. African Star Grass. They also were supplemented with Cynodon dactylon cv. Tifton 85 predried hay ad libitum and 1.5 kg.100 kg^-1 of body weight (BW) of corn-based concentrate. Eggs per gram of feces (EPG) of the weanlings were measured monthly. Group D was dewormed (200 mcg.kg^-1 BW ivermectin + 2.5 mg.kg^-1 BW praziquantel) whenever EPG was ≥500. Group ND weanlings were not treated. The weanlings were subjected to an apparent digestibility assay (total fecal collection procedure). Every month, the weanlings were weighed, evaluated for body condition score, and had withers height, croup height, body length, and thoracic circumference measured. Group ND was infected mainly by small strongyles. There was no difference between groups (P > .05) for morphometric measurements, dry matter intake, and digestibility coefficients, except for apparent digestibility of calcium, which was higher (P < .05) in group D. Small strongyles infection in six- to nine-month-old weanlings fed high grain, nutrient-balanced rations apparently did not affect growth, blood parameters, and apparent digestibility of nutrients.