Suitability of electronic mini-boluses for the early identification of goat kids and effects on growth performance and development of the reticulorumen.

A total of 60 twin-goat kids (30 male and 30 female) of the Canary Island Majorera dairy breed were used in 2 experiments to evaluate 2 types of electronic identification mini-boluses and their effects on rearing performances and reticulorumen development. Electronic identification mini-boluses were cylindrical and made of ceramic materials (B1, 9.0 g and 38.5 × 9.5 mm; B2, 16.3 g and 42.2 × 12.2 mm), contained a 32-mm half-duplex passive transponder, and were administered to kids at different BW. In Exp. 1, treatments were 1) control, without bolus (n = 15) and 2) identified with B1 at 4.8 kg of BW (n = 15). In Exp. 2, treatments were 1) control, without bolus (n = 15) and 2) identified with B2 at 5.6 kg of BW (n = 15). Kids were penned separately, according to mini-bolus treatments, fed a milk replacer daily, and slaughtered at 10 kg of BW. Milk replacer intake was recorded individually twice weekly and boluses read weekly until slaughter. The full and empty stomach complex was measured immediately after slaughter, and mini-bolus location was recorded. Samples of the reticulum and rumen wall were taken to measure the number and length of the papillae and crest. Despite the light BW of kids at time of mini-bolus treatment, no negative effects (P > 0.05) of B1 and B2 mini-boluses were observed on milk intake, growth rate, or G:F in either experiment. No kid mortality or mini-bolus losses were observed during either experiment. All mini-boluses were retained until slaughter, and all were found in the rumen upon dissection, except one B2, which was found in the reticulum. Mini-bolus treatment did not affect (P > 0.05) the weight of full and empty reticulorumen or the number of papillae and crest size of the reticulum epithelium. Moreover, the B1-treated kids showed a greater number of papillae in the rumen wall than the control kids (22.4 +/- 1.0 vs. 18.9 +/- 0.9 papillae/cm, respectively; P < 0.05) in Exp. 1. In conclusion, the use of mini-boluses was suitable for the electronic identification of growing kids from early ages (wk 2 to 5 of age and 5 to 6 kg of BW) and did not produce negative effects on their growth performances or on reticulorumen development. These results support the use of properly designed boluses as a unique identification device for the entire lifespan of goats.