Kidney changes in lambs fed cactus pear varieties resistant to Dactylopius opuntiae as the only roughage

This study aimed to evaluate the effects of four varieties of cactus pear resistant to carmine cochineal as exclusive roughage for lambs on the biochemical, histopathological, and histomorphometric parameters of kidneys. Twenty-four castrated male crossbred lambs at eight months of age and an initial body weight of 21.0 ± 0.5 kg were distributed in a completely randomized design, with four treatments and six repetitions. The experimental treatments consisted of four diets containing Miúda cactus pear, IPA-Sertânia cactus pear, IPA-F21 cactus pear, or Orelha de Elefante Mexicana (OEM) cactus pear as the only roughage. Blood samples were collected every two weeks (14 d, 28 d, 42 d, and 56 d) to quantify serum urea and creatinine levels. After 72 days of the introduction of the tested diets, the animals were slaughtered and fragments of the kidneys were collected for histological analysis. The serum urea level was higher in animals fed a diet based on the Miúda variety (49.38 mg dL^-1), and the serum creatinine levels were lower in the last two collections (P = 0.009). The most frequent histopathological findings in the kidneys were calcification, congestion, glomerular atrophy, presence of luminal cellular debris, and nephrosis, regardless of the cactus pear variety. The Miúda cactus pear and OEM cactus pear varieties caused more severe damage to the nephron components, while the varieties IPA F-21 and IPA-Sertânia caused less significant injuries. The use of IPA-Sertânia and IPA F-21 cactus pear varieties is suggested in lamb's diets, due to the lower impact on the renal parenchyma. However, there was no expressive impairment of renal function, and there was no difference between the cactus pear varieties tested in this study on the weight gain of the animals, and they can all be used to feed feedlot sheep.