ارزیابی استفاده از منابع مختلف نیتروژن در میش و بز در اواخر آبستنی و اوایل شیردهی

The objective of this study was to assess the effects of different nitrogen sources in the diets of sheep and goats during late pregnancy and early lactation. Twenty multiparous small ruminants (10 ewes and 10 does, all in their third parity) were allocated to a 2 × 2 factorial experiment arranged in a completely randomized design, with two dietary treatments and five replicates. The experimental treatments included a control diet containing soybean meal and an experimental diet containing biuret. The measured traits included dam and offspring weights, milk yield and composition, feed intake and nutrient digestibility, some blood metabolites, and urinary purine derivatives. The results showed no interaction between animal species and dietary treatments for all traits. In terms of dietary treatment (biuret or no biuret), only total blood protein and urinary uric acid were higher (P<0.05) in the control group compared to the biuret treatment. Regarding the differences between animal species, milk yield and composition, pre-partum daily dry matter intake, post-partum blood urea nitrogen, and pre-partum urinary creatinine (P<0.01) as well as pre-partum fat digestibility (P<0.05) were higher in sheep than in goats. Therefore, considering the lack of difference in many traits, biuret can be used as a cost-effective nitrogen source to replace soybean meal in the diet of sheep and goats during the transition period.