Desempenho leiteiro e qualidade oocitária de vacas alimentadas com farelo de canola em substituiçãoao farelo de soja

Abstract

Replacing soybean meal with canola meal in dairy cow diets may enhance the supply of rumen undegradable protein and increase the flow of metabolizable amino acids, potentially improving milk production and its components while increasing nitrogen utilization efficiency. Additionally, the use of canola meal in diets may improve oocyte quality by reducing blood and follicular fluid nitrogen concentrations and increasing the activity of antioxidant enzymes in the follicular fluid. The main objective of the thesis was to evaluate the lactational performance and oocyte quality of dairy cows fed canola meal as a replacement for soybean meal. Thirty Holstein-Gir crossbred dairy cows (168 ± 66 days in lactation) were blocked by genetic composition (3/4, 5/8, and 7/8), parity (1 and ≥ 2 calvings), and milk yield in a randomized block design. Cows were assigned to treatments: (1) soybean meal diet (SBM; n = 15) and (2) canola meal diet (CM; n = 15) for eight weeks. Follicular aspiration was performed biweekly on 19 cows (SBM: n = 8; CM: n = 11). Milk yield (13.1 kg/d) and dry matter intake (16.2 kg/d) did not differ between treatments (P ≥ 0.21). The digestibility of organic matter and neutral detergent fiber, and the milk fat content were lower (P ≤ 0.03), and total solids content tended (P = 0.06) to be lower in cows fed CM compared to SBM. Milk urea nitrogen was lower (P < 0.01) in cows fed CM compared to SBM (13.1 vs. 16.3 mg/dL). Body weight was greater (561 vs. 544 kg; P = 0.01) and BCS tended to be greater (3.1 vs. 3.0; P = 0.10) in cows fed CM compared to SBM. Meal frequency, rumination time while lying down and the proportion of daily intake in the morning were greater (P =0.01) for cows fed CM than SBM. Plasma and follicular fluid metabolites, nitrogen partition, microbial protein yield, oocyte quality, and follicular fluid activity of antioxidant enzymes did not differ between treatments (P ≥ 0.12). Canola meal did not affect lactational performance, nitrogen metabolism, and oocyte quality but decreased milk fat content and milk urea nitrogen and increased the body weight of the cows.