RESUMO

Crossbreeding represents an important technique to improve growth, beef quality and adaptability in beef production systems in tropical countries. The aim of this study was to evaluate sire and dam breed effects on performance and carcass traits of crossbred cattle produced in a tropical environment. Heifers and steers were evaluated during the pre-weaning, the post-weaning (n = 173) and the finishing phase (n = 123). Animals were produced by mating Nellore (N_N), Angus × Nellore (A_N) and Caracu × Nellore (C_N) dams with Braford, Charbray and Caracu sires. After weaning, animals were raised grazing on Marandu grass for 12 months; thereafter they were housed in individual pens and finished in a feedlot, receiving a total mixed ration. Ultrasound carcass evaluations were performed to determine ribeye area (R_A), backfat thickness (B_T) and rump fat thickness (R_T). A_N progeny were heavier at birth than N_N (P < 0.05), and Braford progeny had greater birth BW than Caracu (P < 0.05). Greater weaning BW was observed in the A_N and C_N offspring compared to N_N (P < 0.01). Greater average daily gain during the post-weaning period was verified in the N_N progeny compared to C_N (P < 0.05). No dam or sire breed effects were observed for BW at the end of the post-weaning period (P > 0.05). Progeny of N_N cows had greater B_T (P < 0.05) and R_T (P < 0.01) at the end of the post-weaning period in relation to C_N. Greater R_A was observed in the Caracu progeny than in the Braford (P < 0.05), which showed greater R_T than the Charbray progeny at the end of the post-weaning period (P < 0.05). No dam or sire breed effects were verified for final BW at the feedlot or for feed efficiency traits (P > 0.05). A_N progeny were superior in final B_T compared to C_N (P < 0.01), and Braford progeny had greater R_T at the end of finishing than Charbray (P = 0.05). The use of crossbred dams allows an increase in productivity until weaning, but this is not maintained in the post-weaning and finishing periods. The use of Braford sires produces similar growth performance in the different stages of the production system to those seen with Charbray and Caracu sires but generates animals with higher fat thickness at the end of finishing, which may improve carcass quality and commercial value.

Assuntos

RESUMO

The effects of feeding pelleted citrus pulp (PCP) as a natural antioxidant source on the performance and milk quality of dairy cows fed highly polyunsaturated fatty acid (FA) diets were evaluated. Four lactating Holstein cows were assigned to a 4×4 Latin-square. Treatments, on a dry matter (DM) basis, were i) control diet; ii) 3% soybean oil; iii) 3% soybean oil and 9% PCP and; iv) 3% soybean oil and 18% PCP. When cows fed on citrus pulp, the DM intake tended to decrease. The total tract apparent digestibility of DM and ether extract decreased when cows fed on the control diet compared to other diets. Cows fed PCP had higher polyphenols and flavonoids content and higher total ferric reducing antioxidant power (FRAP) in milk compared to those fed no pelleted citrus pulp. Cows fed 18% PCP showed higher monounsaturated FA and lower saturated FA in milk fat compared with cows fed the other diets. The lowest n-6 FA proportion was in milk fat from cows fed control. The present study suggests that pelleted citrus pulp added to 9% to 18% DM increases total polyphenols and flavonoids concentration, and the FRAP in milk.

RESUMO

Four ruminally fistulated primiparous lactating Holstein cows were assigned to a 4 × 4 Latin square design to determine the effects of the site of administration (rumen or abomasum) of flax oil and flax hulls on diet digestibility and milk fatty acid profile of dairy cows. The treatments were 1) oil and hulls administered in the rumen and abomasal infusion of water (RUM/RUM), 2) oil and hulls infused in the abomasum (ABO/ABO), 3) oil administered in the rumen and hulls infused in the abomasum (RUM/ABO), and 4) oil infused in the abomasum and hulls placed in the rumen (ABO/RUM). Cows on the ABO/ABO and RUM/RUM treatments had the highest and lowest amounts of basal dry matter eaten, respectively. Higher dry matter digestibility was obtained when flax oil bypassed the rumen (ABO/ABO and ABO/RUM) compared with when flax oil was administered directly in the rumen (RUM/ABO and RUM/RUM). Apparent digestibility of ether extract was higher when flax hulls were administered in the rumen (RUM/RUM and ABO/RUM) compared with when flax hulls were infused in the abomasum (ABO/ABO and RUM/ABO). The lowest digestibility of acid detergent fiber and neutral detergent fiber was obtained when both flax products were added in the rumen, which may be attributed to the high amount of oil present in the rumen (7.8% of total dry matter input). The lowest yield of 4% fat-corrected milk was obtained for cows on the RUM/RUM treatment, probably as a result of lower dry matter intake and digestibility of fiber. Milk concentrations of protein, fat, total solids, and lactose were similar among treatments. Administration of oil and hulls in the rumen resulted in the highest concentrations of intermediate products of biohydrogenation and total trans fatty acids in milk fat compared with the other treatments. All ratios of n-6 to n-3 fatty acids in milk fat were lower than the 4 to 1 ratio recommended to improve human health. These results suggest that the presence of both flax oil and flax hulls in the rumen decreases 4% fat-corrected milk yield and digestibility but provides a desirable fatty acid profile of milk to enhance consumers' health.

Assuntos