Voluntary intake of lactanting beef cows during pregnancy under tropical pasture and effects of DDG or sugar cane molasses on performance of calves and heifers respectively

• Ano de defesa: 2024
• Autor(a) principal: Matos, Ellem Maria de Almeida
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa; Zootecnia
• Palavras-chave em Português: Bovinos de corte - Alimentação e rações; Bovinos de corte - Registros de desempenho; CIENCIAS AGRARIAS::ZOOTECNIA
• Link de acesso: https://locus.ufv.br/handle/123456789/34958; https://doi.org/10.47328/ufvbbt.2024.729

Our objectives in the current study were: 1) to understand the voluntary intake of beef cows during gestation under grazing in tropical pastures; 2) to evaluate the effects of DDG supplementation on performance and digestion characteristics of suckling beef calves on tropical pastures and 3) to evaluate whether the inclusion of molasses affect voluntary intake, performance, digestive characteristics, and rumen epithelium cell development in young beef finishing heifers. For the first objective, thirty-seven multiparous Nellore cows, along their respective calves, with an average initial body weight (BW) of 517 ±15.7 kg and initial body condition score (BCS) of 5.0, were used. All cows were randomly assigned into eight paddocks with approximately 7.0 ha each, covered evenly with Urochloa decumbens signal grass. Intake and digestibility trials were carried out at approximately 4 days before the insemination (this time point was considered day 0 of gestation) and, 30, 60, 90, 120, 150, 180, 210, 240, and 270 days of gestation. Fecal output was estimated using chromic oxide (Cr2O3) as an external marker. We detected a quadratic pattern (P < 0.05) between week of pregnancy (WP) and dry matter intake (DMI, g/kg BW).In conclusion, the voluntary intake can be adequately described as a function of the week of pregnancy according to the following model: DMI = 20.978±0.9059 + 0.316±0.0947 × WP – 0.0134±0.0023 × WP2 For the second objective, thirty-seven Red Angus × Nellore male calves (162±4.1 kg BW; 120 days old) were used in this study. Cow-calf pairs were randomly assigned into eight paddocks with approximately 7.0 ha each. Four treatments were evaluated, as follows: control (mineral mixture only; n=8), supplement without DDG (n=10), or supplements including 375 (n = 9) and 750 (n = 10) g/kg DDG on a dry matter (DM) basis. The supplements were composed by ground corn, soybean meal, urea, and DDG, and formulated to contain 300 g CP/kg DM. Performance characteristics were evaluated by recording calves’ BW at the beginning and end of the experiment without prior fasting. The ADG and FBW decreased (P = 0.04) linearly as the level of inclusion of DDG in the supplement increased. In conclusion, including 375 or 750 g DDG/kg DM in supplements decreases performance suckling beef calves in tropical pastures. For the third objective, twelve newly weaned Red Angus × Nellore heifers, averaging 238±5.14 kg, were used. The basal diet consisted of corn silage, sorghum silage, ground corn, soybean meal, urea, and mineral mixture, with a forage-to-concentrate ratio of 50:50. The following treatments were evaluated: control (no addition of powdered molasses) or addition of 50 g/kg of diet (DM basis) of powdered molasses. On day 55 of the experiment, a digestibility carried out over a period of 5 days. Briefly, feces samples were collected immediately after defecation on days 1, 2, 3, 4, and 5 of the trial, respectively and on days 3 and 5 of the digestibility trial, urine samples were collected. All heifers were weighed at the beginning and end of the experiment after 16-hour solids fasting. Subsequently, the heifers were slaughtered. There was no effect (P = 0.15) of molasses inclusion in either intake variables or fatty acids concentration. Providing sugarcane molasses does not affect the intake, digestion characteristics, and performance of young beef finishing heifers fed with medium-quality diets. Keywords: beef cattle; by-products; digestion; forage intake.