Nutritional strategies for heifers under grazing system: productive and nutritional performance, metabolic profile and ovarian activity.

The objective of this study was to evaluate the effects of nutritional strategies on productive and nutritional performance, metabolic profile, and ovarian activity in heifers under grazing in the tropics in Brazil. Forty Nellore heifers averaging 8.5 ± 0.06 months and 248.6 ± 3.3 kg body weight (BW) were distributed in a completely randomized 2 × 2 factorial design with four treatments and ten replicates. The evaluated strategies consisted of different amounts of energetic-protein supplement: (1) 4 g/kg of BW of supplement in the pre-weaning and post-weaning; (2) 4 g/kg of BW of supplement pre-weaning and 6 g/kg in the post-weaning; (3) 6 g/kg of BW of supplement in the pre-weaning and 4 g/kg of BW in the post-weaning and; (4) 6 g/kg of BW of supplement in the pre-weaning and post-weaning. Crude protein (CP) and organic matter (OM) intake were increased (P < 0.05) by increasing the amounts of supplement in the post-weaning. Additionally, increasing supplement amounts in the post-weaning increased the digestibility of OM and CP (P < 0.05). Means insulin and glucose concentrations were greater (P < 0.05) for heifers that received higher amounts of supplement in the post-weaning. Average daily gain and fat thickness in the rump were increased (P < 0.05) by increasing supplement amounts in the post-weaning. Amounts of supplement did not influence the body growth of heifers. However, follicular number, diameter, and progesterone concentration were greater (P < 0.05) for heifers that received higher amounts of supplement in the post-weaning. In summary, increasing supplement amounts in the post-weaning improve the performance, energy and metabolic status, and ovarian activity in beef heifers under grazing in the tropics. Due to higher intake of supplement, the heifers receiving 6 g/kg of BW post-weaning had greater responses, independently of the supplement amount received pre-weaning.

Metabolism prepartum and reproductive responses postpartum of Nellore cows supplemented in different periods of gestation / Metabolismo preparto y respuestas reproductivas postparto de matrices Nelore suplementadas en diferentes periodos de la gestación / Metabolismo pré-parto e respostas reprodutivas pós-parto de matrizes Nelore suplementadas em diferentes períodos da gestação

Abstract The purpose of this study was to determine the effect of cow's grazing supplementation during pregnancy on the concentration of metabolites in blood and its relation with uterine involution and postpartum fertility. Twenty-seven Nellore cows were divided into three groups (n=9 for each group) as follows: UNS, unsupplemented during gestation; MID, supplemented from the 30 to 180-day of gestation; LATE, supplemented from the 181 to 281-day of gestation. Blood samples to determine the concentrations of NEFA, BHBA (β-hydroxybutyrate) and the glucose was performed on days 30, 105, 180, 230 and 281 of gestation. Fixed-time artificial insemination (FTAI) was performed in all matrices at forty-five days postpartum. Lower NEFA and BHBA concentrations it was observed in the MID and LATE group at 180 and 281 days of gestation respectively for each treatment. A higher glucose concentration was observed at 180 and 281 days of gestation for MID and LATE treatment, respectively. There were no differences in uterine involution and percentage of gestation between treatments. Pre-partum supplementation improves energy balance without altering uterine involution and postpartum fertility.

Resumen El propósito de este estudio fue determinar el efecto de la suplementación a pasto de vacas durante la gestación sobre la concentración de metabolitos en sangre y su relación con involución uterina y fertilidad posparto. Veintisiete vacas Nelore se dividieron en tres grupos (n = 9 para cada grupo) de la siguiente manera: UNS, sin suplementos durante la gestación; MID suplementados desde los 30 hasta los 180 días de gestación; LATE, suplementado desde los 181 hasta los 281 días de gestación. Coletas de sangre para determinar las concentraciones de NEFA, BHBA (β-hidroxibutirato) y glucosa se realizaron en los días 30, 105, 180, 230 y 281 de gestación. La inseminación artificial a tiempo fijo (AITF) se realizó en todas las matrices a los cuarenta y cinco días después del parto. Se observaron concentraciones bajas de NEFA y BHBA en los grupos MID y LATE a los 180 y 281 días de gestación, respectivamente, para cada tratamiento. Se observó mayor concentración de glucosa a los 180 y 281 días de gestación para los tratamientos MID y LATE, respectivamente. No hubo diferencias en la involución uterina y el porcentaje de estación entre los tratamientos. La suplementación pre-parto mejora el balance energético sin alterar la involución uterina y la fertilidad posparto.

Resumo O objetivo do estudo foi determinar o efeito da suplementação a pasto de matrizes durante a gestação sob a concentração de metabolitos em sangue e sua relação com involução e fertilidade pós-parto. Vinte sete matrizes Nelore foram alocadas em três grupos como segue-se: UNS, não suplementadas durante a gestação; MID, suplementadas desde os 30 - 180 dias da gestação; LATE, suplementadas desde 181 - 281 dias da gestação. Amostras de sangue para determinar as concentrações de NEFA, BHBA (β-hidroxibutirato) y glucose se coletaram nos dias 30, 105, 180, 230 y 281 da gestação. Inseminação artificial a tempo fixo (IATF) se realizou em todas as matrizes aos 45 dias após o parto. Menores concentrações de NEFA e BHBA foram encontradas nos grupos MID e LATE aos 180 e 281 dias de gestação, respetivamente. Maiores concentrações de glucose aos 180 e 281 dias da gestação foram observadas nos tratamentos MID e LATE respetivamente. Não houve diferenças na involução uterina e a porcentagem de gestação entre os tratamentos. A suplementação pré-parto melhora o balanço energético sem alterar a involução uterina e a fertilidade pós-parto.

Nutritional planning for Nellore heifers post-weaning to conception at 15 months of age: performance and nutritional, metabolic, and reproductive responses.

The objective of this study was to evaluate the effects of strategic supplementation in the dry period and dry/rainy transition period on the performance and nutritional, metabolic, and reproductive responses of Nellore heifers grazing Urochloa decumbens. Forty-eight Nellore heifers with age and body weight (BW) of eight months and 235 ± 3.3 kg, respectively, were used. The experimental design was a completely randomized design, with four treatments, all with 12 replications. The evaluated strategies were as follows: low supplementation (LOHI; 0.2% of BW/heifer/day) in the first 90 days and high supplementation (0.6% of BW/heifer/day) in the 90 days thereafter; average supplementation (AVER) with 0.4% of BW/heifer/day for 180 days; high supplementation (HILO; 0.6% of BW/heifer/day) in the first 90 days and low supplementation (0.2% of BW/heifer/day) in the 90 days thereafter; only mineral mix (MM) ad libitum during the 180 days. Data were evaluated using orthogonal contrasts. Supplementation improved the performance of the animals during of dry period (P < 0.05) and dry/rainy transition period (P < 0.05). Supplemented animals had higher longissimus muscle area (LMA) and subcutaneous fat thickness (SFT) at the end of the experiment (P < 0.05). Multiple supplementation increased intake of dry matter (DM), organic matter (OM), and crude protein (CP) in kg/day throughout the experiment. The supplementation increased the digestibility of DM, OM, CP, apNDF, and TDN (P < 0.05). Serum urea nitrogen (SUN), glucose (GLUC), insulin (INS), and progesterone (PROG) were higher in supplemented heifers (P < 0.05). Supplementation reduced the concentrations of non-esterified fatty acids (NEFA) (P < 0.05) and increased conception rate (P < 0.05). In summary, the supplementation strategies adopted in this study improve the performance, metabolic status, and carcass traits of heifers under grazing, allowing an improvement in the conception rate of 15-month-old Nellore heifers.

Soybean grain is a suitable replacement with soybean meal in multiple supplements for Nellore heifers grazing tropical pastures.

The research aimed to evaluate the effect of replacing soybean meal with soybean grain on the nutritional parameters and productivity of heifers grazing on Urochloa decumbens in the rainy-dry transition period. Forty crossbred heifers with the initial age and weight of 18 months and 292 ± 6.1 kg, respectively, were used. The experimental design was a completely randomized design, with five treatments and eight replications. The evaluated treatments were as follows: SM0.5-supply of 0.5 kg/animal/day of soybean meal supplement; SG0.5-supply of 0.5 kg/animal/day of soybean grain supplement; SM1.0-supply of 1.0 kg/animal/day of soybean meal supplement; SG1.0-supply of 1.0 kg/animal/day of soybean grain supplement; MM-only mineral mix ad libitum. The supplement was isoprotein with 350 g of crude protein/kg of dry matter. Supplementation improved the performance of the heifers and this fact can be verified by the higher average daily gain (ADG) and final BW (fBW) of the supplemented animals (P < 0.10). The two supplemented treatments with 1 kg/day demonstrated similar performance (P > 0.10), the same happens for the two treatments receiving 0.5 kg/day (P > 0.10). However, animals receiving 1 kg/day of supplementation had an ADG and final BW higher than animals receiving 0.5 kg/day (P < 0.10). Supplementation (P < 0.10) affected the intake of dry matter (DM), organic matter, crude protein, ether extract, non-fiber carbohydrates, total digestible nutrients, and neutral detergent fiber corrected for ash and protein (apNDF). Supplementation improved DM digestibility and all constituents of the diet (P < 0.10), except for apNDF (P > 0.10). In summary, it is concluded that multiple supplementations improve the performance of grazing heifers in the rainy-dry transition period and the total replacement of soybean meal by soybean grain does not alter the performance of the animals.

Supplementation strategies for Nellore female calves in creep feeding to improve the performance: nutritional and metabolic responses.

The objective of this study was to evaluate the effects of supplementation strategy on performance, nutritional and metabolic characteristics of Nellore suckling female calves, on grazing Urochloa decumbens during the rainy-dry transition period. Forty-four Nellore female calves, averaging 147.6 ± 1.34 kg (4 months), were used. A single supplement 20% of crude protein of dry matter was provided, consisting of daily supplement at 0.0, 0.2, 0.4, or 0.6% of body weight. A positive linear effect (P < 0.05) on final body weight and average weight gain of female calves was observed with increased supplementation. Supplementation increased consumption, in kilograms per day, of dry matter (DM), organic matter (OM), crude protein (CP), digested dry matter, and total digestible nutrients (TDN), all calculated as % of dry matter. There was no effect of supplementation on the consumption in kilograms per day of neutral detergent fiber corrected for ash and protein (apNDF) (P > 0.05). Supplementation increased, in a quadratic way, the total apparent digestibility coefficient of DM, OM, CP, apNDF, and TDN (P < 0.05). There was no effect of supplementation (P > 0.05) on non-esterified fatty acid concentrations. There was a positive linear effect (P < 0.05) of supplementation on insulin concentrations. In this study, it is concluded that linearly increasing the feeding level of a supplement with 20% crude protein (% of DM) in the range of 0.2-0.6% of body weight improves the performance, nutritional and metabolic characteristics of the animals, considering these pasture characteristics.

Estimation of daily milk yield of Nellore cows grazing tropical pastures.

Beef cows' milk yield is typically determined by measuring milk yield once daily and then doubling this value to estimate daily production. However, it is not known whether this is accurate. Thus, we aimed to determine the association between morning and afternoon milk yield in grazing Nellore cows. Eighty Nellore cows were used, with initial weight of 516.0 ± 1.0 kg. The experiment was a completely randomized factorial scheme, with 20 replications and four treatments (i.e., + or - pre-partum supplementation in combination with + or - post-partum supplementation): PRMM-1 kg of supplement/cow/day for 90 days pre-partum; MMPS-1 kg of supplement/cow/day for 90 days post-partum; PRPS-1 kg of supplement/cow/day for 90 days pre-partum and 90 days post-partum; and MM-only mineral mix ad libitum during pre- and post-partum. Milk was sampled on days 45, 135, and 225 post-partum (early, middle, and late lactation, respectively). No effects were observed of pre- and post-partum supplementation on milk yield (P > 0.05). The afternoon/morning proportion of 0.45 in the early third of lactation was higher than other stages, which had a proportion of 0.41 (P < 0.05). Post-partum supplementation increased milk protein in the morning and afternoon milking (P < 0.05). There was also no effect of pre- and post-partum supplementation on afternoon-morning proportion other milk components (P > 0.05). We conclude that estimating daily milk production of grazing beef cattle by multiplying a once daily milking amount times two is not accurate. Under the conditions of this study, proportion of total daily production represented by the ratio of afternoon/morning milking was 0.45 in early lactation (first third) and 0.41 in mid- and late lactation.

Creep feeding effects on male Nellore calves influencing behavior and performance of their dams.

The objective of the present study was to evaluate the effect of different schemes of calves' supplementation in a creep feeding system, on the behavior of Bos indicus calves and dams, and also the influence of the calves' supplementation on dams' performance. Forty-eight Nellore male calves (147 ± 7 kg body weight and 3 months of age) in the suckling phase and their dams (476 ± 9 kg and 6 years of age) were studied in a completely randomized design. The experiment was divided into two periods of 71 days. The treatments were 5- and 10-g supplement dry matter (DM)/kg BW day offered in periods 1 and 2, respectively (5S/10S); 10- and 5-g supplement DM/kg BW day offered in periods 1 and 2, respectively (10S/5S); 7.5-g supplement DM/kg BW day in both periods 1 and 2 (7.5S); and mineral mix ad libitum in both periods 1 and 2 (MM). No differences (P < 0.05) in body condition score (BCS), final body weight (FBW), and average daily gain (ADG) were found in dams' performance. Calves from MM treatment spent more time (P < 0.05) grazing than the supplemented calves from 5S/10S and 10S/5S treatments, in the first period. No difference in suckling time was found between the treatments (P > 0.05) in the first evaluated period. Calves from 10S/5S treatment spent more time suckling and less time eating supplements (P < 0.05) than 5S/10S treatment animals, in the second evaluated period. Dams of MM treatment's calves had more idle time and lower grazing time when compared with the mothers of calves from 5S/10S and 10S/5S treatments. It was concluded that different schedules of Nellore calves' supplementation on pasture do not affect their mothers' performance, and supplementation decreases the grazing time of calves in the suckling phase.