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.

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.