Effects of monensin in supplements for beef cattle in tropical grazing systems during the rainy season.

Two experiments were carried out to evaluate the effect of monensin in supplements for grazing heifers. In experiment I, treatments consisted of protein supplements (low intake - 0.5 kg/animal/day and high intake - 1.0 kg/animal/day) associated or not with monensin. Animal performance, nutrient intake, and digestibility were evaluated. Forty crossbred heifers with an initial body weight (BW) of 213.8 ± 4.5 kg were used. There was no difference in average daily gain between treatments (average of 0.588 kg/animal/day). There was no interaction between monensin and supplements for intake parameters and digestibility. Dry matter (DM) intake was equal between treatments (~ 2% of BW). However, there was a reduction in pasture intake with the high-intake supplement. In experiment II, treatments consisted of two types of supplements (protein or mineral) associated or not with monensin. The variables analyzed were productive performance, ingestive behavior, and thermal comfort, evaluated through the index of thermal stress for cows (ITSC). Forty crossbred heifers with a BW of 159.2 ± 1.3 kg were used. The type of supplement did not influence the performance of the animals. However, monensin promoted greater weight gain in the animals (110 g/animal/day). There was an interaction effect between supplementation and monensin addition on behavioral activities, except for idle time. The inclusion of monensin in the protein supplement reduced the grazing time. The ITSC value influenced the activities of ingestive behavior, and the increase of this index reduced the grazing time in all treatments. Forage quality influences the response to monensin use, and the addition of monensin in supplements for grazing cattle during the rainy season is recommended for forages with high CP content.

Energy to protein ratios in supplements for grazing heifers in the rainy season.

This study evaluated the effect of energy and protein supplementation on the nutritional characteristics, ingestive behavior, and productive performance in grazing heifers during the rainy season. Forty crossbred heifers (Nelore breed predominance) were used in the study, with an age of 14 months and an initial mean weight of 182 ± 1.13 kg. The treatments consisted of mineral supplementation ad libitum (control) and three supplements formulated to contain an energy: protein ratio (TDN:CP) of 1.13, 2.62, and 4.06; these were denominated as low (LC, 0.5 kg animal d-1), medium (MC, 1.0 kg animal d-1), and high consumption (HC, 1.5 kg animal d-1), respectively, in order to guarantee an intake of 300 g of crude protein (CP) animal-1 d -1, with variation in energy content. There was a difference (P < 0.05) in crude protein intake, with a 44% reduction for the LC treatment in relation to HC. The lowest grazing time (398 min) was observed with the MC treatment. Urinary urea-N (UreaN) was lower for control animals (P < 0.05). Average daily gain (ADG) was lower for the control animals than for the supplemented animals (P < 0.05); there was no difference in ADG between the animals receiving supplementation. High supplementation levels and TDN:CP ratios are not recommended because they do not justify the increased costs of supplementation. Therefore, when forage presents great nutritional characteristics, it is possible to optimize the performance of the animals with low to medium consumption supplementation.

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.

Does supplementation of beef calves by creep feeding systems influence milk production and body condition of the dams?

The aim of this study was to evaluate the effects of beef calves' supplementation in creep feeding systems on milk yield, body weight (BW), and body condition score (BCS) of their dams on tropical pastures using a meta-analytical approach. The database was obtained from 11 experiments conducted between 2009 and 2014 in Brazil, totaling 485 observations (cows). The database consisted of 273 Nellore and 212 crossbred (7/8 Nellore × 1/8 Holstein) cows. All experiments were carried out in the suckling phase (from 3 to 8 months of age of calves) during the transition phase between rainy and dry seasons from February to June of different years. The data were analyzed by a meta-analytical approach using mixed models and taking into account random variation among experiments. Calves' supplementation (P ≥ 0.59) and the calves' sex (P ≥ 0.48) did not affect milk yield of cows. The average fat-corrected milk (FCM) yield was 6.71 and 6.83 kg/day for cows that had their calves supplemented and not supplemented, respectively. Differences were observed (P < 0.0001) for milk yield due to the genetic group where crossbred cows presented greater FCM yield (7.37 kg/day) compared with Nellore cows (6.17 kg/day). There was no effect of the calves' supplementation on BW change (P ≥ 0.11) and BCS change (P ≥ 0.23) of the cows. Therefore, it is concluded that supplementation of beef calves using creep feeding systems in tropical pastures does not affect milk yield, body weight, or body condition of their dams.

Levels of supplementation for grazing beef heifers.

The objective of this experiment was to evaluate the effect of providing different levels of a supplement on the nutritional characteristics and productive performance of heifers on pasture during the rainy-dry transition and dry season in Brazil or tropical area. Thirty crossbred heifers with predominance of Zebu breed were used in a completely randomized experimental design. Treatments consisted of a mineral supplement and 0.5, 1.0, 1.5, or 2.0 kg/animal/d of a protein supplement containing 300 g crude protein (CP)/kg of dry matter (DM). In the rainy-dry transition season there was quadratic effect of the protein supplementation (p<0.10) on daily weight gain (DWG). A linear relationship (p<0.10) was found between increasing supplement intake and intakes of DM, organic matter (OM), crude protein (CP), ether extract (EE), non fibrous carbohydrates (NFC) and total digestible nutrients (TDN). Coefficients of apparent digestibility of CP, EE, and NFC increased linearly (p<0.10) with increasing supplement levels, but there was no effect on the DM apparent digestibility (p>0.10); the microbial efficiency (g CPmic/kg TDN) and the relationship of microbial nitrogen flow with nitrogen intake (g/g nitrogen intake) were negative linear profiles. In the dry season, the descriptive pattern least squares means showed a trend of stabilization of DWG from the supply of 0.98 kg of protein supplement; the intakes of DM, OM, CP, EE, NFC, and TDN showed increasing linear relationship (p<0.10) with protein supplement levels; the means of apparent digestibility coefficients of the different dietary fractions presented a linear-response-plateau (LRP); the microbial nitrogen flow (g/d) showed positive linear profile (p<0.10) for supplementation levels. It is concluded that supplementation improves the productive performance of grazing heifers and that 1.0 kg/d of supplement per animal gives the maximum increment of weight gain.

Levels of supplementation for grazing pregnant beef heifers / Níveis de suplementação para novilhas de corte prenhes em pastejo

The objective of this work was to evaluate the effect of different levels of multiple supplement supply on the nutritional characteristics and productive performance of pregnant heifers grazing Brachiaria decumbens Stapf. during the dry season. The experimental area was composed of four 3.0-ha paddocks with potentially digestible dry matter availability of 1,863 kg/ha. Twenty four crossbred heifers at 32 months and average initial body weight of 416±6 kg were used. The experimental design was in a completely randomized. The treatments consisted of mineral supplement and supply 0.5, 1.0, 2.0 kg/animal/day of multiple supplement. The dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), non-fibrous carbohydrates and total digestible nutrients (TDN) intake showed increasing linear relationship (P<0.10) with multiple supplement levels. Coefficients of apparent digestibility of DM, OM and non-fibrous carbohydrates also had linear effect (P<0.10) on the multiple supplementation levels. The microbial nitrogen flow and efficiency there was not affect (P>0.10) by levels of multiple supplementation; however the microbial nitrogen flow in relation to nitrogen intake showed decreasing linear profile (P<0.10). On the average daily gain was observed quadratic effect of multiple supplementation (P<0.10). In conclusion, the supply of 1.5 kg of multiple supplement optimizes the performance of grazing heifers during the dry season.

Objetivou-se avaliar o efeito do fornecimento de diferentes níveis de suplemento múltiplo sobre as características nutricionais e o desempenho produtivo de novilhas prenhes sob pastejo em Brachiaria decumbens Stapf. no período da seca. A área experimental constituiu-se de quatro piquetes de 3,0 hectares cada, com disponibilidade média de matéria seca potencialmente digestível (MSpd) de 1863 kg/ha. Os animais experimentais foram 24 novilhas prenhes mestiças com predominância de sangue zebuíno com idade e peso médio inicial de 32 meses e 416±6 kg, respectivamente, em um delineamento inteiramente casualizado. Os tratamentos consistiram em suplemento mineral e fornecimento de 0,5; 1,0 e 2,0 kg/animal/dia de suplemento múltiplo. Verificou-se efeito quadrático dos níveis de fornecimento de suplemento múltiplo (P<0,10) sobre o ganho médio diário. Os consumos de matéria seca (MS), matéria orgânica (MO), proteína bruta, extrato etéreo, carboidratos não fibrosos (CNF) e nutrientes digestíveis totais apresentaram relação linear crescente (P<0,10) com os níveis de fornecimento de suplemento múltiplo. Os coeficientes de digestibilidade aparente da MS, MO e CNF apresentaram perfil linear crescente (P<0,10) para os níveis de suplementação múltipla. Não houve efeito dos níveis de suplementação múltipla sobre o fluxo de compostos nitrogenados microbianos e eficiência de síntese microbiana, mas o fluxo de compostos nitrogenados microbiano em relação ao nitrogênio ingerido apresentou perfil linear decrescente (P<0,10). O fornecimento de 1,5 kg de suplemento múltiplo otimiza o desempenho de novilhas prenhes em pastejo no período da seca, mas não influencia o consumo de matéria seca do pasto e o fluxo de compostos nitrogenados microbianos.

Supplementation of suckling beef calves with different levels of crude protein on tropical pasture.

The effects of supplementation with different levels of crude protein on performance, intake and nutrient digestibility and efficiency of microbial protein synthesis in suckling beef calves on pasture were assessed. Fifty-five calves, with an average age of 100 days and an initial average body weight of 110 ± 7.5 kg and their respective dams, were used. The experimental design was completely randomised with five treatments and 11 replications. The experimental treatments for calves were as follows: control = calves received only mineral mixture; supplementation levels = calves received supplement containing 8, 19, 30 or 41% of crude protein (CP, at a rate of 0.5% of body weight (BW)). The cows received only mineral mixture ad libitum. Supplemented calves had higher (P < 0.1) average daily gain (ADG). Protein levels showed a quadratic effect (P < 0.1) on average daily gain (ADG) of calves. There was no difference in total dry matter (DM) intake (P > 0.1). However, intake of dry matter forage (DMF) presented cubic profiles (P < 0.1), with CP levels in the supplements. Supplementation increased (P < 0.1) the digestibility of nutrients, except for the digestibility of neutral detergent fibre. Supplementation increased (P < 0.1) the production of microbial nitrogen and N losses in urine. It can be concluded that multiple supplementations optimise the performance of beef calves on creep feeding. The intake of supplements with CP levels between 8 and 30% partially replaces of the pasture ingested by calves and increases the digestibility of the diet.

Effect of calves' supplementation on performance, nutritional and behavioral characteristics of their dams.

The effects of supplementation of beef calves on weight gain, intake and digestibility of pasture, milk production and composition of their dams, and behavior of the pair cow-calf were assessed. Fifty-five beef cows with an initial average body weight of 449 ± 8 kg and their respective offspring, with an initial average body weight of 138 + 3 kg and aged between 90 and 150 days, were used. Animals were submitted to an experimental period of 112 days. The experimental treatments consisted of: control = mineral mixture only, plan 1 = high protein and high carbohydrate multiple supplement, plan 2 = high protein and low carbohydrate multiple supplement, plan 3 = low protein and high carbohydrate multiple supplement, and plan 4 = low protein and low carbohydrate multiple supplement. About 25 and 12.5 % of the protein requirements were supplied by the high and low protein supplements, respectively, and 15 and 7.5 % of total digestible nutrient requirements by the high and low carbohydrate supplements, respectively. Grazing behavior, performance, milk production, milk composition, intake, and digestibility of the cows were not affected (P > 0.05) by the supplementation of the calves. The supplemented calves had greater (P < 0.05) performance (as measured by final body weight, average daily gain, and final body condition score), intake and idle time, and lower (P < 0.05) grazing time, but supplementation did not affect (P > 0.05) suckling time and suckling frequency. It can be concluded that supplementation affects the behavior and feed intake of calves. However, it does not affect the suckling time and suckling frequency of calves. Additionally, performance, milk production, nutritional characteristics, and behavior of their dams are not affected.

Strategies of supplementation of female suckling calves and nutrition parameters of beef cows on tropical pasture.

The performance of female calves in creep feeding under different strategies of supplementation and milk production, intake, and digestibility of grazing Nellore and crossbred cows (Nellore × Holstein) during the dry-rainy transition season were assessed. Forty-four female beef suckling calves, with initial age between 90 and 150 days and average initial body weight of 117.7 ± 4.3 kg, and their respective dams (24 Nellore and 20 crossbred) with average initial body weight of 417.5 ± 8.3 kg, were used. The experimental treatments consisted of: control group--mineral mixture only; strategy 1--supplementation from 112 days prior to weaning (0.375 kg/animal/day); strategy 2--supplementation from 112 days prior to weaning, in increasing amounts of 0.15, 0.30, 0.45, and 0.60 kg/animal/day through the four experimental periods, respectively; and strategy 3--supplementation from 56 days prior to weaning (0.750 kg/animal/day). Calves from strategy 1 had greater (P < 0.05) average daily gain (0.672 kg/day) than control animals (0.582 kg/day) and greater (P < 0.05) efficiency of supplement use than the other groups. Crossbred cows produced more milk than Nellore cows (P < 0.05). Crossbred cows presented greater (P < 0.05) dry matter intake (DMI) than Nellore cows. However, no differences were found (P > 0.05) for nutrient digestibility among genetic types. It can be concluded that strategies of supplementation that present an equitable distribution of supplement provides greater weight gain in suckling female beef calves. Crossbred cows produce more milk and present greater DMI than Nellore cows. There are no differences in the nutrient digestibility between Nellore and Nellore × Holstein crossbred cows.