Intake, performance, and feeding behavior of Holstein and Holstein × Gyr heifers grazing intensively managed tropical grasses during the rainy season.

Holstein × Gyr and Holstein are the primary dairy breeds used in tropical systems, but when rearing under pasture, feed intake, behavior, and performance might differ between them. This study aimed to evaluate the voluntary intake, nutrient digestibility, performance, and ingestive behavior of Holstein and Holstein × Gyr (½ Holstein × ½ Gyr) heifers managed in a rotational system of Guinea grass (Panicum maximum Jacq. cv. Mombaça). The experiment was conducted during the summer season throughout four periods of 21 d. Two 8-heifers (four Holstein and four Holstein × Gyr) groups, averaging 258.6 ±â€¯24.79 kg and 157.1 ±â€¯24.99 kg BW, were used. Each group grazed a separate set of 16 paddocks, and all heifers received a concentrate supplement daily. Heifers were weighed at the beginning and end of the experiment. Fecal, forage and concentrate samples were evaluated for their DM, CP, crude fat, ash, NDF, and indigestible NDF. Feeding behavior was evaluated through 24 h of live observation for 48 h of each experimental period. Grazing, ruminating, resting, and intake of concentrate times were recorded, and rumination criteria, bout criteria, mealtime, meal frequency, and meal duration were calculated. There was no difference in total dry matter intake (DMI), but forage DMI of Holstein × Gyr was 11.70 % greater than the Holstein heifers. The Holstein × Gyr heifers had greater NDF intake and feed efficiency tended to show greater CP and NDF digestibilities, consequently, they had greater average daily gain (ADG). Holstein grazed less than Holstein × Gyr heifers in the afternoon. Ruminating time was 18.43 % lower for Holstein than Holstein × Gyr heifers, and rumination criteria (i.e. longest non-feeding interval within a rumination event) were greater for Holstein heifers. Holstein heifers presented more prolonged rumination bouts and resting time than Holstein × Gyr heifers. Holstein × Gyr can ingest and ruminate greater amounts of fibrous material, and Holstein heifers needed to spend more time ruminating the cud. Overall, even though the behavior was not markedly different between breeds, rearing young Holstein heifers in tropical pasture conditions is less suitable than Holstein-Gyr because of their lower ADG. Therefore, this management condition seems appropriate for Holstein × Gyr but inappropriate for Holstein dairy heifers.

Performance of crossbred lactating cows at grazing in response to nitrogen supplementation and different levels of concentrate feed / Desempenho de vacas mestiças leiteiras a pasto em resposta à suplementação nitrogenada e a diferentes níveis de concentrado

The performance of crossbred (1/2 Holstein x Zebu) cows supplemented on Brachiaria decumbens pasture during the wet-dry transition period was evaluated. Eight cows with 497±50kg, during third and fourth lactations and after the lactation peak were distributed in two 4 x 4 Latin squares. The treatments consisted of a factorial with two types of mineral supplements (nitrogenous and mineral salt) and two levels of concentrate (0.3 and 0.6% body weight (BW)/cow/day), based on corn and soybean meal (60:40), and supplied during the morning and afternoon milking. The experiment lasted 56 days, divided into four periods of 14 days, with seven days for adaptation and seven for data collection. No interaction (P> 0.05) was observed between the supplements and the concentrate levels. The nitrogenous salt and the highest concentrate level increased (P< 0.05) the intake of crude protein, and the highest concentrate level increased (P< 0.05) the intake of non-fibrous carbohydrates and the digestibility of crude protein. No effect (P> 0.05) of supplement and concentrate level was observed on the milk constituents and feed efficiency. Grazing crossbred after the lactation peak during the wet-dry transition period achieve the productive potential with 0.3% BW of concentrate per day and mineral salt.(AU)

Foi avaliado o desempenho de vacas mestiças (1/2 Holandês x Zebu) suplementadas em pastagens de Brachiaria decumbens durante o período de transição águas-seca. Oito vacas com 497±50kg, durante a terceira e a quarta lactação e após o pico de produção, foram distribuídas em dois quadrados latinos 4 x 4. Os tratamentos consistiram de um fatorial com dois tipos de suplementos (sal nitrogenado e sal mineral) e dois níveis de concentrado (0,3 e 0,6% do peso corporal (PC)/vaca/dia), baseado em milho e farelo de soja (60:40) e suprido durante as ordenhas da manhã e da tarde. O experimento durou 56 dias, divididos em quatro períodos de 14 dias, sendo sete dias para adaptação e sete para coletas. Não foi encontrada interação (P>0,05) entre os suplementos e os níveis de concentrado. O sal nitrogenado e o maior nível de concentrado aumentaram (P<0,05) o consumo de proteína bruta, e o maior nível de concentrado aumentou (P<0,05) o consumo de carboidratos não fibrosos e a digestibilidade da proteína bruta. Não foi observado efeito (P>0,05) de suplemento e de nível de concentrado sobre os componentes do leite e a eficiência alimentar. Vacas mestiças após o pico de lactação durante o período de transição águas-seca alcançam seu potencial produtivo com 0,3% do PC/dia de concentrado e sal mineral.(AU)

Effects of soybean oil supplementation on performance, digestion and metabolism of early lactation dairy cows fed sugarcane-based diets.

Sugarcane is an important forage source for dairy cows in tropical countries. However, it provides limited digestible fiber and energy intake, and fat supplementation can be a way to increase energy density and decrease dietary, non-fiber carbohydrates concentrations. We aimed to evaluate the performance, digestion and metabolism of dairy cows in early lactation fed different concentrations of soybean oil (SBO) in sugarcane-based diets. Fourteen primiparous (545±17.2 kg of BW) and eight multiparous (629±26.7 kg BW) Holstein dairy cows were used according to a randomized block design. After calving, diets were randomly assigned to cows within the two parity groups. Diets were formulated with increasing concentrations of SBO (g/kg dry matter (DM)): control (0), low (LSBO; 15.7), medium (MSBO; 44.3) and high (HSBO; 73.4). The study was performed from calving until 84 days in milk, divided into three periods of 28 days each. Dry matter intake (DMI) was affected quadratically in response to SBO addition with the greatest and lowest values of 19.0 and 16.0 kg/day for LSBO and HSBO diets, respectively. The digestibility of potentially digestible NDF was quadratically affected by SBO with the greatest value of 623 g/kg for LSBO diet. Both milk and energy-corrected milk (ECM) production were quadratically affected by SBO inclusion, with greatest ECM values of 27.9 and 27.3 for LSBO and MSBO, respectively. Soybean oil inclusion linearly decreased milk fat concentration by 13.2% from control to HSBO. The CLA t10,c12-18:2 was observed in milk fat only for MSBO and HSBO diets. Soybean oil inclusion did not affect plasma glucose or serum concentrations of total proteins, globulins, albumin, urea nitrogen, beta-hydroxybutyrate, non-esterified fatty acids or insulin. Serum concentrations of total cholesterol, triglycerides and low-density lipoprotein increased with SBO supplementation. Soybean oil inclusion in sugarcane-based diets for early lactation dairy cows from 15.7 to 44.3 g/kg DM can improve energy intake and performance; however, at 44.3 g/kg DM milk fat concentration and ECM decreased. Soybean oil inclusion at 73.4 g/kg DM adversely affected energy intake, fiber digestion and performance of early lactation dairy cows and is not recommended.

Energy and protein requirements for growth of Holstein × Gyr heifers.

There is little information regarding the nutritional requirements for dairy heifers, leading the majority of nutrient requirement systems to consider dairy heifers to be similar to beef heifers. Therefore, we evaluated the muscle protein metabolism and physical and chemical body composition of growing Holstein × Gyr heifers and estimated the energy and protein requirements. We performed a comparative slaughter experiment with 20 Holstein × Gyr heifers at an initial body weight of 218 ± 36.5 kg and an average age of 12 ± 1.0 months. Four heifers were designated as the reference group, and the 16 remaining heifers were fed ad libitum. The 16 heifers were distributed using a completely randomized design in a 2 × 2 factorial arrangement with two roughages (corn silage or sugarcane) and two concentrate levels (30 or 50%) for 112 days. Greater (p < 0.05) values for fractional rates of muscle protein synthesis, degradation and accretion were observed for heifers that were fed 50% concentrate. The following equations were obtained to estimate the net energy for gain (NEg ) and net protein for gain (NPg ): NEg (Mcal/day) = 0.0685 × EBW0.75  × EBWG1.095 and NPg (g/day) = 203.8 × EBWG - 14.80 × RE, respectively, in which EBW is the empty body weight, EBWG is the empty body weight gain and RE is the retained energy. We concluded that increased rates of protein turnover are achieved when a greater quality diet is provided. In the future, these results can be used to calculate the nutritional requirements for growth of Holstein × Gyr heifers after equation validation rather than using the recommendations provided by other systems, which use values developed from beef heifers, to determine the nutritional requirements of dairy cattle.

Supplementation of grazing beef cows during gestation as a strategy to improve skeletal muscle development of the offspring.

The appropriate supply of nutrients in pregnant cows has been associated with the optimal development of foetal tissues, performance of their progeny and their meat quality. The aim of this study was to evaluate supplementation effects of grazing cows in different stages of gestation on skeletal muscle development and performance of the progeny. Thereby, 27 Nellore cows were divided into three groups (n=9 for each group) and their progeny as follows: UNS, unsupplemented during gestation; MID, supplemented from 30 to 180 days of gestation; LATE, supplemented from 181 to 281 days of gestation. The percentage composition of the supplement provided for the matrices was the following: ground corn (26.25%), wheat bran (26.25%) and soya bean meal (47.5%). The supplement was formulated to contain 30% CP. Supplemented matrices received 150 kg of supplement (1 and 1.5 kg/day for cows in the MID and LATE groups, respectively). After birth, a biopsy was performed to obtain samples of skeletal muscle tissue from calves to determine number and size of muscle fibres and for messenger RNA (mRNA) expression analysis. The percentage composition of the supplement provided for the progeny was the following: ground corn grain (30%), wheat bran (30%), soya bean meal (35%) and molasses (5%). The supplement was formulated to contain 25% CP and offered in an amount of 6 g/kg BW. Performance of the progeny was monitored throughout the suckling period. Means were submitted to ANOVA and regression, and UNS, MID and LATE periods of supplementation were compared. Differences were considered at P0.10). Similarly, no differences were observed between calves for nutrient intake (P>0.10). However, greater subcutaneous fat thickness (P=0.006) was observed in the calves of LATE group. The ribeye area (P=0.077) was greater in calves born from supplemented compared with UNS cows. The supplementation of pregnant cows did not affect the muscle fibre size of their progeny (P=0.208). On the other hand, calves born from dams supplemented at mid-gestation had greater muscle fibre number (P=0.093) compared with calves from UNS group. Greater mRNA expression of peroxysome proliferator-activated receptor α (P=0.073) and fibroblast growth factor 2 (P=0.003) was observed in the calves born from MID cows. Although strategic supplementation did not affect the BW of offspring, it did cause changes in carcass traits, number of myofibres, and mRNA expression of a muscle hypertrophy and lipid oxidation markers in skeletal muscle of the offspring.

Reducing mineral usage in feedlot diets for Nellore cattle: I. Impacts of calcium, phosphorus, copper, manganese, and zinc contents on microbial efficiency and ruminal, intestinal, and total digestibility of dietary constituents.

This study evaluated intake, microbial efficiency, and ruminal, small and large intestinal, and total digestibility of DM, OM, CP, and NDF, as well as availability of Ca, P, Mg, Na, K, Cu, Mn, and Zn in Zebu cattle fed with or without supplemental sources of Ca and P or a micromineral premix. Five rumen- and ileum-cannulated Nellore bulls (BW = 200 ± 10.5 kg; 9 mo) were used in the experiment, distributed in a 5 × 5 Latin square design. The experiment was developed in a 2 × 2 + 1 factorial design to measure the effects of mineral supplementation on intake, digestibility, and site of nutrient absorption. The factors consisted of 2 Ca and P levels (macromineral factor; CaP+ or CaP-) and 2 microminerals levels (micromineral factor; CuMnZn+ or CuMnZn-). In addition, a treatment with alimentary restriction (REST) was evaluated at 1.7% of BW. Nutrient fluxes were measured in the omasum and ileum, in addition to intake and fecal excretion. Microbial efficiency was estimated using purine derivative excretion. Dry matter, OM, NDF, CP intake, and total digestibility were not affected ( ≥ 0.058) by the absence of Ca, P, Cu, Mn, and Zn supplementation. Intake of Ca, P, and Mg were reduced ( < 0.01) by CaP-. The absence of CuMnZn reduced ( < 0.01) Cu, Mn, and Zn intake. Ruminal recycling of P, Na, and K is significant for increasing the influx of these minerals to the digestive tract; however, influences of treatments were not observed. The small and large intestines contributed to mineral absorption in different proportions ( < 0.05), according to minerals and treatments. Because of the similarity ( > 0.05) of OM, NDF, and CP digestion sites and coefficients, we assume that omitting supplemental sources of Ca, P, Cu, Mn, and Zn may be an option in raising cattle on feedlots. If supplementation is viable, knowledge about the specific absorption site of each mineral could positively impact choices about the supplemental source.

Estimating mineral requirements of Nellore beef bulls fed with or without inorganic mineral supplementation and the influence on mineral balance.

The objectives of this study were to quantify the mineral balance of Nellore cattle fed with and without Ca, P, and micromineral (MM) supplementation and to estimate the net and dietary mineral requirement for cattle. Nellore cattle ( = 51; 270.4 ± 36.6 kg initial BW and 8 mo age) were assigned to 1 of 3 groups: reference ( = 5), maintenance ( = 4), and performance ( = 42). The reference group was slaughtered prior to the experiment to estimate initial body composition. The maintenance group was used to collect values of animals at low gain and reduced mineral intake. The performance group was assigned to 1 of 6 treatments: sugarcane as the roughage source with a concentrate supplement composed of soybean meal and soybean hulls with and without Ca, P, and MM supplementation; sugarcane as the roughage source with a concentrate supplement composed of soybean meal and ground corn with and without Ca, P, and MM supplementation; and corn silage as the roughage source with a concentrate supplement composed of soybean meal and ground corn with and without Ca, P, and MM supplementation. Orthogonal contrasts were adopted to compare mineral intake, fecal and urinary excretion, and apparent retention among treatments. Maintenance requirements and true retention coefficients were generated with the aid of linear regression between mineral intake and mineral retention. Mineral composition of the body and gain requirements was assessed using nonlinear regression between body mineral content and mineral intake. Mineral intake and fecal and urinary excretion were measured. Intakes of Ca, P, S, Cu, Zn, Mn, Co, and Fe were reduced in the absence of Ca, P, and MM supplementation ( < 0.05). Fecal excretion of Ca, Cu, Zn, Mn, and Co was also reduced in treatments without supplementation ( < 0.01). Overall, excretion and apparent absorption and retention coefficients were reduced when minerals were not supplied ( < 0.05). The use of the true retention coefficient instead of the true absorption coefficient provided a better estimate of mineral requirements. Dietary mineral requirements were lower for P, Cu, and Zn and greater for Fe compared with previously published recommendations. This study provides useful information about mineral requirements and mineral supplementation to obtain adequate dietary mineral supply of Nellore cattle in tropical conditions.

Effect of the addition of ß-mannanase on the performance, metabolizable energy, amino acid digestibility coefficients, and immune functions of broilers fed different nutritional levels.

Three experiments were conducted to evaluate the effect of ß-mannanase BM: supplementation on the performance, metabolizable energy, amino acid digestibility, and immune function of broilers. A total of 1,600 broilers were randomly distributed in a 4 × 2 factorial arrangement (4 nutritional levels × 0 or 500 g/ton BM), with 10 replicates and 20 broilers per pen. The same design was used in the energy and digestibility experiments with 8 and 6 replicates, respectively, and 6 broilers per pen. The nutritional levels : NL : were formulated to meet the nutritional requirements of broilers : NL1 : ; reductions of 100 kcal metabolizable energy : NL2 : ; 3% of the total amino acids (NL3); and 100 kcal metabolizable energy and 3% total amino acids (NL4) from NL1. The serum immunoglobulin (Ig) concentration was determined in two broilers per pen, and these broilers were slaughtered to determine the relative weight of spleen, thymus, and bursa of Fabricius. Throughout the experiment, the lower nutritional levels reduced (P < 0.05) body weight gain : BWG : and increased (P < 0.05) feed conversion : FCR : for the NL4 treatment. The BM increased (P < 0.05) the BWG values and improved (P < 0.05) the FCR of the broilers. The apparent metabolizable energy corrected for nitrogen balance (AMEn) values were reduced (P < 0.05) for NL2 and NL3. The BM increased (P < 0.05) the AMEn values and reduced (P < 0.05) the excreted nitrogen. NL3 and NL4 reduced (P < 0.05) the true ileal digestibility coefficients (TIDc) of the amino acids cystine and glycine, and BM increased (P < 0.05) the TIDc for all amino acids. The addition of BM reduced (P < 0.05) the relative weights of the spleen and bursa. NL2 increased (P < 0.05) the Ig values, whereas BM reduced (P < 0.05) the serum IgA, IgG, and IgM values of the broilers. This study indicates that using suboptimal nutrient levels leads to losses in production parameters, whereas BM-supplemented diets were effective in improving performance, energy values, and TIDc levels of amino acids and immune response of broilers.

Effects of varying ruminally undegradable protein supplementation on forage digestion, nitrogen metabolism, and urea kinetics in Nellore cattle fed low-quality tropical forage.

Effects of supplemental RDP and RUP on nutrient digestion, N metabolism, urea kinetics, and muscle protein degradation were evaluated in Nellore heifers () consuming low-quality signal grass hay (5% CP and 80% NDF, DM basis). Five ruminally and abomasally cannulated Nellore heifers (248 ± 9 kg) were used in a 5 × 5 Latin square. Treatments were the control (no supplement) and RDP supplementation to meet 100% of the RDP requirement plus RUP provision to supply 0, 50, 100, or 150% of the RUP requirement. Supplemental RDP (casein plus NPN) was ruminally dosed twice daily, and RUP supply (casein) was continuously infused abomasally. Jugular infusion of [NN]-urea with measurement of enrichment in urine was used to evaluate urea kinetics. The ratio of urinary 3-methylhistidine to creatinine was used to estimate skeletal muscle protein degradation. Forage NDF intake (2.48 kg/d) was not affected ( ≥ 0.37) by supplementation, but supplementation did increase ruminal NDF digestion ( < 0.01). Total N intake (by design) and N retention increased ( < 0.001) with supplementation and also linearly increased with RUP provision. Urea entry rate and gastrointestinal entry rate of urea were increased by supplementation ( < 0.001). Supplementation with RUP linearly increased ( = 0.02) urea entry rate and tended ( = 0.07) to linearly increase gastrointestinal entry rate of urea. Urea use for anabolic purposes tended ( = 0.07) to be increased by supplementation, and RUP provision also tended ( = 0.08) to linearly increase the amount of urea used for anabolism. The fraction of recycled urea N incorporated into microbial N was greater ( < 0.001) for control (22%) than for supplemented (9%) heifers. Urinary 3-methylhistidine:creatinine of control heifers was more than double that of supplemented heifers ( < 0.001). Control heifers reabsorbed a greater ( < 0.001) fraction of urea from the renal tubule than did supplemented heifers. Overall, unsupplemented heifers had greater mobilization of AA from myofibrillar protein, which provided N for urea synthesis and subsequent recycling. Supplemental RUP, when RDP was supplied, not only increased N retention but also supported increased urea N recycling and increased ruminal microbial protein synthesis.

Desempenho de vacas mestiças em função de suplementação energética e proteica em dietas à base de silagem de milho / Performance of crossbred cows as a result of energetic and protein supplementation in corn silage based diets

Objetivou-se avaliar níveis de concentrados energéticos e proteicos sobre o desempenho de vacas leiteiras Holandês x Zebu, com peso corporal de 452±77kg, de terceira e quarta lactação, 80 dias pós-parto e produção de 12,8kg de leite/dia. Nove vacas foram distribuídas em três quadrados latinos 3x3, em períodos experimentais de 10 dias, distribuídas segundo número de lactações, sendo os tratamentos níveis de farelo de soja (FS) em substituição ao fubá de milho (FM) (0,8; 1,6 e 2,4kg/vaca dia, completando para 3,2kg/vaca dia com FM), níveis de FS ou de FM (0,8; 1,6 e 3,2kg/vaca/dia) e silagem de milho como volumoso. Somente o consumo de proteína bruta se elevou com o aumento nos níveis de FS em dietas contendo FM+FS, ao passo que os consumos diários de matéria seca (MS) e das frações nutricionais aumentaram com a elevação do FS ou FM. Os coeficientes de digestibilidade da MS e dos nutrientes não diferiram em dietas contendo FM+FS. A digestibilidade da proteína bruta (PB) aumentou ao passar de 1,6 para 3,2kg/dia de FS. Houve diminuição da digestibilidade da MS, MO e CNF ao passar de 0,8 para 3,2kg/dia de FM e diminuição do NDT ao passar de 1,6 para 3,2kg/dia de FM. As exigências de NDT e PB só foram satisfeitas plenamente com 0,8+2,4kg (FM+FS) e 3,2kg de FS. As dietas contendo FM não atenderam sequer às exigências de NDT. A produção de leite e a sua composição bem como o peso corporal e a eficiência alimentar relacionada ao CMS não foram influenciados pelos tratamentos. A eficiência alimentar em relação ao fornecimento de concentrado decresceu quando se adicionaram níveis crescentes de FS ou FM. Tendo como volumoso a silagem de milho, o fornecimento de fubá de milho ou farelo de soja, nas quantidades analisadas neste experimento, não promove aumento da produção de leite ou de seus constituintes, sendo que a eficiência do uso do concentrado diminui ao se elevar o nível de suplementação.

The aim was to evaluate levels of energy and protein concentrates on performance of crossbred Holstein x Zebu dairy cows, with body weight of 452 ± 77kg, third and fourth lactation, 80 days post-partum and with a production of 12.8kg of milk per day. Nine cows were distributed in three 3 x 3 Latin squares, with experimental periods of 10 days, distributed according to the number of lactations, with treatment levels of soybean meal (SBM) replacing corn meal (CM) (0.8; 1.6 and 2.4kg/cow/day completing 3.2kg/cow/day with CM); CM or SBM levels (0.8; 1.6 and 3.2kg/cow/day) and corn silage as forage. Only crude protein consumption rose with the increase in levels of SBM in diets containing CM + SBM, while the daily consumption of dry mass (DM) and the nutrient fractions increased with the elevation of CM or SBM. The coefficients of digestibility of DM and nutrients did not differ in diets containing CM + SBM. The crude protein (CP) digestibility increased when changing from 1.6 to 3.2kg/day of SBM. There was reduction of digestibility of DM, OM, and NFC when passing from 0.8 to 3.2kg/day of CM and decrease of TDN when changing from 1.6 to 3.2kg/day of CM. The requirements for TDN and CP were only fully satisfied fully in diets containing 0.8+2.4kg (CM+SBM) and 3.2kg of SBM. Diets containing CM did not attend even the demands of TDN. Milk production and composition, as well as the body weight and food efficiency related to the DMI were not influenced by the treatments. Feed efficiency in relation to the supply of concentrate decreased when increasing levels of CM or SBM were added. Having corn silage as forage, the supply of corn meal or soybean meal in quantities analyzed in this experiment does not promote increase in production of milk or their constituents, and the efficiency of the use of concentrate decreases when raising the level of supplementation.

Efeito da somatotropina bovina recombinante (rBST) sobre o desempenho produtivo e reprodutivo de vacas da raça Holandesa / Effect of recombinant bovine somatotropin (rBST) on productive and reproductive performance of Holstein cows

Avaliaram-se os efeitos da aplicação de rBST sobre o desempenho produtivo e reprodutivo de vacas da raça Holandesa no início da lactação. Foram avaliadas 41 vacas, dos 60 aos 150 dias de lactação, distribuídas em um delineamento inteiramente ao acaso, em três tratamentos: 1- sem aplicação de rBST (controle); 2- aplicação de rBST 60 dias após o parto (rBST-60); 3- aplicação de rBST 100 dias após o parto (rBST-100). A aplicação de rBST aumentou a produção de leite e a produção de leite corrigida a 4 por cento de gordura em 14,0 e 13,2 por cento, respectivamente, quando administrada aos 60 dias pós-parto. Não se observou efeito da aplicação de rBST sobre a porcentagem e a produção de gordura do leite nem sobre o período de serviço, número de serviços por concepção e taxa de gestação aos 150 dias de lactação. O uso do rBST também não afetou o ganho de peso dos animais durante o período avaliado. A aplicação de rBST aos 60 dias de lactação proporcionou maiores pico de produção e persistência da lactação, sem, no entanto, influenciar o desempenho reprodutivo. A aplicação de rBST aos 100 dias de lactação não aumentou a produção de leite e o desempenho reprodutivo das vacas.

Efeito da condição corporal ao parto sobre a produção e composição do leite, a curva de lactação e a mobilização de reservas corporais em vacas da raça Holandesa / Effects of body condition at calving on milk yield and composition, lactation curve and body reserve mobilization of Holstein cows

Avaliaram-se os efeitos do escore da condição corporal ao parto sobre a produção e composição do leite, a curva de lactação e o padrão de mobilização de reservas corporais em vacas da raça Holandesa. Foram utilizadas 51 vacas, sendo 13 primíparas e 38 multíparas, distribuídas em delineamento inteiramente ao acaso, segundo a ordem de partos - primíparas e multíparas - e a classe de escore da condição corporal ao parto (ECCP) - classe 1 ECCP igual ou superior a 3,25, e classe 2 ECCP igual ou inferior a 3,0. Para avaliar o padrão de mobilização de reservas corporais, foram formados grupos de vacas em função do ECCP e do nível de produção de leite. Nas primíparas, não foram observados efeitos da ECCP sobre a produção e a composição do leite e sobre a curva da lactação, exceto para porcentagem de gordura. Nas multíparas, as vacas da classe 1 produziram mais leite e mais componentes do leite, e a curva da lactação mostrou pico de produção mais alto. As vacas de maior ECCP e maior produção de leite apresentaram padrão de mobilização de reservas corporais mais acentuado no início da lactação e maior peso corporal no pré-parto e ao parto. O peso corporal e a mudança de peso corporal ao parto e no início da lactação não foram influenciados pelo escore de condição corporal ao parto e pela produção de leite.