Effects of increased doses of lysine in a rumen-protected form on plasma amino acid concentration and lactational performance of dairy cows fed a lysine-deficient diet.

The objective of these studies was to determine the effects of feeding a novel rumen-protected Lys (RP-Lys) product on plasma AA, lactational performance, and Lys bioavailability. To evaluate RP-Lys on lactation performance a corn-based diet (42.5% of corn silage and 21.9% of corn and corn by-products, on DM basis) was formulated to be Lys deficient but adequate in Met, energy, and metabolizable protein. Thirty-six lactating Holstein cows were fed either a Lys-deficient control diet (CON) with no added RP-Lys, or diets containing 0.3% of RP-Lys (0.3RP-Lys) or 0.6% of RP-Lys (0.6RP-Lys) for 8 wk. There were no effects on dry matter intake (mean ± SD; 26.1 ± 0.58 kg/d), milk yield (37.9 ± 0.72 kg/d), or milk composition to the RP-Lys supplementation. No effect was observed on plasma AA concentrations except for His. Plasma His was linearly reduced by Lys feeding (42.6, 41.2, 30.0 ± 4.09 µM, for CON, 0.3RP-Lys, and 0.6RP-Lys, respectively). Calculated efficiency of Lys utilization decreased linearly with RP-Lys supplementation. In the companion study, 3 rumen-cannulated lactating dairy cows were used in a 3 × 3 Latin square design to assess the bioavailability of the RP-Lys. Free Lys (HCl-Lys), RP-Lys, and water were administered separately by postruminal bolus dosing. The Lys bioavailability was assessed by the ratio of area under the curve of Lys plasma concentration for RP-Lys compared with HCl-Lys and discounted for the area under the curve for water bolus dose. The estimated bioavailability of the RP-Lys was 24.4% ± 4.61. In summary, increased supplemental doses of Lys had no effect on Lys plasma concentration and lactational performance when fed to dairy cows on a corn-based diet, although altered Lys as % of essential AA was observed. However, the lack of effects should be considered in light of the lower-than-expected bioavailability of the RP-Lys.

Postruminal protein supply upregulates hepatic lysine oxidation and ornithine transcarbamoylase in lactating dairy cattle.

Metabolizable protein supply is a limiting factor for milk production in dairy cows, and the availability of AA is a function of the quantity of the metabolizable protein available and of hepatic AA catabolism. This study aimed to evaluate the effect of postruminal protein infusion on key genes for ureagenesis and AA catabolism. Six multiparous Holstein cows in early lactation were used in a replicated crossover design. Cows were fed a TMR and infused postruminally with either 0 or 600 g/d of milk protein isolate. Periods were 21 d long, consisting of 14 d of adjustment to surroundings, followed by 7 d of protein infusion. On the last day of each infusion, liver samples were collected for mRNA analysis and explant culture, milk samples were collected for mRNA analysis, and blood samples were collected for plasma metabolite analysis. Postruminal infusion of protein increased milk yield by 10.5%, milk fat yield by 12.5%, milk protein yield by 20%, milk lactose yield by 11%, and total solids yield by 15.5%. Postruminal infusion of protein increased milk urea N by 23.5%, blood urea N by 18.6%, and the abundance of hepatic ornithine transcarbamoylase mRNA by 52.8%. Postruminal infusion of protein did not alter the mRNA abundance of hepatic argininosuccinate synthase, α-aminoadipate semialdehyde synthase, cysteine sulfinic acid decarboxylase, or cystathionase. The abundance of RNA for milk proteins was unchanged with postruminal protein infusion. Metabolism of l-[U 14C] Lys to CO2 was increased by 127% (0.143 vs. 0.063 ± 0.04 nmol product·mg tissue-1·h-1), and the metabolism of l-[U 14C] Ala to CO2 increased by 40.5% (0.52 vs. 0.37 ± 0.06 nmol product·mg tissue-1·h-1) with postruminal protein infusion. The rate of l-[1-14C] Met oxidation did not differ. These data indicate increased ureagenesis matched by upregulation of nonessential AA catabolism and a disproportional increase in Lys oxidation in response to increased postruminal protein infusion.

Relationship between feed efficiency indexes and thermography, blood, and ruminal parameters in pre-weaning dairy heifers.

The objective of this study was to evaluate whether pre-weaning heifer calves divergent for residual feed intake (RFI) or residual feed intake and body weight gain (RIG) exhibit differences in thermography, blood, and ruminal parameters. Thirty-two Gyr heifer calves were enrolled in a 63-d trial and classified into 2 feed efficiency (FE) groups based on RFI and RIG (mean ± 0.5 SD). The groups were classified as high efficiency (HE) RFI (HE RFI, n = 9), HE RIG (HE RIG, n = 10), low efficiency (LE) RFI (LE RFI, n = 10), and LE RIG (LE RIG, n = 11). The amount of whole milk provided for each calf was calculated based on their metabolic weight at birth (42% x BW0.75). The liquid diet was divided into two meals at 0700 and 1400 h. The total solid diet (TSD) was composed of 92% concentrate and 8% of Tifton 85 hay chopped in 5-cm lengths, as fed. Intake was measured daily. Blood concentrations of insulin, beta hydroxybutyrate, urea, and glucose, and ruminal pH, N-NH3, and volatile fatty acids (VFA) were evaluated at 14, 28, 42, 56, and 70 days of age. Thermal images of the calves were taken with an infrared camera (FLIR T420, FLIR Systems Inc., Wilsonville, OR) on d 56 (±3) at 0600 h, before the morning feeding. Total VFA concentration and propionate as % of total VFA were 24.2% and 22.2% lower in HE RFI compared to LE RFI calves, respectively. On the other hand, acetate as % of total VFA was 10.6% greater in HE RFI than LE RFI calves. Blood urea concentration tended to be greater in LE RFI than HE RFI calves. High efficiency HE RIG tended to have 6.8% greater acetate and 15.4% lower propionate as % of total VFA than LE RIG. Blood insulin concentration was greater and blood glucose tended to be greater for LE RIG than HE RIG group. Low efficiency RIG group had greater left rib, left flank, and anus surface temperature measured by infrared thermography than the HE RIG group. Differences in ruminal fermentation do not seem to be associated with pre-weaning calves efficiency, while differences in protein metabolism seem to affect RFI during this phase. Infrared thermography appears to be correlated to RIG in pre-weaning heifer calves.

Short communication: Effect of glucose infusion dose and stage of lactation on glucose tolerance test kinetics in lactating dairy cows.

The objective for this study was to determine the effect of glucose dose and days following peak milk yield on plasma glucose, serum insulin, and plasma nonesterified fatty acids (NEFA) kinetics during an intravenous glucose tolerance test (IVGTT) in lactating dairy cattle. Six lactating Holstein dairy cows (3 primiparous and 3 multiparous) were assigned to 2 squares and received 0.092, 0.15, or 0.3 g of glucose/kg of body weight (BW) during an IVGTT at 74 and 221 d in milk (DIM), representing early (post-peak) lactation and mid lactation, respectively. Treatments were applied in a replicated Latin square design using contiguous 7-d periods within each stage of lactation. Milk production and dry matter intake were determined daily during the first 6 d of each period. The IVGTT was performed on d 7. For the IVGTT, cows were prepared with indwelling catheters in each jugular vein, and blood samples were collected at -15, -10, 5, 10, 15, 20, 30, 45, 60, 90, and 120 min relative to the glucose infusion. Samples were analyzed for plasma glucose, serum insulin, and plasma NEFA concentrations. Increasing the glucose dose during the IVGTT increased plasma glucose area under the curve (AUC), decreased glucose half-life, and increased maximal plasma glucose concentrations in plasma during the IVGTT. Greater glucose dose during the IVGTT elevated serum insulin AUC and increased nadir NEFA concentrations. Maximal plasma glucose concentration during the IVGTT was lower, whereas maximum NEFA concentration, NEFA AUC, and NEFA clearance rate were greater at 74 than at 221 DIM. Only glucose half-life was responsive to stage of lactation × glucose dose effects during the IVGTT, and the decrease in glucose half-life with increasing glucose dose was greater at 74 than at 221 DIM. Glucose AUC was greater and NEFA AUC lower for cows at 74 than at 221 DIM. For the doses tested, a glucose dose greater than 0.092 g/kg of BW resulted in peak blood glucose concentration that exceeded the previously reported renal glucose excretion threshold of 8.3 mM. There is a need for accompanying data to determine if this is the case for the glucose doses evaluated in this experiment. Based on maximal peak glucose concentrations and effects on glucose half-life, we identify 0.092 g of glucose/kg of BW (0.46 g/kg of metabolic body weight) as the preferred dose for the IVGTT for cows at 74 and 221 DIM in this study.

Supplementation with different non-fiber carbohydrate sources in dairy cow diets with high or low rumen-undegradable protein content / Suplementação com diferentes fontes de carboidratos não fibrosos em dietas para vacas leiteiras com alto ou baixo teor de proteína não degradável no rúmen

The objective for this study was to evaluate the supplementation with different non-fibrous carbohydrate (NFC) sources for grazing dairy cows in diets with high or low concentrations of rumen undegradable protein (RUP). Twelve multiparous cows averaging 30kg/d of milk production and 45±23 days in milk in a 4x4 Latin square design with 2 × 2 factorial arrangement were used. The difference in NFC content of the diets was achieved using ground corn (GC) or dried citrus pulp (DCP). Dietary RUP was altered by the partial replacement of soybean meal (LRUP) by roasted whole soybean and corn gluten meal (HRUP). Greater dry matter intake (DMI) was observed in DCP treatments compared to GC treatments (19.2 and 17.7kg/day of DM, respectively). Milk fat concentration was lower for LRUP treatments (3.4%) when compared to HRUP (3.6%). The milk protein concentration was greater for GC treatments (2.9%) in relation to DCP treatments (2.8%). Lower milk ureic nitrogen was observed when DCP diets were fed compared to those with GC (17.8 and 21.2mg/dL, respectively). The use of DCP as CNF source increased dry matter intake as well as milk fat concentration, although no differences in milk production were observed for RUP level.(AU)

Objetivou-se avaliar a suplementação com diferentes fontes de carboidratos não fibrosos (CNF) em vacas manejadas a pasto em dietas com alta ou baixa concentração de proteína não degradável no rúmen (PNDR). Doze vacas multíparas com média de 30kg leite/ dia e 45±23 dias em lactação foram utilizadas em delineamento quadrado latino 4x4 com arranjo fatorial 2 × 2. As fontes de CNF foram milho moído (MM) e polpa cítrica seca (PC). A PNDR da dieta foi alterada pela substituição parcial do farelo de soja da dieta de baixa PNDR (BPNDR) por grão de soja tostado e farelo de glúten de milho dieta de alta PNDR (APNDR). Foi observado maior consumo de matéria seca (CMS) nos tratamentos com PC quando comparado aos tratamentos com MM (19,2 e 17,7kg / dia de MS, respectivamente). O teor de gordura do leite foi menor para os tratamentos com BPNDR (3,4%) em comparação aos tratamentos com APNDR (3,6%). O teor de proteína do leite foi maior nos tratamentos com MM (2,9%) em relação aos tratamentos com PC (2,8%). Foram observados menores teores de nitrogênio ureico no leite dos animais alimentados com PC em relação aos com MM (17,8 e 21,2mg / dL, respectivamente). O uso de PC como fonte de CNF aumentou o consumo de matéria seca, bem como o teor de gordura do leite, embora não tenham sido observadas diferenças na produção de leite relacionada a alteração nos teores de PNDR.(AU)

Virginiamycin and sodium monensin supplementation for beef cattle on pasture / Suplementação com virginiamicina e monensina sódica para bovinos de corte a pasto

The aim of this paper was to evaluate the effects of including virginiamycin (VM), sodium monensin (MON) or the association (VM+MON) in the energetic mineral supplement, on the intake and performance of beef cattle on pasture. Forty Nellore heifers with 24 months of age and initial body weight (BW) of 251.5±16.6kg, were distributed in four treatments in a randomized block design. Treatments consisted of adding VM, MON or VM+MON to the supplement (CONT). Additive concentrations were defined to reach a dose of 40 to 45mg/100kg BW. The herbage allowance was not a limiting factor for the animals' intake. Supplement intake was lower than expected, with 33.0, 18.8 and 26.3mg per 100kg BW for VM, MON and VM+MON, respectively. Dry matter intake (DMI, mean=2.65% BW) and animal performance were not affected by the inclusion of additives. The average daily gain (ADG) was 0.561kg/animal day-1. The inclusion of additives in energetic mineral supplement does not affect the DMI and the ADG of grazing animals. The variability in supplement intake and daily dose intake of additives may have influenced the performance of the animals. Monensin inclusion presented the less expensive supplementation cost, due to reduction in supplement intake without changing weight gain.(AU)

Objetivou-se avaliar o efeito da inclusão dos aditivos virginiamicina (VM), monensina sódica (MON) e associação (VM+MON) no suplemento energético-mineral sobre o consumo e desempenho de bovinos manejados em pastagem de Urochloa Brizantha cv. Marandu. Foram utilizadas 40 novilhas Nelore com 24 meses de idade e peso corporal (PC) inicial médio de 251,5+16,6kg distribuídas em delineamento em blocos ao acaso com quatro tratamentos. Os tratamentos consistiam de suplemento energético-mineral (CONT) acrescido de VM, MON ou VM+MON. A oferta de forragem não limitou o consumo dos animais. O consumo dos aditivos foi de 0; 33,0; 18,8 e 26,3mg por 100kg de PC para CONT, VM, MON e VM+MON, respectivamente. O consumo de matéria seca e o desempenho dos animais não foram afetados pela inclusão dos aditivos. O ganho médio diário dos animais foi de 0,561kg dia -1 , sem diferença entre os tratamentos. A inclusão de aditivos no suplemento energético-mineral não alterou o CMS e o desempenho dos animais em pastejo. A variabilidade no consumo de suplemento e na dose ingerida dos aditivos pode ter influenciado o desempenho dos animais.(AU)

Frequency of microorganisms isolated at different stages of lactation and milk production loss associated with somatic cell count and to mastitis-causing pathogens / Frequência de microrganismos isolados em diferentes fases da lactação e perda de produção de leite associada à contagem de células somáticas e aos patógenos causadores de mastite

The aim of this study was to evaluate the frequency of isolation of agents causing subclinical mastitis in a herd and to estimate production losses associated with SCC> 200,000cells/mL. Three 7-day interval microbiological cultures were performed in all lactating animals from the same farm that was evaluated from June to July. To evaluate the negative and positive isolation frequencies between the lactation phases, a Chi-square test was performed. Simple linear regressions were performed to evaluate the lactation curve of animals grouped by pathogens isolated from negative cows in the microbiological culture and with SCC <200,000cells/mL. To estimate the production losses between the groups, regression coefficients were used. Results found in this experiment were: Culture-negative cows with SCC ≥ 200,000cells/mL, cows testing positive in milk culture, with SCC <200,000cells/mL and cows testing positive in milk culture, with SCC ≥ 200,000cells/mL. Milk production was -3.5; -0.5 and -4.27kg, respectively, when compared to culture-negative cows with SCC <200,000cells/mL. Cows infected with yeast cells, Coagulase-negative staphylococci (CNS), Staphylococcus aureus and environmental streptococci produced -3.42; -0.5; -0.168 and -2.5kg of milk when compared to culture-negative cows with SCC <200,000cells/mL. SCC indicates an inflammatory reaction in the mammary gland and it is directly associated with milk production losses and with presence of microorganisms in the mammary gland.(AU)

O objetivo deste estudo foi avaliar a frequência de isolamento de agentes causadores de mastite subclínica em um rebanho e estimar as perdas de produção associadas com CCS>200.000 cél./mL. Três cultivos microbiológicos intervalados por sete dias foram realizados em todos os animais em lactação da propriedade avaliada, no período de junho a julho. Para avaliar as frequências de isolamento negativo e positivo entre as fases da lactação, foi realizado um teste de qui-quadrado. Foram realizadas regressões lineares simples para avaliar a curva de lactação dos animais agrupados por patógenos isolados em relação a vacas negativas na cultura microbiológica e com CCS < 200.000 cél./mL. Os coeficientes das regressões foram utilizados para estimar as perdas de produção entre os grupos. Vacas com resultado negativo na microbiologia, mas com CCS ≥ 200.000 cél./mL, positivas na microbiologia com CCS < 200.000 cél./mL e positivas com CCS ≥ 200.000 cél./mL, produziram por dia, respectivamente, -3,5; -0,5 e -4,27kg de leite em relação às vacas negativas com CCS < 200.000 cél./mL. Vacas infectadas com células leveduriformes, Staphylococcus coagulase negativa, Staphylococcus aureus e Streptococcus ambientais produziram, respectivamente, -3,42; -0,5; -0,168 e -2,5kg de leite, comparadas a vacas negativas com CCS < 200.000 cél./mL. A CCS, indicativa de reação inflamatória, encontra-se diretamente associada às perdas de produção de leite, assim como a presença do microrganismo na glândula mamária.(AU)

Factors associated with microbiological and clinical cure of mastitis in dairy cows / Fatores associados à cura microbiológica e clínica da mastite em vacas leiteiras

709 clinical mastitis cases were analyzed and treated with antimicrobial combination cephalexin-neomycin and the anti-inflammatory prednisolone. A sample of milk was collected to perform a microbiological culture before starting the treatment and 14 days later. Somatic cell count (SCC) was obtained from samples collected on the day of the clinical case (D0), 14 days after (D14) and 28 days after (D28). Of the total, 435 (61.4%) at the D0 exhibited growth of microorganisms. Of the isolated agents, 365 (84%) were Gram-positive, and 66 (16%) were Gram-negative. A clinical cure was achieved in 63% of cases. Bacteriological cure occurred in 75% of cases. Only at D28 after the clinical case a significant SCC reduction was verified. The logistic regression for clinical cure showed significant effects for days in milk and parity (P< 0.05). For bacteriological cure, there were significant effects of Log (SCC) D0; clinical cure and quarter affected (P< 0.05). In the principal component analysis, the Temperature-Humidity Index was associated with reduced clinical cure of clinical mastitis cases.(AU)

Setecentos e nove casos clínicos de mastite foram analisados e tratados com combinação antimicrobiana à base de cefalexina-neomicina e o anti-inflamatório prednisolona. Uma amostra de leite foi coletada para realização de cultura microbiológica antes do início do tratamento e 14 dias depois. A contagem de células somáticas (SCC) foi obtida de amostras coletadas no dia do caso clínico (D0), 14 dias após (D14) e 28 dias após (D28). Do total, 435 (61,4%) no D0 apresentaram crescimento de microrganismos, enquanto em 274 (38,6%) não houve crescimento. Dos agentes isolados, 365 (84%) eram Gram-positivos e 66 (16%) eram Gram-negativos. A cura clínica foi alcançada em 63% dos casos. A cura bacteriológica ocorreu em 75% dos casos. Apenas no D28 verificou-se uma redução significativa na SCC. A regressão logística para a cura clínica mostrou efeitos significativos para dias em lactação e paridade (P<0,05). Para a cura bacteriológica, houve efeitos significativos de Log (SCC) D0; cura clínica e quarto afetado (P<0,05). Na análise do componente principal, o índice de temperatura-umidade foi associado com a redução da cura clínica dos casos clínicos da mastite.(AU)

Estimativa das perdas de produção leiteira em vacas mestiças Holandês x Zebu com mastite subclínica baseada em duas metodologias de análise / Comparison of two methodologies to estimate losses of milk production in crossbred Holstein x Zebu cows with sub-clinical mastitis

Contagem de células somáticas (CCS) e produção de leite de vacas mestiças Holandês x Gir foram utilizadas para avaliação da perda de produção de leite estimada por duas metodologias, baseadas na CCS média da lactação total encerrada ou na CCS e nas pesagens de leite em diferentes estágios de lactação. Nas primíparas consideradas com mastite subclínica (CCS ≥ 200.000 células mL-1), a perda de produção na lactação total, avaliada pela CCS média da lactação, foi de 814kg. Para as multíparas, não houve diferença na produção de leite entre vacas com e sem MSC com base na CCS média da lactação. A estimativa avaliada por meio de testes mensais de CCS e pesagens de leite em diferentes estágios de lactação, balanceada pela prevalência de mastite subclínica do mês foi de 917,9kg para primíparas e 1178,9kg para multíparas. A contraposição da produção de leite com a CCS em diferentes estágios da lactação evidenciou maior perda de produção em relação à observação da CCS média da lactação. A perda de produção de leite de vacas baseada na CCS média de toda a lactação foi subestimada quando comparada à contraposição da produção de leite com CCS em diferentes estágios da lactação.(AU)

Somatic cell count (SCC) and milk production of crossbred Holstein x Gir were used to evaluate the estimated loss of milk production two methodologies, based on the average SCC of total closed lactation, or average SCC and weighing milk at different stages of lactation. In primiparous with SCC mL ≥200,000 cells-1 production loss in the total lactation, evaluated by the average lactation SCC, was 814 kilograms. For multiparous, there was no difference in milk production between cows with and without SCM based on the SCC media of lactation. The estimate of lost production assessed through monthly testing of SCC and milk weighing at different stages of lactation, balanced by the prevalence of subclinical mastitis, was 917.9kg for primiparous and 1178.9kg for multiparous. The estimative of milk production with CCS at different stages of lactation showed greater loss of milk production when compared to the estimative based on the average SCC throughout the period of lactation. The milk production loss method based on the average somatic cell count of the whole lactation was underestimated when compared to the method based on average SCC in different stages of lactation.(AU)