Pharmacokinetic profile of Ceftiofur Hydrochloride Injection in lactating Holstein dairy cows

Ceftiofur (CEF), a broad‐spectrum third‐generation cephalosporin, exhibits a good activity against a broad range of gram‐negative and gram‐positive bacteria, including many that produce β‐lactamase. To design a rational dosage regimen for the drug in lactating Holstein dairy cows, the pharmacokinetic properties of ceftiofur hydrochloride injection were investigated in six cows after intravenous, intramuscular, and subcutaneous administration of single dose of 2.2 mg/kg BW (body weight). Plasma concentration–time curves and relevant parameters were best described by noncompartmental analysis through WinNonlin 6.3 software. After subcutaneous administration, the absolute bioavailability was 61.12% and the T_1/2λz (elimination half‐life) was 8.67 ± 0.72 hr. The C_max (maximum plasma concentration) was 0.88 ± 0.21 μg/ml and T_max (the time after initial injection to when C_max occurs) was 1.50 ± 0.55 hr. The MRT (mean residence time) was 11.00 ± 0.30 hr. Following intramuscular administration, the C_max (1.09 ± 0.21 μg/ml) was achieved at T_max (1.20 ± 0.26 hr) with an absolute availability of 70.52%. In this study, the detailed pharmacokinetic profiles of free and total CEF showed that this drug is widely distributed and rapidly eliminated and may contribute to a better understanding of the usage of ceftiofur hydrochloride injection in Holstein dairy cows.     

Impact of diet composition and temperature–humidity index on water and dry matter intake of high‐yielding dairy cows

The temperature–humidity index (THI) is widely used to characterize heat stress in dairy cattle. Diet composition is known to induce variation in metabolic‐associated heat production. However, the relationships between THI and diet are poorly characterized with regard to performance and intake behaviour. Therefore, the objectives were to evaluate the impact of THI on water intake (WI), dry matter intake (DMI) and the frequency of drinking and feeding bouts in lactating dairy cows offered four dietary treatments: each contained 20% grass silage and additionally (i) 20% maize silage, 60% concentrate (M‐HC); (ii) 60% maize silage, 20% concentrate (M‐LC); (iii) 20% pressed beet pulp silage, 60% concentrate (BPS‐HC); or (iv) 60% pressed beet pulp silage, 20% concentrate (BPS‐LC) (DM basis). Individual WI and DMI were recorded from April to July 2013. Furthermore, dietary effects on milk production and reticular pH were estimated. Milk yield was lowest for M‐LC, while energy‐corrected milk was similar for all diets. Milk fat percentage was higher and milk protein amount lower for cows offered both LC diets. Reticular pH below 6.3, 6.0 and 5.8 lasted longest for BPS‐LC. WI was higher for HC diets. However, the frequency of drinking bouts was not influenced by the ration. Lower DMI occurred for BPS‐LC compared to M‐LC. Frequency of feeding bouts was significantly higher for LC diets. THI was significantly related to WI, DMI as well as drinking and feeding bouts. Per increasing THI, WI increased slightly more for LC diets and DMI decreased more for HC diets. Frequency of drinking bouts increased slightly higher for BPS rations per rising THI, while the decrease in feeding bouts was highest for M‐HC. In conclusion, TMR composition and moderate heat stress impacted WI and DMI of dairy cows, while both dietary energy density and ruminal filling might intensify the THI impact.     

The effect of feed barrier design on displacements during feeding of dairy cows in small herds

The aim of this study was to investigate the effect of feed barrier design on displacements in dairy cows fed only roughage diets in the bunk in small commercial dairy herds. Six Norwegian dairy herds with open barriers (OB) and six herds with individual headspace barriers (IHB) were randomly selected. Number of displacements and withdrawals without physical contact was somewhat higher, but not significantly higher, in the IHB herds than in the OB herds but the variation between herds within the type of barrier were very large. The number of pushes and buttings directed towards the front part of the body of cows was significantly higher in the OB herds than in the IHB herds whereas pushes and butts directed towards the side of cows were significantly higher in the IHB herds than in the OB herds.     

Adrenal cortex reactivity in dairy cows differs between lactational stages and between different feeding levels

Changes in ACTH challenge test characteristics in dairy cows changing their physiological status at different lactational stages and different feeding levels were not investigated in terms of repeatability yet. In 23 multiparous Holstein cows (10 cows fed a sole fresh herbage diet without concentrate, 13 cows fed with concentrate), three ACTH challenge tests were performed: once during pregnancy shortly prior to drying off ( T1 ), and in week 3 ( T2 ) and 8 ( T3 ) after parturition. Test characteristics were correlated to performance and metabolic parameters: DMI, BW, energy balance (EB), plasma concentrations of free fatty acids (NEFA) and beta‐hydroxybutyrate (BHB). Basal plasma cortisol concentrations were higher at T1 compared with T2 and T3 (p < .05). The adrenal cortex sensitivity (expressed as total AUC (AUC_t) of cortisol response after ACTH application) was lowest at T2 compared with T1 and T3 (p < .05). Ranking of the individual animals’ responses was not repeatable between time points of the ACTH tests. Enhancing the energy deficiency during early lactation by omission of concentrate did not affect baseline cortisol concentrations in plasma, but decreased peak height at T2 (p < .05). Baseline plasma cortisol concentrations were positively correlated with cortisol peak values after ACTH application, previous lactation performance, milk yield and BW (p < .05). The AUC_t was positively correlated with baseline cortisol concentrations, EB and DMI. Cortisol release after ACTH injection was lower in animals with high plasma concentrations of NEFA, BHB and with higher contents of fat and free fatty acids in milk (p < .05). Cortisol peak height after ACTH administration was higher in cows with a more positive EB, higher DMI and lower plasma concentrations of NEFA and BHB. In summary, cortisol responses to ACTH challenges in this study were not repeatable in dairy cows changing their physiological status.     

Signals for identifying cows at risk of subacute ruminal acidosis in dairy veterinary practice

Controlling rumen disorders is critical to ensure successful dairy herd health management. Lactation diets of dairy cows are commonly rich in concentrates and low in physically effective fibre. Feeding of these diets increases the risk of rumen disorders with far‐reaching consequences for cattle health, welfare and sustainability of dairy production. The term subacute ruminal acidosis or SARA is often used as a synonym for poor rumen health. Being subclinical, SARA lacks of clear symptoms and is therefore difficult to diagnose and to control in the practice. This review article summarises common and identifies new direct and indirect cow signals related to SARA. We have performed a scientific evaluation and interpretation of each of these cow signals by highlighting their advantages and disadvantages from the practitioner's point of view. The gold standard of SARA cow signals still remains direct measurement of ruminal pH. However, continuous pH monitoring is cost‐intensive and often biased by sensor drift. Single‐point ruminal pH measurements by oral stomach tubing or rumenocentesis have strong limitations. Therefore, there is a need for reliable and robust markers of SARA that are easily accessible and inexpensive. Such indirect parameters are the observation of chewing and feeding activities, as well as the monitoring of milk, faecal, urine and blood variables. Also, novel technologies that allow rapid and non‐invasive measurement of the rumen mucosa thickness and ruminal motility patterns might provide advantages in SARA diagnosis. Due to several constraints of these indirect diagnostic tools, such as limited specificity and sensitivity, we strongly recommend using a combination of the signals to reliably identify cows at risk of SARA in a dairy herd.     

Essential oils improved weight gain,growth and feed efficiency of young dairy calves fed 18 or 20% crude protein starter diets

The objective was to evaluate interactions between starter protein (180 vs. 200 g/kg, DM basis) and a mixture of essential oils (EOs; containing thymol, eugenol, vanillin, limonene and guaiacol) on growth, metabolic and ruminal functions of Holstein dairy calves. In a completely randomized 2 × 2 factorial design, 48 calves, 3 days old (averaging BW 42.7 ± 1.9 kg), were allocated into groups fed the following diets: (i) 180 g/kg CP with no EO (180P‐NEO); (ii) 180 g/kg CP with EO (180P‐EO); (iii) 200 g/kg CP with no EO (200P‐NEO); and (iv) 200 g/kg CP with EO (200P‐EO). The EO was supplemented as 1 g/kg of starter DM. Calves were fed ad libitum starter diet and were weaned at day 59 of age, but diets continued until day 80. There were no interactive effects of CP and EO on intake and growth. Pre‐weaning feed efficiency tended to be increased for 200P‐EO (p = .09). Average daily gain and feed efficiency during pre‐weaning period as well as weaning weight were increased (p < .05) by EO, whereas wither height was increased by EO (p = .03) and tended to be increased for 200P vs. 180P (p = .06). Post‐weaning blood urea nitrogen concentration tended to be lower in 180P vs. 200P (p = .08). Ruminal short‐chain fatty acids concentration was greatest in 200P‐EO. The EO increased both butyrate (p = .02) and propionate proportions (p = .01) and reduced acetate proportional ratio (p < .01). Ruminal ammonia‐N was tended to be lower in calves‐fed EO (p = .05) and was lower in those fed 180P vs. 200P (p < .01). In conclusion, supplementation of the starter diet with essential oil improved weight gain, growth and feed efficiency of dairy calves, irrespective of dietary protein content.     

施用生物炭和AM真菌对镉胁迫下玉米生长和生理生化指标的影响

为了探究镉(cadimum, Cd)胁迫下生物炭和丛枝菌根(arbuscular mycorrhizal, AM)对植物生长的协同效应,采用盆栽试验,研究在3个Cd污染(0,3,6 mg Cd·kg^-1)水平下,施用小麦秸秆生物炭和接种AM真菌(Glomus intraradices BEG 141)对玉米生长和生理生化特性的影响。结果表明,施用生物炭和接种AM真菌单独或复合处理均能提高玉米的株高、生物量、光合色素含量、光合特性和抗氧化酶活性,降低胞间CO₂浓度(C_i)、MDA含量。接种AM真菌促进玉米生长效果优于生物炭,而生物炭对提高土壤pH效果较好,施用生物炭和接种AM真菌复合处理对Cd胁迫下玉米生长和改善玉米生理生化特性的促进效应最佳。其中,在6 mg Cd·kg^-1水平下,施用生物炭和接种AM真菌复合处理使株高、生物量分别增加43.87%、79.10%;净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)分别提高33.09%,45.04%,31.27%;叶片的超氧化物歧化酶(superoxide dismutase,SOD)活性、过氧化物酶(peroxidase,POD)活性、过氧化氢酶(catalase,CAT)活性分别提高51.42%,82.91%,43.96%。综合来看,生物炭和AM真菌单独或复合处理均能够减轻Cd胁迫和促进植物生长,以生物炭和AM真菌复合处理效果最佳,AM真菌处理效果次之,生物炭处理效果较差。     

Effect of supplemental dietary slow‐release urea on growth performance and physiological status of dairy heifers

We examined the effect of supplemental dietary slow‐release urea on the growth performance and physiological status of 16 dairy Holstein heifers (10 months of age, 322 ± 10 kg). The heifers were offered a formulated isocaloric and isonitrogenous 70:30 roughage : concentrate ration and were assigned randomly to one of four levels of slow‐release urea supplementation (0% [U₀], 1% [U₁], 1.5% [U_1.5] and 2% [U₂] dry matter [DM]). The total study lasted 95 days, which included a 20 days adaptation period. Dry matter intake (DMI) of U₂ was lower than the intakes of U₀ and U₁ (p < .05), while average daily gains (ADG) of U₁ and U_1.5 were higher than U₀ and U₂ (p < .05). Rumen volatile fatty acids concentration did not differ among the four treatments, while ammonia nitrogen concentration increased with an increase in urea level (p < .05). Serum blood urea nitrogen concentration was lower in U_1.5 than in U₀ and U₂ while serum free fatty acids concentration in U₂ was higher than in the other three treatments (p < .05). We concluded that the addition of urea at a level of 1.5 to 2.0% DM resulted in a reduction in DMI but the addition of 1.0%–1.5% urea resulted in the highest ADG, with no negative effects on rumen fermentation and health status of the calves.     

蒸汽压片玉米在奶牛生产中的应用研究进展

玉米是奶牛舍饲的主要能量饲料来源之一,而蒸汽压片技术是一项目前较为成熟的日粮加工技术,主要通过机械的湿热加工方法改变原料物理形态和营养物质的化学结构,广泛应用于反刍动物日粮中。蒸汽压片处理工艺中的蒸汽压力、温度和处理时间会影响压片产品的容重和淀粉糊化度,进而影响其饲喂效果。研究发现,经蒸汽压片处理的玉米可有效提高其淀粉消化率,加快瘤胃内的发酵速度,改变瘤胃发酵模式,促进瘤胃微生物蛋白合成,有利于维持瘤胃pH及瘤胃内环境的稳定。也有研究表明,蒸汽压片玉米饲喂奶牛后,对其采食量没有明显影响,但可以提高产奶量,改善乳成分,从而提高奶牛的产奶性能。作者对蒸汽压片玉米技术及其在奶牛生产中的应用研究进展进行综述,以期为蒸汽压片玉米在中国奶牛生产中的合理使用提供参考。