Effect of mastitis during the first lactation on production and reproduction performance of Holstein cows

The aim of this study was to evaluate the effect of postpartum mastitis between first calving and subsequent conception on production and reproduction performance as well as culling of Holstein cows. A data set of 9,183 first lactation cows was used. Results showed that the first cumulative 100?days' milk production and the milk yield standardized to 305?days were affected by the interval from calving to first mastitis (P??0.05). Calving year, calving difficulty score, and cumulative first 60?days milk production had significant impacts on mastitis risk (P?相似文献   

日粮添加鱼粉和n-3多不饱和脂肪酸对泌乳初期奶牛产奶量及机体代谢的影响

本试验旨在研究添加鱼粉和特殊n-3脂肪酸对泌乳初期奶牛产奶量、乳成分、干物质采食量和血浆中代谢产物和代谢有关的激素含量以及甘油三酯在肝脏中累积的影响。从产奶第5～50 d,给奶牛饲喂等氮、等能、等脂肪日粮,其中处理分别为0%(对照组)以及1.25%、2.5%、5%的鱼粉和2.3%的鱼油脂肪酸钙盐,在产奶第25 d和第50 d饲喂前(离饲喂后间隔11 h)采集血液样品。试验结果表明:不同处理影响产奶量(分别为48.2、49.8、48.6、53.5、52.2±1.0 kg)和干物质采食量(分别为22.7、22.8、23.0、23.8、24.7±0.5 kg)。各处理间血浆葡萄糖平均浓度分别为53.4、55.3、51.1、57.6、57.3±1.3mg/dl);在添加5%鱼粉和添加2.3%鱼油脂肪酸钙盐处理组中血浆胰岛素浓度均有上升趋势。试验结果也显示在第25 d所有处理奶牛血浆中葡萄糖含量相一致;但在第50 d时存在着差异,其含量分别为54.6、54.4、52.4、60.5、58.3±1.4 mg/dl)。在第25 d时,5%鱼粉和2.3%鱼油脂肪酸钙盐处理中血浆胰岛素含量有所增加,但在第50 d时含量又相一致。各日粮处理对乳成分、能量平衡和血浆非酯化脂肪酸、β-羟基丁酸盐以及尿素浓度均无显著影响。在第21 d时,各日粮处理血浆中天冬氨酸盐转氨酶和肝脏甘油三酯浓度也无较大变化。因此本研究结果显示:在泌乳初期奶牛日粮中添加鱼粉或n-3多不饱和脂肪酸可显著增加产奶量和干物质采食量,但并不改变乳组成。     

Effect of adjuvants on in ovo vaccination against Newcastle disease on hatchability,performance and antibody titres in commercial pullets

This study was conducted to investigate the efficacy of in ovo administration of aluminium hydroxide (AH) and/or mannan oligosaccharide (MOS) adjuvants along with lentogenic VG/GA strain‐Avinew to alleviate the embryonic pathogenicity of Newcastle disease virus. Six hundred and thirty fertilized Bovans eggs were divided into nine groups of 70 each incubated in a commercial hatchery and administered with eight types of in ovo injections in a factorial design of 2 × 2 × 2 including with/without AH, MOS and Newcastle disease vaccine (NDV), and one uninjected group on day 18 of incubation. Hatchability was higher in the eggs received MOS and/or AH adjuvants plus NDV compared those injected with NDV alone which confirmed the attenuation of NDV. However, the average daily feed intake and feed conversion ratio of pullets hatched from NDV‐injected eggs were significantly reduced, but did not affect growth performance during 0‐42 days of age. The performance of pullets hatched from eggs injected with AH, MOS or their mixture with NDV was not significantly different during all growth periods. Pullets from MOS + vaccine injected eggs had significantly higher antibody titres against NDV compared to those hatched from either injected with saline or uninjected on d 28 (p < .05). In addition, AH plus vaccine and MOS significantly improved total anti‐SRBC and IgG respectively. Histological observation revealed that injection of MOS adjuvant into eggs led to increase crypt depth, whereas AH injection caused a reduction in villus surface area of jejunum in chicks on d 14 post‐hatch. It is concluded that in ovo MOS injection as compared to AH may be more effective to attenuate the embryonic pathogenicity of in ovo NDV injection.     

Study of broiler chicken responses to dietary protein and lysine using neural network and response surface models

1. In this study, neural network (NN) and response surface (RS) models were developed to investigate the response [average daily gain (ADG) and feed efficiency (FE)] of young broiler chickens to dietary protein and lysine. For this purpose, data on their responses to dietary protein and lysine were extracted from the literature and separate NN and RS models were constructed.

2. Comparison between the NN and RS models revealed higher accuracy of prediction with the NN models compared to the RS models. In terms of R ² values, the NN models developed for both ADG (R ² = 0.923) and FE (R ² = 0.904) were far superior to the RS models (R ² for ADG = 0.511; R ² for FE = 0.67). This suggests that the NN models can serve as an alternative option to conventional regression approaches including use of RS models.

3. Optimisation of the NN models developed for response to protein and lysine showed that diets containing 220.7 (g/kg of diet) protein and 12.85 (g/kg of diet) lysine maximise ADG, whereas maximum FE is achieved with diets containing 241.3 and 13.12 (g/kg) protein and lysine, respectively. Based on the optimisation results, optimal dietary protein and lysine concentrations for maximum FE in broiler chickens during the starting period are higher than for ADG.     

Isolation and identification of a lipase producing Bacillus sp. from soil

Lipase production in an indigenous lipolytic Bacillus sp. was detected in media containing Tributyrin-Tween 80 and Rhodamine B-Olive oil. The statistical Taguchi model was used to predict the optimum experimental conditions for bacterial growth and lipase production. Partial optimization was carried out for selection of salt base, oil, glucose, NH4Cl and yeast extract concentrations, inoculum density, pH and agitation. Maximum lipase activity was detected in the cell free supernatants of cultures grown in a medium containing 10 g L(-1) yeast extract, 15 g L(-1) NH4Cl, 3 g L(-1) K2HPO4, 1 g L(-1) KH2PO4, 0.1 g L(-1) MgSO4 x 7H2O, 2 g L(-1) glucose, 0.6 mM MgCl2 and 15 ml L(-1) olive oil, pH 8.5 at 30 degrees C for 24 h and low agitation. The amount oflipase produced in the designed medium was in agreement with the predicted values by the statistical method. 16S rRNA cloning and sequencing identified the test organism as Bacillus pumilus.