饲料源活性肽混合物的提取及其对绵羊瘤胃微生物生长的影响

本文探讨了用鱼粉和豆粕制备活性肽的适宜条件,并以胃蛋白酶和胰蛋白酶分别水解鱼粉和豆粕制得的4种活性肽为氮源、可溶性碳水化合物为能源,采用体外法研究了不同来源的肽氮对瘤胃细菌和原虫生长的影响以及对瘤胃中蛋白酶和纤维酶活性的影响。结果表明,胃蛋白酶和胰蛋白酶分别水解鱼粉和豆粕制备活性肽的最适条件为:温度37℃,时间20 h,pH分别为2和7。来源于动物性饲料的混合肽对促进瘤胃微生物生长优于来源于植物性饲料的混合肽;分子量小于3 000 u的鱼粉肽和豆粕肽对瘤胃细菌和原虫的生长有促进作用,能提高瘤胃中蛋白酶活性,而对纤维酶活性无作用。     

Effect of supplementing a high-protein ram press sunflower cake concentrate on smallholder milk production in Zimbabwe

Ram press sunflower cake protein concentrate was formulated locally and its effect on the performance of dairy cows was compared with that of a commercial dairy concentrate. The effects of concentrate on roughage dry matter intake, milk yield and milk composition, live weight and calving intervals were similar for all concentrates, which indicated that the home grown dairy concentrates were as effective as the dairy commercial concentrate. The lack of significant differences in the concentrations of rumen NH₃-N, pH, VFAs and total AA in all the cows between concentrate types supported this. The results indicated that in the low-resource and low-input production systems, crossbreds were as productive as Jersey and Red Dane cows. The exotic cows were more susceptible to tick-borne diseases and mastitis, and showed higher incidences of calving problems and retained placenta compared with crossbred cows. The economics of feeding ram press sunflower concentrate were compared with those of a commercial dairy concentrate on the performance of crossbred, Red Dane and Jersey cows. The gross margin was higher when feeding sunflower cake than when feeding commercial dairy concentrate (p < 0.05).     

蛋氨酸的瘤胃代谢与调控

从蛋氨酸的营养生理功能入手,综述了蛋氨酸的瘤胃代谢与瘤胃保护的研究进展,提出了生物调控瘤胃蛋氨酸代谢的可行性。     

高蛋白和一般蛋白日粮条件下甲醛处理大豆粉对湖羊蛋白质消化代谢的影响

用装置永久性瘤胃和皱胃癌管的阉湖羊,研究在高蛋白和一般蛋白日粮条件下甲醛处理大豆粉对湖羊前胃和整体氮代谢的影响。并用体外培养和尼龙绢袋法比较大豆粉和甲醛处理大豆粉的氮损失程度。结果表明,甲醛处理大豆粉在瘤胃环境中的氮损失程度较低,饲喂之后瘤胃液氨氮浓度降低,pH值升高,而对总挥发性脂肪酸浓度和发酵类型无明显影响。成年湖羊每日通过皱胃的食糜量为7.40公斤,或0.24公斤/公斤体重,食糜中饲料蛋白(包括内源蛋白)仅为摄入粗蛋白的20—30％。饲喂甲醛处理大豆粉时,通过皱胃的总氮、非氨氮和饲料蛋白氮都增加,而微生物氮趋于减少。高蛋白日粮时,通过皱胃的饲料蛋白量增加较多,达15.2克/天(47.4％);一般蛋白日粮时增加较少,为6.1克/天(19.5％)。高蛋白日粮时饲喂甲醛处理大豆粉可促进氮贮留;一般日粮条件下则效果不佳。此外,氮贮留还与青干草采食量或纤维素消化量呈正相关。     

Quantitative analysis of ruminal methanogenic microbial populations in beef cattle divergent in phenotypic residual feed intake（RFI）offered contrasting diets

Background：Methane（CH_4） emissions in cattle are an undesirable end product of rumen methanogenic fermentative activity as they are associated not only with negative environmental impacts but also with reduced host feed efficiency.The aim of this study was to quantify total and specific rumen microbial methanogenic populations in beef cattle divergently selected for residual feed intake（RFI） while offered（i） a low energy high forage（HF） diet followed by（ii） a high energy low forage（LF） diet.Ruminal fluid was collected from 14 high（H）and 14 low（L） RFI animals across both dietary periods.Quantitative real time PCR（qRT-PCR） analysis was conducted to quantify the abundance of total and specific rumen methanogenic microbes.Spearman correlation analysis was used to investigate the association between the relative abundance of methanogens and animal performance,rumen fermentation variables and diet digestibility.Results：Abundance of methanogens,did not differ between RFI phenotypes.However,relative abundance of total and specific methanogen species was affected（P〈 0.05） by diet type,with greater abundance observed while animals were offered the LF compared to the HF diet.Conclusions：These findings suggest that differences in abundance of specific rumen methanogen species may not contribute to variation in CH_4 emissions between efficient and inefficient animals,however dietary manipulation can influence the abundance of total and specific methanogen species.     

生长期牦牛能量代谢和瘤胃代谢的研究

用闭路式呼吸面具法和永久性瘤胃瘘管法及相应的代谢、饲养试验对1—3岁牦牛在海拔高度2300—4300m处作绝食能量代谢和瘤胃消化代谢测定,结果表明:牦牛在该高度范围内绝食产热值稳定不变;牦牛的等热区为8—14℃,并从—20℃起才随气温下降而增加产热;牦牛瘤胃发酵时,在挥发性脂肪酸中丙酸、丁酸比例较其他牛种高,并且当饲料质量下降时,高效酸仍保持较高比例;在较低海拔高度(2300m)时,牦牛的FHP=302.13kJ/kgW~(0.75),MEm为458kJ/kgW~(0.75),Km为0.66,这些数值与国内外对其他牛种研究结果接近,只是在高海拔条件下才显示差异。     

Effect of altered carbohydrate traits in hulless barley (Hordeum vulgare L.) on nutrient profiles and availability and nitrogen to energy synchronization

Four hulless barley cultivars (zero-amylose waxy, CDC Fibar; 5%-amylose waxy, CDC Rattan; normal-amylose, CDC McGwire and high-amylose, HB08302) were developed at the Crop Development Centre, University of Saskatchewan, with differences in carbohydrates traits on the basis of amylose (1–20% DM) and β-glucan (5–10% DM) content. The objectives of this research were to determine: 1) the effect of the alteration of these carbohydrate traits in hulless barley on nutrient availability in ruminants, and 2) carbohydrate structure conformation on hourly effective rumen degradation ratio, in comparison with hulled barley-CDC Copeland. Among the hulless barley lines, HB08302 was greater (P < 0.05) in rumen bypass crude protein (BCP: 52.1% CP), effective degradability (ED) of neutral detergent fibre (EDNDF: 74 g/kg DM) than these in CDC Fibar, whereas CDC Fibar showed greater (P < 0.05) effective degradable crude protein (EDCP: 90 g/kg DM) than the other hulless barley lines. Compared with hulless barley, the hulled CDC Copeland showed relatively greater (P < 0.05) BNDF (62.5% NDF or 98 g/kg DM), starch degradation rate (K_d: 17.4%/h) and EDST (75.9% ST) but reduced (P < 0.05) rumen undegradable protein (RUP: 49 g/kg DM). With the respect to hourly effective degradation (ED) ratios, hulless barley cultivars exhibited relatively optimal hourly ED ratios, ranging from 23 to 34 g N/kg CHO, higher than the hulled barley. Among hulless barley cultivars, CDC Fibar and Rattan had the highest (P < 0.05) ratios (34 g N/kg CHO), while the ratio for CDC McGwire (23 g N/kg CHO) was the lowest (P > 0.05). In conclusion, hulless barley lines with altered carbohydrate traits have the potential to increase rumen nutrient availability to ruminants. The altered carbohydrate conformation of hulless barley affected hourly ED ratios, thus affecting rumen nitrogen to energy synchronization.     

酵母β-葡聚糖对早期断奶羔羊瘤胃氮代谢的影响

选用甘肃肉用绵羊新品种选育群初生公羔20只,随机分为5组,观测了饲粮中添加不同剂量（0、37．50、75．00、112．50、150．00mg／kg）酵母β-葡聚糖对早期断奶羔羊瘤胃氮代谢参数的影响,结果表明,添加酵母β-葡聚糖对日龄82d的羔羊瘤胃液中总氮、氨氮和蛋白氮含量均没有显著影响（P〉0.05）,75．00mg／kg的添加剂量组尿素氮含量有高于对照组的趋势（P=0．091）,食前150．00mg／kg添加剂量组血清尿素氮显著低于对照组（P〈．05）。     

The effect of dicyandiamide on rumen and blood metabolites,diet digestibility and urinary excretion

The excretion of urine by dairy cows provides a source of nitrogen (N) to pasture. Excess N from urine patches can be lost through nitrate (NO₃⁻) leaching and nitrous oxide (N₂O) emissions. Dicyandiamide (DCD) inhibits nitrification in the soil and is usually applied to the pasture by blanket spreading the entire field. This study assessed the potential of pulse-dosing cows with DCD so that the DCD will be excreted in the urine and deposited directly onto the urine patches. The objective of this study was to measure the recovery of DCD in urine and faeces and to assess the effects of DCD on rumen and blood metabolites and diet digestibility. Eight non-lactating Holstein–Friesian dairy cows fitted with rumen cannulae were assigned to two treatments in a Latin square design over two periods. The two treatments used were (1) control (CON) consisting of 500 ml distilled water and (2) DCD consisting of 0.1 g DCD per kg liveweight (LW) suspended in 500 ml distilled water. Both treatments were pulse-dosed into the rumen daily for 6 days with half the volume dosed in the morning and the remainder in the afternoon. The administration of DCD into the rumen had no effect on rumen and blood metabolites, and diet digestibility when compared to the control treatment, as all were not significantly different from the control treatment and were within the normal biological range. During 6 days of dosing with DCD the average recovery of the dosed DCD in urine was 82.3%, with a further 2.1% recovered in the faeces. No DCD was recovered in the urine and faeces 10 days following the cessation of dosing. These results could provide the basis for a novel mitigation strategy to reduce NO₃⁻ leaching and N₂O emissions from urine patches in grazed grassland.     

Restricting access time at pasture and time of grazing allocation for Holstein dairy cows: Ingestive behaviour,dry matter intake and milk production

The objective of this study was to assess the effects of restricting access time to pasture and time of grazing allocation on grazing behaviour, daily dry matter intake (DMI), rumen fermentation, milk production and composition in dairy cows. Twenty-one autumn-calving Holstein cows were assigned to one of the following 3 treatments: providing access to a daily strip of pasture for either 8 h between 07:00 and 15:00 h (T7–15), 4 h between 07:00 and 11:00 h (T7–11), or 4 h between 11:00 and 15:00 h (T11–15). The experimental period consisted of 3 weeks of adaptation and 6 weeks of measurements. Cows were offered a daily herbage allowance of 18 kg DM/cow to ground level, 6.1 kg DM/day of a ground sorghum grain-based supplement and 5.2 kg DM/day of maize silage. Milk yield was greater for cows with 8 h access time to the pasture (25.4 vs. 24.1 for 8 and 4 h access time, respectively). Milk yield was not different between cows that access early (T7–11) or late (T11–15) to the grazing session. Milk protein yield was greater for cows with 8 h access time (0.75 kg/d) vs. 4 h access time treatments (0.72 kg/d). Cows with late access time to grazing in the morning produce more protein (0.74 kg/d) than cows with early access to the pasture (0.70 kg/d). Duration of access had a significant effect on herbage DMI (8.3 vs. 6.6 kg/d, for 8 and 4 h access, respectively), but there was no significant effect of time of grazing allocation. Intakes of concentrate and maize silage DM did not differ between treatments.