甘肃天祝牧区酸奶发酵剂发酵性能的研究

将从甘肃天祝牧区采集的酸奶样品及兰州市几种市售酸奶制作为酸奶发酵剂，对比它们的发酵性能．牧区酸奶发酵剂性能较优。由牧区酸奶发酵剂中分离得到的几株乳酸茵产酸能力及产黏能力较好，其发酵凝乳的温度范围较宽。     

Invited review: production and digestion of supplemented dairy cows on pasture

Literature with data from dairy cows on pasture was reviewed to evaluate the effects of supplementation on intake, milk production and composition, and ruminal and postruminal digestion. Low dry matter intake (DMI) of pasture has been identified as a major factor limiting milk production by high producing dairy cows. Pasture DMI in grazing cows is a function of grazing time, biting rate, and bite mass. Concentrate supplementation did not affect biting rate (58 bites/min) or bite mass (0.47 g of DM/bite) but reduced grazing time 12 min/d per kilogram of concentrate compared with unsupplemented cows (574 min/d). Substitution rate, or the reduction in pasture DMI per kilogram of concentrate, is a factor which may explain the variation in milk response to supplementation. A negative relationship exists between substitution rate and milk response; the lower the substitution rate the higher the milk response to supplements. Milk production increases linearly as the amount of concentrate increases from 1.2 to 10 kg DM/d, with an overall milk response of 1 kg milk/kg concentrate. Compared with pasture-only diets, increasing the amount of concentrate supplementation up to 10 kg DM/d increased total DMI 24%, milk production 22%, and milk protein percentage 4%, but reduced milk fat percentage 6%. Compared with dry ground corn, supplementation with nonforage fiber sources or processed corn did not affect total DMI, milk production, or milk composition. Replacing ruminal degradable protein sources with ruminal undegradable protein sources in concentrates did not consistently affect milk production or composition. Forage supplementation did not affect production when substitution rate was high. Fat supplementation increased milk production by 6%, without affecting milk fat and protein content. Increasing concentrate from 1.1 to 10 kg DM/d reduced ruminal pH 0.08 and NH3-N concentration 6.59 mg/dl, compared with pasture-only diets. Replacing dry corn by high moisture corn, steam-flaked or steam-rolled corn, barley, or fiber-based concentrates reduced ruminal NH3-N concentration 4.36 mg/dl. Supplementation did not affect in situ pasture digestion, except for a reduction in rate of degradation when high amounts of concentrate were supplemented. Supplementation with energy concentrates reduced digestibility of neutral detergent fiber and intake of N but did not affect digestibility of organic matter or flow of microbial N.     

Meta-analysis of the effect of pasture allowance on pasture intake,milk production,and grazing behavior of dairy cows grazing temperate grasslands

Daily pasture allowance (PA) is defined as the product of pregrazing pasture mass and offered area, and is the major grazing management factor determining pasture utilization per unit area and daily performance of grazing dairy cows. The objective of the present study was to perform a meta-analysis reviewing the effect of PA on pasture intake, milk production, milk composition, and grazing behavior of dairy cows. Experiments studying the effect of PA on pasture intake or milk production, which eventually included milk composition or grazing behavior data, or both, were selected to create a database. Papers were selected only if at least 2 PA were compared under the same experimental conditions, particularly the same pasture mass (i.e., where PA levels were only obtained through changes in daily offered area). The final database included 97 PA comparisons reported in 56 papers. For analytical purposes, the database was subdivided into 3 subsets that varied according to the estimation height (EH) at which PA was determined; that is, PA above ground level (PA₀ subset), PA above 2.5 to 3.5 cm (PA₃ subset), and PA above 4 to 5 cm (PA₅ subset). Statistical analyses were conducted independently on the PA₀, PA₃, and PA₅ subsets and on the whole database (global analysis) by using linear and nonlinear mixed-model procedures. The curves, either exponential, quadratic, or linear, describing the effects of PA on pasture intake, milk production, or grazing behavior of dairy cows are conceptually similar, whatever the EH. The equations describing these curves are, however, specific for each EH. Accordingly, from typical low to high PA, the increase in pasture intake (0.13 vs. 0.21 vs. 0.28 kg/kg of PA), milk production (0.11 vs. 0.17 vs. 0.24 kg/kg of PA), and milk solids production (0.008 vs. 0.010 vs. 0.013 kg/kg of PA) per kilogram of increase in PA was lower for PA₀ than for PA₃, and for PA₃ than for PA₅. Grazing time increased from low to medium PA and did not vary from medium to high PA. Pasture intake rate seemed to increase from low to medium PA because of greater bite mass, whereas it increased from medium to high PA because of greater biting rate. The present meta-analysis demonstrated that the general relationship between PA and any dependent variable is quite strong and independent of EH. This suggests no specific relationship for some parts of the world or methodology approach, with a high portability of the global equations calculated here. These results are useful for improving grazing management and modeling on pasture-based dairy systems.     

一种新型的无人机牧草分割网络—LMS-DeeplabV3+

目前草原环境复杂、牧草分散且与背景颜色差异小,无法实现高效精准的分割,因此本文提出了一种新型的轻量化多尺度DeeplabV3+网络(lightweight and multi-scale DeeplabV3+network, LMS-DeeplabV3+)。该网络以DeeplabV3+为基础网络,首先选用轻量级的MobilenetV2作为骨干网络用于初步特征提取,并为了适应牧草分割任务做了网络配置上的调整;其次在加强特征提取模块和解码模块中均使用深度可分离卷积代替普通卷积以轻量化网络;此外利用密集空洞空间金字塔池化(dense atrous spatial pyramid pooling, DASPP)模块捕获更大的感受野,加强各特征之间的交互;又引入卷积注意力机制(convolutional block attention module, CBAM)重分配权重加强特征提取。实验证明,提出的新网络与原始网络相比平均交并比(mean intersection over union,mIOU)提升了8.06个百分点、平均像素精度(mean pixel accuracy,mPA)提升了6.7...     

混合饲料草饼成型试验研究

本文通过混合饲料压制圆形草饼试验,对其成型原理、技术参数和力能关系进行了较深入的研究。     

A survey analysis of farmer practices and perceptions of zero-grazing on Irish dairy farms

Zero-grazing (ZG; the mechanical harvesting and feeding of fresh grass) is increasingly used in grass-based milk production systems alongside conventional grazing. It allows farmers to supply fresh grass from land parcels that are outside of the main grazing block during seasonal shortages and periods when climatic conditions limit animal grazing opportunities. The objective of this study was to establish an understanding of current ZG practices on Irish dairy farms, to capture farmer perceptions on the implementation of this management practice, and to identify farmer knowledge requirements on ZG. An online survey was distributed and completed by 130 dairy farmers who use or have used ZG. Zero-grazing was used alongside conventional grazing by 92% of respondents. These farms were particularly fragmented, with between 1 and 14 separate land blocks. Respondents felt ZG helped them overcome fragmentation, increase grass use, and extend grass feeding in spring and autumn. However, extra cost and time input associated with ZG were recognized as key challenges. The majority of respondents rated current technical information available on ZG in the Republic of Ireland as “poor” or “very poor,” and knowledge deficits were identified in the areas of cost analysis, grass management and productivity, cow productivity, cow health and nutrition, and soil fertility.     

Physicochemical properties of whole milk powder derived from cows fed pasture or total mixed ration diets

This study examined the effect of dietary factors on compositional and functional properties of whole milk powder (WMP) produced from bovine milk. Raw milk samples were obtained from 3 groups of 18 Holstein Friesian spring-calving cows randomly assigned to diets based on perennial ryegrass (GRS), perennial ryegrass/white clover sward (CLV), and total mixed ration (TMR). Raw milks obtained in late lactation were subsequently standardized for fat, heat-treated (90°C for 30 s), evaporated, and homogenized before spray drying. The WMP produced from each diet were analyzed to determine differences in color, particle size distribution, heat coagulation time, yogurt gelation, texture profile, and protein profile due to each diet. Significant differences in heat coagulation time were observed between the CLV and TMR samples, whereas color values were significantly different between GRS and TMR samples. No significant differences in gross composition, protein profile, or whey protein nitrogen index were found between the 3 WMP samples. Average D₉₀ values (the particle size at which 90% of the particles were smaller than the specified size) for fat globules were significantly lower in the TMR sample compared with the GRS and CLV samples. Yogurts produced from GRS- and CLV-derived WMP had significantly higher elastic moduli (G′) than those produced from TMR-derived WMP. Similarly, texture profile analysis revealed significantly higher firmness values in yogurt samples derived from CLV compared with TMR samples. Our data characterize the effect of these diets on the composition and functional properties of fat-standardized WMP, suggesting better yogurt functionality and thermal stability in WMP derived from pasture-based bovine diets.     

Water footprint of beef production on Texas High Plains pasture

ABSTRACT

Depletion of the Ogallala aquifer in the U.S. Great Plains demands information on water usage in forage-fed beef production. We compared a summer grazing system for beef steers consisting of warm-season grasses vs. grasses growing with lucerne (Medicago sativa L.). The water footprint averaged 39 and 26 m³ of water kg^?1 of beef liveweight gain, respectively, when water included rainfall, irrigation, and livestock drinking. Including lucerne reduced the water footprint of beef weight gain thanks to its ability to alleviate protein deficiency in the associated grasses, thus diminishing an important source of inefficiency in converting feed to meat.     

Can phosphorus fertilisers alone increase levels of soil nitrogen in New Zealand hill country pastures?

In New Zealand grazed pastures, nitrogen (N) fixation by clover is the traditional method of supplying N to the grasses that make up the bulk of the pasture sward. In order to stimulate satisfactory clover growth, phosphorus (P) fertilisers are applied at levels which are generally more than adequate for grass requirements. These legumes then provided N through biological nitrogen fixation. However, studies conducted in New Zealand hill country pastures have revealed that these pastures are still highly N responsive. These results draw attention to a key issue with respect to N fertility in hill country pasture and the question arises as to the value of large P fertiliser applications to overcome N deficiency through clover growth. Here we used modelling approach to evaluate the effectiveness of adding P fertilisers to stimulate clover growth for improving soil N status in hill country pastures and to explore why the hill pastures are N responsive. In addition an attempt was made to explore the potential of fertiliser N in hill pastures based on the current model outcomes and the measured values of pasture production under non-limiting N.