Balanced pasture fertilization in the Basque Country: I. Phosphorus and potassium budgets on dairy farms

Dairy farming is the main agricultural activity of the Basque Country. A dairy farm is characterized as a system with soils and crops, forage, cattle and manure as main components, and in such a system, nutrient cycling is very important to maintain soil fertility and optimize forage production. To quantify nutrient transfers in the cycle, a simple system was developed and has been applied to seventeen farms to examine its ability to achieve a balanced P and K fertilization. These farms have provided data on inputs (fertilizer, feeds, concentrates), pasture and manure management, and outputs (milk production), and soil samples have been taken from farm pastures. Phosphorus and K in excreta and uneaten pasture is used with a relatively high efficiency as suggested by the relatively high efficiency of P and K utilization by the pasture that usually ranges from 70 to 90%. Concentrate feeding (3000 kg cow^–1 yr^–1) represents one of the main P and K inputs in Basque Country dairy farms, averaging 26 and 66 kg ha^–1, respectively. Besides, release of K in the soil through slow liberation from non-exchangeable sites was estimated as 30 kg ha^–1. Thus, a high efficiency in excreta recycling would diminish substantially P and K mineral fertilizer needs. Farm nutrient budgets appear to be a convenient tool for determining nutrient shortages and surpluses at farm level, and thus they are considered as a first step to support a better management of maintenance fertilization of permanent pastures.     

Application strategies for Sechura phosphate rock use on permanent pasture

At two phosphate (P) responsive sites in hill country the effectiveness of Sechura phosphate rock (SPR) as a direct application P fertilizer for permanent pasture was evaluated. Sechura was applied at two rates, in three different application strategies. The treatments were 16.7 and 50 kgP ha^–1 annually, 25 and 75 kgP ha^–1 biennially, and 50 and 150 kgP ha^–1 triennially giving a total of 50 and 150 kgP ha^–1, respectively, over three years. Single superphosphate (SSP) served as the standard P fertilizer. A comparison was also made between SPR and Chatham Rise phosphorite (CRP), another reactive PR. Total pasture and legume production and P uptake by pasture was measured with all fertilizer treatments over a three year period.In the year of application, SPR was as effective as SSP in stimulating total pasture and legume production and P uptake by pasture. This reflects the very reactive nature of this PR. In the second and third years of measurement, SPR did not show superior residual efffects to SSP. The ability of CRP to stimulate legume growth more than SPR in the second year following application demonstrates the danger of generalizing about the residual effects of reactive PR materials. Of the application strategies evaluated, a biennial appplication of 25 kgP ha^–1 as SPR maintained legume growth at a higher level than a smaller (16.7 kgP ha^–1) annual dressing. The biennial strategy also increased total pasture yield, in addition to legume production to a greater extent in the second and third years than a single (50 kgP ha^–1) triennial application.     

Effect of pasture versus indoor feeding systems on quality characteristics,nutritional composition,and sensory and volatile properties of full-fat Cheddar cheese

The purpose of this study was to investigate the effects of pasture-based versus indoor total mixed ration (TMR) feeding systems on the chemical composition, quality characteristics, and sensory properties of full-fat Cheddar cheeses. Fifty-four multiparous and primiparous Friesian cows were divided into 3 groups (n = 18) for an entire lactation. Group 1 was housed indoors and fed a TMR diet of grass silage, maize silage, and concentrates; group 2 was maintained outdoors on perennial ryegrass only pasture (GRS); and group 3 was maintained outdoors on perennial ryegrass/white clover pasture (CLV). Full-fat Cheddar cheeses were manufactured in triplicate at pilot scale from each feeding system in September 2015 and were examined over a 270-d ripening period at 8°C. Pasture-derived feeding systems were shown to produce Cheddar cheeses yellower in color than that of TMR, which was positively correlated with increased cheese β-carotene content. Feeding system had a significant effect on the fatty acid composition of the cheeses. The nutritional composition of Cheddar cheese was improved through pasture-based feeding systems, with significantly lower thrombogenicity index scores and a greater than 2-fold increase in the concentration of vaccenic acid and the bioactive conjugated linoleic acid C18:2 cis-9,trans-11, whereas TMR-derived cheeses had significantly higher palmitic acid content. Fatty acid profiling of cheeses coupled with multivariate analysis showed clear separation of Cheddar cheeses derived from pasture-based diets (GRS or CLV) from that of a TMR system. Such alterations in the fatty acid profile resulted in pasture-derived cheeses having reduced hardness scores at room temperature. Feeding system and ripening time had a significant effect on the volatile profile of the Cheddar cheeses. Pasture-derived Cheddar cheeses had significantly higher concentrations of the hydrocarbon toluene, whereas TMR-derived cheese had significantly higher concentration of 2,3-butanediol. Ripening period resulted in significant alterations to cheese volatile profiles, with increases in acid-, alcohol-, aldehyde-, ester-, and terpene-based volatile compounds. This study has demonstrated the benefits of pasture-derived feeding systems for production of Cheddar cheeses with enhanced nutritional and rheological quality compared with a TMR feeding system.     

Invited review: Genetic considerations for various pasture-based dairy systems

Pasture-based dairy systems use grazing to supply significant percentages of the dry matter intake of cows and heifers. Such systems vary from those for which pasture is used only as a supplemental feed for cows primarily fed a total mixed ration to those for which pasture is the primary source of dry matter for the herd. Cows that are optimal in a pasture system share many general characteristics with cows that are appropriate for a nonpasture system, including feed efficiency, maintenance of body condition, reproductive fitness, udder health, longevity, and the ability to adapt to various management systems. However, in such divergent feeding systems, the relative importance of various traits can differ. In pasture systems where cow nutrient demand intentionally coincides with seasonal forage availability, the focus of selection has emphasized fertility and other fitness traits, as well as yields of milk or milk components. Breeds or strains with higher yields of protein and fat typically have advantages in grazing systems that supply milk to solids-based or cheese markets. Holstein cows with high percentages of North American ancestry can work well in grazing systems that include supplemental concentrates or partial mixed rations, particularly if calving intervals are less restrictive. Crossbred cows can be selected for use in specific grazing systems as well as for specific milk markets, with the added advantage of heterosis. Breeds and crosses with high fertility are important for seasonal breeding and calving. The ability of cattle to both milk and maintain sufficient body condition for reproduction is important for any dairy production system but is critical in a seasonal system. Dairy farms that depend on pasture for most of dry matter for cows typically have lower production per cow than nongrazing dairies but have the potential to be economically competitive because of lower operating and overhead costs. Although the principles of selection are similar across a variety of pasture-based and nonpasture systems, we document from studies and observations covered herein that optimal breeds, breed strains, and selection strategies can differ based on varying management constraints and objectives.     

表面改性牧草纤维与橡胶粉的耦合作用对水泥胶砂力学性能的影响

废旧橡胶粉的循环应用可以有效减轻环境污染,同时,牧草纤维的利用被视为低碳建筑工业的重要举措.为了充分利用这两种材料,以掺入表面改性牧草纤维和废旧橡胶粉的水泥胶砂为研究对象,通过水泥胶砂力学性能试验和微观角度分析,研究了表面改性牧草纤维和不同目数及掺量橡胶粉对水泥胶砂力学性能的影响.试验结果表明:掺入表面改性牧草纤维能有效提升水泥胶砂的抗折性能.同时掺入改性牧草纤维和橡胶粉的试验组韧性性能优于单独掺入改性牧草纤维的试验组.当改性牧草纤维掺量为2 kg/m3,掺量为2％的20目橡胶粉的水泥胶砂强度最好.     

Prediction of ruminal pH from pasture-based diets

This study identified suitable predictors of ruminal pH and identified relationships between ruminal pH and animal measures for diets based on fresh pasture. Animal and dietary variables (121 treatment means from six countries) were collated from 23 studies of lactating dairy cows fed pasture. Mean daily ruminal pH ranged from 5.6 to 6.7 across studies. Within studies, a low ruminal pH was associated with higher (P < 0.05; r2 > 0.40) microbial N flow from the rumen, total and individual volatile fatty acid concentrations, milk and milk component yields, and dry matter intake, and with lower (P < 0.05; r2 > 0.30) concentrations of milk fat, fat:protein, and acetate:propionate. Large variation between studies meant that these ruminal and production variables could not be used to make reliable predictions of ruminal pH in future pasture-based studies or feeding scenarios. Ruminal pH was positively related (P < 0.05; r2 < 0.15) to forage neutral detergent fiber (NDF) and NDF content within study, and negatively related (P = 0.001; r2 = 0.14) to nonstructural carbohydrate across studies. No single dietary variable, or group of variables, could be used to make a reliable prediction of ruminal pH. Estimates of effective fiber for diets containing only pasture were made using the Cornell Net Carbohydrate and Protein System ruminal pH equation. Mean effectiveness of fiber in pasture was 43% of NDF, and ranged from 17 to 78% across studies. High flows of microbial nitrogen, milk, milk fat yield, and dry matter intake suggested that the performance of cows fed high quality pasture was not limited when mean ruminal pH decreased to 5.8.     

Milk response to concentrate supplementation of high producing dairy cows grazing at two pasture allowances

Twenty multiparous Holstein cows (four ruminally cannulated) in five 4 x 4 Latin squares with 21-d periods were used to study the effect of concentrate supplementation when grazed at two pasture allowances. The four dietary treatments resulted from the combination of two pasture allowance targets (low, 25 vs. high, 40 kg of dry matter/cow per day) and two concentrate supplementation levels (zero vs. 1 kg of concentrate/4 kg of milk). Concentrate supplementation decreased pasture dry matter intake 2.0 kg/d at the low pasture allowance (17.5 vs. 15.5 kg/d) and 4.4 kg/d at the high pasture allowance (20.5 vs. 16.1 kg/d). Substitution rate was lower at the low pasture allowance (0.26 kg pasture/kg concentrate) than at the high pasture allowance (0.55 kg of pasture/kg of concentrate). Total dry matter intake of both supplemented treatments averaged 24.4 kg/d. Milk production of both supplemented treatments averaged 29.8 kg/d, but was increased with higher pasture allowance in the unsupplemented treatments (19.1 vs. 22.2 kg/d). Milk response to concentrate supplementation was 1.36 and 0.96 kg of milk/kg of concentrate for the low and high pasture allowances, respectively. Concentrate supplementation reduced milk fat percentage but increased milk protein percentage. Rumen pH and NH3-N concentration were decreased with concentrate supplementation. Substitution rate was likely related to both negative associative effects in the rumen (reductions in rumen pH, rate of pasture digestion, and NDF digestibility) and reductions in grazing time. The latter was more important, quantitatively explaining at least 80% of the reduction in pasture dry matter intake observed.     

Effectiveness of single and coastal superposphates applied either in autumn or spring

Phosphorus (P) is known to leach laterally in water flowing during winter over pasture growing on flat soils that are shallow sands over slowly permeable lateritic ironstone gravel or clay soils in the high rainfall (> 800 mm annual average) areas of south-western Australia. The climate is Mediterranean, with hot dry December to March and cool wet April to November growing season, with excess water flowing over the surface from June to early-August. Fertilizer P is presently applied at about mid-March, near the start of the growing season. Single superphosphate has been applied for many years, which has a good residual value, and so the soils are no longer acutely P deficient. Consequently, a better method may be to apply the fertilizer at mid-August, after waterlogging and P leaching have usually receded, and radiation and temperature are rising, so pasture growth is increasing. The field experiment reported here was on a shallow sand over lateritic ironstone gravel where lateral leaching of P occurs. The experiment compared from 1990 to 1994 the effectiveness of single superphosphate (SSP), the fertilizer used at present, and coastal superphosphate (CSP), a partially acidulated rock phosphate containing about half the total P and one third the water-soluble P initially present in SSP. The fertilizers were applied annually either at mid-March or at mid-August. SSP applied at mid-March was the most effective treatment studied in the years when pasture plants had emerged before fertilizer was applied at mid-March. This is attributed to pasture plants being able to take up P from SSP applied at mid-March before leaching of P occurred, so that relative to SSP applied at mid-March, the other P fertilizer treatments (CSP applied at mid-march and mid-August, SSP applied at mid-August) were about equally or less effective. However, in years when the growing season had yet to start before fertilizer was applied at mid-March, then relative to SSP applied at mid-March, the other fertilizer treatments were equally or more effective. This is attributed to extensive leaching of P from SSP applied at mid-March, so that due to P losses from SSP applied at mid-March, the other treatments were equally or more effective. It is therefore concluded that profitable pasture production with reduced leaching is achieved by applying SSP at mid-March if soils are moist and pasture plants are growing at that time. However, if the soils are dry and no pasture plants are growing at mid-March, then CSP should be applied at mid-August.     

Pasture intake and substitution rate effects on nutrient digestion and nitrogen metabolism during continuous culture fermentation

A continuous culture system was used to investigate ruminal digestion in response to increased pasture intake and three different substitution rates (SR) in a 4 x 4 Latin square design. The treatments were 1) low pasture (55 g dry matter (DM)/d, 2) medium pasture (MP, 65 g DM/d), 3) high pasture (75 g DM/d), and 4) pasture (45 g DM/d) plus concentrate (PC, 30 g DM/d). Treatments were designed to produce a low (0.33), medium (0.67), and high (1.00) SR (g of pasture/g of concentrate) by contrasting the low, medium, and high pasture intake treatments with the pasture plus concentrate treatment, respectively. Pasture was fed at 0630, 1000, 1730, and 2100 h, and concentrate at 0600 and 1700 h. Digestibility of DM and neutral detergent fiber were not affected by the amount of pasture. As the amount of pasture increased, pH decreased linearly, and total volatile fatty acid and NH3-N concentrations, and nonammonia N and bacterial N flows increased linearly. Concentrate supplementation did not affect DM digestibility at high SR but increased DM digestibility at low SR. Concentrate supplementation reduced pH and NH3-N concentrations at the three SR. Concentrate supplementation reduced the ratio of rumen degradable N to rumen degradable organic matter; however, the mechanism depended on the SR. High SR, concentrate supplementation reduced rumen degradable N, which reduced NIH-N concentration without affecting bacterial N flow. At low SR, concentrate supplementation increased rumen degradable organic matter, which reduced NH3-N concentration and increased bacterial N flow. Based on these results, at low SR, concentrate supplementation may enhance animal performance because of higher total DM intake and synthesis of microbial protein.