Impact of feeding pattern and feed purchase on area- and cow-related dairy performance of organic farms

Livestock production and ruminants in particular are an integral part of the organic mixed farming concept. In this paper, the feeding patterns of 26 organic dairy farms in two different regions in Germany are analysed, with particular emphasis on the amount and proportion of concentrates and purchased feed related to the dairy performance expressed per cow and hectare. Calculated on an energy basis (MJ NEL), the annual average milk yield of 6737 kg cow^− 1 is derived from roughage (74%), concentrates and cobs (23%), and commercial processing by-products (e.g., spent grains) (3%). Per cow and year, 937 kg dry matter (DM) (range: 0–2724 kg) of concentrates are fed with an intensity of 135 g kg^− 1 milk (range: 0–378 g kg^− 1). Approximately 65% of the concentrates and commercial processing by-products are purchased. The area-related milk yield is almost 7000 kg ha^− 1. For fodder production, 0.96 ha per cow is needed, of which 0.85 ha is farm land. The equivalent production area for purchased fodder is 0.11 ha. In the analysed region in northwestern Germany, most correlations between milk yield and analysed feeding parameters are close and significant. This is in contrast to the region in the south, where the variability of amount and proportion of the different feed types is predominantly independent of the milk yield. Intensification of dairy production to increase milk performance using a higher proportion of concentrates and purchased feed at some of the analysed farms needs to be carefully assessed according to the organic farming profile.     

Effect of the type of silage on milk yield,intake and rumen metabolism of dairy cows grazing swards with low herbage mass

The aim of this study was to evaluate the effect of herbage allowance (HA) and type of silage supplemented (TS) on milk yield, dry matter intake (DMI) and metabolism of dairy cows in early lactation. Thirty‐six Holstein‐Friesian dairy cows were allocated to four treatments derived from an arrangement of two HA (LHA = 17 or HHA = 25 kg of DM/cow/day) and two TS (grass (GS) or maize (MS)). Herbage allowance had no effect on DMI or milk yield. Rumen pH and NH₃‐N concentration were not affected by HA. The efficiency of microbial protein synthesis in the rumen (microbial protein (MP)) was affected by HA with 21.5 and 23.9 g microbial nitrogen per kg ruminal digestible organic matter for LHA and HHA, respectively (P < 0.05). Supplementation with MS showed higher values of milk yield by 2.4 kg/cow/day (P < 0.001), milk protein content by 0.10 % (P < 0.023) and herbage DMI by 2.2 kg/cow/day, and showed lower values for milk urea compared to GS (P < 0.001). The former results suggest that TS had a greater effect on milk yield, total feed intake and energy intake than increase in herbage allowance; however, increase in HA had greater effects on MP than TS.     

Effect of strategies regarding concentrate supplementation and day-time grazing on N utilization at both field and dairy cow level

N utilization at cow and field level was examined over two grazing periods of 30 days with 64 Holstein dairy cows. At cow and field level the effect of sward type (diploid vs. tetraploid perennial ryegrass, both mixed with white clover) and compressed sward height (6 vs. 10 cm) was examined. At dairy cow level the effect of urea supplementation (0 vs. 145 g/day) and energy supplementation strategy (soy hulls(am)/barley(pm) vs. barley(am)/soy hulls(pm)) was also examined. Cows grazed grass/clover swards for 7.5 h/day and were restrictively fed in the barn (3.2 kg dry matter (DM) in maize silage, 3.6 kg ground barley, 3.6 kg soy hulls per day). In none of the two periods were yield of milk (Period 1: 30.9 kg, Period 2: 25.4 kg), fat, protein and lactose significantly affected by sward type, sward height, urea supplementation or energy supplementation strategy. Urea supplementation increased the urea concentration in milk. Also low sward height and feeding soy hulls(am)/barley(pm) increased the urea concentration, probably due to a higher protein content in the sward and a higher grass intake, respectively. N utilization at cow level was highest with high sward height and no urea supplementation. Feeding soy hulls(am)/barley(pm) increased milk yield numerically but was counterbalanced by an equivalent increase in estimated grass intake, and supplementation strategy seemed therefore not to affect N utilization. At field level the N surplus was higher on diploid than on tetraploid swards (50 and 21 kg N/ha) due to a higher clover content in the diploid swards, whereas the difference in N surplus between sward heights was minimal (32 and 38 kg N/ha). Estimated N removal from the pasture in the grazing periods (intake minus excretion) increased by 5.2 kg N/ha when feeding soy hulls(am)/barley(pm), whereas with no urea supplementation the net N removal increased by only 2.5 kg N/ha. It was concluded that N utilization in dairy cows can be improved by decreasing N intake from both herbage and supplementary concentrate without compromising milk yield, and that N balance at field level could be improved by strategic barn feeding.     

Nitrogen efficiency of dairy cows as affected by diet and milk yield

The aim of this study, which was part of the EU-financed project Life Ammonia, was to evaluate the effects of dietary components and milk production on nitrogen efficiency of dairy cows. The study included examining the effects of decreased crude protein (CP) concentration in a grass-clover silage based diet and results of mixing whole-crop barley silage (WCBS) with grass-clover silage in the diet, on feed intake, milk production and nitrogen efficiency. Rations were formulated and milk production data were registered individually each month for 42 cows of the Swedish Red Cattle breed during four indoor periods from 1999 to 2003. The range in nitrogen efficiency by the cows, 11 to 398 days in milk, was 18 to 40%, when fed a diet containing 135 to 184 g CP/kg DM, 44 to 56% of NDF as rumen degradable fibre (RDF) and milking 13 to 57 kg of ECM daily. The average CP concentration of the diet, containing mainly grass-clover silage and concentrate, was decreased from 168 g/kg DM (170 g in early lactation) in the control treatment period to 160 g/kg DM (163 g in early lactation) during the following treatment period. The CP concentration was 170 g/kg DM (171 g in early lactation) during the third treatment period, when the grass-clover silage was fed in a mixture with WCBS. Using the whole data set (n = 284 for primiparous, n = 440 for multiparous cows based on measurements each month) resulted in models, in which total DM intake, ECM yield, dietary CP concentration and RDF were the most important factors affecting nitrogen utilisation of primiparous and multiparous cows. Increases in both average DM intake and milk yield by multiparous cows and no changes in average intake and milk yield by primiparous cows fed the low CP diet or the normal CP diet containing WCBS, compared to cows fed the normal CP diet, resulted in similar nitrogen efficiencies among the treatments. Hence, dietary CP concentrations of 160 to 170 g/kg DM can be used for cows in early lactation in commercial herds to improve nitrogen utilisation without causing a simultaneous decrease in milk yield.     

Early lactation dairy cows: Development of equations to predict intake and milk performance at grazing

The objectives of this study were to examine the effect of parity and days in milk (DIM) on dry matter intake (DMI) and actual milk yield (MY_Act) of grazing spring calving dairy cows in early lactation (< 100 DIM) and to develop equations to predict DMI and milk yield for grass based systems of milk production. A dataset containing 335 observations from 134 Holstein Friesian dairy cows was assembled from two early lactation grazing studies. Observations were available for primiparous (n = 130) and multiparous (n = 205) cows during periods of DMI measurement using the n-alkane technique. Animal performance was divided into two classes of DIM: less than 50 DIM (< 50 DIM) or between 51 and 100 DIM (> 50 DIM). Parity and DIM had a significant effect on grass DMI (GDMI), total DMI (TDMI), MY_Act and milk composition. TDMI increased with parity and DIM and ranged from 13.4 kg/cow per day (primiparous animals, < 50 DIM) to 20.1 kg/cow per day (multiparous animals, > 50 DIM). Actual MY increased with parity and decreased with DIM (range: 24.1 kg/cow per day (primiparous animals, > 50 DIM) to 33.0 kg/cow per day (multiparous animals, < 50 DIM)). Multiparous cows had greater bodyweight (BW) and lower BCS than primiparous cows. In the early lactation period a number of variables had a significant effect on GDMI, TDMI and milk yield. These predictor variables included BW, BCS, potential milk yield (MY_Pot), DIM, daily herbage allowance (DHA; > 4 cm), concentrate level and parity. The equations accounted for 79%, 83% and 86% of the variation in GDMI, TDMI and milk yield, respectively. Actual milk yield was always below the MY_Pot of the cows, the mean difference was 5.8 kg/cow per day. As DHA and concentrate level increased, the difference between MY_Act and MY_Pot reduced. This study supports the concept that immediately post-calving offering a grass based diet with a medium level of concentrate supplementation is sufficient to support high milk production in grazing dairy cows.     

Energy intake and requirement of dairy cows during the whole year

It is argued that in view of the many new methods in dairy farming an economic model of the dairy farm should be available to improve advisory work. Some quantitative data concerning the dairy cow needed for such a model are given. They deal with a net energy feeding value of grass, hay, silage, artificially dried grass and concentrates estimated with a feed evaluation system based on results obtained with lactating cows. Also data on the requirements for net energy and for long forage dry matter are given, again obtained with such cows. Finally information is given on voluntary intake of forage dry matter at pasture, from fresh grass fed indoors, from various preserved forages including forage pellets, as influenced by milk yield and condition of the cow and by kind of forage and level of concentrates fed. Special attention has been paid to the precision of the information. These data are used to predict both the maximal and minimal amounts of long forage which can be fed in the stall period without loss of production, and the additional quantities of concentrates needed. For the grazing cow the problem of the adjustment of voluntary intake of grass to milk yield and amount of concentrates fed is studied. It is concluded that the information is sufficient to develop an economic model of a dairy farm. For its development grassland research should supply data on pasture yield in terms of digestible organic matter when the forage is fed to sheep at the maintenance level, and the economists should add data on costs of food and labour.     

Estimation of Milk Production from Smallholder Dairy Cattle in the Coastal Lowlands of Kenya

A study was carried out on 92 smallholder farms in Kwale district in Coast Province of Kenya to estimate the milk yield. The effect of concentrate feed supplementation on milk yield was also evaluated. Data were collected during a one-year observational longitudinal study. Analysis was done for 371 observations following 63 calving events. The mean annual milk offtake was estimated at 2021 kg/cow. Forty-nine (77.8%) of the lactating cows were supplemented with concentrate feeds at varying rates of 0.5-3.0 kg/cow per day. Supplementary feeding of lactating cows led to a significantly higher mean daily milk yield compared to non-supplemented cows throughout the year (p < 0.05). The mean annual milk offtake from supplemented cows (2195 kg/cow) was 18.6% more than offtake from non-supplemented cows, a difference that was statistically significant (p < 0.05). Therefore, supplementary feeding of commercial feed concentrates was a rational management practice. It was also concluded that milk production from smallholder dairy cows in the coastal lowlands of Kenya was comparable to that from similar production systems but lower than national targets.     

Performance of spring-calving beef suckler cows and their progeny on four contrasting grassland management systems

Data were collected over four consecutive years from four, rotationally grazed, grassland management systems each with 15 spring-calving beef suckler cows and their progeny to 13 months of age. The Systems were high stocking rate (SR), high fertiliser nitrogen (N), 2 silage harvests — HH2; high SR, low N, 2 silage harvests — HL2; low SR, low N, 2 silage harvests — LL2, and low SR, low N, 1 silage harvest — LL1. High and low SR were 0.49 and 0.59 ha cow^− 1 unit, respectively, and high and low N amounted to an annual input of 239 and 57 kg ha^− 1 on the grazing areas, respectively. Where applicable, the four Systems received 114 and 80 kg of N ha^− 1 for the first and second silage harvests, respectively. Equal areas of Systems HH2, HL2 and LL2 were conserved as silage (0.29 and 0.21 ha for first (24 May) and second (4 August) harvests, respectively cow^− 1 unit) each year. Silage from System LL1 (0.37 ha cow^− 1 unit) was conserved 14 days after the other first harvests. Following the final harvesting for silage within any System these areas of grassland were then grazed. During the winter all animals were housed and cows were offered grass silage and calves were offered silage plus 1 kg of concentrate per head daily. Good cow and calf performance at pasture were obtained at both high SR and high N or low SR and low N. At the high SR, increasing the level of fertiliser N application increased cow liveweight gain at pasture by 24 kg, improved body condition score (BCS) gain at pasture by 0.36 units and prolonged the grazing season by 7 days. Similarly, at the low level of fertiliser N, reducing the SR, increased cow liveweight gain at pasture by 21 kg, improved BCS gain at pasture by 0.23 units and prolonged the grazing season by 7 days. At the low SR all the winter silage requirements could be provided in one as opposed to two harvests thereby reducing the conservation area. However, delayed harvesting of silage resulted in lower silage digestibility and reduced calf performance in winter. The results indicate the specifications for a planned lower N grassland system, particularly where qualification for EU environmental schemes is dependent on moderate stocking densities.     

EM发酵玉米秸秆和青贮玉米秸秆对奶牛生产性能的对比试验

本试验应用EM发酵玉米秸秆和青贮玉米秸秆饲喂奶牛,以观察两种方法处理的玉米秸秆对奶牛生产性能及经济效益的影响效果。结果表明,用EM发酵的玉米秸秆饲喂奶牛较青贮玉米秸秆饲喂奶牛,每天每头奶牛采食量提高1.03%,平均产奶量提高2.02%,经济效益提高0.13元;EM原液发酵的玉米秸秆和青贮玉米秸秆1∶1混合饲喂奶牛,每天每头奶牛采食量、平均产奶量、经济效益分别比饲喂青贮玉米秸秆的奶牛提高2.85%、2.99%和1.15元。     

Effects of body condition score at calving and feeding various types of concentrate supplements to grazing dairy cows on early lactation performance

The objective of the experiment reported here was to establish the effect of canola meal supplements of different protein degradability on the performance of grazing dairy cows with different body condition scores (BCS) in early lactation, and to compare this with feeding a cereal grain supplement instead. The experiment included a total of 72 cows in six treatments in a 2 ^* 3 factorial design, incorporating two BCS at calving (4.1 and 5.6 units on an 8-point scale), and three early lactation pelleted supplements. The three pelleted supplements were 100% wheat (wheat supplement), 50% wheat and 50% untreated mechanically extracted canola meal (a rumen degradable protein supplement), and 50% wheat and 50% canola meal that had been subjected to additional heat and pressure (a rumen undegradable protein supplement). It was hypothesised that fat cows would perform best with the treated canola meal supplement, which provided most rumen undegradable protein, whereas the type of protein would not be important for thin cows, and neither would the type of supplemental energy. Cows grazed pasture after calving at a daily pasture allowance of 35–40 kg DM/cow and were offered 6 kg concentrates each day. Cows were fed these diets for 92 days on average, from calving until three weeks into the mating period. Both canola meal-based supplements resulted in higher (P < 0.05) daily milk production than the wheat supplement (33.3 and 34.0 v. 30.5 kg/cow) in both thin and fat cows. Body condition score at calving positively (P < 0.05) affected average milk yield (31.6 v. 33.7 kg/cow), however, there was a time × BCS × supplement interaction whereby the fatter cows benefited from the use of either of the canola meal supplements for a longer period than did the thin cows. Average milk fat concentrations were greater (P < 0.05) where the canola meal supplements were fed (39.3 and 39.6 v. 35.6 g/kg), and in fat cows relative to thin cows (40.0 v. 36.3 g/kg). Serum urea concentrations were significantly (P < 0.05) lower in cows fed wheat than in those fed either of the canola meal supplements (3.1 v. 4.3 and 4.2 mmol/L). Serum β-hydroxybutyrate concentrations were lowest (P < 0.05) where wheat pellets were fed, and highest (P < 0.05) where treated canola meal pellets were fed, and plasma glucose concentrations were highest with wheat and lowest with the treated canola meal pellets. Thus, the hypothesis was not supported by the results of this experiment.     

不同方式处理的全株玉米青贮对奶牛生产性能和经济效益的影响

[目的]探究不同方式制备的全株玉米青贮饲喂奶牛后,对其生产性能和经济效益的影响。[方法]选定中国荷斯坦牛开展全株玉米青贮饲喂试验。将28头奶牛随机分为对照组和试验组,每组14头。前者饲喂不添加菌剂制备的全株玉米青贮,后者饲喂添加青贮菌剂制备的全株玉米青贮。统计各组奶牛日均干物质采食量、日均产奶量、料重比、乳脂率和乳蛋白率,计算各组奶牛日均经济效益和试验期总经济效益。[结果]采用添加青贮菌剂制备的全株玉米青贮饲喂奶牛后,奶牛日均干物质采食量和料奶比与对照组差异不显著,但日均产奶量、平均乳脂率和乳蛋白率显著提高（P<0.05）。每头牛日均产奶量增加1.91 kg,乳脂率增加0.22个百分点,乳蛋白率增加0.06个百分点。试验组经济效益明显提高,每头牛日均经济效益增加4.73元,正试期内总经济效益增加1 986.60元。[结论]采用添加青贮菌剂的全株玉米青贮饲喂奶牛,能有效提高奶牛的生产性能和经济效益。     

Relationship between feeding behaviour and feed intake of dairy cows depending on their parity and milk yield

To investigate the relationship between the parameters of feeding behaviour and feed intake, 70 lactating dairy cows (23 primiparous and 47 multiparous) were monitored from the 2nd to 15th week of lactation. Data were collected by using an automatic feeder and electronic identification of individual cows from 10 July 2005 to 16 January 2006. The resulting data of the cows in primiparous and multiparous condition were categorised into groups based on the mean of their milk yield over the first 15 weeks of lactation: primiparous cows with below-average milk yield (LP) and above-average milk yield (HP) with an average of 28.44 and 34.31 kg energy-corrected milk (ECM) per day, respectively, and multiparous cows with below-average milk yield (LM) and above-average milk yield (HM) with an average of 38.70 and 44.49 kg ECM per day, respectively. The parameters of feeding behaviour were calculated based on the estimated meal criterion from pooled data. Parity, level of milk yield, and day had significant effects on some of characteristics of feeding behaviour and feed intake parameters. There was no significant difference in meal duration either between primiparous and multiparous cows or between LP and HP. However, a significant difference between LM and HM was observed. Cows in HM had shorter feeding times but a larger meal size, higher DMI, and feeding rate. Moreover, these cows displayed a stronger correlation between meal duration, daily mealtime and daily feed intake (r = 0.37 and 0.50, P < 0.001, respectively) than any other cow or group of cows of the study. Meal duration, daily mealtime, meal size and daily DMI increased on average about 32%, 20%, 35%, and 22% respectively, considering all milk yield groups from the 2nd to 15th week of lactation.     

Effect of herbage allowance and concentrate supplementation on dry matter intake, milk production and energy balance of early lactating dairy cows

The objective of this study was to investigate the effect of daily herbage allowance and concentrate supplementation level offered at approximately 40 and 80 days in milk (DIM) and the carryover effects at 120 DIM on the production performance of spring calving dairy cows. Sixty-six (30 primiparous and 36 multiparous) Holstein–Friesian dairy cows (mean calving date — 7 Feb ± 9.9 days) were randomly assigned to a 6 treatment (n = 11) grazing study. The experiment was a randomised block design with a 3 × 2 factorial arrangement of treatments (3 daily herbage allowances (DHA's; approximately 13, 16 and 19 kg DM/cow/day; > 4 cm) and 2 concentrate allowances (0 and 4 kg DM/day). Treatments were imposed from 21 February to 8 May. Following this period (subsequent 4-weeks) animals were offered a daily herbage allowance of 20 kg DM/cow/day and no concentrate. Milk production, total dry matter intake (TDMI), energy balance (EB) and blood metabolites were measured on three occasions — at approximately 40, 80 and 120 days in milk, R1, R2 and the carryover period, respectively. Cows offered a low DHA had a lower post-grazing sward height but increased sward utilisation (> 4 cm) during R1 and R2, there was no difference during the carryover period. Concentrate supplementation increased post-grazing sward height by 11% during R2 but had no effect during R1 and the carryover period. Daily herbage allowance had no effect on milk yield or composition during R1 however a low DHA tended to reduce milk yield in R2. Concentrate supplementation increased milk and solids corrected milk (SCM) yield by 4.1 and 2.8 kg/cow/day, respectively during R1 and also increased R2 milk production performance, this effect extended into the carryover period. Offering a low DHA restricted grass dry matter intake (DMI) during R1 and R2 yet concentrate supplementation significantly increased total DMI (2.3 (R1) and 3.0 (R2) kg DM/cow). Animals offered a low DHA had a significantly lower bodyweight (BW) than those offered a medium or high DHA during P1 and P2. Concentrate supplementation increased BW during P1 and P2 (+ 9 and + 14 kg/cow, respectively). There was no effect of treatment on BW during P3. There was no effect of DHA on EB in R1; during R2 animals offered a low DHA had the lowest EB. Concentrate significantly increased EB in R1 and R2 and increased plasma glucose concentration while it decreased plasma NEFA and BHB concentrations. The results of this study indicate that animals should be offered a low DHA up to 80 DIM after which DHA should be increased however animals should also be supplemented with concentrate during the early post-partum period.     

Effects of toasting blue lupins, soybeans or barley as supplement for high-yielding, organic dairy cows fed grass-clover silage ad libitum

The effect of toasted supplement on milk production was examined in three experiments on an organic study farm during the winter 2004/2005. Three types of iso-energetic supplement feed, toasted or untreated, were examined in each experiment, with an untreated cereal mixture as control. The supplement under investigation was: lupins in experiment 1, barley in experiment 2 and soybeans in experiment 3. The same forage mixture of grass-clover silage (84% of DM), grass pellets (11% of DM) and straw (5% of DM) was fed ad libitum in all the experiments.

Toasting decreased effective rumen protein degradability determined in situ for all three supplements. Compared to untreated lupins toasting of lupins tended (P = 0.10) to increase milk yield, whereas toasting of soybeans did not affect milk yield. Toasting of lupins decreased (P = 0.03) milk protein content (32.2 versus 32.7 g/kg), whereas toasting of soybeans did not affect milk protein content. ECM yield was significantly higher (P = 0.002) for cows fed toasted soybeans than for cows fed untreated soybeans (28.1 versus 26.4 kg ECM) whereas there was no significant effect on ECM yield from toasting lupins or barley. It can be concluded that the potential of toasting to increase the supply of metabolisable protein under organic feeding conditions is variable between feeds.     

Heat production, eating behavior and milk yield of lactating cows fed two rations differing in roughage content and digestibility under heat load conditions

The objective of this study was to measure the effect of feeding two total mixed rations (TMRs), differing in their roughage content and in vitro dry matter digestibility, on the respiratory rate, body temperature, eating behavior and energy balance of lactating cows. The partitioning of metabolizable energy intake (MEI) between heat production (HP) and retained energy (RE) of cows held under heat load conditions was measured. Forty-two lactating cows were divided into two similar sub-groups, each of 21 animals, and were fed either a control (CON) ration containing 18% roughage neutral detergent fiber (NDF) or an experimental (EXP) TMR that contained 12% roughage NDF and used soy hulls as partial wheat silage replacer. The in vitro DM digestibility of the CON and EXP TMRs was 75.3 and 78.6%, respectively (P < 0.05). The EXP diet reduced rectal temperature and respiratory rate of the cows while increasing their number of meals per day by 32.7% as compared with the CON fed cows, and these meals were shorter in duration and were eaten faster. The EXP diet increased total DM intake from 19.6 to 21.5 kg/cow/d, milk yield from 32.3 to 34.6 kg, and yield of energy corrected milk from 30.9 to 32.2 kg, as compared with the CON group. Cows fed the EXP TMR had increased RE in milk and body tissue, as compared with the CON group, but the diets had no effect on the measured HP that was maintained similar (121 vs. 127 MJ/cow/d) in the two groups. The measured MEI (MEI = RE + HP) and the efficiency of MEI utilization for RE production, were similar in the two dietary groups.     

Whole sunflower seeds as a source of polyunsaturated fatty acids for grazing dairy cows: Effects on metabolic profiles and resumption of postpartum ovarian cyclicity

Intake of polyunsaturated fatty acids (PUFA) could modify follicular dynamics and reduce the length of the interval from calving to first ovulation (ICOV) in dairy cows, associated with changes in metabolites (i.e. cholesterol) or hormones (i.e. IGF-I). To test this hypothesis, 48 cows were stratified in two groups (primiparous or multiparous) and within each group were randomly assigned to three treatments to begin at calving: 0 kg (SS0), 0.7 kg (SS0.7) and 1.4 kg (SS1.4) of whole sunflower seeds (WSS) per cow per day. The experimental period lasted for 60 days after calving and the diets, which consisted of direct grazing of improved pastures, whole-plant wheat silage and concentrates, were designed to be isocaloric and isoproteic (1.6 Mcal NEL/kg DM, 16.7% CP). Ovaries were examined by ultrasound three times per week from day 8 postpartum (PP) until first PP ovulation. Body condition score (BCS) was determined and blood samples were collected weekly from calving to characterize the metabolic profiles. In treatments SS0.7 and SS1.4, 7/8 and 6/8 primiparous cows ovulated the first follicular wave PP, compared with only 1/8 primiparous cow in treatment SS0, while there were no treatment differences in multiparous cows. The ICOV was 44, 21 and 19 days for the primiparous, and 22, 21 and 25 days for the multiparous cows, in treatments SS0, SS0.7 and SS1.4, respectively. Treatments had no effect on BCS, plasma IGF-I and metabolic profiles except that NEFA and urea were increased by WSS supplementation. Intake of PUFA (WSS up to 1.4 kg/day or 6.7% of the diet) during early lactation reduced the ICOV in primiparous grazing dairy cows in early lactation but not in multiparous cows, and while the precise mechanism for these results is unclear, it was not related to changes in the plasma concentrations of IGF-I or cholesterol.     

饲用甜菜块根混贮饲喂荷斯坦牛的试验研究

采用75%切碎的饲用甜菜根茎与15%芦苇草粉、8%棉籽壳及2%玉米粉进行混合青贮,并替代荷斯坦奶牛常规日粮中的部分玉米青贮,进行饲喂对比试验。结果表明,饲用甜菜混贮饲料干物质含量为27.8%、粗蛋白含量为2.76%、粗脂肪含量为0.92%、粗纤维含量为11.28%、粗灰分含量为3.23%、钙含量为0.10%和磷含量为0.04%。饲用甜菜混贮饲料等量替代10kg奶牛日粮中的玉米青贮饲喂奶牛,试验组比对照组每头奶牛日平均产奶量降低0.09kg,试验末期对照组和试验组的乳蛋白率分别为3.17%和3.18%,乳脂率分别为3.66%和3.73%,分析结果表明,产奶量及乳品质差异均不显著。可见饲用甜菜块根混贮是一种较好的饲料,可以替代玉米青贮饲喂奶牛,混贮是饲用甜菜块根一种理想的贮藏方法。     

Milk production responses to pre- and postcalving dry matter intake in grazing dairy cows

Sixty-eight multiparous grazing dairy cows were randomly allocated to two precalving pasture allowances to achieve differential dry matter intakes (DMI) for 29 ± 7.7 d precalving (Low or High DMI; 4.8 or 11.9 kg DM). At calving, cows within each precalving treatment were randomly allocated to one of two levels of feeding (Low or High DMI; 8.6 or 13.5 kg DM) for 35 d postcalving in a completely randomized design and a 2 × 2 factorial arrangement of treatments. Following treatments all cows grazed together and were fed pasture and pasture silage. Daily milk yields were recorded, and fat, protein and lactose concentrations determined weekly for 15 weeks. Blood was sampled weekly pre- and postcalving and analysed for indicators of energy status, growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Body condition score (BCS) at calving was reduced by precalving restriction (P < 0.001; 2.8 and 3.0 for precalving Low and High treatment groups, respectively). Precalving restriction reduced milk fat production by 8.4% during the first 5 weeks postcalving, but differences were not significant subsequently. Postcalving feed restriction reduced yield of fat corrected milk (FCM), fat and protein by 23, 21 and 28%, respectively, during the first 5 weeks postcalving. Decreased (P < 0.05) yields of FCM, fat and protein (11, 10 and 9%, respectively) were also evident for 10 weeks after the feed restriction finished. There was a tendency (P < 0.1) for a precalving × postcalving DMI interaction in milk protein yield during the first 5 weeks of lactation with no effect of precalving level of feeding in cows that were restricted postcalving. The plasma concentrations of non-esterified fatty acids (NEFA), β-hydroxybutyrate (BOH) and GH were elevated in restricted cows precalving, and IGF-1 concentration was reduced. Plasma NEFA and BOH concentrations were elevated postcalving in restricted cows, but no effect of postcalving DMI on GH or IGF-1 concentration was evident. Results suggest that under grazing systems milk production responses to precalving DMI are small, but energy restrictions in early lactations result in significant carryover effects in milk production.     

北京地区规模化牛场玉米青贮和TMR颗粒度评价及常规营养成分研究

针对我国粗饲料资源较差以及广泛存在的青贮铡切较长等现实问题,本研究旨在为制定适合于中国饲料资源条件的青贮以及不同生长和泌乳阶段奶牛的TMR分级标准提供基础数据。本试验对北京地区规模化奶牛场的玉米青贮和TMR样品进行颗粒度筛分和常规营养成分测定,并与美国宾州颗粒度分级筛（PSPS）的TMR颗粒度和日粮NDF推荐值进行比较。通过比对发现我国玉米青贮的饲料颗粒度普遍偏大,第一层筛网上的饲料比例远超过宾州筛3%～5%的推荐值。新产牛和高产牛TMR样品位于第一层筛网上的饲料比例绝大多数超过了8%,第二层筛网上的饲料比例比美国推荐值要低15%～25%,这可能是由于粗饲料（青贮和干草）颗粒度过长造成的。高产牛和新产牛日粮NDF含量处于35%～42%,基本上在美国宾州筛推荐的中低产奶牛日粮的NDF范围,这与我国的粗饲料资源有限、质量不高、粗饲料铡切长度有关。因而,我国牧场不能照搬美国宾州筛的TMR分级标准,而应根据我国粗饲料的国情,制订适合于中国饲料资源条件的青贮与不同生长和泌乳阶段奶牛的TMR分级标准。     

Performance and Economics of Dairy Cows Fed a Corn Silage-Based Total Mixed Ration or Grazing Annual Ryegrass During Mid to Late Lactation

Economic and performance characteristics of a low cost grazing system based on annual ryegrass vs a total mixed ration (TMR) for cows during mid through late lactation were evaluated. Cattle used in the trial (28 Holstein and 12 Jersey cows) were blocked by parity, lactation number, days in milk, projected mature equivalent milk yield, and current milk yield, and cows were assigned to two treatments in a randomized complete block design. For 10 wk (March through May 1998), cows either received a corn silage-based TMR or grazed annual ryegrass and received no supplemental concentrates. Changes in feed composition, milk yield, milk composition, BW, condition score, and income over feed costs were examined. Cows on Treatment 1 were fed the TMR twice daily and were housed together in a free-stall barn. Cows assigned to grazing were allowed ad libitum access to annual ryegrass in a rotational 12-paddock system. Loose mineral was provided for ad libitum consumption, but no supplemental concentrate was offered. Daily milk production by the TMR cows was consistent, ranging between 22.5 and 27.2 kg per cow throughout the study. By contrast, daily milk production of the grazing cows declined from 26.6 to 15.9 kg per cow as lactation progressed. Ryegrass grazing reduced milk fat content during wk 4 and 8 of the study and increased MUN content during wk 2 but had no effect on milk protein content or somatic cell count. The BW, body condition score, and estimated DMI of grazing cows were less than they were for TMR cows. Milk income for the grazing cows was less than that for the TMR cows throughout the study. However, feed cost for grazing cows was substantially lower than that for the TMR cows. Hence, income over feed cost (IOFC) was greater for grazing cows than for TMR cows in all but the last 2 wk of the study. These results indicated that annual ryegrass grazing was more profitable than feeding a TMR to cows in mid to late lactation. However, grazing cows did lose body condition, which could have a negative effect on milk production in the subsequent lactation.