泌乳盛期和泌乳后期奶牛的采食行为和日粮营养物质表观消化率的对比分析

试验旨在研究不同泌乳阶段奶牛饲喂相同日粮对采食行为和日粮营养物质表观消化率的影响。选择体重、胎次相近的8头健康泌乳牛,其中4头处于泌乳盛期(泌乳盛期组),4头处于泌乳后期(泌乳后期组),2组奶牛饲喂相同日粮,预试期15 d,正试期15 d。结果表明:泌乳盛期组奶牛每天干物质采食量(24.0 kg)高于泌乳后期组(P<0.01),泌乳盛期组奶牛每千克干物质的采食时间、一昼夜总反刍时间、躺卧时间均低于泌乳后期组(P<0.01),;泌乳盛期组奶牛日粮中中性洗涤纤维和酸性洗涤纤维的表观消化率低于泌乳后期组(P<0.01)。由此可见,泌乳盛期奶牛采食时间极显著高于泌乳后期奶牛,泌乳盛期奶牛躺卧时间极显著少于泌乳后期。     

泌乳奶牛采食、反刍、逍遥行为和日粮纤维性物质表观消化率对比分析

为了对比不同泌乳阶段奶牛的采食、反刍、逍遥行为和日粮营养物质表观消化率,选择体重、胎次相近的8头健康荷斯坦泌乳奶牛,其中,4头处于泌乳盛期(泌乳盛期组),4头处于泌乳后期(泌乳后期组),进行了采食行为观察和消化试验,两组奶牛预饲期20 d,正试期15 d。结果表明,泌乳盛期组奶牛每天的干物质采食量为21.2 kg,极显著高于泌乳后期组的14.1 kg(P<0.01),但两组奶牛的采食时间和采食次数无显著差异(P>0.05),泌乳盛期组奶牛每千克DM采食的时间也极显著低于泌乳后期组奶牛(P<0.01);一昼夜总反刍时间泌乳盛期组奶牛极显著低于泌乳后期组(P<0.01),每千克DMI需反刍时间泌乳盛期组奶牛极显著低于泌乳后期组(P<0.01)。泌乳盛期组奶牛躺卧、走动和站立时间与泌乳后期组奶牛相比无显著差异(P>0.05)。泌乳盛期组奶牛日粮中NDF和ADF的表观消化率极显著低于泌乳后期组(P<0.01),两组奶牛NDF的表观消化率分别为55.8%、67.8%,ADF的表观消化率分别为44.2%、60.7%。     

Effects of Level and Degradability of Rapeseed Meal in Rations for Dairy Cows. 1. Animal Performance

Abstract

A total of 44 dairy cows of the Swedish Red and White dual-purpose breed were divided into 4 equal groups. Two groups were fed concentrate containing approximately 19% crude protein (high level), while two groups were fed concentrate containing 14.3% crude protein (low level). The differences were obtained by mixing either 25 or 8% 00-rapeseed meal into a basic grain-dominated mixture. Within each protein level, one half of the cows were allotted untreated rapeseed meal and the other half heat-treated rapeseed meal. The heat treatment decreased the effective protein degradability of the rapeseed meal by 20 units from 72 to 52%.

The experiment was commenced as a continuous experiment, where weeks 1–3 of the lactation were a preliminary period in which all cows received the same feeding. The experimental period covered lactation weeks 4–20. When the experiment was analysed, the results from the preliminary period were used as covariates.

Significant treatment effects were reached both for level and degradability. This was mainly due to a significantly lower milk and protein production on the treatment URM - low protein level. This treatment also reached a significantly lower feed energy utilization and a higher fat percentage in milk. It was concluded that evaluating the protein according to the new Nordic AAT/PBV system correlated better to milk production than did crude protein or digestible crude protein.

By using the AAT-PBV system it was possible to minimize the crude protein content in the concentrate without impairing milk production. A general conclusion is that there are benefits in the form of higher milk production and better feed utilization from decreasing protein degradability in rapeseed meal.     

Influence of feeding management, concentrate intake and energy intake on the risk of hyperketonæmia in Swedish dairy herds

The risk of hyperketonaemia (clinical and subclinical ketosis) and how it is influenced by feeding and management routines was analyzed in 291–354 dairy herds over a 3 year period. The overall frequencies of cows with milk acetone ≥ 0.40 mM ranged between 4.2 and 6.2% in Parity 1 and 12.7 and 13.8% in Parity 2+. The incidence was probably underestimated, as samples were taken once per 30 day period. The risk of hyperketonæmia was higher at low than at high feeding frequencies; most odds ratios (OR) were in the range of 1.0–2.7 for two versus four meals per day. The effect of feeding frequency was most evident on high concentrate rations. A larger amount of concentrate in early lactation was deemed to increase the risk of hyperketonæmia, but not consistently so; OR ranged between 0.4 and 2.7, with highest risks for the Swedish Red and White breed. Feeding forage before concentrate and feeding the cows a meal close to milking time reduced the risk of hyperketonæmia, but the results were inconsistent. Hyperketonæmia occurred more often in herds with feeding barriers than in short stall without feeding barrier. Our findings suggest that a high feeding frequency and a cautious feeding strategy of concentrate early in lactation are important factors in the prevention of subclinical or clinical ketosis.     

Evaluation of energy requirements of beef cows during early lactationEvaluation des besoins énergétiques des vaches allaintantes au début de lactationBestimmung des energiebedarfs von fleischrindern im frühen laktionsstadium

Two feeding trials were carried out to evaluate the energy requirements of beef cows during early lactation. Samples of thirty and thirty-four suckled cows were used from the 4th to approximately the 14th week of lactation. Levels of feeding were 80–85% (L), 100% (M) and 115–120% (H) of the theoretical energy requirements of dairy cows with the same milk production. Each cow was fed the same restricted diet in the pre- and post-experimental periods for measurements of liveweight changes. The rations consisted of 85% hay and 15% concentrate mixture. The digestibility of the diets was measured for dairy cows in late lactation.The reduced level of feeding decreased milk production and increased liveweight loss significantly (P < 0.05) from H to L treatments in the second experiment. Linear regression of daily liveweight gain on calculated daily energy balance was highly significant (P < 0.001). Cows with a zero energy-balance (calculated) had a significant weight loss of 123 g per day. No change in liveweight was obtained with a metabolizable energy intake 16.2 MJ above the theoretical energy requirement. Lack of information on the energy content of suckled milk and on changes in body composition could, at least partly, explain these results.     

Effect of lactation on functional and morphological echocardiographic variables in adult dairy cows

ObjectivesTo study the effect of pregnancy and lactation on echocardiographic parameters in Holstein dairy cows.AnimalsNine multiparous high milk producing (HMP) dairy cows (producing more than 40 kg of milk per day in peak production) and 9 low milk producing (LMP) cows (producing less than 30 kg or milk per day in peak production).MethodsEchocardiography was performed twice; one month before calving and two months after calving.ResultsThe heart rate of HMP cows in the early lactation period was significantly higher than in the dry period. In LMP cows, there was a significant increase in left ventricular dimension in the early lactation period as compared to the dry period, and the interventricular septum in systole (IVSs) in the dry period was significantly thicker than early lactation period. In HMP cows, there was an increase in the right ventricular diameter in systole in the early lactation period as compared to the dry period. Left ventricular and aortic dimensions in the dry period of HMP were significantly higher than those of LMP cows. When the data were corrected for body weight, comparison of values of the dry period of HMP and LMP cows showed that left ventricular volume in systole in HMP was significantly higher and that IVSs, left ventricular fractional shortening and ejection fraction were significantly lower than in LMP cows.ConclusionsThis study demonstrated that lactation influences the intracardiac dimensions. The amount of milk production can influence echocardiographic parameters in dairy cows.     

An investigation into reduced milk production following dietary alteration on an Irish dairy farm

A nutritional evaluation of an Irish dairy herd indicated gross overfeeding of late lactation cows, over-conditioning of cows at parturition and a high rate of body condition loss in early lactation. Metabolisable-energy based nutritional modelling software was used to guide recommended dietary changes to prevent excessive condition gain in late lactation. Immediately following the implementation of the changes there was an unexpected reduction in performance affecting both milk yield and protein concentration. An investigation into the poor performance revealed underestimation of peak milk yield; over-estimation of maize silage quality; a large difference in the concentrate being fed compared to the concentrate recommended, and failure of the blend of concentrate ingredients to maintain the intended proportions in the in-parlour feeding system. The estimated maximum cumulative effect of these errors was to cause undersupply of energy and protein in the recommended diet of 16% and 3% respectively to cows in early lactation. Use of a net-energy nutritional model would have indicated a requirement for a higher energy supply in this case. This report highlights the challenges in obtaining accurate on-farm data for use in dairy cow nutritional models.     

A field study on the effects of dietary monensin on milk production and milk composition in dairy cows

The objectives of this study were to quantify the effect of 16 ppm of dietary monensin on milk production and composition of dairy cows, and to investigate factors having a potential impact on this effect. Data were generated from a total of 3577 Holstein dairy cows (47 herds) in Quebec enrolled in a herd-level, randomized clinical trial investigating the effects of monensin supplementation. Milk production and composition data were collected from monthly dairy herd improvement (DHI) testing. Monensin increased milk production by 0.9 kg/cow/d in cows under 150 days in milk (DIM) (P < 0.05). Monensin decreased milk fat percentage by 0.18 percentage points during the whole lactation (P < 0.05). This decreasing effect was larger for component-fed cows (P < 0.05) and for cows being fed low levels of dietary physically effective particles (P < 0.05) when compared respectively to cows fed total mixed ration and cows fed high levels of dietary physically effective particles. The results of this study suggest that monensin influences milk production and milk composition of dairy cows, and that diet composition and feeding system influence those effects.     

Analyses of factors affecting dry matter intake of lactating dairy cows

An experiment was conducted to analyze feed, climate and animal factors affecting dry matter intake (DMI) in lactating dairy cows. Sixteen lactating Holstein cows, with parity from 1 to 6, were assigned to a feeding trial for 2 years, comprising 31 lactations. The animals were fed Italian ryegrass silage, oat hay, alfalfa hay, beet pulp and three types of concentrate. The data, pooled and classified by stage of lactation, season of lactation and parity were analyzed by stepwise multiple regression to determine the nature and extent of factors affecting DMI. A total of 45 prediction equations for DMI were derived. Energy‐corrected milk yield or milk yield was selected as the primary factor of DMI in all the equations in which the ratio of contribution (R²) varied from 0.26 to 0.67. The dietary concentration of organic cell wall, crude fiber, crude protein, organic b fraction, forage to concentrate ratio, average ambient temperature and temperature–humidity index were selected as the secondary factors affecting DMI for pooled data, late lactation (251–350 days of lactation), summer (June–August), spring (March–May), ≥4th lactation, autumn (September–November) and 3rd lactation, respectively, and improved R² up to 0.77. Except for an impact of bodyweight in several equations, feed and climatic factors significantly improved prediction equations effectively for data classified in different ways. To estimate DMI accurately in lactating dairy cows, feed and climatic factors should be considered for specific conditions.     

Feeding hay rich in water‐soluble carbohydrates improves ruminal pH without affecting rumination and systemic health in early lactation dairy cows

Forages rich in water‐soluble carbohydrates (WSC) might be an ideal energy source during early lactation, as they provide both energy for milk production and structural fibre to promote chewing and rumen buffering. Thus, the aim was to investigate feeding strategies based on high‐quality hay rich in WSC with graded amounts of concentrate on ruminating behaviour, ruminal pH and systemic health variables. Twenty‐four Simmental cows were randomly allocated to four groups beginning 10 days before until 28 days after calving. Diets were 60LQH (60% fibre‐rich hay plus 40% concentrate), 60HQH, 75HQH and 100HQH (60%, 75% and 100% high‐quality hay, plus 40%, 25% and 0% concentrate, respectively). Hay qualities differed in contents of WSC (110 g vs. 198 g of dry matter [DM]), neutral detergent fibre (646 g vs. 423 g of DM) and crude protein (65 g vs. 223 g of DM). Rumination was recorded using the Rumiwatch system over 4 days during the last week. Weekly serum samples were analysed for the liver enzymes aspartate aminotransferase, glutamate dehydrogenase and γ‐glutamyltransferase and the acute phase proteins serum amyloid A and haptoglobin. Four cows per group received a wireless pH sensor orally placed into the rumen one week before the expected calving date. Daily time spent chewing did not differ between groups. Likewise differences in minimum, maximum and mean pH‐values were not significant, but daily time of reticular pH <6 was longer in cows fed 60LQH compared to cows fed 100HQH (p = 0.043) and in tendency to cows fed 75HQH or 60HQH (p = 0.072 or p = 0.086, respectively). Blood parameters were unaffected by diet. Accordingly the present results demonstrate that feeding hay rich in WSC helped stabilizing the reticuloruminal pH in early lactation dairy cows, even in combination with 40% concentrates in DM.     

Adrenal cortex reactivity in dairy cows differs between lactational stages and between different feeding levels

Changes in ACTH challenge test characteristics in dairy cows changing their physiological status at different lactational stages and different feeding levels were not investigated in terms of repeatability yet. In 23 multiparous Holstein cows (10 cows fed a sole fresh herbage diet without concentrate, 13 cows fed with concentrate), three ACTH challenge tests were performed: once during pregnancy shortly prior to drying off ( T1 ), and in week 3 ( T2 ) and 8 ( T3 ) after parturition. Test characteristics were correlated to performance and metabolic parameters: DMI, BW, energy balance (EB), plasma concentrations of free fatty acids (NEFA) and beta‐hydroxybutyrate (BHB). Basal plasma cortisol concentrations were higher at T1 compared with T2 and T3 (p < .05). The adrenal cortex sensitivity (expressed as total AUC (AUC_t) of cortisol response after ACTH application) was lowest at T2 compared with T1 and T3 (p < .05). Ranking of the individual animals’ responses was not repeatable between time points of the ACTH tests. Enhancing the energy deficiency during early lactation by omission of concentrate did not affect baseline cortisol concentrations in plasma, but decreased peak height at T2 (p < .05). Baseline plasma cortisol concentrations were positively correlated with cortisol peak values after ACTH application, previous lactation performance, milk yield and BW (p < .05). The AUC_t was positively correlated with baseline cortisol concentrations, EB and DMI. Cortisol release after ACTH injection was lower in animals with high plasma concentrations of NEFA, BHB and with higher contents of fat and free fatty acids in milk (p < .05). Cortisol peak height after ACTH administration was higher in cows with a more positive EB, higher DMI and lower plasma concentrations of NEFA and BHB. In summary, cortisol responses to ACTH challenges in this study were not repeatable in dairy cows changing their physiological status.     

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).     

Evaluating the suitability of field beans as a substitute for soybean meal in early-lactating dairy cow: Production and metabolic responses

Twenty-four multiparous Holstein cows were utilized in a completely randomized design to examine the effect of feeding field beans (FB, Vicia faba L. var. minor) as substitute for soybean meal (SBM) on lactation performance and metabolic response during the early lactation period. Cows were individually divided into two equal groups and fed for 16 weeks on one each of the two experimental diets. The controls were fed pelleted concentrate contained 150 g/kg dry matter (DM) of SBM as the main protein source, whereas the experimental concentrate contained 345 g/kg DM of FB. Oat hay was offered ad libitum to cows and water was freely available. Blood samples were assayed for their content of: urea, glucose, triglycerides, cholesterol, total protein, albumin, calcium and phosphorus, aspartate aminotransferase (AST) and alanine aminotransferase (ALT), nonesterified fatty acids (NEFA) and β-hydroxybutyrate (BHBA). Inclusion of FB had no detectable effects on DM intake (DMI), body weight (BW), or body condition score (BCS). Neither milk yield nor quality were influenced by dietary treatment, except for milk urea nitrogen (MU) that was reduced in cows fed the FB diet (P < 0.05). Clotting properties of milk were not affected adversely by added dietary FB. Concentration of blood urea (BU) was lower in cows fed the FB diet than in those fed the control SBM diet (P < 0.05). These findings indicate that feeding FB in a lactation diet supported lactation performance similar to cows fed traditional SBM-based diet, and the results may elicit great interest for countries where soybean utilization is adversely influenced by high supply costs.     

Nutritional strategies to combat physiological imbalance of dairy cows during early lactation: The effect of changes in dietary protein to starch ratios

Abstract

Thirty Danish Holstein cows were used to determine how cows in early lactation adapt to changes in protein to starch supply in order to manipulate metabolism to combat physiological imbalance. During weeks 4 through 6 of lactation, 10 cows were fed either a high protein to starch ratio (high) diet, 10 cows were fed a low protein to starch ratio (low) diet while 10 others continued on the control diet. During weeks 7 through 9 of lactation, all cows returned to the control diet. The diets were formulated to consist of 15.0%, 18.6% and 22.2% crude protein and 13.3%, 7.5% and 1.7% of starch for the low, control and high diets, respectively. Besides milk urea nitrogen, no other production or metabolic parameters were affected by treatment. In conclusion, manipulation of dietary protein to starch is not a potential strategy to combat physiological imbalance during early lactation.     

Competitive behaviour of dairy cows at a concentrate self-feeder

Abstract

We investigated whether feeding cows are disturbed by butting of other cows during the time they are in a concentrate self-feeder, and whether this leads to concentrate leftovers. Forty dairy cows were observed while visiting two self-feeders. If a cow was butted visiting the self-feeder, it was considered as ‘disturbed visit’. When retreating from the feeder within five seconds after being butted, the visit was also considered ‘interrupted’. Half of the visits were disturbed, and 42% of visits were also interrupted. Visits were disturbed particularly when cows’ own feed was dispensed, and in 63% of disturbed visits concentrates were left over. The non-lactating cows, denied concentrates, won leftover concentrates after butting the previous visitor more often than lactating cows. Cows’ weight correlated negatively with visiting and receiving butting. Initiated butting correlated positively with winning leftover concentrates. There is a need for further development of automatic feeders to secure individual concentrate feeding.     

Metabolic load in dairy cows kept in herbage‐based feeding systems and suitability of potential markers for compromised well‐being

Herbage feeding with only little input of concentrates plays an important role in milk production in grassland dominated countries like Switzerland. The objective was to investigate the effects of a solely herbage‐based diet and level of milk production on performance, and variables related to the metabolic, endocrine and inflammatory status to estimate the stress imposed on dairy cows. Twenty‐five multiparous Holstein cows were divided into a control (C+, n = 13) and a treatment group (C?, n = 12), according to their previous lactation yield (4679–10 808 kg) from week 3 ante partum until week 8 post‐partum (p.p.). While C+ received fresh herbage plus additional concentrate, no concentrate was fed to C? throughout the experiment. Within C+ and C?, the median of the preceding lactation yields (7752 kg) was used to split cows into a high (HYC+, HYC?)‐ and low‐yielding (LYC+, LYC?) groups. Throughout the study, HYC+ had a higher milk yield (35.9 kg/d) compared to the other subgroups (27.2–31.7 kg/d, p < 0.05). Plasma glucose (3.51 vs. 3.72 mmol/l) and IGF‐1 (66.0 vs. 78.9ng/mL) concentrations were lower in HYC?/LYC? compared to HYC+/LYC+ cows (p < 0.05). Plasma FFA and BHBA concentrations were dramatically elevated in HYC? (1.1 and 1.6 mmol/l) compared to all other subgroups (mean values: 0.5 and 0.6 mmol/l, p < 0.05). Saliva cortisol, plasma concentrations of serum amyloid A (SAA), haptoglobin (Hp), beta‐endorphin (BE) and activity of alkaline phosphatase (AP) were not different between C+ and C?. In conclusion, herbage‐fed high‐yielding cows without supplementary concentrate experienced a high metabolic load resulting in a reduced performance compared to cows of similar potential fed accordingly. Low‐yielding cows performed well without concentrate supplementation. Interestingly, the selected markers for inflammation and stress such as cortisol, Hp, SAA, BE and AP gave no indication for the metabolic load being translated into compromised well‐being.     

Evaluation of estimated genetic merit for carcass weight in beef cattle: Blood metabolites, carcass measurements, carcass composition and selected non-carcass components

In Ireland, a new beef genetic index has been developed. Growth rate is expressed as expected progeny difference for carcass weight (EPD_CWT) and is estimated on an across-breed basis. Cross-breeding of dairy cows with both Aberdeen Angus and Belgian Blue beef sires is widely practised. The objective of this study was to compare blood metabolites, slaughter traits and carcass composition of progeny from Holstein–Friesian dairy cows and Aberdeen Angus (AA), Belgian Blue (BB), Friesian (FR) and Holstein (HO) sires. The AA and BB sires were selected, within breed, to be of either high (H) or low (L) estimated genetic merit for carcass weight. A total of 170 male progeny from spring-calving cows and 42 sires (10 AA, 13 BB, 7 FR and 12 HO) were artificially reared indoors and managed together until the end of their second grazing season when they were assigned to either a Light (560 kg) or Heavy (620 kg) slaughter weight. Blood metabolite concentrations were measured six times throughout life and feed intake was recorded during the first and second winter. Carcass measurements and selected non-carcass components were recorded after slaughter and the right side of each carcass was dissected into lean, fat and bone. Differences in blood metabolite concentrations amongst genetic groups were negligible although there were some effects of the prevailing level of nutrition. M. longissimus area scaled for carcass weight was 0.220, 0.221, 0.260, 0.255, 0.212 and 0.208 (SE 0.004) cm²/kg for AAH, AAL, BBH, BBL, FR and HO, respectively. Carcass measurements scaled for carcass weight were greater for L, AA, HO and the dairy strains than for H, BB, FR and the beef breeds, respectively. There was no effect of estimated genetic merit for carcass weight on carcass composition. Statistically significant interactions between genetic merit and beef breed existed for some traits with the genetic merit effect largely evident for AA only. BB and the beef breeds had more lean, less fat and more high value lean in the carcass than AA and the dairy strains, respectively. It is concluded that genetic group had little effect on blood metabolite concentrations but there were some feeding level effects. Estimated genetic merit for carcass weight affected carcass weight, m. longissimus area and carcass measurements scaled for carcass weight but the effects were confined to AA. There were large effects of beef breed and dairy strain on carcass composition.     

Effects of inclusion of whole-crop pea silages differing in their tannin content on the performance of dairy cows fed high or low protein concentrates

The effect of including high or low tannin forage peas as an alternative to soyabean meal on performance and N efficiency was investigated using 18 dairy cows in two Latin square design studies. Two varieties of forage pea; Racer (coloured flowers; high tannin) and Croma (white flowers; low tannin), were ensiled 12 weeks post sowing. The in situ degradability characteristics of the pea silages were determined using 4 cannulated sheep. The low tannin forage had a higher soluble N (a) fraction and a greater extent of degradation (a + b), resulting in a greater amount of N being predicted to be released in the rumen than the high tannin forage. In experiment 1, cows were fed one of three treatments in each of 3 periods of 28 d duration in a Latin square design; grass silage/whole-crop wheat (0.50:0.50, DM basis) and 8 kg/d of a high protein concentrate (GWH); grass silage/whole-crop wheat/high tannin forage pea silage (0.25:0.25:0.50 respectively, DM basis) and 8 kg/d of a high protein concentrate (HTH) or 8 kg/d of a low protein supplement (HTL). The inclusion of forage peas increased (P < 0.05) DM intake by 1.2 kg DM/d, but there was no effect of dietary treatment on milk yield (average of 23.0 kg/d), composition or live weight change. The efficiency of use of dietary N (N output in milk/N intake) was highest (P < 0.001) in cows when fed GWH (0.289) and lowest in HTH (0.234). In experiment 2, cows were fed one of three treatments in each of 3 periods of 28 d duration in a Latin square design; grass silage/whole-crop wheat (0.50:0.50, DM basis) and 8 kg/d of a high protein concentrate (GWH); grass silage/whole-crop wheat/low tannin forage pea silage (0.25:0.25:0.5 respectively, DM basis) and 8 kg/d of a high protein concentrate (LTH) or 8 kg/d of a low protein concentrate (LTL). Compared with GWH, the inclusion of forage peas increased (P < 0.05) DM intake by 2.0 kg/d, but there was no effect of dietary treatment on milk yield (average of 24.5 kg/d). Milk fat content was highest (P < 0.05) in cows when fed LTL (45.7 g/kg) and lowest in LTH (41.9 g/kg), but there was no effect (P > 0.05) of treatment on daily fat yield or any other milk component. The efficiency of dietary N use was highest (P < 0.001) in cows when fed GWH (0.300) and lowest in LTH (0.234). It is concluded that either high or low tannin forage pea silages can replace approximately 1.1 kg/d of soyabean meal in the diet of mid-late lactation dairy cows without affecting animal performance, but N efficiency for milk production is decreased.     

玉米秸秆营养价值的开发利用——未充分开发利用的廉价资源

我国有着极其丰富的秸秆资源,每年仅玉米秸秆产量就达2.65亿t左右,但利用率非常低,大部分被直接还田或者焚烧,在造成巨大的资源浪费的同时还引起了特别严重的空气污染问题,直接威胁到人们的健康。长期以来,我国规模化奶牛场在粗饲料种类的选择上存在严重的误区,认为只有采用像苜蓿这样的进口优质粗饲料才能获得理想的生产性能和最佳的经济效益,忽视了对玉米秸秆资源的开发利用。实际上只要妥善解决玉米秸秆机械化收割等一系列产中及产后问题,并通过化学、物理或微生物方法对玉米秸秆进行加工处理,这部分廉价资源就可以成为后备牛、干奶牛及泌乳中后期奶牛良好的粗饲料来源。本文在总结大量相关研究成果的基础上,阐述了合理利用玉米秸秆资源的重要意义,综述了影响玉米秸秆饲用价值的因素及提高其饲用价值的处理方法,并针对各种处理方法的利弊展开分析。     

裹包TMR饲喂对泌乳中期奶牛生产性能、养分表观消化率及血液生化指标的影响

为了研究裹包全混合日粮(TMR)饲喂方式对泌乳奶牛生产性能、养分表观消化率和血液指标的影响,本试验选择24头泌乳天数为(124±20)d的荷斯坦奶牛,随机分为2个处理组,进行为期10周的饲养试验。对照组采用传统的精粗分开饲喂方式,试验组采用裹包TMR饲喂方式,精粗分开饲喂组和裹包TMR饲喂组的日粮配方组成和比例均相同,日粮精料比例为50∶50,裹包TMR水分含量调整为50%。结果表明,1)饲喂裹包TMR,可以显著增加干物质采食量(P<0.05),提高产奶量7.69%并提高3.5%标准乳产量5.20%(P>0.05);2)裹包TMR饲喂方式与精粗分开饲喂方式对乳成分含量和产量的影响差异不显著;3)裹包TMR饲喂可以显著提高粗蛋白和粗脂肪的表观消化率(P<0.05),干物质消化率有提高的趋势(P<0.1);4)裹包TMR饲喂显著降低了血清中尿素氮的含量(P<0.05),但对其他血液指标影响2组间差异不显著。裹包TMR技术可以作为一种有效的全混合日粮供给方式,可在我国中小规模奶牛养殖场和个体养殖户中推荐使用,以期提高奶牛生产性能和综合收益。