Effects of dietary energy intake during gestation and lactation on milk yield and composition of first,second and fourth parity sows

Abstract

In order to determine the effects of a varied level of dietary energy intake during pregnancy and lactation on milk yield and composition, first, second and fourth parity sows (Large White × German Landrace) were provided with energy at a level of either: (i) 100% of ME requirement (MEreq) during pregnancy and lactation, (ii) 120% MEreq during pregnancy and 80% during lactation, and (iii) 80% MEreq during pregnancy and 120% during lactation. In spite of equal target levels feed analysis revealed that gestating first parity sows with 120/80 treatment combination and lactating sows of 80/120 treatment combination received 25, and 11 – 17% more digestible N than in the respective 100/100 treatment combination. Irrespective of this 120/80 sows responded with the highest milk DM, fat, and energy contents, and the lowest lactose concentrations whereas protein levels where not affected, irrespective of parity (p < 0.05). Milk yield of sows in 1st and 4th lactation was 85 and 106% of that in 2nd lactation, respectively. Average milk composition was 18.1% DM, 4.9% protein, 6.8% fat, 5.6% lactose, and 0.8% ash. Milk composition changes ceased at day 7 of lactation with a reduction of milk GE and protein, and an increase of lactose content. Concentrations of threonine, arginine, valine, leucine, tyrosine, phenylalanine, cystine, and tryptophan, as well as stearic, oleic, and linoleic acid were higher in colostrum than in milk at later lactation stages. In contrast, laurine, myristic, palmitic, and palmitoleic acids were lower concentrated in colostrum. In conclusion, these results illustrate the importance of body reserve mobilization for milk production in sows and indicate that low energy supply during gestation cannot be compensated by higher energy supply during lactation.     

Variation in blood leucocytes,somatic cell count,yield and composition of milk of crossbred goats

Ten multiparous crossbred goats, five each of alpine × beetal (AB) and saanen × beetal (SB) were selected from the National Dairy Research Institute goat herd immediately after parturition. These were managed as per the practices followed in the institute’s goatherd. Blood and milk samples were collected at biweekly intervals from day 14 post-kidding for 22 weeks (154 days). Somatic cell count, electrical conductivity, fat, protein and lactose contents of milk were determined using standard methods. In the blood samples total leucocytes and differential leucocytes were also determined. Somatic cell counts were high immediately after parturition on day 14 of lactation and declined gradually with advanced lactation. There were individual variations (P < 0.01) in somatic cell counts between different lactation periods. Somatic cell count of milk was negatively correlated with neutrophils only (P < 0.05) and was neither correlated with milk yield, or with fat, protein, lactose content of milk. Electrical conductivity of milk was low up to four weeks of lactation and thereafter increased as the lactation advanced. Lactose content of milk declined gradually with the advancement of lactation. Fat content of milk was stable up to the eighth week and thereafter increased with advancement of lactation while the protein content of milk did not change significantly during lactation.     

慢病毒shRNA表达载体介导人肿瘤细胞基因稳定沉默的影响因素

目的 探讨慢病毒载体介导人肿瘤细胞RNA干扰的影响因素。方法 以乏氧诱导因子-1α（Hypoxia-inducible factor-1α, HIF-1α）和乏氧诱导因子-1β（Hypoxia-inducible factor-1β, HIF-1β）基因为靶基因,采用Invitrogen公司的BLOCK-iT Lentiviral RNAi Expression System生产表达靶基因shRNA的慢病毒载体,转导Hela、SPCA1和A549,采用定量RT-PCR技术检测靶基因mRNA表达水平。结果 用此系统生产慢病毒,每一10cm培养皿可收获6.3×1010个病毒颗粒。浓度为2×1010copies/ml的Lenti6-HIF1α和Lenti6-HIF1β转导SPCA1、A549和Hela细胞的功能滴度分别为：1.8×106TU/ml、1.2×106TU/ml、1.75×106TU/ml和1.76×106TU/ml、1.21×106TU/ml和1.79×106TU/ml。延长病毒的吸附时间可以提高转导效率, 8小时以内转导效率与吸附时间呈正比,12小时开始进入平台期。1/4、1/2、1、2、4、8倍MOI的Lenti6-HIF1α病毒转导SPCA1和Hela细胞48小时后,RNAi效果与病毒量呈正相比。用筛选的转导细胞证实,RNAi长期效果与细胞类型无关,但与shRNA表达结构整合到靶细胞基因组的拷贝数呈正相关。结论 慢病毒载体介导人肿瘤细胞RNA干扰,短期基因抑制效果取决于细胞类型、病毒量和病毒的吸附时间,稳定基因沉默效果与病毒整合到靶细胞基因组的拷贝数密切相关。     

Histological and histochemical study on mammary gland of Damascus goats through stages of lactation

This research was carried out on seven Damascus goats, to study the relationship between milk production, during advancing lactation, and the changes in secretory mammary cells frequency and cellular activity. Biopsies were obtained from the mammary gland at the three stages of lactation, early, mid and late, for histological and histochemical studies. The histological structures of the mammary gland showed clear differences between lactation stages—being more developed in the early and the mid stages, compared to the late stage of lactation. The number of the alveolar secretory cells increased from the early to the mid stage of lactation by 12.9% and then was reduced at the late stage by 35.9% from that at the mid stage. The milk yield increased by 51.3% from the early to the mid stage, and then was reduced at the late stage by 71.4% from that of the mid stage. The total sectional areas of plate equal to 1.22 mm²/plate of the alveoli were the smallest during late lactation (0.36 mm²/plate) compared to that during the early and the mid stage of lactation (0.50 and 1.17 mm²/plate, respectively). Numerous loci of alkaline phosphatase enzyme (AP) were apparent on the outer surface of the alveolar secretory cells at the early and the mid stages of lactation—suggesting that this enzyme plays an important physiological role in the apical membrane of the alveolar epithelial cells during lactation. Dense protein staining of these cells as well as increased frequency of DNA expression denote great development and increased numbers of these cells at early and mid stages of lactation. This was accompanied by a high level of milk secretion reaching 939.3 ± 130 and 1421.4 ± 123.4 ml/head/day, respectively. In contrast, at the late stage of lactation, the size of alveoli was reduced and few alveoli showed weak AP activity, weak protein manifestation and the lowest frequency of DNA loci. This coincided with the reduction in milk yield (407 ml/head/day). It could be concluded that the stages of the lactation influence the cell number and activity of the mammary parenchyma.     

Effects of bovine mammary gland biopsy and increased milking frequency on post-procedure udder health,histology, and milk yield

Sixteen cows in early lactation were randomly distributed into two groups in order to evaluate the effects of mammary biopsies and increased milking frequency on tissue characteristics, post-biopsy udder health and histology. One group was milked twice a day (2×) starting on the 2nd day after calving, until 28 days in milk (DIM). The other group was milked four times a day (4×) from two to 21 DIM, and twice a day (2×) from 22 to 28 DIM. On days 2, 7, 14, 21, and 28 postpartum, one fragment of secretory tissue was collected from one mammary quarter at a time. Collections were alternated between the four mammary quarters per collection day. A total of 80 mammary tissue samples were collected. Qualitative and quantitative analyses of the tissues were conducted by histologic examination. Animal health was assessed by observation of feed intake behavior immediately after biopsy, and weight and body condition score before and one week after biopsy. Udder health was assessed daily from calving to 60 DIM with California Mastitis Test (CMT) and by noting alterations in the milk such as blood, milk clots, blood clots, clinical signs of mastitis. Milk composition and somatic cell count (SCC) were analyzed before and after the biopsies. Milk production was evaluated before biopsy, on the day of biopsy, and after the biopsy. An average of 10 fields at 40× magnification was obtained from each sample. There were no evident changes in mammary morphology as a result of milking two or four times/day at any of the evaluated time points. Biopsy wounds healed rapidly without infection. Intramammary bleeding and CMT alterations were observed in 96% and 75% of the biopsied mammary quarters, respectively. Clinical mastitis was diagnosed in 12% of the biopsied quarters. Different milking frequencies had no effect on the frequency and duration of post-biopsy alterations. Milk production decreased after biopsies done on days 2 for 2× and 4× groups, but it returned to pre-biopsy values within 1 day. Milk composition and SCC were affected transiently. Increased milking frequency did not influence udder health. Post-biopsy recovery was rapid and the procedure proved effective without damaging the cows’ health.     

Effects of intravenous arginine infusion on inflammation and metabolic indices of dairy cows in early lactation

Enhancing the supply of arginine (Arg), a semi-essential amino acid, has positive effects on immune function in dairy cattle experiencing metabolic stress during early lactation. Our objective was to determine the effects of Arg supplementation on biomarkers of liver damage and inflammation in cows during early lactation. Six Chinese Holstein lactating cows with similar BW (508 ± 14 kg), body condition score (3.0), parity (4.0 ± 0), milk yield (30.6 ± 1.8 kg) and days in milk (20 ± days) were randomly assigned to three treatments in a replicated 3 × 3 Latin square design balanced for carryover effects. Each period was 21 days with 7 days for infusion and 14 days for washout. Treatments were (1) Control: saline; (2) Arg group: saline + 0.216 mol/day l-Arg; and (3) Alanine (Ala) group: saline + 0.868 mol/day l-Ala (iso-nitrogenous to the Arg group). Blood and milk samples from the experimental cows were collected on the last day of each infusion period and analyzed for indices of liver damage and inflammation, and the count and composition of somatic cells in milk. Compared with the Control, the infusion of Arg led to greater concentrations of total protein, immunoglobulin M and high density lipoprotein cholesterol coupled with lower concentrations of haptoglobin and tumor necrosis factor-α, and activity of aspartate aminotransferase in serum. Infusion of Ala had no effect on those biomarkers compared with the Control. Although milk somatic cell count was not affected, the concentration of granulocytes was lower in response to Arg infusion compared with the Control or Ala group. Overall, the biomarker analyses indicated that the supplementation of Arg via the jugular vein during early lactation alleviated inflammation and metabolic stress.     

Effects of Bacillus subtilis natto on milk production,rumen fermentation and ruminal microbiome of dairy cows

Two experiments were conducted to evaluate the effects of Bacillus subtilis natto, which was initially isolated from fermented soybeans on milk production, rumen fermentation and ruminal microbiome in dairy cows. In Experiment 1, 36 early lactation Chinese Holstein dairy cows (56 ± 23 days in milk) were randomly assigned to three groups: Control, cows were fed total mixed ration (TMR); BSNLOW, TMR plus 0.5 × 10¹¹ colony-forming units (cfu) of B. subtilis natto/cow per day; and BSNHIGH, TMR plus 1.0 × 10¹¹ cfu of B. subtilis natto/cow per day. During the 70-day treatment period, daily milk production and daily milk composition were determined in individual cows. The results showed that supplementing dairy cows with 0.5 × 10¹¹ and 1.0 × 10¹¹ cfu of B. subtilis natto linearly increased (P < 0.01) milk production (25.2 and 26.4 kg/day v. 23.0 kg/day), 4% fat-corrected milk (27.3 and 28.1 kg/day v. 24.2 kg/day), energy-corrected milk (27.3 and 28.2 kg/day v. 24.2 kg/day), as well as milk fat (1.01 and 1.03 kg/day v. 0.88 kg/day), protein (0.77 and 0.82 kg/day v. 0.69 kg/day) and lactose yield (1.16 and 1.22 kg/day v. 1.06 kg/day) but decreased milk somatic cell counts (SCC) by 3.4% to 5.5% (P < 0.01) in BSNLOW and BSNHIGH treatments compared with Control. In Experiment 2, four rumen-cannulated dairy cows were fed the basal diet from 1 to 7 days (pre-trial period) and rumen samples were collected on days 6 and 7; the same cows then were fed 1.0 × 10¹¹ cfu/day B. subtilis natto from days 8 to 21 (trial period) and rumen samples were collected on days 20 and 21. B. subtilis natto was discontinued from days 22 to 28 (post-trial period) and rumen samples were collected on days 27 and 28. Compared with the pre- and post-periods, ruminal pH decreased by 2.7% to 3.0% during the trial period (P < 0.01), whereas ammonia nitrogen (NH₃-N), total volatile fatty acids and molar proportion of propionate (P < 0.01) and valerate (P < 0.05) increased. Molar proportion of acetate decreased and the acetate to propionate ratio was lower (P < 0.01) during the trial period. However, no differences for 24-h in sacco dry matter digestibility were detected among different periods (treatments) though NDF digestibility was reduced in the trial and post-trial periods (P < 0.01). Compared with pre-trial period, total ruminal bacteria, proteolytic and amylolytic bacteria in rumen enumerated by culture methods increased by 15.0%, 16.2% and 11.7%, respectively (P < 0.01) but protozoa decreased to 5.35 log₁₀ cfu/ml (P < 0.01) during the trial period. These results demonstrate that B. subtilis natto improves milk production and milk components yield, decreases SCC and promotes the growth of total ruminal bacteria, proteolytic and amylolytic bacteria, which indicate that B. subtilis natto has potential to be applied as a probiotic for dairy cows.     

Growth characterizations of a human monocytic leukemia cell line in a serum-free medium

A clone, AH-01S, derived from a human monocytic leukemia cell line, THP-1, grew rapidly in a serum-free medium containing insulin, transferrin, ethanolamine, and sodium selenite. In batch culture using the serum-free medium, the AH-01S cells proliferated at a specific growth rate (μ) of 0.30 to 0.50 (1/day) from a cell concentration of 1 × 10⁴ cells/ml to 1.6 × 10⁶ cells/ml, an increase of 160 times. A higher cell concentration of 0.45 × 10⁷ cells/ml (cell volume ratio was 0.5%) was obtained in spinner flask culture using the serum-free medium. A mean specific growth rate 0.50 (1/day) was also observed in a culture in a fully instrumented cell culture fermentor. However, μ decreased drastically after the cell concentration reached 1.5 × 10⁶ cells/ml. Analyses of medium composition during cultivation revealed that under lower cell concentration, l-glutamine was the main carbon source while glucose was converted to lactate almost stoichiometrically, and that the production of lactate from glucose decreased at higher cell concentrations. To obtain cultures of 1 × 10⁹ cells, 1,200 to 1,300 mg of a carbon source (glucose) and 400 to 500 of amino acids were consumed during high cell concentration cultivation of the AH-01S cells in the serum-free medium.     

Short- and long-term effects of high milking frequency during the first 21 days of lactation on production and reproductive performance in high-lactating cows

We examined short- and long-term effects of high milking frequency (HMF) for the first 21 days of lactation. The study included 122 Israeli Holstein cows – 32 pregnant heifers, 40 cows in second lactation and 50 cows in >second lactation. Heifers were paired according to predicted transmitting ability and cows according to energy-corrected milk (ECM) production, age, days in milk and expected calving date. Thin cows (body condition score <2.75) were not included. One cow from each pair was arbitrarily allocated to a control group milked three times daily (3× milking cows) and the counterpart to an experimental group milked six times daily for the first 21 days of lactation and then three times daily for the rest of the lactation (6× milking cows). During the first 21 days of lactation, 6× milking cows produced 9.3 kg more milk (26.5%) and 7.16 kg more ECM (19%) than the 3× milking cows. The higher milk production persisted throughout the entire lactation (305 days), as reflected by treatment×age interaction showing higher milk production for the first and second (7%) but not >second lactation cows relative to their control counterparts (−0.37%); ECM production was also higher in 6× milking first and second lactation (7.6% and 5%, respectively) but not for >second lactation cows. Furthermore, HMF had long-lasting effects, expressed as significantly higher milk production through the succeeding lactation in the previous first lactation cows (10%); a tendency toward significance in the second lactation cows relative to the controls (4.7%), but a deleterious effect on the >second lactation cows, reflected by lower milk production (−5.25%) than in controls; similar patterns were found for the ECM. For the entire 305 days of lactation, fat and protein yields were higher for first and second lactation cows, whereas protein yield for >second lactation cows was lower in the 6× milking v. control group. Given that HMF during the first 21 days of first or second lactation increases milk and ECM yields throughout the concurrent and successive lactation with no adverse effect on energy balance, mastitis, metabolic diseases or reproduction, it seems to be economically beneficial. However, caution should be paid for >second lactation cows due to absence of significant effect in the entire of the first HMF applied lactation and the deleterious effect in the succeeding lactation.     

Effect of oral polyamine supplementation pre-weaning on piglet growth and intestinal characteristics

A high proportion of piglets fail to adapt to the changing composition of their diet at weaning, resulting in weight loss and increased susceptibility to pathogens. Polyamines are present in sow milk and promote neonatal maturation of the gut. We hypothesised that oral spermine and spermidine supplementation before weaning would increase piglet growth and promote gastrointestinal development at weaning. In Experiment One, one pair of liveweight (LW)-matched piglets per litter from first and third lactation sows received 2 ml of a 0 (Control) or 463 nmol/ml spermine solution at 14, 16, 18, 20 and 22 days of age (n=6 piglets/treatment per parity). Villus height and crypt depth in the duodenum and jejunum were measured at weaning (day 23 postpartum). In Experiment Two, piglets suckling 18 first and 18 third lactation sows were used. Within each litter, piglets received 2 ml of either water (Control), 463 nmol/ml spermine solution or 2013 nmol/ml spermidine solution at 14, 16, 18, 22 and 24 days of age (n=54 piglets/treatment per sow parity). Piglets were weighed individually at 14, 18, 24 (weaning) and 61 days of age. In Experiment One, oral spermine supplementation resulted in a 41% increase in villus height, a 21% decrease in crypt depth and 79% decrease in the villus height : crypt depth ratio compared with control piglets (P<0.01). In Experiment Two, spermine and spermidine-supplemented piglets suckling first lactation sows grew faster (P<0.05) between days 14 and 18 postpartum than control piglets: 0.230±0.011 and 0.227±0.012 v. 0.183±0.012 kg/day, respectively. Spermine supplementation tended (P<0.1) to increase piglet LW gain from weaning to day 37 post-weaning compared with control piglets (0.373±0.009 v. 0.341±0.010 kg/day). In conclusion, spermine supplementation increased villus height at weaning, and appears to have the potential to improve the pre- and post-weaning growth of conventionally weaned piglets.     

Pb2+浓度和藻类食物密度对多刺裸腹溞生命表统计学参数的影响

采用48h急性毒性试验研究了Pb2+对多刺裸腹溞(Moina macrocopa)的48h-LC50值,采用生命表试验方法在0.5×106、1.0×106、2.0×106个细胞/mL的斜生栅藻(Scenedesmus obliquus)密度下研究了浓度为0.2、0.4、0.6、0.8、1.0mg/L的Pb2+对多刺裸腹溞生命表统计学参数的影响。结果表明,Pb2+对多刺裸腹溞48h-LC50值为10.5mg/L。与各食物密度下的对照组相比,除了0.5×106、1.0×106个细胞/mL下0.2mg/L的Pb2+显著延长了多刺裸腹溞的生命期望,0.5×106个细胞/mL的食物密度下0.4mg/L的Pb2+显著提高了多刺裸腹溞的净生殖率、0.40.8mg/L的Pb2+显著提高了种群内禀增长率外,较高浓度的Pb2+显著缩短了多刺裸腹溞的生命期望,降低了净生殖率、总生殖率和种群内禀增长率;且随着食物密度的升高,使净生殖率和总生殖率显著降低的Pb2+浓度阈值呈降低的趋势,但使世代时间显著缩短的Pb2+浓度阈值则呈升高的趋势。Pb2+浓度、食物密度以及它们间的交互作用对多刺裸腹溞的各主要生命表统计学参数均有显著的影响(P0.05)。0.5×106、1.0×106cells/mL食物密度下,Pb2+浓度与多刺裸腹溞的各主要生命表统计学参数间均有显著的剂量-效应关系;2.0×106cells/mL食物密度下,Pb2+浓度与多刺裸腹溞的生命期望、总生殖率和净生殖率间均有显著的剂量-效应关系。多刺裸腹溞的生命期望、净生殖率和内禀增长率对Pb2+污染的敏感性因食物密度的不同而存在着差异。     

Higher somatic cells counted by the electronic counter method do not influence renneting properties of goat milk

Laws of different countries regarding SCC of goat milk are not in agreement with each other and sometimes they fix a threshold for the enhancement of dairy products. The aim of this study was to assess if renneting properties of goat milk are influenced by higher somatic cell count (SCC) measured by an electronic cell counter. Milk samples, taken throughout the lactation of 169 goats from three farms, were analyzed for chemical, physical, hygienic and renneting properties. Samples were divided into three levels on the basis of their SCC: L: low level, samples with SCC lower than 10⁶ cells/ml; M: medium, between 10⁶ and 2 × 10⁶ cells/ml; H: high, higher than 2 × 10⁶ cells/ml. Milk clotting time was between 12.07 and 13.31 min, curd firming time between 1.68 and 2.05 min and curd firmness between 41.66 and 48.97 mm. All the three renneting properties were not affected by the SCC level but they were highly correlated with other factors as protein content and pH. Furthermore, the microbial count showed a high positive correlation with SCC. These results showed that in goat milk, contrarily to other dairy species, higher SCC did not affect renneting properties and that counting of somatic cells by using electronic cell counters might be not suitable for the improvement of dairy products.     

Alterations in the relative abundance of Haptoglobin (Hp) transcripts in total milk somatic cells during different stages of lactation cycle in high yielding cross-bred cows

The expression profile of Haptoglobin (Hp) gene in total milk somatic cells (SCC) of high-yielding cross-bred Karan Fries (KF) was studied during early, mid, and late lactation cycle. Milk samples (200 ml/animals) were collected from 10 high-yielding and 10 low-yielding cows throughout the lactation cycle (from day 7 to day 300) with an interval of one month. Relative mRNA expression profiles of Hp by RT polymerase chain reaction was studied in high-yielding cows, whereas low-yielding cows were taken as control. The folds of induction of Hp was significantly (p < 0.001) downregulated by a mean factor of 0.207 in milk SCC during early lactating cows. Whereas, it was significantly (p < 0.01) upregulated by a mean factor of 20.888 during mid lactation. The expression was unaltered during the late lactation. The study demonstrates that Hp is synthesized within the mammary gland and significantly upregulated during mid-lactation period compared to other stages of lactation cycle.     

Genetic variations in the SPP1 promoter affect gene expression and the level of osteopontin secretion into bovine milk

Osteopontin (OPN) is now recognized as an important cytokine and extracellular integrin‐binding protein at the crossroads of inflammation and homeostasis. In a previous study, we found that OPN gene (SPP1) polymorphisms are associated with milk performance traits and somatic cell score (SCS), a parameter used to estimate the genetic value of udder health in dairy cattle. In this study, we assessed whether the genetic variations had an impact on SPP1 promoter activity, immune response and the level of OPN secreted into milk. The influence of DNA polymorphisms on the promoter activity of SPP1 was confirmed in vitro. To measure the impact of the genetic variations on OPN secretion into milk, we measured OPN levels in both plasma and milk throughout lactation. Cows were grouped by the OPN haplotypes associated with a high (H2 × H3) or low (H1 × H4) SCS. For both H2 × H3 and H1 × H4, the OPN level in plasma remained low throughout lactation, although the concentration in the milk of H1 × H4 cows increased more in late lactation. Moreover, the macrophages of H1 × H4 cows expressed a lower SPP1 and proinflammatory IL6 in response to infection. Regarding the immune cell response, cows with the genetic potential to secrete higher OPN levels during late lactation had macrophages expressing fewer proinflammatory cytokines, a situation that might explain the genetic association with low somatic cells. Although OPN's favorable roles during late lactation remain to be elucidated, the tissue remodeling properties associated with OPN may be beneficial for reducing the incidence of infection during the transition period in lactating cows.     

Fertilization of cumulus-free,zona-intact mouse ova in vitro at high and low sperm concentrations

The effect of varying the sperm concentration between 2 × 10⁵ sperm/ml and 8 × 10⁶ sperm/ml on fertilization of cumulus-free, zona-intact F1 (CBA × C57BL) mouse ova by QS and F1 (CBA × C57BL) mouse spermatozoa was studied. The spermatozoa from both strains of mice exhibited optimal fertilization rates at 2 × 106 sperm/ml. However, at sperm concentrations greater than 4 × 106 sperm/ml and less than 1 × 106 sperm/ml, fertilization rates were significantly reduced. F1 spermatozoa were more susceptible to dilution than QS spermatozoa. A significant interaction between strain and sperm concentration indicated that the two strains produced different fertilization rates at different sperm densities. Extracts of epididymal fluid, medium from capacitated spermatozoa, or ampulla fluid did not improve the fertilization rate at 2 × 105 sperm/ml, but retaining the cumulus oophorus did. The decrease in fertilization rate at 8 × 106 sperm/ml can in part be attributed to a nondialysable inhibitor from the neat sperm preparation that appeared to be of epididymal origin.     

Restricting dairy cow access time to pasture in autumn: The effects on milk production,grazing behaviour and DM intake of late lactation dairy cows

Extending the grazing season in pasture based systems of dairy production can increase farm profitability; poor weather and soil conditions can reduce the number of grazing days. The study objectives were to (i) examine the effect of restricted access to pasture in the autumn on the milk production, grazing behaviour and DM intake (DMI) of late lactation spring-calving dairy cows and (ii) establish the effect of alternating restricted and continuous access to pasture on dairy cow production, DMI and grazing behaviour. Cows were randomly assigned to one of four grazing treatments: (i) 22 h (full-time) access to pasture (22H; control); (ii) Two 5-h periods of access to pasture (2×5H); (iii) Two 3-h periods of access to pasture (2×3H); and (iv) alternating between full-time and 3-h access to pasture with no more than three continuous days on any one regime, e.g. Monday – full-time access, Tuesday − 2x3H access, Wednesday − 2x3H access; Thursday – full-time access, etc. (2×3HV). Restricted access to pasture was offered after a.m. and p.m. milking. Swards of similar quality and pregrazing herbage mass were offered. Treatment had no effect on milk yield (13.2 kg/day), milk fat (48.2 g/kg), protein (39.0 g/kg) or lactose content (42.6 g/kg) and milk solid yield (1.15 kg/day). Similarly, there was no effect of treatment on final BW (483 kg) or final BCS (2.66). There was no significant difference in DMI (15.1 kg DM/cow/day) between treatments. There was an effect on daily grazing time, 22H cows (565 min/cow/day) grazed for longest time, however, when the 2x3HV treatment had full-time access to pasture, they had a similar grazing time (543 min/cow/day) to the 22H cows and were similar to the 2x3H treatment on days with restricted access to pasture (357 min/cow/day). The 22H and 2x5H animals had similar grass DMI/min (29.2 g/min), the 2x3HV were higher (33.9 g/min) but were similar to the comparable treatment when offered 2x3H access time (41.6 g/min) and when offered 22H access time (27.7 g/min). The results from this study show how when offered a grass only diet of autumn pasture grazing behaviour can be modified by restricting pasture access time without reducing dairy cow production in late lactation at low production levels. There was also no effect of alternating access time between 22H and 2x3H on milk production and DMI in the 2x3HV treatment. Restricted access time to pasture in autumn may be a strategy which farmers can use to extend the grazing season.     

Variations During Lactation in Total and Differential Leukocyte Counts,N-acetyl-ß-D-glucosaminidase,Antitrypsin and Serum Albumin in Foremilk and Residual Milk from Non-infected Quarters in the Bovine

Quarter samples of foremilk and residual milk were taken approximately every second week from 2 days post partum (pp) throughout lactation month 9, from 5 dairy cows in their second lactation period. Bacteriologically positive milk samples were excluded. The aim was to study the variation in total and differential leukocyte counts, N-acetyl-ß-D-glucosaminidase (NAGase), antitrypsin (ATR) and serum albumin (BSA) in milk during the lactation period and different stages of oestrous cycle. Also the between milkings variation was studied from lactation month 4 to 9. At 2 days pp, each fraction of milk contained significantly higher numbers of leukocytes and had a higher activity of NAGase and ATR than later in the lactation period. In foremilk the highest content of BSA was also recorded at 2 days pp. From lactation month 2 to 9, stage of lactation had, in general, a slight effect on the variation in the variables measured. The total leukocyte count in residual milk tended to increase as lactation proceeded. The proportion of monocyte-macrophages in foremilk was significantly decreased during the last 4 months. NAGase and BSA in both fractions and ATR in residual milk increased significantly towards the end of the lactation period. From lactation month 4 to 9 the highest recorded ranges of variation between milkings, within quarter and stage of lactation, in the total leukocyte count, proportions of neutrophils, lymphocytes, monocyte-macrophages, NAGase, ATR and BSA in foremilk were 215 × 103ml, 42 %, 34 %, 54 %, 6.68 units, 0.36 units and 0.14 mg/ml respectively. The corresponding figures in residual milk were higher except for the variation in BSA which was slightly lower in residual milk than in foremilk. In residual milk there was a positive correlation between the proportion of neutrophils and the total leukocyte count, when calculated on data from all cows and the entire experimental period. During the oestrous periods, the proportion of neutrophils in residual milk was higher than during the dioestrous periods. Foremilk and residual milk differed in the total as well as the differential leukocyte counts in all the various stages of lactation, whereas the contents of NAGase, ATR and BSA were equal in both fractions. The exception was 2 days pp when the proportions of lymphocytes were equal in both fractions and BSA-significantly higher in foremilk than in residual milk.     

Protein profile and alpha-lactalbumin concentration in the milk of standard and transgenic goats expressing recombinant human butyrylcholinesterase

The expression of recombinant proteins of pharmaceutical interest in the milk of transgenic farm animals can result in phenotypes exhibiting compromised lactation performance, as a result of the extraordinary demand placed on the mammary gland. In this study, we investigated differences in the protein composition of milk from control and transgenic goats expressing recombinant human butyrylcholinesterase. In Experiment 1, the milk was characterized by gel electrophoresis and liquid chromatography/mass spectrometry in order to identify protein bands that were uniquely visible in the transgenic milk and/or at differing band densities compared with controls. Differences in protein content were additionally evaluated by computer assisted band densitometry. Proteins identified in the transgenic milk only included serum proteins (i.e. complement component 3b, ceruloplasmin), a cytoskeleton protein (i.e. actin) and a stress-induced protein (94 kDA glucose-regulated protein). Proteins exhibiting evident differences in band density between the transgenic and control groups included immunoglobulins, serum albumin, β-lactoglobulin and α-lactalbumin. These results were found to be indicative of compromised epithelial tight junctions, premature mammary cell death, and protein synthesis stress resulting from transgene expression. In Experiment 2, the concentration of α-lactalbumin was determined using the IDRing^® assay and was found to be significantly reduced on day 1 of lactation in transgenic goats (4.33 ± 0.97 vs. 2.24 ± 0.25 mg/ml, P < 0.01), but was not different from non-transgenic controls by day 30 (0.99 ± 0.46 vs. 0.90 ± 0.11 mg/ml, P > 0.05). We concluded that a decreased/delayed expression of the α-lactalbumin gene may be the cause for the delayed start of milk production observed in this herd of transgenic goats.     

Relation of Milk Production Loss to Milk Somatic Cell Count

Milk production loss was studied in relation to increased somatic cell count (SCC). Available data were weekly test-day milk yields and SCC (in 1,000 cells/ml), and mastitis incidences. In total, 18,131 records from 274 cows were used. Production loss was determined for test-day kg milk, kg protein, and kg energy-corrected milk. Least-squares analysis of variance was used to estimate the direct effect of Log10(SCC) on production. The recorded measures of production were first corrected for fixed effects, with adjustment factors estimated from a healthy data-set. The average daily milk yield was 19.7 kg/day in first lactation and 22.0 in later lactations. The geometric mean of SCC was 63.1 in first lactation and 107.2 in later lactations. The incidence of clinical mastitis treated by a veterinarian was 19.8% of the lactations-at-risk. Linear relationships were found between the production parameters and Log10(SCC). Quadratic and cubic effects were evaluated, but were found to contribute little to the overall fit of the models. The individual milk yield loss was 1.29 kg/day for each unit increase in Log10(SCC) for cows in first lactation. Milk yield decreased by 2.04 kg/day per unit Log10(SCC) for older cows. Corresponding values for protein yield were 0.042 and 0.067 kg/day for first and later lactations, respectively.     

Effects of dietary energy intake during gestation and lactation on milk yield and composition of first, second and fourth parity sows

In order to determine the effects of a varied level of dietary energy intake during pregnancy and lactation on milk yield and composition, first, second and fourth parity sows (Large White x German Landrace) were provided with energy at a level of either: (i) 100% of ME requirement (MEreq) during pregnancy and lactation, (ii) 120% MEreq during pregnancy and 80% during lactation, and (iii) 80% MEreq during pregnancy and 120% during lactation. In spite of equal target levels feed analysis revealed that gestating first parity sows with 120/80 treatment combination and lactating sows of 80/120 treatment combination received 25, and 11-17% more digestible N than in the respective 100/100 treatment combination. Irrespective of this 120/80 sows responded with the highest milk DM, fat, and energy contents, and the lowest lactose concentrations whereas protein levels where not affected, irrespective of parity (p < 0.05). Milk yield of sows in 1st and 4th lactation was 85 and 106% of that in 2nd lactation, respectively. Average milk composition was 18.1% DM, 4.9% protein, 6.8% fat, 5.6% lactose, and 0.8% ash. Milk composition changes ceased at day 7 of lactation with a reduction of milk GE and protein, and an increase of lactose content. Concentrations of threonine, arginine, valine, leucine, tyrosine, phenylalanine, cystine, and tryptophan, as well as stearic, oleic, and linoleic acid were higher in colostrum than in milk at later lactation stages. In contrast, laurine, myristic, palmitic, and palmitoleic acids were lower concentrated in colostrum. In conclusion, these results illustrate the importance of body reserve mobilization for milk production in sows and indicate that low energy supply during gestation cannot be compensated by higher energy supply during lactation.