猪乳中一组高分子量蛋白质的表达量与母猪泌乳性能关系的研究

通过设计的数学模型,分析了162头二花脸母猪和50头大约克母猪乳中一组高分子量蛋白质(HMWP)的基因表达量(HMWP浓度)与母猪泌乳性能的关系。结果表明,初乳和常乳中HMWP的基因表达量与乳中蛋白质和表皮生长因子(EGF)含量存在显著相关(P<0.05或P<0.01),其中常乳中HMWP的基因表达量与乳蛋白存在极显著正向线性相关(P<0.01)。常乳中HMWP基因表达量与乳糖含量也有正向线性相关的趋势(P<0.1),但与类胰岛素样生长因子-1(IGF-I)和胰岛素含量无显著相关性(P>0.1)。     

Post-grazing sward height imposed during the first 10 weeks of lactation: Influence on early and total lactation dairy cow production,and spring and annual sward characteristics

Increasing the proportion of grazed grass in the diet of the dairy cow is the main target of grass-based milk production systems. Imposing a severe post-grazing sward height (PGSH) in early lactation is one strategy to increase grass utilisation. A grazing experiment was undertaken to investigate the direct and carryover effects of PGSH imposed in early lactation on sward and dairy cow lactation performance. Ninety Holstein–Friesian dairy cows (mean calving date: February 13) were randomly assigned to one of three target PGSH treatments: 2.7 cm (severe; S), 3.5 cm (low; L) and 4.2 cm (moderate; M) from February 14 to April 24, 2011 (period 1; P1). This was followed by a carryover period (period 2; P2) during which cows were randomly re-assigned within their P1 treatment across two PGSH treatments: 3.5 or 4.5 cm until November 13. Sward utilisation (>2.7 cm) during P1 was significantly improved by decreasing PGSH from M (0.74) to L (0.82) and further to S (0.94). At the end of the entire grazing season, the M treatment swards had produced +1.4 t dry matter (DM)/ha than the S and L treatment swards which had similar total DM yields (14.1 t DM/ha). Treatment had no immediate or carryover effect on the proportions of leaf, stem and senescent material in the sward or the quality of herbage selected by the animals. During P1 the cows in S had greater bodyweight loss (−18 kg), reduced milk (−2.1 kg/day) and milk solids yields (−0.21 kg/day) as well as lower grass DM intake (−1.7 kg DM/day) compared with the cows in L and M, which performed similarly (−5 kg, 24.1 kg/day, 1.94 kg/day, and 13.0 kg DM/day, respectively). There was no carryover effect of early lactation PGSH on milk and milk solids yields, fat and protein concentrations during P2. This indicates that cows restricted in P1 were able to adjust production in accordance with the higher PGSH imposed during the remainder of the lactation. The S treatment had numerically lower, though not significantly lower, total lactation milk and milk solids yields, reflecting their significantly reduced yields in early lactation. It was concluded that grazing to 2.7 cm in early lactation is too restrictive for dairy cows. Cows in L and M had very similar total cumulative production performance. As a result, grazing to 3.5 cm during the first 10 weeks of lactation contributes to achieving both high milk output from pasture and high grass utilisation.     

Central somatostatin-somatostatin receptor 2 signaling mediates lactational suppression of luteinizing hormone release via the inhibition of glutamatergic interneurons during late lactation in rats

Reproductive function is suppressed during lactation owing to the suckling-induced suppression of the kisspeptin gene (Kiss1) expression in the arcuate nucleus (ARC) and subsequent suppression of luteinizing hormone (LH) release. Our previous study revealed that somatostatin (SST) neurons mediate suckling-induced suppression of LH release via SST receptor 2 (SSTR2) in ovariectomized lactating rats during early lactation. This study examined whether central SST-SSTR2 signaling mediates the inhibition of ARC Kiss1 expression and LH release in lactating rats during late lactation and whether the inhibition of glutamatergic neurons, stimulators of LH release, is involved in the suppression of LH release mediated by central SST-SSTR2 signaling in lactating rats. A central injection of the SSTR2 antagonist CYN154806 (CYN) significantly increased ARC Kiss1 expression in lactating rats on day 16 of lactation. Dual in situ hybridization revealed that few ARC Kiss1-positive cells co-expressed Sstr2, and some of the ARC Slc17a6 (a glutamatergic neuronal marker)-positive cells co-expressed Sstr2. Furthermore, almost all ARC Kiss1-positive cells co-expressed Grin1, a subunit of N-methyl-D-aspartate (NMDA) receptors. The numbers of Slc17a6/Sstr2 double-labeled and Slc17a6 single-labeled cells were significantly lower in lactating dams than in non-lactating rats whose pups had been removed after parturition. A central injection of an NMDA antagonist reversed the CYN-induced increase in LH release in lactating rats. Overall, these results suggest that central SST-SSTR2 signaling, at least partly, mediates the suppression of ARC Kiss1 expression and LH release by inhibiting ARC glutamatergic interneurons in lactating rats.     

Serological examination and egg production of progeny of fowl experimentally infected with Egg Drop Syndrome 1976 virus

Summary

Following EDS'76 virus (BC14 virus) infection of breeder chickens by the conjunctival route, vertical transmission occurred in the first week after infection. In the progeny which had been infected with EDS'76 virus by the vertical route, increasing haemagglutination inhibiting (HI) litres to BC14 virus and increasing numbers of birds with HI litres were observed from 3 weeks to 15 weeks of age. Sixty‐one per cent of the hens and 77 per cent of the cocks had ²log HI BC14 virus litres exceeding 4 at an age of 15 weeks.

Some birds which had been serologically negative throughout the rearing period, seroconverted between 25 and 28 weeks of age. This phenomenon occurred in hens as well as in cocks. Simulation of stress twice during the laying period by injection of corticosteroid hormone did not increase the number of birds serologically positive to EDS'76 virus.

EDS'76 was observed in the group of hens that was vertically infected, since egg production was significantly depressed between 28 and 34 weeks of age. Probably this was mainly the result of a production drop in the hens showing seroconversion at 27 or 28 weeks of age.

In the group of fowl vertically infected with EDS'76 virus, serologically positive birds appeared to be protected for the greater part to BC14 virus challenge at 50 weeks of age, while negative birds seemed to be fully susceptible. Chicks hatched from eggs collected in the third and fourth week after infection of the dams had maternal antibodies. Fertility and hatchability of apparently normally shelled eggs seemed not to be affected after BC14 virus infection of the dams. Intensive contact with contaminated faeces is probably an indispensable condition for lateral transmission of the virus.     

大豆皮替代产奶牛日粮精料中玉米与小麦麸对产奶性能的影响

本试验选用 4 2头荷斯坦产奶牛分为 3组 ,每组 1 4头。采用完全随机化区组设计进行试验。处理为 3种大豆皮替代水平 ,即 :大豆皮分别替代精料中 0 % (对照 )、2 5%和 50 %的玉米与小麦麸 ;区组 ( 4个 )为产奶牛的不同胎次和泌乳月。正式试验期 1 2周。结果表明 ,用大豆皮替代产奶牛精料中 0 %、2 5%和 50 %的玉米和小麦麸 ,日粮干物质、蛋白质进食量、日产奶量、4 %乳脂率校正奶产量、产奶的饲料转化效率、乳蛋白、乳糖、无脂固形物含量均没有明显变化 (P >0 .2 0 ) ,乳脂率随大豆皮替代水平的提高呈直线上升趋势 (P =0 .0 8)。以大豆皮替代精料中 2 5%和 50 %玉米与小麦麸饲粮喂奶牛 ,每千克产奶的饲料成本平均分别降低 0 .0 4 5和 0 .0 57元     

Physiological responses to water restriction in dry and lactating Awassi ewes

The effect of water restriction in Awassi ewes was assessed under two physiological conditions: lactating and dry, over a 3-week-period (August–September, 2002). Eight dry and eight lactating Awassi ewes (with their lambs) were assigned to one of two watering regimes: watered once every three days and daily watering, respectively. Weather data, body weight and rectal temperature were recorded. Venous blood was sampled on the watering day of the water-restricted group, and subjected to haematological, biochemical and electrolytes analysis. Ewes under water restriction lost more weight and had higher packed cell volume, haemoglobin, serum cholesterol, urea, creatinine, total protein and albumin as compared to daily-watered animals. However, lactation seemed to have no significant effect on these serum components. As for blood pH and electrolytes, Na⁺ and Cl⁻ were significantly higher under water restriction; whereas significantly lower K⁺ and Ca⁺⁺ but higher pH and Cl⁻ were observed in lactating animals. Finally, lower cortisol concentrations were observed in water-restricted animals, warranting further studies on the hormonal adaptation to long term water stress. It was concluded that water restriction induces similar changes in blood physiological indicators in dry and lactating Awassi ewes; while lactation beyond the first month post partum seems to mostly affect blood electrolytes.     

努比羊和云岭黑山羊初产泌乳性能的研究

[目的]研究努比羊和云岭黑山羊初产泌乳性能。[方法]选择健康初产努比羊（产双羔20只、产单羔19只）和云岭黑山羊（产双羔4只、产单羔15只）,研究品种和产羔数对母羊初产泌乳力的影响。[结果]同品种间,产双羔努比羊和云岭黑山羊总产奶量比产单羔努比羊和云岭黑山羊高14.81%（P〈0.05）和32.8%（P〈0.05）;相同产羔数,产双羔努比羊总产奶量比产双羔云岭黑山羊高22.93%（P〈0.05）,产单羔努比羊总产奶量比产单羔云岭黑山羊高42.20%（P〈0.05）。产单、双羔努比羊和云岭黑山羊泌乳曲线规律相似,在泌乳前期（5～15 d）乳产量逐渐上升,泌乳高峰期（15～35 d）持续20 d后泌乳量逐渐下降。山羊产后80～120 d的产奶量预测值显示,不同品种和产羔数山羊产奶量均快速下降。泌乳70 d时,同品种间,产双羔的奴比羊和云岭黑山羊母羊失重比同品种产单羔母羊高3.06%（P〈0.05）和0.89%（P〈0.05）,相同的产羔数量,努比羊体重失重比云岭黑山羊高3.22%～5.39%（P〈0.05）。[结论]努比羊和云岭黑山羊初产泌乳规律相似,泌乳性能与品种、产羔数密切相关。     

激素和生长因子调控奶牛乳腺发育的研究进展

生长激素及同期发情技术等目前较好地应用于奶牛场的生产,但是生长因子、转录因子、受体及细胞内信号等因素最终决定了乳房发育的大小和泌乳能力的强弱。这些因素还有待进一步研究以指导生产实践。     

两种接产操作程序对哺乳仔猪腹泻的影响

通过规范接产操作程序和改善接产环境,哺乳仔猪的腹泻率、死亡率分别由31.23%、6.45%下降到12.75%、2.75%,二者相比分别下降了59.17%、57.36%,差异极显著（P〈0.01）。结果表明,加强接产前母猪的消毒及改善接产环境能显著降低哺乳仔猪腹泻率与死亡率。