Effects of diets with different protein and DL-methionine levels on the growth performance and N-balance of growing minks

This study was performed to evaluate the effects of diets with different protein and dl-methionine (Met) levels on nitrogen (N) retention, nutrient digestibility, growth performance, and some blood parameters in growing minks. Eighty healthy male minks were selected and randomly divided into five groups with different types of diet. The dietary protein levels, expressed as percentage of dry matter (DM), were 36% (HP) and 28% (LP), corresponding to average 363g and 295g protein/kg DM, respectively. LP was supplemented with Met (0.3%, 0.6% and 0.9% DM); the codes were LP+M1, LP+M2 and LP+M3, respectively. From July to middle of September, the average daily gain and feed: gain ratio (F/G) of the minks that received the diet with 0.6% Met added to the low protein diet was better than feeding HP and other groups. Fecal N and Urinary N of group LP+M2 were the lowest one, in contrast, the daily retention of N was the highest one. Digestibility of DM and CP were not affected by different diets, but digestibility of fat declined with dietary protein level decreasing. Serum urea nitrogen (SUN) was affected by different protein and Met levels. Considering all factors the best performance could be observed offering LP+M2, the prime level of Met was 13.87 g/kg DM in dietary, and 258.5 g digestible protein kg(-1) DM was enough for mink in growing period. Furthermore, addition of Met in low protein diets for minks would be beneficial in terms of reduced feed expenses and lower nitrogen emissions to the environment.     

饲粮蛋白质水平对冬毛生长期水貂生长性能、血清生化指标及毛皮质量的影响

本文旨在探讨饲粮蛋白质水平对水貂生长性能、营养物质消化吸收、毛皮品质和血清生化指标的影响.随机选取日龄体重相近的70只健康公水貂平均分至5组,饲喂5个蛋白质水平的饲粮(32%、28%、24%、20%和16%),每千克干物质中含蛋白质分别为326.4、284.7、249.3、203.9和172.8 g.试验组编号分别为P...     

Effects of dietary supply of arginine on urinary orotic acid excretion,growth performance and blood parameters in growing mink (Mustela vison) kits fed low‐protein diets

Effects of dietary arginine levels of 1.2%, 1.7% and 2.2% of dry matter (DM) (4.8 g/16 g N, 6.4 g/16 g N and 8.0 g/16 g N, respectively) and excess dietary lysine (6.5% in DM, 22 g/16 g N) were investigated in male mink kits fed low‐protein diets supplemented with a mixture of amino acids in the growing period during 4 weeks in July‐August. Urinary excretion of orotic acid, growth performance, feed consumption, plasma concentrations of ammonia (NH₃), orotic acid, urea and glucose were studied. The results showed that arginine is an essential nutrient for mink kits in the growing period and that excess dietary lysine antagonizes arginine. An arginine supply of 2.2% of DM (8.0 g/16 g N) resulted in minimum urinary excretion of orotic acid and a supply of 1.7% of DM (6.4 g/16 g N) prevented increased plasma concentrations of NH₃. Growth performance was negatively affected by the low protein level in all diets. The plasma concentrations of orotic acid, urea and glucose were not affected by the dietary levels of arginine.     

饲粮维生素D和钙水平对育成期水貂生长性能、营养物质消化率及氮代谢的影响

本试验旨在研究在钙磷比固定的条件下,饲粮维生素D和钙水平对育成期水貂生长性能、营养物质消化率及氮代谢的影响。选取(60±5)日龄健康短毛黑公水貂117只,随机分成9组,每组13个重复,每个重复1只。试验采用3×3双因素随机试验设计,饲粮钙磷比固定为2,设3个维生素D水平,分别为2 100、4 100、6 100 IU/kg,3个钙水平,分别为2.3%、2.7%、3.1%,共配制9种试验饲粮,9种饲粮的钙与维生素D水平分别为2.3%与2 100 IU/kg(Ⅰ组)、2.3%与4 100 IU/kg(Ⅱ组)、2.3%与6 100 IU/kg(Ⅲ组)、2.7%与2 100 IU/kg(Ⅳ组)、2.7%与4 100 IU/kg(Ⅴ组)、2.7%与6 100 IU/kg(Ⅵ组)、3.1%与2 100 IU/kg(Ⅶ组)、3.1%与4 100 IU/kg(Ⅷ组)、3.1%与6 100 IU/kg(Ⅸ组)。预试期13 d,正试期60 d。结果表明:1)饲粮维生素D和钙水平对育成期水貂的末重、平均日增重、料重比均有极显著的影响(P0.01),末重、平均日增重均以Ⅷ组最高,Ⅰ组最低,料重比以Ⅷ组最低,Ⅰ组最高。2)育成期水貂脂肪消化率组间差异极显著(P0.01),Ⅱ、Ⅳ、Ⅴ组极显著高于Ⅶ、Ⅷ组(P0.01)。饲粮钙水平对育成期水貂干物质排出量有显著影响(P0.05),以钙水平为3.1%时最高;饲粮钙水平对育成期水貂脂肪消化率有极显著影响(P0.01),钙水平为3.1%时极显著低于钙水平为2.3%和2.7%时(P0.01)。饲粮维生素D水平极显著影响育成期水貂的干物质排出量(P0.01),以维生素D水平为4 100 IU/kg时最低;饲粮维生素D水平显著影响育成期水貂的干物质消化率、脂肪消化率(P0.05),二者均以维生素D水平为4 100 IU/kg时最高。3)饲粮钙水平对育成期水貂的氮沉积有显著影响(P0.05),且氮沉积呈现随饲粮钙水平的升高而增加的趋势,以钙水平为3.1%时最高。饲粮维生素D水平对育成期水貂的净蛋白质利用率、蛋白质生物学价值有显著影响(P0.05),且均以维生素D水平为4 100 IU/kg时最高。饲粮维生素D和钙水平对育成期水貂的净蛋白质利用率、蛋白质生物学价值均有显著的交互作用(P0.05),二者以Ⅷ组最高。综合各项指标,在本试验条件下,饲粮中钙磷比为2、维生素D水平为4 100 IU/kg、钙水平为3.1%时,育成期水貂可以获得较好的生长性能、较高的营养物质消化率及氮利用率。     

Reproductive performance is improved during seasonal anoestrus when female and male Murciano-Granadina goats receive melatonin implants and in Payoya goats when females are thus treated

This work investigates whether the reproductive performance of Mediterranean goats achieved using melatonin implants at around the spring equinox is affected by the protocol followed, i.e. implanting females only, males only, both sexes or neither sex. In a first experiment, Murciano-Granadina females (n = 419, 510 and 631 for three consecutive years) were divided into four groups: treated with melatonin (FM) and not treated with melatonin (FC), mounted by males treated with melatonin (MM) or not (MC). In a second experiment, performed during 2009, the same protocols were used with 635 Payoya females and the results compared with those obtained for the same year for the Murciano-Granadina breed. Fertility (percentage of goats kidding), litter size (number of kids born per female kidded) and productivity (number of kids per female in each mating group) were calculated. In the first experiment, better reproductive performances were obtained when females (overall fertility: 71.1% vs 57.0% for the FM and FC animals; productivity 1.37 ± 0.04 kids per female vs 1.12 ± 0.03 kids per female for the FM and FC animals; p < 0.01) or males (overall fertility: 65.9% vs 58.4 for the MM and MC animals; productivity 1.28 ± 0.03 kids per female vs 1.13 ± 0.04 kids per female for MM and MC groups, respectively; p < 0.01) were implanted with melatonin. Moreover, the interaction sex × melatonin treatment had a significant effect (p < 0.05) on productivity. In the second experiment, for the Murciano-Granadina breed, the greatest increase in the number of kids born per female was obtained when the females were treated with melatonin, in either the FM/MC or FM/MM protocols (0.54 extra kids and 0.53 extra kids per female, respectively) (p < 0.01). In the Payoya breed, the greatest increase was obtained using the FM/MC protocol (0.19 extra kids per female). Thus, improved reproductive performances are obtained when female Murciano-Granadina and Payoya goats are implanted with melatonin, although important differences in reproductive performance are seen between the breeds.     

日粮有机螯合锰添加水平对妊娠期水貂营养物质消化率及氮代谢的影响

本试验旨在研究日粮有机螯合锰添加水平对妊娠期水貂营养物质消化率及氮代谢的影响。试验采用单因子试验设计,选取150只健康成年雌性水貂,根据随机区组法分成5组,每组设30个重复,每个重复1只水貂。基础日粮中各组锰添加水平分别为0(Ⅰ组)、15(Ⅱ组)、50(Ⅲ组)、100(Ⅳ组)和500 mg/kg(Ⅴ组),锰以有机螯合锰形式添加。结果表明,妊娠期水貂的基础日粮中添加有机螯合锰水平为50 mg/kg时干物质表观消化率、蛋白质表观消化率最高,添加100 mg/kg时脂肪表观消化率达到最高;日粮有机螯合锰添加水平在100 mg/kg时对妊娠期水貂氮沉积、净蛋白质利用率和蛋白质生物学价值均最高,与0、500 mg/kg组相比差异显著(P＜0.05)。因此,在妊娠期水貂基础日粮中添加有机螯合锰的适宜范围为50~100 mg/kg。     

Effect of evening primrose oil as food supplement on reproduction in the mink.

The effects of addition of evening primrose oil (EPO) to a mink diet in the breeding season on the reproductive performance and kit and female performance during the lactation period were investigated in an experiment with 4 groups of male and female mink. Matings were carried out so that control males were mated to both control and supplemented females. Similarly, supplemented males mated both control and supplemented females. Reproductive results were evaluated both on a group basis and as an effect of male or female treatment, respectively. After males supplemented with EPO, there was a tendency for reduced rate of stillborn kits and kit losses during the first 21 days of life. These effects could not be explained physiologically. Female treatment did not affect reproductive performance, but there was a tendency for lower weight losses during lactation for EPO-supplemented females. Kit performance during the lactation period was independent of experimental treatment.     

Conception rates in farm mink (Neovison vison) in relation to first mating date,age and color variety

The aim of the study was to analyze the effects of the first mating date, age and color variety on the conception rates in farm mink. We analyzed female mink reproductive performance in 492 Sapphire and 463 Standard Black females over 3 or 4 years. The analysis included the number of inefficient matings, the interval between the first inefficient mating and the efficient mating (copulation) and the conception rates. The results show a significant effect of female's age and color variety on the conception rates. The youngest, yearling females of either color needed a higher number of matings per conception, as compared to older, 2‐ and 3‐year‐old females. Black females demonstrated a higher number of inefficient matings (1.066), as compared with Sapphires (0.730). Yearling females were most often mated from 1 to 10 March, and older females from 11 to 20 March. Older females achieved better conception rates than the yearlings. Dates between 11 and 25 March proved to be the optimum for the first mating, since the highest conception rates were observed if the females had mated during this period.     

不同锌水平对水貂生产性能及营养物质消化率的影响

研究不同锌水平对水貂生产性能及营养物质消化率的影响。结果表明：日粮中添加不同水平的锌有降低水貂干物质、有机物质、蛋白质和脂肪采食量的趋势;锌水平为30mg／kg时显著降低微量元素的排出量,减少微量元素对环境的污染。添加不同锌水平的锌显著提高生长期水貂的日增重。在日粮中添加ZnSO4·7H2O水平为30mg／kg时水貂日增重效果最好。     

日粮维生素D和钙水平对冬毛期水貂生长性能、营养物质消化率及氮、钙、磷代谢的影响

本试验旨在研究当日粮钙磷比一定时,维生素D和钙水平对冬毛期水貂生长性能、营养物质消化率及氮、钙、磷代谢的影响。随机选取（135±5）日龄、健康雄性水貂117只,分成9组,每组13个重复,每个重复1只。采用3×3双因素随机试验设计,设3个维生素D水平,分别为2 300、4 300、6 300 IU/kg;设3个钙水平,分别为2.0%、2.4%、2.8%,钙磷比固定为1.7∶1,配制9组试验日粮,分别为：Ⅰ组（2 300 IU/kg维生素D＋2.0%钙）、Ⅱ组（4 300 IU/kg维生素D＋2.0%钙）、Ⅲ组（6 300 IU/kg维生素D＋2.0%钙）、Ⅳ组（2 300 IU/kg维生素D＋2.4%钙）、Ⅴ组（4 300 IU/kg维生素D＋2.4%钙）、Ⅵ组（6 300 IU/kg维生素D＋2.4%钙）、Ⅶ组（2 300 IU/kg维生素D＋2.8%钙）、Ⅷ组（4 300 IU/kg维生素D＋2.8%钙）、Ⅸ组（6 300 IU/kg维生素D＋2.8%钙）。预试期13 d,正试期60 d。结果表明：①各组水貂料重比差异极显著（P<0.01）,Ⅱ组最低。钙水平对料重比有显著影响（P<0.05）,维生素D水平对料重比有极显著影响（P<0.01）。②钙水平可极显著影响粗脂肪消化率（P<0.01）,其中2.8%水平极显著低于2.0%和2.4%水平（P<0.01）。③日粮维生素D和钙水平对水貂氮代谢指标均无显著影响（P>0.05）。④各组水貂粪钙、粪磷、钙消化率、磷消化率均差异极显著（P<0.01）,其中Ⅱ组钙消化率、磷消化率最高,Ⅲ组次之。钙水平可极显著影响粪钙、粪磷、钙消化率、磷消化率（P<0.01）,2.0%水平可极显著降低粪钙、粪磷含量（P<0.01）,极显著提高钙消化率及磷消化率（P<0.01）。维生素D水平对钙消化率影响显著（P<0.05）,对粪磷、磷消化率影响极显著（P<0.01）,2 300~4 300 IU/kg维生素D水平有利于提高钙消化率、磷消化率,降低粪磷含量。综合考虑各项指标,在本试验条件下,日粮中钙磷比为1.7∶1,维生素D水平为2 300~4 300 IU/kg、钙水平为2.0%时,冬毛期水貂料重比及钙、磷排放量较低,而粗脂肪、钙、磷消化率较高。     

日粮粗蛋白质和粗脂肪水平对生长貉营养物质消化率和氮代谢的影响

试验旨在研究日粮中粗蛋白质和粗脂肪水平对生长貉营养物质消化率及氮代谢的影响,为生长貉的精准饲养提供科学依据。采用3×3完全随机设计,3个日粮粗蛋白质水平为22%、24%和26%,3个粗脂肪水平为7.5%、9.5%和11.5%。所有日粮中赖氨酸、含硫氨基酸和苏氨酸含量相等。将体重相近的11周龄健康公貉63只,随机分为9组,每组7只,单笼饲养,试验期共56 d。结果表明：日粮粗蛋白质和粗脂肪水平互作对生长貉能量和营养物质消化率、氮代谢指标均无显著影响（P>0.05）;日粮粗蛋白质水平影响干物质消化率（P<0.05）,其中日粮粗蛋白质水平为22%时干物质消化率显著高于粗蛋白质水平24%和26%组（P<0.05）;粗脂肪消化率随日粮粗脂肪水平增加而提高（P<0.05）,也有随日粮粗蛋白质水平增加而提高的趋势（0.05 < P < 0.10）。日粮粗蛋白质水平对氮沉积量无显著影响（P>0.05）,但显著影响日食入氮、日粪排出氮、日尿排出氮、蛋白质生物学价值和利用率（P<0.05）,日粮粗蛋白质水平为22%和24%时蛋白质生物学价值显著高于粗蛋白质水平26%组（P<0.05）;日粮粗脂肪水平显著影响日尿排出氮、沉积氮、蛋白质生物学价值和利用率（P<0.05）,其中日粮粗脂肪为9.5%和11.5%时沉积氮、蛋白质的生物学价值和利用率显著高于粗脂肪水平7.5%组（P<0.05）。以上结果表明,适当提高日粮粗脂肪水平、降低粗蛋白质水平,可降低尿氮排放,提高蛋白质的生物学价值和利用率。     

Influence of protein intake, energy intake and stage of gestation on growth, reproductive performance, nitrogen balance and carcass composition in gestating gilts

Thirty-six crossbred gilts were fed three levels of protein (146, 255 and 364 g/d) and two levels of energy (6,200 and 7,440 kcal of digestible energy/d) throughout gestation in a 3 x 2 factorial arrangement of treatments. Five-day N balance studies were conducted in early (0 to 30 d), mid- (30 to 60 d) and late (60 to 90 d) gestation. At slaughter (90 d of gestation), reproductive tracts were weighed and evaluated for reproductive performance and samples of the reproductive tract, liver and semimembranosus muscle (SM) were analyzed for crude protein. The right half of the carcass was subjected to a physical separation of fat, lean and bone. Neither dietary protein nor energy level significantly affected weight gain or reproductive performance. Nitrogen retention increased as dietary protein level increased and stage of gestation progressed (linear effect, P less than .01), but efficiency of N utilization and dry matter digestibility decreased with increasing protein intakes (quadratic effect, P less than .05 and linear effect, P less than .01, respectively). Nitrogen retention (P less than .01), efficiency of N retention (P less than .05) and dry matter digestibility (P less than .01) were higher in gilts fed high (H) energy compared with gilts receiving moderate (M) energy diets. Increasing dietary protein increased total carcass separable lean tissue (quadratic effect, P less than .01), liver weight (linear effect P less than .01) SM weight (quadratic effect, P less than .05) and SM percentage M (linear effect P less than .10). Similarly, total carcass N and carcass lean N increased as protein level increased (quadratic effect, P less than .10, P less than .05, respectively). In contrast to the increase in muscle N, N in uterine tissue and fluids was not affected by dietary protein level. The results of this experiment suggest that 146 g of crude protein/d during gestation is just as effective as higher levels of crude protein for litter size or storage of N in reproductive tissue, but 255 to 364 g of protein/d are required to maximize muscle N.     

Effect of energy and protein levels on performance,egg quality,and nutrient digestibility of laying pigeons

A total of 3,240 female Taisheng pigeons at 40 wk age were fed 9 diets containing 3 ME levels (2,630, 2,770, and 2,940 kcal/kg) and 3 CP levels (14.0, 15.0, and 16.0%) in a factorial arrangement. These diets were fed to investigate the effects of ME and CP on performance, egg quality, and nutrient digestibility. Female pigeons were housed under the same managerial conditions and randomly assigned into 9 treatments (6 replicates of 60 birds each). Two female–female paired pigeons housed in one cage were under a 16L:8D lighting cycle. Feed in pellet form and water were provided for ad libitum consumption. The study lasted 12 wk. As dietary ME level increased from 2,630 to 2,940 kcal/kg, BW, egg production, and apparent DM, crude fat (CF), and phosphorus (i.e., P) digestibilities increased (P < 0.05), feed intake decreased (P < 0.05), and feed conversion efficiency increased (P < 0.05). Increasing the level of dietary protein from 14 to 16% resulted in an increased (P < 0.05) BW, shell percentage, length of the major axis, and DM digestibility. Therefore, dietary ME had a greater influence on the performance of Taisheng laying pigeons than did dietary protein.     

Replacement of soybean meal with levels of inclusion of soya waste in the diet of growing goats

An experiment was conducted to investigate the effect of replacing soybean meal with soya waste at different levels on intake, digestibility and growth in goats. Eighteen male goat kids with initial body weight (BW) of 13.0 kg were distributed equally to three dietary groups. They were fed Napier grass (Pennisetum purpureum) and concentrate mixture, and each goat was assigned to an individual pen. Soybean meal in the concentrate mixture was replaced with soya waste at 0% (T1), 50% (T2) and 100% (T3) levels in respective dietary groups. These diets were isocaloric and isonitrogenous. Results showed that animals fed T3 diet exhibited higher Napier grass intake than those fed T1 or T2 diet. There was no influence on total intakes of dry matter (DM), organic matter (OM), crude protein (CP), metabolic BW, per cent BW and metabolisable energy by the dietary groups. However, there was an increasing trend on intake and digestibility of neutral detergent fibre (NDF) with increasing levels of soya waste in the diets. Animals fed T3 diet showed higher intake and digestibility of NDF than those fed T1 diet. There was no influence of the dietary groups on digestibilities of DM, OM and CP. Similarly, there was no effect of them on the final BW, total BW gain, daily BW gain, feed conversion ratio and feed cost. Soya waste can replace 100% soybean meal in diets for growing goats, because no change was observed in nutrient intake, digestibility and growth performance; inclusion of soya waste enhanced the intake and digestibility of NDF.

     

Energy metabolism and protein balance in growing rats fed different levels of dietary fibre and protein.

A study was performed to investigate the effect of different levels of dietary fibre (DF) and dietary protein on visceral organ size, digestibility, nitrogen balance and energy metabolism in rats. Thirty-six male Wistar rats, initial body weight about 76 g were used in a factorial design consisting of three levels of DF (low, 100 g/kg DM: medium, 250 g/kg DM and high, 290 g/kg DM) and two levels of dietary protein (low, 120 g/kg DM and high, 223 g/kg DM). The added fibre source was soybean hulls and Danish fish meal was used as sole source of dietary protein. Measurements of gas-exchange were done on six rats (one group) while urine and faeces were collected individually. The ratio of food/empty body gain increased (P<0.05) with increasing DF and decreasing levels of dietary protein. The weight of the digestive tract was larger (P<0.05) in rats fed the high fibre diet than in those fed the low fibre diet. The digestibility of nutrients and energy decreased linearly with increasing level of soybean fibre (P<0.05). An increased intake of DF was associated with a concomitant loss of protein and energy to faeces. The microbial degradation of NSP and other unabsorbed carbohydrates caused considerably changes in N metabolism of the colon. In rats fed the low protein diets increased levels of DF decreased N excretion in urine and increased N excretion in faeces, while the ratio of retained/digested protein remained constant. When rats were fed the high protein diet protein retention dropped in response to DF both absolute and relative to digested amount, indicating that energy intake could be a limiting factor. Heat production as a percentage of metabolizable energy (HP/ME) was higher (P<0.05) in rats fed the low protein diet than in rats fed the high protein diet, but no significant difference was found among DF levels.     

Effects of dietary nonprotein nitrogen on performance, digestibility, ruminal characteristics, and microbial efficiency in crossbred steers

Two trials were conducted to evaluate the effects of dietary NPN levels on animal performance, diet digestibility, ruminal characteristics, and microbial efficiency. Experiment 1 was conducted with 24 Holstein x Nellore crossbred steers (350 +/- 20 kg of BW) distributed in 6 blocks to evaluate intake and digestibility of nutrients and performance. The diets consisted of 70% corn silage and 30% concentrate (DM basis) and were formulated to contain 12.5% CP (DM basis). Treatments consisted of 0, 15.5, 31, and 46.5% of dietary N as NPN. There were no treatment differences in the daily intakes of DM (P = 0.47), OM (P = 0.60), CP (P = 0.24), nonfiber carbohydrates (NFC; P = 0.74), or TDN (P = 0.63); however, NDF intake decreased linearly as NPN increased (P = 0.02). Additionally, no effects of NPN were observed on apparent total tract digestibility of DM (P = 0.50), OM (P = 0.53), NDF (P = 0.63), or NFC (P = 0.44). The apparent total tract digestibility of CP increased linearly (P = 0.01), but ADG (1.14 kg/d) was not influenced (P = 0.96) as NPN increased. In Exp. 2, 4 ruminally and abomasally cannulated steers (300 +/- 55 kg of BW) were fed the same diet used in Exp. 1 to evaluate the effects of NPN levels on intake and digestibility of nutrients, ruminal characteristics, and microbial efficiency. There were no differences in the daily intakes of DM (P = 0.22), OM (P = 0.17), CP (P = 0.31), NDF (P = 0.29), or TDN (P = 0.49). However, NFC intake increased linearly (P = 0.02), and there was a quadratic effect (P = 0.01) on intake of ether extract as NPN increased. Ruminal digestibility of CP increased linearly (P = 0.01) with the increase of dietary NPN. There were no differences (P >or= 0.28) in microbial protein synthesis and microbial efficiency among the treatments. The results of these trials suggest that dietary NPN levels (up to 46.5% of total N) can be fed to crossbred steers receiving corn silage-based diets without affecting their growth performance or ruminal protein synthesis.     

Effects of dietary protein levels on digestibility of nutrients and growth rate in young female mink (Mustela vison)

This study investigated digestibilities of nutrients and feed efficiency in female mink at the different dietary protein levels during the mink growth period. Effects of dietary protein on growth performance of minks were also measured. Sixty 45‐day‐old healthy female minks were randomly assigned to 6 treatment groups with 10 animals in each group. Animals were fed diets varying in protein levels: 28% (Group I), 30% (Group II), 32% (Group III), 34% (Group IV), 36% (Group V) and 38% (Group VI), respectively. The digestibilities of key nutrients were determined on Day 14 after initiating the experiment and the last 3 days. From the beginning of the study, body weight and feed intake were weighed and recorded every other week in order to calculate the average daily bodyweight gain and the feed efficiency. The trial had demonstrated that nitrogen intake was greatly significantly different, which was affected by dietary protein levels (p < 0.001). Growth performance of minks was impaired when dietary protein level was at 28%. When dietary protein level was at 34%, minks had the best daily gains, feed efficiency, and digestibilities of some key nutrients.     

Prognostic indicators of post partum viability of kids born to Escherichia coli-vaccinated or unvaccinated does

This study was undertaken to determine some blood and other physiological parameters with potential for use as prognostic indicators of viability of newborn goat kids. Of the 143 kids born during the on-farm study, 97 were crosses of Galla x Small East African (SEA) and 46 were pure SEA. The SEA x Galla kids were 46 single males, with a mean body weight at birth of 2.77 +/- 0.22 kg, 43 females with a mean body weight at birth of 2.36 +/- 0.76 kg and 5 and 3 sets of female and male twins (mean body weight at birth of 1.8 +/- 0.19 kg and 2.05 +/- 0.07 kg for the female and male kids, respectively). The SEA kids comprised 36 single male and female kids (mean body weight at birth of 2.48 +/- 0.04 kg and 10 sets of twins (both male and female) (mean body weight at birth of 1.50 +/- 0.04 kg ). Pre-suckling sera obtained on-station from kids born of does vaccinated against Escherichia coli (n = 8) and unvaccinated does (n = 7) had a total protein content of <40.0 g/l and no detectable levels of IgG and A or E. coli antibodies. Sera obtained 12 hours post partum) from kids that survived in both groups contained about 19-22 g of Ig g/l, 50-80 g total protein/l, blood glucose of >5 mmol/l and had an E. coli antibody titre of between 1/160 and 1/640. On the other hand, kids that died within 48 hours of birth (parturient deaths) and had been classified in categories 3 and 4 righting reaction had low (<40 g/l) total protein, low white blood cell count (4,000/ml) and low blood glucose concentration (<4.9 mmol/l). It is concluded that kids with delayed righting reaction (>45 minutes), low rectal temperature (<36 degrees C), low birth weights (<1.5 kg for singles and <1.0 kg for twins), low white blood cells (<4,000/ml), low (<2 mmol/l) blood glucose levels, low total protein (<40.0 g/l), low (<1:160) E. coli antibody titre and IgG (< or =3,350 mg/l) in sera obtained 12 hours after birth have a poor prognosis for survival.     

水貂不同赖氨酸、蛋氨酸水平颗粒饲料对营养物质消化代谢的影响

为确定水貂适宜氨基酸组成、降低饲料成本,试验选取成年健康公母水貂各60只,随机分成6组,采用2×3因子试验设计,即赖氨酸2个水平,分别为1.85%和1.7%,蛋氨酸3个水平分别为0.81%、0.99%和1.24%,对采食正常试验组水貂进行了消化代谢试验。结果表明:①日粮赖氨酸水平的变化对公母貂干物质摄入、排出及消化率影响不显著(P>0.05);蛋氨酸水平的变化对母貂干物质摄入、排出及消化率影响不显著(P>0.05),公貂粪干物质排出量蛋氨酸水平为0.99%组显著低于蛋氨酸水平为1.24%组(P<0.05),公貂干物质消化率蛋氨酸水平为0.99%组极显著地高于蛋氨酸水平为0.81%组和1.24%组(P<0.01)。②日粮赖氨酸水平的变化对公母貂有机物摄入、排出及消化率影响不显著(P>0.05);蛋氨酸水平的变化对公母貂有机物摄入、排出及母貂消化率影响不显著(P>0.05),公貂蛋氨酸水平为0.99%组有机物消化率显著高于蛋氨酸水平为0.81%组(P<0.05),与蛋氨酸水平为1.24%组差异不显著(P>0.05)。③公母貂蛋白质消化代谢受赖氨酸水平变化的影响不显著(P>0.05);公母貂蛋白质摄入及粪蛋白的排出受蛋氨酸水平变化影响不显著(P>0.05),蛋氨酸为1.24%时公貂尿蛋白排出显著高于0.99%水平组(P<0.05),与0.81%水平组尿蛋白排出差异不显著(P>0.05);公貂蛋白存留0.99%水平组极显著高于1.24%水平组(P<0.01);公貂蛋白质消化率0.99%水平组显著高于1.24%水平组(P<0.05),与0.81%水平组差异不显著(P>0.05);母貂蛋氨酸水平变化对各消化代谢率指标影响不显著(P>0.05)。④1.85%赖氨酸水平组公貂赖氨酸摄入、尿排出及消化代谢率均显著高于1.7%赖氨酸水平组(P<0.05),母貂间差异不显著(P>0.05),赖氨酸水平对公母貂蛋氨酸摄入、粪尿排出及消化代谢率无显著影响(P>0.05);蛋氨酸水平对公母貂赖氨酸摄入、粪尿排出无显著影响(P>0.05),蛋氨酸0.99%水平公貂赖氨酸消化代谢率均极显著高于蛋氨酸1.24%水平和0.81%水平公貂(P<0.01),蛋氨酸水平对母貂间赖氨酸消化代谢率无显著影响(P>0.05);蛋氨酸水平对公母貂蛋氨酸摄入、粪尿排出及消化代谢率均有显著影响(P<0.05),随着蛋氨酸水平的降低,蛋氨酸的摄入逐渐降低,而尿排出蛋氨酸1.24%组显著高于0.99%和0.81%水平组(P<0.05);蛋氨酸0.99%和1.24%水平组公母貂蛋氨酸的消化代谢率均极显著高于0.81%水平组(P<0.01),蛋氨酸0.99%和1.24%水平组公母貂蛋氨酸的消化代谢率无显著差异(P>0.05)。     

The effect of protein supplementation on nitrogen utilization in lactating dairy cows fed grass silage diets

The study set out to examine the effects of supplementing grass silage with various levels of protein concentration and degradability on dietary nitrogen (N) excretion in lactating dairy cows consuming at least 60% forage. Six Holstein/Friesian cows in early to midlactation were offered six diets comprising two levels of crude protein (210 and 290 g/kg DM) and three levels of protein degradability in the concentrate achieved using different amounts of untreated or formaldehyde-treated soybean meal. Despite a difference of almost 100 g/d in N intake, apparent fecal and milk N outputs were not significantly affected. Protein degradability also had no effect on N outputs in feces and milk. However, there was a major effect of both level and degradability of CP on urinary N output. Moreover, an interaction between level and degradability of CP was detected, such that the rate at which urinary N increases with increasing CP degradability was higher on the high-CP than on the low-CP diet. A low level of protein (150 g/kg DM in the diet) and medium to low rumen-degradable protein supplements provided a significant reduction in N excretion without compromising lactational performance (mean 24.8 kg/d), in terms of both milk yield and composition. This study also demonstrated that a high efficiency of N utilization could be achieved on low-CP diets (supplying less than 400 g N/d), with feces being the main route of N excretion, whereas an exponential excretion of urinary N was observed as N intake exceeded 400 g N/d.