Effects of stocking density on growth performance,blood parameters and immunity of growing pigs

This study was conducted to evaluate the effects of different stocking densities on growth performance, blood parameters, intestinal morphology and intestinal immunity of growing pigs. A total of 288 male pigs (44.35 ± 0.50 kg) were randomly assigned to groups with stocking densities of 2.46, 1.23 and 0.82 m²/pig for a month. The results showed that there was no significant difference on growth performance among groups. Pigs in the stocking density of 0.82 m²/pig had the lowest backfat thickness and spleen weight index among groups (P < 0.05). With increasing stocking density, the serum concentrations of blood urea nitrogen (BUN), transglutaminase (TGG), alkaline phosphatase (AKP) and immunoglobulin A (IgA) were increased, and albumin (ALB), albumin-to-globulin ratio (ALB:GLO), insulin-like growth factor-1 (IGF-1) and immunoglobulin (IgM) were decreased (P < 0.05), and cortisol tended to increase and glucose tended to decrease (0.05 < P < 0.1). Compared with the stocking density of 2.46 m²/pig, the ileal villus height and jejunal villus width decreased in stocking densities of 1.23 and 0.82 m²/pig (P < 0.05). The duodenal villus height and ileal villus width in the stocking density of 0.82 m²/pig were the lowest among 3 groups (P < 0.05). The content of immunoglobulin A in duodenum, jejunum and ileum mucosa increased along with increasing density (P < 0.05). The contents of interleukin (IL)-2 in the spleen or liver and IL-10 in the spleen were higher in the stocking density of 0.82 m²/pig than in other 2 groups. These results showed that stocking density could affect the metabolism, intestinal morphology, and immunity of growing pigs and 1.23 m²/pig may be the suitable stocking density for the growing pigs in the present study.     

Acclimation to high ambient temperature in Large White and Caribbean Creole growing pigs

The effect of breed [Creole (CR) vs. Large White (LW)] on performance and physiological responses during acclimation to high ambient temperature was studied in 2 experiments involving 24 (12/breed) growing pigs each. Pigs were exposed to 24 degrees C for 10 d (d -10 to -1) and thereafter to a constant temperature of 31 degrees C for 16 d (d 1 to d 16) in Exp. 1 and for 20 d (d 1 to d 20) in Exp. 2. For both experiments, the temperature change was achieved over 4 h on d 0. The first experiment began at 105 d of age, and the average BW of CR and LW pigs was 36.6 +/- 2.5 kg and 51.7 +/- 3.0 kg, respectively. The second experiment was designed to compare both breeds at a similar BW (about 52 kg on d 0). Pigs were individually housed and given ad libitum access to feed. At 24 degrees C, ADG was lower (P < 0.01) in CR than in LW (602 vs. 913 g/d and 605 vs. 862 g/d in Exp. 1 and 2, respectively), but the ADFI was not affected by breed (190 and 221 g x d(-1) x kg(-0.60) in Exp. 1 and 2, respectively). Short-term thermoregulatory responses during the 4-h transition from 24 to 31 degrees C (d 0) were analyzed according to a linear plateau model to determine the break point temperature, above which rectal temperature (RT), cutaneous temperature (CT), and respiratory rate (RR) began to change. The CT increased linearly with temperature increase (0.22 degrees C/ degrees C) and was less (P < 0.05) in CR than in LW (by -0.3 degrees C on average). In both experiments, the break point temperature for RT was not affected by breed (27.6 degrees C on average), whereas for RR it was greater (P < 0.05) in CR than in LW (27.5 vs. 25.5 degrees C, P < 0.01). On average, ADFI declined by about 50 g x d(-1) x kg(-0.60) from d -1 to d 1 (P < 0.01), and thereafter at 31 degrees C, it gradually increased (23 g x d(-1) x kg(-0.60); P < 0.05), suggesting an acclimation to high exposure. This response was not influenced by breed. After the day that marked the beginning of the acclimation response (i.e., the threshold day), RR, CT, and RT declined over the duration of exposure to 31 degrees C (P < 0.05) in both experiments. During this period, RT and CT were less in CR than in LW pigs (39.6 vs. 39.9 degrees C and 37.9 vs. 38.2 degrees C, respectively; P < 0.05), whereas RR was not affected by breed. The threshold day at which RT began to decline was less in CR than in LW pigs (0.18 vs. 1.17 d and 0.39 vs. 0.93 d in Exp. 1 and 2, respectively; P < 0.05). In conclusion, this study suggests that short- and long-term physiological reactions during heat acclimation differed when CR and LW pigs were compared at the same age or BW.     

高温对牛生殖内分泌及繁殖性能的影响

高温对牛的生殖内分泌和繁殖性能有很大的影响。高温情况下,牛的生殖内分泌模式发生改变,性成熟推迟,精子的生成受阻,精液质量下降.高温还影响母牛的发情和胚胎发育,使受胎率大大降低,妊娠期缩短.最后,提出了缓解高温对牛繁殖性能影响的措施     

A meta-analysis of the effects of high ambient temperature on growth performance of growing-finishing pigs

High ambient temperature (T) is one of the most important climatic factors influencing pig performance. Increased T occurs sporadically during summer heat waves in temperate climates and year round in tropical climates. Results of published experiments assessing the effects of high T on pig performance are surprisingly variable. Thus, a meta-analysis was performed to aggregate our knowledge and attempt to explain differences in the results across studies on the effect of increased T on ADFI and ADG in growing-finishing pigs. Data for ADFI and ADG were extracted from 86 and 80 trials, respectively, from articles published in scientific journals indexed in PubMed, Science Direct, and from proceedings of scientific meetings through November 2009. Data on ADFI and ADG were analyzed using a linear mixed model that included the linear and the quadratic effects of T and BW, and their interactions as continuous, fixed effects variables, and the trial as a random effect factor (i.e., block). In addition, the effects of housing type (2 levels: individual and group housing) and the year of publication (3 levels: 1970 to 1989, 1990 to 1999, and 2000 to 2009) on the intercept and the linear regression term for T (i.e., the slope) were also tested. Results showed that high T had a curvilinear effect on ADFI and ADG and that this effect was more pronounced in heavier pigs. Across T, ADFI was less when pigs were group-housed. The intercept and the regression coefficient (slope) for T were significantly affected by the year of publication. The effect of increased T was greater in more contemporary works, suggesting that modern genotypes could be more sensitive to heat stress than older genotypes of lesser growth potential. In conclusion, pig performance decreases at an accelerating rate as T is increased. The large between-study variability on the effects of high T on pig performance is partially explained by differences in pig BW and to a lesser extent by the year the study was published.     

Effects of ambient temperature on growth performance and carcass traits of male growing White Pekin ducks

ABSTRACT

1. An experiment was conducted to investigate the effects of ambient temperature on growth performance and carcass traits in male growing Pekin ducks from 14 to 42 d of age in order to establish their optimal temperature requirements.

2. A total of 216 14 d old male White Pekin ducks were allocated randomly to six environmentally controlled chambers with ambient temperature set at 20°C, 22°C, 24°C, 26°C, 28°C, and 30°C from 14 to 42 d of age, respectively.

3. As ambient temperature increased from 20°C to 30°C, the body weight and weight gain decreased linearly or quadratically (P < 0.05) and was accompanied by linearly decreasing feed intake (P < 0.05). According to broken-line regression, the upper critical level of ambient temperature during the growing period for body weight, weight gain, and feed conversion ratio were 27.4°C, 27.4°C, and 26.0°C, respectively.

4. The weight of breast meat, leg meat, and abdominal fat decreased linearly or quadratically as ambient temperature increased and declined to a minimum when the temperature increased to 30°C (P < 0.05). The percentage of breast meat and abdominal fat showed a linear or quadratic decreasing response to increasing temperature, but leg meat percentage increased as temperature increased and reached maximum at 30°C (P < 0.05). According to broken-line regression, the upper critical ambient temperatures during the growing period for breast meat weight and percentage were 25.5°C and 25.6°C, respectively.

5. It was concluded that both growth performance and breast meat of growing ducks were sensitive to increasing ambient temperature and this should be kept below the upper critical temperature during the growing period in order to optimise growth performance and carcass traits at market age.     

高温期维生素E和C对肥育猪生长与代谢的影响

将来源相同、体重相近 (55kg) 的杜长大生长肥育猪 36头 ,公母各半 ,随机分为 3个处理 ,每个处理设 3个重复 (各组间差异不显著 ) ,每个重复公母各 2头 ,在试验日粮中分别添加维生素C(50mg·kg- 1 )和维生素E(2 0 0mg·kg- 1 ) ,研究日粮维生素对持续高温期生长肥育猪生长性能与生化指标的影响。研究结果表明维生素E和C对持续高温期生长肥育猪的生长性能、内分泌功能、血清生化指标、血清电解质平衡等方面都会产生明显的影响。与对照组相比 ,生长肥育猪在热应激期采食维生素日粮后出现 :(1 )VC组平均日增重显著增加 (p <0 0 5) ;VC组和VE组间平均日增重差异不显著 (p >0 0 5) ;(2 )血清游离甲状腺素T4 显著增高 (p <0 0 5) ,游离T3也呈增高趋势 (p >0 0 5) ,VC组和VE组间血清T3、T4 浓度差异不显著 (p >0 0 5) ;(3)维生素组血清TP、ALB浓度显著增高 (p <0 0 5) ,血清BUN浓度显著降低 (p <0 0 5) ,而血清GLU、CHO、TG、GLO变化不显著 (p >0 0 5) ;(4)维生素组血清K+ 浓度显著增高 (p <0 0 5) ,Cl- 水平略有降低 ,Ca+ + 水平呈现出增加趋势 ,但变化都不显著 (p >0 0 5)。     

不同铜源对生长猪生产性能的影响

本试验采用单因素试验设计,选取48头平均体重为39kg的生长猪（杜×大×长）,按照体重接近、公母各半的原则随机分为4个处理组,每个处理3个重复,每个重复4头猪。4个处理组分别为：基础日粮（对照组）,即处理组1：处理组2、3、4分别在基础日粮中添加150mg／kg碱式氯化铜、200mg／kg碱式氯化铜、200mg/kg五水硫酸铜。探讨碱式氯化铜对生长猪生产性能的影响,并确定适宜添加量。试验结果表明：在日粮中添加200mg／kg碱式氯化铜能够显著提高生长猪的平均日增重（P〈0．05）,降低平均日采食量（P〉0．05）,改善料重比（P〉0．05）。因此,碱式氯化铜能有效替代五水硫酸铜作为生长猪的促生长剂。     

SSTR和IGFBP对生长猪生产性能的影响

选用 9周龄 1 9kg左右约·杜·长·宁四元杂种猪 60头 ,随机分为 3组 ,试验组I、试验组II和对照组各 2 0头。试验组I在 1 0、 1 3和 1 5周龄颈部皮下注射生长激素抑制激素受体 (SSTR)疫苗 ;试验组II在 1 0周龄颈部皮下注射SSTR +IGFBP (胰岛素样生长因子结合蛋白 )疫苗 ,1 3及 1 5周龄注射SSTR疫苗 ;对照组注射相同剂量的生理盐水。结果表明 :SSTR组平均日增重较对照组提高 5 73% ,采食量提高 3 88%。SSTR +IGFBP组平均日增重较对照组提高 9 74% ,采食量提高 1 1 1 6%。     

Effects of high dietary sodium chloride content on performance and sodium and potassium balance in growing pigs

Thirty castrated male Moo Lath pigs (6–8 weeks of age) were used in a 15-week growth trial to study the effect of high dietary sodium chloride (NaCl) content on feed and water intake, performance, sodium (Na) and potassium (K) balance, and plasma aldosterone concentration. The pigs were randomly allocated (ten per treatment) to diets containing 0.24 % Na (Na0.24), 0.28 % Na (Na0.28), and 0.32 % Na (Na0.32) per kg diet. Feed and water was provided ad libitum, and water consumption, feed offered, and feed residues were recorded daily. Every third week, the pigs were weighed, blood samples were collected, and a 3-day total collection of urine and feces was performed. Water intake was higher (P?=?0.001) in pigs fed with diets Na0.28 (3.7 L/day) and Na0.32 (3.9 L/day) than in pigs fed with diet Na0.24 (3.4 L/day), and dry matter (DM) intake was higher on diet Na0.32 (P?=?0.041) than on the other diets. The average daily body weight (BW) gain was higher on diet Na0.32 than on the other diets (P?=?0.031). The feed conversion ratio (in kilogram feed DM to kilogram BW gain) was 4.6, 4.6, and 4.1 on treatments Na0.24, Na0.28, and Na0.32, respectively (P?=?0.14). The highest Na balance was observed on diet Na0.32 followed by diets Na0.28 and Na0.24 (P?<?0.001), while there was no treatment-related pattern for the K balance. The Na/K ratio in feces and urine increased (P?<?0.001), and the K/Na ratio in feces (P?<?0.001) decreased with increasing Na content in the diet. Plasma aldosterone concentration decreased (P?<?0.001) with increasing dietary content of Na. These results indicate that high NaCl intake and free access to water will increase Na balance but do not negatively influence feed intake and performance of growing local pigs.     

Influence of a high ambient temperature on lipid metabolism in the growing pig

Because pigs are fatter when they are heat-stressed, it was hypothesized that lipid metabolism is enhanced in heat-stressed pigs. To test this hypothesis, an experiment was conducted to determine the influence of a high ambient temperature on the level of plasma lipids, thyroid hormones, lipoprotein lipase activity, and on the composition of very low density lipoproteins (VLDL) and chylomicrons in the growing pig. Twelve Large White x Landrace castrated male pigs with an initial weight of 20 +/- 0.6 kg were allotted to one of the following treatments: 1) ambient temperature of 31 degrees C, with ad libitum access to feed or 2) ambient temperature of 20 degrees C and fed the amount consumed by those kept at 31 degrees C until 35 kg BW. Ambient temperature did not affect piglet performance. Compared to that in pigs kept at 20 degrees C, in pigs kept at 31 degrees C the lipid content of backfat was 26% higher and the proportion of flare fat was increased by more than twofold (P < 0.001). Lipoprotein lipase activity was increased more than twofold in backfat and nearly twofold in leaf fat at 31 vs 20 degrees C (P < 0.001). In warmth-exposed (31 degrees C), feed-restricted pigs, the plasma level of triiodothyronine was 30% lower than at 20 degrees C (P < 0.001), whereas VLDL-lipid concentration was more than fourfold higher, and plasma concentrations of NEFA and triglycerides were 2.6- and 3.6-fold higher, respectively (P < 0.001). In conclusion, the chronic exposure of growing pigs to a high ambient temperature enhances lipid metabolism in both the liver (VLDL production) and the adipose tissue (lipoprotein lipase activity). Consequently, plasma triglyceride uptake and storage are facilitated in the adipose tissue, which results in greater fatness.     

Effects of stocking density on growth performance,meat quality and tibia development of Pekin ducks

This study was performed to investigate the effects of stocking density on performance, meat quality and tibia development in Pekin ducks reared on a plastic wire floor. A total of 372 healthy, 21‐day‐old, male ducks with similar body weight (BW) were randomly allotted to stocking densities of five (low), eight (medium) and 11 (high) birds/m². Each group had six replicates. Results showed that compared with the low density group, medium and high stocking density caused a decrease in final BW at 42 days old, and in average daily gain, European performance index (p < .01) and meat pH at 45 min postmortem (p < .001), and an increase of meat drip loss (p < .01). High stocking density resulted in an increase of feed/gain ratio (p < .001), but a decrease of tibia calcium (p < .01) and phosphorus content (p < .05). Meat color, shear force values, tibia size (weight, length, and width) and breaking strength were not significantly influenced by stocking density. In conclusion, stocking density over eight birds/m² negatively affects growth performance, but meat quality and tibia development are not dramatically influenced. Based on this study, the stocking density of male Pekin ducks should be adjusted between five and eight birds/m².     

Effects of exposure to high ambient temperature and dietary protein level on performance of multiparous lactating sows

Fifty-nine multiparous Large White x Landrace sows were used to determine the effects of high ambient temperature and level of dietary heat increment on lactation and reproductive performance. During a 28-d lactation and the 14-d postweaning period, ambient temperature was maintained constant at 20 or 29 degrees C. Experimental diets fed during lactation were a control diet (NP; 17.6% crude protein) and two low-protein diets obtained by reduction of CP level (LP; 14.2% CP) and both reduction of CP and addition of 4% fat (LPF; 15.2% CP); the NE:ME ratio was 74.3, 75.6, and 75.8% for NP, LP, and LPF diets, respectively. All diets provided 0.82 g of digestible lysine/MJ of NE, and ratios between essential amino acids and lysine were above recommendations. During the ad libitum period (i.e., between d 7 and 27 of lactation), ADFI and NE intake decreased, respectively, from 7.63 to 4.22 kg and 82.0 to 43.3 MJ of NE when the temperature increased from 20 to 29 degrees C. Exposure to 29 degrees C reduced litter BW gain (2,152 vs 2,914 g/d) and increased lactation BW loss (34 vs 16 kg) but increased postweaning BW gain (2 vs - 4 kg). Expressed per kilogram of feed intake, water intake increased from 4.0 to 7.5 L between 20 and 29 degrees C. Compared with the NP diet, low-CP diets (LP or LPF) maintained performance and reduced total N excretion (-22.5%) in lactating sows at thermoneutrality and attenuated the negative effects of high temperature on NE intake and BW loss (40.9 vs 47.9 MJ of NE/d and 41 vs 30 kg for NP and LP + LPF diets, respectively). Temperature and diet composition did not affect the reproductive performances, and the mean weaning-to-estrus interval was 4.9 d. The respiratory rate and skin, udder, and rectal temperatures increased markedly at 29 degrees C (105 vs 33 breaths per min and 37.8 vs 36.1 degrees C, 38.9 vs 38.2 degrees C, and 39.5 vs 38.8 degrees C, respectively) without any effect of diet. In conclusion, low heat increment diets (i.e., with reduced CP/NE ratio) did not affect lactation performance of sows at thermoneutrality and attenuated the effects of high ambient temperature on energy intake and BW loss. At any ambient temperature, N excretion can be markedly reduced.     

Effects of stocking density,light and perches on broiler growth

The aim of this study was to determine the effect of stocking density, light intensity and light color on broiler growth. The experiment consisted of four 35‐day phases during each of which 320 chickens were surveyed. The research was performed at stocking densities of four and six birds/m². Illuminances of 15 and 30 lx were obtained through commercial lamps with 4000 K and 6000 K color temperatures. Lighting was used 17 h a day, between 06.00 and 23.00 hours (17 L:7 D). The results showed a decrease in body, carcass, breast and thighs weight (P < 0.05) with the increase in stocking density. Body weight decreased by 10.5% and carcass weight decreased by 9.4% at six birds/m² stocking density. Contrastingly, no differences were found for the tested light colors. Increasing illuminance from 15 to 30 lx caused a 1.9% decrease in body weight. The analysis of the effect of perches revealed that using perches significantly increased body (2.5%) and breast weight (11.8%). The interactions between light intensity or color and stocking density and between light intensity and light color were analyzed.     

Effects of dietary tryptophan and stocking density on the performance,meat quality,and metabolic status of broilers

Background:Highly automated cage-rearing systems are becoming increasingly popular in China.However,a high stocking density can cause oxidative stress and decrease broiler performance.The tryptophan(TRP) derivative5-hydroxytryptophan(5-HT) has been shown to preserve membrane fluidity in birds suffering from oxidative stress.Therefore,this experiment was conducted to determine the effects of dietary TRP supplementation on performance,breast meat quality and oxidative stress in broilers reared in cages with a high or low stocking density.Methods:Female Arbor Acres broilers(25-d-old,n=144) were randomly allocated to 1 of 4 treatments.The birds were fed a diet based on corn,soybean meal,cottonseed meal and corn gluten meal containing either 0.18 or 0.27%TRP and were housed with stocking densities of 11 or 15.4 birds/m2 in a 2 × 2 factorial experiment.Broiler performance was evaluated from d 25 to 42.Eight birds from each treatment were slaughtered on d 42 and plasma and breast muscle samples were collected to measure biochemical indices.Results:A higher stocking density tended to be associated with reduced weight gain(P0.10),and significantly increased plasma glutamic-pyruvic transaminase(GPT) activity(P0.001).Increased dietary TRP significantly reduced the activities of lactic dehydrogenase and GPT while increasing total cholesterol in the plasma(P0.01),reducing drip loss of breast muscle(P0.10) and improving feed efficiency(P0.10).Conclusions:An increase in dietary TRP,1.5-fold higher than the standard supplementation level,can alleviate oxidative stress as well as improve welfare and feed efficiency in broilers reared in cages with a high stocking density.     

Fluctuating ambient temperature for weaned pigs: effects on performance and immunological and endocrinological functions

Following weaning at 3 wk of age, crossbred barrows and gilts were housed in temperature-controlled rooms for a 5-d adjustment period at 35 degrees C, then assigned to receive constant ambient temperature (CT) or fluctuating ambient temperature (FT) treatment for the nursery phase of the experiment. Pigs in FT received 12 h at 35 degrees C and 12 h at 15 degrees C daily for the initial 2 wk of the experiment, then 12 h at 29 degrees C and 12 h at 9 degrees C daily for the final 2 wk. Pigs in CT received 35 degrees C and 29 degrees C continuously for the first and final 2 wk, respectively. Weekly growth performance, feed intake and feed-conversion efficiency were not affected by treatment. Plasma glucose, serum cortisol, monocyte phagocytic function and antibody response to a commercial E. coli bacterin were similar in pigs exposed to CT and FT treatments. Concentrations of insulin in serum were similar between treatments at 0, 1 and 3 wk but were increased for pigs in FT at 2 (P less than .05) and 4 wk (P less than .01). Numbers of lymphocytes, band neutrophils and monocytes in pigs were not influenced by ambient temperature treatment. However, numbers of mature neutrophils for pigs in FT were increased (P less than .05) at 1 and 3 wk of treatment. Eosinophils were also elevated in FT pigs at 4 wk of treatment. Pairs of littermate pigs that had been given CT and FT treatments were selected randomly to continue on the finishing phase of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dietary tryptophan and stocking density on the performance,meat quality,and metabolic status of broilers

Background

Highly automated cage-rearing systems are becoming increasingly popular in China. However, a high stocking density can cause oxidative stress and decrease broiler performance. The tryptophan (TRP) derivative 5-hydroxytryptophan (5-HT) has been shown to preserve membrane fluidity in birds suffering from oxidative stress. Therefore, this experiment was conducted to determine the effects of dietary TRP supplementation on performance, breast meat quality and oxidative stress in broilers reared in cages with a high or low stocking density.

Methods

Female Arbor Acres broilers (25-d-old, n = 144) were randomly allocated to 1 of 4 treatments. The birds were fed a diet based on corn, soybean meal, cottonseed meal and corn gluten meal containing either 0.18 or 0.27% TRP and were housed with stocking densities of 11 or 15.4 birds/m² in a 2 × 2 factorial experiment. Broiler performance was evaluated from d 25 to 42. Eight birds from each treatment were slaughtered on d 42 and plasma and breast muscle samples were collected to measure biochemical indices.

Results

A higher stocking density tended to be associated with reduced weight gain (P < 0.10), and significantly increased plasma glutamic-pyruvic transaminase (GPT) activity (P < 0.001). Increased dietary TRP significantly reduced the activities of lactic dehydrogenase and GPT while increasing total cholesterol in the plasma (P < 0.01), reducing drip loss of breast muscle (P < 0.10) and improving feed efficiency (P < 0.10).

Conclusions

An increase in dietary TRP, 1.5-fold higher than the standard supplementation level, can alleviate oxidative stress as well as improve welfare and feed efficiency in broilers reared in cages with a high stocking density.     

Effect of stocking density on performance of broiler chicks

In two experiments space allowances of 0.143, 0.122, 0.105 and 0.093 m²/bird and 0.093, 0.078, 0.064 and 0.047 m²/bird were used and their effects on live‐weight, food consumption and food conversion of Cobb broilers up to 10 weeks old were measured.

When the space allowance was greater than 0.093 m²/bird there was no effect on any of the characters studied.

At 10 weeks old a decrease in space allowance from 0.093 to 0.047 m²/bird was accompanied by reduced final live‐weight and food consumption and increased efficiency of food conversion; the effect on live‐weight was smaller at 9 weeks and was not significant at 8 or 7 weeks.

It was concluded that in broiler experiments ending at 8 weeks a space allowance of 0.078 m²/bird (0.8 ft²/bird) is more than adequate.     

抗热应激剂对高温条件下生长猪生产性能和代谢的影响

选取体重约 2 0kg的杜× (长×大 )杂交猪 90头 ,随机分为 5个处理 ,每个处理 3个重复 ,每重复 6头 ,单栏饲养于试验猪舍内。各组分别饲喂含不同抗热应激剂的饲粮 ,对照组不含抗热应激剂 ,试验组依次添加中草药添加剂 2 %、蛋氨酸锌 5 30mg/kg、吡啶甲酸铬 2 0 0mg/kg和酸化剂 15 0 0mg/kg ,饲养期 4 9d。试验结果表明 :①含抗热应激剂各试验组的日增重和采食量均高于对照组 ,而蛋氨酸锌组和吡啶甲酸铬组的料重比均低于对照组 ;②从血清生化指标看 ,酸化剂组BUN(P <0 .0 5 )和SOD值 (P <0 .0 1)显著低于对照组 (P <0 .0 5 )。而各组的TG和MDA差异不显著 (P >0 .0 5 )。总之 ,中草药添加剂、蛋氨酸锌、吡啶甲酸铬和酸化剂均能增强生长猪在高温条件下的蛋白质分解和糖异生作用 ,进而改善生产性能