Response of growing-finishing pigs to decreasing floor space allowance and(or) virginiamycin in diet

Five hundred forty crossbred pigs were utilized in four trials (10 replications) at two stations to determine the separate and interacting effects of decreasing floor space allowance with or without the addition of virginiamycin to the diet on performance of growing-finishing pigs. Pigs were allowed .37, .33 or .28 m2/pig during the growing phase (23 to 55 kg) and .74, .66, .56 m2/pig during the finishing phase (55 to 100 kg) and fed either a corn-soybean meal control diet or the control diet plus 11 mg of virginiamycin/kg of diet. Floor space allowances were achieved by varying pen size, so the number of pigs and feeder space per pig were constant for all pens. During the growing phase, daily gain (P less than .01) daily feed intake (P less than .05) and feed conversion ratio (P less than .05) decreased as floor space allowance decreased. During the finishing phase and for the total test period, daily gain (P less than .01) and feed conversion ratio (P less than .05) were reduced but daily feed intake was not affected (P greater than .05) by restricted floor space allowance. The addition of virginiamycin to the diet had no effect on pig performance. The virginiamycin X floor space allowance interaction was not significant, suggesting that pigs fed a diet with or without virginiamycin responded similarly to restricted floor space allowance. The data suggest that the addition of virginiamycin to the diet was ineffective in overcoming the decrease in performance of growing-finishing pigs caused by crowded conditions.     

The growth performance of the progeny of two swine sire lines reared under different floor space allowances

A total of 736 pigs was used in a study with a 2 x 2 x 2 factorial arrangement to investigate the effects of and interactions between sire line (Line A vs. B), floor space (unrestricted vs. restricted), and gender (barrow vs. gilt) on growth performance, BW, and protein and estimated lipid accretion curves from 40 to 120 kg of BW. Pigs were by eight Line-A and nine Line-B sires mated with PIC C22 dams. Line A was of Pietrain ancestry and Line B was a synthetic line. The unrestricted floor space treatment consisted of small groups (four pigs) with 0.93 m2/pig of floor space for the entire grow-finish period. Pigs in the restricted floor space were in larger groups (12 pigs) with 0.37 and 0.56 m2/pig of floor space for the grower and finisher phases, respectively. Pigs were given ad libitum access to a three-phase dietary program, and one and three nipple waterers were available in the groups of 4 and 12 pigs, respectively. No sire line x floor space interactions were found for any of the traits measured. Line A pigs grew more slowly (50 g/d, P < 0.05), took longer (4.1 d, P < 0.05) to reach harvest weight (120.3 kg), and had similar feed intakes, but a lower gain:feed ratio (2.8%, P < 0.05) than Line B pigs. Line A pigs had greater longissimus muscle depth (P < 0.05) and estimated protein accretion rate (P < 0.05) than Line B pigs, but Line A and Line B pigs had a similar estimated percentage of lipid-free soft tissue. Pigs reared in the restricted floor space grew more slowly (105 g/d, P < 0.05) and consumed less feed (280 g/d, P < 0.05) but had a similar (P > 0.05) gain:feed ratio to pigs reared in the unrestricted floor space. Pigs reared in the unrestricted floor space had greater (P < 0.05) predicted protein and lipid accretion rates throughout the growth period than pigs reared in the restricted floor space. Differences between genders for growth traits and carcass measurements were in agreement with previous research. The differences in growth performance, carcass measures, and compositional growth curves between these two sire lines were similar in the two floor spaces.     

饲料企业生产车间绩效考核体系研究

随着畜牧产品市场的不断变化,市场竞争的日益加剧,饲料企业在目前的发展阶段面临着诸多挑战。为了更好地生存与发展,饲料企业需要通过绩效考核来提高生产车间的效率,从而增加经济效益。本文分析了目前我国饲料企业生产车间绩效考核的现状和存在的问题,探讨了优化和完善生产车间绩效考核体系的相关措施,以期能够提高生产车间的工作效率和饲料企业的经济和社会效益。     

Effect of restricted postweaning growth resulting from reduced floor and feeder-trough space on pig growth performance to slaughter weight in a wean-to-finish production system

The effect of reduced pig growth rate postweaning as a result of restricted floor space and feeder trough space on subsequent growth to slaughter was investigated in a wean-to-finish system. Crossbred pigs (n = 1,728) were used in a randomized block design with a 2 x 2 x 2 factorial arrangement of treatments: 1) floor space (high [0.630 m2/pig] vs. low floor space [0.315 m2/pig]), 2) feeder trough space (unrestricted [4 cm/pig] vs. restricted feeder trough space [2 cm/pig]), and 3) period of imposing floor- and feeder-trough-space treatments (12 vs. 14 wk postweaning). Growth performance was measured from weaning (5.5 +/- 0.01 kg of BW; 17 d of age) to slaughter (the end of wk 25 postweaning). From the end of the treatment period to the end of wk 25, pigs on all treatments had the same floor and feeder trough space. Pigs with low floor space had lower (P < 0.01) ADG, ADFI, and gain:feed ratio than those with high floor space, and were therefore lighter (P < 0.05) at the end of the postweaning treatment period. Pigs given the restricted feeder trough space had lower (P < 0.05) ADFI, similar (P > 0.05) ADG, and higher (P < 0.01) gain:feed ratio than those with unrestricted feeder trough space during the treatment period. Pigs in the 14-wk treatment period had higher (P < 0.01) ADG and ADFI, but lower gain:feed than those in the 12-wk treatment during that period. In the subsequent period, from the end of treatment to wk 25, there was an interaction (P < 0.05) between floor space and treatment period; the difference in ADG and gain:feed for pigs on low vs. high floor space was greater for the 14-wk than the 12-wk treatment period. However, low-floor-space pigs tended (P = 0.06) to be lighter than high-floor-space pigs at the end of wk 25 postweaning. Neither feeder trough space nor treatment period affected pig growth performance during the period from the end of treatment to wk 25. Carcass backfat and longissimus depths at the end of wk 25 were not influenced (P > 0.05) by treatment. In summary, pigs with restricted growth due to low floor space until either 12 or 14 wk postweaning had increased growth and feed efficiency in the subsequent period to wk 25 postweaning, with only a slight effect on BW and no effect on carcass measures.     

Effect of group size and feeder type on growth performance and feeding patterns in growing pigs

The effects of four group sizes (2, 4, 8, and 12 pigs per pen) and two single-space feeder types (conventional and electronic feed intake recording equipment [FIRE]) on feed intake, growth performance, and feeding patterns were determined in growing pigs over a 4-wk period. A total of 416 hybrid pigs (barrows and gilts) were grown from 26.5 (SD = 1.6) to 47.8 (SD = 2.7) kg BW and given ad libitum access to a corn-soybean meal-based diet (17.4% CP; 0.9% lysine; 3,298 kcal ME/kg). The floor space allowance was 0.9 m2/pig for all treatments. Pigs using the electronic feeders had similar growth rates but lower feed intakes (P < 0.01) and higher gain:feed ratios (P < 0.01) compared to those using the conventional feeders. Barrows compared to gilts had higher growth rates (P < 0.05), numerically higher (P > 0.05) ADFI, and similar feed efficiency and feeding pattern. Feed intakes and growth rates were lowest (P < 0.05) for groups of 12 pigs but gain:feed ratio was not affected by group size. Daily feeder occupation time per pig was lower (P < 0.01) for groups of 12 than for groups of 2 or 4 pigs, and feed consumption rate was higher (P < 0.01) for groups of 12 than for groups of 4 pigs. The proportion of time spent eating was lower (P < 0.01) and the proportion of time spent standing was higher (P < 0.01) for pigs in groups of 12 compared to groups of 2. Correlations between ADG and ADFI and feed intake per visit were 0.29 and 0.30, respectively (P < 0.01), between ADG and ADFI and feed consumption rate were 0.27 and 0.31, respectively (P < 0.01), and between ADFI and feeder occupation time per day were 0.33 (P < 0.01). This study suggests that, in growing pigs given access to a single feeder, changes in feeding behavior with increasing group size were not sufficient to maintain feed intake and growth rate.     

Risk factors associated with Salmonella enterica prevalence in three-site swine production systems in North Carolina, USA

The goal of this study was to identify risk factors associated with increased fecal shedding of Salmonella enterica (SE) in groups of market swine reared in large three-site production units. We conducted an intensive, long-term investigation of potential management and environmental risk factors operating during the growing phase of pig production. Data regarding finisher site characteristics, biosecurity protocols, group growth performance, medication usage, and environmental temperature were collected. Results indicate that SE infection is common. Risk factors were identified at both the finisher site and group level. Biosecurity and hygiene practices (absence of a toilet, more than 2 people present at a finisher site daily, and other domestic species at the site), environmental temperature (winter and spring seasons, increased temperature variability, and below median high temperature the day of sampling), and production performance (above median feed conversion) were associated with elevated SE prevalence. In addition, an association between the floor space allowances per pig at the time of sampling (a measure of the number of pigs sold prior to sampling) was identified, with greater space allowance associated with decreased prevalence. The results of this study identify potential management practices for evaluation for SE control and suggest caution in interpretation of fecal culture results when sampling from different marketing groups in swine production systems.     

Effects of restricted feed intake on finishing pigs weighing between 68 and 114 kilograms fed twice or 6 times daily

In a previous study with limit-fed gestating gilts, we observed that gilts fed 6 times/d had greater ADG than those fed the same amount over 2 feedings. To confirm these earlier responses, we used finishing pigs as a model in two 42-d trials and two 28-d trials to evaluate the effects of restricted feed intake and feeding frequency (2 vs. 6 times/d, floor fed) on pig performance between 68 and 114 kg. In all experiments, pigs (10/pen) were housed in 1.8 × 3.1 m pens with a half-solid, half-slatted concrete floor. Pigs were fed a corn- and soybean meal-based diet formulated to 1.15% standardized ileal digestible Lys and 3,294 kcal of ME/kg. In Exp. 1 to 3, energy and Lys were supplied to pigs according to NRC (1998) calculations to target an ADG of 0.80 kg. In Exp. 4, the diet was supplied to pigs to target an ADG of 0.80 kg (low feed intake) or 0.95 kg (high feed intake) to determine if the amount of energy above the maintenance requirement and feeding frequency affected pig performance. Pigs were fed by dropping similar amounts of feed onto the solid concrete floor either 2 (0700 or 1400 h) or 6 times (3 meals within 2 h at the morning and afternoon feedings) per day with an Accu-Drop Feed Dispenser (AP Systems, Assumption, IL). In Exp. 1 and 2, pigs fed 6 times daily had increased (P < 0.02) ADG and G:F compared with pigs fed 2 times per day. Greater feeding frequency increased (P < 0.05) the duration of time spent feeding and standing and reduced the lying time. In Exp. 3, a third treatment was included to determine whether the improvements in performance were due to decreased feed wastage. This treatment was designed to minimize feed wastage by dropping feed closer to the floor for pigs fed 2 times per day. Pigs fed 6 times daily had improved (P < 0.05) ADG and G:F compared with pigs in either treatment fed 2 times per day. No difference (P > 0.05) in performance was observed between pigs fed 2 times per day when feed was dropped from the feed drop or by the modified method. In Exp. 4, increasing the feeding frequency from 2 to 6 times per day improved (P < 0.01) ADG and G:F for pigs fed the low feed intake and tended to increase (P < 0.06) ADG and improved (P < 0.05) G:F for pigs fed the high feed intake. In limit-feeding situations, increasing the frequency of feeding from 2 to 6 times per day improved pig performance, which confirmed our earlier findings in gestating gilts.     

Breeding objectives for Targhee sheep

Breeding objectives were developed for Targhee sheep under rangeland production conditions. Traits considered were those for which EPD were available from the US National Sheep Improvement Program and included direct and maternal effects on 120-d weaning weight (WW and MM, respectively); yearling weight (YW); yearling fleece weight, fiber diameter, and staple length; and percent lamb crop (PLC), measured as the number of lambs born per 100 ewes lambing. A bioeconomic model was used to predict the effects of a change of 1 additive SD in EPD for each trait, holding all other traits constant at their mean, on animal performance, feed requirements, feed costs, and economic returns. Resulting economic weightings were then used to derive selection indexes. Indexes were derived separately for 3 prolificacy levels (1.41, 1.55, and 1.70 lambs/ewe lambing), 2 triplet survival levels (50 and 67%), 2 lamb pricing policies (with or without discounting of prices for heavy feeder lambs), and 3 forage cost scenarios (renting pasture, purchasing hay, or reducing flock size to accommodate increased nutrient requirements for production). Increasing PLC generally had the largest impact on profitability, although an increase in WW was equally important, with low feed costs and no discounting of prices for heavy feeder lambs. Increases in PLC were recommended at all 3 prolificacy levels, but with low triplet survival the value of increasing PLC eventually declined as the mean litter size increased to approximately 2.15 lambs/ewe lambing and above. Increasing YW (independent of WW) increased ewe maintenance costs and reduced profitability. Predicted changes in breeding values for WW and YW under index selection varied with lamb pricing policy and feed costs. With low feed costs or no discounts for heavy lambs, YW increased at a modest rate in association with increasing WW, but with high feed costs or discounting of heavy lambs, genetic trends in WW were reduced by approximately 50% to constrain increases in YW. Changes in EPD for MM or fleece traits generally had smaller effects on profitability than changes in PLC, WW, and YW. Two indexes designed to address current rangeland production conditions (low forage costs and discounting of heavy feeder lambs) or more intensive and integrated production with retained ownership and value-based marketing of lambs (higher forage costs and no discounting of heavy lambs) were anticipated to meet the needs of most Targhee producers.     

The physical size of gestating sows

Two hundred ninety-six gestating sows were used to determine the physical dimensions of sows in commercial settings. Sows were examined from five farms within a single production model that included identical feed formulation, management practices, herd health, and similar, but not identical, genotypes. Sows were individually weighed, backfat thickness was determined by ultrasound, and body dimensions were determined. Sow body length, height, width (lateral length, left to right from mid-line), and depth (measured as distance from ventral to dorsal extremes) were also determined. Regression procedures were used to model the changes in sow body size in relation to parity, BW, and stage of gestation within and among genotypes. Farm-to-farm variation in sow dimensions for the same genotype was also determined. Least squares means, SD, and 95% upper confidence limits of this sample are presented. Sows increased (P < 0.001) in body dimensions by predicable levels with parity (r2 = 0.92) up to Parity 6, and with advancing pregnancy (r2 = 0.99). Sows of different but related genotypes differed (P < 0.01) in body length, width, height, and depth. Sows of the same genotype, fed the same feed formulation, differed in body dimensions when managed on different farms. Based on mean values and a 95% confidence interval, stall width would need to be at least 72.4 cm to accommodate all sows on the farm. These data and models can be used to design stall sizes and farm floor space needs to meet current animal welfare recommendations. To accommodate the body size of pregnant sows on commercial farms, stall sizes for the majority of sows would need to increase, as would the total floor space needed for a given number of gestating sows individually penned in conventional production systems to meet recently published guidelines.     

Effects of Alternative Molting Programs and Population on Layer Performance: Results of the Thirty-Fifth North Carolina Layer Performance and Management Test

A study involving 7 white-egg and 3 brown-egg commercial layer strains was conducted at the North Carolina Piedmont Research Station to assess the effects cage population 3-bird vs. 4-bird cages and alternative molt programs on performance through 113 wk of age (791 d). The flock was divided into 3 groups; not molted (NM), maintained in continuous production; molted using feed restriction (FR), an industry-type 14-d feed withdrawal molting program initiated at 463 d of age; and molted using a nonfasted/anorexic program (NF), in which an ad libitum supply of a low protein, low energy molt feed was provided. Productivity, egg size, and egg quality were monitored at 28-d periods throughout the test providing the performance data for the white-egg and brown-egg strains with regard to these management factors. Detailed results by strain are available on the following Web site: http://www.ces.ncsu.edu/depts/poulsci/tech_info.html#layer. The performance for the 3-bird or 4-bird cage groups for either type of layer was similar, except that birds in 4-bird cages had higher feed consumption in the first production phase than did the birds in 3-bird cages. In the same time period the white-egg birds in the 3-bird cages had a greater percentage of cracked eggs and a smaller percentage of Grade A large eggs than those in 4-bird cages. No differences were observed in egg income for the 2 population sizes for either type of layer. However, due to their higher feed consumption, the white egg birds in the 4-bird cages had higher feed cost per hen for the first cycle, which was offset by the egg income component due to their increased production rate. The molted layers outperformed the nonmolted layers for both types of layers in terms of overall income over feed costs. The FR molted hens, under a program that has traditionally been used by commercial producers, outperformed NF-molted hens, indicating that further refinements are needed to make the NF program economically competitive with the FR molting program.     

Effects of toxic and non‐toxic blue mussel meal on health and product quality of laying hens

Blue mussels (Mytilus edulis) are a potential protein source in poultry feeds because of their high methionine and cystein content. However, mussels may temporarily be contaminated with the toxin, okadaic acid. The aim of this small scale study was to evaluate the effects on animal health and morphology of the digestive tract of laying hens fed three different diets; a commercial feed and diets containing 15% normal or 15% toxic mussel meal, i.e. a concentration of 198.6 μg toxin per kg feed. Twelve laying hens were divided into six groups and fed the experimental diets for 8 weeks. Animal health, production performance and egg quality were recorded. At sacrifice, tissue samples were prepared for histological evaluation using light microscopy. Okadaic acid did not have any adverse effects on animal health or production parameters and no histological changes indicating disturbances in the digestive tract was observed. Internal egg quality was improved as eggs from hens fed either of the two mussel meal diets had an increased yolk colour. These results show that mussel meal functions as a novel protein source for laying hens and those toxic mussels at this level may be included in the feed without negative effects on parameters evaluated in this study.     

Effects of dietary protein/energy ratio on growth performance,carcass trait,meat quality,and plasma metabolites in pigs of different genotypes

Background:The protein/energy ratio is important for the production performance and utilization of available feed resources by animals.Increased protein consumption by mammals leads to elevated feed costs and increased nitrogen release into the environment.This study aimed to evaluate the effects of dietary protein/energy ratio on the growth performance,carcass traits,meat quality,and plasma metabolites of pigs of different genotypes.Methods:Bama mini-pigs and Landrace pigs were randomly assigned to two dietary treatment groups(Chinese conventional diet with low protein/energy ratio or National Research Council diet with high protein/energy ratio;n = 24 per treatment) in a 2x2 factorial arrangement.Blood and muscle samples were collected at the end of the nursery,growing,and finishing phases.Results:We observed significant interactions(P 0.05) between breed and diet for total fat percentage,intramuscular fat(IMF) content,protein content in biceps femoris(BF) muscle,and plasma urea nitrogen(UN) concentration in the nursery phase;for average daily gain(ADG),average daily feed intake(ADFI),dry matter,IMF content in psoas major(PM) muscle,and plasma total protein and albumin concentrations in the growing phase;and for drip loss and plasma UN concentration in the finishing phase.Breed influenced(P 0.05) growth performance,carcass traits,and meat quality,but not plasma metabolites.Throughout the trial,Landrace pigs showed significantly higher(P 0.05) ADG,ADFI,dressing percentage,lean mass rate,and loin-eye area than did Bama mini-pigs,but significantly lower(P 0.05)feed/gain ratio,fat percentage,backfat thickness,and IMF content.Dietary protein/energy ratio influenced the pH value,chemical composition of BF and PM muscles,and plasma activities of glutamic-pyruvic transaminase and gamma-glutamyl transpeptidase,and plasma concentration of UN.Conclusions:Compared with Landrace pigs,Bama mini-pigs showed slower growth and lower carcass performance,but had better meat quality.Moreover,unlike Landrace pigs,the dietary protein/energy ratio did not affect the growth performance of Bama mini-pigs.These results suggest that,in swine production,low dietary protein/energy ratio may be useful for reducing feed costs and minimizing the adverse effects of ammonia release into the environment.     

Bioeconomic evaluation of embryo transfer in beef production systems: I. Description of a biological model for steer production.

Concepts used to derive a deterministic model for evaluating embryo transfer for commercial steer production taking into consideration genetic merit for growth and mature size, herd feed supply, and recipient maternal environment are discussed. Genetic potential of an embryo is used to derive optimal growth rates that can be sustained by available herd feed per animal per day. Equations are provided for various measures of performance as functions of the feed, genotype of the embryo, and recipient maternal contribution. To assess the value of a particular line of embryos, interactions between genotype and nutrient environment are quantified, so that the benefits of embryos of high genetic merit are evaluated objectively. Product quality and weight are predicted from the model to provide a framework that will allow commercial beef producers to determine marketing strategies likely to result in optimal return.     

不同季节条件下笼养与平养蛋鸭生产性能的比较分析

本试验以山麻鸭为研究对象,比较分析在不同季节条件下笼养与平养蛋鸭生产性能的差异,以筛选出不同季节条件下蛋鸭适宜的饲养方式.结果表明,春季,平养组的产蛋率与总蛋重极显著高于笼养组(P<0.01),而平养组的料蛋比和畸形蛋率极显著低于笼养组(P<0.01);夏季,笼养组的产蛋率显著高于平养组(P<0.05),而笼养组的畸形蛋率极显著低于平养组(P<0.01),但笼养组的总蛋重与料蛋比与平养组相比差异不显著(P>0.05);秋季,笼养组的产蛋率极显著高于平养组(P<0.01),而笼养组的料蛋比显著低于平养组(P<0.05),但笼养组的总蛋重与畸形蛋率与平养组相比差异不显著(P>0.05);冬季,平养组的产蛋率和总蛋重分别显著和极显著高于笼养组(P<0.05;P<0.01),而平养组的畸形蛋率极显著低于笼养组(P<0.01),但平养组的料蛋比与笼养组相比差异不显著(P>0.05).由此可知,在春、冬季节对山麻鸭采用平养方式,可提高蛋鸭的产蛋性能;夏、秋季节对山麻鸭采用笼养方式,有利于蛋鸭生产性能的发挥.     

Effect of dietary supplementation with vitamin C or carbadox on weanling pigs subjected to crowding stress

A 2 X 3 factorial arrangement was used in each of two trials with two levels of floor space allowance (.25, .13 m2/pig) and three dietary treatments (basal, basal + 660 ppm vitamin C, basal + 55 ppm carbadox). The reduction in floor space allowance was achieved in trial 1 by doubling the number of pigs/pen from eight to 16 and in trial 2 by reducing the size of pens by half. An 18% protein starter diet was used as the basal diet. Total numbers of pigs used were 216 in trial 1 and 144 in trial 2. Pigs were weaned between 4 and 5 wk of age (7.5 kg average wt) and fed ad libitum for 28 d. Reducing floor space allowance caused a (P less than .05) reduction in weight gain of weanling pigs in both trials. When the reduction of floor space allowance was done by increasing number of pigs/pen (trial 1), pigs responded with a significantly reduced feed intake with no change in efficiency of feed utilization. However, when floor space allowance was reduced by changing the size of the pen (trial 2), feed intake of pigs was not affected but efficiency of feed utilization was reduced significantly. Neither form of crowding affected vitamin C concentration in adrenal glands and weights of adrenal glands, spleen and thymus. Dietary supplementation of carbadox, but not vitamin C, produced significantly greater weight gain, feed efficiency, and spleen weight of pigs in both trials. Although there was no interaction between crowding and dietary treatment in affecting the performance of pigs, supplemental carbadox improved the performance of crowding-stressed pigs by maintaining an adequate level of feed intake and improving feed efficiency, whether crowding was caused by increased pig density or by reduced pen size. No significant differences in phytohemagglutinin (PHA) skin test response or in the neutrophil-to-lymphocyte ratio (N/L) were observed among treatments in trial 1, while a significantly reduced response to PHA and a higher N/L were detected in crowding-stressed pigs in trial 2.     

Correlated responses in sow appetite, residual feed intake, body composition, and reproduction after divergent selection for residual feed intake in the growing pig

Residual feed intake (RFI) has been explored as an alternative selection criterion to feed conversion ratio to capture the fraction of feed intake not explained by expected production and maintenance requirements. Selection experiments have found that low RFI in the growing pig is genetically correlated with reduced fatness and feed intake. Selection for feed conversion ratio also reduces sow appetite and fatness, which, together with increased prolificacy, has been seen as a hindrance for sow lifetime performance. The aims of our study were to derive equations for sow RFI during lactation (SRFI) and to evaluate the effect of selection for RFI during growth on sow traits during lactation. Data were obtained on 2 divergent lines selected for 7 generations for low and high RFI during growth in purebred Large Whites. The RFI was measured on candidates for selection (1,065 pigs), and sow performance data were available for 480 sows having from 1 to 3 parities (1,071 parities). Traits measured were sow daily feed intake (SDFI); sow BW and body composition before farrowing and at weaning (28.4 ± 1.7d); number of piglets born total, born alive, and surviving at weaning; and litter weight, average piglet BW, and within-litter SD of piglet BW at birth, 21 d of age (when creep feeding was available), and weaning. Sow RFI was defined as the difference between observed SDFI and SDFI predicted for sow maintenance and production. Daily production requirements were quantified by litter size and daily litter BW gain as well as daily changes in sow body reserves. The SRFI represented 24% of the phenotypic variability of SDFI. Heritability estimates for RFI and SRFI were both 0.14. The genetic correlation between RFI and SRFI was 0.29 ± 0.23. Genetic correlations of RFI with sow traits were low to moderate, consistent with responses to selection; selection for low RFI during growth reduced SDFI and increased number of piglets and litter growth, but also increased mobilization of body reserves. No effect on rebreeding performance was found. Metabolic changes previously observed during growth in response to selection might explain part of the better efficiency of the low-RFI sows, decreasing basal metabolism and favoring rapid allocation of resources to lactation. We propose to consider SRFI as an alternative to SDFI to select for efficient sows with reduced input demands during lactation.     

Efficacy of Montmorillonite Clay (NovaSil PLUS) for Protecting Full-Term Broilers from Aflatoxicosis

Contamination of poultry feeds by aflatoxin is a problem faced by poultry producers at one time or another. Of the several strategies used to reduce the economic effect of aflatoxin-contaminated feeds, the inclusion of selective enterosorbents may be the most practical and cost effective. This study evaluated the effectiveness of montmorillonite clay (MC) supplied as NovaSil PLUS on the performance of full-term commercial type broilers. Eight hundred male commercial broiler chickens (all vaccinated for Marek's disease, Newcastle disease, and bronchitis) were randomly assigned, (20 each) to 40 floor pens and fed 1 of the 4 dietary treatments of industry-type corn-soy broiler diets. Treatments consisted of a control feed, control feed plus 0.5% MC (CMC), a feed containing ˜4,000 ppb aflatoxin (AF), and a feed containing ˜4,000 ppb aflatoxin plus 0.5% MC (AMC). The starter diet was fed for 3 wk, the grower for 2 wk and, the finisher for 1 wk. Selected birds were randomly retained for specific tissue analyses of blood serum; relative liver, spleen, and kidney weights; and histological examination of sampled organs.The combined data showed that birds fed MC as NovaSil PLUS received significant protection against the effects of the aflatoxin for most parameters measured. This level of protection did not totally protect the birds from the effects of feeding extremely high concentrations of aflatoxin, however, as their performance was not as good as that of the control group. To our knowledge this is the first study addressing the protective effects of MC in full-term broilers fed steam-pelleted feeds more nearly approximating commercial production.     

Effect of sequential implanting with zeranol on steer lifetime performance

Three trials involving 513 exotic crossbred steers were conducted to determine the effect of zeranol implanting in the suckling and growing phases on subsequent feedlot performance and carcass characteristics. Treatments were 1) unimplanted control, 0000; 2) implanted twice in the finishing phase, 00II; 3) implanted in the growing phase and twice in the finishing phase, 0III; 4) implanted in the suckling phase and twice in the finishing phase, I0II; 5) implanted in the suckling and growing phases with a single implant in the finishing phase, III0; and 6) implanted in the suckling and growing phases and twice in the finishing phase, IIII. Implanting in the suckling period did not significantly affect preweaning gain. Implanting in the growing period produced a treatment x trial interaction (P less than .05), but zeranol increased gains by an average of 8.4% over the three trials. Growing period gain was not influenced by implanting during suckling. Implanting twice during the finishing period increased gain (P less than .05) over unimplanted and III0 steers. Finishing gain was not influenced by previous suckling and(or) growing implant treatment. Lifetime ADG of steers was increased (P less than .05) by all implant treatments compared with unimplanted controls. Zeranol tended (P = .14) to improve feed conversion in the finishing phase. All implant treatments increased hot carcass weight (P less than .05), and all but III0 reduced fat deposition, as indicated by lower quality grade (P less than .05). Other carcass characteristics were not significantly affected by treatment. These trials demonstrated that implanting in the suckling and(or) growing phases of production did not reduce performance in the finishing phase.     

低蛋白低磷加酶日粮对生长猪生产性能及减排效果的影响

选择30头24.4kg左右的健康杜×长×大杂交猪,将其随机分成2组,每组3个重复,每个重复5头猪,分别饲喂两种日粮：对照组日粮（18.4%CP＋0.37%有效磷,高蛋白高磷组日粮）和试验组日粮（16.0%CP＋0.28%有效磷＋100g/t植酸酶,低蛋白低磷加酶组日粮）,研究低蛋白低磷加酶日粮对生长猪生产性能及减排效果的影响。结果表明,低蛋白低磷加酶日粮对生长猪生产性能没有显著影响,但是可显著提高氮、磷的利用率,从而减少氮、磷排放。