Net protein and metabolizable protein requirements for maintenance and growth of early-weaned Dorper crossbred male lambs

Background: Dorper is an important breed for meat purpose and widely used in the livestock industry of the world.However, the protein requirement of Dorper crossbred has not been investigated. The current paper reports the net protein(NP) and metabolizable protein(MP) requirements of Dorper crossbred ram lambs from 20 to 35 kg BW.Methods: Thirty-five Dorper × thin-tailed Han crossbred lambs weaned at approximately 50 d of age(20.3 ± 2.15 kg of BW) were used. Seven lambs of 25 kg BW were slaughtered as the baseline animals at the start of the trial. An intermediate group of seven randomly selected lambs fed ad libitum was slaughtered at 28.6 kg BW. The remaining 21 lambs were randomly divided into three levels of dry matter intake: ad libitum or 70% or 40% of ad libitum intake. Those lambs were slaughtered when the lambs fed ad libitum reached 35 kg BW. Total body N and N retention were measured.Results: The daily NP and MP requirements for maintenance were 1.89 and 4.52 g/kg metabolic shrunk BW(SBW0.75).The partial efficiency of MP utilization for maintenance was 0.42. The NP requirement for growth ranged from 12.1 to 43.5 g/d, for the lambs gaining 100 to 350 g/d, and the partial efficiency of MP utilization for growth was 0.86.Conclusions: The NP and MP requirements for the maintenance and growth of Dorper crossbred male lambs were lower than the recommendations of American and British nutritional systems.     

Breed group differences in testicular growth patterns in spring-born ram lambs

Three groups of spring-born ram lambs were used to assess breed group differences in testicular growth patterns through 5 mo of age. Group 1 included 20 3/4-Finnish Landrace (Finn), 1/4-Rambouillet rams and 31 1/8-Finn, 7/8-Rambouillet rams. Group 2 included 23 3/4-Finn, 1/4-Dorset rams and 19 1/8-Finn, 7/8-Dorset rams. Group 3 included 21 black-faced (BF) rams (six Hampshire and 15 Suffolk) and 46 whitefaced (WF) rams (nine Dorset, 20 Barbados Blackbelly X Dorset, 10 Finn X Dorset and six Dorset X Finn). Scrotal circumference (C) was measured at 19, 43, 72, 100, 128 and 153 d in Group 1; at 20, 48, 76, 93 and 153 d in Group 2 and at 40, 60, 81, 103, 124 and 158 d in Group 3. Breed group X age interaction was tested to assess breed group differences in testicular growth patterns, and logistic curves were used to describe increases in scrotal circumference with age. In Group 1, 3/4-Finn and 1/8-Finn rams were similar in estimated final scrotal circumference at 150 d of age (260 and 259 mm, respectively), but rapid testicular growth began earlier in 3/4-Finn rams. The estimated age at which the growth rate in scrotal circumference was maximum was 81 d for 3/4-Finn rams and 93 d for 1/8-Finn rams. No differences were observed in testicular growth in Group 2 rams. However, in Group 3, smaller WF rams matured more rapidly than larger BF rams. Growth in scrotal circumference was most rapid at 99 d in BF rams and 88 d in WF rams. Within WF rams, Barbados Blackbelly X Dorset and Finn X Dorset rams matured earlier than Dorsets. In all groups, the primary breed difference was associated with age differences during the period of rapid testicular growth.     

Genetic correlations for daily gain between ram and ewe lambs fed in feedlot conditions and ram lambs fed in Pinpointer units

When performance is recorded in automated facilities that measure feed intake of individual lambs that are penned in a group, such as Pinpointer units, a legitimate question is the degree to which daily gain is genetically correlated with daily gain achieved under feedlot conditions. Lambs were from a composite population (1/2 Columbia, 1/4 Suffolk, and 1/4 Hampshire germplasm) and of the F2 or more advanced generations. Data were daily gains of 1,101 rams (PR) fed in Pinpointer units (11 to 17 wk of age) and 2,021 rams (FR) and 3,513 ewes (FE) fed under feedlot conditions (9- or 10-wk period starting at 9 wk of age). The FR and FE lambs were born from 1983 through 1995, whereas the PR lambs were born from 1986 through 1995. Measurements of daily gain in PR, FR, and FE lambs were considered to represent three correlated traits. Unadjusted means were .411, .406, and .326 kg/d for PR, FR, and FE, respectively. Random effects in the model were animal direct genetic, maternal genetic, and maternal permanent environmental. Fixed effects were associated with age of dam (1 to 6 yr), type of rearing (1 to 4), and contemporary group (test date). Variances due to maternal genetic effects with single-trait analyses were near zero, so those effects were eliminated from the three-trait analysis although a random uncorrelated effect due to dam was included in the model. Estimates of heritability were .22, .14, and .23 for PR, FR, and FE, respectively, with fractions of variance due to dam effects ranging from .02 to .05. Estimates of genetic correlations were .86 for PR with FR, .83 for PR with FE, and 1.00 for FR with FE. Estimated phenotypic variances were similar for PR and FR, but one-third less for FE. The similarity of heritability estimates and estimates of genetic correlations all exceeding .83 suggest that daily gain of rams fed in Pinpointer units will reflect genetic expression for daily gain in both ram and ewe lambs fed under feedlot conditions.     

Effects of breed and intake level on growth and feed efficiency in ram lambs

Effects of breed and intake level on growth and feed efficiency in ram lambs were tested with 52 Rambouillet, 46 Dorset and 53 Finnish Landrace (Finn) rams. Rams were individually fed at 100, 85 or 70% of ad libitum or at maintenance. The experimental diet contained 79% digestible dry matter (DM), 3.28% N and 2.95 Mcal metabolizable energy/kg DM. Rams were serially slaughtered every 35 d for 175 d. The efficiency of deposition of body weight, protein, energy and trimmed cuts was determined by breed and intake level over constant time, weight, fat and maturity intervals. Ranking of the breeds for feed efficiency depended upon both the interval and the criterion of evaluation. Efficiency of protein and trimmed cut gain was positively related to mature size in the time and weight intervals, but all differences in efficiency were small in the fat or maturity intervals. Gross energetic efficiency did not differ greatly among breeds in any interval. Dorsets appeared to have a somewhat greater propensity to fatten than the other breeds and to be less able to retain N at a fixed N intake. In the constant time interval, maintenance requirements were estimated to be 115 kcal/kg.75, and the estimated partial efficiencies of energy deposition in fat and protein were .49 and .26, respectively.     

Copper toxicity in confinement-housed ram lambs.

Fourteen Suffolk rams (6 mo) were diagnosed with chronic copper poisoning. Preliminary results indicated that a combination of serum aspartate aminotransferase, gamma glutamyltransferase, and copper could be used as a test so that high risk lambs could be treated more aggressively.     

Free ferulic acid uptake in ram lambs

The objective of this research was to investigate the fate of free ferulic acid (FA) in sheep. Ferulic acid is normally present in plants, bound to the indigestible cell wall. If the FA present in a ruminant diet is released from the cell wall with feed pretreatment methods, FA may be released into the rumen for digestion or absorption into the bloodstream or both. Eight male Dorset × Finn lambs were randomly assigned to 1 of 4 treatment (trt) concentrations, 0 (control), 3, 6, or 9 g/d free FA as part of a replicated 4 × 4 Latin square design. Lambs were housed individually and consumed chopped alfalfa hay (Medicago sativa; 22.8% CP, 39.3% NDF, 0.73 Mcal/kg NE(g)) ad libitum and 350 g corn grain (Zea mays L.; 9.1% CP, 11.2% NDF, 1.52 Mcal/kg NE(g)) once daily at 0800 h. Basal concentrations of FA in hay, grain, blood, feces, and urine were established following a 14-d adjustment to diet and housing. An oral dose of free FA was administered for 5 d via bolus after each morning feeding, after which hay, grain, blood, feces, and urine were sampled. Body weights were recorded at the beginning and end of each trt, and DMI was measured daily during trt periods. In addition to trt, each lamb ingested a daily average of 3.78 g FA in its bound form via the offered hay (2.67 mg/g FA; 1.0 kg/d DMI) and corn (3.17 mg/g FA; 0.35 kg/d DMI). The FA administered had a quadratic effect on average hay DMI (1.25, 1.41, 1.41, and 1.29 kg/d for 0, 3, 6, or 9 g/d FA trt; P < 0.01; SE = 58.9 g), but lamb BW did not change as a result of FA trt (P = 0.28). The NDF content and amount of FA in refusals were not affected by trt, (P = 0.30; P = 0.82, respectively). Fecal FA did not differ among trt or when compared with basal FA (P = 0.53), while urine FA increased as FA dose increased (P < 0.01), indicating that free FA was absorbed and transferred into urine. No free FA was found in the plasma analyzed, suggesting that disappearance from the blood of absorbed free FA occurred within the 5 h that passed between bolus dosage and blood collection. An in vitro analysis was conducted to assess the degree of inhibition of microbial NDF digestion caused by FA supplementation. In vitro, NDF disappearance was not inhibited as a result of FA treatment (P = 0.80). These data in combination with the results of the lamb study indicate that free FA as 0.24, 0.43, and 0.70% of DMI in lambs is absorbed and excreted in the urine as opposed to the feces with no apparent effects on rumen microbial NDF digestion.     

Progeny test of ram lambs selected for low ultrasonic backfat thickness or high post-weaning growth rate

Ram lambs were selected from a total of 1206 lambs in 8 industry Coopworth ram breeding flocks. Eight rams were selected randomly (one from each flock), 8 were selected on the basis of a low live weight-adjusted ultrasonic backfat thickness (lean) and 8 for a high post-weaning growth rate (PW gain). Rams from a Coopworth line specially selected and bred for low ultrasonic backfat (lean selection) were also included in the progeny test in which the rams were single sire mated to 1.5 year old Coopworth ewes. Birth and weaning weights were recorded for a total of 474 female and 371 male progeny. The males (progeny of 31 sires) were slaughtered between January and April at an average hot carcass weight (HCW) of 12.56 kg and carcass growth and carcass fatness parameters recorded. The carcass composition data were analysed using the allometric equation by covariance on HCW. The adjusted mean values of carcass water content were significantly higher for the progeny of the lean selection rams (7.58 kg) than forthe other 3 sire classes (7.49, 7.46 and 7.41 for the lean, PW gain and controls respectively) indicating that they were leaner. Other indicators of carcass fatness also revealed marked differences between the sire classes. There were also marked effects of slaughter date with lambs slaughtered earlier being leaner (after adjustment for HCW) than lambs slaughtered later in the season. The results indicate that selection of sires on the basis of ultrasonic backfat thickness or post weaning live weight gain can be expected to result in the production of leaner lamb carcasses.     

The physiological effects of natural variation in growth hormone gene copy number in ram lambs

The effects of natural variation in the number of copies of the growth hormone (GH) gene on growth parameters, plasma GH profiles, and the response to GHRH challenge were compared in Coopworth ram lambs from selection lines differing in body composition and GH levels. Different genotypes at the GH locus carried two, three, or four copies of the GH gene and GH secretion was studied under ad libitum feeding conditions and in the fasted state. There were no significant effects of GH genotype on any parameters of growth or body composition. Basal serum GH concentration, GH pulse frequency, and GH pulse amplitude differed significantly with selection line and fasting, but did not differ significantly between the GH genotypes. Significant differences of subtle nature were found between the GH genotypes in their responsiveness to GHRH. For the ad libitum-fed Lean selection line animals, the first GHRH challenge resulted in a higher mean maximum response for GH1/GH1 than GH2/GH2 (P < 0.05). Between the first and the second challenges there was a decrease in maximum response for the GH1/GH1 genotype and an increase for the GH2/GH2 genotype (P < 0.05 for GH genotype main effect). The differences between GH genotypes in response to GHRH challenge suggest that polymorphism in the number of GH gene copies in sheep may have physiological implications for the function of the GH axis, which may be manifested in growing lambs only under specific genotype-environment combinations.     

Puberty and early sexual development in Libyan fat-tailed ram lambs

Puberty and early sexual development were studied in 143 Libyan fat-tailed ram lambs, equally representing Brownhead and Blackhead strains of this breed. The two strains did not differ in any of the measured parameters in a consistent way, yet the Brownhead lambs tended to be slightly heavier and to have a slightly larger testis diameter than Blackheads. At the commencement of the observations when the lambs were 69 days old, 25.2% had fully descended testes at a significantly higher (P less than 0.01) mean (SD) body weight (24.1 +/- 4.1 kg) than those with partly descended (69.2%, 15.7 +/- 6.3 kg) or with non-descended testes (5.6%, 19.5 +/- 3.2 kg). Testes development followed a triphasic pattern with an initial and a final phase of slow growth and a middle phase of fast growth, commencing at a weight of 24.5 kg and an age of 85 days and lasting until the weight of 36-43 kg and age of 180-200 days in both strains. The separation of penile adhesions commenced at a mean body weight and age of 33.6 +/- 3.7 kg and 125.5 +/- 27.4 days respectively and was completed at a mean weight and age of 38.3 +/- 4.2 kg and 153.4 +/- 29.9 days. Only four lambs failed to show complete penile separation. Age had little influence on testis descent or on penile development. Puberty was assessed in 71 lambs using sperm recovery following electroejaculation as an end point. Most of these lambs (92.9%) reached puberty at a mean (SD) age of 171.5 (39.9) days, mean body weight of 39.9 (9.3) kg, mean testis diameter of 4.1 (0.4) cm and mean horn length of 21.4 (3.7) cm. Puberal lambs were significantly superior to non-puberal lambs (P less than 0.01) in all these counts except for age which was similar in both categories. Direct testicular observation showed a strong correlation between testis diameter, testis weight, body weight, sperm concentration/g testis weight and to testis histology. Age was poorly correlated to testis weight, histology or sperm concentration. It is concluded that the body weight is a major determinant of puberty in this breed. It is also considered that the two strains of the breed are remarkably similar in the studied aspects of puberty and sexual development.     

Evaluating a novel analgesic strategy for ring castration of ram lambs

Objective To evaluate the analgesic efficacy of the NSAIDs flunixin and meloxicam administered locally to the scrotum before ring castration. Study design Randomised, controlled, prospective study. Animals Forty eight single born male Merino lambs. Methods Lambs, aged approximately 4 weeks, were allocated to four groups for castration. Groups were: sham control; castration + saline; castration + flunixin; castration + meloxicam. Drugs (5 mL) were administered subcutaneously around the circumference of the scrotum immediately before castration. Cortisol, rectal temperature, haematology and plasma haptoglobin were measured before and up to 48 hours after treatment. Behaviour recorded by video for 12 hours after treatment was classified as pain avoidance behaviours in the first hour and postural behaviours in three 4 hour intervals. Results Ring castration (saline group) induced a bi‐phasic increase in cortisol with peaks at 90 minutes and 24 hours but no significant changes in haematology, haptoglobin or rectal temperature. Pain avoidance behaviours were increased and teat seeking decreased. Normal lying and normal standing postures were decreased and abnormal ventral lying, statue standing, abnormal standing and total abnormal postures increased. Flunixin decreased cortisol at 90 minutes (60.3 versus 117.3 nmol L^?1) and cortisol AUC (0–6 hours), decreased elevated leg movement (2.5 versus 5.4 events) and sum of pain avoidance behaviours (8.5 versus 16.7 events), improved time spent in normal ventral lying and decreased abnormal ventral lying and total abnormal postures compared to saline treated lambs. In a similar contrast, meloxicam caused non‐significant decreases in cortisol at 90 minutes, cortisol AUC (0–6 hours) and pain avoidance behaviours, and significantly improved the postural behaviours normal ventral lying (26.7 versus 15.4%) and normal standing (13.9 versus 7.5%), and reduced abnormal standing and total abnormal postures. Physiological and behavioural responses associated with ring castration for both NSAID treatment groups were generally greater than sham controls. Conclusions and clinical relevance Locally administered NSAIDs provided partial analgesia for ring castration.     

Relationship between LH and testicular development in progesterone-implanted prepubertal ram lambs

The relationship between systemic luteinizing hormone (LH) and testicular development was investigated in Finn and Suffolk ram lambs treated at 2 wk of age with sc progesterone implants for 0, 4, 8 or 12 wk. Serial samples of blood (30-min intervals for 3 h) were collected from five rams X breed-1 X treatment-1 at 6, 8, 10, 12, 14, 18 and 22 wk of age plus 1 and 2 wk after implant removal. Scrotal circumference was measured at 10, 14, 18 and 22 wk of age. A testicular biopsy was obtained at 14, 18 and 22 wk for microscopic evaluation of testicular development and spermatogenesis. Pulsatile LH releases occurred 60 to 180 min apart in control lambs between 6 and 22 wk of age; LH secretion was not affected by age except for a decrease (P less than .01) in mean LH at 22 wk. Transient increases in testosterone were found subsequent to LH pulses. Systemic testosterone increased (P less than .01) progressively with age, was higher (P less than .05) in Finn than in Suffolk rams at 18 and 22 wk and was correlated positively (P less than .01) within breeds with seminiferous tubule diameter at 14 wk and with scrotal circumference at 10 and 14 wk. Tubule diameter was larger (P less than .01) but testes size and weight were smaller (P less than .01) in Finn than in Suffolk rams. Progesterone implants decreased (P less than .01) LH secretion at 4, 6, 8, 10 and 12, but not at 14 wk of age; decreased systemic testosterone between 4 and 14 wk; decreased (P less than .01) seminiferous tubule diameter at 14 wk, which was related inversely to duration of progesterone treatment; and delayed puberty from 18 to 22 or more wk in rams implanted from 2 to 10 or 14 wk of age. Both control and treated rams with elongated spermatids at 18 vs 22 or more wk had increased LH secretion, higher systemic testosterone and larger tubule diameter and testes size at a younger age. These results suggest that rate of sexual maturation in ram lambs is related to level of postnatal LH stimulation and to the prepubertal age when increased LH stimulation occurs.     

Growth hormone, insulin, prolactin and glucose levels in ewe and ram lambs during normal and compensatory growth

Two trials were conducted to determine the effect of compensatory growth on plasma glucose and serum growth hormone (GH), prolactin (PRL) and insulin concentrations in lambs. The trials consisted of a normal growth (NG) period (4 to 7 mo of age), a restricted feed/weight loss period and a compensatory growth (CG) period. The lambs in Trial 1 were 13 mo of age and in Trial 2, 11 mo of age at the start of the respective CG periods. Compensatory growth rate was 61 to 67% greater than NG rate in Trial 1 and 2, respectively. Twenty-four hour blood collections were performed during NG and CG in each trial. Normal growth blood collection for Trial 1 was performed in April (ram, n = 7; ewe, n = 6) and the CG blood collection in November (ram, n = 6; ewe, n = 6) while for Trial 2 blood collection dates were November (ram, n = 6; ewe n = 6) and March (ram, n = 4; ewe, n = 5). Trial 1 ram lambs had lower plasma glucose concentrations during CG than during NG while plasma glucose concentration was not altered in ewe lambs. Type of growth had no effect on plasma glucose in Trial 2. There was a type of growth by sex interaction for insulin in both Trial 1 and Trial 2. Insulin concentration decreased during CG in ram lambs but remained unchanged (Trial 1) or increased in ewe lambs (Trial 2) during CG. The effect of CG on PRL concentration in Trial 1 was confounded by photoperiod and the only effect in Trial 2 was a small decrease in the amplitude of PRL peaks during CG. The overall mean GH concentration (GHmn) was increased (P less than 0.01) two fold during CG in Trial 1. This effect was also seen in Trial 2 but the increase was sex dependent (P less than 0.005) with the effect of CG on GHmn in ram lambs being six times that seen in ewe lambs. The GH profile characteristics responsible for the increase in GHmn during CG differed between sexes and trials.     

Carcass characteristics of Awassi ram lambs slaughtered at different weights

Thirty Awassi ram lambs were used to study the effects of slaughter weight on carcass characteristics. Lambs were slaughtered at three different live weights (20, 30, and 40 kg). Empty body weight, hot and cold carcass weights and non-carcass components increased (P < 0.001) at a steady rate between all slaughter weights. Body length, leg length, maximum shoulder width, width behind shoulders and gigot width increased (P < 0.001) as slaughter weight increased from 20 to 40 kg. Linear dimensions measured on the surface of the M. Longissimus also increased (P < 0.001) with increasing slaughter weight. The ratio between width and depth of the longissimus muscle decreased (P < 0.01) at a steady rate between 20 and 40 kg indicating that the muscle increased more in depth than width. Dressing-out percentage was higher (P < 0.001) for lambs slaughtered at 30 kg live weight compared to other weights. Total lean and total bone decreased (P < 0.05) as a percent of cold carcass weight while total fat, subcutaneous and intermuscular fat percentages increased (P < 0.05) with increasing weight. Subcutaneous fat percentage was not affected by increasing body weight between 20 and 30 kg. Intermuscular fat percent was higher in all cuts except the leg where subcutaneous fat % was higher. Muscle to bone ratio increased (P < 0.001) while muscle to fat ratio decreased (P < 0.001) with increasing body weight in the four major cuts and the whole carcass. In conclusion, slaughtering Awassi ram lambs at weights up to 30 kg resulted in higher dressing-out percentage and better carcass characteristics than ram lambs slaughtered at heavier weights.     

Factors affecting productivity of Rambouillet ewes mated to ram lambs

Objectives of this study were to estimate the magnitude of the effects of various factors associated with ewes and their ram lamb mates on fertility, prolificacy, lamb survival, lamb weaning weight and ewe productivity and to estimate the heritability and repeatability of each trait. Records from 731 ewe-years, 75 ram lamb sires and 616 lambs born from the University of Illinois Rambouillet flock were used. Ewes mated to single-born ram lambs had higher fertility rates (P less than .01), gave birth to lambs with higher survival rates (P less than .01), weaned lighter (P less than .05) individual lambs but weaned more weight of lamb per ewe exposed (P less than .01) than ewes mated to multiple-born ram lambs. Ram lamb breeding weight, ram lamb scrotal circumference, ewe breeding weight and ewe age had relatively large and positive effects on the composite trait of weight of lamb weaned per ewe exposed and significant effects on a number of the component traits. Heritability and repeatability estimates were, respectively, as follows: fertility, 3%, 3%; prolificacy, 34%, 19%; lamb survival, 15%, 8%; lamb weaning weight, 7%, 36%; and ewe productivity, 27%, 10%.     

Endocrine profiles, testicular gonadotropin receptors and sperm production in hemi-castrated ram lambs

The effects of hemi-castration upon compensatory hypertrophy, serum gonadotropin and testosterone concentrations, testicular gonadotropin receptors and daily sperm production (DSP) were studied in 10 crossbred ram lambs. At 4 mo of age lambs were either hemi-castrated (HC; n = 5) or left intact (INT; n = 5). Blood samples were collected every 2 h for the first 24 h post-surgery, every 6 h for the next 24 h and then three times weekly for the following 14 wk. Serial blood samples (15-min intervals for 8 h) were collected during the 4th, 8th and 12th week following hemi-castration. Individual mean testicular and epididymal weights increased (P less than .05) 48 and 33% in HC compared with INT rams, respectively. Serum follicle stimulating hormone (FSH) increased (P less than .05) within 8 h after HC, reached peak concentrations within 1 wk and remained elevated for 4 wk before returning to concentrations of INT rams. Neither mean serum luteinizing hormone (LH) nor pulse patterns of LH or FSH were different (P greater than .05) between these two groups at any period examined. Serum testosterone (T) concentrations were lower (P less than .05) during the first 48 h post-surgery in HC rams, but by 1 wk concentrations were similar (P greater than .05) to those in INT rams. Remaining testes from HC and INT rams were removed at 7 mo of age, 3 mo after initial gonadal manipulation. On a per-testis basis there were more (P less than .05) LH and FSH receptors in HC than INT rams, respectively; however, concentrations of receptors were not different (P greater than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Immune, growth and carcass responses of ram lambs to active immunization against desulfated cholecystokinin (CCK-8)

This study explored feed intake and carcass responses to active immunization against desulfated cholecystokinin-octapeptide (CCK-8) in ram lambs. Antibody titers 8 wk following primary immunization and booster immunizations given at 4 and 6 wk averaged greater than 1:1,000. Titers increased to greater than 1:10,000 by 16 wk following a final booster immunization at 11 wk. The antibodies developed against desulfated CCK-8 exhibited 29% and 13% cross-reactivities for sulfated CCK-8 and gastrin-17, respectively. Immunization against desulfated CCK-8 had no effect on feed intake, ADG, carcass weight or carcass quality grade. Backfat thickness and carcass yield grade were reduced (P less than .05) by immunization. Organ weights at slaughter, including those of the pancreas and small intestines, were not affected by CCK-8 immunization, with the exception of the lungs, which were 16% lighter (P less than .01) in immunized lambs. In conclusion, active immunization against desulfated CCK-8 resulted in development of high antibody titers against desulfated and sulfated CCK-8. Immunization against CCK-8 decreased fat content of the carcass but failed to affect feed intake, carcass weight or ADG.