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Measures of growth and serum Zn concentration were made on young growing pigs receiving a low Zn (20 ppm) basal diet supplemented with 25 or 50 ppm of Zn from either zinc oxide or metallic Zn dust from the metal smelting and refining industry. Growth was not sensitive to either source or level of supplemental Zn, but serum Zn concentration increased linearly with increases in supplemental dietary Zn from either source. Equations for the linear regression of serum Zn concentration on supplemental dietary Zn were calculated from the data on blood samples after 2 and 5 weeks of the trial. The ratio of the slope of the regression line for metallic Zn dust to that for zinc oxide was 1.30 and 1.33 for the 2-week and the 5-week data, respectively. The availability of Zn from this metallic Zn dust to young growing pigs was therefore estimated to be about 30% greater than that from zinc oxide powder.

Two feeding trials were conducted to compare feedlot performance and carcass characteristics when cattle were fed corn silage (HS) or high grain (HG) rations. In trial 1 equal numbers of small (SA) and average framed (AA) Angus, crossbred Chianina (CH), and Holstein (HO) calves were fed HS or HG rations in which supplemental protein requirements were determined by two methods. System 1 (N.R.C.) involved supplementing rations according to National Research Council crude protein recommendations. In System 2 protein supplementation was based on requirements estimated from stage of growth, composition of gain, and estimated growth rate. In trial 2 unselected (UH) and selected Hereford (SH), Charolais × Angus × Hereford crossbred (CAH), and Holstein × Angus × Hereford crossbred (HAH) calves were used to compare HS and HG rations. In trial 2 protein supplementation (System 3) was calculated similarly to System 2, with the exception that estimates of protein utilization efficiency for corn silage and corn grain were lower and higher, respectively, than in System 2.High grain fed cattle, compared to HS cattle, had higher (P<.05) daily carcass gains, fatter carcasses, and lower cutability. Daily protein and fat gains were greater (P<.05) for HG cattle than for HS cattle.Daily carcass, fat, and protein gains were higher (P<.05) with NRC than with System 2 supplementation, but carcass quality and cutability were not influenced by protein system (trial 1). High grain steers used ME 34 and 18% more efficiently than HS steers, respectively, with NRC and System 3 supplementation. In System 2 HG steers were 67% more efficient in use of ME than were HS steers. This suggests a protein × energy level interaction on efficiency of ME utilization.Daily protein gain tended to be greater and daily fat gain less for the larger cattle types compared to average or small framed steers. Only small differences in energetic efficiency were observed among the beef breeds or crosses, but Holsteins were less efficient than beef breeds.

Trace mineral salt supplemented with 0, 30, 65 or 170 ppm selenium (from sodium selenite) was offered ad libitumto ewes and their lambs consuming low-selenium (Michigan) or adequateselenium (North Dakota) diets. Although overt lesions of muscular dystrophy were not observed, the low erythrocyte glutathione peroxidase activities, low plasma selenium concentrations, and elevated plasma creatine phosphokinase activities in Michigan lambs unsupplemented with selenium provided evidence of incipient selenium deficiency. Selenium supplements restored these values to normal. Tissue selenium concentrations were also increased in Michigan lambs, but even the 170 ppm supplement did not produce selenium accretion above that in North Dakota lambs fed diets which were naturally adequate in selenium. Thirty to 65 ppm supplemental selenium in salt proved safe and effective in preventing subclinical selenium deficiency.

Data consisting of 948 calf records collected from 1978 to 1982 were analyzed to determine the effects of breeding methods used to improve commercial herds genetically on birth and weaning traits. Four distinct groups were used in the project: Group 1 (G1), an unselected, random mating Hereford control line; Group 2 (G2), a Hereford group using sires selected for yearling growth; Group 3 (G3), a rotational cross with Angus, Hereford, Charolais and Simmental breeds; and Group 4 (G4), a rotational cross with Angus, Hereford, Simmental and Holstein-Friesian breeds. Traits analyzed were birth weight (BW), calving difficulty (CD), percent assisted births (%AB), percent born alive (%BL), preweaning average daily gain (PWDG), relative growth rate (RGR), weaning weight (WWT) and percent weaned (%WND). The use of high yearling weight sires in G2 increased calf size (P<.01) at birth and weaning by 8.9 and 28.1 kg, respectively, along with increased CD (P<.01). Use of rotational crossbreeding systems increased calf size and growth from birth to weaning (P<.01), but decreased CD and %AB (P<.01) by .17 units and 13.5%, respectively. Including Holstein-Friesian in G4 resulted in further increases in preweaning growth (P<.01) and calving ease was improved without affecting BWT compared with G3.

Differences in total carcass bone, muscle and fat, and linear measurements of the tibia and radius were evaluated in barrows at 105 kg and boars at 105, 118, 132 and 145 kg live body weight. The carcasses of five replicates were physically separated into skin, bone and soft tissues, and the linear measurements of the tibia and radius were obtained on seven replicates. At live weight of 105 kg, boars did not differ significantly in fat-free muscle, but they had 33.2% less fat, 11% greater bone weight and 14% greater skin weight than barrows. At 145 kg, boars had total carcass fat weight comparable with 105-kg barrows. Fat-free muscle, bone and skin weight of boars increased at linear rates of .41, .083 and .104 kg/kg of body weight increase from 105 to 145 kg, respectively. At 105 kg, density and length of the tibia and radius did not differ between boars and barrows. The tibia of boars were heavier than those of barrows at 105 kg, resulting in a greater ratio of tibia weight to length (indirect measure of bone thickness). As boars increased in live weight from 105 to 145 kg, total weight and length of the tibia and radius increased linearly. The ratio of weight to length of the tibia and radius increased during this 40-kg weight gain, indicating that weight of both bones increased at a greater rate than length. These results indicate that boars and barrows have the same weight of total carcass fat when boars are 40 kg heavier than the barrows. The greater bone weight of boar carcasses compared with barrows is due to greater bone thickness.

The rate of gain, carcass measurements and three muscles were evaluated in 65 crossbred boars representing 13 litters that were allotted at 4 wk of age to slaughter weight and treatment groups as follows: 1) 105 kg, castrated; 2) 105 kg, intact; 3) 118 kg, intact; 4) 132 kg, intact and 5) 145 kg, intact. One barrow and four boars within a litter constituted a replicate and each replicate was penned separately. The growth rate of all boars to 105 kg constituted one group and was compared with the growth rate of barrows to 105 kg live body weight. Average daily gain from 4 wk until 105 kg did not differ significantly between boars and barrows. Growth rate of the boars continued at an increasing rate until they reached 87.3 kg live weight, while maximum daily gain of barrows occurred at 76.3 kg live weight or 11 kg less than that of boars. At 105 kg, boars had 31.3% less 10th rib backfat thickness and 2.9% greater carcass length than barrows, but longissimus muscle area did not differ. Barrows had greater backfat thickness at 105 kg than 145-kg boars. As live weight increased from 105 to 145 kg, carcass length, 10th rib backfat thickness and longissimus area of boars increased (P<.01) linearly. Fat-free muscle weights of the brachialis (BR), semi-tendinosus (ST) and longissimus (L) did not differ between boars and barrows at 105 kg. Boars at 105 kg had 1.3 and 1.7% more moisture in the BR and ST, respectively, than barrows. Precentage protein, total intramuscular fat and fiber diameter in the BR, ST and L muscles did not differ between boars and barrows at 105 kg or with increasing live weight in boars. Total RNA increased linearly (P<.05) in the BR and ST as boars increased in live weight from 105 to 145 kg.

Thirty steer carcasses of the three major British beef breeds and 15 Holstein steer carcasses were selected for comparison within narrow weight and 12th rib fat thickness ranges. Fifteen carcasses of the three British breeds were selected within each of two weight ranges (light, 227 to 250 kg and heavy, 318 to 340 kg) while only heavy weight Holstein carcasses were obtained. All carcasses were selected within a 6.4 to 12.7 mm fat thickness range. The right side of each carcass was cut into boneless, closely trimmed (approximately 7.5 mm) retail cuts by wholesale cut, and roasts and steaks from the round, loin, rib and chuck (RLRC) were weighed separately from total retail cuts.The heavy British group had more (P<.01) external and total fat trim than the Holsteins, but less (P<.01) bone with no differences in total retail cuts or RLRC roasts and steaks. The light British group had a higher (P<.01) percentage of retail cuts and RLRC roasts and steaks, less (P<.01) bone and less (P<.01) external fat trim from the RLRC than Holstein carcasses.Holstein carcasses had a higher (P<.05) proportion of combined four primal cuts (RLRC) and a lower (P<.01) proportion of flank than the heavy British group. The proportion of total fat in the brisket, plate and flank was not different (P>.05), but Holsteins had a higher proportion of their total fat as kidney and pelvic fat. Holstein carcasses had a higher percentage of bone than the heavy British group, but bone distribution among wholesale cuts differed little between breed types.

The toxicity of fermented ammoniated condensed whey (FACW), ammonium lactate (AL), ammonium acetate (AA), and urea was examined in four Holstein steers consuming 50% corn silage-50% concentrate rations. Intraruminal infusion of FACW at 400 mg N/kg body weight (BW) resulted in acute toxicity as evidenced by muscle tremors, incoordination and collapse of two of the four steers. Infusion of AL at 400 mg N/kg BW resulted in similar symptoms of acute ammonia toxicity in three of four steers. Infusion of FACW or AL at 300 mg N/kg BW did not result in acute toxicity. When AA was infused at 300 and 400 mg N/kg BW, acute toxicity was observed in one and two steers, respectively. When FACW, AL or AA were infused at 200 mg N/kg BW, none of the animals showed symptoms of acute toxicity. In contrast, two of the steers infused with urea at 200 mg N/kg BW exhibited symptoms of acute toxicity. FACW and ammonium salts did not elevate rumen pH, whereas urea infusion significantly elevated rumen pH levels. At 30 min after infusion, steers given FACW, AA, or AL had lower (P<.05) plasma ammonia levels than urea-infused steers. FACW can be used as supplemental nitrogen for feedlot cattle with little chance of causing ammonia toxicity, even when fed at two to three times the level of nitrogen normally consumed in a daily ration.

Two experiments with growing lambs and one with growing beef cattle were conducted to determine the effect of supplemental selenium from sodium selenite upon performance and tissue selenium concentration when these animals were fed pelleted diets containing low or adequate levels of selenium from natural sources. Natural selenium levels were either 85 or 199 ppb in the basal diets used in the beef experiment and one sheep experiment. The two basal diets were formulated identically except that Michigan corn was used to produce the low selenium diet while South Dakota corn was used to produce the adequate selenium diet. Supplements of 100 or 200 ppb of selenite selenium did not significantly influence weight gain, feed consumption or gain/feed. Serum, sternomandibularismuscle and liver selenium concentrations were generally increased when supplemental selenium was added to the low selenium diet; however, these values were less than those obtained when equal dietary selenium concentrations were derived from natural sources. The second study with sheep confirmed that supplemental selenium can be safely provided by adding 30 ppm of selenite selenium to trace mineral salt fed ad libitum. It was concluded that there is little animal or human health hazard associated with supplementing the diets of slaughter lambs or cattle with selenite selenium equivalent to .1 ppm (100 ppb).

Certain chemical and histological characteristics of the longissimusof seven yearling bulls selected for tenderness and seven yearling bulls selected for leanness were compared. Selection for tenderness in contrast to selection for percent trimmed round and loin since 1959 has not produced significant differences between the two groups for sarcomere length, fiber area, ultimate muscle pH, collagen content, labile collagen yield or proportion of α and β collagen sub-units in muscle. In addition, factors in epimysial tissue which have been associated with cross-linking of the collagen molecule were not affected. Muscle pH at 1 hr. postmortem was significantly lower in carcasses from the tender line of cattle when compared to those from the lean line. Both muscle pH and temperature at 1 hr. postmortem were closely associated with tenderness.

The relationships of physically separably muscle, fat and bone of the left side to yields of retail cuts, fat trim and bone from the right side of 80 steer carcasses were studied. Forty light- and 40 heavy weight carcasses were selected with four fat thickness (12th rib) ranges included within each weight group.Significant (P<.01) simple correlation coefficients were observed between the separable muscle, fat and bone of the left side and yield of retail cuts, fat trim and bone of the right side for both weight and percent of these traits in the combined as well as within weight groups. Correlations between total separable muscle and retail cuts were higher in the light weight than in the heavy weight group; whereas, correlations for separable fat and bone with fat trim and retail bone, respectively, were greater in the heavy weight group. While most of the correlations within fat thickness groups within weight groups were quite similar to those for the combined fat thickness groups within each weight group, several of the correlations within fat thickness groups were considerably lower. Seventy-one percent or less of the variation in total separable muscle and fat was accounted for by percent retail cuts and fat trim. The determination of the separable components is the best determination of physical carcass composition, and the data obtained in this study indicate that retail cuts or fat trim are not as accurate for estimation of the separable muscle or fat as separable components of some carcass parts.

Eighty steer carcasses were selected within two weight groups on the basis of chilled carcass weight and within four fat thickness (av. three measurements at 12th rib) ranges within each weight group. The left side of each carcass was physically separated into muscle, fat and bone, whereas, the right sides were cut into closely trimmed boneless retail cuts. The data from both sides were collected by wholesale cut.Carcass weight had a significant (P<.01) effect upon weight of separable components (fat, muscle and bone) and yields of retail cuts and fat trim. It also had a significant (P<.01) effect upon percent retail cuts and fat trim, but not on the percent separable muscle, fat and bone. Less than one-third of the approximate liveweight difference in steers from the two weight groups in this study was in the form of separable muscle or total retail cuts.Average 12th rib fat thickness significantly (P<.01) affected weight and percent separable components, retail cuts and fat trim. Only the yields of retail cuts and fat trim were significantly (P<.01) affected by carcass weight-fat thickness interaction.Higher correlation coefficients were observed between fat thickness and compositional data than between carcass weight and measurements of composition within weight groups. Fat thickness was negatively correlated with measurements of muscling and bone and positively correlated with measurements of fat.Carcass weight showed low negative relationships to percent measurements of muscling. The relationship of carcass weight and fat thickness to separable components, retail cuts and fat trim (weight and percent) was generally higher in the light weight group, especially for percents, than in the heavy weight group. These data indicate that 12th rib fat thickness and carcass weight influence the yield of muscle and fat to a greater extent in light weight than in heavy weight carcasses. All correlations between separable components were significant (P<.01) for the combined and individual weight groups, except for that between weight of separable fat and bone in the combined weight group.

Four muscles from 25 lambs representing both high and low blood potassium groups were analyzed for potassium and sodium content. Significant differences existed in the potassium and sodium content of the different muscles on a wet basis, on a fat-free-moisture-free basis and on a protein basis. On comparing means, variations as high as 12.77% occurred in potassium concentration. The magnitude of the variation in potassium content indicated that constancy does not exist in the potassium-muscle relationship, and suggests it is a major source of error in prediction of body composition from potassium concentration. Data on the variability in sodium content, fat, protein and moisture are also presented.Four of the lambs averaged 1.44 gm. K/kg. blood and were classified in the high blood potassium group, whereas, the remaining 21 lambs had a mean value of 0.42 gm. K/kg. blood and were of the low blood potassium type. The differences in the potassium content of the two groups of lambs were not statistically significant, and suggest that the blood type is not an important cause of variability in the potassium content of lamb muscle.

A study was made to determine the effects of diet upon the fatty acid composition from several sites of hog depot fat.The leaf fat and backfat from hogs fed safflower oil was less saturated than that from controls. This difference was mainly due to palmitic acid. Fat from hogs fed safflower oil contained significantly more linoleic acid and significantly less oleic acid than the fat from control hogs. Feeding tallow tended to restore the fatty acid pattern of safflower oil-fed hogs to that of control animals. It was found that the major fatty acid changes due to diet occurred within 4–5 weeks.Diet can alter the fatty acid composition of pork fat to an extent where lard may have a favorable effect upon maintaining low serum cholesterol levels in humans. However, the adverse effects of the triglyceride structure of lard upon this phenomena must be further investigated.The fatty acid composition of the intramuscular fat from the l. dorsimuscle was affected much less by diet than was that of the leaf fat or backfat. Data suggest that the inner layer of backfat exhibited a more extensive turnover of fatty acids than the outer layer. The leaf fat and backfat from barrows contained more palmitic and stearic acids and less linoleic acid than did similar fat samples from gilts. There was no difference in the fatty acid composition of the intramuscular fat between barrows and gilts.It was found that there was no significant difference for tenderness, juiciness, flavor, over-all acceptability and Warner-Bratzler shear values for loin samples due to treatment.

Various multiple regression models were used primarily to examine the regression of swine litter traits from farrowing through 154 days of age on differences in inbreeding and in age of dam. The records included were for 7,075 litters from eight cooperating agricultural experiment stations in the Regional Swine Breeding Laboratory. Only first parity litters, from gilts aged 10 to 19 mo., were studied.An initial study indicated that the inbreeding of the sire of the litter had little or no effect on litter size at farrowing. The inbreeding of the dam significantly depressed litter size, total litter weight, and average weight per live pig at farrowing. Nonlinearity was apparent with the traits involving weight. Each of the litter traits at farrowing increased curvilinearly as age of dam at first parity increased. The predicted peak performance was by gilts of age 15 to 17 mo. at farrowing. The inbreeding of the litter showed practically no influence on litter size but evidenced a significant effect on pig weights at farrowing.The inbreeding and age of dam had practically no effect on number weaned over their indirect effects on litter traits at farrowing. However, the inbreeding of the dam continued to exert a significant direct influence on both pig and litter weights at weaning, while age of dam retained a significant effect on average weaning weight per pig. The quadratic equation provided a significantly closer fit than the linear equation in relating the inbreeding of the dam to the total weight of the litter at weaning. The inbreeding of the litter showed an increased influence on weaning traits over that shown at farrowing. Significant curvilinear relationships were noted for each trait.The inbreeding of the dam retained a significant direct effect on total litter weight at 154 days, in addition to its indirect influence through the litter traits at farrowing. No such direct effect was noted for the inbreeding of the dam on litter size or average pig weight at 154 days. However, the inbreeding of the litter exerted a significant influence on the 154-day litter traits even when litter farrowing or weaning traits were considered as covariables.The significant curvilinear effects of the inbreeding of the dam and litter suggest that complex inter-locus genetic interactions may be involved. Differential opportunities for selection also may have modified the apparent effects of the inbreeding of the dam.Average pig weight at weaning was heaviest in litters in which about nine live pigs had been farrowed and six to seven pigs weaned. The birth weight of the pig showed a highly significant influence on the litter traits at weaning and at 154 days.

Three selenium (Se) balance trials were conducted with young pigs to compare supplements (0.2 ppm Se) of natural Se (from seleniferous corn) vs.selenite Se, a stored selenite-glucose premix (in which some selenite had apparently been reduced to elemental Se) vs.a freshly prepared selenite-glucose premix, and a supplement of 22 IU of vitamin E (E) per kilogram of diet vs.no E supplement. The basal diets consisted of corn and soybean meal plus minerals and vitamins (except E) and contained 0.041 to 0.047 ppm natural Se. A higher proportion of Se from seleniferous corn was excreted in the feces (P < .05) and a lower proportion excreted in the urine (P<.01) as compared to Se from sodium selenite. An E supplement significantly reduced fecal Se excretion of pigs fed seleniferous corn. Selenium excretion in both feces and urine tended to be greater, and Se retention concomitantly less, on the stored selenite premix than on the premix which had been freshly prepared. Vitamin E supplementation of the freshly prepared selenite premix tended to increase both fecal and urinary Se excretion and to reduce Se retention.

Levels of androgens, gonadotropins and spermatogenesis were studied in 51 Herefords 1 year of age. Results with 10 of these bulls in a preliminary trial revealed a correlation of −.67 between pituitary FSH and epididymidal sperm numbers. Gonadal sperm concentration in 41, year-old Herefords (60×106/g) was similar to that for year-old and mature Holsteins, but seminal vesicular fructose and citric acid in Herefords exceeded that of Holsteins. In jugular serum, LH concentrations increased in 29 Herefords from 10 to 12 months of age, but prolactin, testosterone and androstenedione decreased. Relative to concentrations determined in jugular serum at 12 months, prolactin, testosterone and androstenedione increased at slaughter (12.5 months) while LH decreased. Testosterone concentration exceeded androstenedione at 12.5 months in testes and in serum.None of the correlations between serum LH or prolactin and serum androgens at 10, 11 or 12 months of age was significant. Concentrations of serum LH at slaughter were correlated with serum testosterone (r=.38), testicular testosterone (r=.56) and testicular androstenedione (r=.55), but similar correlations for prolactin were not significant. LH in the serum and pituitary were unrelated to gonadal and extragonadal sperm numbers. However, serum prolactin was correlated with gonadal (r=.36) and epididymidal (r=.30) sperm numbers, and comparable correlations for pituitary FSH were −.45 and −.31, respectively. These results suggest that release of FSH limits spermatogenesis at 1 year of age.

Results indicate that there was little difference in the usefulness of the live probe or lean meter in regard to estimating backfat thickness and percentage of either lean or primal cuts. However, the higher relationship for the live probe with both loin lean areas and with fat trim indicated live probe to be a more reliable measure for estimating carcass leanness.

Results of this study indicate that the various loin indices, especially the loin index and the trimmed loin-fatback ratio, reflect the various measures of leanness or fatness more accurately than percentage ham, percentage New York shoulder or percentage belly. Some evidence is presented which suggests the percentage of trimmed loin may reflect true leanness somewhat more accurately than either of the other loin indices. Percentage skinned ham and percentage New York shoulder were more accurate indicators of the supplementary measures of leanness than percentage belly, which was of little value.Data are presented showing that carcass length and percentage loin are positively correlated, yet variation in length accounted for only 17 to 18 of the variability in percentage loin. Carcass length did not appear to influence percentage belly, percentage ham or percentage New York shoulder, which explains the low relationship between carcass length and cut-outs. Evidence is presented showing some basis for the assumption that dressing percentage increases with fatness. However, the association between various measures of fatness and dressing percentage is low.

Results indicate that simple cut indices involving a minimum number of weights and adapted to large scale useage may be utilized in evaluating swine carcasses. The loin index, which is the percentage of trimmed loin in relation to rough loin, appears to be more promising than the trimmed loin-fatback ratio or the percentage trimmed loin on either the live or carcass basis. A comparison of the loin index and backfat thickness as measures of lean cuts (carcass basis) justifies the conclusion that loin index more accurately reflects percentage lean cuts. Although percentage skinned ham (both live and carcass bases) and percentage New York shoulder (both bases) indicate cut-out nearly as well as the various loin indices, all loin indices were superior as indicators of loin lean area. On the other hand, the percentage trimmed belly was a poor indicator of all cut-outs and loin lean area.Consideration of the pigs by groups showed the hormone treated-delayed castrated-limited fed group generally had higher correlation coefficients between the cut indexes and all carcass cut-outs and loin lean area than was true for the barrows or gilts. The greater variability of the treated group was apparently responsible for the higher relationships. Data from pigs on treatments which are distinctly different than those commonly used by commercial swine producers should not be used as a basis for measuring the usefulness of various evaluation procedures.

In this study the fat-lean ratio in cross section of the rough loin at the last rib was investigated as a possible measure of carcass leanness. Correlation coefficients of approximately −0.60 between the fat-lean ratio and several measures of carcass cut-out indicated the relationship may be high enough to be useful when it is impossible to obtain cut-out information. However, the area of lean at the 10th rib or last rib was only slightly less reliable than the ratio of fat to lean for estimating cut-out values.Consideration of the relationship between either carcass length or dressing percentage and carcass cut-out indicates that major emphasis should be placed on other methods of measuring leanness.

Little research has been conducted with frozen ram semen because of limited artificial insemination in sheep. However, with the possibilities of synchronized estrus and the advent of production and progeny testing, it is possible that artificial insemination will increase. A great saving in reproductive potential could be realized if ram semen were frozen and stored during an entire year. A successful technique for freezing semen could also be a useful tool in genetic research, enabling the use of the semen of ram lambs after slaughter. Frozen ram spermatozoa, to be useful, must survive prolonged frozen storage and be capable of fertilizing ova.The purpose of these studies was (1) to determine the glycerol requirement for freezing semen, (2) to determine the sperm survival effect of adding egg yolk to a milk diluter and (3) to investigate the rate of decline in motility of frozen ram spermatozoa stored at –79 ° C. over a 14-month period.

The relationship between live-animal measurements with carcass attributes was investigated using the data from 31 long yearling steers. Live-animal measurements and carcass measurements were all highly repeatable with the exception of spring of ribs, the width of pins and the length from the 13th rib to hooks.With constant live weight, circumference of body at fore flank was associated with 81 % of the variation in ribeye area, while circumference of middle, rear flank, hind leg above hock and width of rump were also significantly related to ribeye area. Live-animal weights and various live-animal measurements showed high relationships to such wholesale cuts as chuck, rib, shortloin and sirloin plus round.

Live animal weight, chilled carcass weight, primal cut weight, and estimated carcass lean in almost all instances were significantly and positively related to the weights and various linear measurements of the fore and hind cannon bones. On the other hand, the association with the cannon bone measurements and primal cuts and estimated carcass lean were greatly reduced when calculated on a percentile basis. When the effects of live weight were held constant, width and circumference measurements of the hind and fore cannons were associated with 15 to 25% of the variation existing in ribeye area. The joint effects of live weight and each of the cannon bone measurements considered separately, accounted for only 14 to 34% of the variation in ribeye area.Radiographic measurements of the dorsal and lateral view of the lumbar vertebra disclosed that width of the body of the lumbar vertebra and width of the vertical processes were the measurements most closely associated with ribeye area, accounting for 22 and 20% of the variation in ribeye area, respectively. When the effects of live weight were held constant, width of the transverse processes and height of the anterior articular processes were equal to the two previous measurements in predicting rib-eye area. The joint effects of live weight and each of these four measurements of the lumbar vertebra explains only 32 to 36% of the variation existing in ribeye area.Results indicate that both cannon bone measurements and radiographs of the lumbar vertebra are related to muscling. However, the relationships are not high enough to be useful for predictive purposes.

Differences in the general combining abilities and the general maternal effects were estimated from 2137 three-line cross pigs of 12 Poland China inbred lines. Differences in general combining ability were statistically significant, accounting for 4% of the variation among pigs of the same season-farm group. Maternal effects of the lines and the interactions involving specific effects were not statistically significant. There was good agreement between the direct transmitting abilities of the lines when estimated from the three-line cross data and when estimated for five of the lines in farm herds where they were used for commercial production.

Specific gravity of the Longissimus dorsimuscle of the 9-10-11 rib section was determined in order to test the usefulness of specific gravity as an objective measure of marbling. Ether extract was used as the standard by which the validity of this measurement was determined. Correlation coefficients between specific gravity and percent fat, water, protein and grade to the nearest one-third were −.81, 0.74, 0.68 and −.68, respectively. All were highly significant.The regression of percent fat in the rib eye on specific gravity was found to be −413.30, with a standard error of the estimate of 1.20% fat. Thus, for each increase of 0.001 units in specific gravity there was a decrease of 0.41 in percent fat. The high relationship between specific gravity and fat indicates the usefulness of specific gravity as an objective measure of marbling. Furthermore, specific gravity offers the added advantages of ease of determination and of maintainence of the meat in a saleable condition.

Data from 62 yearling Hereford and Angus steers which were fed 180 days or longer and managed alike throughout their life were used in the first part of the study. In these data, gain had a larger direct effect than age, final weight, or area of loin eye on the carcass grade of the steers, accounting for 0.11 of variation in carcass grade. All the factors taken together accounted for 0.34 of the variation in carcass grade. The direct effect of area of loin eye on carcass grade was small, 0.0016, and negative. However, the correlation between area of loin eye and carcass grade was positive, 0.20, because area of loin eye was positively correlated with age, final weight, and gain, and each of these was positively associated with carcass grade. Carcass grade was more highly correlated with final weight (correlation coefficient equaled 0.52) than with any of the other variables.Data from 42 older and larger Hereford steers fed 98 days were also analyzed. In these data, only final weight had a significant direct effect on carcass grade, accounting for 0.11 of the variation. Age of the individual steers was not known.Heritability estimates were obtained for carcass grade and area of loin eye using data from the Hereford steers mentioned in the first part. The estimates indicate that heritability is low for carcass grade and high for area of the loin eye.

THE rate of genetic improvement in a population is largely determined by the breeding plan that is used. Considering the cost and long generation intervals involved in large domestic animals, it would be very difficult to over-emphasize the importance of selecting a breeding plan that would maximize the use of existing genetic variability in such populations.The object of this study was to evaluate the amount of improvement for performance traits in crossline swine which would result from a specific selection procedure. The procedure was to select in one line for two traits, select in another line for two other traits and then cross the two lines.To estimate these changes, simulated swine herds were generated. A computer was used to generate herds that have heritabilities and genetic correlations like those in swine breeds.Pure mathematics [Griffing (1960), Kimura (1954, 1958, 1962), Kojima (1961), Robertson (1960)] and Monte Carlo simulation]Baker and Comstock (1961), Barker (1958a, 1958b), Barker and Butcher (1966), Bereskin, Shelby and Hazel (1969), Bohidar (1960), Fraser (1957a, b, 1960a, b, c) Fraser, Burnell and Miller (1966), Gill (1963, 1965a, b, c), Martin and Cockerham (1960), Parker (1966), Qureshi (1963, 1964), Young (1966)] have been used in other studies to evaluate expected genetic changes due to selection.

The experiment involved records on 375 steer and 362 heifer calves born over a four-year period, 1960 to 1963 inclusive, at the Fort Robinson Beef Cattle Research Station in northwestern Nebraska. The calves were from 80 cows each from the Angus, Hereford and Shorthorn breeds, and were the progeny of 17 Angus, 16 Hereford and 16 Shorthorn sires. Traits studied were birth weight, weaning score, and adjusted 200-day weight (steers and heifers); adjusted final weight, marbling score, final carcass grade, fat thickness, rib-eye area and actual cutability (steers); and adjusted 550-day weight (heifers).There were no differences in the sire components of variance between the straightbreds and crossbreds, indicating similar additive genetic variance in the two groups. Estimates of components of variance for between and within sires were obtained separately for each breed of sire and breed of dam group. These components were pooled to give heritability estimates in straightbred and crossbred populations. The pooled analyses yielded estimates of heritability from 0.15 to 0.85 with most standard errors between 0.3 and 0.4. No difference was noted between the estimates from crossbreds and straightbreds. Estimates of genetic and phenotypic correlations for the pooled within straightbred analyses are presented. High estimates of genotypic and phenotypic correlations were noted among the traits associated with weight (birth and 200-day weight, final weight, 550-day weight, rib-eye area, and actual cutability). Standard errors, in general, varied from 0.3 to 0.4. Estimates of the correlation between a sire's genetic ability to produce straightbred and crossbred progeny were high indicating that mass selection in purebred populations contributing germ plasm to crossbred populations would be approximately as effective in improving commerical crossbred performance as it would be in improving commercial straightbred performance.

The data from 100 bulls produced in the Michigan Beef Cattle Breeding Project were used to evaluate the relationship among performance traits of yearling bulls.Percent preferred cuts (trimmed wholesale loin and round) was influenced by carcass weight, the regression was −.005% per kg. of carcass weight. Percent preferred cuts adjusted for carcass weight was not closely associated with loin-eye area (correlations ranged from 0.04 and 0.33). Adjusted percent preferred cuts was negatively correlated with tenderness index (r=−.24 to −.38). Weight of preferred cuts was highly correlated with carcass weight (r=0.95 or higher). The correlations between percent round and percent loin were low (r=−.06 to 0.23 on a total carcass basis).There was a higher correlation between percent round (r=0.57 to 0.89) than between percent loin from the two sides (r=−.23 to 0.66). Variance in percent round was about four times as important as variance in percent loin in determining percent preferred cuts.

Studies of the ability of panels of judges to differentiate between live hogs and their carcasses for economically important characteristics have been made using a paired comparison technique. Judges of live hogs tended to be more consistent in their judgements than did those of carcasses and to achieve a perfect ranking of the seven hogs comprising each batch more nearly, although the carcass judges showed a marked improvement as the experiment progressed.Both panels of judges found it more difficult to make consistent judgements of the percent yield of untrimmed loin than of rib-eye area or of the yield of trimmed lean cuts. Rankings of live hogs for the yield of untrimmed loin showed very little relation to the actual yield of this cut, and only a slight relation for the carcass judges. Rankings of live hogs and carcasses for rib-eye area and the yield of trimmed lean cuts were both significantly related to these characteristics although, in the case of lean cut yield, the judges' predictions were no better than could have been achieved using backfat measurements.

Ground shelled corn was compared with pelleted, flaked, crumbled and commercially heat-treated corn for fattening lambs, and ground shelled corn vs. crumbled corn for fattening steers. Daily gains were not significantly related to treatments in any of the trials but the various kinds of processing apparently decreased palatability in both steers and lambs, as compared to ground shelled corn. In the individually-fed steer trial feed efficiency was significantly increased by the crumbled corn, and in both lamb experiments the various kinds of processed corn increased efficiency from 7 to 16%. The various kinds of processed corn significantly narrowed the ruminal acetate: propionate ratio in both species. The possible relationship of volatile fatty acids to the observed feed efficiency is discussed.

A group of 25 beef-type cattle and a group of 25 Holstein cattle fed on three separate trials were handled and slaughtered under similar conditions. Twenty-five beef-type steers with similar carcass characteristics to the original 25 beef-type steers were included in the cutting comparisons. The groups were compared from the standpoint of dressing percent, carcass grade, percent of wholesale cuts, percent of trimmed round, sirloin and porter-house steaks and percent of separable lean, fat and bone in the carcass. In addition, rib roasts were cooked and the meat was evaluated for cooking losses, tenderness, flavor of fat and lean, texture, aroma and juiciness. Results show that the beef-type cattle had a higher carcass yield and graded higher. Although there were a few statistically significant differences between the beef- and dairy-type steers in cut-out percents, there were no appreciable differences in percent of high-priced wholesale cuts or total trimmed retail steaks. Furthermore, the difference in percent separable lean in the carcass between breed types was negligible. Thus, there was little advantage for beef-type from the standpoint of carcass cut-out.Although roasts from the beef-type cattle had a greater shrinkage during cooking, they were rated significantly higher for intensity of lean flavor and for quality and quantity of juiciness. However, there was no significant difference attributable to aroma, texture of lean, flavor of fat or tenderness as measured with either the Warner-Bratzler shear or panel score.

A summary of four years work in progeny and performance testing of rams is reported. A total of 576 rams consisting mostly of Rambouillets with a smaller number of Corriedales, Columbias, Merinos and Suffolks have been full fed on a ration of oats and alfalfa and studied in detail. Data are presented to indicate that important and highly heritable differences exist between the performance of offspring of different sires. Other data are presented to show the phenotypic correlation existing between the various characteristics on which data were collected as possible aids in selection.

Over the last ten years approximately 5 percent of the male pigs weaned in this herd have had scrotal hernia.The differences between lines are greater than could be explained by chance alone. These differences have fluctuated from year to year, but little if any more than would be expected by chance.The yearly differences in the incidence of scrotal hernia were not statistically significant.The estimates of heritability for scrotal hernia were about 0.15 when based on differences among sires within lines. A less dependable estimate, based on differences among lines, was about 0.07. These figures estimate the amount to which the additive effects of his genes determine whether a male pig which reaches weaning age had scrotal hernia or not.Whether or not a male pig had scrotal hernia was also 15 percent determined by a maternal effect. It was not determined to what extent this unexpectedly large maternal effect was genetic or environmental.The large maternal effect indicates that a breeder should practice strong selection against sows that have produced herniated pigs. If the maternal effect can be identified as some environmental effect and if the environment which causes hernia can be easily corrected, that would offer a way to lower the incidence of hernia.Since scrotal hernia is a threshold characteristic with low heritability, hernia could be reduced by forming many inbred lines, selecting those which have the least hernia and crossing them together to form new lines. Scrotal hernia is not important enough by itself to warrant forming inbred lines but, since many lines are being formed for other reasons, the incidence of hernia should be considered when selecting among the lines.

For any trait the difference between the average phenotype of the animals used as parents and the average phenotype of all animals born that year can be calculated.This difference can be symbolized as . However, in only very specific cases is the expected genetic change (ΔG) in the trait between one generation and the next equal to heritability times . If selection is completely on the trait being considered, then ΔG=heritability times . In this case has traditionally been called selection differential.However, in any case where selection is on the basis of more than one trait, e.g., trait 1 and trait 2, then ΔG1is not equal to heritability1times , but rather is equal to . The bivalues are determined by the index used in selection, I=b1P1+b2P2. Since in this case ΔG1is not equal to heritability times , it seems unwise to describe as a selection differential. Lush (Personal communication) has proposed this be called a secondary selection differential.Examples are given in the text of the inaccuracy which may be involved by always calling a selection differential and then estimating ΔG as heritability times the selection differential.In cases where the bi values were not used in the actual selection, they can sometimes be estimated. A method of estimating the bivalues which were actually used in selection is given in the text. However, if records are not available on all traits used in selecting the animals, the estimated bivalues will be biased. If accurate estimates of bivalues cannot be made, estimates of the ΔGivalues should not be made.

This study was conducted in order to determine the effect of slaughter weight upon the acceptability, quality and processing characteristics of pork carcasses. Carcasses of 40 Yorkshire and 40 crossbred barrows and gilts were studied. The animals were divided into four slaughter weight groups ranging from 100 to 210 lb.As slaughter weight was lowered, there was a decrease in carcass length, dressing percent and loin-eye area, and an increase in the percent of primal and lean cuts. Chemical analysis of the rough ham indicated that slaughtering at lighter weights resulted in higher percentages of protein and moisture, and a lower percent of ether extract. Analysis of the longissimus dorsishowed similar trends except that no significant differences were observed in the percent of ether extract as slaughter weight decreased. Physical separation of the rough ham showed that the percent of lean increased and that the percent of fat decreased as slaughter weight was reduced.Taste panel scores indicated that fresh chops, smoked hams and bacons from the four weight groups were equally acceptable. Differences in cooking losses of the fresh chops and in the yields of the smoked hams and bacons were not significant.Surface color renotations of hue and value were not affected by slaughter weight; however, significant decreases in chroma were noted as slaughter weight decreased.Consumer studies indicated a strong preference for the 7-rib loin roasts and loin chops from the heaviest group of pigs. Although the chops from the lightest group ranked second, results suggest that the preference was based on rejection of excessively fat chops rather than a preference for the smaller chops. The 7-rib blade loin roasts from the lightest group were strongly rejected, but the Boston butt roasts from this group were preferred. In general, results indicated that the consumers would buy cuts from the lightest group, except for the 7-rib loin roasts, which were rejected because of their small size.