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Four treatments, involving differences in method of feeding and interval between last feed and slaughter, were employed in a study of the effect of dietary chlortetracycline on protease, amylase, and cellulase activity in the intestinal and cecal contents of 16 pairs of weanling pigs. Most consistent results were obtained with six pairs which were limited pair-fed except for the final feeding during which feed was available ad libitum for a 4-hour period ending 18 hours before slaughter. The mean total activities of all three hydrolases in the contents of the small intestines and of the ceca of the antibiotic-fed animals of these six pairs were significantly greater than in those of the control animals. Expressed as activity per gram dry matter of intestinal contents, significantly higher values for protease and amylase, but not for cellulase, were observed in the pigs that had received chlortetracycline. When the combined results obtained from all 16 pairs of the experimental animals were analyzed, the results showed that on a basis of activity per gram dry matter of intestinal contents, ingested chlortetracycline was associated with significant increases in amylase and cellulase but not in protease activity. Protease, amylase, and cellulase activities per gram dry matter of cecal contents were higher for pigs fed the antibiotic than for their controls. The mean wet weight of the empty small intestine and the mean dry weight of the mucosa scraped from the anterior 3-meter section of the small intestine were lower for the chlortetracycline-fed animals, but the differences were not statistically significant.

The factors important to consumer acceptance of meats were determined from 1,469 interviews conducted in Calgary, Edmonton and Vancouver. The factors included in the survey were determined by the repertory grid technique in an effort to eliminate researcher bias in factor selection. Only the acceptability of packaging was introduced as a factor of researcher interest. The most important factors related to the consumer acceptance of meats included: nutrition, tenderness, suitability for serving to special guests, fattiness, waste, and packaging. Other factors were of importance for the specific meat types or meat cuts studied. Nutrition evoked concern for healthfulness in terms of fat content and degree of meat processing. Opinions about fat content were based on preconceived ideas, and were not closely associated with wastage. Responses for the tenderness-toughness factor appeared to be influenced by the implication of this factor for the respondent's cooking ability. The factors important to consumer acceptance of all or most of the meats studied included factors related to the evaluative and potency dimensions of attitude. Activity factors were also important for specific meats and meat cuts.

Procedures are described for determining dry matter losses and for measuring volatile fatty acid production by direct chromatographic separation of acids produced during incubation of finely ground forages in miniature artificial rumen units. The results of preliminary assays done on three samples of unknown digestibility—excellent alfalfa hay, good mixed grass-alfalfa hay, and oat straw—showed that significantly different percentages of dry matter were lost and significantly different amounts of fatty acids were produced when feeds of such diverse quality were fermented. Analysis of the data for two groups of 11 and 6 samples of hay, for which dry matter digestibility coefficients as determined with sheep were available, indicated the existence of a high degree of correlation between dry matter digestibility in vivo and both dry matter loss and fatty acid production in vitro. Differences in assay results were observed when filtered rumen fluid or washed cells from the rumen fluid of sheep fed hay or from sheep fed straw were employed as sources of inocula. Examples of unsolved problems which are pertinent to the appraisal of the efficacy of artificial rumen assays for the estimation of the nutritive value of forages are discussed.

The joint and separate effects of several cow-calf variables on milk yield were studied with 176 and 201 beef cows from the University of Alberta beef breeding herd for 1966 and 1967, respectively. The dams consisted of Hereford, Aberdeen Angus, Galloway and hybrid breeding. Independent variables considered were: breed, post-calving weight, winter weight loss, summer weight gain and age of dam, and weaning age, sex and birth weight of calf. Total variance of milk yield explained by all variables together was only 40 and 52% for 1966 and 1967, respectively. Breed and age differences of dam accounted for 82 and 87% of explained variance in milk yield respectively for 1966 and 1967. Holding cow age constant, post-calving weight of cow explained 0.0 and 8.5% additional variance in milk yield for 1966 and 1967, respectively. Summer weight gain of cow was negatively associated with milk yield. Winter weight loss of cow had little influence on milk yield. There appeared to be a negative relationship between early parturition and milk yield. The effect of calf sex on milk yield of dam was inconsistent; cows suckling male calves vs. female calves yielded more milk in 1966 but less in 1967. Birth weight of calf had a small positive influence on milk yield of dam. Association between milk yield of dam and preweaning performance of progeny was high. It appeared that the quickest way to improve milk yield in beef cattle would be the introduction of breeds noted for high milk yield and by indirect selection, through selection of dams with progeny that have high average daily gain to weaning.

Carcasses of 73 pigs taken from an experiment which involved 144 barrows and gilts of Duroc × Yorkshire, Hampshire × Yorkshire and Yorkshire × Yorkshire breeding, fed either a high energy (HE) (3652 kcal DE/kg) or a low energy (LE) (2757 kcal DE/kg) ration, and slaughtered at 68, 91 and 114 kg liveweight, were dissected to study tissue development and carcass composition in pigs. To establish a starting point, an additional nine barrows and eight gilts of the same breed groups were slaughtered at 23 kg liveweight. A normal pattern of tissue growth was shown to occur, bone growth being relatively slow and muscle growth relatively fast. Fat deposition paralleled muscle growth from 68 to 91 kg liveweight, after which fat deposition exceeded muscle growth in absolute amount. Breed of sire tended to influence the carcass, muscle and fat weight per day of age as well as the proportions of lean and fat in the carcass. Gilts had more muscle per day of age and a greater percentage of muscle and less of fat than barrows. Barrows had a greater carcass weight and more fat per day of age than gilts. The LE ration resulted in higher percentage of muscle and lower percentage of fat in the carcass than did the HE ration. At all slaughter weights, the differences in the proportions of muscle, fat and bone between barrows and gilts were similar to the differences resulting from the HE and LE rations. Carcasses from gilts slaughtered at 114 kg liveweight were equal in composition to those from barrows slaughtered at 91 kilograms. Similarly, pigs fed the LE ration at 114 kg had equal carcass composition to HE-fed pigs at 91 kilograms. The data indicated that there may be some justification for extending the weight range in the Canadian grading system such that carcasses of superior composition outside the present weight range would be recognized on their merit. Some interactions occurred among breed, sex and ration groups reflecting differences in energy intake and partitioning of nutrients for tissue growth.

Relationships between a number of split and internal carcass measurements and per cent yield of the carcass and its component cuts when trimmed in accordance with commercial standards were examined using a sample of 482 hog carcasses. Carcass length and weight were found to have low predictive value, accounting respectively for approximately 9 and 4% of the total variance in per cent yield of the trimmed lean cuts (ham, loin, picnic, and butt). Commercial grade explained approximately 27% of the variance in this trait and sex approximately 21%. The most useful predictors of per cent yield of lean cuts, and the proportion of total variance explained by each, were: per cent yield of trimmed loin, 83%; ratio of loin area to total back fat, 53%; total back fat, 54%; and per cent lean in the ham face, 43%. A regression equation combining total back fat, loin area, and per cent lean in the ham face explained 63%. Regression equations are provided and implications as regards commercial grading and carcass appraisal for progeny testing are discussed.

Semen was collected over a 30-day period from 18 yearling beef bulls, nine Herefords and nine hybrids. Average age at the start of the test was 380 ± 20 days. A total of 112 attempted collections resulted in 94 samples. Fifty percent of ejaculates were considered acceptable for freezing from Herefords and 79% from hybrids, respectively. The hybrid bulls produced significantly more semen per ejaculate (3.3 vs. 2.2 ml), higher sperm concentration (1092 × 106 vs. 657 × 106 per ml), higher sperm numbers per ejaculate (3,834 × 106 vs. 1,499 × 106) and higher total motile sperm per ejaculate (1,999 × 106 vs. 669 × 106). Bull-within-breed variance was significant for semen volume, concentration, initial motility and progressive motility. Progressive motility was in favor of semen from the hybrid bulls but was not statistically significant (48% vs. 36%). It is suggested that the superiority of the hybrid bulls was related to earlier onset of puberty. The trial also suggests that useable semen for progeny test purposes can be obtained soon after bulls reach one year of age.

A study with 176 (1966) and 201 (1967) cows from the University of Alberta beef herd was conducted to investigate the effectiveness of a number of milk variables for explaining variance in preweaning gain of beef calves. The seven milk variables calculated over 24 hours were yield of milk, total energy, total protein and total solids, and percentages of butterfat, protein and solids-not-fat. These variables were measured for two periods, August and October, and averages for the two periods were calculated. Mean 24-hour milk yield ranged from 3.8 to 6.1 kilograms. Percentage of butterfat, protein and solids-not-fat, respectively, ranged from 4.10 to 5.77, 3.28 to 3.93, and 8.67 to 9.50. The intercorrelations among yield of milk, energy, protein and total solids were high and positive, ranging between 0.85 and 0.99. Correlations of milk yield with percent milk components were small and predominantly negative. Intercorrelations of percent milk components ranged from 0.09 to 0.55. Correlations of mean milk yield variables and average daily gain (ADG) of calf to weaning for the two periods ranged from 0.73 to 0.78. In most instances, total milk yield was equally or more highly correlated with ADG than the other milk yield variables. Correlations of percent milk components with ADG were low, and in most instances not significant. In 1966 data, little additional variation in ADG was explained by the inclusion of other milk variables over that explained by milk yield alone. In 1967, the inclusion of milk percent components accounted for from 2 to 7% of variance in ADG over milk yield alone. Average milk yield for the two periods of milking was more consistent than a single milking in explaining variance in ADG over both years. The response of ADG of calf to milk yield was essentially a linear relationship, but there were indications that the curvilinear relationship of ADG and milk yield should not be ignored in beef herds of relatively high milk production.

Feeding trial and digestibility experiments with seven groups of 4 lambs and digestibility experiments with 5 rumen fistulated mature wethers were conducted to compare effects of the inclusion of different levels of poor quality lowland or slough hay in pelleted vs. non-pelleted rations. Lambs fed pelleted rations containing from 45 to 90 per cent of the test hay consumed from 1.8 to 4 times as much feed daily, gained 3 to 8 times more rapidly, and required [Formula: see text] to [Formula: see text] as much feed per unit gain as did those fed corresponding non-pelleted rations.For the pelleted vs. non-pelleted comparisons, digestibility coefficients for crude protein and gross energy did not follow any consistent pattern. In the case of lambs, pelleting appeared to reduce (P

Diets containing gross energy levels of 3.9 and 3.2 Cal./gm. and crude protein levels of 14 and 18 per cent on an air-dry basis (4.4 and 3.5 Cal./gm and 15 and 20 per cent respectively on an oven-dry basis) were fed in a 2 × 2 factorial design to weanling rats and pigs. The lower energy level was achieved by adding 20 per cent of a fine aggregate of vermiculite. In the rat experiment the vermiculite was compared with a similar level or non-nutritive cellulose. Dry matter, apparent energy and apparent nitrogen digestibility and nitrogen retention were determined with 4- to 5-week-old rats weighing approximately 80 grams and with pigs averaging approximately 8, 20 and 50 kilograms liveweight.The apparent digestibility of energy and nitrogen by rats and pigs was similar. The percentage apparent nitrogen digestibility was reduced in both species fed lower energy diets. Dry matter and energy digestibilities were lowered in rats fed lower energy diets containing vermiculite but a similar effect was evident only in 8-kilogram pigs.Nitrogen retention varied between the two species. Percentage gross or digestible nitrogen retention in rats was increased with higher energy and with lower protein diets. Retention of digested nitrogen in Pigs was reduced with higher energy compared to lower energy diets. Higher protein improved nitrogen retention in 8-kilogram pigs but lowered retention in heavier pigs.

Four trials, involving 124 pigs, were conducted to study the effects of differing planes of nutrition on swine characteristics and to study the relative response of specific genetic groups of pigs to these differing planes. Seasonal and sex effects were also evaluated. Equalized limited feeding to a scale of 75 per cent of the U.S. N.R.C. recommended levels for bacon hogs was compared to liberal feeding wherein pigs were fed to appetite three times daily and to ad libitum feeding.Winter-fed pigs grew slower, were less efficient, had a higher dressing percentage and shorter carcasses than summer-fed pigs.As the plane of nutrition increased, average daily gains increased, feed conversion ratios were correspondingly inferior, dressing percentage rose, backfat thickness increased and area of loin and total Record of Performance score decreased.Females outgained barrows under equalized limited feeding, whereas barrows outgained females at a similar feed requirement by eating more feed under liberal feeding. Female carcasses were superior to those of barrows with a tendency for the differences to be greater under the equalized limited feeding system.Genotype × plane of nutrition interactions were significant for average daily feed consumed (P

Milk yield in lactating range beef cows was estimated by milking 42 cows four times at approximately monthly intervals during the lactation. Milking was by machine after oxytocin injection. Weights of calves, before and after suckling, over a 24-hour period were used to estimate calf consumption. Breed-age group averages for 24-hour milk yield varied from 3.7 to 8.4 kg, with an overall average of 6.4 kg. Breed of cow accounted for 82.5% of the variance in milk yield in these data. Milk yield declined on the average by 0.02 kg per day of lactation. The correlation between calf consumption and milk yield was 0.58. Butterfat was 3.9% on the average, protein 3.5%, solids-not-fat 9.1% and total solids 13.0%. Breed-age group or month of test did not significantly influence milk constituent percentages, although butterfat and total solids tended to rise as lactation progressed.A good estimate of milk yield was obtained by one test milking. Milk composition based on one test milking was not reliable. Milk yield as estimated in any month was highly related to calf average daily gain from birth to weaning. Use of two test milkings improved the relationship only slightly. Milk solid component percentages showed little relationship to calf gains.

A study with 173 cows from the University of Alberta beef breeding herd (1969–1970 data) was conducted to investigate the interrelation of cow body-size variables and the effect of selected cow-size variables on calf performance. The cows were classified into two breed categories: Hereford and Angus–Galloway crosses (HEAG) and hybrid and other breed crosses (HYC). Measurements of cow body-size included: postcalving weight (PCW), weight when calves were weaned (WCW), height at withers (HW), height at sacrum (HS), and average wither-sacral height (H), body length (L), and heart girth (G). Heart girth was more highly correlated with body weight than either length or height measurements, indicating that G reflects condition of animal, whereas L and H measurements tend to reflect skeletal size. Body weight was highly correlated with both PCW/H and WCW/H ratios. Weight–height ratios appeared to reflect condition; WCW/H was considerably higher than PCW/H (4.13 vs. 3.32 for HEAG and 4.02 vs. 3.15 for HYC). Across breed and age of dam a 10-kg increase in PCW resulted in a 0.7-kg increase in weaning weight of calf. A 1-cm increase in H resulted in a 0.97-kg increase in weaning weight of calf. Within breeds, preweaning performance of calves was more closely associated with H than with PCW in HEAG dams and about equal to H and PCW in HYC dams. Postweaning average daily gain was positively associated with both PCW and H for HYC dams but negatively associated with PCW for HEAG dams. For HEAG dams a 10-kg increase in PCW resulted in a 0.47-kg decrease in final weight of male calves and a 1-cm increase in H resulted in a 3.7-kg increase. For HYC cows, a 10-kg increase in PCW resulted in a 1.91-kg increase in final weight of male calves and a 1-cm increase in H resulted in a 0.82-kg increase in final weight of male calves.

A study involving three sets of data from the University of Alberta beef breeding herd (1966–67, 176 cows; 1967–68, 167 cows; 1968–70, 285 cows) was conducted to determine the influence of birth weight of calf (BW), postcalving weight of dam (PCW), and breed effect on calf performance to 365 days of age. The influence of preweaning on postweaning performance was also considered. Calves heavier at birth tended to excel in both preweaning and postweaning growth rate. A 1-kg increase in BW resulted in an increase of 2.86–4.42 kg in calf weight at 365 days of age. For male calves, PCW was negatively associated with calf weight at both 180 and 365 days of age for 1966–67 data; however, for 1967–68 and 1968–70 data, a 10-kg increase in PCW resulted in 0.70- and 0.92-kg increases, respectively, in calf weight at 180 days, and 1.96- and 2.12-kg increases in calf weight at 365 days, respectively. For female calves, a 10-kg increase in PCW resulted in 1.40-, 0.88-, and 0.29-kg increases in calf weight at 180 days of age, and 0.68-, 1.31-, and 0.31-kg increases in calf weight at 365 days of age, respectively, for the three sets of data. Breed difference explained from 22 to 43% of the variance in average daily gain of calf to weaning (ADG) but only 0.2–13.8% of the variance in postweaning average daily gain (PWADG). Male calves with higher ADG to weaning or heavier weaning weights tended to have slightly higher PWADG. A 10-kg advantage in weaning weight for male calves resulted in a 12–14-kg advantage in weight at 365 days of age.

Results of experiments to investigate the effect of dietary chlortetracycline on pancreas dry weight and on the crude fat content and hydrolase activity of the gland are presented. Chlortetracycline fed at a level of 20 g. per ton of feed caused an increase in rate of gain and efficiency of feed utilization by pigs between the ages of 9 and 17 weeks. An effect on the pancreas was indicated by significant increases in: (a) dry weight, (b) total protease and amylase activity, and (c) amylase activity per gram dry matter of the glands from animals receiving the supplemented ration. The difference remained significant after adjustment for body weight by covariance in the case of amylase activity but not for dry weight or protease activity, indicating that the effect of chlortetracycline on amylase activity was more pronounced than that on rate of gain of pigs, pancreas dry weight, or pancreatic protease activity. No significant difference in the crude fat content of the pancreas attributable to the inclusion of chlortetracycline in the ration was observed.

SUMMARYThe influence of breed and sex on relative growth patterns of muscle, bone and fat in beef cattle has been investigated. Comparisons were made of growth coefficients estimated using Huxley's (1932) allometric equation relating muscle, bone or fat to muscle plus bone using data from the dissection of half carcasses of 63 young bulls, 106 steers and 22 heifers representing a number of breed groups. Growth coefficients for muscle and for bone were found to be similar among different breed groups of bulls, steers and heifers. The proportion of muscle increased and that of bone decreased as the size of animal, measured by muscle plus bone, increased. Muscle and bone weights adjusted to common muscle plus bone weights were significantly different among breed groups within sex. Differences in amount of muscle relative to bone were therefore established at earlier stages of growth and maintained over the period represented in the present study.Growth coefficients for fat were significantly different among breed groups within sexes.Sex within breed group had no statistically significant influence on growth coefficients for muscle or for bone. Muscle and bone weights adjusted to a common muscle plus bone weight were similar for sex groups within all breed group comparisons. Sex did not have a marked effect on rate of fattening since differences between growth coefficients for fat (between sexes, within breeds) were not statistically significant—although in all comparisons growth coefficients for fat were lowest for bulls, intermediate for steers and highest for heifers. Sexes differed in weight of fat adjusted to common muscle plus bone weight, heifers being fatter than steers and steers fatter than bulls, a difference probably resulting more from early onset of the fattening phase in heifers, followed by steers, rather than relative rate of fattening.

Experiments with castrate male Landrace × Lacombe – Yorkshire and Yorkshire × Lacombe – Yorkshire pigs, weighing 15 to 195 pounds, and with weanling male rats, were designed to study the value of stabilized tallow as an energy source. A 3 × 3 factorial design was used with rations containing 0, 15 and 30 per cent supplemental fat (gross energy levels of 4.0, 4.8 and 5.4 kcal./gm. of ration) and 14, 18 and 22 per cent protein.The addition of 15 or 30 per cent supplemental fat to the rations of pigs decreased feed consumption, increased average daily gain, and improved efficiency of digestible energy and feed utilization. Generally the higher levels of protein in the ration resulted in increased feed consumption, increased rate of gain, and improved efficiency of digestible energy and feed utilization as compared to the lower level of protein. The results from the rat experiment were similar, except that fat levels in the rations did not influence rate of gain or efficiency of digestible energy utilization.Carcasses of pigs receiving supplemental fat in their rations had an increased thickness of backfat and higher dressing percentage. As protein levels in the rations increased, average backfat thickness decreased and area of loin muscle increased. Several significant interactions occurred which were associated with breeding or with replicate differences.

The effect of winter weight loss in Hereford cows on calf birth weight and performance to weaning was examined over a period of 4 yr. The average winter weight loss of cows (60 ± 36.2 kg mean ± SD) over the period of this study had a significant effect (P 0.05) effect on the pre-weaning daily gain, or weaning weight of their calves.

To elucidate the influence of high body weight selection on body compositional relationships, the accumulation of lipid, protein, and ash was investigated in two lines of mice selected for high 42-day body weight (H lines) and an unselected foundation population (FP). The two H lines differed in population size and were designated as the high–large (HL) and high–small (HS) lines. Logistic body growth curves revealed that HL mice exhibited an accelerated growth rate and reached a higher mature body weight than FP or HS mice. Over the range of body weights examined, HL mice had more lipid, less protein, and less ash than FP or HS mice of the same sex and body weight. However, HL lipid accumulation (relative to body weight increase) was not accelerated in comparison to that of FP mice. This study suggests that the existing model of selection-mediated compositional changes requires expansion to account for the ability of high-growth selection to direct an acceleration of body growth without a correlated enhancement of the relative rate of fat accumulation.Key words: mice, selection, body composition.

Data from a two-breed group diallel experiment involving double-muscled (DM) and normal (N) cattle were analyzed to evaluate the importance of heterosis, maternal and direct effects for reproduction and growth traits. The DM cattle were from a composite of primarily Angus, Charolais, Galloway and Hereford breeds, and N cattle were crossbred cattle with at least 50% Hereford breeding. The data comprised a total of 491 matings and 389 calvings in four breeding seasons. Records on calving performance, calving date, calf crop born and weaned, sex ratio of progeny and weight of calves were analyzed using least squares procedures. Significant heterosis of 5 to 12% was observed for all the calf crop and growth traits, except for birth weight. Heterosis resulted in 24% reduction in the incidence of dystocia and perinatal calf mortality (P less than .05). The significant heterosis was due mainly to poor production in DM X DM crosses. The DM cows were superior (P less than .05) to N cows in reciprocal crossing (maternal effect) for all the calf crop traits, but had higher incidence of calving difficulty and a higher proportion of male progeny. Significant direct effect was observed for all the traits except calving date and sex ratio among progeny. The N sires were superior for all the calf crop traits and caused less incidence of dystocia and perinatal mortality compared with the DM sires. Significant differences were obtained between the straightbreds for all the traits except calving date. The N straightbreds were superior to the DM straightbreds for all the significant traits.

SummaryRestriction site analysis revealed a variant growth hormone gene haplotype fixed within growth-selected mice (High line-3; HL-3) exhibiting growth rates 1·5 times greater than those of unselected Foundation population (FP-3) mice. Relative to the FP-3 haplotype, the HL-3 haplotype exhibited restriction fragment length polymorphisms for each of seven different restriction enzymes. Three of the polymorphic sites lie within 1·1 kb of the 5′ end of the structural gene; a fourth polymorphism exists within the structural gene. The HL-3 haplotype was also fixed within an additional three growth-selected lines (including a replicate of HL-3). This identification of an association, between the natural variant of a growth regulating gene and a growth-related phenotype, is the prototype of experiments that could lead to the isolation of variant genes which enhance livestock production characters.

Records of 547, 2-yr-old heifers of three breed groups were used to evaluate the relative influence of dam's body and pelvic measurements, calf birth weight, sire birth weight and some relative measures (ratios) of calf birth weight and dam weight at calving on calving difficulty. The data were analyzed by regression and least squares procedures. The full model explained 32.5% of the variation in calving difficulty score. The linear effect of calf birth weight was the most important variable, accounting for 17.8% reduction in the coefficient of determination, and together with dam weight at calving and the quadratic effect of calf birth weight it accounted for 92% for all the variation explained by the full model. Dam weight at calving was negatively related to calving difficulty. Breed, year and sex of calf did not influence calving difficulty score, except when the calf birth weight or dam weight or both were excluded from the model. When calf birth weight was expressed as a ratio of the dam's weight at calving, hip height and pelvic measurements, the total model explained 34.8% of the variation in calving difficulty score. The ratio of calf birth weight to dam weight was the most important variable (R2 = 26.8%). Ratios of calf to dam weight at calving and calf weight to the vertical pelvic diameter (R2 = 29.3%) were the only significant factors when the effects of calf birth weight and dam weight were removed from the model. Pelvic measurements, on their own, did not influence calving difficulty score in this study (P greater than .1), but small pelvic dimensions tended to be associated with higher calving difficulty scores.

Factors influencing calving difficulty in beef herds are examined using two data sources. The first set of data was from two breed populations maintained by the University of Alberta at its experimental beef breeding ranch and the second was obtained from the Canadian Charolais Association ‘Conception to Consumer’ progeny testing programme.

The effects of breed–type, sex and age on the density of four bovine limb bones were studied. The density of the four limb bones increased significantly with age, but the effects of breed–type and sex were variable. The results are discussed with reference to the densiometric method of predicting carcass fatness.