Medium Energy Diet Research Articles

Response of Male Buffalo Calves to Different Levels of Energy and Protein in Finishing Diets

A factorial experiment with completely randomised design was conducted, using 27 heads of 15 month buffalo male calves with initial live weight of 287 +/- 15 kg. The animals were individually housed and randomly allocated into 9 treatment groups of three animals each. Three levels of energy (E1, E2, E3) with three levels of crude protein (P1, P2, P3) were formulated to provide 90, 100 and 110% requirement equivalents for 900 g, expected body weight gain of steers derived from NRC beef cattle requirements (1976). Live weight changes were obtained by direct weighing of the animals every month and ended by slaughtering the calves for carcass index measurements. Results indicated that Dry Matter Intake (DMI) was not significantly different between treatments. Average Daily Gain (ADG) ranged from 503 to 951 g/animal that was significantly varied among the diets (p < 0.05). The significantly higher daily gain was obtained (p < 0.05) when animals received medium energy diets that was similar to 100% beef cattle steer requirements. In addition the feed conversion ratio was significantly lower, when the animals received medium energy diets (p < 0.05). The dressing yield as well as the meat % age was not affected by the type of the diet, but abdominal fat was significantly higher in medium energy diets (p < 0.05). It can be concluded that the optimum fattening performance of 15 month old buffalo male calves may be obtained by providing around 10.42 MJ/kg of dietary metabolisable energy and about 10.22% of crude protein.

Long-term effect of selection for litter size and feeding programme on the performance of reproductive rabbit does 1. Pregnancy of multiparous does

AbstractA total of 166 crossbred does were used to study the possible long term effect of two types of crossbred does (H1 v. H2, old and current generations, respectively) from the cross of different generations of lines selected for litter size, the use of a feeding programme based on a low-energy diet during the rearing and the administration of a high-energy diet during reproductive life, on the performance and body condition of multiparous pregnant does. Selection did not affect the live weight (LW) of does at the effective artificial insemination (AI; 4257 g), the LW change (+12·3 g/day) and food intake (172 g dry matter (DM) per day) until the 28th day of pregnancy. However, H2 does showed greater LW losses during the pre-partum period than H1 does (120+g;P&lt;0·05), perhaps related to their higher prolificacy (+1·1 total pups born;P&lt;0·05). H2 does showed a higher perirenal fat thickness (PFT) at first AI (+0·12 mm;P&lt;0·05) than H1 does, these differences disappearing at effective AI. Females given a high-energy reproduction diet showed a lower LW at effective AI than those receiving a medium-energy diet (4210, 4305 g, respectively;P&lt;0·05). However, type of reproduction diet did not affect the LW and PFT changes of pregnancy does, reaching partum with a similar PFT (8·83 v. 8·93 mm) and maintaining the differences in LW. Pregnant does given high-energy diet consumed 20 g DM and 1·4 g digestible protein per day less than does receiving medium-energy diet until the 28th day of pregnancy, but their digestible energy (DE) intake was significantly higher (+78 kJ DE per day;P&lt;0·05). Does given high-energy diet showed a significantly lower litter size at birth (−0·7 pups;P&lt;0·05), although there were no significant differences in the number of pups born alive (9·54 and 9·76 pups for high and medium-energy diets, respectively). Pups from does given high-energy diet were slightly weightier than those from medium-energy diet (+5·4 g;P&lt;0·05). Multiparous pregnant does that received a low-energy diet ad libitum during the rearing period and first pregnancy showed a higher LW at effective AI (+137 g LW;P&lt;0·05) but a lower PFT (−0·26 mm;P&lt;0·05) than those females that received a medium-energy diet restricted during this same period. These differences were maintained at parturition (+142 g LW and −0·20 mm;P&lt;0·05). Feeding programme during rearing affected neither the food intake of multiparous pregnant does until the 28th day of pregnancy, nor the litter size and weight at birth. The interval between parturitions was not affected by the selection for litter size or the reproduction diet received, but was longer for does that received the low-energy diet ad libitum during the rearing period (+2·9 days;P&lt;0·05). In conclusion, rabbit selection programmes by litter size seem to be working well, but high energy reproduction diets, frequently used to cover their higher energy requirements, must be used carefully out of lactation in the long term to avoid a reduction in litter size.

Effect of dietary energy levels on the urinary excretion of purine derivatives in sheep

ABSTRACTThe effect of dietary energy levels on the urinary excretion of purine derivatives (PD) was investigated in sheep fed hay and concentrate diets. In addition, the possibility of using PD concentrations in spot samples of urine as a useful tool for determining daily PD excretion was also examined. Three female lambs (mean bodyweight (BW) ± standard error, 31.4 ± 1.0 kg) were fed three diets consisting of timothy hay (20 g dry matter/kg BW per day) and rolled barley at three different energy levels (low‐energy (LE), medium‐energy (ME) and high‐energy (HE) at 1.0‐, 1.2‐ and 1.5‐fold greater than the maintenance level of energy (450 KJ/BW0.75/day), respectively) in a 3 × 3 Latin square design. The dietary protein level was almost constant (380 mg nitrogen/BW0.75/day as digestible crude protein base) and was adjusted using soybean protein. Digestible organic matter intake (DOMI) increased (P &lt; 0.05) with an increase in the dietary energy level and there was a difference (P &lt; 0.05) in the organic matter digestibility between the LE and HE diets. For urinary PD excretion, the differences between the LE and ME diets and the HE diet were significant (P &lt; 0.05), although there was no clear difference between the LE and ME diets. There was a positive correlation (r = 0.47, P &lt; 0.05) between urinary PD excretion and DOMI. There was also a correlation (r = 0.59, P &lt; 0.05) between the urinary PD level at 7–8 h after the morning feed and the daily total PD excretion, suggesting that the PD level in spot urine samples could be useful for estimating microbial protein synthesized in the rumen and/or digested in the lower gut.

Efeitos da dietilpropiona, energia da dieta e sexo sobre o ganho de peso corporal, peso dos órgãos e deposição de tecidos em ratos

O objetivo deste trabalho foi avaliar a dietilpropiona (DEP), um derivado fenetilamínico utilizado como anorexígeno, e dietas de diferentes densidades calóricas, utilizando ratos de ambos os sexos. O experimento contou com 72 ratos Wistar distribuídos por sexo, bloqueados por peso inicial e alocados dois a dois em 36 gaiolas experimentais. As dietas e a água foram fornecidas ad libitum e atenderam a todas as exigências dos animais, sendo que a dieta de alta energia continha 3.700kcal de energia metabolizável (EM)/kg, a média 3.350kcal EM/kg e a baixa 3.000kcal EM/kg de ração. A droga foi administrada com uma dose diária de 20mg/kg, durante 36 dias, por via intraperitonial. A análise estatística considerou os efeitos da droga, energia da dieta, sexo, triplicata e a interação entre essas variáveis. Os resultados mostraram que houve interação entre dieta e droga (p&lt;0,0195) e que o uso da droga diminuiu o consumo alimentar apenas em dietas de baixa e média energias. A interação entre sexo e droga (p&lt;0,0253) mostrou que a droga reduziu o ganho de peso em ambos os sexos. Concluiu-se que a DEP reduziu o ganho de peso dos machos e das fêmeas, com redução de gordura depositada em ambos os sexos, sendo que as percentagens de deposição de gordura foram maiores nas fêmeas do que nos machos, os quais depositaram mais proteína. A DEP foi responsável pela redução no consumo de dietas de baixa e média energia metabolizável, não havendo efeito em dietas de alta energia.

Effects of dietary energy density on feed intake, body weight gain and carcass chemical composition of Omani growing lambs

Forty male Omani lambs were used in a feeding trial to study the effects of feeding diets containing various levels of metabolizable energy (ME) on growth and carcass composition. Ten lambs were selected randomly and slaughtered at the start of the trial to provide information on initial carcass composition. Thirty lambs were divided randomly into three groups and fed three diets varying in ME concentration (low, medium and high) from weaning (at average 76 days) until slaughter at the mean weight of 30 kg. Digestibility of dry matter (DM) was 66.9, 68.7 and 73.9% for low, medium and high energy diets, respectively. Apparent gross energy digestibility was 66.8, 67.2 and 73.3% corresponding to dietary concentrations of 12.2, 12.6 and 13.9 MJ of DE/kg for low, medium and high energy diets, respectively. Daily DM intake ranged between 3.12 and 3.73 % of body weight (BW) which was equivalent to 76.5–97.5 g/kg 0.75 or 0.738–1.142 MJ ME/kg 0.75. Daily BW gain increased ( P < 0.001) with increasing ME density with a maximum of 154 g/day observed in lambs on high energy diet during the last 4 weeks of the experiment. Feed conversion ratio (FCR), i.e., kg feed/kg BW, improved with increasing ME density ( P < 0.001). Sheep fed high energy diet had heavier BW ( P < 0.01), empty BW weight ( P < 0.001), carcass weight ( P < 0.01) higher dressing percentage ( P < 0.05) but lower gut content ( P < 0.001) than lambs fed medium and low energy diets. Sheep slaughtered at the end had lower water, protein but higher carcass and non-carcass chemical fat than sheep slaughtered at the start of the experiment. This study indicated that meat production from sheep in Oman will be improved in form of higher BW gains and better carcass composition by increasing energy levels in the diet.

Milk production of Tswana goats fed diets containing different levels of energy

The aim of this experiment was to characterize the milk yield of the Tswana goat of Botswana. Twenty-one Tswana goat does were allocated to one of three diets formulated to provide energy for maintenance and a milk yield of either 1.5 kg/d, 1.0 kg/d or 0.5 kg/d. Intake, milk yield and kid growth rate was monitored for 14 weeks. Dry matter intakes of up to 5% of body weight were recorded. Energy intake and milk yield differed between treatments (p < 0.01). Daily ME intake for the low, medium and high-energy diets was 1.01, 1.42 and 1.64 MJ ME/kg metabolic weight; the corresponding milk yields were 0.47, 0.53 and 0.72 kg/day. Kid birth weight ranged from 2.6 to 2.9 kg, and daily gains over the 14-week period were 95, 116 and 128 g/day for the low, medium and high energy diets respectively. Milk output accounted for 62% of the variation in kid growth rate. It was concluded that Tswana goats have the potential to respond to increasing levels of energy intake by increasing milk yield to relatively high levels. (South African Journal of Animal Science: 2000, 30(1): 77-81)

Effect of energy and protein density of prepartum diets on fat and protein metabolism of dairy cattle in the periparturient period.

To determine if increased nutrient density in prepartum diets improves nutrient balance of peripartum cows, we blocked 40 Holstein cows and 40 heifers by expected date of parturition and assigned them randomly within blocks to one of four treatment diets varying in density of net energy for lactation (NEL) and crude protein (CP). Diets were 1.30 Mcal of NEL/kg and 12.2% CP, 1.49 Mcal of NEL/kg and 14.2% CP, 1.61 Mcal of NEL/kg and 15.9% CP, and 1.48 Mcal of NEL/kg and 16.2% CP. These diets were fed ad libitum from 25 d prepartum until parturition, and all cows were fed the same diet after calving. Increased nutrient-density of prepartum diets did not decrease feed intake. Compared to animals fed the lowest density, those fed the highest density consumed more NEL (20 vs. 14 Mcal/d) and gained more body condition, backfat, and body weight. They also had less nonesterified fatty acids in plasma (176 vs. 233 microM) and more insulin-like growth factor-I in plasma (472 vs. 390 ng/ml) during the last 2 wk prepartum and less triglyceride in liver at parturition (0.9 vs. 1.5%, wet tissue basis). Quadratic effects of energy density were not observed, and the addition of protein in the medium energy diet had no effect. Prepartum diets did not alter any variables during lactation. In conclusion, increasing the energy and protein density up to 1.6 Mcal of NEL/kg and 16% CP in diets during the last month before parturition improves nutrient balance of cattle prepartum and decreases hepatic lipid content at parturition.

Effect of season and dietary energy concentration on composition and strength of skin in naked neck fowl

1. Two experiments, in spring and summer, were conducted to evaluate the effect of dietary energy concentration on the composition and strength of the skin of naked neck fowl. The heterozygous naked neck birds were also compared with their normally feathered sibs under summer temperatures. 2. The average temperatures were 21.2°C and 27.1°C in spring and summer experiments, respectively. Three concentrations of dietary energy were fed to the birds. The diets used were: a low energy diet of 12.12 MJ ME/kg; a medium energy diet of 12.96 MJ ME/kg; and a high energy diet of 13.79 MJ ME/kg. Two protein concentration per energy treatment, 230 and 200 g/kg, respectively were used from 0 to 3 and 3 to 7 weeks of age. 3. A significant season sex interaction showed that the skin of males had higher protein and collagen and lower dry matter and fat content than that of females, when grown under summer conditions. No sex differences were present under spring conditions. 4. The differences between sexes was not significant in spring but males had stronger skin than females in summer. Neither ambient temperature nor dietary energy concentration significantly affected skin displacement of naked neck birds. 5. In comparing the naked neck and their normally feathered sibs in the summer experiment, it was found that naked neck birds had lower skin fat content and higher skin protein content than normally feathered birds.

Influence of dietary energy on bird performance, carcase parts yields and nutrient composition of breast meat of heterozygous naked neck broilers reared at natural optimum and summer temperatures

1. Heterozygous naked neck birds were raised under natural spring (average 21.2°C) and summer temperatures (average 27.1°C) to investigate the influence of dietary energy on broiler performance, carcase yield and nutrient composition of breast meat. 2. Birds were fed on a low energy diet of 12.12 MJ ME/kg, a medium energy diet of 12.96 MJ ME/kg and a high energy diet of 13.79 MJ ME/kg with 2 protein concentrations per energy treatment, 230 and 200 g/kg, from 0 to 3 and 3 to 7 weeks of age, respectively. 3. Summer rearing resulted in a decrease in body weight, body weight gain, carcase weight and carcase part yields of birds. 4. Increasing dietary energy from 12.12 to 13.79 MJ ME/kg increased body weight at 3 and 7 weeks, body weight gains from 0 to 3 and 3 to 7 weeks, carcase weights and relative abdominal fat weights of birds in a linear manner. There was no effect of dietary energy on the nutrient composition of breast meat. 5. It was concluded that there was no differences in dietary energy requirements of heterozygous naked neck birds when grown under natural optimum (21.2°C) and summer temperatures (27.1°C).

Genetic parameter estimation of postweaning gain, feed intake, and feed efficiency for Hereford and Angus bulls fed two different diets

Postweaning gain performance and individual feed intake on 271 Hereford and 263 Angus bulls were recorded during three 168-d test periods from 1984 to 1986. Each breed was composed of two lines and within each breed bulls were fed either a high-energy (HD) or a medium-energy (MD) diet. Energy intake was partitioned into energy for maintenance and growth based on predicted individual animal requirements. Estimates of heritability were obtained using Restricted Maximum Likelihood with an individual animal model including fixed effects of year, diet, and covariates of initial weight and backfat change by breed and with line effects for overall data. Bulls fed the HD grew faster and had higher metabolizable energy intake per day (MEI), residual feed consumption (RFC), and gross and net feed efficiency (FE and NFE) (P < .001) than those fed the MD. Estimates of heritability for Hereford and Angus bulls, respectively, were .46 and .16 for 200-d weaning weight (WWT), .16 and .43 for average daily gain (ADG), .19 and .31 for intake per day (MEI), .43 and .45 for yearling weight (YWT), .07 and .23 for RFC, .08 and .35 for FE, and .14 and .28 for NFE. Genetic and phenotypic correlations between MEI and ADG, MEI and YWT, ADG and YWT, ADG and FE, YWT and FE, and FE and NFE were moderately to highly positive for both breeds. Negative genetic and phenotypic correlations between NFE and ADG show partial correlations of FE with ADG after accounting for energy requirement for maintenance. Residual feed consumption was negatively associated with YWT, FE, and NFE, indicating a possible genetic improvement.

Comparison of insulin infusion sites on metabolite net flux and insulin kinetics in growing euglycemic beef steers3

Four beef steers (average BW, 246 kg) were used in a split-plot design with five bovine insulin (I) infusion rates (5, 10, 20, 40, and 80 mU.kg-1.h-1) in the main plot and two infusion sites, mesenteric (M) and jugular (J) veins, in the subplot. Steers were fed a medium-energy diet at .235 Mcal of ME/kg BW.75 daily in 12 equal feedings at 2-h intervals. Catheters were placed in the mesenteric, hepatic-portal, and hepatic veins and in the abdominal aorta. Blood was sampled from the arterial, portal, and hepatic catheters at 20-min intervals for 1 h before I infusion. Glucose was infused intrajugularly to maintain euglycemia during the I infusion, with arterial glucose monitored at 10- to 15-min intervals. After at least 2.5 h, blood was again sampled at 20-min intervals for 1 h. Blood flow was determined by downstream dilution of p-aminohippurate. Arterial I concentrations (+/- SE) at the greatest I infusion rates were 183.5 +/- 10.46 (J) and 179.0 +/- 6.64 (M) microU/mL. Portal I concentration tended to be greater during M than during J infusion (e.g., J, 199.9 +/- 10.48 vs M, 225.8 +/- 8.99 microU/mL at the greatest dose). Hepatic glucose production at the larger three I doses reached a plateau near 40% of the preinfusion production rate (.57 +/- .02 mmol.kg-1.h-1 vs J, .23 +/- .029 and M, 27 +/- .037). Urea N concentration decreased, but portal uptake or hepatic release of urea N was largely unaffected by I dose or site of infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Recombinant Bovine Somatotropin with Lactating Cows Fed Diets Differing in Energy Density

Sixty-four Holstein cows (32 primiparous) were assigned randomly at parturition to one of two diets differing in forage:grain ratio and were further assigned to either control or treatment with recombinant bST. A full lactation study was conducted. Total mixed rations consisted of alfalfa silage, high moisture ear corn, soybean meal, and vitamin and mineral supplements. Percentages of forage in the diet (dry basis) for the high and medium energy diets were wk 1 to 12, 38.2 and 58.2; wk 13 to 26, 48.2 and 68.2; and wk 27 to 44, 68.2 and 88.2. Injection of a saline placebo or 20.6 mg/d per cow of bST started at wk 13 and stopped at wk 43 of lactation. Administration of bST increased 305-d milk yield by 19.9 and 18.3% for multiparous cows fed high and medium grain diets and by 13.0 and 5.9% for primiparous cows fed the same diets. Body weight gain during lactation tended to be lower for cows treated with bST, and body condition scores were significantly lower for those treated with bST and fed the medium energy diets.Daily injection of bST did not change concentrations of glucose or urea in blood or β-hydroxybutyrate in plasma. Multiparous cows had a transitory increase in plasma FFA concentration immediately after bST treatment started. Milk composition, health, and reproductive parameters observed were not adversely affected by bST administration. Cows fed low energy diets during bST administration in the first lactation did not produce as much milk as controls when compared during the first 10 wk of their second lactation.

Effect of postweaning implantation of zeranol and dietary energy level on growth and reproductive performance of replacement beef heifers

Eighty-one heifer calves weaned at an average age of 6 mo were used to study the effect of postweaning zeranol implantation, on the growth and reproductive performance of heifers fed to grow slowly on three dietary energy levels. Forty heifers were implanted with 36 mg of zeranol at 30 d and again at 120 d postweaning. The remaining heifers were used as ummplanted controls. Within the implanted and control groups, heifers were subdivided into three groups and fed either a low, medium or high energy diet, which provided approximately 105, 130 and 160%, respectively, of NRC maintenance energy requirement, until 1 yr of age. The heifers were then turned out to pasture with hay supplementation. Heifers were exposed to bulls for 35 d at approximately 14 mo of age. Zeranol had no significant effect on growth. The effect of zeranol on the reproductive traits studied was not significant, although the trend was that the zeranol implanted heifers had lower calf crop born (52.3 vs. 63.6%) and lower incidence of calving difficulty (18.5 vs. 32.1%) than control heifers. The level of energy in the diet had a significant (P &lt; 0.01) effect on growth of the heifers, with those on the high energy diet having the highest mean growth rate, but no significant effect on reproductive performance. Key words: Zeranol, dietary energy, growth, reproduction, heifers

Postweaning growth of unselected Hereford and Angus cattle fed two different diets.

Two unselected herds of purebred Hereford and Angus cattle were created and their progeny evaluated during a 4-yr period (1964 to 1967) for 168-d postweaning gain when they were fed either a high- or medium-energy diet. Birth weight and 200-d adjusted weaning weight also were measured and the importance of sire x diet interactions for postweaning gain examined. Year effects were significant (P less than .001) for all traits in Herefords and for postweaning gain in Angus. Postweaning gain of both breeds increased in successive years, but no trend was observed for birth and 200-d weights. Bulls were heavier than heifers (P less than .05) for all three traits in both breeds. Hereford and Angus calves receiving the high-energy diet gained more (P less than .001) than their contemporaries fed the medium-energy diet. Sire differences were significant for birth weight in Herefords and for all three traits in Angus. Sire x diet interactions were not significant for postweaning gain in either breed. Genetic correlations were calculated by two methods: the two-way ANOVA approach using sire and sire x diet interaction variance components and the one-way ANOVA approach in which gains by progeny of each sire on each diet were considered to be two distinct traits. The genetic correlations for gain in Herefords could not be estimated by either method because of negative sire variance component estimates. The genetic correlations for gain in Angus were 1.08 for the two-way ANOVA method and 1.43 +/- .64 for the one-way ANOVA method. These results indicate that sires ranked the same based on progeny performance when fed either diet.

Epididymal sperm reserves in 12-month-old Angus and Hereford bulls: Effects of bull strain plus dietary energy

Bull calves ( n = 103) were obtained from two strains of Angus and two strains of Hereford cattle developed by selecting replacements on the basis of superior feedlot growth performance within breed on either high- or medium-energy diets. From weaning to slaughter at 12 months of age at the end of a 168-day growth performance test, bulls of one strain of each breed were fed the high-energy diet (80% grain +20% forage; 13.064 MJ/kg) and bulls of the second strain were fed the medium-energy diet (100% forage; 9.110 MJ/kg). At one year of age, Angus bulls had heavier ( P < 0.01) testes than Hereford bulls (409 vs. 330 g). Level of dietary energy did not affect paired testicular or paired epididymal weight. Compared with Hereford bulls, Angus had greater ( P = 0.06) cauda epididymal sperm reserves (4.9 × 10 9 vs. 3.6 × 10 9 spermatozoa). Bulls fed the medium-energy diet during the 168-day growth performance test and slaughtered at 12 months of age had 41% greater ( P < 0.05) caput-corpus epididymal sperm reserves (4.8 × 10 9 vs. 3.4 × 10 9 spermatozoa), 58% greater ( P < 0.01) cauda epididymal sperm reserves (5.2 × 10 9 vs. 3.3 × 10 9 spermatozoa), and 52% greater ( P = 0.01) total epididymal sperm reserves (9.9 × 10 9 vs. 6.5 × 10 9 spermatozoa) than bulls in the high-energy diet group. Thus, the sperm reserves of yearling Angus and Hereford bulls appear to be greater if bulls are selected and managed on a medium-energy rather than a high-energy diet.

Grouping and complete diet composition in relation to parity and potential yield in dairy cows

SummaryThree experiments, involving a total of 294 Israeli Holstein cows, were carried out to study aspects of the grouping of cows in relation to timing of changes and the type of complete diet given. In Expt 1, 40 cows were changed from a high energy diet to a medium energy diet either at 60 or at 180 days post calving. The results indicated a larger reduction in milk and FCM yield following the later than the earlier change of diet.Experiment 2 involved 64 cows subjected to two treatments, one involving a ‘uniform’ diet (25:75 forage to concentrate D.M. ratio) and the other a ‘step’ treatment where the same diet as in treatment 1 was given for approximately 74 days and then changed to a diet of 35:65 forage to concentrate ratio. The results showed that it is not necessary to adopt different feeding systems according to the potential yield of the cow and that cows could be given rather lower energy diets within the range offered without loss of efficiency.In Expt 3, involving 190 cows, the cows were divided into one of two feeding treatments, ‘uniform’ and ‘step’ similar to Expt 2 and the effect of potential yield and parity was considered. The results emphasized the importance of potential yield rather than feeding system in relation to yield. The results showed a shorter period from calving to conception for the ‘uniform’ treatment.A strategy for efficient cow feeding is outlined.

Testicular development, daily sperm production and epididymal sperm reserves in 15-mo-old Angus and Hereford bulls: effects of bull strain plus dietary energy.

Bull calves (n = 143) were obtained from two strains of Angus and two strains of Hereford cattle for which replacements were selected on the basis of superior feedlot growth performance on either high- or medium-energy diets. From weaning to slaughter at 15 mo of age, bulls were fed either the high-energy (80% grain + 20% forage) or medium-energy diet (100% forage) corresponding to their strain. Bulls in high-energy diet groups had a greater (P less than .05) scrotal circumference at 12 mo, but not 15 mo of age, than bulls in medium-energy diet groups. Compared with Hereford bulls, Angus had greater (P less than .01) scrotal circumference (36.1 vs 33.9 cm) and greater (P less than .05) paired testes weight (570 vs 464 g) at 15 mo of age. Daily sperm production per gram testicular parenchyma (DSP/g) was affected by strain-diet (P less than .01) but not by breed. Bulls in medium-energy diet groups had 12% greater DSP/g than did high-energy diet bulls (17.4 X 10(6) vs 15.5 X 10(6)). Daily sperm production (DSP) was 9% and 30% greater (P less than .01) for medium-energy diet bulls in 1980 (8.2 X 10(9) vs 7.5 X 10(9)) and 1981 (8.0 X 10(9) vs 6.2 X 10(9)), respectively, compared with high-energy diet bulls. The effect (P less than .01) of breed on DSP was attributed to breed differences in paired testes weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship among Definable Characteristics of Feeder Calves, Subsequent Performance and Carcass Traits. II. Subjective Scores

Three-hundred and forty-nine commercial calves of Angus, Hereford, Charolais-cross and Angus × Hereford breeding were fed to an estimated constant subcutaneous fat thickness (12 mm) on high and medium energy diets. Physical description of feeder calves, in terms of subjective scores for frame, fat and muscle, combined with initial calf weight and breed classification, explained 49% of the variation in carcass weight within diet-year subclasses and 32% of that in days on feed. Deletion of subjective scores from the models reduced coefficients of determination for carcass weight and days on feed by 13 and 5%, respectively. Corresponding reductions from deletion of terms for breed were 9 and 11%. Among descriptive variables (listed in order of magnitude of partial mean-squares), frame (P<.001), breed (P<.001), initial weight (P<.05), fat (P<.05) and frame × breed (P<.05) were sources of variation in carcass weight; while breed (P<.001), frame × diet (P<.01) and fat (P<.01) were related to days on feed. In general, frame was positively related and fat negatively related to carcass weight and days on feed. Effects of frame were similar to those of measured wither height and body depth, and subjective fat was less related than ultrasonically measured fat to response variables. Coefficients of determination from models describing yield and quality grades were .11 and .07, respectively. Muscle was unrelated (Pώ.05) to response variables studied.

Effect of feeding system on performance and carcass characteristics of yearling steers, steer calves and heifer calves.

Three types of cattle (Angus x Hereford yearling steers, Charolais x British breed steer calves and Hereford heifer calves) were evaluated for their response to different feeding systems utilizing high moisture corn, corn silage and soybean meal as major feed ingredients. Feeding ing systems for steers included: A = 85% concentrate; B = 40% concentrate; C = two phase, with switch from all corn silage to 85% concentrate in the middle of the feeding period; D = same as C except switch occurred late in the feeding period; E = all corn silage continuously. Heifer diets consisted of the following ratios of corn silage to concentrate: low energy = 89:11; medium energy = 67:33; and high energy = 100 fed at a moderate (10.9% for low energy and medium energy, and 11.7% for high energy) and high (13.8%) crude protein level. Treatments within each experiment were terminated at approximately the same final weight. Increasing percentage corn added to the total diet increased ADG in most comparisons. Adjusted to a constant carcass weight, increasing dietary energy increased fat thickness and reduced percentage retail product with no effect on quality grade in yearling steers and heifer calves. In Charolais cross-steer calves, increasing energy level increased quality grade with no effect on yield grade or percentage retail product. Energetic efficiency slightly favored system C in yearling steers while steer calves maximized efficiency on A. Hereford heifers were the most energetically efficient on medium energy diets.

Stage of Lactation as a Criterion for Switching Cows from One Complete Feed to Another during Early Lactation

Holstein (91) and Brown Swiss (29) cows were group-fed high (1.98) or medium (1.78 Mcal of net energy Lactation /kg of dry matter) energy complete feeds ad libitum during the first 24 wk of lactation. Feeds consisted of corn silage, alfalfa haylage, ground shelled corn, and soybean oil meal mixed in least-cost combinations to provide 16% crude protein. Weeks on high, and weeks on medium energy diets were (1) 1 to 24, and 0; (2) 1 to 16, and 17 to 24; (3) 1 to 8, and 9 to 24; (4) 1 to 8, and 9 to 24; (5) 1 to 16, and 17 to 24; (6) 0 and 1 to 24. Means for groups 1 to 6 were daily milk−22.1, 22.6, 23.1, 22.0, 21.4, and 21.6kg/cow; daily 4% fat-corrected-milk−21.8, 21.9, 22.4, 21.0, 21.2, and 21.4kg/cow; changes in body weight +25.5, −1.2, −11.1, +24.2, +20.7, and +3.5kg/cow. Cows consuming high energy diet produced more milk during the first 8 wk. There were no significant differences in daily production of milk or 4% fat-corrected-milk. Cows switched from medium to high after 8 wk ranked first for persistency of daily milk during wk 17 to 24 of lactation. Cows receiving high energy diets initially lost less weight in wk 4 to 8, and those receiving high energy diets after 8 wk gained more weight, especially during weeks 16 to 24, than cows receiving medium feed.