Biomedical subjects

D S Buchanan

Publications and source records attributed to D S Buchanan.

At least 19 recordsLinked to original sources

PubMed2003

Influence of milk production potential on forage dry matter intake by multiparous and primiparous Brangus females.

Brangus cows (n = 29) were used in three experiments to evaluate the effects of parity (multiparous vs. primiparous) and potential genetic merit for milk production (high vs. low) on forage intake during late gestation, early lactation, and late lactation. Cows were selected for milk production based on their sire's EPD for milk production (MEPD). Cows had ad libitum access to (130% of previous 2-d average intake) low-quality hay (5.3% CP and 76% NDF), and cottonseed meal was supplemented to ensure adequate degradable intake protein. All females were adapted to diets for at least 7 d, and individual intake data were collected for 9 d. During the lactation trials, actual milk production was determined using a portable milking machine following a 12-h separation from calves. During late gestation, multiparous cows consumed 24% more (P = 0.01) forage DM (kg/d) than primiparous cows; however, parity class did not influence forage intake when intake was expressed relative to BW. Furthermore, MEPD did not influence forage intake during late gestation. During early lactation, multiparous cows produced 66% more (P < 0.001) milk than primiparous cows, and high MEPD tended (P = 0.10) to produce more milk than low MEPD. Multiparous cows consumed 19% more (P < 0.0001) forage DM than did primiparous cows when expressed on an absolute basis, but not when expressed on a BW basis. High-MEPD cows consumed 8% more (P < 0.05) forage DM than did low-MEPD cows. During late lactation, multiparous cows produced 84% more milk than primiparous cows, although MEPD did not influence (P = 0.40) milk yield. In addition, multiparous cows consumed 17% more (P < 0.01) forage DM per day than primiparous cows, but when intake was expressed relative to BW, neither parity nor MEPD influenced forage DMI during late lactation. Milk yield and BW explained significant proportions of the variation in forage DMI during early and late lactation. Each kilogram increase in milk yield was associated with a 0.33- and 0.37-kg increase in forage DMI for early and late lactation, respectively. Results suggest that multiand primiparous cows consume similar amounts of low-quality forage DM, expressed per unit of BW, during late gestation and lactation. Selecting beef cows for increased genetic merit for milk production increases forage DMI during early lactation.

Animal Feed↗

PubMed2002

Efficacy of intramuscular treatment of beef cows with oxytetracycline to reduce mastitis and to increase calf growth.

Spring-calving multiparous Angus x Hereford cows were used to determine the efficacy of intramuscular treatment with oxytetracycline to reduce the incidence of mastitis-causing bacteria, decrease milk somatic cell counts (SCC), and increase calf growth. During 2 yr, milk samples were collected from each quarter from a total of 319 cows at 8 to 14 d after calving and at weaning, to determine the presence of bacteria and SCC. A California mastitis test (CMT) was performed on milk from each quarter of each cow at the initial sample collection. Cows with a CMT score of 1, 2, or 3 in at least one quarter, were randomly assigned to receive either an intramuscular injection of oxytetracycline (n = 63) or the control vehicle (n = 60), and cows with a CMT score of 0 or trace in all four quarters were not treated (n = 196). Calf weights were determined at birth, early lactation, and weaning. The number of somatic cells in milk and the percentage of quarters that were infected increased as CMT score increased (P < 0.01). The presence of mastitis-causing bacteria at calving increased (P < 0.05) the incidence of infection at weaning. The presence of mastitis-causing bacteria at weaning was associated with increased SCC for quarters and average SCC for cows (P < 0.01). Average SCC per cow at weaning increased (P < 0.05) as the number of infected quarters per cow increased. Treatment did not alter (P > 0.10) the percentage of cows or quarters infected with mastitis-causing bacteria or SCC of cows or quarters at weaning. Average SCC per cow was negatively correlated (P < 0.05) with calf weights at early lactation, but not with weaning weights of calves. Treatment did not influence (P > 0.10) calf weights at early lactation or at weaning. Cows with one or more dry quarters after calving had calves that weighed less at early lactation and weaning than cows with four functional quarters (P < 0.01). Intramuscular oxytetracycline treatment of beef cows that had CMT scores of 1 or greater after calving did not reduce intramammary infection rates or increase calf weights at weaning.

Animals↗

PubMed2001

Growth hormone response to growth hormone-releasing hormone in beef cows divergently selected for milk production.

In dairy cattle, increased circulating growth hormone has been associated with selection for greater milk yield. This study tested the hypothesis that beef cows divergently selected for milk production would have differing GH responses to a challenge dose of GHRH. Growth hormone response to a challenge of GHRH was measured in 36 Angus-sired cows ranging from 6 to 10 yr of age. The cows were classified as high milking (n = 16) or low milking (n = 20), on the basis of their sires' milk EPD. Mean milk EPD (in kilograms) were 16.6 and -14.4 for high and low milking cows, respectively. Milk production was estimated by the weigh-suckle-weigh procedure. Blood samples were taken immediately before and 10 min after a clearance dose of 4.5 microg of GHRH/100 kg BW (injected i.v.) and, 3 h later, immediately before and 10 min after a challenge dose of either 1.5 or 4.5 microg of GHRH/100 kg BW. Each animal received both challenge doses, and the doses were randomly assigned across 2 d of blood collection. Serum concentrations of GH and IGF-I were measured by RIA. Serum IGF-I was measured in the baseline blood sample on d 1 of blood collection. A positive relationship (r = 0.35; P = 0.03) was observed between the cows' rankings for each dose of GHRH; that is, high responders to the low dose were high responders to the high dose. Growth hormone response to the 4.5 microg/100 kg BW challenge dose of GHRH was positively related to sire milk EPD (R2 = 0.09; P = 0.03). Response of GH to the 1.5 microg GHRH/100 kg BW challenge dose also tended to be related (P = 0.08) to sire milk EPD of high milking cows. In addition, IGF-I concentrations of high milking cows were inversely related (R2 = 0.24; P = 0.04) to sire milk EPD. Growth hormone response to GHRH challenge may have potential as an additional tool in the evaluation of milk production in beef cattle.

Animals↗

PubMed2001

Milk production of crossbred daughters of high- and low-milk EPD Angus and Hereford bulls.

Milk yield from 273 Angus- and Hereford-sired cows and preweaning performance of their calves were used to determine how accurately milk EPD of Angus and Hereford sires predicted milk production of crossbred daughters and subsequent calf performance. Mean milk EPD (kg) for high Angus (HA), low Angus (LA), high Hereford (HH), and low Hereford (LH) bulls (n = 41) selected as sires were +8.7, -6.2, +7.6, and -4.8, respectively. Cows calved in spring or fall from 1992 to 1997 and yielded a total of 660 records. Twenty-four-hour milk production of the cows was estimated by two weigh-suckle-weigh measurements at monthly intervals. The statistical model included breed, milk EPD level, sire of cow within breed and milk EPD level, year, season, cow age, calf sire, sex, and all two- and three-way interactions. Means were obtained for monthly milk production, total milk production, time and yield of peak production, monthly calf weights, monthly cow weights and body condition scores (1 through 9), and calf birth and weaning data. The least squares means for 24-h milk production (kg) of HA, LA, HH, and LH with P-values for high vs low, across breeds, were, respectively, as follows: mo 1: 6.9, 5.9, 7.1, and 5.7 (P < 0.01); mo 2: 7.2, 6.1, 6.9, and 5.7 (P < 0.01); mo 3: 6.1, 5.1, 5.1, and 4.3 (P = 0.01); mo 4: 6.1, 4.9, 4.9, and 4.8 (P = 0.01); mo 5: 4.8, 4.0, 4.2, and 3.8 (P = 0.01); mo 6: 4.7, 3.4, 3.2, and 3.0 (P < 0.01); and mo 7: 3.7, 2.5, 3.0, and 3.0 (P = 0.05). Least squares means for total milk (kg) were 911.4, 729.6, 758.0, and 664.2 (P < 0.01); for yield at peak (kg/d) were 7.0, 5.7, 6.1, and 5.2 (P < 0.01); for birth weight (kg) were 37.1, 37.9, 38.3, and 38.8 (P = 0.31); for 205-d weight (kg) were 237.3, 218.2, 222.2, and 214.1 (P < 0.01); for final cow weight (kg) were 482.4, 505.4, 509.5, and 511.7 (P = 0.11); and for final cow BCS were 4.9, 5.3, 5.1, and 5.2 (P < 0.01). The correlations of total production with the monthly productions were 0.52, 0.56, 0.52, 0.54, 0.35, 0.37, and 0.31 (P < 0.01) and were 0.12 with birth weight, 0.45 with 205-d weight, -0.12 with final cow weight, and -0.26 with final cow body condition score (all P < 0.01). Daughters of high-milk EPD sires produced more milk and weaned heavier calves than those of low-milk EPD sires at the expense of body condition. These results suggest that sire milk EPD are sufficiently associated with milk yield and calf performance to be useful tools in genetic improvement of preweaning performance.

Animals↗

PubMed1998

Plasma cholecystokinin-8 in pigs with divergent genetic potential for feed intake and growth.

Plasma cholecystokinin-8 (CCK-8) was studied in pigs with divergent genetic potential for feed intake. Differences in feed intake resulted from selection for either fast (line F) or slow (line S) postweaning gain. The hypothesis was that the relatively lesser feed intake in S versus F may be attributable, in part, to greater circulating concentrations of the putative satiety hormone CCK-8. In Experiment I, barrows from F (n = 23) and S (n = 19) were used to determine changes in CCK-8 associated with ad libitum feed consumption. Blood samples were collected after overnight feed deprivation, then periodically during a 2-hr feeding period. Averaged across sampling times, concentration of CCK-8 tended to be greater (P = 0.07) in S (6.70 pmol/l) than in F (5.06 pmol/l). Concentration of CCK-8 per unit of feed consumed (CCK-8/cumulative feed intake) was greater (P < 0.01) in S than in F during the first 30 min of the feeding period. In Experiment 2, plasma concentrations were determined for nine pairs (F, S) of the same barrows allowed an amount of feed equal to the previous ad libitum intake of the S barrow in the pair. Averaged across times, the difference between CCK-8 concentrations of S (11.65 pmol/l) and F (7.94 pmol/l) barrows was not significant (P = 0.18). A greater concentration of CCK-8 per unit of feed consumed in S than in F supports the hypothesis that satiety effects of CCK-8 may play a role in genetic differences between the lines for feed intake.

Animals↗

PubMed1998

Comparison of sire breed solutions for growth traits adjusted by mean expected progeny differences to a 1993 base.

Records on growth traits were obtained from five Midwestern agricultural experiment stations as part of a beef cattle crossbreeding project (NC-196). Records on birth weight (BWT, n =3,490), weaning weight (WWT, n = 3,237), and yearling weight (YWT, n = 1,372) were analyzed within locations and pooled across locations to obtain estimates of breed of sire differences. Solutions for breed of sire differences were adjusted to the common base year of 1993. Then, factors to use with within-breed expected progeny differences (EPD) to obtain across-breed EPD were calculated. These factors were compared with factors obtained from similar analyses of records from the U. S. Meat Animal Research Center (MARC). Progeny of Brahman sires mated to Bos taurus cows were heaviest at birth and among the lightest at weaning. Simmental and Gelbvieh sires produced the heaviest progeny at weaning. Estimates of heritability pooled across locations were .34, .19, and .07 for BWT, WWT, and YWT, respectively. Regression coefficients of progeny performance on EPD of sire were 1.25+/-.09, .98+/-.13, and .62+/-.18 for BWT, WWT, and YWT, respectively. Rankings of breeds of sire generally did not change when adjusted for sire sampling. Rankings were generally similar to those previously reported for MARC data, except for Limousin and Charolais sires, which ranked lower for BWT and WWT at NC-196 locations than at MARC. Adjustment factors used to obtain across-breed EPD were largest for Brahman for BWT and for Gelbvieh for WWT. The data for YWT allow only comparison of Angus with Simmental and of Gelbvieh with Limousin.

Animals↗

PubMed1997

Feasibility of the grandprogeny design for quantitative trait loci (QTL) detection in purebred beef cattle.

The grandprogeny design (GPD) was developed for dairy cattle to use existing pedigreed populations for quantitative trait locus (QTL) detection. Marker genotypes of grandsires and sons are determined, and trait phenotypic data from grandprogeny are analyzed. The objective of this study was to investigate the potential application of GPD in purebred beef cattle populations. Pedigree structures of Angus (n = 123,319), Hereford (n = 107,778), Brangus (n = 14,449), and Gelbvieh (n = 8,114) sire evaluation reports were analyzed to identify potentially useful families. Power of QTL detection was calculated for a range of QTL effects (.1 to .5 SD) and two Type I error rates (.01 and .001). Reasonable power (> .75) could be achieved using GPD in Angus and Hereford for QTL having moderate effects (.3 SD) on weaning weight and large effects (.4 to .5 SD) on birth, yearling, and maternal weaning weights by genotyping 500 animals. Existing Gelbvieh and Brangus families useful for GPD were limited, and reasonable power could be expected only for QTL having large effects on weaning or birth weights. Although family structures suitable for GPD exist in purebred beef populations, large amounts of genotyping would be required to achieve reasonable power, and only QTL having moderate to large effects could be expected to be identified.

Aging↗

PubMed1995

Plasma growth hormone, insulin-like growth factor I, and insulin-like growth factor binding proteins in pigs with divergent genetic merit for postweaning average daily gain.

Characteristics of growth hormone (GH), IGF-I, and IGF-binding proteins (IGFBP) were studied in gilts sampled from lines of pigs selected for either fast (line F, n = 14) or slow (line S, n = 14) postweaning ADG. Repeated blood samples were obtained from gilts (approximately 55 kg BW) during a period of feed deprivation and again during refeeding. Averaged across time, the difference in mean plasma GH concentrations of F and S gilts was not significant (7.7 vs 6.4 ng/mL; P > .20) during feed deprivation, and frequently, height, and amplitude of GH pulses did not differ (P > .25) for F and S pigs. Overall, F gilts had greater concentrations of plasma IGF-I than S gilts during feed deprivation (217.3 vs 145.1 ng/mL; P < .03). Across line, plasma IGF-I decreased (P < .01) during feed deprivation. Average GH did not differ (P > .40) for F and S gilts during the refeeding period. Average plasma IGF-I tended (P = .05) to be greater in F gilts than in S gilts during refeeding. Consistent with changes over time during feed deprivation, plasma IGF-I averaged across line increased (P < .01) in response to refeeding. Averaged across time (0 and 48 h refeeding), activity of IGFBP-2 (singlet band at 34 kDa) did not differ significantly (P = .17) in F and S gilts. However, there was a tendency (P = .13) for a line x time interaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Effect of divergent selection for postweaning average daily gain on front-end soundness of market-weight pigs.

A total of 975 barrows and gilts from lines divergently selected for postweaning ADG were evaluated for front-end structural soundness (scored on a scale from 1, extreme leg weakness, to 8, superior leg structure) at approximately 100 kg, as well as growth performance and backfat thickness. Selection was for either fast (line F) or slow (line S) ADG from 9 wk of age to 100 kg and was replicated in spring- and fall-farrowing groups. The cumulative divergent selection differential corresponding to the animals evaluated was .47 kg/d (approximately 5 standard deviations). There was a line x sex x farrowing group interaction (P < .05) for ADG. Pigs from F grew faster (P < .01) than pigs from S, but the difference between lines was greater in gilts than in barrows. This interaction between line and sex was more pronounced in the spring- than in the fall-farrowing group. Average daily feed intake was 23% greater (P < .01) for F pigs than for S pigs. Even though pigs from F consumed more feed than those from S, their relatively faster ADG resulted in a greater (P < .01) feed efficiency (gain/feed) in F than in S. There was a line x farrowing group interaction (P < .05) for average backfat thickness adjusted to 105 kg. Barrows and gilts from F had 3.9 and 8.3% greater backfat thickness than those from S in the fall- and spring-farrowing groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Magnetoencephalography and magnetic source imaging. Capabilities and limitations.

The advent of large-array superconducting biomagnetometer systems, including sophisticated operating and data processing electronics, has enabled practical patient studies evaluating the potential contribution of magnetoencephalography to clinical medicine. The superimposition of sources localized magnetically onto anatomic images, referred to as magnetic source imaging, has allowed physicians to conduct this evaluation in the content of their customary medical practice. This article summarizes the basic technology of magnetoencephalography and magnetic source imaging and includes brief descriptions of the various applications that are being studied with these new sensor systems, some of which are discussed in subsequent articles.

Brain↗

PubMed1994

Improved soybean protein sources for early-weaned pigs: I. Effects on performance and total tract amino acid digestibility.

Seventy-two Yorkshire pigs weaned at 21 d of age were allotted to one of seven treatments with different protein sources serving as the primary lysine source at the expense of dried skim milk. Protein sources were dried skim milk (DSM), two isolated soybean proteins (ISP), three soybean protein concentrates (SPC), and 48.5% soybean meal (SBM). Average daily gain (ADG) and feed efficiency (G:F) were greater (P < .05) for pigs fed the DSM diet, the two ISP diets, or the three SPC diets during the first 2-wk period than for pigs fed the SBM diet. Average daily feed intake (ADFI) during the 1st wk was lowest in pigs fed the SBM diet. During the 2nd wk on trial and for the first 2-wk period, ADFI among the dietary treatments was similar. Performance of pigs fed either the ISP diets or the SPC diets as the supplemental protein source was equal to the performance of those fed the DSM diet. Average daily gain, G:F, and ADFI during a subsequent 3-wk period were not affected by treatment. Dry matter (DM) and nitrogen (N) digestibilities were greater (P < .01) in pigs fed DSM, ISP, and SPC diets than in those fed the SBM diet. Apparent digestibility of DM, N, and amino acids (AA) improved from wk 1 to wk 2 postweaning in pigs fed SBM but not in those fed DSM. However, digestibilities of these nutrients were similar among pigs fed the DSM, ISP, and SPC diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1994

Improved soybean protein sources for early-weaned pigs: II. Effects on ileal amino acid digestibility.

Early-weaned gilts fitted with simple ileal T-cannulas were used to determine the effect of protein source on N and amino acid (AA) digestibility. The digestibilities of N and AA in 25- to 53-d-old pigs fed either dried skim milk (DSM), isolated soybean protein (ISP), soybean protein concentrate (SPC), or soybean meal (SBM) as the only protein source were determined. The pigs were fed semipurified diets formulated to contain 22% CP. Digestibility of N and overall essential amino acids (EAA) and nonessential amino acids (NEAA) both at the terminal ileum and over the total digestive tract of early-weaned pigs was greater (P < .01) by pigs fed the DSM, ISP, and SPC diets than by those fed the SBM diet. The ileal and total tract digestibilities for N and all AA except glutamic acid (P < .05) increased with increasing age of pigs. Digestibility both at the ileum and total digestive tract for lysine was greater (P < .01) in pigs fed the DSM diet than in those fed any of the soybean protein diets. Digestibility values over the total tract were greater than values estimated at the ileum, indicating a net disappearance of both N and AA in the hindgut. This study suggests that low digestibility of the first-limiting AA, lysine, may limit performance of pigs fed a SBM diet.

Amino Acids↗

PubMed1994

Effects of beta-hydroxy-beta-methyl butyrate on performance and carcass quality of feedlot steers.

Beta-hydroxy-beta-methyl butyrate (HMB), a compound formed during catabolism of leucine, was fed to 256 crossbred steers as 0 or .03% of diet dry matter. Effects on performance, carcass characteristics, and tissue composition were measured. Groups of 32 steers per diet were slaughtered after 105, 119, 133, and 147 d on feed. The HMB was fed to each group only during the final 82 d they were fed. Averaged across slaughter date, animal performance was not altered by HMB; however, an interaction between HMB and time on feed was detected. Feeding HMB increased (P < .01) daily gain of steers slaughtered at 105 d but decreased (P < .01) daily gain of steers slaughtered at 147 d. Steers fed HMB had numerically higher marbling scores that resulted in a trend toward higher carcass quality grades. Steers receiving HMB tended to have less (P < .08) s.c. fat and fewer steers with yield grades of 4 or greater (1.6 vs 4.7%). Supplementation of HMB to feedlot steers tended to increase (P < .07) the ratio of intramuscular fat to subcutaneous fat. Steers fed HMB had higher (P < .001) blood plasma concentrations of HMB (3.06 vs 1.70 mg/L) and lower (P < .03) blood plasma concentrations of cholesterol (108.4 vs 118.7 mg/dL). Feeding HMB tended to increase (P < .10) lipid content of the longissimus muscles of those steers slaughtered at 105 d.

Adipose Tissue↗

PubMed1993

An alternative to the biomagnetic forward problem in a realistically shaped head model, the "weighted vertices".

The "weighted vertices" (WV), an alternative in solving the biomagnetic forward problem (BFP) for a realistically shaped head (RSH) model are presented. This proposed approach differs from the others in the way some terms in the governing integral equations are defined. The effects that WV has on important issues such as the "auto solid angle" and "stability of equations" are discussed. Two variants of the WV approach, i.e., the "linear weight" and the "quadratic weight," have been developed, and comparison of results produced by these two approaches shows that the implementation of quadratic elements to evaluate the integral produces significant improvements. This study is done with a focus on magnetic rather than electric phenomena, so a homogeneous conductor has been used in the numerical example. However, the thoughts behind this proposed method can be easily extended for cases where inhomogeneous conductors are involved. Significant improvement in the accuracy of the forward problem has been observed by use of the WV approach.

Computer Simulation↗

PubMed1992

Cavernous haemangioma of the temporal bone.

Cavernous haemangioma of the temporal bone is a rare lesion and nearly always of limited extent. A case of a large and rapidly progressive temporal bone haemangioma in a child is presented. Negative angiography led to biopsy at which profuse and troublesome haemorrhage was encountered. Subsequent Red Blood Cell labelled scan demonstrated blood pooling in the lesion. The combination of positive RBC labelled scan and negative angiography can only occur in lesions in which blood pooling takes place, enabling biopsy with its hazards to be avoided. The tumour was resected using a skull base, infratemporal approach. Morbidity was minimal. There was no evidence of recurrence at a 15 month follow-up.

Child, Preschool↗

PubMed1992

Effect of days fed, carcass grade traits, and subcutaneous fat removal on postmortem muscle characteristics and beef palatability.

Angus x Hereford steers (n = 48) similar in frame size and in muscle thickness were allotted to eight groups (n = 6) of similar mean live weight for serial slaughter at 28-d intervals (0 to 196 d). Except for d-0 steers, which served as grass-fed controls, all steers were fed a high-concentrate diet during the finishing period. Upon slaughter, one side of each carcass was trimmed of subcutaneous fat in the wholesale rib region. Postmortem longissimus muscle (LM) temperature was monitored for each side during the 24-h chilling period. After quality and yield grade data were collected, rib steaks were removed and aged (7 d) and sensory traits of the steaks were evaluated. Most carcass grade traits increased linearly (P less than .01) with days on feed, whereas most sensory panel variables and marbling increased curvilinearly (P less than .05). Generally, after 56 d on feed, carcasses chilled at slower rates (P less than .05) with increased days fed. Taste panel tenderness, amount of perceived connective tissue, and shear force values peaked at 112 d and were slightly less desirable for cattle fed longer than 112 d (quadratic term, P less than .01). Postmortem muscle temperature at 2.5 h was the chilling time most highly correlated with tenderness values among untrimmed sides. Correlations for shear force with 2.5-h LM temperature, marbling score, days fed, fat thickness, and carcass weight were -.63, -.61, -.56, -.55, and -.53, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1992

Growth and carcass characteristics of pigs selected for fast or slow gain in relation to feed intake and efficiency.

Selection in pigs for either fast (line F) or slow (line S) postweaning gain was replicated in spring (SREP) and fall (FREP) farrowing groups. Littermate barrows were sampled from F and S during Generations 2, 3, and 4 of the SREP and Generation 3 of the FREP. Beginning at approximately 35 kg (OTWT), barrows were either allowed ad libitum access to feed (AL) or limited to a standard total feed intake (LIM). Blocks of the line x intake level factorial were removed from test and carcass data collected when the average weight of barrows in the block was approximately 110 kg. Carcass data were also collected on an additional barrow from each litter at OTWT to allow estimation of lean tissue gain per unit of feed consumed (LTFC) of tested barrows. In Generations 3 and 4 of the SREP, F-AL was greater (P less than .01) than S-AL for average daily intake and ADG; carcass backfat was greater (P less than .01) but LTFC tended to be less (P less than .10) for F-AL than for S-AL. When LIM was imposed in the SREP, F barrows gained faster (P less than .05) than S barrows in Generation 4, but across generation the lines did not differ for carcass backfat and LTFC was greater (P less than .01) for F than for S. In the FREP, F-AL was greater (P less than .05) than S-AL for average daily intake and ADG and was less (P less than .05) for LTFC, but F and S did not differ for these traits when LIM was imposed; carcass backfat of F was greater (P less than .01) than that of S by .46 cm under AL and .38 cm under LIM. Most of the response in ADG could be attributed to changes in intake, but results in Generation 4 of the SREP indicated that changes in efficiency had also contributed. Most of the additional intake in F vs S resulted in deposition of fat, probably due in part to the heavier weight of F-AL vs S-AL barrows.

Adipose Tissue↗

PubMed1992

Sodium bicarbonate or multielement buffer via diet or rumen: effects on performance and acid-base status of lactating cows.

Our objective was to compare the influence of dietary NaHCO3 and a multielement buffer on ruminal acid-base status and lactation performance of dairy cows. Five ruminally fistulated, primiparous and multiparous lactating Holstein cows averaging 123 +/- 21 d postpartum were assigned randomly to treatments in a 5 x 5 Latin square with 3-wk experimental periods. Treatments were a basal diet without supplemental buffers, with 1.5% NaHCO3 or 1.5% multielement buffer, or with NaHCO3 or multielement buffer solutions poured into the rumen via cannula at 2 h postfeeding. Addition of either buffer to the diet reduced ruminal fluid hydrogen ion concentration from 0 to 6 h postfeeding; only NaHCO3 reduced ruminal fluid acidity when dosed via the cannula. Addition of buffers via ruminal cannula appeared to retard the reduction in ruminal fluid acidity that normally occurs from 6 to 12 h postfeeding; this may have been related to a feedback mechanism inhibiting salivary buffer secretion. Buffering capacity of ruminal fluid tended to increase with buffer addition; the increase was greatest during infusion of NaHCO3. The ruminal fluid buffer value index increased by 4 units for control cows from early (0 to 6 h) to late (6 to 12) postfeeding; smaller increases were noted for addition of multielement buffer. This index was not different for NaHCO3 during these two intervals. Milk yield and DMI were not affected by buffer addition. Although milk fat content tended to be higher with the multielement buffer than with NaHCO3, it was not accompanied by the expected alterations in ruminal acid-base status. Therefore, this increase may be related to systemic effects of specific minerals in the multielement buffer rather than to a more stable ruminal environment. Based on the ruminal fluid buffer value index, NaHCO3 tended to maintain the most stable ruminal acid-base status.

Acetates↗