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Biomedical subjects

J D Ferguson

Publications and source records attributed to J D Ferguson.

At least 37 records · Page 2Linked to original sources
PubMed1995

Application of linear programming in bull selection for a dairy herd.

Approximately 70% of dairy cows are inseminated with semen from bulls provided by commercial artificial insemination centers. To help producers in the selection process, artificial insemination centers publish information regarding production and type traits associated with each bull. Producers must decide from these lists which bulls to use, how often they are to be used, and to which cows they should be allocated. The bulls selected have a direct effect on cost of semen for the herd and genetic improvement in production of future generations. In general, producers' goals are to replace poor genes through strategic culling (not breeding certain cows) with better genes through semen purchases in an economically efficient manner. The cost of semen, however, is realized immediately, whereas economic returns from the traits selected are dependent on the realization of future cash flows. Higher production returns are needed to justify using more expensive bulls. The purposes of the study reported here were to examine the bull selection portfolio of a 450-cow commercial dairy herd in southeastern Pennsylvania and to use linear optimizing programming to select a genetically similar group of bulls at a much lower cost than that the producer had been using. This approach of dominant decision-making can be generalized and implemented for various dairy from conditions.

Animals↗
PubMed1995

Responses in urea and true protein of milk to different protein feeding schemes for dairy cows.

Four multiparous Holstein cows were used in a 4 x 4 Latin square to investigate the effects of protein concentration, degradability, and quality on plasma urea concentration and milk N constituents. Diets varied in the amount and proportion of RDP and RUP relative to NRC requirements: diet 1, excessive RDP, deficient RUP; diets 2 and 3, balanced for RDP and RUP; and diet 4, excessive RDP, balanced for RUP. Diet 3 was formulated for optimal AA balance as predicted by the Cornell Net Carbohydrate and Protein System. Diets contained 34% corn silage, 19% alfalfa haylage, and 49% concentrate (DM basis). Concentrates varied in amounts of urea and soybean, corn gluten, and fish and blood meals. Concentrations of urea N and NPN in milk varied among diets: diet 1, 19 and 34 mg/dl; diet 2, 16 and 31 mg/dl; diet 3, 15 and 30 mg/dl; and diet 4, 23 and 39 mg/dl, respectively. Increases in NPN concentration were attributed to increases in the urea fraction of NPN. Intake of RUP and AA balance influenced milk true protein content; diet 1, 2.89%; diet 2, 2.90%; diet 3, 3.01%; and diet 4, 2.95%. the proportions of true protein and urea in milk are influenced by CP concentration, protein type, and protein quality.

Animal Feed↗
PubMed1994

Relationships between administration of GnRH, body condition score and fertility in Holstein dairy cattle.

The objective of this study was to determine the effect of GnRH treatment in dairy cows differing in body condition score. A total of 2437 primiparous and multiparous cows was allocated randomly to receive either GnRH (100 microg) or placebo at the post partum exam (25 to 35 d) and at the first breeding. Complete records were available from 1906 cows: Group 1 (n = 535) placebo and placebo; Group 2 (n = 489) GnRH and placebo; Group 3 (n = 438) placebo and GnRH; and Group 4 (n = 444) GnRH and GnRH. The change of body condition score during early lactation was determined on a 1 to 5 scale (1 = emaciated to 5 = obese). Cows with a high body condition score (> or =3.0) at the first breeding had 8.8 fewer days to first service and 6.4 fewer days open but more services per conception (0.16) than cows with low body condition score (<3.0). Conception rate improved when GnRH was administered at the first breeding to cows with a body condition score of <3.0 at the first breeding regardless of parity. The administration of GnRH at the post partum exam decreased the conception rate in first lactation cows but was beneficial for cows in second and greater lactations. Thus the efficacy of GnRH may not be consistent in all parities and body condition groups.

Journal Article↗
PubMed1994

Principal descriptors of body condition score in Holstein cows.

The objective of this study was to assess objectively the ability of observers to assess body condition of dairy cows. Four observers independently assigned a body condition score (five-point scale, .25 increments) and described the appearance of seven body regions of 225 Holstein cows. Areas described were the thurl region, ischial and ileal tuberosities, ilio-sacral and ischio-coccygeal ligaments, transverse processes of the lumbar vertebrae, and spinous processes of the lumbar vertebrae. An absolute body condition score was designated for each cow based on the modal body condition score for all observers. If there was no modal body condition score, the mean score was used for the absolute body condition score. Statistical analysis of principal components was used to examine the relationship between body region description and absolute body condition score. Descriptions of body regions were highly correlated across all absolute body condition scores. Four principal component vectors explained 83.6% of the variation of the body region correlation matrix. The first principal latent vector accounted for 55% of the variation and was uniformly correlated with all body regions. Analysis of variance of first principal latent vector as the dependent variable and absolute body condition score as the class variable indicated that body condition could be separated into .25 units between 2.5 and 4.0, inclusively. Below 2.5 and > 4.0, body condition could only be separated by .5 units. Distinct changes in specific body regions were associated with change in absolute body condition score. Observers agreed with the absolute score 58.1% of the time, deviating by .25 units 32.6% of the time. A body condition score can be given to a cow based on principal descriptors of specific body regions between 2.5 and 4.0 by .25 units.

Adipose Tissue↗
PubMed1993

Serum urea nitrogen and conception rate: the usefulness of test information.

Total of 627 AI in 332 Holstein cows in nine herds were used to examine the relationship between serum urea N and conception rate. Cows were assigned randomly to one of three isocaloric diets varying in protein degradability and content. The AI occurred from 50 to 150 DIM. Mean serum urea N for each cow from 50 to 150 DIM was used to examine conception rate and serum urea N. The clinical interpretation of serum urea N on conception rate is evaluated using Bayes theorem from two approaches (dichotomization vs. continuous). Test information resulting from dichotomization of serum urea N into high and low categories (maximizing the average of test sensitivity and specificity) is compared with likelihood ratio approaches allowing a continuous measure. Likelihood ratio test indicates that conception rate decreases with serum urea N of > 14.9 mg/dl, but dichotomized test suggests that the decrease does not occur until serum urea N is > 20 mg/dl.

Animals↗
PubMed1992

Nonprotein nitrogen and protein distribution in the milk of cows.

The NPN content of milk represents only 5 to 6% of the total N in milk. However, the significance of this milk N fraction to energy and N metabolism in the dairy cow has not been well characterized. The single largest contributor to the NPN fraction of milk NPN is urea. Urea equilibrates in body water, and blood urea is the primary source of milk urea. The urea in milk can be derived from at least two sources: the end product of digestion and amino acid catabolism. Blood urea N was positively associated with intakes of ruminally degradable and undegradable protein and negatively associated with intake of net energy. Consequently, it might be possible to develop a system to evaluate the dietary protein and energy status of the lactating dairy cow employing milk urea in conjunction with milk true protein.

Animals↗
PubMed1991

Nutrition and reproduction in dairy cows.

Diagnosis of nutritional effects on herd fertility requires a systematic analysis of reproductive records in addition to quantifying the feeding program on the farm. Corroborative laboratory tests for specific deficiencies may be useful.

Animal Nutritional Physiological Phenomena↗
PubMed1991

New approaches to nutritional monitoring.

This article discusses new and innovative methods that can be used in the field to assess the economic value of ingredients in the production system. Methods to evaluate and monitor milk production responses are considered.

Animal Feed↗
PubMed1990

Economic evaluation of pregnancy diagnosis in dairy cattle: a decision analysis approach.

Cost-benefit evaluations of several pregnancy diagnosis schemes were performed. The strategy using on-farm milk progesterone test on d 19 after service, followed by treatment of nonpregnant cows with prostaglandin, was the most profitable returning $10.50 per cow above the cost of the intervention. An increase in efficiency of detection of estrus of greater than 20% among cows diagnosed nonpregnant and an error rate in pregnancy diagnosis of less than or equal to 3% were needed to ensure profitability. Pregnancy diagnosis by uterine palpation per rectum on d 35 after service, combined with the use of pressure-sensitive mounting devices on nonpregnant cows was the second most profitable strategy and returned $5.10 per cow. An increase in efficiency of detection of estrus of greater than or equal to 20% was required to ensure profitability. Embryonic mortality was also critical and an increase from a baseline value of 10% to 12%, as a result of early uterine palpation, made this scheme unprofitable ($-4.80 per cow). Pregnancy diagnosis by uterine palpation per rectum at 50 or 65 d was less profitable, with a return of $2.50 and $.10 per cow, respectively.

Animals↗
PubMed1990

Effects of hard fats on in vitro and in vivo rumen fermentation, milk production and reproduction in dairy cows.

Adding 0, 5, 15, and 20% of substrate as prilled or unprilled fatty acids [palmitic (47 to 48%), stearic (36 to 37%), and oleic (14%) acids] to an in vitro rumen fermenter had no effect on total VFA production. Acetate:propionate ratio was reduced by fatty acid concentrations of 15 and 20% (prilled and unprilled). In a 4 x 4 Latin square, increasing dietary prilled fatty acids (0, 3, 6, or 9% of DM) decreased DM intake, increased percentage of milk fat, and had no effect on percentage of milk protein. Milk volume and FCM increased with 3% but decreased with 6 and 9% dietary fatty acids. Rumen fluid acetate:propionate decreased with increasing dietary fatty acids. Holstein cows in three herds in Pennsylvania and Friesian cows in an Israeli herd were assigned randomly to receive, from 0 to 110 to 150 d postcalving, diets containing 0 or 2% of DM prilled fat. In Israel, dietary fat increased milk yield, FCM, and fat percentage during the first 90 d postcalving. In Pennsylvania, prilled fat had variable effects on milk composition and little effect on milk yield and FCM. Conception rate was improved in cows consuming rations containing prilled fat: first service, 59.1 versus 42.6%; all services, 59.3 versus 40.7%. The inclusion of prilled fat at 2% of DM in dairy cattle rations had slight effects on rumen fermentation, variable effects on milk yield and composition, and beneficial effects on conception rate.

Animals↗
PubMed1990

[The effect of gonadotropin releasing hormone (GnRH) and analogs on the conception rate in cattle. A critical literature review].

The objective of this article was to review the current literature of the influence of gonadotropin releasing hormone (GnRH) and GnRH agonists on conception rate in dairy cattle. The application of GnRH or agonists at artificial insemination (first and subsequent) and between days 7 and 34 after parturition were considered. The variations between studies were discussed as well as different mechanisms concerning the influence of GnRH for establishing pregnancy. From a critical point of view the routine use of GnRH or agonists at the time of first or subsequent breeding or during the postpartum period cannot be supported.

Animals↗
PubMed1989

Impact of protein nutrition on reproduction in dairy cows.

In most but not all published studies, feeding diets with high concentrations of crude protein decreased reproductive efficiency. We were able to resolve some of the inconsistencies among published reports by considering the fate of consumed protein in the rumen and then using logistic regression analysis to identify factors affecting pregnancy. Our models showed that type and amount of protein fed explained much of the variation in conception rate. Age and dietary concentration of energy were identified as modifiers of the impact of protein on reproduction. Protein nutrition can affect reproduction through toxic effects of ammonia and its metabolites on gametes and early embryos, through deficiencies of amino acids, and by exacerbations of negative balances of energy. Alterations in the hypothalamic-hypophyseal-ovarian axis may be responsible for many of the effects of protein on reproduction.

Animal Feed↗
PubMed1989

Effect of disease on days open assessed by survival analysis.

Survival analysis, a regression technique for analyzing data in which the time to an event is the measured outcome, was used to quantify the effects of five common herd diseases on days open in dairy cattle. Data were collected retrospectively from health and production records of 467 cows in five herds. In the 5-yr study period, 1059 lactations were followed to a conception or culling event. Retained placenta, nonsystemic metritis, systemic metritis, ovarian cysts, and lameness were associated with a decrease in conception rate and an increase in median days open. The hazard ratios for conception were .66, .83, .70, .70, and .69 and the increase in median days open 5, 15, 13, 22, and 28 d for the five diseases, respectively. Several attributes of survival analysis make it a valuable tool for quantifying days open in dairy cattle, including the ability to use reproductive information from observations which fail to conceive. Additionally, results obtained from survival analysis complement economic and decision analyses and will facilitate accurate cost assessment of suboptimal reproductive performance.

Animals↗