Biomedical subjects

M L McGilliard

Publications and source records attributed to M L McGilliard.

At least 19 recordsLinked to original sources

PubMed2002

Evaluating sire selection practices using lifetime net income functions.

Dairy farmers do not take full advantage of opportunities available for genetic improvement through use of artificial insemination, perhaps because economic advantages of good sire selection may not be fully recognized or understood. This study was undertaken to document differences between use of AI and non-AI bulls and to develop prediction equations to compare lifetime economic merit of future progeny from alternative sire selection policies. We describe the use of two methods of measuring lifetime economic merit, with and without adjustment for opportunity cost of a postponed replacement. Comparison of lifetime relative net income adjusted for opportunity cost on groups of cows sired by different kinds of bulls showed that daughters of proven AI bulls generated $148 and $120 more lifetime net income under fluid and manufactured milk market conditions than daughters of non-AI bulls. Daughters of proven AI bulls produced $60 more than daughters of AI young sires in progeny testing programs at the time of daughter conception. We developed prediction equations from combinations of genetic evaluations for production, productive life, SCS, and linear type traits on sires to predict lifetime relative net income of progeny produced from alternative sire selection strategies. Prediction equations explained 14 to 18% of variation in relative net income (not adjusted for opportunity cost), but herd and year of first freshening accounted for considerably more variation than did genetic evaluations on the sire of the cow. Finally, two independent data sets were used to develop and test predictions of lifetime relative net income adjusted for opportunity cost using genetic evaluations based on the eight traits included in the Merit indexes for the sire of each cow. Prediction equations from odd numbered herds were used to predict lifetime economic merit in even numbered herds and vice versa. Coefficients of determination ranged from 0.088 to 0.103 and averaged 0.004 higher than prediction equations with Net or Fluid Merit. Accuracy of predictions showed that Net and Fluid Merit were robust and useful indexes that accurately identified bulls whose daughters generated highest lifetime economic merit.

Animals↗

PubMed2000

Evaluation of reproductive performance in lactating dairy cows with prostaglandin F2alpha, gonadotropin-releasing hormone, and timed artificial insemination.

Nine hundred and twenty Holstein cows from 16 commercial dairy herds to evaluate three systematic breeding protocols: 14-d PGF2alpha, timed artificial insemination (AI), and GnRH-PGF2alpha, relative to AI following estrus detection without hormone intervention. The timed AI protocol involved GnRH, followed by PGF2alpha 7 d later and GnRH again 2 d after PGF2alpha, with AI 6 to 18 h after the second GnRH. The GnRH-PGF2alpha protocol consisted of GnRH followed by PGF2alpha 7 d later. Eight herds relied on visual observation to detect estrus, and eight herds utilized the HeatWatch estrus detection system. The average interval to first postpartum AI was shortest for the timed AI protocol (77.1 d) followed by the 14-d PGF2alpha protocol (81.6 d). There was no difference in days to first AI between the control (86.1 d) and GnRH-PGF2alpha (89.5 d) protocols. Percent pregnant per first AI did not differ among control (45.6%), 14-d PGF2alpha (43.7%), or GnRH-PGF2alpha (44.0%) protocols, but all protocols had a higher percent pregnant per first AI than the timed AI protocol (30.1%). Response to the GnRH-PGF2alpha protocol was limited because 44.0% of the cows submitted to the protocol were not detected in estrus < or = 10 d post-PGF2, administration and had an interval to first AI of 103.8 d. Cumulative percent pregnant by 120 d postpartum did not differ between control cows (53.1%) and hormonally treated cows (50.6%). Visual observation herds had a shorter interval to first postpartum AI (82.8 d) than the HeatWatch herds (84.8 d), with a higher overall rate of estrus detection across all protocols (75.3 and 67.6%, respectively).

Animals↗

PubMed1999

Effects of ultrasound-guided transvaginal follicular aspiration on oocyte recovery and hormonal profiles before and after GnRH treatment.

Endocrine changes and recovered oocytes were evaluated during 16 wk of ultrasound-guided transvaginal follicular aspiration (TVFA) and prior to and following administration of GnRH at the cessation of aspiration. Nonlactating previously aspirated (PAC, n = 4) and non-aspirated, (AC, n = 4) Holstein cows were subjected to 16 wk of twice-weekly aspiration. Four control cows (OAC) were aspirated 1 time only at the final TVFA session (wk 16). Jugular blood samples were collected from all cows during aspiration, before and after the final TVFA session, and during an 18-d period following cessation of aspiration. Ovarian activity was monitored in all cows after cessation of aspiration for 18 d. The PAC and AC cows averaged 3.4 +/- 1.2 (+/- SE) and 6.8 +/- 1.2 oocytes per session, respectively. Progesterone concentrations during TVFA did not differ between the PAC and AC (0.8 +/- 0.1 and 0.9 +/- 0.1 ng/mL, respectively). Progesterone concentration in OAC was 4.5 +/- 0.2 ng/mL before TVFA, while the PAC and AC averaged 0.5 +/- 0.2 and 0.3 +/- 0.2 ng/mL, respectively, at 16 wk. At Week 16 LH was 1.0 +/- 0.2 ng/mL and it increased to 7.5 +/- 0.1 ng/mL after GnRH treatment. The LH concentration before the final aspiration session was higher at peak amplitude in PAC than in AC groups and peak length was longer in OAC than in AC cows (P < 0.07). Between 18 and 24 h after the last aspiration there were more LH peaks and greater peak frequencies in PAC than in OAC cows (P < 0.07), and the interval between peaks was longer in PAC and AC cows (P < 0.10) than in OAC cows. Mean FSH concentrations were lower (P < 0.01) for OAC than for PAC and AC groups at 20 and 24 h after the last aspiration. Follicle numbers after GnRH varied most among treatment groups for follicles < 9 mm, with the PAC, AC and OAC averaging 5.1 +/- 1.0, 5.1 +/- 1.0, and 3.8 +/- 1.0 follicles/d, respectively. Progesterone concentrations increased to 1.1 +/- 0.3 ng/mL in PAC cows and 2.5 +/- 0.3 and 3.4 +/- 0.3 ng/mL in AC and OAC groups, respectively, during the 18-d period. These results suggest that long-term TVFA affects progesterone, LH and FSH profiles and ovarian dynamics in cows.

Animals↗

PubMed1998

Increase in milk yield of commercial dairy herds fed a microbial and enzyme supplement.

A microbial and enzyme supplement fed at 21.2 g/d per cow to 46 Virginia dairy herds increased the milk yield of 31 herds (17 significantly) and decreased the milk yield of 15 herds (7 significantly). Effects of season were important but consistent with overall results. Herds began receiving the supplement, which contained dried fermentation products of Aspergillus oryzae, Bacillus subtilis, Lactobacillus acidophilus, and yeast culture, midway between the first and second monthly Dairy Herd Improvement tests and continued on the supplement through the 3rd mo. Entry of herds was staggered over 8 mo to reduce the influence of season. The trial involved 3417 cows with 5 test mo between 60 and 365 d in milk. Milk yield during mo 3 averaged 0.64 kg/d per cow more (+0.73 kg/d for first lactation cows and +0.56 kg/d for later lactation cows) than the mean milk yield during mo 1 and 5. Herds completing the study before summer responded similarly to all other herds, which included herds that were fed the product during summer and those that finished the study during summer. Fat and protein yields and protein percentage differed little with or without the supplement. Fat percentage decreased (0.10%). Twenty-one herds that were fed a yeast product prior to and during the study responded similarly to the 17 herds that were not fed a yeast product.

Animals↗

PubMed1997

Effect of degradability of dietary protein and fat on ruminal, blood, and milk components of Jersey and Holstein cows.

Twelve Holstein cows and 12 Jersey cows were used in six 4 x 4 Latin squares to investigate the effects of the degradability of dietary protein and supplemental dietary fat on milk components. Dietary dry matter contained 16% crude protein with two concentrations of ruminally undegradable protein (RUP) obtained by substituting blood meal for a portion of the soybean meal. Treatments were 1) 29% RUP, 0% added fat; 2) 29% RUP, 2.7% added fat (Ca soaps of fatty acids); 3) 41% RUP, 0% added fat; and 4) 41% RUP, 2.7% added fat. The dry matter of the total mixed ration fed at 1000 and 1400 h consisted of 30% corn silage, 29% alfalfa haylage, and 41% concentrate. Supplemental dietary fat depressed dry matter intake by 6.2%. Plasma urea N was greater at 0700 and 1600 h for Jerseys fed diets containing added fat and greater at 0700 h for Holsteins fed diets containing 41% RUP than for Holsteins fed 0% added fat and 29% RUP. When averaged across both breeds, milk production increased 7.1%, and production of 4% fat-corrected milk by Jerseys increased 8.4%, in response to added dietary fat. Milk protein was reduced when Holstein diets contained 41% RUP. Milk protein content was reduced 7.1 and 3.9%, and milk urea N was increased 4.9 and 8.5%, by added fat and 41% RUP in both breeds, respectively. Added fat reduced the concentration, but not the yield, of milk components. Substitution of blood meal decreased the concentration and yield of milk protein and casein N.

Animals↗

PubMed1997

Influence of undergradability of protein in the diet on intake, daily gain, feed efficiency, and body composition of Holstein heifers.

Thirty-two Holstein heifers with body weights (BW) between 213 and 231 kg were randomly assigned to one of four treatments for the 50-d trial. Treatments consisted of four percentages of rumen-undegradable protein (RUP) (31, 43, 50, and 55% of total N) at 100% of National Research Council recommendations for total digestible nutrients and crude protein. Total mixed diets composed of corn silage, ground barley straw, soybean meal, blood meal, urea, and minerals were formulated for a mean daily BW gain of 0.60 kg. Ration RUP percentage was varied by shifting protein sources. Mean dry matter intake (grams per kilogram of BW0.75) was 97.6, 84.4, 77.8, and 73.5 for 31% RUP (soybean meal), 43% RUP (blood and soybean meal), 50% RUP (blood meal with urea), and 55% RUP (blood meal) treatments, respectively. Daily gain was 0.84, 0.89, 0.91, and 0.96 kg/d, respectively. Intake of digestible energy (megacalories per kilogram of BW0.75 per day) was 0.28, 0.24, 0.22, and 0.21, respectively, and feed efficiency (megacalories of digestible energy per kilogram of BW gain) was 20.6, 16.1, 15.2, and 13.3, respectively. Dry matter intake (grams per kilogram of BW0.75), digestible energy intake, feed efficiency, daily BW gain, and hip height differed with respect to treatment. There were no differences in growth, wither height, or heart girth because of treatments. Changes in percentage of empty body fat as estimated by urea space procedures was 6.73, 4.67, 6.67, and 7.32, respectively, and did not differ with respect to treatments. These results indicate that increasing the RUP percentage in the diets of growing heifers improves feed efficiency and increases BW gain.

Animal Feed↗

PubMed1997

Predicting ad libitum dry matter intake and yield of Holstein cows.

Two data files, one from New Hampshire (n = 3308) and one from Georgia (n = 678), containing 4-wk or weekly means, respectively, of ad libitum dry matter intakes (DMI) and related variables were used to predict DMI and yields of 4% fat-corrected milk and milk protein in lactating Holstein cows. The DMI ranged from 5.9 to 30.4 kg/d, and milk yield ranged from 5.8 to 64.3 kg/d. Because of the lack of data from < 14 d in milk, prediction was not possible for the first 2 wk of lactation. Factors considered for inclusion in the DMI prediction model were parity number (1 or > or = 2), treatment with bovine somatotropin (bST), day of year, days in milk, minimum (nighttime) temperature-humidity index, body weight, 4% fat-corrected milk yield, milk protein yield, and corn silage and total silage percentages in forage dry matter. In separate models, the silage predictors were replaced with more specific descriptors of ration dry matter, including percentages of crude protein, fat (ether extract plus soaps of fatty acids), concentrate, acid detergent fiber or neutral detergent fiber, and forage acid detergent fiber or neutral detergent fiber. The square and sometimes natural logarithm of predictors were included in models, which then were subjected to a stepwise backward elimination option of a multiple regression procedure. Several useful equations were developed to predict ad libitum DMI; the best models accounted for about 80% of the variability in DMI, and standard deviations were < 9% of mean DMI. Depression in DMI related to heat stress was higher in pluriparous cows than in primiparous cows (22% vs. 6%). The negative coefficient for effects of bST treatment on DMI suggested that milk yield increased proportionally more in response to bST than did DMI. About 74 to 77% of DMI predictions were within 2 kg/d of observed DMI.

Animals↗

PubMed1997

Diurnal variation in milk and plasma urea nitrogen in Holstein and Jersey cows in response to degradable dietary protein and added fat.

Four Holstein and four Jersey cows fitted with ruminal and duodenal cannulas were used in two 4 x 4 Latin squares to investigate the effects of varying protein degradability and supplemental fat on diurnal changes in plasma and milk urea N. Dietary dry matter contained 16.2% crude protein with two concentrations of ruminally undegradable protein (RUP) that were obtained by substituting blood meal for a portion of soybean meal. Treatments were 1) 29% RUP and 0% added fat, 2) 29% RUP and 2.7% added fat (Ca soaps of fatty acids), 3) 41% RUP and 0% added fat, and 4) 41% RUP and 2.7% added fat. Dry matter of the total mixed diet fed at 1000 and 1400 h consisted of 30% corn silage, 29% alfalfa haylage, and 41% concentrate. Ruminal ammonia, plasma urea N, and milk urea N were measured every 4 h over a 24-h period. Dry matter intake was depressed 6.7% by added fat. Ruminal ammonia was 25 to 45% lower when the 41% RUP diets were fed. Overall, the concentration of plasma urea N and milk components were not influenced by diet. However, milk urea N was higher in Holsteins than in Jerseys. Both plasma and milk urea N increased within 2 h after the 1000-h feeding followed by a decline at 6 h after the 1400-h feeding. In this short-term study, fat supplementation had no effect on milk production or yields of milk components. The inclusion of blood meal, however, increased the yields of milk components. Plasma and milk urea N did not differ among dietary treatments but varied throughout the day in relation to the time of feeding.

Ammonia↗

PubMed1996

Predicting ad libitum dry matter intake and yields of Jersey cows.

Two data files were used that contained weekly mean values for ad libitum DMI of lactating Jersey cows along with appropriate cow, ration, and environmental traits for predicting DMI. One data file (n = 666) was used to develop prediction equations for DMI because that file represented a number of separate experiments and contained more diversity in potential predictors, especially those related to ration, such as forage type. The other data file (n = 1613) was used primarily to verify these equations. Milk protein yield displaced 4% FCM output as a prediction variable and improved the R2 by several units but was not used in the final equations, however, for the sake of simplicity. All equations contained adjustments for the effects of heat stress, parity (1 vs. > 1), DIM > 15, BW, use of recombinant bST, and other significant independent variables. Equations were developed to predict DMI of cows fed individually or in groups and to predict daily yields of 4% FCM and milk protein; equations accounted for 0.69, 0.74, 0.81, and 0.76 of the variation in the dependent variables with standard deviations of 1.7, 1.6, 2.7, and 0.084 kg/ d, respectively. These equations should be applied to the development of software for computerized dairy ration balancing.

Animal Feed↗

PubMed1996

Time of ovulation relative to mounting activity in dairy cattle.

Time of ovulation was determined for Holstein cows (n = 51) for estruses occurring spontaneously (n = 33) or those induced by PGF2 alpha (n = 86). Ultrasound examination of ovaries was conducted 42 to 49 d postpartum, followed by administration of 25 mg of PGF2 alpha if a corpus luteum was observed. In the absence of a corpus luteum, ovaries were reexamined weekly, and PGF2 alpha was administered upon observation of the presence of a corpus luteum. Onset of estrus was determined by HeatWatch, an electronic pressure-sensing system that recorded each mount associated with estrus. To determine ovulation in relation to first detected mount, ultrasound examinations were conducted at 12, 20, and 24 h after the initial mount and then every 2 h until 40 h. Cows were assigned randomly to receive one of two treatments: 1) the cow received 25 mg of PGF2 alpha 8 to 13 d later or 2) the cow was allowed to cycle spontaneously and then was switched to alternate treatment at a third cycle. The mean estrus period, determined from mounting activity recorded by HeatWatch, consisted of 10.1 mounts over 9.5 h (6.0 mounts were > or = 2 s) for a total 24.1 s of mounting activity. Estrus characteristics were extremely variable and were not different for estruses induced by PGF2 alpha or for those occurring spontaneously. Mean ovulation time relative to first mount was 27.6 +/- 5.4 h and was not different between spontaneous and induced estruses. Knowing the time of ovulation in reference to the first mount of estrus and being able to identify the first mount consistently and accurately with the HeatWatch system allows for accurate timing of AI.

Animals↗

PubMed1994

Conception rates. 1. Derivation and estimates for effects of estrus detection on cow profitability.

Objectives were to derive equations and obtain estimates per cow of days to conception, milk production, semen purchases, calvings, and reproductive failures based on the probability of estrus detection and AI conception. The net benefits of changing rates of estrus detection, including changes in milk production, semen purchases, and replacement inventories (culled cows and calves) were converted to annual values and multiplied by fixed prices to obtain estimates of the annual financial benefit of a change in rates of estrus detection. Improvement in milk production because of a 1-d decrease in DIM at conception was dependent on DIM, peak milk production, and monthly rate of decline in daily milk production. Variation was considerable in expected benefits of improved estrus detection. Under the assumption that replacement was not planned prior to breeding (in which case improved estrus detection would have no value), estimated financial benefits for increasing the probability of estrus detection from 60 to 70% with a 70% AI conception rate were $6/yr; increasing from 20 to 30% the rate of estrus detection with a 50% AI conception rate increased estimated annual benefits to $83. This wide range of values occurred with fixed costs and prices so that fluctuating prices would introduce further variation in financial benefits. Derived equations allow point estimates of expected benefits with input values estimated.

Animals↗

PubMed1994

Conception rates. 2. Economic value of unit differences in percentages of sire conception rates.

The objectives of this research were to estimate 1) the annual increase in profitability and 2) the value of a unit of semen because of an increase of 1 in percentage of AI conception rate. Factors contributing to increased annual profit per cow included more milk production, less semen purchased, more calvings, and fewer reproductive cullings. With a 7% average monthly rate of decline in milk production between peak and end of lactation, $ .24/kg of milk net income over feed cost, $ 20/unit of semen, $ 150 per calving, and $ 400 per reproductive culling, values for increased annual profitability per cow ranged from $ .88 to $ 7.36, and increased value per unit of semen ranged from $ .60 to $ 5.01, when estrus detection and AI conception were each constrained to minima of 30% and maxima of 70%. Additional probability of concept was worth less at high rates of estrus detection and of AI conception. Within-herd variation can be attributed to differences between cows in milk production, asset value of the cow based on future expectations of milk production, and seasonal differences in milk price and rates of estrus detection. Further differences between herds can be expected as producers vary in discounting values for uncertainty of information. Therefore, generalizations from a single set of assumptions may be limited, and application of methods to specific cows and producers may be desirable.

Animals↗

PubMed1994

Timing of artificial insemination of dairy cows: fixed time once daily versus morning and afternoon.

Nonreturn rates to professional technician service of 7240 first AI Holstein cows were calculated to evaluate differences between once daily and a.m.-p.m. AI. To determine whether management practices affected nonreturn rates, participating herd owners were surveyed for methods used for detection of estrus. Nonreturn rates for once daily and a.m.-p.m. AI were 64.6 and 65.6% for 60-d, 60.1 and 60.6% for 75-d, and 58.4 and 57.8% for 90-d nonreturn periods. Signs of estrus for AI and interval from detection of estrus to AI were related to nonreturn rates. Nonreturn rate was highest, 63.4%, when cows were in standing estrus. Nonreturn rates were lowest, 36%, when cows were bred after treatment with PGF2 alpha without being detected in estrus or bred strictly on veterinary advice based on palpation. Nonreturn rates were similar for different times of the day when once daily AI was practiced. However, AI in the midmorning may have some advantages. The highest nonreturn rate for a 3-h period was 68.2% for 0800 and 1100 h; the lowest was 54.7% for 1300 to 1600 h. Movement before observation for estrus and an observation period > 15 min improved nonreturn rates for once daily AI. Once daily AI can be used effectively with no difference from the traditional a.m.-p.m. system; results are best when AI is based on standing estrus and performed between 0800 and 1100 h.

Animals↗

PubMed1993

Interactions of high milk yield and reproductive performance in dairy cows.

Correlations between reproductive traits and measures of milk yield indicate that higher yield is associated phenotypically and genetically with reduced reproductive performance in lactating cows. Numerous recent studies have reported that reproductive performance is compromised, primarily through delayed ovarian activity and reduced conception rates, by the demands of high milk yield. However, daily managerial decisions to obtain efficient reproductive performance have considerable impact. Management can offset depression in fertility, because high yielding herds often achieve the fewest days open. Selection for milk yield has increased blood concentrations of somatotropin and prolactin, stimulators of lactation, and decreased insulin, a hormone that is antagonistic to lactation and may be important for normal follicular development. These changes in hormone concentrations promote higher milk yield but may be potentially detrimental to other physiological functions, such as reproduction, if the management is not adequate to meet the metabolic demands of lactation. Timing and magnitude of negative energy balance apparently interact to determine the extent to which negative energy balance alters hypothalamic secretion of GnRH and its effect on gonadotropin secretion and, therefore, ovarian secretion of progesterone, which affects expression of estrus and support of the uterus during early pregnancy.

Animals↗

PubMed1992

Effect of progesterone supplementation in repeat-breeder cattle on conception and plasma progesterone.

Reposital-type progesterone (75 mg/d for cows, 40 mg/d for heifers) or saline were administered to 24 Holstein cattle to assess the effects of exogenous progesterone (P) on fertility in repeat-breeders. Treatments were administered daily from day 6 to 10 after fourth, fifth and sixth insemination. Cumulative conception rate (57.1%) for the fourth through sixth insemination was affected by lactation number, service number, plasma P (4.67 ng/ml for pregnant cows vs 4.06 ng/ml for nonpregnant cows) and corpus luteum size on days 5 and 15. Plasma P concentrations were affected by day of cycle and size of corpus luteum on both ovaries on day 15. A treatment by day interaction accounted for higher plasma P in P-treated cattle than saline-treated cattle from day 5 through 15. Administration of exogenous P during early life of the corpus luteum in the repeat-breeder increased plasma P. Higher plasma P was associated with insemination success.

Animals↗

PubMed1992

Estimating production benefits through simulation of group and individual feeding of dairy cows.

Objectives were 1) to develop DMI and milk prediction equations, 2) to use these equations to simulate group and individual feeding of dairy herds, and 3) to estimate effects of group and individual feeding on FCM production. University of New Hampshire data were used to predict DMI from previous DMI and cow and ration characteristics. The same data were used to predict milk production from DMI and previous milk production. Feeding was simulated for 100 cows over 50 4-wk periods in a number of trials. Effects of individual feeding, additional groups, herd calving intervals, and within-herd variation of annual milk production per cow on daily FCM per cow were isolated in average and high producing herds. Changing from one group to individual feeding can increase daily FCM per cow by .5 to 1.1 kg and two groups to individual feeding by 0 to .8 kg without changing total herd nutrient intake. Reallocation of the same amount of nutrients to two groups instead of one can increase daily milk production by .15 to .8 kg of FCM per cow, reallocation to three groups instead of two by 0 to .6 kg of FCM per cow, and reallocation to four groups instead of three by 0 to .35 kg of FCM per cow.

Animal Feed↗

PubMed1991

Effect of varying levels of neutral detergent fiber and total digestible nutrients on intake and growth of Holstein heifers.

Intake, growth, DM intake, BW, and wither height were recorded from 108 Holstein heifers weighing between 100 and 400 kg. Heifers were divided into two blocks based on beginning BW (mean = 182 kg, light and mean = 270 kg, heavy). Heifers within blocks were assigned randomly to one of five treatments for the 35-d trial to examine effects of dietary NDF and TDN on growth. Light heifer treatments were 35, 45, or 50% of NDF at 100% of NRC TDN recommendation and 85 and 115% of NRC TDN at 45% NDF. Heavy heifer treatments were 40, 50, or 60% of NDF at 100% NRC TDN and 85 and 115% of TDN at 50% NDF. Total mixed rations formulated for .68 kg/d of BW gain were fed. Rations contained corn silage, alfalfa haylage, ground orchardgrass hay, soybean meal, high moisture corn, and a mineral mix. Mean DM intake (kilograms per day) and BW (kg) were 5.9, 217 and 7.28, 311, respectively, for the light and heavy blocks. Mean BW gain (kilograms per day) and growth in wither height (centimeters per day) were 1.07, .122 and .96, .076, respectively, for light and heavy blocks. Maximal DM intake per kilogram of BW.75 occurred at 41% NDF, below which NDF and ADF correlations with DM intake per kilogram BW.75 were -.16 and -.42. Above 41% NDF, correlations were -.28 and -.21. Ration NDF content had more influence than TDN on intake and growth of heifers with less than 200 kg BW. Above 200 kg BW, heifer performance more closely reflected the changes in ration energy content (TDN); NDF had less effect.

Analysis of Variance↗

PubMed1991

Expert system for evaluation of reproductive performance and management.

A microcomputer expert system for dairy herd reproductive management was developed using an expert system shell and Turbo Pascal. The expert system initially examines the broad areas of days open, days to first breeding, detection of estrus, and conception rate to determine whether a problem exists. Interpretations ranging from "excellent" to "severe" were established for each trait. The system then selects an area for evaluation that has the largest negative influence on days open. Once an area has been selected for further evaluation, the expert system utilizes information from the user and DHI reports developed by the Dairy Records Processing Center in Raleigh, NC. These reports identify problems with conception categorized by production, parity, service number, days in milk, breed, and service sire. In addition, questions are presented by the expert system to isolate problems of accuracy of data, use of natural service, semen handling, AI technique, detection of estrus, signs of estrus, and other management areas. Recommendations and suggestions are given. Ten commercial herds having a conception rate less than 40% were evaluated by the expert system and by an extension reproduction specialist who supplied information for the system. Of 100 areas investigated, the expert system and extension specialist identified 47 as potential problem areas, agreeing on 85% of them. Most discrepancies resulted from the specialist applying a less restrictive standard when values were close to a preselected threshold.

Animal Husbandry↗