Master of Science

Master of Science

Data from the University of New Hampshire were used to analyze dry matter intake and milk production in Holstein dairy cows. Equations predicting 4% FCM and dry matter intake were derived from this data using ordinary least squares. Days in milk, available nutrients, calving date, and previous period 4% FCM accounted for 90% of the variation in 4% FCM for heifers and 93% of the variation in 4% FCM for cows with previous lactations. Days in milk, acid detergent fiber, calving date, and dry matter intake from the previous 28 day period accounted for 71% of the variation in heifer dry matter intake and 79% of the variation in dry matter intake for the older cows. First period dry matter intake was predicted from first period 4% FCM, cow body weight, and acid detergent fiber of the ration. The lower R² for the first period dry matter intake (41% for heifers and 43% for cows with previous lactations) indicated that dry matter intake for a cow within a lactation was much more predictable than dry matter intake between different cows. Rations were balanced for absolute amounts for simulated lactating cows using NRC requirements and 4% FCM and dry matter intake generated from the prediction equations. Relationships between 4% FCM and nutrient concentrations were determined for heifers and multiparous cows. These recommendations suggest maximum feeding of nutrients to groups producing at least 35 kg of 4% FCM daily. The effect of grouping and individual feeding on 4% FCM were analyzed. Independent variables included nutrient concentration, dry matter intake, groups, calving interval, variability of 305 day milk production within the herd, and level of feeding. Holding dry matter intake and nutrient concentrations constant, increasing the number of groups from one to two increased 4% FCM by 0%-3%, two groups to three groups by 0-2%, and three groups to four groups by 0-1%. Changing from one group to individual feeding increased 4% FCM by 2%-4% and two group to individual feeding increased 4% FCM by 0%-3%. The range of figures was influenced by herd production level, calving interval, and variability of within herd production. High variability of production favored additional groups, while high calving intervals favored individual feeding. To estimate expected change in profitability due to a change in grouping or feeding methods, multiply previous milk revenue by expected percentage change and subtract the increased cost of feeding. Feeding less than the group average for nutrients was not found conducive for increasing profitability. In fact, production response to protein suggested that the low producing groups in multiple group feeding systems should be increased in protein slightly. Individual feeding had the most potential for profitability, although group feeding compared favorably under some circumstances. If cows were grouped, a minimum of two groups was generally preferable. If the high producing group did not satisfy the needs of the high producing cows, or the drop in nutrients between groups was substantial, a three group system would appear more favorable. / Ph. D.

Infection of tall fescue (<i>Festuca arundinacea</> Schreb.) with the endophyte fungus (<i>Acremonium coenophialum</i>, Morgan-Jones and Gam) has been associated with toxicity symptoms observed in cattle. The overall objective was to investigate the influence of endophyte infection on growth and chemical composition of tall fescue and the toxicity of endophyte-infected (EI) tall fescue to cattle. In a greenhouse study with pairs of genetically identical EI and non-infected (NI) ‘Kenhy’ tall fescue clones, concentration of N, Ca, Mg, Al, B, Mn and Zn was higher and K and S was lower in NI, compared to EI tall fescue. Insect resistance was higher in EI, compared to NI. Yield and chemical composition of high and low EI tall fescue were measured at four growth stages (stockpiled, prebloom, bloom and regrowth after harvest at bloom), two sites (Glade Spring and Blackstone) and three rates of N fertilization (0, 40 and 80 kg/ha) in a field study. Tall fescue grown at Glade Spring was higher in N, Mg, Al, Cu, Fe and Mn, compared to Blackstone. Nitrogen fertilization increased N, Mg, Ca, B, Cu, Na, Zn and decreased NDF, ADF, cellulose, P and S concentration in tall fescue. Neutral detergent fiber, ADF, cellulose, lignin, Fe and Na were higher in low, compared to high EI tall fescue. Concentrations of Cu, Na and Zn in stockpiled and Ca, Cu, Na and Zn in bloom-cut tall fescue hay were below dietary requirements for 227-kg steers. A disc meter was also evaluated for use in predicting yield of tall fescue. The meter is useful for non-destructive estimation of yield. Three feeding studies were conducted with steers (6/treatment/year). Diets were orchardgrass/alfalfa hay, spring-cut EI tall fescue hay, spring-cut EI tall fescue silage and fall-cut EI tall fescue silage. Serum prolactin and cholesterol were depressed in steers fed fescue hay and silages, compared to steers fed orchardgrass/alfalfa hay. Differences in mineral composition of hay and silage were reflected in serum minerals in steers. Ergopeptine alkaloids in EI tall fescue may have contributed to the depression of serum prolactin. The spring-cut silage contained the highest concentration of ergopeptine alkaloids, compared to other diets. Steers fed the spring-cut tall fescue silage had the lowest basal and thyrotropin-releasing hormone stimulated prolactin compared to steers fed the other diets. / Ph. D.

Twenty first-calf heifers and 24 cows in their second or greater lactation were randomly assigned to 4 dietary treatments from day 15 to day 61 postpartum. Mixed diets consisted of corn silage, alfalfa haylage, orchard grass hay, and a pelleted concentrate. Concentrates were control (C), C + additional corn (H), C + 4% calcium stearate (S), or C + 4% tallow (T). C, S, and T contained 50:50 forage and concentrate dry matter and H contained 40:60. / Master of Science

Twenty-four cows in a production trial and 8 cows fitted with ruminal and duodenal cannulas were used in 4 x 4 Latin squares to investigate the effects of dietary protein degradability and supplemental fat on rumen, blood, and milk components. Diet dry matter contained 16% CP with two levels of rumen undegradable protein (RUP) obtained by substituting blood meal for soybean meal. Treatments were 29% RUP, 0% added fat; 29% RUP, 2.7% added fat (Calcium soaps of fatty acids); 41% RUP, 0% added fat; and 41% RUP, 2.7% added fat. Dry matter intake was depressed 6.2% by added fat. Plasma urea N (PUN) increased with added fat and 41% RUP, however greater changes were observed due to time of feeding. Milk production increased 7.1% in both breeds and 4% fat corrected milk increased by 8.4% in Jerseys fed added fat. Milk protein yield decreased in Holsteins fed 41% RUP. Milk protein content was reduced 7.1% by added fat and 3.9% by 41% RUP, and milk urea N (g/100g N) was increased by added fat and 41% RUP. Milk urea N followed PUN pattern throughout the day. Added fat reduced content, but not yield, of milk components. Blood meal substitution decreased content and yield of milk protein and casein N. / Master of Science

Data sets from six locations containing 631 dairy heifers and 5409 observations of individual dry matter intake (DMI) were used to develop an equation to predict DMI. Data were contributed by Pennsylvania State University, University of New Hampshire, Purina Mills, Kansas State University, University of Minnesota, and Virginia Tech. Objectives varied by location and trials within locations but all contained DMI (kg/d), BW (kg), age (wk), DM, and CP, and ADF percentages of ration DM. Daily gains (g) were calculated from consecutive BW. Season was expressed as sine wave of Julian day plus 60 d times Ï divided into 180. Average daily temperature, humidity, and wind data were collected from Minnesota and Virginia and analyzed with BW to determine their effect on DMI. Sire PTA milk, protein, and fat of heifers were recorded from all sources to determine the relationship of genetics with DMI. Diet measurements (DM, CP, and ADF percent of ration DM) were analyzed with BW to determine their impact on DMI. Two equations were developed using backwards elimination techniques. The first equation was: DMI = -12.63 + .0587(BW) - .0000264(BW2) - .000 12(BWxDM) - .000477(BWxADF) + .292(DM) - .00103(DM2) - .413(CP) + .01349(CP2) + .181(ADF) - .0025(DMxCP) - .00269(DMxADF) + .00509(CPxADF) with an R2 of .90. Because body weight and diet variables were highly correlated, a smaller model could be created with one diet variable. A smaller model would also be more practical to use if accuracy was not lost. Body weight and ADF were used for second model: DMI = -1.71 + .0429(BW) - .0000246(BW2) - .00023(BWxADF) + .032(ADF) - .00068(ADF2) with an R 2 of .87. Previous DMI prediction equations from Virginia Tech were validated using all data from other locations and had R2 of .90 and .84 with this data set. Body weight raised to the .53 power most accurately described the relationship of DMI and BW. Temperature and DMI had a quadratic relationship. Higher DMI were observed at extreme temperatures between -10 to 27° C. Humidity and temperature x humidity accounted for more variation of OMI than season and other environmental measures, but were not included in the small model due to availability of these measurements and they did not change OMI by .1 kg/SO. Sire PTA milk by groups showed differences among heifer groups although no trends were found. Dry matter percent and CP percent had linear and quadratic relationships with OMI. Maximum OMI plateaued between 75 and 950/0 OM and occurred at extreme percentages for CP between 9 and 27%. Acid detergent fiber percent had a negative linear relationship with OMI between 7 and 45%. / Master of Science

Studies were conducted to: (1) examine an in situ technique with sorghum grain substrates using monofilament nylon bags, (2) evaluate in vitro various reconstituted sorghum grain treatments, (3) determine digestibility and nitrogen balance of steers fed reconstituted sorghum grain and (4) evaluate sorghum grain processing methods on performance of finishing steers. Dry matter efflux, DME (water bath) and in situ dry matter disappearance, ISDMD (ventral sac of rumen) from nylon bags were higher (P < .05) as bag porosity (5 to 80 um) and incubation time (4 to 24 h) increased, and as substrate weight: bag surface area ratio (7 to 56 mg/cm²) decreased. High linear correlations were obtained between DME and ISDMD, and also between nitrogen efflux and in situ nitrogen disapperance. No permanent influx of ruminal dry matter into nylon bags were detected. In vitro dry matter digestibility (mixed rumen inoculum) of reconstituted whole sorghum grain was influenced (P<.001) by grain moisture level (18 to 31%), constant or variable temperature during storage (-18 to 41 C) and length of storage time (3 to 28 d). All interactions of these three factors were significant (P<.05 or higher). Short term flushing with O₂, CO₂ and N₂ did not affect (P>.10) the digestibility of reconstituted whole sorghum grain. With reconstituted whole sorghum grain, grain pH could be used as a satisfactory measure of quality control. Apparent digestion coefficients for dry matter, organic matter, protein and energy were similar (P>.05) for steers fed 90% concentrate diets containing reconstituted whole or flaked sorghum grain. Nitrogen retention as a percent of nitrogen intake was 35% higher (P<.05) for steers fed reconstituted than flaked sorghum grain diets. In two finishing trials with steers, feed intake and feed conversion were higher (P<.05) for dry rolled than for flaked or reconstituted sorghum grain.

We conducted two experiments evaluating perennial ryegrass straw as a forage source for ruminants. Experiment 1 evaluated digestion and physiological variables in steers offered perennial ryegrass straw containing increasing levels of lolitrem B. Sixteen ruminally cannulated Angus X Hereford steers (231 ± 2 kg BW) were blocked by weight and assigned randomly to one of four treatments (TRT). Steers were provided perennial ryegrass straw at 120% of the previous 5-d average intake. Prior to straw feeding, soybean meal (SBM) was provided (0.1% BW; CP basis) to meet the estimated requirement for degradable intake protein. Low (L) and high (H) lolitrem B straws (<100 and 1550 ppb, respectively) were used to formulate TRT diets: LOW (100% L); LOW MIX (67% L:33% H); HIGH MIX (33% L:67% H); HIGH (100% H). Intake and digestibility of DM and OM, and ruminal pH, total VFA, and NH₃-N were not affected by increasing lolitrem B concentration (P>0.13). Ruminal indigestible ADF (IADF) fill increased linearly (P=0.01) and IADF passage rate (%/h) decreased linearly (P=0.04) as lolitrem B level increased. Experiment 2 evaluated performance and production of 72 Angus X Hereford cows (539 ± 5 kg BW) consuming perennial ryegrass straw containing increasing levels of lolitrem B during the last third of gestation. Cows were blocked by body condition score (BCS) and randomly assigned to one of three TRT. Cows were provided perennial ryegrass straw ad libitum and supplemented with SBM (0.1% BW; CP basis) to meet the estimated requirement for degradable intake protein. Mixtures of a L and H lolitrem B straw (467 and 2017 ppb, respectively) were used to formulate TRT diets: LOW (100% L); MIX (50% L:50% H); HIGH (100% H). Thirteen of 24 cows on the HIGH TRT exhibited signs of ryegrass staggers and were removed from the study. Dry matter intake was not affected (P>0.12) by increasing lolitrem B concentration; however, estimated DM digestibility decreased linearly (P<0.01) as lolitrem B concentration increased. Lolitrem B concentration did not influence pre- or post calving weight or BCS change (P>0.10). These data suggest that feeding perennial ryegrass straw containing up to 1550 ppb lolitrem B does not adversely affect nutrient digestion or physiological response variables in steers. However, providing straw with a lolitrem B concentration of approximately 2000 ppb resulted in 54% of cows exhibiting signs of ryegrass staggers. Blending of H and L straws appears to be a successful management practice. Keywords: Alkaloid, Beef Cattle, Endophyte, Lolitrem B, Perennial Ryegrass, Straw / Graduation date: 2004

Kikuyu pasture (Pennisetum clandestinum) is potentially the most important source of roughage used to feed dairy heifers in summer in KwaZulu-Natal. It is commonly believed that on kikuyu pasture beef breed females grow at a faster rate than those from dairy breeds when no supplementation is given. Little conclusive evidence is, however, available to support this. Explanations as to why such differences may exist are also limited. Eight Hereford and eight Holstein heifers of similar age and maturity stage were used in a trial. The trial was run over a twenty week period. For the first ten weeks all the animals in the trial grazed ad libitum kikuyu pasture with no supplementation except for a mineral lick. Over this (grass only) period the two breed groups formed the two treatments. During the second ten week period of the trial all of the Holsteins and four of the Herefords were fed a restricted but equivalent amount (1 .7 kg) of a maize meal based concentrate. The use of a computerized, mobile feeding system allowed concentrate intake of individual animals to be measured. Animal height, weight and condition score readings were taken weekly over the grass only and the concentrate (final seven weeks) periods of the trial. Herbage intake and digestibility were estimated using n-alkanes as indigestible markers in two experiments conducted during the grass only and concentrate periods. The Herefords had a significantly higher ADG than the Holsteins (0.82 vs. 0.04 kg/day; P < 0.01) over the grass only period. During the concentrate period the rate of mass gain of the Holstein treatment did not differ significantly (P >0.05) from the Hereford treatment receiving concentrate. The Herefords receiving concentrate were also not significantly different (P > 0.05) in rate of mass gain from the Herefords not receiving concentrate. Rate of height gain was not significantly different (P> 0.05) between treatments over either the concentrate or the grass only periods. During the grass only period the Holsteins lost condition (0.07 condition score units per week) whilst the Herefords gained condition at an equivalent rate. The voluntary intake of concentrates was not significantly different (P > 0.05) between the Herefords and Holsteins (19.19 vs. 16.40 g/kg/L.W(liveweight) (0.75)). Regression coefficients relating level of concentrate intake to rate of mass gain were also not significant (P > 0.05) for either of the treatments receiving concentrate. The use of n-alkanes as indigestible markers showed the intake of the Holstein treatment to have an intake 55% (P < 0.0 1) higher than the Herefords (185.4 vs. 120.5 g/kg L.W(0.75)) over the first experiment where both treatments were grazing ad lib. kikuyu alone (grass only period). During the concentrate period intake of the Herefords receiving concentrate exceeded that of the Holsteins (P < 0.01) by 23% (139.1 vs. 113.1 g/kg L.W(0.75)). Review of the literature, suggests that the double alkanes technique greatly over-estimated intake. Errors in herbage sampling (accentuated by pasture rotation in the first experiment), a low daily dose of the synthetic alkane (C(32)) and incorrect estimation of the C(32) content in the daily doses are identified as possible causes of the over-estimation of intake. Faecal recoveries of the herbage n-alkanes were demonstrated to increase with increasing chain length and hence C(35) was proposed as the most reliable herbage alkane for dry matter digestibility determination. Digestibility differences between treatments estimated using the C(35) alkane were not significantly different (P > 0.05) in either the first or second experiments. The mean digestibility estimates (using the C(35) alkane) for the first and second experiments were 64.9 and 56.61 %, respectively. In conclusion, higher growth rates of Herefords on kikuyu pasture would seem to be primarily due to differences in the dry matter intake of the grazed herbage. Further work using other breeds of dairy and beef animals is required. The underlying cause of differences in dry matter intake between breeds also requires investigation. / Thesis (M.Sc.Agric.)-University of Natal, Pietermaritzburg, 1995.