Nonpregnant Holstein Cows Research Articles

Decreased Insulin Response in Dairy Cows Following a Four-Day Fast to Induce Hepatic Lipidosis

Negative energy balance has been implicated in the development of fatty liver, insulin resistance, and impaired health in dairy cows. A 4-d fasting model previously was reported to increase liver triglycerides more than 2.5-fold. The purpose of the present study was to evaluate insulin response in this fasting model. Nonlactating, nonpregnant Holstein cows were fasted for 4 d (6 cows) or fed continuously as control cows (4 cows). Samples were collected 5 d before fasting, during fasting, and immediately after the 4-d fast, 8 d after the fast, and 16 d after the fast. Fasted cows had greater liver triglyceride content (49.4 vs. 16.2mg/g, wet-weight basis) at the end of the fasting period compared with control cows. Fasted cows also had increased plasma nonesterified fatty acid (NEFA) concentrations (1.24 vs. 0.21 mmol/L) and increased plasma β-hydroxybutyrate (BHBA) concentrations at the end of the fasting period. Liver triglyceride, plasma NEFA, and plasma BHBA in fasted cows returned to prefasting concentrations by the end of the experiment. Plasma glucose concentrations were not affected by fasting. Plasma insulin concentrations were decreased (6.3 vs. 14.1μU/mL) and insulin-stimulated blood glucose reduction was decreased (24.9 vs. 48.6%) in the fasted cows compared with control cows at the end of the fast, indicating reduced insulin response. Insulin response was negatively correlated with plasma NEFA and liver triglycerides. Decreased insulin response may be an important complication of negative energy balance and hepatic lipidosis.

Effect of transfer of one or two in vitro-produced embryos and post-transfer administration of gonadotropin releasing hormone on pregnancy rates of heat-stressed dairy cattle

Pregnancy rates following transfer of an in vitro-produced (IVP) embryo are often lower than those obtained following transfer of an embryo produced by superovulation. The purpose of the current pair of experiments was to examine two strategies for increasing pregnancy rates in heat stressed, dairy recipients receiving an IVP embryo. One method was to transfer two embryos into the uterine horn ipsilateral to the CL, whereas the other method involved injection of GnRH at Day 11 after the anticipated day of ovulation. In Experiment 1, 32 virgin crossbred heifers and 26 lactating crossbred cows were prepared for timed embryo transfer by being subjected to a timed ovulation protocol. Those having a palpable CL were randomly selected to receive one ( n = 31 recipients) or two ( n = 27 recipients) embryos on Day 7 after anticipated ovulation. At Day 64 of gestation, the pregnancy rate tended to be higher ( P = 0.07) for cows than for heifers. Heifers that received one embryo tended to have a higher pregnancy rate than those that received two embryos (41% versus 20%, respectively) while there was no difference in pregnancy rate for cows that received one or two embryos (57% versus 50%, respectively). Pregnancy loss between Day 64 and 127 only occurred for cows that received two embryos (pregnancy rate at Day 127 = 17%). Between Day 127 and term, one animal (a cow with a single embryo) lost its pregnancy. There was no difference in pregnancy rates at Day 127 or calving rates between cows and heifers, but females that received two embryos had lower Day-127 pregnancy rates and calving rates than females that received one embryo ( P < 0.03). Of the females receiving two embryos that calved, 2 of 5 gave birth to twins. For Experiment 2, 87 multiparous, late lactation, nonpregnant Holstein cows were synchronized for timed embryo transfer as in Experiment 1. Cows received a single embryo in the uterine horn ipsilateral to the ovary containing the CL and received either 100 μg GnRH or vehicle at Day 11 after anticipated ovulation (i.e. 4 days after embryo transfer). There was no difference in pregnancy rate for cows that received the GnRH or vehicle treatment (18% versus 17%, respectively). In conclusion, neither unilateral transfer of two embryos nor administration of GnRH at Day 11 after anticipated ovulation improved pregnancy rates of dairy cattle exposed to heat stress.

Blood melatonin and prolactin concentrations in dairy cows exposed to 60 Hz electric and magnetic fields during 8 h photoperiods.

Two experiments were conducted to test the hypothesis that electric and magnetic field (EMF) exposure may result in endocrine responses similar to those observed in animals exposed to long days. In the first experiment, 16 lactating, pregnant Holstein cows were assigned to two replicates according to a crossover design with treatment switchback. All animals were confined to wooden metabolic cages and maintained under short day photoperiods (8 h light/16 h dark). Treated animals were exposed to a vertical electric field of 10 kV/m and a horizontal magnetic field of 30 microT (EMF) for 16 h/day for 4 weeks. In a second, similar experiment, 16 nonlactating, nonpregnant Holstein cows subjected to short days were exposed to EMF, using a similar protocol, for periods corresponding to the duration of one estrous cycle. In the first experiment, circulating MLT concentrations during the light period showed a small numerical decrease during EMF exposure (P < .05). Least-square means for the 8 h light period were 9.9 versus 12.4 pg/ml, SE = 1.3. Melatonin concentrations during the dark period were not affected by the treatment. A similar trend was observed in the second experiment, where MLT concentrations during the light period tended to be lower (8.8 pg/ml vs. 16.3 pg/ml, P < .06) in the EMF exposed group, and no effects were observed during the dark period. Plasma prolactin (PRL) was increased in the EMF exposed group (16.6 vs. 12.7 ng/ml, P < .02) in the first experiment. In the second experiment, the overall PRL concentrations found were lower, and the mean plasma PRL concentration was not affected by treatment. These experiments provide evidence that EMF exposure may modify the response of dairy cows to photoperiod.

Responses of the estrous cycle in dairy cows exposed to electric and magnetic fields (60 Hz) during 8-h photoperiods

To study the effects of exposure to extremely low frequency (ELF) electric and magnetic fields (EMF) on the estrous cycle of dairy cows under short-day photoperiod, 16 non-lactating, non-pregnant Holstein cows were exposed to a vertical electric field of 10 kV/m and a horizontal magnetic field of 30 μT for 16 h per day in a cross-over design consisting of two sequences. Each sequence included three periods, and each period corresponded to the duration of one estrous cycle. All animals were maintained under short photoperiod (8 h light/16 h dark) during the trial. Exposure to EMF had an impact on the duration of a complete estrous cycle ( P<0.01) and on the duration of the luteal phase ( P<0.01). The mean duration of one cycle was 19.5±0.4 for the control and 21.3±0.4 days for the exposed animals, respectively. The mean duration of the luteal phase was 15.4±0.4 days for the control and 17.2±0.4 days for the exposed group. The total area under the progesterone (P 4) curve, the amplitude of the curve or the slope of the P 4 rise at the onset of the luteal phase were not affected by EMF exposure. Results indicate that exposure to EMF may increase the duration of the estrous cycle.

Functional Characterization of Mammary Gland of Holstein Cows under Humid Tropical Summer Climates

Physiological parameters were measured on six primiparous, non-pregnant Holstein cows prior to peak lactation over a 3-month summer season in southwestern Taiwan. The objectives were to characterize heat stress-induced change in functionality of mammary gland under natural climates of tropical summer and to establish physiological indices applicable to this environment in referring to this change. Environmental and physiological readings, milk and blood samples were taken at 15:00 h biweekly for totally five time points during the study. Climate readings showed that the afternoon humidex value reached the highest (53.5) around mid summer. Rectal temperature of cows taken simultaneously varied between 38.26°C and 40.02°C in parallel to humidex. Milk production declined drastically from 29.2 to 22.2 kg/d the first month entering summer but leveled up at end of the summer season suggesting effects exerted by heat stress rather than stages of lactation. Lactose content decreased linearly (p<0.05) with times in summer, from 4.69 to 4.38%. On the other hand, activity of N-acetylglucosaminidase (NAGase) in milk increased linearly to over two folds (p<0.05) during the same intervals. Elevations of fractional constituent of BSA in whey protein and serum cortisol level were also noticed in the course. Measurement of arteriovenous concentration (A-V) difference across the mammary gland demonstrated net uptake of glucose and net release of urea throughout the study period. The amount of urea released from mammary gland increased (p<0.05) progressively from 1.54 to 7.76 mg/dl during summer. It is concluded that gradual regression of mammary gland occurred along the humid tropical summer season. This regression is likely initiated through elevation of body temperature, which is irreversible above certain point. The increased release of urea from mammary gland during heat stress suggests its potential role as an early indicator of suboptimal mammary function. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 7 : 988-995)

The Effect of Ascorbic Acid and l-Histidine Therapy on Acute Mammary Inflammation in Dairy Cattle

Ascorbic acid and L-histidine were investigated as antioxidant therapies for acute mammary inflammation. Mastitis was induced in eight nonpregnant Holstein cows by intramammary infusion of endotoxin. Treatments were administered in a 4 × 4 Latin square crossover design with 1-wk periods between challenges with endotoxin. Four individual treatments, control, ascorbic acid only, L-histidine only, and ascorbic acid plus L-histidine, were applied. Two doses of 25g of ascorbic acid administered intravenously at 3- and 5-h postendotoxin challenge increased milk production recovery (9% higher, P<0.02) and tended to reduce the extent of rumen stasis. Two doses of 25g of L-histidine similarly administered decreased plasma antioxidant activities 5.5% (P<0.05). However, ascorbic acid and L-histidine had no effects on rectal temperature, heart rate, respiratory rate, and dry matter intake. The data suggested that ascorbic acid provided some potential benefit for recovery from acute mammary inflammation in dairy cattle.

Effects of Brown Midrib Corn Silage on the Energy Balance of Dairy Cattle

Effects of genotype and level of intake on net energy for lactation values of corn silage were evaluated by indirect calorimetry in two experiments using lactating and dry, nonpregnant dairy cows. In experiment 1, six multiparous Holstein cows in early lactation were fed experimental diets containing either brown midrib (bm3) or isogenic normal corn silage. Dietary treatments were isogenic and bm3 diets fed ad libitum, and the bm3 diets restricted-fed. Dry matter (DM) intake was 2.4 kg/d greater for cows fed the bm3 diet ad libitum compared with cows fed the isogenic diet. Apparent digestibilities of DM, organic matter, neutral detergent fiber, and acid detergent fiber were greater for cows restricted-fed bm3 than the isogenic diet. In experiment 2, six dry, nonpregnant Holstein cows were fed maintenance diets containing either bm3 or isogenic corn silage. Apparent digestibilities of DM, organic matter, neutral detergent fiber, and acid detergent fiber were greater for cows fed bm3 compared with isogenic corn silage. Digestible energy and metabolizable energy were greater for maintenance diets containing bm3 compared with isogenic corn silage, respectively. These data indicate increased milk production seen in other studies is a result of increased DMI rather than an increase in energy efficiency. Increased organic matter digestibility of bm3 corn silage resulted in greater digestible energy and metabolizable energy values in cows fed at maintenance energy intake. However, calculated net energy for lactation values of bm3 and isogenic corn silages were similar at both productive and maintenance levels of feeding.

Effect of ovarian steroids and oxytocin on the production of prostaglandin E2, prostaglandin F2alpha and endothelin-1 from cow oviductal epithelial cell monolayers in vitro.

Cyclic physio-anatomical variation in the oviducts is mediated by the local countercurrent transfer of ovarian products. Thus, in this study cow oviductal epithelial cells (COEC) culture were utilized to investigate the effects of ovarian products such as progesterone (P4), estradiol 17beta (E2) and oxytocin (OT) on local oviductal prostaglandin E2 (PGE2), F2alpha (PGF2alpha) and endothelin-1 (ET-1) production. COEC were collected from non-pregnant Holstein cows (n = 8) during the follicular phase and cultured in M199 under standard culture conditions until monolayer formation. Cells in first passage were incubated for 24 or 48 h with P4 (500 ng/ml), E2 (1 ng/ml), OT (10(-9) M) or combination of E2 + P4. Administration of E2 significantly increased the production of PGE2, PGF2alpha and ET-1. However, simultaneous administration of P4 blocked the effect of E2. OT did not show any effect on oviductal productions of either PGs or ET-1. The results of this study show that E2 stimulates PG and ET-1 production by COEC in vitro. Thus, it can be suggested that locally transferred E2 from the ovarian follicles may be important for oviductal contraction and gamete/zygote transport during the peri-ovulatory period.

Effect of Hot and Humid Conditions on Cortisol Levels m Lactating Dairy Cows

Fourteen lactating, non-pregnant Holstein cows were heat synchronized for estrus and assigned randomly to pens in a free stall barn with (Fan) or without (Control) a fan to observe the effect of forced ventilation on cortisol concentrations. After a 21-day adjustment period, Jugular cannulae were inserted for blood sampling before PGF2a injection. All animals were in their luteal phase at the time of injection as determined by previous observations for estrus and palpation. After PGFZa, blood samples were collected at 6-h intervals from 0 to 36h, 4-h intervals from 36 to 88h and 3 times weekly for three weeks thereafter. Blood samples were assayed for cortisol. Daily rectal temperatures and ambient data were recorded. Average daily rectal temperatures were lower (P&lt;0.05) in the Fan (39.1“C) than in the Control (39.5“C). Cortisol did not show a diurnal pattern and the values did not differ (P &gt;0.05) between treatment groups.

Ruminal Digestion and Duodenal Nutrient Flows in Dairy Cows Consuming Grass as Pasture, Hay, or Silage

The objective of this experiment was to quantitate ruminal digestion and flow of nutrients to the small intestine of Holstein cows grazing grass pasture or fed grass hay or silage. Three dry, nonpregnant Holstein cows fitted with ruminal and duodenal (Y-type) cannulas grazed or were given free choice access to hay or silage during three consecutive 19-d periods. Pasture intake was estimated using chromic oxide; hay and silage intakes were both measured and estimated. Intakes were similar among forages. Ruminal samples had higher VFA and ammonia when cows grazed than when cows were fed hay or silage. Ruminal pH did not differ. Based on duodenal spot sampling, cows on pasture had lower DM flows to the small intestine. Bacterial N flow, as a percentage of total N flow, was higher for cows that grazed. Most flows of AA to the small intestine were similar among forages, but Pro and Phe were lower for grazing cows. Supplementation strategies for cows on pasture should be designed to synchronize protein and carbohydrate in the rumen and to increase the supply of nutrients available in the small intestine.

Lipoprotein lipase and metabolic activities in incubated bovine adipose tissue explants: effects of insulin, dexamethasone, and fetal bovine serum

An in vitro system was used to study the regulation of lipoprotein lipase (LPL) activity in bovine adipose tissue. The utilization of two energetic and lipogenic substrates, acetate and glucose, and the activity of glucose-6-phosphate dehydrogenase (G6PDH), an enzyme involved in de novo lipogenesis, were also studied. Nine nonlactating, nonpregnant Holstein cows were given limited amounts of feed for 10 d, then they were overfed for 3 to 5 wk. Samples of perirenal adipose tissue were incubated for 24 or 48 h. Insulin (2 mU/mL) increased (P < .001) daily glucose and acetate utilization and attenuated (P < .001) the loss of G6PDH activity detected after 1 or 2 d of incubation. Dexamethasone (DEX, 10 nM) added to the insulin-supplemented medium decreased (P < .02) glucose utilization, but it did not change acetate utilization or G6PDH activity. A higher concentration of DEX (100 nM) potentiated (P < .004) the ability of insulin to attenuate the decrease in G6PDH activity without changing substrate utilization. Under basal conditions, LPL activity was decreased by approximately 66% after 2 d of incubation. The decline in LPL activity was attenuated by insulin addition (P < .02) and was further attenuated (P < .004) by 100 nM of DEX. The addition of 10% fetal bovine serum alone to the medium had no effect on LPL activity, and fetal bovine serum decreased this activity when it was added to the insulin-supplemented medium.

Induction of Estrus After Thyroidectomy in Nonlactating Holstein Cows

Hypothyroidism reportedly decreased sexual behavior in several species. To confirm the role of hypothyroidism in the expression of estrus in cattle, our objective was to determine whether estrus could be induced in ovariectomized cows without intact thyroid glands using estradiol benzoate and progesterone. Eight nonlactating, nonpregnant Holstein cows were thyroidectomized and ovariectomized, and another four cows were ovariectomized only. All cows were given either estradiol benzoate or progesterone plus estradiol benzoate in a crossover design with two replicates during 4 consecutive wk. Cows were observed continuously for estrus from 9 to 45h after treatment with gonadal steroids. Intensity of estrus was assessed by quantitative measurement of the frequencies of mounting activity and standing behavior. The percentage of cows showing estrus was influenced by thyroidectomy-ovariectomy (78.1%) compared with ovariectomy (31.1%) but was unaffected by hormonal treatment. In contrast, other measures of estrous behavior (duration of standing estrus and frequencies of mounting and standing activities) were unaffected by thyroid status or by hormonal treatments. We concluded that ovariectomized cows without intact thyroid glands exhibit estrus and that the exhibited behavior is similar in intensity and duration to that in ovariectomized cows treated with gonadal steroids. Hypothyroidism may not cause failure to express estrus.

Effects of Diets Magnesium on Acid-Base Status and Calcium Metabolism of Dry Cows Fed Acidogenic Salts

The objective was to study effects of dietary Mg on acid-base status and Ca metabolism of Holstein cows fed acidogenic diets with relatively high Ca concentrations. Eight nonlactating, nonpregnant Holstein cows were used in a switchback experiment with three 28-d periods. The normal Mg (.2%, dry basis) diet consisted of corn silage plus a concentrate mix supplemented with NH4Cl (126 g/d per cow) and (NH4)2SO4 (126 g/d per cow). The high Mg (.37%, dry basis) diet had MgSO4 substituted for an equivalent amount of s supplied by (NH4)2SO4 in the normal Mg diet. Cation-anion differences of the two diets were –302 (normal Mg) and –289 (high Mg) meq/kg of dietary DM. Compared with cows fed the normal Mg diet, those fed high Mg tended to have higher blood pH and plasma concentrations of total Ca but lower plasma concentrations of P and lower urinary excretion of ammonium and net acid. Cows fed the high Mg diet also tended to increase in urinary excretion with a decrease in urinary excretion of Ca. Metabolic responses to intravenous infusion of Na2-EDTA were similar among cows fed either diet. Results indicate that increasing salts was of no advantage with regard to Ca metabolism.

Induction of estrus in thyroidectomized-ovariectomized, nonlactating, Holstein cows (1992)

Low thyroid activity (hypothyroidism) has been reported to decrease sexual behavior associated with reproduction in several species. Using estradiol benzoate (EB) and progesterone (P ), we attempted to induce 4 estrus in hypothyroid cows. Thyroid glands (thyroidectomy) and ovaries (ovariectomy) were removed surgically from nonlactating and nonpregnant Holstein cows that were culled from the Kansas State University dairy herd. Eight cows were thyroidectomized and ovariectomized (THYOVEX) and another four cows were ovariectomized only (OVEX). Starting 9 hr after injection of EB, cows were continuously observed for estrus for 36 hr. Frequencies of mounting activity and standing behavior were recorded for each cow. The percentage showing standing estrus was greater in cows that had no thyroid glands or ovaries than in cows without ovaries (78 vs 31%). Manifestation of estrus was identical in cows treated with EB or EB+P (62%). Interval from 4 EB injection to onset of standing estrus, frequency of mounting activity, and duration of standing estrus were similar among treatment groups and unaffected by the type of hormonal treatment. Thyroidectomized cows can exhibit estrous behavior, which is similar to that in ovariectomized cows treated with EB or P +EB.; Dairy Day, 1992, Kansas State University, Manhattan, KS, 1992;

Screening of Anionic Salts for Palatability, Effects on Acid-Base Status, and Urinary Calcium Excretion in Dairy Cows

Six anionic salts [MgCl2·6H2O, MgSO4·7H2O, CaCl2·2H2O, CaSO4·2H2O, NH4Cl, and (NH4)2SO4] were evaluated for their effects on dietary DM intake, systemic acid-base balance, and urinary excretion of Ca. Each of the six salts was fed to 12 nonlactating, nonpregnant Holstein cows for l-wk periods in two replicates of a 6×6 Latin square design. All salts were fed at the rate of two equivalents cow–1 d–1. Anionic salt treatments did not decrease DM intake compared with the control diet fed without salts. Blood pH was not affected by any of the salt treatments; however, mild, compensated metabolic acidosis was evidenced by decreased blood bicarbonate concentrations and decreased blood base excess when any of the salts was fed. Urinary pH and urinary base excess also were lowered by all of the salts. Fractional excretion of urinary Ca was increased by all salt treatments. All six anionic salts tested were of similar value in their acidifying effects and in their ability to increase urinary excretion of Ca.

Secretory patterns of LH and FSH during development and hypothalamic and hypophysial characteristics following development of steroid-induced ovarian follicular cysts in dairy cattle

Two experiments were conducted to (1) investigate developmental endocrinology of ovarian follicular cysts (cysts) in cattle and (2) evaluate effects of cysts on hypothalamic and hypophysial characteristics. Cysts were induced with oestradiol-17 beta (15 mg) and progesterone (37.5 mg) dissolved in alcohol and injected s.c. twice daily for 7 days. Cysts were defined as the presence of follicular structures (which may or may not have been the same structure) of 2.0 cm in diameter or greater that were present for 10 days without ovulation and corpus luteum development. In Exp. 1,22 non-lactating, non-pregnant Holstein cows were allocated to 3 groups. Beginning on Day 5 (oestrus = Day 0) of the oestrous cycle, 7 cows (Controls) were treated with twice daily s.c. injections of ethanol (2 ml/injection) for 7 days. Luteolysis was then induced with PGF-2 alpha and blood samples were collected daily every 15 min for 6 h from the morning after the PGF-2 alpha injection (Day 13) until oestrus. Steroids to induce cysts were injected as previously described into the remaining cows (N = 15). Three blood samples were collected at 15-min intervals every 12 h throughout the experimental period. Additional blood samples were collected every 15 min for 6 h on a twice weekly basis. After steroid injections, follicular and luteal structures on ovaries were not detected via rectal palpation for a period of 36 +/- 4 days (static phase). Then follicles developed which ovulated within 3-7 days (non-cystic; N = 7) or increased in size with follicular structures present for 10 days (cystic; N = 8). Mean (+/- s.e.m.) concentrations of LH, FSH, oestradiol-17 beta and progesterone in serum remained low and were not different during the static phase between cows that subsequently developed cysts or ovulated. During the follicular phase, mean serum concentration of LH (ng/ml) was higher (P less than 0.1) in cows with cysts (2.9 +/- 0.2) than in cows without cysts (1.1 +/- 0.1) or control cows (1.4 +/- 0.2). In addition, LH pulse frequency (pulses/6 h) and amplitude (ng/ml) were higher (P less than 0.1) in cows with cysts (3.6 +/- 0.3 and 2.2 +/- 0.3, respectively) than in non-cystic (2.3 +/- 0.2 and 1.0 +/- 0.2, respectively) and control (1.8 +/- 0.1 and 1.1 +/- 0.2, respectively) groups during the follicular phase. There were no differences in the FSH, oestradiol-17 beta or progesterone characteristics in cows of any of the 3 groups during the follicular phase.(ABSTRACT TRUNCATED AT 400 WORDS)

In Vitro Production of β;-Hydroxybutyrate from 1,3-Butanediof by Bovine Liver, Rumen Mucosa, and Kidney

A model ketosis can be produced in dairy cows by restricting feed intake plus feeding 1,3-butanediol. Increases in D-β;-hydroxybutyrate in blood result from metabolism of the 1,3-butanediol, but the site of metabolism has not been established. In vitro production of D-β;-hydroxybutyrate from butyrate and from isomers of 1,3-butanediol was measured in bovine liver, rumen papillae, and kidney cortex, all obtained at slaughter from nonlactating, nonpregnant Holstein cows. Production of D-β;-hydroxybutyrate from butyrate by the tissues was greatest for liver and rumen and much less for kidney. Only liver, however, produced appreciable amounts of D-β;-hydroxybutyrate from R-, S-, or RS-1,3-butanediol, and rates were maximal at substrate concentrations of 5mM. Production of D-β;-hydroxybutyrate from R-1,3-butanediol by liver was greater than from S-1,3-butanediol. In vitro rates of production of D-β;-hydroxybutyrate were consistent with liver being the primary tissue involved in the metabolism of 1,3-butanediol, and capacity of the liver probably is sufficient to account for metabolism of 1,3-butanediol when 1kg is fed daily to dairy cows.

Effects of Amount of Whole Cottonseed on Intake, Digestibility, and Physiological Responses of Dairy Cows

In Experiment 1, 27 lactating cows were fed complete rations ad libitum of 0, 15, and 30% whole cottonseed to examine the effects on intake, digestibility, blood gases, and blood metabolites. Dry matter intake declined linearly with increased cottonseed, but because of greater energy density, calculated net energy for lactation intake was not depressed significantly. Ether extract, crude protein, and calcium digestibility increased with cottonseed in the diet. Respiration rates declined with dry matter intake and increased cottonseed feeding; some blood gases were influenced by cottonseed feeding but not in a detrimental way. No data among 13 blood metabolites indicated effects of gossypol toxicity with 30% whole cottonseed in the diet.In Experiment 2, 24 dry, nonpregnant Holstein cows were offered complete rations ad libitum of 15, 35, and 55% whole cottonseed to measure responses in intake, respiration rates, and blood metabolites. The highest cottonseed diet significantly depressed intake of both dry matter and calculated net energy for lactation. Maximum dry matter from cottonseed eaten by an individual was 8.4 kg/d (average for 1 wk). Respiration rates declined parallel to intake. No evidence for gossypol toxicity was seen among data of 11 metabolites in blood.

Effects of Sodium Hydroxide Treatment on Nutritive Value of Screened Manure Solids Fed to Dairy Cattle

This trial was to identify an effective method of increasing the nutritive value of screened manure solids by treatment with sodium hydroxide and to evaluate the effectiveness of this treatment. Treatments were applied in a 5×3 factorial design with five percentages of sodium hydroxide and three storage times. Treatment was followed by fiber analysis and in vitro digestibility determination. Based on this information three rations were formulated to contain 22% of screened manure solids either untreated, treated to contain 7% sodium hydroxide and fed immediately, or treated to contain 7% sodium hydroxide and stored 7 days prior to feeding. Chemical composition, intake, and digestibility of these complete rations were measured in a trial of 12 nonlactating, nonpregnant Holstein cows. Treatment reduced the hemicellulose content of the screened manure solids and increased digestibility of crude fiber and cellulose in the complete rations. Storage of treated material depressed digestibility of crude protein and soluble carbohydrate. Intake of organic matter was not different among the three rations. Untreated screened manure solids can be used successfully in complete rations for dairy cattle, but treatment with sodium hydroxide does not appear to be justified.

Effects of Ruminal Infusion of Acetic Acid onto Three Hay to Concentrate Ratios on Apparent Digestibilities and Rumen Parameters in Cattle1

Three pairs of mature, dry, nonpregnant Holstein cows were fed at maintenance diets of 80:20, 50:50 or 20:80 hay (chopped timothy) to concentrate (82% corn meal, 15% soybean meal, 3% limestone) and, using a balanced switchback design, were either infused via fistula or not with acetic acid to supply the equivalent of an additional 10% of maintenance. The infusate was delivered at a constant rate in 2 liters of aqueous solution over 20 hr per day by way of a stainless steel device that assured its delivery into the ventral rumen 4 to 6 cm from the mucosa. Apparent digestibilities of dry matter, organic matter, gross energy acid detergent fiber, nitrogen and nitrogen retention were unaffected by the acetic acid infusion. Neutral detergent fiber, cellulose and hemicellulose digestibilities were reduced by acetic acid infusion at 20:80 hay to concentrate ratio, but were unaffected at rations of 80:20 or 50:50. In rumen fluid, acetic acid concentration was increased and pH was reduced by the acetic acid infusion at all hay to concentrate ratios. Osmolarity, sodium and potassium concentrations were unaffected by acetic acid infusion. Concentration of propionate, i-butyrate, i- and n-valerate, but not n-butyrate, was reduced by acetic acid infusion. Over a feeding cycle from 7.00 am to 5:00 pm, acetic acid infusion did not affect the postprandial rise in concentration of any of the volatile fatty acids or total volatile fatty acids, the reduction in pH, or potassium concentration. Osmolarity and sodium concentration were unaffected by time over the feeding cycle or by acetic acid infusion. These results are discussed in relation to the use of intraruminal infusion of acetic acid to measure its partial efficiency for body tissue deposition in cattle.