Effects of oral calcium supplementation on productive and reproductive performance in Holstein cows.

The objectives of this experiment were to determine the effects of oral Ca supplementation on milk yield, body condition, pregnancy per artificial insemination (P/AI), and days to pregnancy in Holstein cows considered to be of low (LRM; no calving assistance, live singleton without retained placenta) or high (HRM; at least one of the following: dystocia, twins, stillbirth, retained placenta, or vulvo-vaginal laceration) risk of developing metritis. The hypotheses were that oral Ca supplementation during the early postpartum period would reduce the loss of body condition and improve lactation performance and reproduction. Four hundred fifty Holstein cows were blocked by parity as primiparous cows (n=174) or multiparous cows (n=276). Within parity, a cow considered at HRM was matched with a cow of LRM and the pair was randomly assigned to control (no Ca supplementation), 86g of Ca on d 0 and 1 postpartum (CaS1), or 86g of Ca on d 0 and 1 postpartum followed by 43g/d on d 2 to 4 postpartum (CaS4). Body condition was scored at calving and 32 d postpartum and estrous cyclicity was evaluated at 38 and 52 d postpartum. Milk yield was recorded daily. Multiparous cows were classified as above or below the mean 305-d mature equivalent milk yield based on production in the previous lactation. Reproductive performance was evaluated for the first 210 d postpartum. Body condition did not differ among treatments, and cows lost on average 0.44 units of body condition in the first month of lactation. Calcium supplementation did not affect milk yield in the first 5 mo postpartum. For multiparous cows, Ca supplementation was beneficial to milk yield in the first 30 DIM in cows of greater production potential, but detrimental to multiparous cows with below average production potential. Calcium supplementation to primiparous cows reduced P/AI at first (control=55.8, CaS1=31.5, CaS4=37.0%) and all artificial inseminations (control=48.5, CaS1=34.6, CaS4=38.5%); however, Ca supplementation to multiparous cows improved P/AI at the first (control=32.1, CaS1=38.6, CaS4=41.3%) and all artificial inseminations (control=28.1, CaS1=35.3, CaS4=40.5%). These responses in P/AI to Ca supplementation resulted in extended median days to pregnancy (control=75, CaS1=100, CaS4=94 d) and smaller proportion of pregnant cows (control=89.3, CaS1=83.9, CaS4=83.9%) in primiparous cows, but shorter days to pregnancy (control=115, CaS1=94, CaS4=94 d) and increased proportion of pregnant cows in multiparous cows (control=67.0, CaS1=77.2, CaS4=74.3%). Risk of metritis depressed most measures of reproduction evaluated in the experiment. Results indicate that responses to oral Ca supplementation are conditional on parity and production potential of cows. Oral Ca supplementation was detrimental to reproduction in primiparous cows. On the other hand, Ca supplementation benefited reproduction in multiparous cows and milk yield in the cohort of multiparous cows of greater production potential.

Effects of oral calcium supplementation on mineral and acid-base status, energy metabolites, and health of postpartum dairy cows.

Two experiments were conducted to characterize blood concentrations of minerals and acid-base status after oral dosing of Ca salts and to determine the effects of oral Ca on mineral and metabolic status and incidence diseases. The hypotheses were that administration of oral Ca as CaCl2 and CaSO4 maintains blood total Ca (tCa) concentrations ≥2.125 mM and reduces the incidence of diseases in early lactation. In experiment 1, 18 Holstein cows on the day of calving were assigned to receive a single dose of 0, 43, or 86g of Ca as an oral bolus. Blood was sampled before and after treatments to characterize acid-base status and concentrations of minerals. In experiment 2, 450 Holstein cows considered of low (LRM; normal calving) or high risk (HRM; dystocia, twins, stillbirth, retained placenta, vulvo-vaginal laceration, or a combination of these) of metritis (primiparous-LRM=84; primiparous-HRM=84; multiparous-LRM=138; multiparous-HRM=138) on the day of calving were blocked by parity and then randomly assigned to control, no Ca supplementation; 86g of Ca on d 0 and 1 postpartum (CaS1); or 86g of Ca on d 0 and 1 postpartum followed by 43g/d on d 2 to 4 postpartum (CaS4). Blood was sampled before and 30 min after treatment on d 0, and 30 min after treatments on d 1 to 4, and d 7 and 10 for determination of concentrations of minerals and metabolites and blood acid-base responses. Disease incidence was evaluated for the first 30 DIM. Concentrations of ionized Ca (iCa) increased for 2h in cows supplemented with 43g of Ca and fewer than 8h in cows supplemented with 86g of Ca. The changes in iCa concentrations from pretreatment to 30 min after 86g of Ca supplemented on d 0 were 0.11±0.03 mM in multiparous cows and 0.25±0.03 mM in primiparous cows. Oral Ca reduced the incidence of subclinical hypocalcemia (SCH; tCa <2.125mM) in the first 4 d in the experiment (control=69.3%; CaS1=57.5%; CaS4=34.2%). Calcium supplementation decreased the prevalence of SCH on d 0 and 1 postpartum in all cows. Stopping oral Ca in CaS1 on d 1 postpartum, however, caused a rebound in SCH on d 2 to 4 postpartum in primiparous cows. Oral Ca increased the incidence of metritis (control=22.7%; CaS1=34.8%; CaS4=32.8%), primarily because of an increase in LRM primiparous cows (control=17.9%; CaS1=35.7%; CaS4=42.9%). Oral Ca increased morbidity in primiparous cows (control=38.1%; CaS1=61.8%; CaS4=60.3%) but had no effect on multiparous cows (control=38.2%; CaS1=35.1%; CaS4=30.1%). Large doses of oral Ca as salts of chloride and sulfate in the first days postpartum should be avoided in primiparous cows and used only in cows at risk of clinical hypocalcemia.

Effect of oral mineral and energy supplementation on blood mineral concentrations, energetic and inflammatory profile, and milk yield in dairy cows affected with dystocia.

The objectives of this study were to determine the effect of mineral/energy supplementation of dairy cows with dystocia on blood mineral concentrations, energetic and inflammatory profiles, and milk yield. Multiparous Holstein cows with dystocia were randomly assigned into two groups, (1) treated with a mineral/energy supplement (DME, n= 18) and (2) not treated (DNT, n= 22). A group of cows with normal parturition were randomly selected and were left untreated (NNT, n= 25). Cows in DME received an oral drench of 110 g of calcium and 400 g of propionate as calcium propionate plus 110 g potassium chloride and 150 g of magnesium sulfate administered within 6 h of calving and again 3 days post-partum. Compared to cows with a normal parturition, dystocic cows had decreased plasma calcium concentrations, increased plasma haptoglobin, decreased milk yield at 1 day post-partum, and tended to have increased rectal temperatures from 1 to 12 days post-partum. Compared with cows in DNT, those in DME had decreased plasma calcium concentrations and increased plasma magnesium concentrations 2 and 3 days post-partum, and a tendency for an increase in rectal temperature from 1 to 12 days post-partum. Dystocia is detrimental to calcium homeostasis post-partum, but mineral/energy supplementation as undertaken in this study is not recommended for use in cows with dystocia.

Effect of feeding maternal colostrum or plasma-derived or colostrum-derived colostrum replacer on passive transfer of immunity, health, and performance of preweaning heifer calves.

The objective of this study was to evaluate the effect of feeding maternal colostrum (MC), a plasma-derived (PDCR) or colostrum-derived colostrum replacer (CDCR) on passive transfer of immunity, health, and performance of preweaning heifer calves. Preplanned contrasts were performed for MC versus CR (PDCR combined with CDCR) and PDCR versus CDCR. At birth, calves were randomly assigned to 1 of 3 treatment groups: MC (n=49), 3.8L of maternal colostrum; PDCR (n=49), 550 g (1 dose; 150 g of IgG) of a PDCR; or CDCR (n=49), 470 g (1 dose; 100g IgG) of a CDCR. The best total protein cutoff for determining passive transfer was >5.2, 5.6, and 5.1g/dL for MC, PDCR, and CDCR, respectively. Serum total protein was greater for calves fed MC (mean ± SE; 6.14 ± 0.11 g/dL) than for calves fed PDCR (5.29 ± 0.11 g/dL) and CDCR (5.27 ± 0.11 g/dL). Serum IgG concentrations were greater for calves fed MC (2,098 ± 108 g/dL) than for calves fed PDCR (927 ± 107 g/dL) or CDCR (1,139 ± 108 g/dL). Apparent efficiency of absorption was greater for CDCR than PDCR (38.8 ± 3.0 vs. 21.6 ± 3.0%). Adequate passive transfer was greatest for MC (91.8%), followed by CDCR (49%) and PDCR (28.6%). Calves fed MC had greater weaning weights and body weight gain than calves fed CR. Morbidity was lower for calves fed MC (46.9%) than for calves fed PDCR (71.4%) or CDCR (67.3%). Calves fed MC tended to have lower mortality than calves fed CR. Given the conditions of this trial, feeding 3.8L of MC was superior to feeding one dose of CR. Further research is needed to evaluate calf performance when a higher dose of CR is fed.

Pre-partum monensin supplementation improves body reserves at calving and milk yield in Holstein cows dried-off with low body condition score.

The objective of this study was to determine the effect of a monensin controlled-release capsule administered intraruminally at drying-off on body condition score (BCS) at calving, milk yield, fertility and concentration of energy-related blood metabolites in Holstein cows dried-off with low BCS (< or = 3.0, scale 1 to 5 with a 0.25 point of increment). Between July and August, 2001, 220 cows from parity 2 or more and dried-off 50-70 days before expected parturition, with a BCS < or = 3.0 were randomly assigned to either a treatment group (n=110; oral capsule of monensin releasing 335 mg/day for 95 days) or a control group (no capsule, n=110). At assignment, on day 21 before expected parturition, at calving, and at 7, 14, and 21 days in milk a blood sample was obtained from a random sub sample of 10 cows per group. Effects of monensin on serum NEFA, BHBA and glucose were measured. Milk yield, milk fat and protein content (%) at DHIA test days during the entire lactation, 305 ME milk production and reproductive responses were compared. Monensin significantly improved BCS at calving, increased milk yield at test days 4 and 8, decreased the percentage of milk protein, did not change the percentage of milk fat, and decreased NEFA and BHBA during the post-partum period.

Effect of calcium-energy supplements on calving-related disorders, fertility and milk yield during the transition period in cows fed anionic diets.

The objective of this study was to determine the effect of a calcium-energy supplement at calving on the incidence of calving-related disorders (CRD), fertility, BCS and milk yield in cows fed anionic diets and to establish any associations among outcome variables. In Florida, from October to December 1997, 479 cows were assigned to three groups and treated at calving as follows: Group 1: 160 nontreated cows; Group 2: 158 cows, treated orally with 60g Ca as CaCl2; Group 3: 161 cows, treated orally with 110g Ca as calcium propionate (510g) plus propylene glycol (400g). No treatment effect was detected for any of the outcome variables. An association was found between dystocia and age and retained fetal membranes (RFM). Age and RFM were associated with metritis. RFM and displacement of the abomasum were associated with ketosis. Ketosis and age were related to displacement of the abomasum. Parity, BCS, ovarian cysts, RFM and metritis were associated with fertility.

Effects of gossypol from cottonseed meal and dietary vitamin E on the reproductive characteristics of superovulated beef heifers.

Superovulated Hereford-Angus crossbred heifers (average 397 kg BW) were used to test the effect of feeding cottonseed meal (gossypol) and vitamin E on embryo quality and ovarian characteristics. Twenty-four heifers were assigned randomly to four treatments with six heifers per treatment. Treatments were the following dietary supplements: 1) SBM (soybean meal + 30 IU vitamin E/kg of diet DM); 2) SBM+E (soybean meal + 4,000 IU vitamin E x animal(-1) x d(-1)); 3) CSM (cottonseed meal + 30 IU vitamin E/kg of diet DM); and 4) CSM+E (cottonseed meal + 4,000 IU vitamin E x animal(-1) x d(-1)). Supplements based on cottonseed meal provided 43.5 g of total gossypol/d (37% negative isomer (-) and 63% positive isomer (+)). Blood samples were collected at the start of the experiment and every 3 wk thereafter up to 12 wk. Plasma a-tocopherol (alpha-T) concentration was affected by treatments (P < 0.05). Heifers supplemented with cottonseed meal had greater (P < 0.05) alpha-T concentration in plasma than heifers supplemented with soybean meal at each concentration of vitamin E. Supplementation at 4,000 IU vitamin E x animal(-1) d(-1) increased (P < 0.05) the concentration of a-T in plasma. Weight gain, hemoglobin and hematocrit were not affected by treatment. Erythrocyte osmotic fragility (EOF) increased (P < 0.05) in cottonseed meal-fed animals; however, EOF was lowered (P < 0.05) with vitamin E supplementation. Heifers fed CSM and CSM+E supplements had greater (P < 0.01) concentrations of (-)-, (+)-, and total-gossypol in plasma, corpora lutea (CL), liver, and endometrium than heifers fed SBM and SBM+E supplements. Tissue alpha-T concentration increased with increased dietary supplemental vitamin E, particularly in great amounts in the CL. Because there was no adverse effect of gossypol on superovulation response or embryo development despite concentrations of gossypol in endometrium that are toxic to embryos, it is likely that systems exist in the reproductive tract to limit gossypol toxicity.

Metabolic responses of transition Holstein cows fed anionic salts and supplemented at calving with calcium and energy.

The objective of this study was to determine the concentrations of plasma Ca, P, Mg, nonesterified fatty acids (NEFA), 3-hydroxybutyrate (BHBA), and glucose in transition cows fed anionic salts prepartum and provided with calcium and energy supplements at calving. The study was conducted on a Florida Holstein dairy farm from November to December 1997. Treatments consisted of no treatment (n = 30); 60 g of Ca as calcium chloride, orally (n = 30); 110 g of Ca as calcium propionate 510 g plus 400 g of propylene glycol, orally (n = 30); two doses of 60 g of Ca as calcium chloride, one at calving and the second 24 h later, orally (n = 30); and 10 g of Ca as borogluconate, intravenously (n = 30). Treatments were administered within 12 h after parturition. Blood samples were collected at d 1 (parturition), 2, 3, 6, 9, and 12 after calving. Plasma total Ca, P, Mg, NEFA, BHBA, and glucose were measured. There were no differences in the concentrations of the blood metabolites among treatments.

Effects of gossypol from cottonseed on hematological responses and plasma alpha-tocopherol concentration of dairy cows.

The effects of feeding whole cottonseed (WCS) and bovine somatotropin (bST) administration on hematological responses and plasma alpha-tocopherol concentrations of lactating dairy cattle were examined. After parturition, multi and primiparous Holstein cows (n = 159) were assigned randomly to a 2 x 2 factorial arrangement of treatments consisting of (0 or 15% WCS and 0 or 208 mg of bST injected every 2 wk starting within 7 d after calving. Blood samples were collected from a subset group of 64 cows at 14, 28, 42, and 56 d postpartum. Blood was collected from all cows (n = 159) at 75, 96 and 120 d postpartum. Blood samples were analyzed for alpha-tocopherol and total and (+)- and (-)-gossypol in plasma. Erythrocyte osmotic fragility, hemoglobin and hematocrit also were determined in blood. The mean concentrations of alpha-Tocopherol, total, and (+)- and (-)-gossypol were higher in cows fed WCS regardless of bST administration and plateaued by d 75 postpartum. Hematocrit and hemoglobin concentrations were not affected by treatments. Erythrocyte osmotic fragility was higher in cows fed WCS, but the increase was attenuated when bST was injected (diet x bST interaction). No clinical signs of gossypol toxicity were observed in the cows consuming the WCS.

Effect of oral administration of a calcium chloride gel on blood mineral concentrations, parturient disorders, reproductive performance, and milk production of dairy cows with retained fetal membranes.

OBJECTIVE: To assess the effect of oral administration of CaCl2 gel on blood mineral concentrations, parturient disorders, reproductive performance, and milk production of dairy cows with retained fetal membranes (RFM). DESIGN: Randomized field trial. ANIMALS: 20 cows that calved normally and were not treated with CaCl2 gel (group 1), 20 cows with RFM that were treated with CaCl2 gel (group 2), and 20 cows with RFM that were not treated with CaCl2 gel (group 3). PROCEDURE: Group-2 cows were treated orally with CaCl2 gel (54 g of calcium) 24 and 48 hours after parturition. RESULTS: Administration of CaCl2 gel 24 and 48 hours after parturition did not have a significant effect on serum normalized calcium, total calcium, magnesium, or phosphorus concentrations or on incidence of metritis or left displacement of the abomasum, days to first insemination, pregnancy status after first insemination, or milk production. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of CaCl2 gel 24 and 48 hours after parturition did not have significant effect on blood mineral concentrations, parturient disorders, reproductive performance, and milk production in dairy cows with RFM.

Long-term effects of feeding gossypol and vitamin E to dairy calves.

Male Holstein calves were used to test the effect of feeding 400 mg of free gossypol/kg of diet and to determine whether vitamin E could counteract gossypol toxicity. Fifty-two calves were allotted to treatments as follows: 1) soybean meal-based starter; 2) cottonseed meal-based starter; 3) cottonseed meal-based starter + 2000 IU of vitamin E/d per calf, and 4) cottonseed meal-based starter + 4000 IU of vitamin E/d per calf. Vitamin E supplementation (treatments 3 and 4) improved weight gain and feed intake over calves on treatment 1. Gossypol concentrations in plasma were higher in calves on treatments 2, 3, and 4 than in calves on treatment 1; however, no differences were observed among animals receiving the three cottonseed meal diets. Hemoglobin and hematocrit were decreased in calves receiving treatment 2, and vitamin E supplementation counteracted this effect (treatments 3 and 4). Plasma alpha-tocopherol concentrations were not affected by gossypol intake and followed the vitamin E supplementation pattern During the experimental period, 10 calves died, six from treatment 2 and two each from treatments 3 and 4. Necropsy findings from 4 of 10 calves were suggestive of gossypol toxicity. Histopathological examination revealed centrilobular necrosis in the liver and atrophy and vacuolation of cardiocytes. Feeding cottonseed meal caused death of some calves with gossypol related toxicity signs, but did not decrease plasma alpha-tocopherol; however, vitamin E supplementation increased performance and may have conferred some protection against gossypol toxicity.

Effects on performance, tissue integrity, and metabolism of vitamin E supplementation for beef heifers fed a diet that contains gossypol.

We conducted an experiment for 112 d with yearling beef heifers to evaluate the effects of cottonseed meal (CSM) fed with various concentrations of vitamin E on hematological and tissue components. Heifers were assigned randomly to four treatments, with eight heifers per treatment. The treatments consisted of the following dietary supplements: 1) CON, based on soybean meal with 30 IU vitamin E/kg; 2) GOS, based on CSM with 30 IU vitamin E/kg; 3) G+2E, based on CSM with 2,000 IU vitamin E x animal(-1) x d(-1); and 4) G+4E, based on CSM with 4,000 IU vitamin E x animal(-1) x d(-1). Supplements based on CSM provided 4.5 g of free and 50.5 g of total gossypol x animal(-1) x d(-1). The total gossypol present in the supplements was 29.1% of the negative isomer (-) and 70.9% of the positive isomer (+). Blood samples were collected at the start of the experiment and every 2 wk thereafter up to 16 wk. There was a time x treatment interaction (P<.01) for plasma alpha-tocopherol ( alpha-T) concentration; however, feeding gossypol did not decrease plasma alpha-T. Weight gain, retinol palmitate, retinol, beta-carotene (beta-C), hemoglobin, and hematocrit were not affected by treatment. Erythrocyte osmotic fragility (EOF) increased (P<.05) in gossypol-fed animals; however, vitamin E supplementation lowered EOF (P<.05). Heifers fed the supplements GOS, G+2E, and G+4E had greater (P<.01) plasma (-)-, (+)-, and total gossypol than heifers fed CON from Collection 2 to the end of the experiment. There was a treatment effect (P<.05) on vitamin E and gossypol concentrations in different tissues, with no effect (P>.05) for trace minerals (Cu, Zn, Fe, and Se). Vitamin E concentration in tissue increased with increased dietary supplementation of vitamin E. In heart and neck muscle, (-)-gossypol was greater (P<.05) than (+)-gossypol, but the reverse was true for liver. Gossypol decreased in vitro lipid peroxidation of liver homogenate in tissues. Gossypol deposition in tissue was liver > heart > muscle. In summary, gossypol from CSM did not decrease concentrations of antioxidant vitamins, including alpha-T, vitamin A, and beta-C, or have any detrimental effect on performance of beef heifers.

Reproductive effects of feeding gossypol and vitamin E to bulls.

An experiment was conducted to determine the effects of long-term feeding of cottonseed meal on the reproductive traits of Holstein bulls. Holstein bulls approximately 6 mo of age were placed on the following treatments: 1) soybean meal + corn (CON); 2) cottonseed meal + corn (GOS); and 3) cottonseed meal + 4,000 IU vitamin E x bull(-1) x d(-1) (G+4E). The GOS and G+4E diets were formulated to supply 14 mg of free gossypol x kg(-1) BW x d(-1). These bulls had been in a previous experiment that evaluated the effects of feeding the same type of diets, but from 2 wk to 6 mo. of age. Percentage of motility, percentage of normal and live sperm, and daily sperm production were less (P<.05) in the GOS than in the other two treatments. Percentages of primary abnormalities and abnormal midpieces were greater (P<.05) in the GOS group than in the other two groups. At 12 and 16 mo. of age, bulls were given two assessments for sex drive traits. Bulls that received gossypol exhibited less sexual activity (P<.05) at the first test than bulls in other treatments. Vitamin E supplementation in bulls that received gossypol improved the number of mounts in the first test and the time to first service in the second test. There was a trend of gossypol to decrease and vitamin E to improve libido score. The results of the GOS first libido test may indicate lack of sexual maturity, which agrees with sperm production data. At the time of first test (12 mo. of age), none of GOS, two of CON, and six of G+4E bulls had reached puberty on the basis of experimental protocol. Long-term feeding of gossypol to Holstein bulls negatively affected some reproductive traits; however, vitamin E supplementation countered these adverse effects and even improved these traits.

Long-term effects of gossypol and vitamin E in the diets of dairy bulls.

Long-term effects of the inclusion of cottonseed meal in the diet on hematological and tissue parameters of Holstein bulls were investigated. Twenty-four Holstein bulls that were approximately 6 mo of age received the following treatments for 10 mo: 1) soybean meal plus 30 IU of vitamin E/kg, 2) cottonseed meal plus 30 IU of vitamin E/kg, and 3) cottonseed meal plus 4000 IU of vitamin E/d per bull. Treatments 2 and 3 were formulated to supply 14 mg of free gossypol/kg of body weight per d. Average daily gain, total gain, and final body weights were not affected by treatment. The osmotic fragility of erythrocytes was greater during all collection periods for bulls on treatments 2 and 3 than for bulls on treatment 1. The inclusion of 4000 IU of vitamin E/d per bull did not reduce the increase in the osmotic fragility of erythrocytes that was caused by gossypol. Bulls on treatment 3 had higher plasma alpha-tocopherol concentrations than did bulls on treatments 1 and 2. Vitamin E supplementation did not affect gossypol concentrations in plasma or tissue. The highest gossypol concentrations were found in the liver followed by the heart and testis. In vitro lipid peroxidation of tissue indicated that gossypol acts as an antioxidant in lipid peroxidation systems, and its role as an antioxidant may be dependent on dose or tissue. Cottonseed meal in the diets of bulls did not affect growth or vitamin E status.

Protein degradability and calcium salts of long-chain fatty acids in the diets of lactating dairy cows: productive responses.

Our objective was to evaluate the effect of excessive intake of ruminally degradable crude protein [11.1 and 15.7% of dietary dry matter (DM)] and supplemental fat (Ca salts of long-chain fatty acids at 0 or 2.2% of dietary DM) on the productive performance of lactating Holstein cows (n = 45) during the first 120 d postpartum. The main N sources were soybean meal and urea in the diets with high concentrations of degradable protein versus a combination of vegetable and animal by-product feedstuffs in the diets with less degradable protein. Cows fed the diets with excess degradable protein had slower rates of increase in DM intake (DMI) and milk production, had lower plasma insulin and greater plasma glucose and urea concentrations, and lost more than twice the body weight of cows fed the diets with less degradable protein. Supplemental fat in the highly degradable protein diet reduced the loss of body condition, stimulated DMI, and reduced concentrations of plasma nonesterified fatty acids early postpartum compared with the highly degradable protein diet without added fat. Without affecting DMI, supplemental fat stimulated milk production (2 kg/d) starting at 3 wk postpartum. During early lactation, DMI and milk production were sensitive to the degree of ruminal degradability of protein and energy supplementation in the form of fat.

Protein degradability and calcium salts of long-chain fatty acids in the diets of lactating dairy cows: reproductive responses.

Multiparous Holstein cows (n = 45) were assigned at calving to one of four diets arranged in a 2 x 2 factorial design. The two main factors were dietary concentration (dry matter basis) of 1) degradable intake protein (11.1 or 15.7%) and 2) supplemental fat (Ca salts of long-chain fatty acids; 0 or 2.2%). Soybean meal and urea were replaced with less degradable protein meals (corn gluten meal, meat and bone meal, fish meal, and blood meal). During the first 9 wk postpartum, cows fed diets containing the greater concentration of highly degradable protein demonstrated less follicular development on their ovaries, were delayed in their first luteal activity postpartum (25.2 vs. 38.6 d), accumulated less luteal tissue (< 15 vs. > 70 mm), and had lower plasma progesterone accumulated over time. The supplementation of Ca salts of long-chain fatty acids to the 15.7% degradable protein diet doubled the number of corpora lutea, reduced time to first rise in progesterone by 6 d, doubled the number of normal luteal phases, and restored the pattern of accumulated plasma progesterone concentrations to a pattern that was similar to that induced by other diets. Cows were synchronized to estrus and inseminated at approximately 65 d postpartum. Pregnancy rate was increased from 52.3 to 86.4% when fat was supplemented. Cows fed fat tended to have more corpora lutea and a larger corpus luteum and accumulated more plasma progesterone than did cows not fed fat. Diets containing excess degradable protein or Ca salts of long-chain fatty acids influenced ovarian structures and reproductive performance.

Assessment of the mammary system.

Assessing the health status of the mammary gland is a complex and often perplexing endeavor. One must use all of the faculties available to come up with an accurate diagnosis. A detailed history of the individual and the herd or flock plus a thorough physical examination that includes specific attention paid to the mammary gland are essential. One cannot overlook these basic tenets in favor of more sophisticated means of evaluation such as somatic cell counts and milk microbiology. A holistic approach to mastitis diagnosis, treatment, and, most importantly, control is necessary.