Nine commercial dairy herds, each with low herd milk somatic cell counts, were monitored for 1 yr to determine prevalence of intramammary infections and rates of clinical mastitis. Staphylococcus species was the bacterial group most frequently isolated from quarters at calving and at drying off. Environmental streptococci and coliform intramammary infections totaled less than 6% of quarters at both calving and at drying off. Staphylococcus aureus were isolated from less than 1% of quarters and Streptococcus agalactiae from 0% of quarters at both calving and drying off. A total of 646 clinical cases of mastitis were diagnosed in 548 quarters of 406 cows. Mean rate of clinical mastitis among herds was .457 clinical cases/305 cow-days. Rates of clinical mastitis ranged among herds from .273 to .748 clinical cases/305 cow-days. Coliforms and bacteriologically negative and environmental streptococci accounted for 82.3% of clinical cases. Rates of clinical mastitis and severity of clinical signs differed among herds, seasons of the year, parity groups, and stages of lactation. Rates of clinical mastitis were highest during summer, in first lactation cows, and during the first 7 d of lactation.

Factors associated with bulk tank milk bacterial and somatic cell counts were investigated for one year on nine well managed dairies. Geometric mean total bacterial count among dairies was 4.4 × 10 colony cfu/ml. Geometric mean bulk tank milk somatic cell counts among herds was 265 × 10ml. Bacterial counts in bulk tank milk were correlated with rates of coliform and environmental streptococcal clinical mastitis cases. Rates of total clinical cases were also correlated with bulk tank milk somatic cell counts. Correlations were measured among bulk tank milk bacterial counts and gram-negative bacterial, coliform, Klebsiella species, and streptococcal counts in materials used to bed lactating cows. Total bacterial and staphylococcal bulk tank milk counts increased when synthetic rubber liners were used greater than 800 quarter milkings. Correlations measured indicated that monitoring bulk tank milk may be an effective means of detecting management changes in herds with low bacterial and milk somatic cell counts.

An electronic spreadsheet program using a budgeting procedure was used to compare the effect of protein pricing differentials and cheese yield pricing systems on income over feed and variable costs of the six major dairy breeds. Increasing the protein differentials from $ .03 to .22/45.4kg milk per .1 unit increase in protein percent above 3.2% decreased the difference in income over feed and variable costs between non-Holstein and Holstein breeds. With the prices and assumptions used, the income over feed and variable costs of non-Holstein breeds never equaled or surpassed that of Holsteins. With current milk, feed, and cheese prices, using a cheese pricing system caused a substantial decrease in income over feed costs for Holsteins and decreased the differences between Holsteins and non-Holsteins. Increased cheese prices, increased feed prices, and lowered milk prices also narrowed the differences in income over feed and variable costs between Holstein and non-Holstein breeds. Although changes in the milk pricing system make the non-Holstein breeds more competitive with Holsteins, non-Holstein breeds must produce between 224 and 1539kg more milk with the various milk and feed price scenarios used for the income over feed and variable costs to equal that of Holsteins.

Rate of growth was studied in 140 Holstein heifers fed standard amounts (.9 kg/day, control) or extra amounts (4.5 kg/day) of grain with or without .45mg melengestrol acetate (MGA) from 2.5 months of age to initial breeding size (120cm withers height). Heifers fed extra grain exhibited first estrus at an earlier age (P<.01) than the controls (7.5±.1 versus 8.7±.2 months), but body weight and withers height at first estrus were unaffected by amount of grain or MGA. Heifers fed extra grain attained 120cm withers height at 11.4 months of age, whereas controls required 12.5 months (P<.01). Melengestrol acetate did not affect ages when the heifers attained 120cm withers height. The interval from first estrus to 120cm withers height (about 3.5 months) was not affected by nutrition or MGA. Although MGA did not affect skeletal growth, it increased body weight about 10% at 120cm withers height, but only with extra grain (P<.01) and only after about 5.5 months of age. Neither amount of grain nor MGA affected weights of the mammary glands either at first estrus or at 120cm withers height. At 120cm withers height, mammary deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) were elevated over 60% (P<.01) by MGA especially in heifers fed extra grain. Pituitary prolactin was unaffected, but MGA depressed prolactin in blood plasma, especially in heifers fed standard grain. Melengestrol acetate fed before pregnancy did not affect subsequent milk production. Melengestrol acetate increased the number of large ovarian follicles, reduced uterine DNA, increased uterine RNA, and increased endometrial cell height. Neither pituitary luteinizing hormone nor folliclestimulating hormone was influenced by MGA or quantity of grain fed. On the average, all heifers calved by 2 years of age, and age at conception, services per conception, weight at calving, withers height at calving, and weight of calf were uninfluenced by MGA or amount of grain. In terms of age at first calving, neither extra grain nor MGA offers appreciable gain relative to standard grain alone.

Body composition, tenderness, growth hormone levels, thyroid activity and adrenal cortical activity were measured after feeding melengestrol acetate (MGA) to Holstein heifers. MGA was administered at 0.45 mg per animal per day either from 2.5 months of age or from first estrus. The heifers were fed corn silage and hay ad libitum in addition to either 0.9 or 4.5 kg grain per head daily and killed at first estrus or at breeding size. MGA feeding increased growth rates by 9.95% (P<.05) in one analysis. Mean jugular growth hormone level was significantly lower in MGA treated animals, and was significantly and negatively related to growth rate. The results suggested that MGA may preferentially stimulate the growth of lean tissue. Adrenal weights were significantly reduced in animals receiving MGA in one analysis. Plasma cortisol, adrenal cortisol and adrenal corticosterone concentrations, and adrenal fasiculata layer widths were significant (P<.05) less in animals fed MGA than in comparable animals without MGA.

The influence of melengestrol acetate (MGA) on sperm and egg transportation superovulation and fertility was studied in 77 rabbits. 2 experiments were conducted. In the first experiment no fertilized ova were found in rabbits inseminated into the vagina or lower uterine horns on either Day 1 or Day 3 after a 12-day period of MGA injections. However fertility after upper uterine insemination was 79%. The results of the first experiment suggested inhibition of sperm transportation through the cervix and lower uterus or failure of normal sperm survival in the female after MGA but little or no effect of MGA on capacitation of sperm. The second experiment was designed to compare fertility of inseminations into the vagina the lower uterine horns or the upper horns. The fertility data from this experiment concurred with the results of the first experiment. MGA also reduced efficiency of ova recovery from the oviducts at about 24 hours after ovulation but did not reduce the number of ova ovulated.