The world's population will reach 10.4 billion in 2067, with 81% residing in Africa or Asia. Arable land available for food production will decrease to 0.15 ha per person. Temperature will increase in tropical and temperate zones, especially in the Northern Hemisphere, and this will push growing seasons and dairy farming away from arid areas and into more northern latitudes. Dairy consumption will increase because it provides essential nutrients more efficiently than many other agricultural systems. Dairy farming will become modernized in developing countries and milk production per cow will increase, doubling in countries with advanced dairying systems. Profitability of dairy farms will be the key to their sustainability. Genetic improvements will include emphasis on the coding genome and associated noncoding epigenome of cattle, and on microbiomes of dairy cattle and farmsteads. Farm sizes will increase and there will be greater lateral integration of housing and management of dairy cattle of different ages and production stages. Integrated sensors, robotics, and automation will replace much of the manual labor on farms. Managing the epigenome and microbiome will become part of routine herd management. Innovations in dairy facilities will improve the health of cows and permit expression of natural behaviors. Herds will be viewed as superorganisms, and studies of herds as observational units will lead to improvements in productivity, health, and well-being of dairy cattle, and improve the agroecology and sustainability of dairy farms. Dairy farmers in 2067 will meet the world's needs for essential nutrients by adopting technologies and practices that provide improved cow health and longevity, profitable dairy farms, and sustainable agriculture.
Depletion of the ovarian reserve is associated with reproductive senescence in mammalian females, and there is a positive relationship between the size of the ovarian reserve and the number of antral follicles on the surface of the ovary. Therefore, we conducted a series of experiments to investigate the influence of stage of the estrous cycle, age, and birth weight on antral follicle counts (AFC) in beef cows and heifers. Pairs of ovaries were collected from crossbred beef cows at slaughter (n = 72) or at necropsy (n = 333; 0 to 11 yr of age); all visible antral follicles were counted, the ovaries were weighed, and stage of the estrous cycle was estimated based on ovarian morphology. There was no influence of estimated stage of the estrous cycle on AFC (P = 0.36). There was a small but positive effect of birth weight on AFC [AFC = -1.7 + 0.31(birth weight); P = 0.007, r(2) = 0.05]. When antral follicle counts were regressed on age, there was a quadratic effect of age such that AFC increased until 5 yr of age and decreased thereafter [AFC = 12.9 + 9.0(yr) - 0.86(yr(2)); P < 0.001, r(2) = 0.22]. In a third experiment, crossbred beef heifers (n = 406; 353 to 463 d of age) at 3 locations were subjected to ovarian ultrasonography on unknown day of the estrous cycle. Heifers were classified as low AFC (<15 follicle, n = 84) or high AFC (>24 follicles, n = 178). Whereas estimated stage of the estrous cycle did not influence AFC (P = 0.62), heifers classified as low AFC had smaller ovaries (P = 0.001), decreased birth weight (P = 0.003), and a decreased heifer pregnancy rate (P = 0.05) compared with heifers in the high AFC group. From these results, we conclude that AFC in beef cows and heifers is influenced by birth weight and age but not by stage of the estrous cycle. In beef cows, the number of antral follicles increases to 5 yr of age and then begins to decline. This may indicate that a decrease in fertility due to decline of the ovarian reserve may begin earlier than previously thought in beef cows.
Longevity and lifetime productivity are important factors influencing profitability for the cowcalf producer. Heifers that conceive earlier in the breeding season will calve earlier in the calving season and have a longer interval to rebreeding. Calves born earlier in the calving season will also be older and heavier at weaning. Longevity data were collected on 2,195 heifers from producers in South Dakota Integrated Resource Management groups. Longevity and weaning weight data were collected on 16,549 individual heifers at the U.S. Meat Animal Research Center (USMARC). Data were limited to heifers that conceived during their first breeding season. Heifers were grouped into 21-d calving periods. Heifers were determined to have left the herd when they were diagnosed not pregnant at the end of the breeding season. Heifers that left the herd for reasons other than reproductive failure were censored from the data. Heifers that calved with their first calf during the first 21-d period of the calving season had increased (P < 0.01) longevity compared with heifers that calved in the second 21-d period, or later. Average longevity for South Dakota heifers that calved in the first or later period was 5.1 ± 0.1 and 3.9 ± 0.1 yr, respectively. Average longevity for USMARC heifers that calved in the first, second, or third period was 8.2 ± 0.3, 7.6 ± 0.5, and 7.2 ± 0.1 yr, respectively. Calving period as a heifer influenced (P < 0.01) unadjusted weaning BW of the first 6 calves. Estimated postpartum interval to conception as a 2-yr-old cow was greater for females that calved in the first period as heifers but did not differ between heifer calving periods in subsequent calving seasons. In summary, heifers that calved early in the calving season with their first calf had increased longevity and kilograms weaned, compared with heifers that calved later in the calving season.
The first critical transition in follicular development, the activation of primordial follicles to leave the pool of resting follicles and begin growth, is poorly understood, but it appears that the balance between inhibitory and stimulatory factors is important in regulating the exodus of follicles from the resting pool. There is evidence that anti-Mullerian hormone (AMH; also known as MIS) inhibits follicle activation in mice, but whether it plays a similar role in non rodent species is not known. When pieces of bovine ovarian cortex, rich in primordial follicles, are cultured in serum-free medium, most follicles initiate growth, but when cortical pieces are grafted beneath the chorioallantoic membrane (CAM) of chick embryos, follicle activation does not occur. Since embryonic chick gonads of both sexes produce and secrete high levels of AMH, the hypothesis that the AMH in the chick circulation inhibits follicle activation was tested. In Experiment 1, whole newborn mouse ovaries were grafted beneath the CAM (placed "in ovo") or cultured in vitro for 8 days. In vitro (or after 8 days in vivo) follicles activated and proceeded to the primary or secondary stage, but activation was suppressed in ovo. This inhibition was reversed if ovaries were removed from beneath the CAM and cultured in vitro. In contrast, when ovaries from mice null mutant for the AMH type II receptor were CAM-grafted in Experiment 2, follicle activation occurred in a similar fashion to activation in vitro. This finding strongly implicates AMH as the inhibitor of follicle activation in ovo. Since chick embryonic gonads are the source of circulating AMH, chicks were gonadectomized in Experiment 3, prior to grafting of pieces of bovine ovarian cortex beneath their CAMs. Bovine primordial follicles activated in the gonadectomized chicks, similar to the results for mice lacking the AMH type II receptor. Taken together these experiments provide strong evidence that AMH is the inhibitor of mouse follicle activation present in the circulation of embryonic chicks and provide indirect, and hence more tentative, evidence for AMH as an inhibitor of bovine follicle activation.
The CAM graft will provide a useful model for studying the factors involved in activation of primordial follicles.
Children with normal-variant short stature can be classified into four subgroups by measuring their anabolic and growth reactions to a 10-day course of human growth hormone. In Subgroup 1 there is no anabolic or growth reaction; in Subgroup 2 there is a weak anabolic reaction but no growth; Subgroups 3 and 4 have both reactions but Subgroup 4 is more responsive than Subgroup 3. We monitored growth rate and plasma immunoreactive somatomedin C concentrations in four to six children from each subgroup (age range, eight to 11 years) before, during, and after six months of injections of growth hormone (0.08 unit per kilogram of body weight per day). In children in Subgroups 3 and 4, the average somatomedin C level, which was subnormal before treatment, was restored to normal. Simultaneously, the average growth rate accelerated fivefold. In children in Subgroups 1 and 2, whose average pretreatment somatomedin C was normal, growth hormone had little effect on somatomedin level of growth rate. The somatomedin response in Subgroups 3 and 4 was apparent by the 10th day of treatment. This response provides a rapid method for identifying affected children who will benefit from longterm administration of human growth hormone.
We hypothesized that the ovulatory response of one ovary to FSH would be related positively to the size of the primordial and growing pools of follicles in the other ovary. Nonlactating cows (n = 26) were unilaterally ovariectomized and 2 days later were superovulated. The superovulatory response was classified as Low (< 5 corpora lutea [CL]), Medium (5-14 CL), or High (> 14 CL). Surface follicles on the ovary removed before superovulation were classified as small (1-3 mm), medium (3-7 mm), or large ( > 7 mm), and the ovary was then fixed and serially sectioned. Follicles = 1 mm in diameter in 388 +/- 38 fields (2 x 2 mm) per cow were classified as primordial, primary, secondary, or tertiary. By classification, Suboptimal ovaries contained < 100 follicles = 1 mm and Optimal ovaries contained > 250 follicles = 1 mm. Number of CL was correlated positively with total number of primordial, tertiary, and medium surface follicles. Number of Empty fields (2 x 2-mm fields containing no follicles) was correlated negatively with superovulatory response and number of primordial follicles. Number of CL was related to number of tertiary follicles in a positive linear manner and the number of medium follicles in a positive quadratic manner (r 2 = 0.66). Numbers of primordial, tertiary, small surface follicles, medium surface follicles, and total surface follicles were lower (p = 0.06) in the Low superovulatory response group than in the Medium or High group. Suboptimal ovaries had fewer small surface follicles and fewer CL than Optimal ovaries (p < 0.05). We conclude that superovulatory response in cattle is related positively to the pools of primordial and growing follicles in the bovine ovary.
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