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Two assumptions commonly applied in convection schemes—the diagnostic and quasi‐equilibrium assumptions—imply that convective activity (e.g., convective precipitation) is controlled only by the large‐scale (macrostate) environment at the time. In contrast, numerical experiments indicate a "memory" or dependence of convection also on its own previous activity whereby subgrid‐scale (microstate) structures boost but are also boosted by convection. In this study we investigated this memory by comparing single‐column model behavior in two idealized tests previously executed by a cloud‐resolving model (CRM). Conventional convection schemes that employ the diagnostic assumption fail to reproduce the CRM behavior. The memory‐capable org and Laboratoire de Météorologie Dynamique Zoom cold pool schemes partially capture the behavior, but fail to fully exhibit the strong reinforcing feedbacks implied by the CRM. Analysis of this failure suggests that it is because the CRM supports a linear (or superlinear) dependence of the subgrid structure growth rate on the precipitation rate, while the org scheme assumes a sublinear dependence. Among varying versions of the org scheme, the growth rate of the org variable representing subgrid structure is strongly associated with memory strength. These results demonstrate the importance of parameterizing convective memory, and the ability of idealized tests to reveal shortcomings of convection schemes and constrain model structural assumptions. Plain Language Summary: Convection (clouds) has memory, can remember its own history, and is affected by it when evolving to the next step. However, this memory effect is often neglected in convection schemes, which are approximate sub‐models used to represent (parameterize) convective processes in climate models whose resolutions are too low to properly resolve convection. In this study we apply two simple tests to probe the memory behavior of various convection schemes. We found that most conventional schemes fail to mimic the memory response of a cloud‐resolving model (CRM) where convection is properly represented. In two schemes where memory is parameterized, their responses are more similar but still bear significant differences to the CRM. We show that this discrepancy can be explained by the equations used in these schemes. For one of the schemes, we also found that the strength of memory is related to the growth rate of the memory variable, rather than its absolute value. Overall, our results demonstrate the importance of taking memory into account in convection schemes, and show that the two tests implemented here are simple but useful in shining light on potential shortcomings of convection schemes and hence also ways to improve them. Key Points: Several convection schemes were tested via two recently proposed, idealized experiments designed to isolate memory‐like behaviorAll schemes either fail to show any such behavior, or show weaker memory than an explicit cloud‐resolving modelBy fitting simple equation sets to the results, structural assumptions and parameters related to subgrid memory processes can be constrained [ABSTRACT FROM AUTHOR]

The objective of this study was to estimate breeding values (EBV) and genetic and phenotypic trends for female fertility traits derived from artificial insemination (AI) records. Data were collected from automated milk recording systems: 64464 records from 18 South African (SA) Holstein herds. Breeding values were estimated for heifer traits, i.e., age at first service (AFS), age at first calving (AFC), number of services per conception (SPCh); and for cow traits, i.e., calving to first service (CFS), number of days open (DO), number of services per conception (SPC), first service within 80 days post-partum (FS80d), and whether cows were confirmed pregnant within 100 days post-partum (PD100d) or within 200 days post-partum (PD200d) using THRGIBBSF90. Trends were estimated for the period 1984 to 2011. There was no clear trend on average breeding values for heifer traits. However, phenotypic trends for heifer traits showed a desirable downward trend, with a decrease of 0.14 and 0.13 months/year for AFS and AFC, respectively. Phenotypic trends for cow fertility traits appeared to increase at the rate 0.16 and 0.83 days/year for CFS and DO, respectively, with animals requiring 0.02 more services per year for SPC. The average EBV for binary traits FS80d, PD100d, and PD200d, showed no distinct trend. In general, there was no clear genetic and phenotypic trend for all traits defined. The trends that appeared to follow trait improvement could have been coincidental. Thus, efforts have to be made towards the improvement of heifer and cow fertility traits explored in this study. [ABSTRACT FROM AUTHOR]

The efficiency of feed use for milk production is critical for sustainable and profitable pasture-based dairy systems. The aim of this study was to estimate milk production and energy-use efficiencies of pasture-grazed Holstein and Jersey cows. Lactation records of 122 Holstein and 99 Jersey cows varying from parities 1 to 6 that were managed under similar feeding and environmental conditions were collected from 2005 to 2014. Feed intake and nutrient requirements of the cows were calculated using the National Research Council and the Cornell Net Carbohydrate and Protein System equations. Holsteins had a higher milk yield/kg dry matter intake (1.36±0.01 vs. 1.27±0.01 kg), whereas Jerseys had higher efficiencies in milk fat (52.4±0.3 vs. 58.4±0.4 g), milk protein (42.7±0.3 vs. 45.1±0.3 g), and energy-corrected milk (1.30±0.01 vs. 1.36±0.01 kg) per kg dry matter intake. Jersey cows also had a higher dry matter intake/kg body weight (3.13±0.02 vs. 3.51±0.02%). During transition and early lactation stages, Holstein and Jersey cows were in negative energy balance for 102.4±2.3 vs. 74.2±2.3 days, with the lowest energy reserves (-53.9 MJ vs. -39.7 MJ) reached at 22.3±0.9 vs. 24.6±0.9 days post-calving, respectively. Compared to Holsteins, Jersey cows used proportionally less net energy intake to produce 100 g milk fat (13.7±0.10 vs. 12.5±0.10), 100 g milk protein (16.7±0.14 vs.16.2±0.15) and a 1-kg energy-corrected milk (5.52±0.04 vs. 5.35±0.04), making them a better breed for pasture-based dairy systems as they possess more production and feed-use efficiency traits, which are desirable in pasture-based production systems. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the milk production of Holstein and Jersey cows on pasture as affected by parity, lactation stage, calving season, age at first calving, and calving interval. Test-day lactation records of 122 Holstein and 99 Jersey cows, varying from parities 1 to 6, were collected using standard milk recording procedures. Cows were managed and kept as one herd on kikuyu over-sown with ryegrass pasture and received 7 kg of concentrate (as fed) containing 170 g/kg crude protein per day. Across parities, the means for milk yield, milk fat, milk protein, dry matter intake, and body weight were 23.8 ± 6.2 and 17.9 ± 4.4 kg/day; 3.89 ± 0.03 and 4.66 ± 0.03%; 3.17 ± 0.02 and 3.59 ± 0.02%; 17.8 ± 2.6 and 14.4 ± 2.1 kg/day; and 567 ± 3.49 and 411 ± 3.84 kg for Holstein and Jersey cows, respectively. Milk yield increased by 26.5% in Holsteins and 23.7% in Jerseys from first to fourth lactation. Mean lactation number was 2.5 ± 0.15 and 3.0 ± 0.17; test-day milk yield for summer was 21.2 ± 0.28 and 16.5 ± 0.31 kg/day; and winter was 21.3 ± 0.28 and 16.4 ± 0.32 kg/day; age at first calving was 26.4 ± 0.3 and 26.2 ± 0.3; and inter-calving period was 13.9 ± 0.18 and 13.2 ± 0.17 months, for Holstein and Jersey cows, respectively. With inter-calving periods of 13 months, 13.1 to 15.0 and above 15 months, the 305-day Holstein cow milk yield was 7324 ± 181, 7768 ± 193, and 7927 ± 211 kg, whereas that of Jerseys was 5400 ± 135, 5621 ± 244, and 5724 ± 234 kg, respectively. In this study, Jerseys performed better than Holsteins in lactation number and calving interval. Holsteins, however, had a higher increase in milk yield from first to fourth lactation, whereas age at first calving did not differ. [ABSTRACT FROM AUTHOR]

Beef production is a natural possibility in dairy herds through culled cows and rearing bull calves for veal or beef production. This potential is not always exploited fully, probably because of its relatively small contribution to overall farm income. Studies were conducted comparing different breeds in crossbreeding programs towards improving milk output, fertility and beef production potential through rearing of dairy and crossbred bull calves as veal or beef. Initially, Jersey cows in a pasture-based system were serviced by Belgian-Blue and Limousin sires. Crossbred bull and heifer calves were reared on pasture to 24 months of age and growth rate parameters compared to Jersey steers. At marketing, the live weight of crossbreds was heavier than Jersey steers, although lower than expected because of poor pasture quality and utilization. Further crossbreeding studies included Holstein and Jersey cows serviced by either purebred sires or Fleckvieh sires, a Simmentaler-derived breed from Germany. Pure- and crossbred bull calves were reared intensively as veal to live weights of approximately 200 kg to ensure a carcass weight not exceeding 100 kg. Another group of bull calves were reared as beef to 21 months of age on rain-fed pasture. As expected, the daily live weight gain was higher in crossbred bull calves and steers compared to Jersey calves and steers, while not differing between Fleckvieh x Holstein and Holstein bull calves and steers. A preliminary study also indicates that the pure Holstein bull calves may perform well in the feedlot. Results indicate a potentially higher beef income for crossbred veal calves and steers. Further studies are required to determine an optimal feeding program and marketing age as well as its effect on beef quality characteristics. [ABSTRACT FROM AUTHOR]

The aim of this article was to review the state of fertility of female dairy cattle in South Africa and to compare it with international efforts at improving fertility. Fertility in dairy cows is defined as the ability to conceive from first insemination soon after calving and to carry the calf full term to calving. It is one of the main profit drivers in the dairy industry and is a complex trait that is influenced by the environment, genetics, and their interaction. Generally, there has been a decline in dairy cow fertility across breeds worldwide because of intense selection for milk yield, milk components, and body conformation traits. In addition, most fertility traits are negatively correlated to milk production traits. Milk production has been the focal point of selection programmes as it is linked directly to the profitability of the dairy enterprise. The low heritability of fertility traits is one of the factors that discouraged efforts to include fertility in genetic evaluations. However, owing to its economic importance, female fertility was later included in the breeding objectives for dairy cattle in several countries. Although most fertility traits are heritable to a low degree, some additive genetic variability can be exploited. [ABSTRACT FROM AUTHOR]

Certain fatty acids (FAs), such as omega-3 and conjugated linoleic acid (CLA) are considered essential FAs with beneficial health effects for humans. Milk is considered a relatively inexpensive and readily available source of these FAs and is part of a recommended healthy daily diet. The aim of the study was to determine the effect of diet changes on the FA composition of Jersey (J) and Fleckvieh x Jersey (FxJ) milk. Cows were alternately put on kikuyu-ryegrass pasture, followed by a feedlot system, then returned to kikuyu-ryegrass pasture for four weeks each. The same concentrate mixture was fed to cows regardless of feeding system. The feedlot system consisted of a partial total mixed ration (pTMR). Milk samples were collected two and four weeks after diet changes and stored at -20 °C until laboratory analysis by gas chromatography. The FA concentration of milk was not affected by breed, although it was affected significantly by diet changes. Most notably, the total omega-3 and -6 FAs decreased when cows were fed pTMR while increasing when the diet was changed back to pasture feeding. The CLA content of milk was similarly affected. That is, concentrations decreased significantly when the cows were on the pTMR diet and increased when cows were put back on the pasture-based diet. The results suggested that the health benefits of milk fat are affected negatively when cows are fed pTMR compared with being fed in a pasturebased system. The health benefits of milk are reduced owing to decreased levels of the CLA content of milk fat. Therefore, feeding additional hay in a pasture-based production system should be reconsidered when aiming to produce milk that provides health beneficial qualities. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate two late prepartum fibre-based diets that differed in nonstructural carbohydrate (NFC) and protein levels on live weight (LW) changes and fertility traits of Holstein cows until 120 days postpartum. At 30 days before calving, 120 pregnant Holsteins (heifers, n = 54 and dry cows, n = 66) from the Elsenburg herd were assigned to two nutritional treatments according to parity, expected calving date, LW, and milk production during the previous lactation. Prepartum heifers and cows were fed independently a similar type and level of a prepartum concentrate, associated with an ad libitum intake of either unchopped oat hay for the control group or a partial total mixed ration (pTMR: oat hay (48%), lucerne hay (43%) and soybean oil cake meal (9%)) for the treatment group. After parturition, cows in both the control and treatment groups were maintained on ad libitum cultivated irrigated kikuyu-ryegrass pastures, supplemented each with a post-partum concentrate of 7 kg/day from calving until 120 days in milk (DIM). As expected, young and still growing primiparous cows were significantly lighter in pre- and post-partum LW traits compared with mature multiparous cows (parity > 3). Prepartum LW of cows was similar between the control and the treatment in both parity groups. Post-partum LW of the primiparous cows differed significantly between the control and the treatment, which were 488 ± 9 and 507 ± 13 kg, respectively. However, no difference was observed in terms of post-partum LW of multiparous cows of the control and the treatment groups, which were 579 ± 10 and 579 ± 8 kg, respectively. Primiparous cows that received the prepartum oat hay-based diet showed significant decrease in post-partum LW loss changes, LWnadir, LW loss at nadir and rate of LW loss from calving to LWnadir in comparison with their counterparts on the prepartum pTMR-based diet, but these LW traits were similar in multiparous cows. Prepartum diets did not have an effect on post-partum fertility parameters of the multiparous cows, whereas primiparous cows that received the control diet recorded a significantly longer interval from calving to first service (CFS) in the subsequent lactation in comparison with their counterparts fed the treatment diet i.e. 117 ± 9 and 86 ± 8 days, respectively. Proportions of cows that were pregnant at 120 DIM were similar in the subsequent lactation between groups that received the prepartum oat hay- and pTMR-based diets in both parity groups. Further research is required to investigate different prepartum feeding periods and nutritional approaches involving various levels and sources of energy and protein nutrients to encourage post-partum metabolic and hormonal responses that benefit the fertility of dairy cows in the subsequent lactation. [ABSTRACT FROM AUTHOR]

Presents a technique which allows the dimension of a point contact to shrink down to a single atom. Description of the device used in the experiment; Details on the experiment; Information on the sample fabrication.

This review discusses the effects of starch and fat before and after calving on metabolism, energy balance (EB), milk production, and reproduction in dairy cows. The shift in dairy cows from a pregnant nonlactating state to a non-pregnant lactating state induces physiological changes, which affect the metabolic and endocrinal axes to redirect body energy stores towards the mammary gland for milk production. Overfeeding high starch and fat levels during the dry period after calving may result in cows failing to adapt to the negative energy balance (NEB) because of major liver and rumen dysfunction. Alternatively, keeping dry cows on high-forage/low-energy diets adjusts dry matter intake (DMI) to optimize the rumen function and decrease the severity of the NEB during transition. These periparturient biological improvements in dairy cows showed real benefits such as fewer postpartum health complications (e.g. milk fever, ketosis, mastitis, metritis), decreased body condition loss and improved reproductive axis in the subsequent lactation. Adding dietary starch and/or fat to diets of dairy cows following parturition increased milk yield. In addition, milk protein of dairy cows increased with glucogenic diets, but decreased with lipogenic diets. Inversely, milk fat usually increases after feeding lipogenic diets, but it decreases when feeding glucogenic diets to dairy cows. Glucogenic and lipogenic nutrients can affect the cow's metabolism and its EB status positively, as is evidenced by plasma non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), glucose, amino acids, insulin, insulin-like growth factor-I (IGF-I), growth hormone (GH), gonadotropin hormones, and progesterone (P4) levels. These metabolites (NEFA, BHB, glucose, amino acids) and hormones (insulin, IGF-I, GH, P4) have been shown to affect folliculogenesis, ovulation, conception, and pregnancy success. Feeding a starchbased diet to dairy cows can lead to acidosis and increase glucose and insulin levels, while decreasing NEFA and BHB levels. Furthermore, an insulinogenic diet favours an early resumption of ovarian activity, but has adverse effects on the quality of oocytes. In contrast, keeping dairy cows on a fat-based diet elevates NEFA and BHB levels and decreases glucose and insulin levels. Additionally, a lipogenic diet increases the plasma P4 levels and improves the quality of oocytes. These evidences suggest that reproductive performances in dairy cows can be enhanced by feeding an insulinogenic diet until the resumption of the ovarian cycle then switching to a lipogenic diet from mating period onwards. Since long-term field studies on fertility are limited and the reproduction process in dairy cows is multi-factorial, further research is needed on the pre- and postpartum effects of starch and/or fat as well as their combinations on reproduction axis and thus to draw conclusions on reproductive performances. [ABSTRACT FROM AUTHOR]

Heat stress in dairy cows is an increasing problem because of climate change. Even though South Africa has a warm to hot climate, little research on this topic has been done locally. Currently, while intensive housing is increasing being used in large dairy production systems, a shade structure provides the first step to protect cows against heat stress improving production performance and welfare. This paper provides results on the production performance, physiological parameters and behaviour of Holstein-Friesian cows with and without access to a shade structure during summer. The effects of heat stress on primiparous Holstein-Friesian and Jerseys cows in a breed comparison study are also shown. The milk yield of Holstein-Friesian cows with access to shade was significantly higher than that of cows without shade. Although the difference in milk yield was small (5.5%), the difference between the accumulative milk yield between shade and no shade cows increased over time for each of the three summer seasons, indicating a decreasing ability of cows without shade to withstand heat stress conditions. The internal rate of return on the capital outlay for the construction of a shade structure showed a positive return on investment within three summer seasons. Jersey cows displayed a higher tolerance to heat stress than Holstein-Friesian cows suggesting that they would be more suitable for a hot environment. However, the large difference (ca 30%) in production performance should be taken in account when considering a change in breed. Ways to alleviate the effect of heat stress on dairy cows are suggested. [ABSTRACT FROM AUTHOR]