Conservation priorities for the different lines of Dutch Red and White Friesian cattle change when relationships with other breeds are taken into account.

From a genetic point of view, the selection of breeds and animals within breeds for conservation in a national gene pool can be based on a maximum diversity strategy. This implies that priority is given to conservation of breeds and animals that diverge most and overlap of conserved diversity is minimized. This study investigated the genetic diversity in the Dutch Red and White Friesian (DFR) cattle breed and its contribution to the total genetic diversity in the pool of the Dutch dairy breeds. All Dutch cattle breeds are clearly distinct, except for Dutch Friesian breed (DF) and DFR and have their own specific genetic identity. DFR has a small but unique contribution to the total genetic diversity of Dutch cattle breeds and is closely related to the Dutch Friesian breed. Seven different lines are distinguished within the DFR breed and all contribute to the diversity of the DFR breed. Two lines show the largest contributions to the genetic diversity in DFR. One of these lines comprises unique diversity both within the breed and across all cattle breeds. The other line comprises unique diversity for the DFR but overlaps with the Holstein Friesian breed. There seems to be no necessity to conserve the other five lines separately, because their level of differentiation is very low. This study illustrates that, when taking conservation decisions for a breed, it is worthwhile to take into account the population structure of the breed itself and the relationships with other breeds.

Differences in mastitis susceptibility between Holstein Friesian, Dutch Friesian and Dutch Red and White cows.

Summary On an experimental farm 3 dairy breeds were compared with regard to mastitis by various parameters. Higher cell counts and more udder infections were present in the Dutch Red and White (DRW) in comparison with the Holstein Friesian (HF) and the Dutch Friesian (DF). Within the HF breed a negative correlation between cell count and production was established and also in this breed, a negative correlation between maximum rate of milk flow and cell count. There is no evidence that higher procuction and easier milking are connected with more mastitis. On the contrary, within the breeds an opposite trend appeared. Selection against mastitis does not conflict with selection for production and ease of milking. An addition trial revealed that sampling after too quick preparation of the cows before milking resulted in much higher cell counts in quarter samples. Cows which were selected for drying off with antibiotics recovered from their infection but these more susceptible animals maintained a higher cell count to a certain extent.

[Direct selection for fertility and health in cattle]. / Directe selectie op vruchtbaarheid en gezondheid bij rundvee.

Financial losses in dairy cattle due to breeding inefficiency and health impairment are so high that they should be taken into account in cattle breeding. These disturbances tend to increase as productivity increases. Although these disturbances are quantitative characteristics, they can only be recorded qualitatively. Therefore the heritabilities of breeding inefficiency and health impairment are low. Several of these disturbances (mastitis, metabolic disorders) show a much higher incidence in cows than they do in heifers. Selection for production-traits is mainly based on heifer groups of bulls. Artificial selection designed to prevent disturbances will fail to produce positive results as the heritabilities are low for heifers and the current groups of heifers are too small to obtain a reliable estimate of the breeding value of a bull for disturbances of fertility or health. Natural selection against these disturbances should not be ruled out, and therefore it is advisable to record certain disturbances and to use this recording in the selection of bull dams.

[Breed variations in feed intake and energy utilization in dairy cows]. / Rasverschillen in voeropname en energiebenutting bij melkkoeien.

In four experimental studies on feed intake, two completely mixed rations containing 0 and 50 per cent of concentrates respectively were fed ad lib. to dairy cattle of four different breeds: the Jersey, the Holstein-Friesian (HF), the Dutch Black-and-White (FH) and the Dutch Red-and-White (Meuse-Rhine-Yssel). There are considerable differences in feed intake between the breeds, particularly between the Jerseys and the heavier breeds (HF + MRY + FH). The experimental studies in the Jerseys showed that there was an interaction between breed and the composition of the feed, which is due to differences in nutrient requirements between breeds. These variations are attributable to differences in composition of the milk. The dairy breeds, Jersey and HF, use a large part of the energy taken up for milk production and a smaller part for maintenance than do the double-purpose breeds: FH and MRY.

[A comparison between large breeds of cattle and their cross-breeds with Jerseys]. / Een vergelijking tussen grote runderrassen en hun kruisingen met Jerseys.

Friesians (ZB) and MRY cows were inseminated with semen from Jersey or Holstein Friesian (ZB) and Jersey or MRY bulls respectively. The Jersey x Friesian (J x ZB) and the Jersey x MRY (J x MRY) crossbreds were compared with their contemporary Friesian and MRY herdmates, respectively. Crossbreds were born without any calving problems. The feet and legs were better, the mature weight, the feed costs and the average carcass values were lower compared to the purebreds. The conclusions are, that in market situations, where milk production or milk fat production is not limited, the crossbreds yield a much higher return per hectare than the purebreds. The present measures to limit milk fat production do not make crossbreds clearly profitable over Friesians and MRY's in the Netherlands. Also the relative increase for milk protein in relation of milk fat has contributed to that.

[Effect of BST administration on milk production and metabolism of dairy cows in 3 consecutive years of IVO trials(Institute for Animal Husbandry Research)]. / Het effect van BST-toediening op de melkproduktie en de stofwisseling van melkkoeien gedurende drie achtereenvolgende jaren in IVO-proeven.

The effect of subcutaneous administration of recombinantly derived bovine somatotropin (somidobove) in a sustained delivery vehicle was studied in three successive lactations. After a preliminary period of three months, cows of different breeds and parities were treated during six periods of treatment of 28 days. The efficacy of BST application was equal in Jerseys (n = 35), Red and Whites (n = 54) and Friesians (n = 149); was slightly higher in cows (n = 211) than in heifers (n = 32); was higher on concentrates- (n = 105) than on roughage (n = 138) based diets and was slightly lower in a third successive lactation. After the start of treatment body tissues were mobilised for the increased milk production, however after some weeks of treatment, energy intake increased and compensated for the higher food requirements. Somatic cell counts in milk were higher in treated than they were in control cows. Calves of treated cows (n = 80) showed a five per cent lower birth weight than those of control cows (n = 80). No differences were found between treated and control cows in disease frequency and in reasons for culling. Administration of BST improved efficiency of milk production in three lactations, without adverse effects on health or culling rates of cows and without negative effects on the quality of the milk.

[Effects of long-term BST application in dairy cows]. / De effecten van langdurige BST-toediening bij melkkoeien.

The effects of administration of BST on milk production of dairy cows are summarised on the basis of a number of review papers. Then the results of a trial with forty control cows and thirty-seven cows, in which six doses of 640 mg of BST were subcutaneously injected at twenty-eight day intervals from the fourth month after calving in a third of fourth lactation are discussed. The response to administration of BST was a 3.2 kg of milk yield, 165 g for milk fat, 105 g of milk protein and 155 g lactose. Efficiency of milk production during the period of treatment was seven per cent higher in the treated cows. During the successive lactations, the response to BST in milk fat slightly declined, but similar responses were recorded for milk protein and lactose. Plasma levels of 3-hydroxybutyrate and NEFA were higher after treatment with BST. Fertility and health were not affected by this treatment. Calves from treated cows showed five per cent lower birth weight, which had no effects on viability and postnatal weight gain. Treatment with BST did not have any effect on the concentrations of calcium, magnesium, phosphorus and NEFA in milk. In the successive lactations, the somatic cell count in the milk of treated cows increased slightly more than that in controls. During the third and fourth lactation, in the period of treatment, the number and percentage of polymorphonuclear neutrophils and number of macrophages were higher in milk showing higher cell counts. More quarters of the udders of treated cows were bacteriologically infected compared to the controls before and after treatment. Small injection sites were detected on 50-60 per cent of the treated cows, which disappeared rapidly. In the third and fourth lactation, no marked differences between controls and treated cows were recorded in frequencies of diseases and culling.

Differences in mastitis susceptibility between Holstein Friesian, Dutch Friesian and Dutch Red and White cows. Correlation between parameters for mastitis and for production.

On an experimental farm 3 dairy breeds were compared with regard to mastitis by various parameters. Higher cell counts and more udder infections were present in the Dutch Red and White (DRW) in comparison with the Holstein Friesian (HF) and the Dutch Friesian (DF). Within the HF breed a negative correlation between cell count and production was established and also in this breed, a negative correlation between maximum rate of milk flow and cell count. There is no evidence that higher production and easier milking are connected with more mastitis. On the contrary, within the breeds an opposite trend appeared. Selection against mastitis does not conflict with selection for production and ease of milking. An addition trial revealed that sampling after too quick preparation of the cows before milking resulted in much higher cell counts in quarter samples. Cows which were selected for drying off with antibiotics recovered from their infection but these more susceptible animals maintained a higher cell count to a certain extent.

Fertility control in cattle by use of the "milk progesterone test".

The development and validation of a radioimmunoassay for progesterone in cow's milk is described. Control of the temperature during storage of the milk and also during the sample incubation procedure appeared to be a critical requirement with respect to reduction of nonspecific binding of tritiated progesterone. Ranges of milk progesterone levels were established during pregnancy as well as during the luteal and the follicular phase of the oestrus and of pregnancy in three trials on two experimental farms. The mean accuracy with respect to the diagnosis "pregnant", "non-pregnant" or "not in oestrus" were 84.0, 97.6, and 100%, respectively. By leaving out of account all animals with high progesterone values (greater than 10 ng. ml(-1)) on day 1 (= day of insemination) the accuracy of the diagnosis "pregnant" was improved to 87.1%.

Effects of treatment of dairy cows with recombinant bovine somatotropin over three or four lactations.

Jersey, Dutch Red and White, and Friesian cows were subcutaneously injected with 640 mg of recombinant bST at 28-d intervals from 87 to 115 d after calving through four successive lactations. A TMR (6.72 MJ of NEL) and 168 g of CP/kg of DM) was fed for ad libitum consumption. The bST effects per day were 3.3 kg for milk yield, 189 g for fat yield, 109 g for protein yield, 157 g for lactose yield, 4 MJ of NEL for feed intake, and -4 kg for body weight. Responses in blood parameters measured 7 d after injection were -.007 mmol/L for glucose, -1.3 mg of N/100 ml for urea, 221 mumol/L for 3-hydroxybutyrate, 59 mumol/L for NEFA, 65 ng/L for insulin, 2.8 micrograms/L for thyroxine, and 26.7 micrograms/L for somatotropin. Somatic cell count in milk was 75,000 cells/ml higher in treated cows. Concentrations of NEFA, Ca, Mg, and phosphorus were unaffected. Repeatability of the maximum response in milk yield after bST treatment was low: .2 within and .5 between lactations. Cows treated in the previous lactation had slightly more retained placentas, and birth weight of their calves was 2 kg less. No differences were observed between treated and control cows in disease incidence. Six treated cows were culled in third and fourth lactations. No indications for tissue damage, inflammation, or stress after bST injections were detected.

Effect of monensin on milk production by Holstein and Jersey cows.

Effects of the administration of monensin via concentrates to dairy cows were studied in two trials. In one trial, 64 Holstein cows were assigned to four groups that received 0, 150, 300, or 450 mg/d of monensin from 5 to 24 wk postpartum. Milk production tended to increase (4.0, 3.3, and 5.4%, respectively) for the three groups of treated cows. Fat content was decreased by 0.09, 1.89, and 4.09 g/kg, respectively, for these same three groups. The effect on protein content was small and nonsignificant. Feed intake was reduced in treated cows, although not significantly, and feed efficiency was improved by monensin. In a confirmatory trial, 58 Holstein and 22 Jersey cows were allocated either to a control group or to a treatment group that received 300 mg/d of monensin from 5 to 36 wk postpartum during the first lactation and from 2 wk before calving to 36 wk postpartum during a subsequent lactation. During the first lactation, cows in the treatment group showed a 7% increase in milk production, a relative decrease (1.4 g/kg) in milk fat content, and equal protein content compared with cows in the control group. Body weight gain and body condition scores near the end of the treatment period were higher for cows in the treatment group. A decrease in blood ketone concentrations was found between 7 and 56 d of lactation. Treatment effects on milk production differed between breeds and within genetic lines. Jersey cows were less responsive than were Holstein cows, and Holstein cows with a high ratio of breeding values for protein and fat showed larger milk production responses. Results from the second lactation showed similar differences between the two groups as did those from the first lactation.

Genetic correlation between days until start of luteal activity and milk yield, energy balance, and live weights.

The objective of this study was to estimate genetic correlations among fertility and measures of energy balance, dry matter intake, and live weight (change). Data from 622 first lactation cows (fed ad libitum a complete ration) included milk, fat, and protein yields; energy balance; and live weights for the first 15 wk of lactation. For a subset of the heifers (n = 329) and 91 contemporaries, progesterone values were measured in the milk twice a week and were used to determine the interval between calving and first luteal activity (CLA). To obtain correlations, a series of bivariate animal model analyses was performed. The heritabilities for CLA and energy balance were 0.16 and 0.33, respectively. Heritability for live weights were 0.48 to 0.61 and for live weight changes were 0.17 and 0.24. Genetic correlations of CLA with milk, fat, and protein yields were high and unfavorable (0.51, 0.65, and 0.48, respectively), whereas energy balance, live weight during lactation, and weight gain all had a favorable genetic correlation with CLA (range -0.40 to -0.80). When genetic variation in CLA was adjusted genetically for milk, fat, and protein yields, the correlation with feed intake became -0.49 and explained approximately half of the genetic variance in CLA. This supports that increasing genetic merit for feed intake, at a common genetic merit for yield, improved CLA. Furthermore, selection on an index including protein yield and energy balance or live weight (change) allowed 0.71 to 0.80 of the maximum response in protein yield without a negative selection effect on CLA.

Autologous and homologous transplantation of bovine spermatogonial stem cells.

The aim of this study was to develop a method for spermatogonial stem cell transplantation into the bovine testis. Five-month-old Holstein-Friesian calves were used and half of the calves were hemicastrated to allow autologous transplantation and the other half were used for homologous transplantation. Approximately 20 g of each testis was used for cell isolation. On average 106 cells per gram of testis containing about 70% type A spermatogonia were isolated. The cells were frozen in liquid nitrogen until transplantation. Testes were irradiated locally with 10-14 Gy of X-rays to deplete endogenous spermatogenesis. At 2 months after irradiation, cells (approximately 10 x 10(6) were injected into the rete testis through a long injection needle (18 gauge), using ultrasonography and an ultrasound contrast solution. At 2.5 months after transplantation, calves were castrated and samples of testes were taken for histological examination. After 2.5 months in the irradiated non-transplanted control testes, only 45% of the tubules contained type A spermatogonia. However, after autologous spermatogonial transplantation, >80% of the tubule cross-sections contained type A spermatogonia. In addition, only 20% of the tubules of the control testes contained spermatocytes and, except for a few tubules (5%) with round spermatids, no more advanced germ cells were found. After autologous spermatogonial transplantation, about 60% of the tubules contained spermatocytes; 30% contained spermatids and in about 15% of tubules spermatozoa were found. No improvement in spermatogonial repopulation was found after homologous transplantation. The results of this study demonstrate, for the first time, successful autologous transplantation of bovine spermatogonial stem cells resulting in a complete regeneration of spermatogenesis.