The relationship between milk urea concentration and the fertility of dairy cows was examined in two studies. The first examined the relationship between bulk milk urea concentration and overall herd fertility, using data collected from 250 herds in the UK. There was no relationship either between bulk milk urea concentration and fertility, or between changes in bulk milk urea concentration and fertility. The second study compared the relationship between the milk urea concentration five days after service, and the fertility of individual cows on 11 UK dairy farms. There was no significant difference between the milk urea concentration of the cows that became pregnant and those that did not.
The Committee on Medical Aspects of Food Policy report Nutritional Aspects of Cardiovascular Disease recommended increased dietary intakes of the long chain polyunsaturated fatty acids eicosapentaenoic acid and docosahexaenoic acid to help protect against cardiovascular disease. There is some evidence that a-linolenic acid can be elongated and desaturated by mammalian enzyme systems to produce small amounts of eicosapentaenoic and docosahexaenoic acids. Whole linseeds are rich in a–linolenic acid, and it has been suggested that feeding this oilseed to dairy cows may result in higher levels of the long chain polyunsaturated fatty acids in bovine milk. To examine this hypothesis, the effect of feeding whole ground linseed and xylose treated whole ground linseed on the performance and milk composition of dairy cows was investigated.Either form of whole linseed reduced dry matter intakes and milk protein concentration. The xylose treated whole linseed increased milk yield, but neither linseed source changed milk fat concentration. Levels of milk a-linolenic acid increased to 1.2 g/100 g fatty acid when whole ground linseed was fed, and to 1.5 g/100 g fatty acid with the xylose treated linseed compared with 0.7 g/100 g fatty acid for cows fed the control diet. The efficiency of incorporation of additional dietary a-linolenic acid into milk fat was estimated to be 1.6 and 3.4% for the whole ground and xylose treated whole ground linseed respectively. Feeding whole ground linseed increased the proportion of a-linolenic acid in milk fat, but there was no evidence of eicosapentaenoic and docosahexaenoic acids in milk fat, suggesting that if any elongation and desaturation of a-linolenic acid occurs in dairy cows, none is transferred to milk.
The objective of this study, which formed part of a larger project, was to investigate the effect of feeding high levels of urea on the reproductive function of the lactating dairy cow. Increasing dietary protein intake can increase milk production, but may reduce reproductive performance (Laven and Drew 1999). McEvoy et al (1997), based on work which fed urea to sheep, suggested that this effect on fertility may be caused by ammonia. However, there is little information on the effect of feeding quickly degradable nitrogen (QDN) on the concentration of plasma ammonia in the dairy cow and the accurate measurement of plasma ammonia is difficult. The measurement of a more stable metabolite, such as urea, may be more useful, if it can be shown to be correlated with plasma ammonia.
A considerable number of calves is born prematurely. Morbidity and mortality of preterm calves are higher than of calves born at normal term. Besides insufficient functioning of the lungs, immaturities of the gastrointestinal tract (GIT) and of endocrine control of metabolism are thought to contribute to health problems. Because corresponding studies are lacking in preterm calves, we have tested the hypothesis that there are differences in maturation at birth and in response to feeding for 8 d of the GIT and of metabolic and endocrine traits between term and preterm calves. Fourteen calves were born on d 275 of gestation, i.e. 42 ± 3 h after dams were injected 0.5 mg prostaglandin F 2α and 5 mg Flumethason, and were slaughtered either on d 1 (GrPS, n=7) or on d 8 (GrPF, n=7) of life. Another 14 calves, serving as control, were spontanously born after normal lengths of pregnancy (290 ± 2 d) and were slaughtered either on d 1 (GrNS, n=7) before first feeding or on d 8 (GrNF, n=7) of life. The 8 d old preterm and term calves were fed colostrum and then mature milk. Blood samples were taken from jugular veins to measure blood gases, hematologic, metabolic and endocrine traits. Histomorphometrical analyses of duodenum, jejunum, ileum and colon were performed on slides stained with hematoxilin and eosin. Cell proliferation was based on counting crypt cells which (following injection of 500 µg 5-bromo-2`-deoxyuridine 1 h before slaughter) had incorporated this substance into DNA and relative to unlabeled epithelial cells and as relative to the length of the mucosal epithelial layer. Apoptotic cells were visualized based on terminal transferase 3' end labelling by fluorescence microscopy. Results: The pH was lower (P<0.05) in GrPS than in GrPF. Mean pCO 2 tended to be higher (P<0.05) in GrPS versus GrNS, and tended to be higher (P<0.1) in GrPS than in GrPF. There were no group differences in pO 2 , base excess, HCO 3 , TCO 2 , and sO 2 . Haematological traits were always in physiological range and barely differed between term and preterm calves. Blood plasma concentrations of metabolites (protein, immunoglobulin G, albumin, urea, creatinine, nonesterified fatty acids, triglycerides, cholesterol, glucose, lactate) and hormones (growth hormone, insulin-like growth factor-1, 3.5.3'-triiodothyronine and thyroxine, cortisol, insulin, glucagon) and patterns of postnatal changes in preterm calves were in the same range as in calves born at normal term. In jejunum villus circumferences, areas and heights were greater (P<0.001) in GrNS than in GrNF and GrPS. Villus circumferences and villus heights in ileum were greater (P<0.05) in GrNS than in GrNF. Crypt depths in duodenum, jejunum, ileum and colon were greater (P<0.001) in GrNF than in GrNS and GrPF. Villus circumferences, areas and heights were greatest in jejunum, whereas colon had the greatest crypt depths. Number of BrdU-labeled cells in duodenum and jejunum were higher (P<0.05) in GrNF than in GrNS. Number of BrdU-labeled cells in duodenum and number of BrdUlabeled cells...
Human nutritionists have identified that dietary myristic and palmitic fatty acids are major risk factors in cardiovascular disease. Bovine milk fat is particularly rich in these fatty acids as they can be produced de novo in the mammary gland from by-products of fibre fermentation in the rumen. However, increased dietary levels of C18 fatty acids has been shown to reduce the concentration of myristic and palmitic acids in milk fat. Supplying dietary oil from whole oilseeds treated with xylose, may reduce rumen biohydrogenation of polyunsaturated fatty acids and further decrease the saturated fatty acid content of milk. In this study, the effect of feeding whole ground soya beans, whole ground soya beans treated with xylose and whole ground rape seed on dairy cow performance and milk composition was investigated. All three oilseeds reduced dry matter intakes and milk protein concentration. Both the xylose treated whole ground soya beans and the whole ground rape seed increased milk yield, but the whole rape reduced milk fat content. Levels of linoleic acid in milk fat increased when whole soya was fed, whereas oleic acid concentration was highest when whole rape was included in the diet. Concentrations of myristic and palmitic acids in milk fat were lower when any whole ground oilseed was fed, but the reduction was greatest with whole ground rape which reduced the myristic plus palmitic acid content of milk fat to 25 g/100 g fatty acid, compared with 47 g/100 g milk fatty acid in the milk from cows fed a standard low oil diet. These results suggest that feeding specific sources of dietary oil can dramatically reduce levels of myristic and palmitic acids in milk fat, and that different oilseeds have different effects on milk fat concentration.
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