Feeding frequency has diet-dependent effects on plasma hormone concentrations but does not affect oocyte quality in dairy heifers fed fibre- or starch-based diets

Abstract

The post-fertilisation developmental capacity of bovine oocytes recovered by ultrasound guided transvaginal follicular aspiration (ovum pick-up, OPU) is influenced by diet-induced changes in hormone and metabolite concentrations. The objectives of this experiment were first to determine whether post-prandial changes in hormone concentrations, induced by changing the frequency of feeding, influenced oocyte quality and second whether changes in plasma glucagon concentration were associated with oocyte quality. Using a 2 3 2 factorial design, Holstein heifers (six per treatment) were fed either fibre-or starch-based diets containing either 189 or 478 g starch/kg dry matter. The diets were offered in either two or four equal meals per day and supplied twice the maintenance energy requirement. Blood samples were obtained both at weekly intervals (three samples per heifer, collected before feeding) during the experiment and throughout an entire 24-h period (15 or 17 samples per heifer for twice or four times daily-fed heifers, respectively). Each heifer underwent six sessions of OPU (twice weekly) beginning 25 days after introduction of the diets. Oocyte quality was assessed by development to the blastocyst stage in synthetic oviductal fluid following in vitro fertilisation. Mean weekly plasma insulin concentrations did not differ between diets, but plasma glucagon concentrations were greatest when heifers were fed the starch-based diet twice daily compared with the other diets. When heifers were offered four meals per day, there were no meal-related changes in hormone concentrations. However, when heifers were offered two meals per day, plasma insulin concentration increased after feeding the starch-based, but not the fibre-based diet. Plasma glucagon concentration increased after meals when heifers were fed twice daily and the increase was substantially greater when the starch-based diet was fed. Treatments did not influence (overall mean with mean 6 s.e.) ovarian follicle size distribution or oocyte recovery by OPU (6.2 6 0.4 per heifer), the proportion of oocytes that cleaved following insemination (0.57 6 0.030) or blastocyst yield (0.27 6 0.027 of oocytes cleaved). In conclusion, by feeding diets differing in carbohydrate source at different frequencies of feeding, meal-related changes in plasma hormone profiles were altered significantly, but oocyte quality was not affected. Therefore effects of diet on oocyte quality appear not to be mediated by meal-related fluctuations in hormone concentrations.

Increased feeding frequency increased milk fat yield and may reduce the severity of subacute ruminal acidosis in higher-risk cows

“…Increasing feeding frequency did not affect the concentrations of glucose, insulin, or fatty acids in the plasma of dairy cows. Previous studies Rooke et al, 2008) have also reported that the average daily concentrations of these metabolites were not affected by feeding frequency. A couple of studies did report a tendency for increased feeding frequency to lower peak and average insulin concentrations (Sutton et al, 1988;, but these studies fed cows 8 or 12 times a day, and that may have contributed to the discrepancies with the current study.…”

Nutritional Strategies to Promote Bovine Oocyte Quality for In Vitro Embryo Production: Do They Really Work?

“…Weekly blood concentrations of insulin and BCS were not altered by diet, but IGF-1 and leptin were increased when starch diets were provided four times a day [81]. In addition, post-prandial increases in insulin and glucagon associated with starch consumption were observed, suggesting that the metabolic alterations associated with meal frequency do not seem to impact oocyte developmental competence [81]. The same animal model was used to test the effects of different levels of starch and leucine, showing that a high intake of starch can impair in vitro blastocyst production associated with high insulin concentrations in blood.…”

“…Similarly, IVEP was unaltered in Holstein heifers with a BCS of 2 who were fed with either a 2 M fibre-or starch-based diet supplied twice or four times a day for around 45 days. Weekly blood concentrations of insulin and BCS were not altered by diet, but IGF-1 and leptin were increased when starch diets were provided four times a day [81]. In addition, post-prandial increases in insulin and glucagon associated with starch consumption were observed, suggesting that the metabolic alterations associated with meal frequency do not seem to impact oocyte developmental competence [81].…”

“…Consideration of the initial BCS of cows and heifers and its monitoring during experimental trials has shown to be a simple but effective way to determine the overall metabolic effect of experimental feeding regimes. Indeed, the absence of significant changes in the BCS of oocyte donors sometimes seems to be a better determinant of the lack of impact of nutritional treatments on IVEP rather than blood concentration changes in metabolic hormones and metabolites [63,81]. However, BCS is a subjective assessment of body fat deposition, and it is influenced by the experience level of the evaluator [142].…”