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Season of birth is associated with first-lactation milk yield in Holstein Friesian cattle
- M. Van Eetvelde, M. M. Kamal, L. Vandaele, G. Opsomer
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The aim of the present research was to assess factors associated with first-lactation milk yield in dairy heifers, including maternal and environmental factors, factors related to the development of the heifer and factors related to its offspring such as gender of the calf. In addition, the potential underlying mechanism, in particular metabolic adaptations, was further explored. Data on body growth, reproduction and milk yield of 74 Holstein Friesian heifers on three herds in Flanders (Belgium) were collected. At birth, body measurements of the heifers were recorded and blood samples were taken (in order) to determine basal glucose and insulin concentrations. Body measurements were assessed every 3 months until first calving, and gender and weight of their first calf were recorded. Information on fertility and milk yield of the heifer and its dam were collected from the herd databases. Daily temperature and photoperiod were recorded from the database of the Belgian Royal Meteorological Institute. Linear mixed models were run with herd as a random factor, to account for differences in herd management. Heifers grew 867±80.7 g/day during their first year of life and were inseminated at 14.8±1.34 months. First calving took place at 24.5±1.93 months, at a weight of 642±61.5 kg and heifers produced 8506±1064 kg energy corrected milk during their first 305-day lactation. Regression models revealed that none of the maternal factors such as milk yield and parity, nor the growth of the heifer during the 1st year of life were associated with milk yield during first lactation. Age, and to a lesser extent BW at first parturition were positively associated with first-lactation milk yield. In addition, the season of birth, but not calving, had a significant influence on milk yield, with winter-born heifers producing less than heifers born in any other season. The lower yielding winter-born heifers had higher insulin concentrations at birth, whereas glucose concentrations were similar, the latter being suggestive for lower insulin sensitivity of the peripheral tissues. Furthermore, environmental temperature at the end of gestation was negatively correlated with neonatal insulin concentrations. In conclusion, results of the present study suggest heifers born during the hotter months are born with a higher peripheral insulin sensitivity, finally leading to a higher first-lactation milk yield.
Evidence for placental compensation in cattle
- M. Van Eetvelde, M. M. Kamal, M. Hostens, L. Vandaele, L. O. Fiems, G. Opsomer
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Prenatal development is known to be extremely sensitive to maternal and environmental challenges. In this study, we hypothesize that body growth and lactation during gestation in cattle reduce nutrient availability for the pregnant uterus, with consequences for placental development. Fetal membranes of 16 growing heifers and 27 fully grown cows of the Belgian Blue (BB) breed were compared to determine the effect of body growth on placental development. Furthermore, the fetal membranes of 49 lactating Holstein Friesian (HF) cows and 27 HF heifers were compared to study the impact of dam lactation compared to dam body growth. After parturition, calf birth weight and body measurements of dam and calf were recorded, as well as weight of total fetal membranes, cotyledons and intercotyledonary membranes. All cotyledons were individually measured to calculate both the surface of each individual cotyledon and the total cotyledonary surface per placenta. Total cotyledonary surface was unaffected by breed or the breed×parity interaction. Besides a 0.3 kg lower cotyledonary weight (P=0.007), heifer placentas had a smaller total cotyledonary surface compared with placentas of cows (0.48±0.017 v. 0.54±0.014 m2, respectively, P<0.001). Within the BB breed, fetal membranes of heifers had a 1.5 kg lower total weight and 1.0 kg lower intercotyledonary membrane weight (P<0.005) compared with cows. A cotyledon number of only 91±5.4 was found in multiparous BB dams, while growing BB heifers had a higher cotyledon number (126±6.7, P<0.001), but a greater proportion of smaller cotyledons (<40 cm2). Within the HF breed, no parity effect on intercotyledonary membrane weight, cotyledon number and individual cotyledonary surface was found. Placental efficiency (calf weight/total cotyledonary surface) was similar in HF and BB heifers but significantly higher in multiparous BB compared with multiparous HF dams (106.0±20.45 v. 74.3±12.27 kg/m2, respectively, P<0.001). Furthermore, a seasonal effect on placental development was found, with winter and spring placentas having smaller cotyledons than summer and fall placentas (P<0.001). Main findings of the present study are that lactation and maternal growth during gestation entail a comparable nutrient diverting constraint, which might alter placental development. However, results suggest that the placenta is able to manage this situation through two potential compensation mechanisms. In early pregnancy the placenta might cope by establishing a higher number of cotyledons, while in late gestation a compensatory expansion of the cotyledonary surface is suggested to meet the nutrient demand of the fetus.
Environmental factors and dam characteristics associated with insulin sensitivity and insulin secretion in newborn Holstein calves
- M. M. Kamal, M. Van Eetvelde, H. Bogaert, M. Hostens, L. Vandaele, M. Shamsuddin, G. Opsomer
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The objective of the present retrospective cohort study was to evaluate potential associations between environmental factors and dam characteristics, including level of milk production during gestation, and insulin traits in newborn Holstein calves. Birth weight and gestational age of the calves at delivery were determined. On the next day, heart girth, wither height and diagonal length of both the calves and their dams were measured. Parity, body condition score and age at calving were recorded for all dams. For the cows, days open before last gestation, lactation length (LL), length of dry period (DP) and calving interval were also calculated. The magnitude and shape of the lactation curve both quantified using the MilkBot model based on monthly milk weights, were used to calculate the amount of milk produced during gestation. Using the same procedure, cumulative milk production from conception to drying off (MGEST) was calculated. A blood sample was collected from all calves (n=481; 169 born to heifers and 312 born to cows) at least 5 h after a milk meal on day 3 of life to measure basal glucose and insulin levels. In addition, an intravenous glucose-stimulated insulin secretion test was performed in a subset of the calves (n=316). After descriptive analysis, generalized linear mixed models were used to identify factors that were significantly associated with the major insulin traits (Insb, basal insulin level; QUICKI, quantitative insulin sensitivity check index; AIR, acute insulin response; DI, disposition index) of the newborn calves. The overall average birth weight of the calves was 42.7±5.92 kg. The insulin traits were significantly associated with gender and season of birth when data of all calves were analyzed. In addition, the insulin traits in calves born to cows were significantly associated with MGEST, DP and LL. The Insb was estimated to be higher in calves born to the cows having passed a higher MGEST (P=0.076) and longer DP (P=0.034). The QUICKI was estimated to be lower in calves born to the cows having passed a higher MGEST (P=0.030) and longer DP (P=0.058). Moreover, the AIR (P=0.009) and DI (P=0.049) were estimated to be lower in male compared with female calves. Furthermore, the AIR (P=0.036) and DI (P=0.039) were estimated to be lower in calves born to cows having passed a longer LL. The decisive effects of MGEST, DP and LL in cows on the insulin traits of their calves may provide a basis for developing managerial interventions to improve metabolic health of the offspring.