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The objective of the present experiment was to analyse the effect of body condition score (BCS) at calving, type of suckling restriction and flushing on metabolic and endocrine profiles, and productive and reproductive responses of primiparous beef cows grazing native grassland. Primiparous beef (n = 56) cows in anestrus classified by BCS at calving (low ≤3.5 and moderate ≥4; 1–8 visual scale) were assigned randomly to four treatments in a two by two factorial arrangement of type of suckling restriction and flushing. Type of suckling restriction started at 55 ± 10 days postpartum (DPP ± s.e.m.; Day 0 = initiation of the treatment) and consisted of applying nose plates to calves for 12 days (i.e. TS treatment) or 5 days of isolation of the cow–calf pair, followed by applying nose plates to calves for 7 days as calves were reunited with their mothers (i.e. IS treatment). Immediately after the suckling restriction treatments were finished, the breeding season started, and each cow received (flushing group) or not (control group) 2 kg/day (fresh basis) of whole-rice middling for 22 days. The BCS was superior in moderate-BCS cows through the experiment. The type of suckling restriction did not affect any plasma parameter, but insulin-like growth factor I (IGF-I) concentrations increased in all cows during suckling restriction. Cholesterol concentration was affected by flushing × day interaction (P < 0.05), while insulin and IGF-I concentrations were affected by the interaction among BCS at calving, flushing and days (P < 0.03). Flushing increased cholesterol concentration in both BCS groups at calving, while insulin and IGF-I concentrations increased during flushing only in moderate-BCS cows. Suckling restriction, flushing, and BCS at calving did not affect calf weight or milk production. Moderate BCS cows had a shorter postpartum anestrous interval (PPI) (98 vs 123 DPP; P < 0.01). Isolated type of suckling reduced postpartum anestrous interval when compared with TS treatment (97 vs 115 DPP, P < 0.05). Early pregnancy rate was greater in flushed than in control cows (0.8 vs 0.55, P < 0.01) and in moderate-BCS cows than in low-BCS cows (0.84 vs 0.46, P < 0.01). Total pregnancy rate was also greater in flushed and moderate cows and tended to be affected by the interaction between flushing and BCS at calving (P = 0.06; flushed cows: moderate = 1 vs low = 0.5, P < 0.08; and control cows: moderate = 0.8 vs low = 0.4, P < 0.09). These results confirmed the great value of suckling restriction and flushing during post-calving and relevance of BCS at calving as a link between energetic nutrition and metabolic and reproductive processes in primiparous beef cows grazing native grassland.

BackgroundThe present study hypothesized that GH-AluI and IGF-I-SnabI polymorphisms do change the metabolic/endocrine profiles in Holstein cows during the transition period, which in turn are associated with productive and reproductive parameters.MethodsHolstein cows (Farm 1, primiparous cows, n = 110, and Farm 2, multiparous cows, n = 76) under grazing conditions were selected and GH and IGF-I genotypes were determined. Blood samples for metabolic/endocrine determinations were taken during the transition period and early lactation in both farms. Data was analyzed by farm using a repeated measures analyses including GH and IGF-I genotypes, days and interactions as fixed effects, sire and cow as random effects and calving date as covariate.Results and DiscussionFrequencies of GH and IGF-I alleles were L:0.84, V:0.16 and A:0.60, B:0.40, respectively. The GH genotype was not associated with productive or reproductive variables, but interaction with days affected FCM yield in multiparous (farm 2) cows (LL yielded more than LV cows) in early lactation. The GH genotype affected NEFA and IGF-I concentrations in farm 1 (LV had higher NEFA and lower IGF-I than LL cows) suggesting a better energy status of LL cows.There was no effect of IGF-I genotype on productive variables, but a trend was found for FCM in farm 2 (AB cows yielded more than AA cows). IGF-I genotype affected calving first service interval in farm 1, and the interaction with days tended to affect FCM yield (AB cows had a shorter interval and yielded more FCM than BB cows). IGF-I genotype affected BHB, NEFA, and insulin concentrations in farm 1: primiparous BB cows had lower NEFA and BHB and higher insulin concentrations. In farm 2, there was no effect of IGF-I genotype, but there was an interaction with days on IGF-I concentration, suggesting a greater uncoupling somatropic axis in AB and BB than AA cows, being in accordance with greater FCM yield in AB cows.ConclusionThe GH and IGF-I genotypes had no substantial effect on productive parameters, although IGF-I genotype affected calving-first service interval in primiparous cows. Besides, these genotypes may modify the endocrine/metabolic profiles of the transition dairy cow under grazing conditions.

The effect of complexed trace minerals supplementation on productive, reproductive and metabolic variables during early postpartum of grazing primiparous dairy cows =) was investigated. Pasture-fed Holstein heifers were offered (supplemented group; SG, n = 60) or not (control group; CG, n = 60) a commercial trace mineral supplement during the first 90 days of lactation. Milk production and composition were determined monthly. Reproductive function was evaluated by calving-first service interval, number of services per conception, and pregnancy rates. Non-esterified fatty acids, β-hydroxybutyrate, insulin, and insulin-like growth factor-1 were determined on blood samples collected on days postpartum -7 ± 4, 30 and 60. Supplementation did not affect milk production or its composition, except for fat percentage that tended to be higher in SG than CG. Calving-first service and calving-conception intervals were shorter in SG than CG but number of services per conception and pregnancy rates did not differ between treatments. No lameness was observed during the period evaluated and although a beneficial effect of SG was found in locomotion score, it was not clinically relevant (scores 1-2). Metabolites and hormones concentrations did not differ between treatments. Organic trace mineral supplementation had a transient beneficial effect on milk composition on the intervals from calving to first service and from calving to conception, with no changes in metabolic and endocrine profiles during the transition period primiparous dairy cows on grazing conditions. Additional key words: dairy cows; Holstein heifers; metabolic-endocrine profile microminerals; transition. ResumenEfecto de la suplementación con minerales orgánicos traza durante el postparto temprano sobre la composición de la leche y los perfiles metabólicos y hormonales en novillas de leche Se investigó el efecto de la suplementación con complejos de minerales traza sobre variables productivas, reproductivas y metabólicas durante el postparto temprano en vacas lecheras primíparas en pastoreo. Novillas Holstein (n = 120) fueron suplementadas (SG) o no (grupo control; CG) con un preparado comercial de minerales traza durante los primeros 90 días de lactación. La producción de leche y su composición se determinaron mensualmente. La actividad reproductiva fue evaluada por el intervalo parto-primera inseminación artificial (IA), el número de servicios por concepción y la tasa de gestación. Se determinaron los ácidos grasos no esterificados, el β-hidroxibutirato, la insulina y el factor de crecimiento similar a la insulina-1 en muestras de sangre tomadas los días postparto -7 ± 4, 30 y 60. La suplementación no afectó la producción de leche ni su composición, excepto por una tendencia del porcentaje de grasa a ser mayor en el SG que en el CG. Los intervalos parto-primera IA y parto-concepción fueron menor en SG que en CG, pero el número de IA por concepción y las tasas de gestación no fueron diferentes entre los dos grupos. No

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