The effects of two levels of herbage allowance (HA, kg DM/kg liveweight (LW)) on forage mass and chemical composition, cow body condition score, cow LW, stocking rate, productive and reproductive responses were evaluated during two consecutive years. Eighty primiparous spring-calving beef cows were allocated to a completely randomised block design of two HA that had an annual average of 2.5 (low) and 4.0 kg DM/kg LW (high) from –150 to 195 days postpartum. The grazing system was continuous, and the put-and-take method was employed to adjust HA. At 86 ± 12 days postpartum, all cows were submitted to calf suckling restrictions with nose plates (12 days) and dietary flushing (2 kg/cow.day of whole-rice bran for 22 days), 6 days before bull introduction. Forage mass was affected by HA (P = 0.004) and year (P = 0.014); the high HA had a greater forage mass than the low HA (1474 vs 1212 ± 86 kg DM/ha; P < 0.05), and Year 2 had a greater forage mass than Year 1 (1545 vs 1134 ± 78 kg DM/ha; P < 0.05). Stocking rate was affected by HA and season (P = 0.0004) interaction. The stocking rate during autumn and spring was greater in low than high HA, and no differences were identified in winter and summer. The body condition score was improved in high HA during autumn and resulted in a greater winter (mid-gestation) body condition score than the low HA without differences during spring-summer (postpartum). Cow LW was lower during autumn, winter and early postpartum (16 days postpartum) in low HA in Year 1 than high HA of Year 1 and high and low HA cows in Year 2. Furthermore, the probability of total pregnancies (0.88 vs 0.59 ± 0.07; P = 0.01) and the calf weight adjusted to 205 days (194 vs 175 ± 16 kg; P < 0.05) were greater in high HA. Calf weight adjusted to 205 days (Year 1: 192 vs Year 2: 177 ± 16 kg; P < 0.05) and survival curves of postpartum anoestrus (P = 0.01) were affected by year but did not affect the probability of conception, early or total pregnancies. In conclusion, the reproductive and productive responses of primiparous beef cows grazing Campos grasslands were improved in high HA and could contribute to alleviating adverse climatic conditions effects.

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The objectives of the present experiment were to analyse the reproductive and productive responses to suckling-restriction treatments and flushing in primiparous grazing beef cows. During 3 years, 153 primiparous anoestrus cows were assigned randomly to one of four treatments in a 2 by 2 factorial arrangement of suckling-management treatments and flushing. Suckling-restriction treatments started at 61 ± 10 days postpartum and consisted of applying nose plates to calves for 12 days (i.e. TS treatment) or 5 days of isolation of the calf from the cow followed by applying nose plates to calves for 7 days as calves were reunited with their mothers (i.e. IS treatment). Nutritional treatments (flushing v. control) started at the beginning of the breeding season, immediately after the suckling-restriction treatments were finished (73 ± 10 days postpartum), with cows receiving or not receiving 2 kg/day of whole-rice middling for 22 days. Cow body condition score (BCS) was recorded every 20 days from calving until 120 days postpartum. Duration of postpartum anoestrus (PPA) and probability of cyclicity were estimated by plasma progesterone concentrations analysed in weekly samples. Pregnant cows were determined by ultrasound 42 days after bull introduction (early pregnancy; EP) and 30 days after the end of the breeding season (total pregnancy; TP). BCS at calving and changes in BCS from calving to the day of BCS nadir (ΔBCS) varied among years depending on forage availability and weather conditions. Increased cow BCS at calving decreased PPA (b = –41 days, P < 0.0001) and, in interaction with ΔBCS, increased EP (P < 0.008) and TP (P < 0.003). Calf weights at weaning and average daily gain were not affected by suckling-restriction or flushing treatments. Isolated temporary suckling control reduced PPA by 11 days when compared with temporary suckling control (P < 0.004). Flushing increased EP by 40%, which was also affected by BCS at calving and was greater in cows that gained, than in those that maintained or lost BCS. We conclude that flushing was useful in improving early pregnancy rates of primiparous beef cows with ‘suboptimal’ body condition (lower than 4.5) at calving and grazing native pasture.

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.

The body condition score (BCS) at calving has been postulated as the main factor in the interaction of nutrition and reproduction in beef-cow ecosystems. The objective of the present study was to analyse the effect of BCS at calving on endocrine and metabolic profiles during the transition period in primiparous Hereford cows (n = 56) grazing native grassland. Cow BCS was registered and plasma insulin, insulin-like growth factor-I (IGF-I) and metabolites (concentrations of urea, albumin, cholesterol, total protein, non-esterified fatty acids (NEFA)) were determined in plasma from –30 to +45 days postpartum (DPP). The effect of BCS at calving (low ≤3.5 and moderate ≥4; 1–8 visual scale) on BCS evolution and hormone and metabolite concentrations were analysed using a time repeated-measures analysis. Cow BCS, NEFA, urea and IGF-I profiles were affected (P < 0.05) by the BCS at calving and DPP interaction, while insulin tended (P = 0.06) to be affected only by BCS at calving. The low-BCS cows presented a smaller loss of BCS during the prepartum than did moderate-BCS cows, and a delayed BCS recovery during the postpartum. The increase in plasma NEFA was greater (P < 0.05) and started earlier during the prepartum period in the low-BCS cows. Protein concentrations increased during prepartum to +30 DPP, while albumin and urea concentrations were maintained until calving and decreased during the postpartum. Urea concentrations were greater (P < 0.05) during prepartum in low-BCS cows. Concentrations of IGF-I and insulin were greater (P < 0.05) in moderate- than low-BCS cows during prepartum, but did not differ between the groups after calving. No effects were observed in calf weight or milk production at +45 DPP. The association between BCS during prepartum and at calving with the endocrine and metabolic profiles (positive: insulin, IGF-I; negative: NEFA and urea) reflected a better nutritional status and plasticity to negative energy balance on moderate cows. This different endocrine milieu did not affect calf weight and/or milk production. In conclusion, the BCS at calving affected the metabolic and endocrine profile during the transition period of primiparous beef cows grazing native grassland.