Resposta produtiva de vacas leiteiras submetidas a ofertas de forragem em pastos consorciados no Uruguai

• Ano de defesa: 2014
• Autor(a) principal: Rebuffo, Gianni Paolo Motta
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Mato Grosso; Brasil; Faculdade de Agronomia, Medicina Veterinária e Zootecnia (FAMEVZ); UFMT CUC - Cuiabá; Programa de Pós-Graduação em Ciência Animal
• Palavras-chave em Português: Comportamento animal; Intensidade de desfolhação; Oferta de forragem; Produção de leite; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA; Animal behavior; Forage offer; Grazing intensity; Milk production
• Link de acesso: http://ri.ufmt.br/handle/1/438

The present research was developed based on two short term experiments carried out in autumn spring of 2010 and one in the hole productive year of 2010, whit the objective of study the effects of grazing intensity in animal performance and their effects on animal grazing behavior. The experiments were carried out in the Experimental Station of de Agronomy Faculty of Uruguay. The first experiment was carried out with the objective of evaluate animal behavior, forage selection, and animal performance in Holstein dairy cows by changing forage mass offerduring early lactation on early autumn. The animals were blocked by calving date (27/3 10), live weight (527± 67 Kg), body condition score (2,790,31) and randomly distributed in three treatments: Hi (OA: 38.4 kg DM/cow.day-1), Medium (OM: 30.3 kg DM/cow.day-1) and Low (OB: 26.8 kg DM/cow.day-1) forage mass offer for a 56 days period. The animals grazed during the morning from 7:30 to 14:30 hours between the morning and evening milk in individual paddocks for each treatment in a second year perennial pasture whit a botanical composition of 58% of Festuca arundinacea, 20% od Trifolium repens, 12% of death forage and 10% of weeds. After the evening milk the animals were individually supplemented whit 5.5 Kg of DM per cow of a total mixed ration with a concentrate : voluptuous relation of 65:35 in dry matter bases (CP=17,1±1,0%, NDF=40,0%). Diary milk production was measured in each milk, individual samples of all animals were taken weakly, for milk fat and protein determination. Animal grazing behavior was measures whit Grazing Recorders® during the last 3 days in each paddock in three animals per treatment. During these days it was determined pasture selection by Hand clipping techniques. The experimental design was completely random blocks, all the results were submitted to a variance analysis applying the Tukey Krammer test whit a 5% of probability of error. During the experimental period the OA and OM treatments had a superior milk production (P<0.05) that the OB treatment whit no statistic differences between them (26,0±0,4 vs. 23,8±0,4 L/cow/day). No statistic differences were obtained in Milk fat percentage (mean: 3,71±0,09%), milk protein percentage (mean: 3,16±0,05%) nor total fat production (mean: 934±46 g/cow/day). Significant differences between treatments were observed for total protein production (820±30, 846±29, and 718±33 g/cow/day) for OA, OM and OB respectively. There were no significant differences for CP values for the forage selected between treatments (mean:17,90,71%), but there were observed significant differences for NDF percentages (44,8±0,79, 47,0±0,82 and 49,4±0,80 (P<0.05) for AO OM and OB treatments respectively. There were observed significant differences (P<0.05) between treatments on grazing time (369,1±7,1; 317,0±7,0; 335,1±7,2 minutes/day) for OA OM and OB, such as on the bite rate (64 ± 2,0; 51 ± 2,0; 60 ± 1,9 bites/minute) or OA OM and OB. During the experimental period the OB treatment had a lower milk production, that could be explained by a inferior quality of the diet selected expressed by a higher NDF value and a diminish of grazing time in comparison with the OA treatment. Under grazing conditions during the autumn forage mass offer under 26,8 KgDM/cow/day, animal performance is negatively affected. The second experiment was carried out during the spring with the same objectives as the experiment one. There were used 36 Holstein dairy cows whit spring calving and 1611 days in lactation. The animals were blocked by calving date, live weight, body condition score and randomly distributed in three treatments: Hi(OA: 49.8 kg DM/cow.day-1), Medium (OM: 33.7 kg DM/cow.day-1) and Low (OB: 27,6 kg DM/cow.day-1) forage mass offer for a 56 days period. The animals grazed during the morning from 7:30 to 14:30 hours between the morning and evening milk and from 17:00 untill 4:30 hours in individual paddocks for each treatment in a second year perennial pasture whit a botanical composition of 56% of Festuca arundinacea, 37% of Trifolium repens, 5% of death forage. Animals were supplemented whit 2 KgDM/cow of a concentrate supplement during each milk (CP:18,11 %; NDF:19,11,0 %). Diary milk production was measured on each milk, individual milk samples were taken weakly, for milk fat and protein determination. Animal grazing behavior was measures whit Grazing Recorders®. During this days it was was determined forage selection by Hand clipping techniques. The experimental design was completely random blocks, all the results were submitted to a variance analysis applying the Tukey Krammer test whit a 5% of probability of error. There were no significative differences on the selected forage by the treatments (CP: 24,8±1,17; NDF:37,9±1,44 and ADF:22,4±1 %. There were observed significant differences (P<0.05) between treatments on grazing behavior, which conducted in forage dry matter intake differences between treatment. During the experiment the Medium forage offer treatment presented the highest milk production (P<0.05) (30,56±0,29), followed by the low forage offer treatment (29,42±0,28) and the hi forage offer treatment (27,14±0,32). Statistical differences were bserved in milk solid values (P<0.05). The animal performance differences between treatments were caused by the different forage selection strategies used by the animals during grazing, trying to maximize intake rate under different grazing environments created by the treatments. The third experiment was conducted an experiment whit the objective of evaluate three forage mass offer treatments by changing grazing intensity whit Holstein dairy cows in a second year perennial pasture of Festuca arundinacea, and Trifolium repens, for a one year period. The experiment was carried out in the Experimental Station of de Agronomy Faculty of Uruguay in 2010. Once a week forage growth rate, a total biomass production was measured. The botanical composition was measured once a month in each treatment. Total milk production per hectare was determined by individual milk of all animals during the stoking period. Stocking rate was calculated using the number of animals in the total area and the time spent grazing. The experimental design was completely random blocks, all the results were submitted to a variance analysis applying the Tukey test whit a 5% of probability of error. There were no statistical differences (P>0.05) in the annual forage growth rate (40,034,41; 45,394,4; 42,164,41 KgDM/ha/day), for hi, medium and low forage mass offer. There were no statistical differences (P>0.05) in the total annual biomass production (14620571; 16576571; 15373571 KgDM/ha/year), for hi, medium and low forage mass offer. There were no statistical differences (P>0.05) in the annual stocking rate (1,710,08; 1,870,08; 1,730,08 animals/hectare), for hi, medium and low forage mass offer. No statistical differences (P>0.05) were observes in the botanical composition between treatments. Seasonal variation in forage growth rate, forage biomass accumulation and stocking rate, affected the total milk production per hectare per year (P<0.05), where the medium forage mass offer treatment presented the highest milk production (13256290 L/hectare/year) not presenting statistical differences between de hi (11542290 L/hectare/year) and low (11392290 L/hectare/year) forage mass offer. A medium forage offer during the whole year grants the best productive performance per hectare. Animal performance in dairy cows diverges with forage mass offer, existing an interaction between seasons, where during the attumn presented negative correlations with forage mass offer below 26.8 Kg of DM/cow/day. During the spring there was a quadratic relation between forage mass offer and animal performance, were the greatest animal performance was obtained with forage mass offers of 33.7 Kg of DM/cow/day. Seasonal variation in forage growth rate, and stocking rate were affected by forage mass offer, where the medium forage mass offer treatment presented the highest milk production since it presented also a high forage growth rate and a high stocking rate along the houle year.