A.U. Carvalho

Parâmetros fisiológicos de bovinos cruzados submetidos ao estresse calórico

The thermoregulation physiological responses in thermoneutrality and heat stress of crossbred calves (½Gir x ½Holstein), males and females, with age between 14 and 20 months were studied. The animals were submitted to thermoneutrality (22°C and 70% of relative humidity) and to heat stress (42oC and 60% of relative humidity) in summer and winter seasons in bioclimatic chamber. Rectal temperature (TR), respiratory rate (FR) and body surface temperature (BST) were registered at 6 AM and 4 PM. It was observed increase in TR, FR and BST in the heat stress period (P 0.05) was observed for BST.

Effects of milk replacer feeding strategies on performance, ruminal development, and metabolism of dairy calves

Performance, rumen development, and metabolism of male Holstein calves (n=54) were evaluated according to 1 of 3 liquid feeding strategies: 4 L of milk replacer (MR)/d until 60 d old (4 L-60 d), 6L of MR/d until 29 d old and 4 L/d from 30 to 60 d (6L-29 d/4 L-60 d), or 6L of MR/day until 60 d old (60 d-6L). Water and starter were provided ad libitum. Intakes of MR and starter were monitored daily and body weight (BW) weekly. Blood samples for glucose and insulin concentrations and ruminal content samples for volatile fatty acids and ruminal ammonia concentrations were collected at 15, 30, 45, 60, 75, and 90 d of age. Six calves on each treatment were euthanized at 30, 60, and 90 d of age. Empty weights of forestomach and abomasum, papillae length, and mitotic index were measured. Average MR intake/d (expressed as a percent of BW) was greater for calves receiving 6L/d than for those receiving 4 L/d until 30 d of age. Calves on the 6 L-29 d/4 L-60 d had the smallest MR intake from 30 to 60 d old, followed by the 4 L-60 d and 6L-60 d treatments. Starter intake (kg of dry matter/day) did not differ between groups. It increased from 0.065 kg/d in the first month to 0.386 kg/d in the second month, and to 2.065 kg/d after weaning. Weight gain was greater for calves fed more MR in the first month, but no difference was observed during the second month. After weaning, 6L-60 d calves had greater rate of weight gain than others and were heavier at 30, 60, and 90 d of age. Weight of empty forestomachs, ruminal pH, and ammoniac nitrogen concentration were not different among groups. Propionate concentration was lower for 6 L-60 d calves, but acetate and butyrate concentrations were not influenced by MR feeding strategy. Calves fed more MR until d 30 had greater ruminal epithelium mitotic index. The different MR feeding strategies did not influence papillae length or ruminal epithelium thickness. Lesions such as ruminal parakeratosis or hyperkeratosis were not observed. The MR feeding strategy did not affect glucose concentration, but insulin was higher in 6L-60 d calves than in the other groups. Glucose concentration increased with age, whereas insulin decreased until 45 d old, and then started to increase until 90 d. In conclusion, MR feeding strategy did not influence ruminal development. Feeding calves 6 L of MR/d over 60 d resulted in greater rate of weight gain without negative effects on starter intake or forestomach development. The weight advantage that 6L-60 d calves obtained preweaning was maintained until 90 d of age.

Mastite subclínica e relação da contagem de células somáticas com número de lactações, produção e composição química do leite em vacas da raça Holandesa

The subclinical mastitis occurrence and the relationship between somatic cell count (SCC) with parity, milk yield and milk chemical composition, were studied in Holstein cows. The study was carried out in farms belonging to the milk control program of the Associacao de Criadores de Gado Holandes de Minas Gerais. Data on lactation order, subclinical mastitis, SCC, milk production, fat contents and total protein contents were analyzed. There was a negative correlation between SCC and milk production and, correlations between SCC and percentage of fat and protein were positive. Higher lactation order cows showed higher SCC, and cows with SCC higher than 100,000 cels/ml showed less milk production.

Potencial forrageiro de cultivares de girassol produzidos na safrinha para ensilagem

The objective of this study was to evaluate some important agronomic traits for silage production of 12 hybrids and a variety of sunflower (Helianthus annuus L.) participant of the national assay of sunflower, in the agricultural year of 1996/97. The experiment was conducted from February to June 1997. The experimental procedure followed a randomized block design and the means values were compared by Student-Newman-Keuls test. Significant differences among hybrids for fresh and dry matter productions, leaf, head and stem percentages, stems circumference close the head, broken plants percentage and height of the plants were observed. No significant differences among hybrids for stems circumference close the ground, diameter of the head and laying plants percentage were found. The agronomic traits indicated that some hybrids of sunflower present potential to be used for silage production in double-cropping system, or during the drought.

Epidemiologic aspects of an outbreak of Trypanosoma vivax in a dairy cattle herd in Minas Gerais state, Brazil.

The aim of this study was to assess the epidemiological situation of bovine trypanosomiasis caused by Trypanosoma vivax in a dairy cattle herd from Igarapé, Minas Gerais state, Brazil. The herd was monitored from September 2007 to February 2009 by sampling blood for determination of packed cell volume (PCV), microhaematocrit centrifugation test of parasitaemia (MHCT), serology (IFA), morphological identification of T. vivax and molecular diagnosis by polymerase chain reaction (PCR). During all the experimental period, 25 animals were MHCT and PCR positive, considering that in each sample collection a mean of 70 animals was evaluated. The morphometric characteristics of trypomastigote forms confirmed the infection by T. vivax. The seroprevalence ranged from 7.4% in September 2007 to 48% in February 2009, and the highest incidence observed could be correlated with an increased population of Stomoxys calcitrans flies in that region. Anaemia was the most important change found in infected animals, which showed lower averages of PCV than parasitologically negative animals (p<0.0001). Infected individuals showed lower averages of PCV than parasitologically negative animals (p<0.0001), indicating higher anaemia in the former compared with the latter group.

Clinicopathologic Features of Experimental Clostridium perfringens Type D Enterotoxemia in Cattle

This study was designed to experimentally reproduce enterotoxemia by Clostridium perfringens type D in cattle and to characterize the clinicopathologic findings of this disease. Fourteen 9-month-old calves were inoculated intraduodenally according to the following schedule: group 1 (n = 4), C. perfringens type D whole culture; group 2 (n = 3), C. perfringens type D washed cells; group 3 (n = 5), C. perfringens type D filtered and concentrated supernatant; group 4 (n = 2), sterile, nontoxic culture medium. In addition, all animals received a 20% starch solution in the abomasum. Ten animals from groups 1 (4/4), 2 (3/3), and 3 (3/5) showed severe respiratory and neurologic signs. Gross findings were observed in these 10 animals and consisted of acute pulmonary edema, excessive protein-rich pericardial fluid, watery contents in the small intestine, and multifocal petechial hemorrhages on the jejunal mucosa. The brain of one animal of group 2 that survived for 8 days showed multifocal, bilateral, and symmetric encephalomalacia in the corpus striatum. The most striking histologic changes consisted of perivascular high protein edema in the brain, and alveolar and interstitial proteinaceous pulmonary edema. The animal that survived for 8 days and that had gross lesions in the corpus striatum showed histologically severe, focal necrosis of this area, cerebellar peduncles, and thalamus. Kochs postulates have been met and these results show that experimental enterotoxemia by C. perfringens type D in cattle has similar clinical and pathologic characteristics to the natural and experimental disease in sheep.

Desempenho de bezerros alimentados com dietas líquidas à base de leite integral ou soro de leite

Quinze bezerros da raca Holandesa, desaleitados aos 30 dias de idade, foram utilizados para avaliar os efeitos da inclusao de fontes proteicas alternativas, em substituicao as proteinas do leite integral, na formulacao de sucedâneos do leite. Os animais foram divididos em tres grupos: o grupo controle (C) - recebeu leite em po integral reconstituido; o grupo sucedâneo SL (soro/leite) recebeu 41,6% da proteina bruta (PB) vinda do concentrado proteico de soro (CPS), 23,1% do soro de leite e 35,3% do leite em po integral; e o grupo sucedâneo S (soro) recebeu 68% da PB vinda do CPS e 32% do soro de leite. O consumo de concentrado, feno, sal mineral e agua foi mensurado diariamente, enquanto o ganho de peso foi avaliado semanalmente. Nao houve diferenca (P>0,05) para o consumo de concentrado, sal mineral e agua entre os grupos, nos periodos avaliados. O consumo de feno e o ganho de peso foram inferiores nos animais do grupo S (P<0,05). A substituicao de 100% do leite integral por CPS e soro de leite influenciou negativamente o desempenho.

Parâmetros clínicos, hematológicos, bioquímicos e hormonais de bovinos submetidos ao estresse calórico

Clinical, haemathological, biochemical, and hormonal parameters were characterized in 39 males and 32 females crossbred cattle (½ Holstein x ½ Gir), averaging 14 to 20 months of age, submitted to thermoneutrality (22oC and 70% of RH) and heat stress (42oC and 60% RH) in summer and winter in climatic chamber. At clinical examination, all animals presented salivation and ocular globe retraction. Under heat stress, animals increased erythrocytes count, hemoglobin total concentration, hematocrit, concentraction of total proteins, urea, creatinin, sodium, potassium, chlorides, cortisol, urinary pH and density, and dry matter of feces (P 0.05). It was concluded that hematology, biochemical, and hormonal parameters are important to characterize the heat stress in cattle.

Taxa de sudação e parâmetros histológicos de bovinos submetidos ao estresse calórico

Coat thickness, sweat rate, and histological parameters were characterized in 39 males and 32 females crossbred cattle (½ Holstein x ½ Gir), averaging 14 to 20 months of age, submitted to thermoneutrality (22oC and 70% of relative humidity - RH) and heat stress (42oC and 60% RH) in summer and winter in a climatic chamber. Fur length and coat thickness were significantly higher in summer than winter, 1.58 and 1.04cm and 5.31 and 3.91mm, respectively (P<0.05). Skin histology showed that sweat gland area and distance of gland to epithelium was shorter in summer than in winter, 2,589 and 4,051µm and 294 and 344µm, respectively (P<0.05). It was concluded that the season influenced the coat thickness, the sweat glands disposal and activity to maximize thermic homeostasis control.

Prevalência e classificação das afecções podais em vacas lactantes na bacia leiteira de Belo Horizonte

The prevalence and classification of clinical foot problems of 469 lactating dairy cows were studied in 10 farms in the dairy region of Belo Horizonte, Brazil, managed in confinement systems. A total of 142 cows were considered affected and presented 534 lesions. The prevalence of affected cows was 30.3%, being 66.7% in the hind feet and 33.3% in the fore feet, with no difference between outer claw (49.2%) and inner claw (50.7%). The classification according to lameness showed, 105 animals classified as score 1, 9 as score 2, 15 as score 3, 7 as score 4 and 6 as score 5. Age of cow influenced the prevalence of lesions, but no effect of lactation stage was observed. The most frequent lesion was horn erosion representing 48.5% of the total, followed by interdigital dermatitis (13.5%) and septic pododermatitis (9.6%).