Impact of 48-h water and feed deprivation and hydroxychloride sources of copper and zinc on the metabolism and performance of grazing Nellore cattle during the dry period.

Procedures such as transport and marketing can subject animals to water and feed deprivation and impair animal health and performance. Maintaining the mineral status of animals under these conditions can bring benefits to health and performance. The use of hydroxychloride mineral sources can improve mineral status, nutrient digestibility and performance. Two studies were conducted to investigate how the supplementation of 02 trace mineral sources of Cu and Zn and 48-hour water/feed deprivation would affect the performance and metabolism of grass-fed beef cattle. In the first study, 20 castrated and rumen-canulated Nellore steers (BW = 350 ±â€¯132 kg; 20 m) were distributed in individual pens, in a 2 × 2 factorial arrangement: supplemental Cu and Zn sources from inorganic vs hydroxychloride (HTM) and 48-hours deprivation (WFD) vs unrestricted (WFU) access to water and feed. The 57d of study was divided into two periods: (1) Adaptation from -21d to -1d and (2) evaluation from 0d to 36d. Interaction between deprivation × period was detected (P < 0.05) for digestibility of DM (DMD), organic matter (OMD), neutral detergent fiber (NDFD), and acid detergent fiber (ADFD). Deprivation increased DMD, OMD, NDFD, and ADFD immediately after the deprivation period (3-5d), but impaired digestibility at longer periods such as 11-13d and 32-34d. DM (DMI) and nutrient intake (P = 0.075), as well as NDFD were higher in HTM. Several ruminal parameters were affected by deprivation: short-chain fatty acids concentration decreased, while rumen pH increased (deprivation × time; P < 0.05); decreased propionate, butyrate and increased isobutyrate, isovalerate, and valerate in WFD (deprivation × time; P < 0.05), respectively. In the second study, eighty-four intact Nellore males (BW = 260 ±â€¯35 kg) were blocked by BW and randomly assigned to Urochloa brizantha cv. Marandu paddocks for 131d in a 2 × 2 factorial arrangement. Liver Cu was higher in WFU/HTM animals (mineral × deprivation; P < 0.05). Interaction between deprivation × period (P < 0.05) was detected for BW and average daily gain (ADG). On 2d and 12d after deprivation, WFD increased ADG and recovered the BW lost. In conclusion, water and feed deprivation imposed in these trials were able to impact several nutrient digestibility and ruminal fermentation parameters in short- and long-term. Performance was not affected by the studied factors. Furthermore, supplementation with sources of Cu and Zn hydroxychloride increased Cu in the liver and tended to increase DMI and NDFD.

Evaluation of somatic cell count thresholds to detect subclinical mastitis in Gyr cows.

The objectives of this study were (1) to determine the sensitivity (Se) and specificity (Sp) of somatic cell count (SCC) thresholds to identify subclinical mastitis in Gyr cows caused by major and minor pathogens; (2) to study the effects of month of sampling, rear or front mammary quarters, herd, intramammary infection (IMI), and bacterial species on SCC at quarter level; and (3) to describe the prevalence of IMI in Gyr cows in commercial dairy herds. In total, 221 lactating Gyr cows from 3 commercial dairy farms were selected. Milk samples were collected from individual quarters once a month for 1 yr from all lactating cows for SCC and bacteriological analysis. Mammary quarters were considered the experimental units and the SCC results were log(10)-transformed. Four SCC thresholds (100, 200, 300 and 400 × 10(3) cells/mL) were used to determine Se and Sp to identify infected mammary quarters. The overall prevalence of IMI in quarter milk samples of Gyr cows was 49.8%, and the prevalence of minor pathogens was higher (31.9%) than that of major pathogens (17.8%). Quarter samples with microbial isolation presented higher SCC compared with negative samples. Sensitivity and Sp of selected SCC thresholds varied according to the group of pathogen (major and minor) involved in the IMI definition. Sensitivity increased and Sp decreased when mammary quarters with only major pathogens isolation were considered positive. The use of a single SCC analysis to classify quarters as uninfected or infected in Gyr cows may not be a useful test for this breed because Se and Sp of SCC at the studied thresholds were low. The occurrence of IMI and the bacterial species are the main factors responsible for SCC variation in mammary quarters of Gyr cows. Milk samples with major pathogens isolation elicited higher SCC than those with minor pathogens.

Morfometria e distribuição de leite alveolar e cisternal na glândula mamária de vacas Holandesa e Girolanda / Morphometry and cisternal and alveolar milk distribution in mammary gland of Holstein and Girolanda cows

Estudaram-se a distribuição do leite nas porções alveolar e cisternal e a morfometria da glândula mamária de 14 vacas, sete da raça Holandesa, grupo H, e sete da Girolanda, grupo G, com ordem e dias de lactação semelhantes, ordenhadas duas vezes ao dia. A produção de leite foi mensurada diariamente, enquanto as frações de leite cisternal e alveolar foram medidas uma vez por semana. Durante o experimento, também foram realizadas medidas de ultrassonografia e morfometria da glândula mamária. As vacas Girolandas apresentaram úberes e tetos maiores que as vacas Holandesas. Diâmetro, espessura da parede e comprimento do canal do teto, medidos por imagens de ultrassom, também foram maiores nas Girolandas, mas a área de cisterna da glândula mamária foi maior nas Holandesas. Não houve diferença na produção de leite e nas frações de leite cisternal e alveolar entre as raças.

The milk distribution in alveolar and cisternal portions and the mammary gland morphometry were studied using 14 cows, being seven Holstein and seven Girolanda, with same parity and days in lactation, and milked twice a day. Milk yield was measured everyday, whereas alveolar and cisternal fractions were determined once a week. During the experiment, ultrasound scan measurements and morphometrical measures of the mammary gland were also performed. Girolanda cows had udder and teats larger than Holstein cows. Diameter, wall thickness, and length of the teat channel measured from ultrasound images were higher in Girolanda group, but cisternal area of the mammary gland was larger in Holstein cows. No differences in milk yield and cisternal and alveolar milk fractions between the studied breeds were observed.

Produção de leite, leite residual e concentração hormonal de vacas Gir x Holandesa e Holandesa em ordenha mecanizada exclusiva / Milk yield, residual milk, oxytocin concentration and cortisol release in Holstein and Gir x Holstein cows machine milked without stimulus from a calf

Avaliaram-se as concentrações de ocitocina e de cortisol e as produções de leite e de leite residual de três grupos genéticos de vacas: ½ Gir X ½ Holandês (n=6, grupo genético F2), » Gir X ¾ Holandês (n=6, grupo genético F3) e Holandês (n=6, grupo genético H), ordenhadas mecanicamente e na ausência dó bezerro. O grupo genético H produziu mais leite do que os grupos F2 e F3, e a concentração de ocitocina foi semelhante nos três grupos. O aumento de ocitocina durante a ordenha foi maior para os grupos H e F3 em relação ao grupo F2. O leite residual do grupo F2 foi maior do que o dos grupos genéticos F3 e H. O cortisol do grupo F2 foi maior do que o das vacas dos demais grupos genéticos. Vacas dos grupos F2 e F3 foram mais estressadas durante a ordenha do que vacas do grupo H, mas as dos dois grupos genéticos cruzados liberavam suficiente quantidade de ocitocina que permitiu a ejeção efetiva de leite.