Phenotypically divergent classification of preweaned heifer calves for feed efficiency indexes and their correlations with heat production and thermography.

The aims of this study were (1) to assess if there is phenotypical divergence for feed efficiency (FE) during the preweaning phase; (2) if FE is correlated with heat production (HP) measured by the face mask method or (3) by surface skin temperature via thermography, and (4) whether these methods are applicable to preweaned calves. Holstein × Gyr heifer calves (n = 36, birth body weight = 32.4 ± 6.6 kg) were enrolled and on trial between 4 and 12 wk of age and were classified into 2 residual feed intake (RFI) and residual body weight gain (RG) groups: high efficiency (HE; RFI, n = 10; and RG, n = 9) and low efficiency (LE; RFI, n = 10; and RG, n = 8). Calves were fed milk (6 L/d) and solid feed (95% starter and 5% chopped Tifton 85 hay, as fed). Growth was monitored weekly and feed intake (milk and solid feed) daily, during the whole period. Gas exchanges (O2 consumption and production of CO2 and CH4) were obtained using a face mask at 45 ± 5 d of age and HP was estimated. Maximum temperatures were measured at 7 sites with an infrared camera at 62 ± 7 d of age. There was divergence in RFI and RG. Respectively, HE and LE calves had RFI of -0.14 and 0.13 kg/d, and RG of 0.05 and -0.07 kg/d. Dry matter intake was 15% lower in HE-RFI compared with LE-RFI, but no differences were observed in average daily weight gain. Within the RG test, no differences were observed in dry matter intake or average daily gain. The HE-RFI calves consumed less O2 (L/d) and produced less CO2 (L/d). Heart rate and HP were lower for HE-RFI calves compared with LE-RFI. Residual feed intake was correlated with HP (r = 0.48), O2 consumption (r = 0.48), CO2 production (r = 0.48), and heart rate (r = 0.40). No differences were observed in HP and gas exchanges between RG groups. Methane production was null in both groups. Eye temperature measured by thermography was 0.5°C greater in HE-RG than LE-RG calves. Differences in skin temperature between HE and LE calves were not observed at the other sites. These results support the hypothesis that calves are divergent for RFI, RG, and FE during preweaning and divergence tests are applicable during this phase. The face mask method described here is a useful tool for estimating differences in HP among phenotypically divergent RFI calves. Eye temperature measured by infrared thermography may have potential to screen phenotypically divergent RG calves.

Degradabilidade in situ do bagaço de cana-de-açúcar para pequenos ruminantes de raças naturalizadas do Nordeste brasileiro / In situ degradability of sugarcane bagasse for naturalized small ruminant breeds from the northeastern Brazil

Com o crescimento da indústria sucroalcooleira, buscam-se alternativas de uso dos resíduos gerados por ela. Os pequenos ruminantes de raças naturalizadas do Nordeste brasileiro mostram-se como grupos potenciais para que seja utilizado o bagaço de cana-de-açúcar (BCA) nas dietas. Nesse contexto, objetivou-se determinar a degradabilidade ruminal in situ da matéria seca (MS) e da fibra em detergente neutro (FDN) do BCA e os parâmetros ruminais em caprinos Moxotó e ovinos Morada Nova, fistulados no rúmen. Contidos em sacos de náilon, 3g de BCA foram incubados no rúmen nos tempos seis, 24 e 96 horas, determinando-se o conteúdo de MS e FDN nos resíduos obtidos. Nos tempos zero, seis e 12 horas após a primeira refeição, mediram-se no líquido ruminal pH e nitrogênio amoniacal (N-NH3) ruminal. O CMS não diferiu entre caprinos e ovinos. O potencial de máxima degradação da MS foi semelhante entre espécies, e da FDN foi superior em caprinos. Ovinos apresentaram maiores tempo de colonização, taxa de degradação e degradabilidade efetiva da MS e FDN. O pH não diferiu entre as espécies. Observou-se maior concentração de N-NH3 ruminal em caprinos, no tempo zero. Diante da maior velocidade de degradação da MS do BCA pelos ovinos, essa espécie se mostra detentora de uma microbiota ruminal com crescimento mais eficiente sobre o BCA.

With the increase of the sugar and alcohol industries, alternative uses for residue are sought, and the small ruminants from the naturalized breeds of northeastern Brazil are potential groups to make use of the sugarcane bagasse (SCB) in their diets. In this context, the objective was to determine the in situ degradability of dry matter (DM) and neutral detergent fiber (NDF) of SCB and ruminal parameters in Moxotó goats and Morada Nova sheep rumen fistulated. Three grams of SCB were placed in naylon bags and incubated in the rumen at 6, 24 and 96 hours, and the residues analyzed for DM and NDF. Rumen fluid was collected at zero, 6 and 12 hours after the first meal and pH and ammonia nitrogen (N-NH3) were determined. DMI did not differ between goats and sheep. The maximum degradation potential of DM was similar between species and the A of NDF was higher in goats. Sheep had higher colonization time, rate of degradation and effective degradability of DM and NDF. The pH did not differ between species. The highest concentration of ruminal N-NH3in goats was at time zero. Given the higher rate of degradation of bagasse dry matter by sheep, this specie shows a more efficient rumen microbial growth on SCB.

Digestibilidade da matéria seca de silagens de milho e de suplementos concentrados determinada por procedimentos in vitro / Dry matter digestibility of corn silages and concentrates determined by in vitro procedures

Compararam-se os valores de digestibilidade in vitro da matéria seca (DIVMS) de quatro silagens de milho e de seis concentrados (três proteicos e três energéticos), determinados pelo método de dois estádios realizados em tubos individuais ou em equipamento automatizado de fermentação, e avaliou-se a ocorrência de efeito associativo na digestão de alimentos destas três classes incubadas em um mesmo jarro de fermentação da incubadora in vitro, ou em jarros diferentes contendo a mesma classe de alimentos. Utilizou-se delineamento inteiramente ao acaso, em esquema fatorial 3 x 3 (procedimentos in vitro x classes de alimentos). Os valores de DIVMS determinados pelo método dos tubos foram mais próximos dos relatados na literatura e menores (P<0,02) que os obtidos pelos procedimentos automatizados. Não houve diferença (P>0,05) nos valores de DIVMS dos concentrados e das silagens de milho incubados no mesmo jarro de fermentação da incubadora ou, separadamente por alimento, em jarros diferentes.

The values of in vitro dry matter digestibility (IVDMD) of four corn silages and six concentrates (three proteic and three energetics) were determined by the two-stage technique that utilizes individual digestion tubes and by an automatic equipment of fermentation (filter bag technique). It was also evaluated the associative effect on digestion of these three food classes when incubated in the same fermentation jar of the "in vitro incubator" and when in different vessels containing the same class of foods. The experimental design was completely randomized in a 3 x 3 factorial arrangement (in vitro procedures x food classes). The IVDMD values determined in tubes were closer to those found in the literature and lower (P<0.02) than those obtained by the automatic procedure. No differences were found (P>0.05) in IVDMD of concentrates and silages when incubated together in the same fermentation jar or separated by food classes in separated jars.

Degradabilidade in situ da matéria seca de forrageiras tropicais obtidas em diferentes épocas de corte / In situ dry matter degradation of tropical forages harvested at different ages

Estimou-se a degradabilidade in situ de 10 forrageiras tropicais em três idades ao corte (21, 42 e 63 dias) e em três tempos de incubação (6, 24 e 96h). As forrageiras utilizadas foram: Andropogon gayanus cv. Planaltina, Brachiaria brizantha (acessos 3401, 3413 e 3451 CPAC), Cenchrus ciliaris (acessos 79119, 79146, 79148, 80199 e 81302 CPATSA) e Panicum maximum (3616 CPAC). Os acessos de B. brizantha, P. maximum e A. gayanus apresentaram os maiores valores de degradabilidade da matéria seca e os de C. ciliaris os valores mais baixos. Todas as forrageiras apresentaram queda no desaparecimento da matéria seca com o avanço da idade. Os acessos de Brachiaria brizantha 3413 e 3451 apresentaram as maiores degradabilidades efetivas.

Production and economic potentials of cattle in pasture-based systems of the western Amazon region of Brazil.

Our objectives were to evaluate strategies to improve productivity and economic returns from beef and dual-purpose cattle systems based on data collected on one dual-purpose (Bos taurus x Bos indicus) and two beef (Nellore) cattle farms in the western Amazon region of Brazil. Forage chemical composition and digestion rates of carbohydrate fractions of grazed Brachiaria decumbens and Brachiaria brizantha cv. Marandu grasses and Pueraria phaseoloides (tropical kudzu) legume were measured monthly during a 9-mo period from the end of one dry season to the end of the subsequent rainy season. Measurements of milk and growth responses to grazing these forages were used to predict animal productivity responses to dietary nutrient availability throughout an annual cycle. The ME available for gain in our simulations was always more limiting than metabolizable protein. The predicted ME available for gain was 0.50 kg/d for steers grazing B. brizantha and 0.40 kg/d for finishing steers grazing B. decumbens. Grasses contained more NDF and neutral detergent insoluble protein and less ME (P < 0.05) in the rainiest months than in the less rainy season, which resulted in 20% less predicted weight gain by growing steers (P < 0.05). Supplementation with sorghum grain was required to increase milk production and growth by 25 or 50% per animal, respectively, but this strategy was less profitable than current forage-only diets. Greater productivity of land and labor from higher stocking indicated greater net margins for beef production, but not for milk. This study suggested that more intensive beef production by judicious fertilization of grass-legume pastures and greater stocking density is the preferable strategy for owners of these cattle systems to improve economic returns under current conditions. It also might help decrease the motivation for additional forest clearing.

Consumo, digestibilidade aparente e balanço de nitrogênio em ovinos e caprinos alimentados com palha de soja / Intake, apparent digestibility and nitrogen balance in sheep and goats fed soybean straw

Determinaram-se as diferenças no consumo, balanço de nitrogênio e digestibilidade aparente das diversas fraçöes da palha de soja, em ovinos e caprinos, em um delineamento experimental inteiramente ao acaso. O consumo de matéria seca (MS) diferiu entre as espécies, 55,76 e 35,60g/kg elevado a 0,75 sobrescrito, respectivamente para ovinos e caprinos (P<0,05). Na digestibilidade da MS (por cento) näo foi detectada diferença significativa entre as espécies, 46,75 e 42,61 para ovinos e caprinos, respectivamente (P>0,05). As digestibilidade das fraçöes fribrosas (por cento) foram semelhantes (P>0,05), observando-se os seguintes valores para ovinos e caprinos, respectivamente: fibra detergente neutro, 43,62 e 40,00; fibra detergente ácido, 41,84 e 37,28; hemicelulose, 49,34 e 48,85 e celulose, 54,25 e 54,24. O balanço de nitrogênio foi positivo para ambas as espécies. Ovinos e caprinos apresentaram capacidade semelhante em digerir a palha de soja, porém os ovinos a consumiram em maior quantidade