F. Gil Extremera

Effects of concentrates with different contents of protected fat rich in PUFAs on the performance of lactating Granadina goats

The purpose of this study was to determine whether the use of different levels of a protected fat rich in polyunsaturated fatty acids (PUFAs) in the concentrate fraction of diets for lactating goats has any effects on feed intake, nutrient digestibility, N and energy utilisation for milk production. Three groups of six Granadina goats in the middle of their second lactation were used. They were fed diets of forage (50%) and concentrate (50%). The concentrate fraction contained either 0, 9 or 12% added fat. The added fat was protected against rumen metabolism and was particularly rich in PUFAs. The total feed intakes and the forage and concentrate intakes were determined for each case as were the digestibility of nutrients and the N and energy utilisation for milk production. A tendency to decrease total feed intake as the fat level increased was observed. The concentrate fraction intake and the DM digestibility for fat addition in the concentrate at 12% was lower (p<0.05) than that for the basal diet. Organic matter and energy digestibilities were lower (p<0.05) for fat addition in the concentrate at 12% than those for fat addition at 9% and for the basal diet. However, fat addition in the concentrate at 9 and 12% or only at 12%, brought about an increase (p<0.05) in fat digestibility or ADF digestibility, respectively. The ratio between N output in the milk and N ingested or N available for production for fat addition in the concentrate at 9% was higher (p<0.05) than that for the basal diet. Finally, the ratio between energy output in the milk and metabolisable energy available for production for fat addition in the concentrate at 12%, tended to be higher than those for fat addition in the concentrate at 9% and for the basal diet. From these results, it is concluded that the use in the concentrate fraction of diets for lactating goats of the protected fat here considered, gives rise to a good digestive utilisation of the diet together with improved N and metabolisable energy utilisation for milk production.

Evaluation of the allergenicity of goat milk, cow milk, and their lactosera in a guinea pig model.

The object of this study was to determine the allergenicity of goat milk (GM) and cow milk (CM) and that of their respective lactosera (GML and CML), by in vivo and in vitro assays. Two systemic tests for anaphylaxis were carried out in guinea pigs, the animals being sensitized orally with the 2 types of milk and lactosera. Sera were taken from the orbital sinus of the experimental animals at 0 and 22 d of the experiment to perform the serological study and the passive cutaneous anaphylaxis test. For the latter, the guinea pigs were sensitized passively with antibodies against the 4 antigen solutions. Enzyme-linked immunosorbent assay and Western blot were used to determine the specific antibodies of the isotypes immunoglobulin G1 and immunoglobulin G(Fc) developed against the same 4 antigen solutions. From these anaphylaxis and antibody-production tests, it was concluded that GM is hypoallergenic when compared with CM. The lactosera produced more closely grouped results, with values always below those of the corresponding milk. None of the proteins in the 4 immunizing solutions were identified as being their main allergen. These results show the hypoallergenicity of GM versus CM, and also that both casein and lactoserum proteins may be responsible for allergy in each case. To analyze the possibility of producing an innocuous food for those allergic to milk proteins, it would be of interest to identify the epitope(s) responsible for such allergenicity.

Effect of providing a polyunsaturated fatty acid-rich protected fat to lactating goats on growth and body composition of suckling goat kids

The aim of this study was to investigate the possibility of improving the composition of goat meat, in terms of the fatty acid composition of the different fat deposits. For this purpose, we used two groups of 12 female goats each of which had recently undergone a double birth. The animals were maintained under semi-extensive conditions and trough-fed with a concentrate that was either non-supplemented or supplemented with 50 g/kg of polyunsaturated fatty acids (PUFA)-rich fat protected against ruminant metabolism. The kid goats born to each group were suckled by their dams and a representative sample of each was slaughtered at 45 days after birth. The milk produced by the dams receiving the fat-supplemented diet contained fat with a lower content of saturated fatty acids and a higher content of n-3 PUFA, trans-C18: 1 and CLA. The kid goats suckled by these dams grew faster and the legs of the carcasses presented greater muscular development compared with the non-fat-supplemented diet group. The cover, intermuscular and intramuscular fat presented a different fatty acid composition, with a higher proportion of n-3 PUFA, trans C18: 1 and CLA, while that of n-6 PUFA remained unchanged. The change in the lipid metabolism of the kid goats was made evident by the blood levels of certain biochemical parameters. We discuss the improvement in the quality of the meat obtained, taking into account the feeding strategy provided and the class of animal in question.

Factors affecting pre- and post-weaning growth and body composition in kid goats of the Granadina breed

Thirty-two kid goats of the Granadina breed were used in four trials of three factors: milk type (goat milk and milk replacer), intake level (1·86 and 2·48 maintenance) and slaughter age (15, 30, 45 and 60 days). Weaning was carried out between the 31st and 45th days. The composition of the carcass and its different cuts and the development of the stomach compartments were studied. Both the high intake level and use of goat milk produced a statistically greater fat proportion in the carcass. At 30 days of age in kids given goat milk at the high intake level the fat proportion of the carcass was 130 g/kg. The variations in bone proportions were inverse to those for fat. The muscle proportions were affected by age, overall. The tissue composition of the different cuts showed similar responses to those in the carcass. The stomach compartments were affected most by age. The results show that kids of the Granadina breed have a good fattening capacity. The feeding and weaning system used here produced kids by 60 days of age with stomach compartments similar in proportion to those of adult goats.

Energy utilization for maintenance and growth in preruminant kid goats and lambs

Abstract Energy metaboclism of the Granadina kid goat and the Segurena lamb was analysed by an experiment on different feeding levels and comparative slaughter. The metabolizable energy (ME) intake, total energy retention, energy retained as protein and energy retained as fat were determined in both kinds of animal for their first 2 months of life. ME requirements for maintenance, ME efficiencies for energy retention and ME intake values at which protein retention and fat deposition begin to occur were estimated by the regression method. The estimated ME requirements for maintenance and ME efficiencies for energy retention were: 456 kJ per kg0.75 per day and 0.55 for kid goats, and 393 kJ per kg0.75 per day and 0.54 for lambs, respectively. Values of ME intake at which protein retention and fat deposition begin to occur were: 258 and 575 kJ per kg0.75 per day for kid goats, and 428 and 362 kJ per kg0.75 per day for lambs, respectively. According to the results obtained, it was deduced that kid goats compared with lambs show a higher ME requirement for maintenance together with a higher partial efficiency of ME utilization for protein retention and a lower partial efficiency of ME utilization for fat deposition.

Land snails as experimental animals: a study of the variability and distribution of individual weights in Helix aspersa snails born from the same clutch

A study was carried out to examine the distribution of individual weights in Helix aspersa snails, the aims being to establish the best estimate of the ponderal growth and also to obtain a model growth curve. Four groups of 20 snails from the same clutch were analysed and kept under experimental conditions from birth up to 6 months. The variability of their individual weights within groups was studied by calculating the coefficients of variation every 15 days. At the same time, the assumed normal distribution of those weights was being tested. The coefficients of variation increased with age and the assumed normal distribution of individual weights had to be rejected. By means of a log transformation of the original data, a model growth curve was constructed, and was used to assess the possibility of estimating age from weight. We finally reached the conclusion that median weight, rather than the mean, would be a better measure of central tendency to use until it is possible to obtain selected populations. The difficulty of estimating age from weight is emphasized.

Nutritional Utilization in Malagueña Dairy Goats Differing in Genotypes for the Content of αS1-Casein in Milk

A study was carried out with 20 goats of the Malagueña breed, half with a high (HG) and half with a low (LG) genetic capability for alpha(S1)-casein (AS1-CN) synthesis, to determine whether the 2 different genotypes (that cause differences in goat milk composition) are related to differences in nutritional feed utilization. Among the 10 HG goats, 7 had BB and 3 had AB genotypes for AS1-CN, whereas there were 7 EF and 3 FF genotypes in the 10 LG goats. The goats were fed diets differing in crude protein content (13.6 vs. 17.7% dry matter for diets 1 and 2, respectively). For each genotype group, a balance trial was conducted with each of the 2 diets in a 2-period balanced changeover designed with half the animals consuming diet 1 and the other half diet 2, determining individual feed intake and the utilization of N and energy in the diets. Greater voluntary feed intake on a metabolic body weight basis among the HG goats was identified as the first possible cause of their milk production. The HG goats also had a greater level of feed utilization, on a metabolic body weight basis, for N and energy intake. Greater ratios of N balance/ digestible N, milk protein N/digestible N, milk energy/ digestible energy, and milk energy/ME were found for HG goats compared with LG. These effects appear to be dependent on the level of protein in the diet, indicating interactive effects. The greater N and energy utilization of HG versus LG goats may explain the differences in milk composition between the 2 genotype groups.

Factors affecting the food intake, growth and protein utilization in the Helix aspersa snail. Protein content of the diet and animal age:

Food intake, growth and protein utilization were studied in the Helix aspersa snail by means of a nutritional balance experiment. This was designed in a 5·11 factorial arrangement involving 5 diets of different protein content (10·0, 12·5, 15·0, 17·5 and 20·0%) and 11 animal ages (ranging over 15 to 180 days of age). Dietary protein content and animal age determined food intake and protein utilization. The variations of dry matter and protein intake rates, growth rates, growth effeciency factors and protein retention rates, depending on dietary protein content or animal age were in agreement with what happens in other animals. These results suggest that there is no need to use diets with more than 17·5% of crude protein in these animals.

The effect of different concentrations of protein and fat in milk replacers on protein utilization in kid goats

The efficiency of utilization of protein for retention was analysed in pre-ruminant kid goats of the Granadina breed. Sixty male kids were used. Six were slaughtered at birth and the remaining 54 were offered different protein and fat intakes using nine different milk replacers. The protein concentrations were 200, 240 and 280g/kg dry matter (DM) and those of fat were 200, 240 and 280 g/kg DM. Animals were maintained on experiment until they were 60 days old. All were slaughtered on day 61. Nitrogen (N) balance trials were performed during the last 8 days of the 1st and 2nd months. Body composition of the animals slaughtered at birth and at 61 days were determined. Rates of energy retained as protein and as fat were determined (kJ/kg M 0·75 per day) and the corresponding rates of metabolizable energy intake as protein and as fat (kJ/kg M 0·75 per day) estimated. Once the relationships between the rates ofN retained and those of digestible N ingested had been established, it was evident that by increasing the protein content of the diet the efficiency of protein retention was decreased. In contrast, increasing the fat content of the milk replacer increased the efficiency of protein retention. The latter effect was noted for the milk replacers containing the high and medium levels of protein but not for those that contained the lowest level of protein, indicating that the level of protein was then the limiting factor. Having recorded this protein-sparing effect of the fat, the results obtained from the slaughter trials were used to develop generalized equations expressing the rates of energy retention in the form of protein or fat as a function of the rates of metabolizable energy intake achieved as both protein and fat. From the analysis of these equations conclusions are drawn about the variable contribution to protein retention in these animals of energy ingested as fat. This contribution depended on the energy intake achieved both in the form of protein and in the form of fat.

Physiological responses of pre-ruminant kid goats and lambs to different environmental temperatures.

The purpose of this study was to establish the metabolic behaviour of both preruminant kid goats and lambs, when they are kept at different environmental temperatures (12,24 and 30°C). The animals were fed ad libitum with a milk replacer for the first two months of life. Blood samples were taken from all the animals on days 30, 40, 50 and 60 post partum, to determine serum levels of glucose, insulin, free fatty acids, triiodothyronine (T3) and thyroxine (T4), both when fasting and 4 hours after starting feeding. The high sensitivity of both kinds of animal to the lowest of the environmental temperatures used, particularly for the first periods of life here considered, was established from the glucose/insulin and T3/T4 molar ratios and from the concentrations of free fatty acids. The results obtained by species were also evidence of metabolic behaviour typical of leanner animals in kids.ResumenEl objeto del presente estudio consiste en aclarar el particular comportamiento metabólico en el cabrito y en el cordero prerrumiante cuando se les mantiene a diferentes temperaturas ambientales (12, 24 y 30 °C). Los animales se alimentan ad libitum, en base a un mismo lactorreemplazante, durante sus primeros dos meses de vida. Los días 30, 40, 50 y 60 de edad se obtienen muestras de sangre de todos los animales, determinándose los niveles séricos de glucosa, insulina, ácidos grasos libres, triyodotironina (T3) y tiroxina (T4), tanto en ayuno como 4 h después de iniciada la toma de alimento. De los valores obtenidos para las relaciones molares de glucosa/insulina y T3/T4 así como las concentraciones de ácidos grasos libres, según clase de animal, temperatura ambiental, momento de toma de muestra y edad, se deducen la alta sensibilidad que ambas clases de animales muestran frente a la más baja de las temperaturas ensayadas, sobre todo durante sus primeros estadíos de vida. Igualmente y en función de las respuestas obtenidas según clase de animal, se deduce para cabritos un comportamiento metabólico típico de las especies de desarrollo más magro.