M.R. Sanz Sampelayo

Effects of concentrates with different contents of protected fat rich in PUFAs on the performance lactating Granadina goats: Part II. Milk production and composition

Abstract With the aim of obtaining higher quality goats milk, three groups of Granadina goats in the middle of their second lactation were fed diets consisting of forage and concentrate fractions. To the concentration fractions was added 0, 9 or 12% of a fat protected against rumen metabolism that was particularly rich in polyunsaturated fatty acids (PUFAs). The composition of the protected fat was determined as was the milk yield and the chemical composition of the milk. The PUFAs content of the protected fat was 14.3%, with the degree of saponification equal to 84.9%. Daily milk production and milk dry matter, protein, fat and lactose concentration did not vary significantly in relation to diet. In all cases, all values depended on the corresponding energy intake. However, milk fat from goats fed protected fat contained higher concentrations of PUFAs. Also, fat addition caused some differences in the fractional composition of milk protein. It is concluded that milk fat from goats can be modified by nutritional means to obtain a healthier product.

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.

Utilization of goat milk vs. milk replacer for granadina goat kids

Abstract Nutritional responses of Granadina goats fed goat milk or milk replacer were studied. Digestibility of nutrients, metabolizable energy, animal growth and performance were analyzed. In a factorial design, two sources of milk (goat milk and milk replacer), were fed at three levels (1.24, 1.86 and 2.48 times the energy required for maintenance) and two animal ages (15 and 30 days). The patterns of abomasal emptying and abomasal flow composition were determined also in goat kids fed goat milk or milk replacer ad libitum. Nutrient digestibilities and metabolizable energy were greater in goats on goat milk than on milk replacer, and in goats 30 days of age than 15 days of age. Animal growth was similar in goats fed goat milk or milk replacer. Performance indicated greater fattening in goats fed goat milk than milk replacer, and in goats 30 days of age than 15 days of age. Protein and fat left the milk-fed abomasum more regularly at a slower rate of emptying than when kids were fed milk replacer. The pattern of abomasal emptying in goat kids was similar to other pre-ruminant animals. In conclusion, experimental animals made suitable use of milk replacer. Greatest differences were observed against goat milk feeding for ash digestibility and fat deposition.

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.

Production of healthier goat milk. Use of a concentrate supplemented with a "protected" fat rich in PUFA.

In order to obtain healthier goat milk as far as its fat composition is concerned, milk production and composition trials were carried out with Granadina goats kept in semi-extensive breeding conditions. The animals were feeding indoors with a concentrate supplemented or not with 7% of fat conveniently protected against the action of rumen, which had 35% of polyunsaturated fatty acids (PUFA). The amount of milk produced was higher (p<0.05) with consumption of the fat supplemented concentrate. At the same time, and although there was no difference in the milk concentration of fat and protein nitrogen (p>0.05), the corresponding yields were higher for consumption of the fat supplemented concentrate. As for the composition of milk fat, the use of the supplemented concentrate resulted in fat with a higher (p<0.05) concentration of PUFA and a lower (p<0.05) concentration of stearic acid. At the same time, the concentration of medium chain triglycerides, which is the specific nutritional value particular to goats’ milk, was the same whichever concentrate was consumed.ResumenCon objeto de obtener una leche de cabra más saludable en relación con la composición de su grasa, se llevan a cabo unos ensayos de producción de leche y control de su composición, en cabras de raza Granadina, mantenidas bajo condiciones prácticas de explotación semiextensiva. Los animales se suplementan en pesebre con un concentrado que incluía o no un 7% de una grasa convenientemente protegida frente a la acción del rumen, la que presentaba en su composición un 35% de ácidos grasos poliinsaturados (PUFA). La cantidad de leche producida, resulta mayor (p<0.05) bajo el consumo del concentrado suplementado con la grasa. Al mismo tiempo, y si bien las concentraciones de grasa y nitrógeno proteico no muestran diferencias (p>0.05), los rendimientos correspondientes resultan mayores para el caso de consumo del concentrado suplementado con la grasa. Respecto de la composición de la grasa láctea, el empleo del concentrado suplementado da lugar a una grasa con una mayor (p<0.05) concentración de PUFA y menor (p<0.05) de ácido esteárico. Junto a esto, no varía la concentración de triglicéridos de cadena media, independientemente del tipo de concentrado consumido, aspecto en el que especialmente reside el particular valor nutritivo que presenta la leche de cabra.

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.

Body composition of goat kids during sucking. Voluntary feed intake

The body composition of thirty-eight Granadina goat kids was measured. Six animals were slaughtered at birth while the remainder were kept individually at an environmental temperature of 24 +/- 2 degrees and a relative humidity of 60 +/- 5%. They were given goats milk or a milk-substitute at two planes of nutrition until 15 or 30 d of age and then slaughtered. The goats milk and milk-substitute contained 260.4 and 222.0 g digestible protein/kg and 23.23 and 20.85 MJ metabolizable energy/kg respectively. Voluntary feed intake as metabolizable energy was a function of metabolic body-weight (kg W0.75), equivalent to 2.42 and 2.44 times the energy requirement for maintenance for goats milk- and milk-substitute-fed animals respectively. There was a high degree of correlation between the empty-body concentration of dry matter, fat and energy and empty-body-weight (P less than 0.001) or animal age (P less than 0.001), and between body-weight and animal age (P less than 0.001). The relationships between empty-body composition and empty-body-weight were independent of type of milk or plane of nutrition. In contrast relationships between empty-body composition or empty-body-weight and animal age were affected by the type of milk and, over all, by the plane of nutrition. All these results show that in these animals any body-weight will have a similar composition, but it will be reached earlier or later depending on dietary regimen and always with the limitation of voluntary intake.