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Effect of CSN1S1 genotype and its interaction with diet energy level on milk production and quality in Girgentana goats fed ad libitum
- Renato Italo Pagano, Pietro Pennisi, Bernardo Valenti, Massimiliano Lanza, Adriana Di Trana, Paola Di Gregorio, Anna De Angelis, Marcella Avondo
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- Journal:
- Journal of Dairy Research / Volume 77 / Issue 2 / May 2010
- Published online by Cambridge University Press:
- 12 April 2010, pp. 245-251
- Print publication:
- May 2010
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A study was carried out to evaluate how the energy level of the diet can affect milk production and quality in Girgentana lactating goats in relation to polymorphism at the αs1-casein (CSN1S1) genotype locus. Twenty-seven goats, homogeneous for milk production (1·5±0·3 kg/d), days of lactation (90±10 d) and body weight (35·8±5·5 kg) were selected on the basis of their CSN1S1 genotype, as follows: nine goats homozygous for strong (AA) alleles, nine goats homozygous for weak alleles (FF) and nine goats heterozygous (AF). The goats were used in a 3×3 factorial arrangement of treatments, with three genotypes (AA, FF, AF) and three diets at different energy levels (100%, 65% and 30% of hay inclusion). The experiment consisted of three simultaneous 3×3 Latin squares for the three genotypes, with one square for each level of hay inclusion in the diet. All the animals were housed in individual pens. Each experimental period lasted 23 d and consisted of 15 d for adaptation and 8 d for data and sample collection, during which the goats received the scheduled diet ad libitum. The animals were fed three different diets designed to have the same crude protein content (about 15%) but different energy levels: a pelleted alfalfa hay (H100) and two feeds including 65% (H65) and 30% (H30) of alfalfa hay (respectively 1099, 1386 and 1590 kcal NE for lactation/kg DM). All the diets were ground and pelleted (6 mm diameter). AA goats were more productive than AF and FF goats (respectively: 1419 v. 1145 and 1014 g/d; P=0·002). Indeed the interaction energy level×genotype was significant (P=0·018): in fact AA goats showed their milk increase only when fed with concentrates. Differences in protein and in casein levels between the three genotypes were in line with results expected from the different allele contribution to αs1-casein synthesis. Milk urea levels were significantly lower in AA goats compared with AF and FF genotypes (respectively 32·7 v. 40·4 and 40·4 mg/dl; P=0·049) and significantly lower when goats were fed with 65H and 30H diets than with 100H diet (respectively 37·4 and 34·3 v. 41·7 mg/dl; P<0·001). Indeed, a significant interaction genotype×diet (P=0·043) occurred for milk urea, which was significantly lower in AA goats but only when fed with concentrates (65H and 30H). Blood concentrations of energy indicators (glucose, non-esterified fatty acids and beta-hydroxybutyric acid) were not influenced by genotype. The results confirm that strong alleles are associated with a greater efficiency of feed utilization and seem to show that a high energy level of the diet can further improve this efficiency.
Diet selection and milk production and composition in Girgentana goats with different αs1-casein genotype
- Marcella Avondo, Renato Italo Pagano, Anna Maria Guastella, Andrea Criscione, Marianna Di Gloria, Bernardo Valenti, Giuseppe Piccione, Pietro Pennisi
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- Journal:
- Journal of Dairy Research / Volume 76 / Issue 2 / May 2009
- Published online by Cambridge University Press:
- 13 March 2009, pp. 202-209
- Print publication:
- May 2009
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In goats, αs1-casein polymorphism is related to different rates of protein synthesis. Two genetic variants, A and F, have been identified as strong and weak alleles based on a production of 3·5 and 0·45 g/l of αs1-casein per allele. The aim of the trial was to test whether goats can select their diet as a function of their genetic aptitude to produce milk at different casein levels and whether this selection can influence milk production or composition. Two groups of 8 animals, homozygous for strong (AA) or weak (FF) alleles were housed in individual pens. Using a manger subdivided into five separate containers, the goats were offered daily for 3 weeks: 1·5 kg of alfalfa pelleted hay, 0·7 kg of whole barley, 0·7 kg of whole maize, 0·7 kg of whole faba bean and 0·7 kg of pelleted sunflower cake. Total dry matter intake was similar between groups and resulted in nutrient inputs much higher than requirements. On average, goats selected 86% of maize plus barley and only 46% of faba bean plus sunflower. Indeed, AA goats selected less faba bean compared with FF goats (37·2 v. 56·7% of the available amount; P=0·01); during week 2 and week 3 they significantly increased maize selection (respectively for week 2 and week 3: 94·9 and 99·1% v. 85·3 and 87·3%) thus increasing the ratio between the high-energy feeds and the high-protein feeds (2·41 v. 1·81, P=0·023). As for true protein, the high soluble fraction (B1) and the indigestible fraction (C) were lower in the diet selected by AA goats (respectively in AA and FF groups: B1, 7·85 v. 9·23% CP, P<0·01; C, 6·07 v. 6·30% CP, P<0·001); these diet characteristics can be associated with lower losses of protein. Milk production, being similar in AA and FF groups when goats were fed with a mixed diet, significantly increased in AA group, when free-choice feeding was given (mean productions: 1198 v. 800 g/d, P<0·01). Casein content was higher in AA group than in FF group (2·70 v. 2·40%, P<0·01) whereas milk urea was higher in FF group (59·7 v. 48·8 mg/dl, P<0·01). In conclusion, when the animals were free to select their diet, their higher genetic aptitude to produce casein seemed to adjust their energy and protein dietary input in qualitative terms, thus leading to an increase in milk production and a decrease in milk urea. These results seem to demonstrate that interactions probably occurred between genetic polymorphism at the αs1-casein locus, diet selection and the efficiency of nutrient transformation into milk.
Milk production and composition in Malagueña dairy goats. Effect of genotype for synthesis of αs1-casein on milk production and its interaction with dietary protein content
- Gloria de la Torre Adarve, Eva Ramos Morales, Juan Manuel Serradilla Manrique, Francisca Gil Extremera, M Remedios Sanz Sampelayo
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- Journal:
- Journal of Dairy Research / Volume 76 / Issue 2 / May 2009
- Published online by Cambridge University Press:
- 05 January 2009, pp. 137-143
- Print publication:
- May 2009
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A study was carried out to analyse the production and composition of milk from Malagueña goats of different genotypes for the content of αs1-casein. Twenty goats were used, half of them with a high (HG) and half with a low (LG) genetic capability for αs1-casein synthesis. Among the ten HG goats, seven had BB and three had AB genotypes, whereas there were seven EF and three FF genotypes among the LG goats. The goats were fed a diet differing in crude protein content, 136 and 177 g/kg dry matter for diet 1 (D1) and diet 2 (D2), respectively. For each genotype group, a trial was conducted, with each of the two diets in a two-period balanced change-over design, in which the milk production and composition were analysed. The genotype was found to determine milk composition, with that produced by the HG goats being higher in total solids, protein, αs1-casein, αs2-casein and fat. Analysis of milk production values and, especially, those of the yields of the different components, revealed an interaction between the factors. HG goats that consumed D1 were more productive than LG goats, but this ceased to be so when the D1 diet was replaced by D2. However, LG goats, although less productive than HG ones when the D1 diet was consumed, showed increased productive capacity when D1 was replaced by D2. The main difference for the fatty acid profile of the dairy fat is that the milk fat produced by the HG goats contained higher levels of short and medium-chain fatty acids. From these results, it is concluded that, in terms of favouring production, the advantage of replacing animals with a low capacity for αs1-casein synthesis with those of a high capacity seems to depend on the protein level in the diet. Similarly, the advantage of changing to a diet of higher protein content depended on the animal's genotype.