About 6 years ago dairy farmers within the European Union (EU) were given an alternative to the r... more About 6 years ago dairy farmers within the European Union (EU) were given an alternative to the ration dietary cation-anion difference (DCAD) principle in order to reduce the risk of milk fever (parturient hypocalcaemia) when the Commission of the European Communities (CEC) amended its list of accepted Additives and Products or Substances used in Animal Feed (Part B of the Annex to Directive 94/39/EC) by allowing ”synthetic zeolite” (synthetic sodium aluminium silicate) with the purpose of reducing the risk of milk. This was the result of CEC’s review of published and unpublished research based on the Danish invention of using zeolite for this particular purpose. Over a period of several years the Commission formed its opinion with regard to the intended effect of using zeolites, and to any potentially adverse side-effects on the cow, its calf, milk as a food, and the environment, before it finally accepted this novel use of zeolite in January 2008. The rationale for the underlying ...
The objective of this study was to determine the effects of feeding synthetic zeolite A for 3 wk ... more The objective of this study was to determine the effects of feeding synthetic zeolite A for 3 wk before expected calving on peripartal serum mineral concentrations, hypocalcemia, oxidant status, and performance. Holstein cows (n = 55) entering their second or greater lactations were assigned randomly to 1 of 2 dietary treatments starting 21 d before expected calving: control (CON: 40% corn silage, 33% wheat straw, and 27% concentrate; n = 29) or experimental [EXP: CON plus zeolite A (X-Zelit, Protekta Inc., Lucknow, ON, Canada/Vilofoss, Graasten, Denmark; n = 26) at an inclusion rate of 3.3% of dry matter, targeting 500 g/d as-fed]. Cows were fed the same postpartum diet and housed in individual tiestalls through 28 d in milk. Cows fed EXP had higher serum Ca concentrations as parturition approached and during the immediate postpartum period. Serum P concentrations were lower for the EXP-fed cows during the prepartum period and the first 2 d of lactation, whereas serum Mg concentrations were lower than those of the CON-fed cows only during the immediate periparturient period. Cows fed EXP had decreased prevalence of subclinical hypocalcemia (SCH) from d −1 through 3 relative to day of parturition, with the largest difference occurring within the first day postpartum. Prepartum dry matter intake tended to be decreased and rumination was decreased in cows fed EXP; however; postpartum dry matter intake, rumination, milk yield, milk component yield, and colostrum measurements did not differ between treatments. Cows fed EXP tended to have increased hazard of pregnancy by 150 d in milk when controlling for parity compared with CON-fed cows; potential reproductive benefits merit further study. This study demonstrated that zeolite A supplementation during the prepartum period results in markedly improved serum Ca concentrations around parturition and similar postpartum performance compared with controls and is effective at decreasing hypocalcemia in multiparous Holstein cows.
El objetivo general de esta tesis fue el estudio de la relacion entre longevidad reproductiva, re... more El objetivo general de esta tesis fue el estudio de la relacion entre longevidad reproductiva, rendimiento reproductivo y reservas corporales en conejas, asi como el cambio de estas relaciones con la seleccion. El efecto de la seleccion se estudio utilizando lineas seleccionadas. Se ha revisado la evidencia actual de los antagonismos entre reproduccion, produccion y longevidad y se presenta un marco de relacion entre condicion corporal, reproduccion y longevidad. En el primer trabajo se investiga el efecto de las reservas corporales y de la seleccion por tamano de camada sobre la longevidad reproductiva. Se comparan, utilizando embriones congelados, conejas cruzadas separadas 12 generaciones en el proceso de seleccion de las dos lineas maternales que intervienen en su produccion. La condicion corporal de las conejas se evaluaba a traves del espesor de la grasa peri-renal medida por ultrasonidos el dia 10 de lactacion durante los seis primeros partos. Se utilizo un modelo Cox de ries...
Abstract Calves are often lower in plasma vitamin E concentration than the recommended level (3 m... more Abstract Calves are often lower in plasma vitamin E concentration than the recommended level (3 mg/L) after weaning, which seems to be a challenge for a good immune response. Two studies were performed investigating if a natural vitamin E supplement in the starter concentrate could increase the plasma vitamin E concentration of calves around weaning. Each study was conducted at three Danish farms producing rose veal calves. Studies 1 and 2 included a total of 318 and 421 calves, respectively, from at least 3 weeks pre-weaning until at least 2 weeks after weaning. In study 1, the standard concentrate used at the farm was fed either unsupplemented (CON) or supplemented with 490 ± 24 (Means ± SD) mg of RRR-α-tocopherol (RRR-α-T)/kg of diet by mixing a vitamin E-enriched pellet with the standard concentrate pellet in the ratio of 1:10. In study 2, calves were fed either a common concentrate pellet with 48 ± 8 mg/kg all-rac-α-tocopheryl acetate (CON) or a common concentrate pellet with 245 ± 30 (Means ± SD) mg/kg RRR-α-T with a similar dietary composition. Performance data were analyzed for each farm per study; however, plasma parameters were analyzed across the three farms in each study. In both studies, the plasma vitamin E concentration was analyzed at start (approximately 3 weeks pre-weaning), at weaning, and 2 to 3 weeks after weaning; however, the concentrate intake and thus vitamin E intake was not recorded. In both studies, the overall average daily gain (ADG) from start to weaning was not affected by vitamin E supplementation. In study 1, the plasma vitamin E concentration at weaning in RRR-α-T calves (5.09 ± 0.58, LSmeans ± SEM) was higher (P = 0.01) than in CON calves (3.35 ± 0.55, mg/L). Similarly, the plasma vitamin E concentration post-weaning in RRR-α-T calves (3.71 ± 0.27) was markedly higher (P
Un total de 130 conejas, 59 de una línea (V) seleccionada intra-línea por tamaño de camada al des... more Un total de 130 conejas, 59 de una línea (V) seleccionada intra-línea por tamaño de camada al destete y 71 de una línea longevo productiva (LP) caracterizada por un mínimo de 25 partos y 7.5 gazapos nacidos vivos, fueron utilizadas para evaluar como afecta la exposición a distintos niveles de exigencias reproductiva a la respuesta de las conejas durante su 2ª lactación. Para ello, se constituyeron en ambas líneas tres grupos experimentales: PP9 (cubrición previa post-parto y con 9 gazapos), PD9 (cubrición previa post-destete y con 9 gazapos) y PD5, (cubrición previa post-destete y con 5 gazapos). La ingestión de pienso fue mayor para la línea LP (322 ± 4 g /d) que para la línea V (304 ± 5 g /d). La producción de leche de las conejas de la línea LP fue mayor (214 ± 3 g/d) que en la línea V (194 ±3 g/d), especialmente en los grupos experimentales de tamaño de camada alto (+12 y +13% para los grupos PP9 y PD9, respectivamente). Las conejas de la línea LP presentaron un mayor peso vivo (4128 ± 41 g) que las de la línea V (4001 ± 45 g). Estas diferencias de peso vivo no fueron tan evidentes en el grupo PP9 (+46 ± 106 g), aumentaron en el grupo PD9 (+138 ± 103 g) y sólo fueron significativas para el grupo PD5 (+207 ± 103 g; P<0.05). Las conejas de la línea LP presentaban un mayor grosor de su grasa perirenal que las V en el día post-parto (+0.50 mm; P<0.01), pero no se observaron diferencias entre líneas a partir de dicho momento. Estos resultados confirman el importante papel de las reservas corporales sobre las capacidades reproductivas y de supervivencia de las conejas reproductoras.
The aim of this study was to characterize patterns of energy balance through lactation of cows ke... more The aim of this study was to characterize patterns of energy balance through lactation of cows kept under constant feeding conditions. Danish Holstein, Danish Red, and Jersey cows were studied during consecutive
... La condición corporal al momento de la monta, parto y día 10 de lactación no se ve afectado p... more ... La condición corporal al momento de la monta, parto y día 10 de lactación no se ve afectado por el tamaño de camada, mientras que existe una clara reducción del GGP al día 25 de lactación a medida que aumenta la pre-sión de lactación.Aunque estemos mostrando ...
The aim of this experiment was to investigate the effect of body condition and selection for prol... more The aim of this experiment was to investigate the effect of body condition and selection for prolificacy on the reproductive life span of female rabbits. The body condition was obtained by ultrasound measurement of the perirenal thickness of 166 crossbred does at day10 after parturition in 6 consecutive parities. Two genetic groups were included: the current generation of does crossbred between two lines, both selected within line for number of pups at weaning, and a control group consisting of animals from the same cross but from 12 generations earlier. This control population was obtained by use of cryopreservation techniques, and made a simultaneous comparison between animals of different generations possible. A proportional Cox model was used to obtain estimates of survival characteristics. Twelve generations of selection for litter size at weaning did not significantly affect reproductive life span. Animals in poor body condition were found to have a significantly (P b 0.05) higher risk of dying than animals in better condition. Also, animals with high body fat mobilisation had a higher risk of culling (P b 0.05) than animals with intermediate mobilisation. Animals with zero pups born alive were also found to have a high risk of culling (P b 0.001).
This study analyzed genetic and phenotypic variation in plasma GH during lactation in first parit... more This study analyzed genetic and phenotypic variation in plasma GH during lactation in first parity dairy cows. The heritability and repeatability were examined using an algorithm for separation of basal and peak concentrations and different power transformations. Blood samples were obtained 17 times during first parity in 85 Holstein, 67 Red Dane, and 62 Jersey cows and assayed for GH. Each breed comprised 2 genetic groups; thus, a total of 6 genetic groups were defined. Across genetic groups, cows were assigned to 1 of 2 total mixed rations with a low or a normal energy concentration. The separation algorithm identified only
An evaluation of a new maternal line (LP) of rabbits was carried out. This new line was founded f... more An evaluation of a new maternal line (LP) of rabbits was carried out. This new line was founded following a scheme similar to that applied in the selection for hyperprolificacy in rabbits or pigs. In this case, the selection criteria were hyperlongevity and an independent culling level near the average for prolificacy. Evaluation was carried out by comparison of the reproductive and longevity performance of the LP line with another maternal line recognized for good reproductive performance and standard longevity (V line). The results indicate that the LP line could be a valuable resource for inclusion in the current 3-way cross schema used in rabbit production, because females showed better survival ability and nearly the
The aim of the present study was to investigate differences in reproductive and body traits durin... more The aim of the present study was to investigate differences in reproductive and body traits during successive parities between two genetic lines. The LP line was constituted by means of selection of animals having an extremely high number of parities (at least 25) and an average reproductive performance compared to the V line selected for litter size at weaning during 31 generations. The two lines were found to have an equal reproductive performance in the first three parities, but the LP line had higher reproductive performance from the fourth parturition onwards. The low reproductive performance after the third parity in the V line was suggested to be caused by constrained environmental conditions in the test station. A line by parity interaction was also observed for body weight, since body weight declined going from the third to the fourth parity in the LP line but not the V line. Thus, it was concluded that hyper selection for reproductive longevity and average prolificacy succ...
The aim of this work was to evaluate the ability of a line selected for reproductive longevity (L... more The aim of this work was to evaluate the ability of a line selected for reproductive longevity (LP) to confront productive challenges compared to a line selected during 31 generations for litter size at weaning (V). A total of 133 reproductive rabbit does were used (72 and 61 from LP and V lines, respectively). Within each line, three groups with different levels of productive effort were planned: PP9, inseminated at day 4 after the first partum and with nine kits during the second partum, and inseminated after first weaning (30 days) and with nine (PW9) or five kits (PW5) during the second partum. The reproductive performance, body condition (perirrenal fat thickness (PFT)) and lipolytic response were controlled. LP does showed greater mean live weight (LW; +128 g;P< 0.05), PFT (+0.47 mm;P< 0.05) and estimated body energy (EBE; +0.29 MJ/kg;P< 0.01) than V does at second partum. However, LP does that mated at firstpost partumdid not significantly differ in EBE relative to V...
The objective of this study was to examine the effect of breed, parity and body fatness on the li... more The objective of this study was to examine the effect of breed, parity and body fatness on the lipolytic response of dairy cows. The lipolytic response was estimated as the plasma non-esterified fatty acid (NEFA) response to an adrenergic challenge. Four challenges per lactation were carried out on 124 Danish Holsteins, 101 Danish Red and 82 Jerseys through consecutive lactations. Within breed, there were two genetic lines. Cows were equally distributed across two feeding treatments, a normal and a low energy total mixed ration. Diet composition was constant throughout lactation. The lipolytic response was significantly affected by breed, parity and stage of lactation. Lipolytic response was greater in early lactation than other stages in lactation (P 0·001). The larger breeds had a higher lipolytic response than Jerseys (P 0·05), and showed an increase in lipolytic response between first and second parity (P 0·05), but not between second and third lactation. Lipolytic response in J...
About 6 years ago dairy farmers within the European Union (EU) were given an alternative to the r... more About 6 years ago dairy farmers within the European Union (EU) were given an alternative to the ration dietary cation-anion difference (DCAD) principle in order to reduce the risk of milk fever (parturient hypocalcaemia) when the Commission of the European Communities (CEC) amended its list of accepted Additives and Products or Substances used in Animal Feed (Part B of the Annex to Directive 94/39/EC) by allowing ”synthetic zeolite” (synthetic sodium aluminium silicate) with the purpose of reducing the risk of milk. This was the result of CEC’s review of published and unpublished research based on the Danish invention of using zeolite for this particular purpose. Over a period of several years the Commission formed its opinion with regard to the intended effect of using zeolites, and to any potentially adverse side-effects on the cow, its calf, milk as a food, and the environment, before it finally accepted this novel use of zeolite in January 2008. The rationale for the underlying ...
The objective of this study was to determine the effects of feeding synthetic zeolite A for 3 wk ... more The objective of this study was to determine the effects of feeding synthetic zeolite A for 3 wk before expected calving on peripartal serum mineral concentrations, hypocalcemia, oxidant status, and performance. Holstein cows (n = 55) entering their second or greater lactations were assigned randomly to 1 of 2 dietary treatments starting 21 d before expected calving: control (CON: 40% corn silage, 33% wheat straw, and 27% concentrate; n = 29) or experimental [EXP: CON plus zeolite A (X-Zelit, Protekta Inc., Lucknow, ON, Canada/Vilofoss, Graasten, Denmark; n = 26) at an inclusion rate of 3.3% of dry matter, targeting 500 g/d as-fed]. Cows were fed the same postpartum diet and housed in individual tiestalls through 28 d in milk. Cows fed EXP had higher serum Ca concentrations as parturition approached and during the immediate postpartum period. Serum P concentrations were lower for the EXP-fed cows during the prepartum period and the first 2 d of lactation, whereas serum Mg concentrations were lower than those of the CON-fed cows only during the immediate periparturient period. Cows fed EXP had decreased prevalence of subclinical hypocalcemia (SCH) from d −1 through 3 relative to day of parturition, with the largest difference occurring within the first day postpartum. Prepartum dry matter intake tended to be decreased and rumination was decreased in cows fed EXP; however; postpartum dry matter intake, rumination, milk yield, milk component yield, and colostrum measurements did not differ between treatments. Cows fed EXP tended to have increased hazard of pregnancy by 150 d in milk when controlling for parity compared with CON-fed cows; potential reproductive benefits merit further study. This study demonstrated that zeolite A supplementation during the prepartum period results in markedly improved serum Ca concentrations around parturition and similar postpartum performance compared with controls and is effective at decreasing hypocalcemia in multiparous Holstein cows.
El objetivo general de esta tesis fue el estudio de la relacion entre longevidad reproductiva, re... more El objetivo general de esta tesis fue el estudio de la relacion entre longevidad reproductiva, rendimiento reproductivo y reservas corporales en conejas, asi como el cambio de estas relaciones con la seleccion. El efecto de la seleccion se estudio utilizando lineas seleccionadas. Se ha revisado la evidencia actual de los antagonismos entre reproduccion, produccion y longevidad y se presenta un marco de relacion entre condicion corporal, reproduccion y longevidad. En el primer trabajo se investiga el efecto de las reservas corporales y de la seleccion por tamano de camada sobre la longevidad reproductiva. Se comparan, utilizando embriones congelados, conejas cruzadas separadas 12 generaciones en el proceso de seleccion de las dos lineas maternales que intervienen en su produccion. La condicion corporal de las conejas se evaluaba a traves del espesor de la grasa peri-renal medida por ultrasonidos el dia 10 de lactacion durante los seis primeros partos. Se utilizo un modelo Cox de ries...
Abstract Calves are often lower in plasma vitamin E concentration than the recommended level (3 m... more Abstract Calves are often lower in plasma vitamin E concentration than the recommended level (3 mg/L) after weaning, which seems to be a challenge for a good immune response. Two studies were performed investigating if a natural vitamin E supplement in the starter concentrate could increase the plasma vitamin E concentration of calves around weaning. Each study was conducted at three Danish farms producing rose veal calves. Studies 1 and 2 included a total of 318 and 421 calves, respectively, from at least 3 weeks pre-weaning until at least 2 weeks after weaning. In study 1, the standard concentrate used at the farm was fed either unsupplemented (CON) or supplemented with 490 ± 24 (Means ± SD) mg of RRR-α-tocopherol (RRR-α-T)/kg of diet by mixing a vitamin E-enriched pellet with the standard concentrate pellet in the ratio of 1:10. In study 2, calves were fed either a common concentrate pellet with 48 ± 8 mg/kg all-rac-α-tocopheryl acetate (CON) or a common concentrate pellet with 245 ± 30 (Means ± SD) mg/kg RRR-α-T with a similar dietary composition. Performance data were analyzed for each farm per study; however, plasma parameters were analyzed across the three farms in each study. In both studies, the plasma vitamin E concentration was analyzed at start (approximately 3 weeks pre-weaning), at weaning, and 2 to 3 weeks after weaning; however, the concentrate intake and thus vitamin E intake was not recorded. In both studies, the overall average daily gain (ADG) from start to weaning was not affected by vitamin E supplementation. In study 1, the plasma vitamin E concentration at weaning in RRR-α-T calves (5.09 ± 0.58, LSmeans ± SEM) was higher (P = 0.01) than in CON calves (3.35 ± 0.55, mg/L). Similarly, the plasma vitamin E concentration post-weaning in RRR-α-T calves (3.71 ± 0.27) was markedly higher (P
Un total de 130 conejas, 59 de una línea (V) seleccionada intra-línea por tamaño de camada al des... more Un total de 130 conejas, 59 de una línea (V) seleccionada intra-línea por tamaño de camada al destete y 71 de una línea longevo productiva (LP) caracterizada por un mínimo de 25 partos y 7.5 gazapos nacidos vivos, fueron utilizadas para evaluar como afecta la exposición a distintos niveles de exigencias reproductiva a la respuesta de las conejas durante su 2ª lactación. Para ello, se constituyeron en ambas líneas tres grupos experimentales: PP9 (cubrición previa post-parto y con 9 gazapos), PD9 (cubrición previa post-destete y con 9 gazapos) y PD5, (cubrición previa post-destete y con 5 gazapos). La ingestión de pienso fue mayor para la línea LP (322 ± 4 g /d) que para la línea V (304 ± 5 g /d). La producción de leche de las conejas de la línea LP fue mayor (214 ± 3 g/d) que en la línea V (194 ±3 g/d), especialmente en los grupos experimentales de tamaño de camada alto (+12 y +13% para los grupos PP9 y PD9, respectivamente). Las conejas de la línea LP presentaron un mayor peso vivo (4128 ± 41 g) que las de la línea V (4001 ± 45 g). Estas diferencias de peso vivo no fueron tan evidentes en el grupo PP9 (+46 ± 106 g), aumentaron en el grupo PD9 (+138 ± 103 g) y sólo fueron significativas para el grupo PD5 (+207 ± 103 g; P<0.05). Las conejas de la línea LP presentaban un mayor grosor de su grasa perirenal que las V en el día post-parto (+0.50 mm; P<0.01), pero no se observaron diferencias entre líneas a partir de dicho momento. Estos resultados confirman el importante papel de las reservas corporales sobre las capacidades reproductivas y de supervivencia de las conejas reproductoras.
The aim of this study was to characterize patterns of energy balance through lactation of cows ke... more The aim of this study was to characterize patterns of energy balance through lactation of cows kept under constant feeding conditions. Danish Holstein, Danish Red, and Jersey cows were studied during consecutive
... La condición corporal al momento de la monta, parto y día 10 de lactación no se ve afectado p... more ... La condición corporal al momento de la monta, parto y día 10 de lactación no se ve afectado por el tamaño de camada, mientras que existe una clara reducción del GGP al día 25 de lactación a medida que aumenta la pre-sión de lactación.Aunque estemos mostrando ...
The aim of this experiment was to investigate the effect of body condition and selection for prol... more The aim of this experiment was to investigate the effect of body condition and selection for prolificacy on the reproductive life span of female rabbits. The body condition was obtained by ultrasound measurement of the perirenal thickness of 166 crossbred does at day10 after parturition in 6 consecutive parities. Two genetic groups were included: the current generation of does crossbred between two lines, both selected within line for number of pups at weaning, and a control group consisting of animals from the same cross but from 12 generations earlier. This control population was obtained by use of cryopreservation techniques, and made a simultaneous comparison between animals of different generations possible. A proportional Cox model was used to obtain estimates of survival characteristics. Twelve generations of selection for litter size at weaning did not significantly affect reproductive life span. Animals in poor body condition were found to have a significantly (P b 0.05) higher risk of dying than animals in better condition. Also, animals with high body fat mobilisation had a higher risk of culling (P b 0.05) than animals with intermediate mobilisation. Animals with zero pups born alive were also found to have a high risk of culling (P b 0.001).
This study analyzed genetic and phenotypic variation in plasma GH during lactation in first parit... more This study analyzed genetic and phenotypic variation in plasma GH during lactation in first parity dairy cows. The heritability and repeatability were examined using an algorithm for separation of basal and peak concentrations and different power transformations. Blood samples were obtained 17 times during first parity in 85 Holstein, 67 Red Dane, and 62 Jersey cows and assayed for GH. Each breed comprised 2 genetic groups; thus, a total of 6 genetic groups were defined. Across genetic groups, cows were assigned to 1 of 2 total mixed rations with a low or a normal energy concentration. The separation algorithm identified only
An evaluation of a new maternal line (LP) of rabbits was carried out. This new line was founded f... more An evaluation of a new maternal line (LP) of rabbits was carried out. This new line was founded following a scheme similar to that applied in the selection for hyperprolificacy in rabbits or pigs. In this case, the selection criteria were hyperlongevity and an independent culling level near the average for prolificacy. Evaluation was carried out by comparison of the reproductive and longevity performance of the LP line with another maternal line recognized for good reproductive performance and standard longevity (V line). The results indicate that the LP line could be a valuable resource for inclusion in the current 3-way cross schema used in rabbit production, because females showed better survival ability and nearly the
The aim of the present study was to investigate differences in reproductive and body traits durin... more The aim of the present study was to investigate differences in reproductive and body traits during successive parities between two genetic lines. The LP line was constituted by means of selection of animals having an extremely high number of parities (at least 25) and an average reproductive performance compared to the V line selected for litter size at weaning during 31 generations. The two lines were found to have an equal reproductive performance in the first three parities, but the LP line had higher reproductive performance from the fourth parturition onwards. The low reproductive performance after the third parity in the V line was suggested to be caused by constrained environmental conditions in the test station. A line by parity interaction was also observed for body weight, since body weight declined going from the third to the fourth parity in the LP line but not the V line. Thus, it was concluded that hyper selection for reproductive longevity and average prolificacy succ...
The aim of this work was to evaluate the ability of a line selected for reproductive longevity (L... more The aim of this work was to evaluate the ability of a line selected for reproductive longevity (LP) to confront productive challenges compared to a line selected during 31 generations for litter size at weaning (V). A total of 133 reproductive rabbit does were used (72 and 61 from LP and V lines, respectively). Within each line, three groups with different levels of productive effort were planned: PP9, inseminated at day 4 after the first partum and with nine kits during the second partum, and inseminated after first weaning (30 days) and with nine (PW9) or five kits (PW5) during the second partum. The reproductive performance, body condition (perirrenal fat thickness (PFT)) and lipolytic response were controlled. LP does showed greater mean live weight (LW; +128 g;P< 0.05), PFT (+0.47 mm;P< 0.05) and estimated body energy (EBE; +0.29 MJ/kg;P< 0.01) than V does at second partum. However, LP does that mated at firstpost partumdid not significantly differ in EBE relative to V...
The objective of this study was to examine the effect of breed, parity and body fatness on the li... more The objective of this study was to examine the effect of breed, parity and body fatness on the lipolytic response of dairy cows. The lipolytic response was estimated as the plasma non-esterified fatty acid (NEFA) response to an adrenergic challenge. Four challenges per lactation were carried out on 124 Danish Holsteins, 101 Danish Red and 82 Jerseys through consecutive lactations. Within breed, there were two genetic lines. Cows were equally distributed across two feeding treatments, a normal and a low energy total mixed ration. Diet composition was constant throughout lactation. The lipolytic response was significantly affected by breed, parity and stage of lactation. Lipolytic response was greater in early lactation than other stages in lactation (P 0·001). The larger breeds had a higher lipolytic response than Jerseys (P 0·05), and showed an increase in lipolytic response between first and second parity (P 0·05), but not between second and third lactation. Lipolytic response in J...
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