Mammary sensitivity to protein restriction and re-alimentation

Goodwill, M.G.; Jessop, N. S.; Oldham, J. D.

doi:10.1079/bjn19960047

Cited by 5 publications

(3 citation statements)

References 36 publications

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“…This indicates the superior milking potential, on a relative scale, of the Holstein Friesian cow over the goat and sheep breeds used in the current study, which could be attributed to inherent qualities, or improved production characteristics through advances in breeding and better nutritional supplementation of diets. Dietary changes (Goodwill et al 1996), oxytocin (Nostrand et al 1991) and/or bovine somatotropin (bST) (Knight et al 1990) treatments and frequency of milking (Wilde et al 1987) have been observed to affect the mammary gland cell number, but whether such responses are caused by changes in proliferation rate or in death rate is not immediately clear. Since proliferation and death rate parameters are estimated using the mechanistic model, this offers an opportunity to analyse responses due to treatments within and across species.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of a mechanistic lactation model using cow, goat and sheep data

et al. 2010

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SU MMARYA mechanistic lactation model, based on a theory of mammary cell proliferation and cell death, was studied and compared to the equation of Wood (1967). Lactation curves of British Holstein Friesian cows (176 curves), Spanish Churra sheep (40 curves) and Spanish Murciano-Granadina goats (30 curves) were used for model evaluation. Both models were fitted in their original form using non-linear least squares estimation. The parameters were compared among species and among parity groups within species.In general, both models provided highly significant fits to lactation data and described the data accurately. The mechanistic model performed well against Wood's 1967 equation (hereafter referred to as Wood's equation), resulting in smaller residual mean square values in more than two-thirds of the datasets investigated, and producing parameter estimates that allowed appropriate comparisons and noticeable trends attributed to shape. Using Akaike or Bayesian information criteria, goodnessof-fit with the mechanistic model was superior to that with Wood's equation for the cow lactation curves, with no significant differences between models when fitted to goat or sheep lactation curves. The rate parameters of the mechanistic model, representing specific proliferation rate of mammary secretory cells at parturition, decay associated with reduction in cell proliferation capacity with time and specific death rate of mammary secretory cells, were smaller for primiparous than for multiparous cows. Greater lactation persistency of cows compared to goats and sheep, and decrease in persistency with parity, were shown to be represented by different values of the specific secretory cell death rate parameter in the mechanistic model. The plausible biological interpretation and fitting properties of the mechanistic model enable it to be used in complex models of whole-cow digestion and metabolism and as a tool in selection programmes and by dairy producers for management decisions.

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Section: Discussionmentioning

confidence: 99%

Evaluation of a mechanistic lactation model using cow, goat and sheep data

et al. 2010

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“…In the rat, substantial mammary development takes place following parturition (Knight & Peaker, 1982) and has been shown to be dependent on diet quality (Goodwill et al 1996~). Whether this pattern of development post-parturition occurs in other species is less clear since most studies have involved measuring mammary gland mass rather than an index of cell number (such as DNA content).…”

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“…Whether this pattern of development post-parturition occurs in other species is less clear since most studies have involved measuring mammary gland mass rather than an index of cell number (such as DNA content). The study of Goodwill et al (1996~) shows that there can be large changes in mammary-gland weight due to fat loss without changes in cell number.…”

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Protein metabolism during lactation

Jessop

1997

Proc. Nutr. Soc.

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West Mains Road, Edinburgh EH9 3JGLactation increases considerably the demand for amino acids over that required for basal needs. The demand imposed varies with the quantity of milk produced and, between species, with the protein content of milk. Using data on milk composition from Blaxter (1989) and assuming milk production of 60, 1000 and 50 000 ml/d for a rat, human subject and dairy cow respectively, the ideal protein required can be calculated as 5.7, 32 and 1465 g/d. (This calculation assumes the efficiency of use of the first limiting amino acid to be 0.85; Oldham, 1987). If this is expressed relative to the minimal requirement for amino acids, it gives a measure of the relative cost of lactation to the animal. Maintenance needs for amino acids can be considered to arise from obligatory losses occurring within the body (such as catabolism of amino acids, skin and hair loss) and those associated with protein loss to the gut. The latter varies with intake and, hence, dietary characteristics and has been estimated to account for 60 % of maintenance needs (Moughan, 1989). Thus, minimal requirements can be estimated as 40 96 of maintenance needs, calculated from Emmans & Oldham (1988). The relative amino acid cost of lactation for the rat, human subject and dairy cow, when producing the daily quantities of milk given previously are thus 11.0, 1-4 and 12.1 respectively. The cost for the rat and high-producing dairy cow are somewhat similar and substantially higher than that for human subjects. CAN SUCH ELEVATED REQUIREMENTS BE MET FROM DIETARY SUPPLY?Many studies have been conducted in our laboratories to determine the response of iactating rats to changes in the nutrient balance of the diet. We chose the rat as an experimental model as it has a substantially-elevated nutrient requirement during lactation and its digestive anatomy makes it easier to predict nutrient supply from the diet when compared with a ruminant. Intake varies markedly with the protein content of the diet such that DM intake is reduced at lower protein contents (Fig. l(a)). Our early work identified a threshold protein content of the diet below which the intakes of females were too low to support lactation (Friggens et al. 1993) and our subsequent studies have concentrated on diets in which the crude protein (N x 6.25; CP) content is varied between 210 and 90gkg DM by substitution with a mixture of fat and carbohydrate such that all diets are isoenergetic. A consequence of reduced intake during lactation is reduced lactational performance (as measured by the growth rate of a litter of twelve pups) and an increase in the rate of body-weight loss (Fig. 1). Thus, as amino acid supply from the diet is reduced through changes in intake and diet composition, so there is an increase in use of endogenous nutrients, body protein and fat. TO

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