Animal Health, Welfare Nutrition

Salmon protein hydrolysate (SPH) is made from fresh by-products from farmed salmon that are minced and acidified to hydrolyse proteins into peptides and free amino acids. The objective of this study was to evaluate SPH in young pigs compared to soy protein concentrate (SPC), fish meal (FM) and combinations hereof. Five diets were composed, all fulfilling the nutrient recommendations for young pigs. All diets contained 172 g soy bean meal/kg. One diet was supplemented with 123 g SPH/kg, and equivalent protein was supplied as SPC or FM in two other diets. Two diets were composed by combining half the amount of SPH and SPC or half the amount of SPH and FM. One week after weaning, one hundred individually housed pigs were allocated to one of five diets (n = 20) and fed ad libitum for four weeks. Pigs fed the SPH and SPH + FM diets ate 12-14% more (P<0.05) than pigs fed the SPC diet, but the results on gain and feed utilization was not significantly different among treatments. No differences were observed in faeces characteristics when scored by visual judgment during two 5-d periods. In conclusion, pigs responded equally to diets containing SPH and FM, and SPH resulted in greater feed intake than SPC.

Milk yield is reduced by pregnancy, and the present experiment was conducted to study the biological basis for the negative effect of pregnancy on milk yield. A total of 16 dairy cows were fed at either a normal or a low feeding level (eight cows per treatment), and half of them were inseminated after approximately 3 months of lactation and the other half were not inseminated. Mammary biopsies were taken at approximately 9 months of lactation. The milk yield of pregnant cows was reduced by 2.6 kg/day, and lactation persistency was reduced already from the time of insemination. Low feeding level reduced the milk yield by 9.8 kg/day from week 8 to week 39 of lactation, whereas no interaction between pregnancy and feeding level was found. Cell proliferation (Ki-67) and apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling, TUNEL) were unaffected by feeding level, and pregnancy tended to reduce cell proliferation but had no effect on apoptosis. Reduced cell proliferation may explain the reduced lactation persistency in pregnant cows. Transcription of oestrogen receptor a, progesterone receptor A and B, and long and short isoforms of the prolactin receptor were higher in pregnant cows compared with non-pregnant cows. Feeding level did not mediate changes in transcription of genes. Transcription of other cell-turnover-related genes (IGF-I, IGF binding protein-5, caspase-3) as well as genes related to the secretory activity of the cells (a-lactalbumin and acetyl CoA carboxylase a) was not affected by pregnancy or by feeding level.

Mammary gland development in sheep occurs mainly during puberty and pregnancy. We have investigated the effects of a late gestation feed restriction on mammary gland development in sheep. Five control ewes were slaughtered d −38 from parturition, whereas 10 ewes were fed ad libitum and another 10 ewes were fed restrictedly (50% of energy and protein requirements) the last 38 days of pregnancy. Half the ewes in each feeding treatment group were slaughtered d −6 from parturition. Both mammary glands were collected at slaughter. From the remaining five sheep in each feeding group, blood and mammary biopsies were collected on d −16, d −6, d 5 and d 30 from parturition. Fetus weights, weight of mammary parenchyma, amount of mammary epithelium and rate of mammary cell proliferation increased from d −38 to d −6 from parturition, but was not significantly affected by late gestation feed restriction. Colostrum yield was reduced (P = 0.02) by feed restriction, but milk yield at d 5 and d 30 was not (P = 0.12). Mammary gene expressions of alpha-lactalbumin (P = 0.97), leptin (P = 0.36), Bcl-2 (P = 0.35), Bax (P = 0.21), insulin-like growth factor I (IGF-I) (P = 0.81) and cyclin D1 (P = 0.43) were not affected by feed restriction, although plasma IGF-I (P = 0.13) and leptin (P = 0.04) concentrations were reduced by feed restriction. Our results suggest that extensive mobilization of body tissues occurred during late gestation feed restriction, which compensated for the reduced dietary nutrient supply, thereby maintaining fetal and mammary gland development, and this was likely explained by a high initial level of body fat in the experimental ewes. The colostrum yield was impaired by feed restriction, but our results show that in multiparous sheep, adequate post-partum nutrition can support lactational performance. In conclusion, mammary redevelopment in between successive lactations is not significantly affected by feed restriction during late pregnancy in fat sheep.

Expression levels of genes related to cell turnover and lactogenesis. PP and MP = primiparous (broken line) and multiparous (solid line) glands, respectively. Values are relative to d 1 of MP glands and are least squares means with 95% confidence limits. P-values for stage of gestation-lactation (S), parity (P), and their interaction (P*S) are presented in each graph. BCL2 = B-cell CLL/lymphoma-2; IGF1 = insulin-like growth factor I; IGFBP3 = insulin-like growth factor binding protein III; IGFBP5 = insulin-like growth factor binding protein V; TGFB1 = transforming growth factor β I; TGFB1R2 = transforming growth factor β I receptor II; PRLR = prolactin receptor; LALBA = α-lactalbumin; LTF = lactoferrin; LPT = leptin; LPTR = leptin receptor.

The present study aimed to 1) elucidate whether continuous milking during late gestation in dairy goats negatively affects mammary remodeling and hence milk production in the subsequent lactation, and 2) identify the regulatory factors responsible for changes in cell turnover and angiogenesis in the continuously lactating mammary gland. Nine multiparous dairy goats were used. One udder half was dried off approximately 9 wk prepartum (normal lactation; NL), and the other udder half of the same goat was milked continuously (continuous lactation; CL) until parturition or until the half-udder milk yields had dropped to below 50 g/d. Mammary biopsies were obtained from each udder half just before the NL gland was dried off (before dry period), within the first 2 wk after drying-off (early dry period, samples available only for NL glands), in the mid dry period, within the last 2 wk before parturition (late dry period), and at d 1 (the day of parturition), 3, 10, 60, and 180 of lactation. Mammary morphology was characterized in biopsies by quantitative histology, and cell turnover was determined by immunohistochemistry (terminal deoxynucleotidyl transferase dUTP nick end labeling and Ki-67). Transcription of genes encoding factors involved in mammary epithelial cell (MEC) turnover and vascular function was quantified by quantitative reverse transcription PCR. Results demonstrated that omitting the dry period was possible in goats but was not as easy as claimed before. Renewal of MEC was suppressed in CL glands, which resulted in a smaller MEC population in the subsequent lactation. At the time of parturition (and throughout lactation), the mammary glands subjected to CL had smaller alveoli, more fully differentiated MEC, and a substantially larger capillary fraction compared with NL glands. The continuously lactating gland thus resembled a normally lactating gland in an advanced stage of lactation. None of the studied genomic factors could account for these treatment differences. The described characteristics in CL glands compared with NL glands indicated a gland maintained in lactation for a longer period. Figure 1.