During sows’ lactation substantial physiological changes occur, going from negative energy balance in early lactation to either zero or positive energy balance later in lactation (around day 15, Figure 4), which will affect the concentration of metabolites in plasma (Mosnier et al., 2010; Hansen et al., 2012a). When milk production is initiated, the requirement for milk synthesis rapidly increases and the feed intake can, however, not keep up with the increasing requirements for nutrients or the sows are not supplied enough. As a consequence sows become catabolic and start mobilizing nutrients to cover the requirement. The catabolism of body depots can to some extent be traced in blood plasma samples, and central plasma metabolites are described in the following:
In general plasma concentrations of insulin is closely tied to the circulating concentrations of glu- cose as insulin acts to lower glucose in plasma and keep glucose constant (Akers and Denbow, 2013). Furthermore, insulin acts to lower plasma concentrations of fatty acid and AAs and to pro- mote the conversion into storage (Cunningham and Klein, 2013). In contrast low plasma insulin will stimulate the catabolism of glycogen and mobilization of muscle and fat tissue, which will cov- er a part of the nutrient requirement. During the lactation period the general interpretation of the
a a b b a ab bc c a a b b 0 5 10 15 20 25 30 35 40
LELL LEHL HELL HEHL
Kg
role of insulin is, however, too simple to explain the observed changes in plasma insulin and plasma glucose and no clear explanation exists. It has, however, been suggested to be related to an altered distribution of nutrients and lowered insulin sensitivity in peripheral tissues during lactation. This favors the supply of nutrients to the udder (which is insulin independent) at the expense of other body tissues (Theil et al., 2012). The plasma concentration of insulin was found by Mosnier et al. (2010) to increase 4 hours post prandial, after parturition (from app. 24 to 38 µUI/mL) and decrease from day 4 of lactation until reaching a plateau at weaning (app. 12 µUI/mL). For plasma glucose the concentration slightly increases in early lactation (app. up to 0.93 g/L) and reduces throughout lactation (app. 0.78 g/L at weaning). The decrease in plasma insulin and plasma glucose in lactation is in contrast with the general understanding of insulin, because when insulin levels are high glu- cose levels should be the reverse.
Negative energy balance is associated with increased plasma non-esterified fatty acid (NEFA), which indicates that energy is mobilized from fat tissue. The urea concentration in plasma is indica- tive of oxidation of AAs and high levels indicate either breakdown of muscle tissues (to cover the requirements for energy, protein or individual AAs) or oxidation of excessive AA (imbalances of AA profile) supplied in the feed. Triglycerides (TAG) and lactate are mainly a response controlled by feed intake as TAG represents the quantity of fatty acids taken up from feed and lactate concen- tration to some extent reflects the amount of starch converted by lactic acid bacteria. However, lac- tate can also originate from the conversion of N and propionate in the liver or anaerobic metabolism in the muscles.
5 Long term consequences of suboptimal feeding
Commercially housed sows lose large amounts of BW during lactation and excessive weight loss due to negative energy balance during lactation has an unfavorable impact on sows in subsequent reproductive cycles (King and Williams, 1984; Whittemore, 1996). The catabolism of body tissues for maintaining milk production instead of conserving nutrients as reserves for the next reproduc- tive cycle affects the weaning to estrus interval (WEI) and litter size in subsequent reproduction (Zak et al., 1997). Culling of sows in commercial farms often happens because of reproduction fail- ures (Vestergaard et al., 2004).
Reproduction problems as a consequence of excessive weight loss have been found to affect repro- duction in several ways, including increasing interval from weaning to estrus, an increased inci-
dence of anestrus, a decreased conception rate, lower ovulation rate and higher embryonic mortality (Zak et al., 1997). In contrast reproductive problems may also arise around farrowing due to in- creased weight and condition by overfeeding during late pregnancy (Dourmad et al., 1994). These problems may be related to farrowing complication and metabolic disorders and studies have found that increasing the feed intake during late gestation increased the occurrence of agalactia (Persson et al., 1989) and the number of still born piglets (Persson et al., 1989; Cools et al., 2014).
The reestablishment of a new reproduction cycle is initiated after weaning when suppression of LH increases (Kemp, 1998). LH stimulates the follicle maturation and is essential for ovulation. The reproductive process is dependent on nutrient availability because depletion of body reserves during lactation establishes a hormonal background which affects follicular growth (Baidoo et al., 1992). When sows’ feed intake is low during lactation, the concentration of glucose is low as is the secre- tion of insulin and LH (Koketsu et al., 1996b; Koketsu et al., 1998). As a consequence the low LH secretion will adversely affect the WEI. The WEI seems to be similar in different parities although primiparous sows generally seem to be more sensitive than multiparous sows (Whittemore and Morgan, 1990).
Prolonged WEI has also been proven to depend on which body tissue is being mobilized (Reese et al., 1984). Reese et al. (1984) suggest that the WEI is more affected by catabolism of body fat than catabolism of muscle tissue during lactation. In contrast, King (1987) found a critical daily level of energy about 45 MJ DE for which the WEI is affected. A more recent suggestion for lactating sows is to keep weight loss in the range of approximately 15-25 kg (Theil et al., 2012).
The longevity and long term performance of sows are best accomplished by avoiding severe body loss and extreme fluctuations in BW and fat reserves (Aherne and Kirkwood, 1985; Eissen et al., 2000). Koketsu and Dial (1997) also found that ensuring a greater feed intake of sows during lacta- tion will improve the reproductive performance and thereby the longevity of sows. Furthermore, thin sows are also more prone to developing shoulder lesions, which has been implemented in Dan- ish culling strategies (Kaiser and Petersen, 2014). Continued selection for lean pigs will further re- duce the body fatness of sows and reduce feed intake (Eissen et al., 2000). Selection for higher feed intake or at least average daily weight gain should therefore be considered in further breeding. Reconstitution of body tissue in the subsequent reproductive cycle is not energetically and econom- ically favorable. The efficiency is lower when feed is deposited as body reserves and later mobi- lized (during lactation) due to oxidation, section 3.1. As a rule of thumb, it takes 4 kg of feed to gain
1 kg of BW. Deposition of 1 kg protein is associated with additionally 4.2 kg water and 1 kg fat is associated with additionally 0.17 kg water (Noblet and Etienne, 1987a). The equation for weight and water loss is:
Weight loss = 5.20(± 0.12) x protein mobilization + 1.17(± 0.12) x fat mobilization Water loss = 4.20 x body protein loss + 0.17 x body fat loss
Recalling the weight loss of 37 kg from Figure 5 for the LELL sows composed by a protein loss of 5.31 kg and a fat loss of 13.9 kg, the following calculations are made:
Weight loss = 5.20(± 0.12) x 5.31 + 1.17(± 0.12) x 13.9 = 44 kg Water loss = 4.20 x 5.31 + 0.17 x 13.9 = 24 kg
With the equation obtained from Noblet and Etienne (1987a) it is possible to approximately esti- mate the weight loss from protein and fat loss. Furthermore it is possible to calculate how much of the weight loss can be ascribed to water loss.
6 Final remarks and conclusion of literature review
- There may be a potential to further increase sows’ MY by paying attention to non-nutritional factors (e.g. litter size, litter weight or nursing frequency)
- Sows’ requirement for nutrients is more diverse according to differences in voluntary feed intake and MY
- It should be possible to generate a feeding curve more adapted to the energy requirement of the sow to avoid excessive weight loss during lactation
- Sows can be fed closer to their requirements in early lactation, but practical experience shows that voluntary feed intake is greatly reduced.
- The 1-diet feeding strategy used so far for lactating sows is not well balanced with nutrients required to support milk production during the entire lactation
- Negative energy balance should be avoided to improve sows’ longevity
- Avoiding weight loss during lactation improves feed efficiency and feeding costs
The literature review indicates the need for a feeding strategy for lactating sows that takes into account the individual sow’s requirements to cover maintenance and milk production. This is, however, not possible with a 1- diet feeding strategy.
MANUSCRIPT TO BE SUBMITTED
1 2
Running head: Nutrition of lactating sows 3
4 5
A 2-diet feeding regime for lactating sows reduces nutrient deficiency in early lactation and
6
improves milk yield1
7 8 9 T. F. Pedersen* 10 11 12
*Department of Animal Science, Faculty of Science and Technology, Aarhus University, DK-8830 13 Tjele, Denmark. 14 15 16 17 ________________________________________ 18 1
The research project was funded by the Ministry of Food, Agriculture and Fisheries of 19
Denmark, grant no. 3405-11-0342 20
2
Corresponding author: [email protected] 21
ABSTRACT: The objective of the present study was to evaluate whether a new feeding re-
23
gime composed of two diets throughout lactation could minimize sow weight loss and increase milk 24
yield (MY) and piglet weight gain. In total, 14 sows were included in the experiment from parturi- 25
tion until weaning 28 d later. The sows were fed one of two dietary feeding regimes from lactation 26
d 2 and throughout the lactation period. The 1-diet feeding regime represented the Danish feeding 27
standards and recommendations and the new 2-diet regime supplied sows feed according to their 28
individual requirement. The 2-diet regime was composed of a basal diet, formulated to cover the 29
energy requirement for maintenance and a lactation supplement formulated to cover the increasing 30
requirement for milk production. Sows’ feed intake and weight loss were affected by an interaction 31
between diet regime and treatment. In lactation wk 4 sows fed the 1-diet feeding regime produced 32
less milk (13.0 kg/d) than the sows fed the 2-diet regime (14.9 kg/d). Piglet weight gain was numer- 33
ically higher (P = 0.11) throughout the lactation period for sows fed the 2-diet regime. Sows in both 34
dietary regimes were in negative energy balance throughout lactation. Sows fed the 1-diet regime 35
were negative in N and Lys and reached a positive or zero balance in late lactation. For the 2-diet 36
feeding regime sows’ N and Lys balance was positive throughout lactation, and N loss was higher 37
for sows fed the 2-diet feeding regime. The concentration of urea in plasma was lower for sows fed 38
the 1-diet feeding regime. In conclusion feeding lactating sows with the 2-diet feeding regime 39
throughout lactation improved sows’ MY and mean piglet weight (as lactation progressed), and the 40
mobilization pattern was altered although the mobilization over the entire lactation period was not 41
affected. 42
Key Words: milk yield, nutrient balances, feeding regime, plasma metabolites.
43 44
INTRODUCTION
45The lactation period is an important part of the sow’s reproduction cycle and is crucial for 46
the survival of piglets. Sows’ milk yield (MY) has increased during the past decades and sows are 47
today able to produce 1.5 times their own weight in milk (Hansen et al., 2012b). Sows’ MY is, 48
however, relatively insensitive to manipulation by feeding e.g. additional supply of protein or fat 49
(Dourmad et al., 1998; Lauridsen and Danielsen, 2004). 50
During lactation substantial changes occur, and sows mobilize great amounts of nutrients 51
from body reserves (Theil, 2015). Typically, commercial sows lose 10-30 kg of BW during lacta- 52
tion even though they are fed ad libitum (Beyer et al., 2007; Smits et al., 2013; Cools et al., 2014), 53
but weight losses may be even higher (Kim et al., 2009).Excessive BW loss has an unfortunate 54
effect on the subsequent reproductive cycle by e.g. delaying return to estrus (King and Dunkin, 55
1986; Zak et al., 1997). Furthermore, in the long run, it is not energetically efficient to use body 56
depots to support MY instead of using energy directly from feed (k = 0.72-0.78) (Noblet and 57
Etienne, 1987b; Theil et al., 2004). The efficiency of utilizing body depots (k = 0.86-0.89) and re- 58
taining energy (k = 0.74) in the subsequent gestation period reduces the efficiency to approximately 59
0.65 to sustain MY (Noblet and Etienne, 1987b; Strathe et al., 2012). 60
Lactating sows’ nutrient requirement is today covered by a single diet fed throughout lacta- 61
tion. The 1-diet regime is not able to take into account the changing requirements of Lys, nitrogen 62
(N) and energy (Feyera and Theil, 2014). Sows’ requirement for energy is both determined by 63
maintenance and MY, while the Lys requirement is almost exclusively determined by MY (Theil, 64
2015). An increasing interest in using a dynamic 2-diet regime to cover lactating sows’ requirement 65
has therefore evolved, but experience is still scarce. 66
The objective of the present study was to evaluate whether a new feeding regime composed 67
of two diets throughout lactation could minimize sow weight loss and increase sow MY and piglet 68
weight gain. 69
70
MATERIALS AND METHODS
71The experiment complied with the Danish Ministry of Justice, Act no. 253 of March 8 2013 72
concerning experiments with animals and care of experimental animals, and a license issued by the 73
Danish Animal Experiments Inspectorate. 74
75
Animals and Housing
76 77
A total of 14 cross-bred (Danish Landrace x Yorkshire) second parity sows were included in 78
the experiment from parturition until weaning 28 d later. The experiment was carried out at Aarhus 79
University, Foulum, Denmark in the period from March 2014 to May 2014. Sows and their litter 80
were individually housed in fixed farrowing crates (2.7 x 1.8 meter). Pen floor consists of one half 81
concrete floor and one half iron slatted floor. The temperature was kept around 20ᵒC around farrow- 82
ing and then gradually reduced to 16 ᵒC throughout the experimental period. The piglets were pro- 83
vided with heating lamps in the cave throughout the experimental period and floor heating was 84
turned on the first 14 d after farrowing. Sawdust was provided in the piglet cave before parturition. 85
Until 48 h after farrowing the light was on 24 h and for the rest of the experimental period the light 86
was on from 06-18 and again in connection with feeding from 00.30 to 01.00. 87
88
Diets and Feed Composition
89 90
Two different feeding regimes were supplied; a standard lactation diet (1-diet feeding re- 91
gime) as a control diet or a basal diet and lactation supplement (2-diet feeding regime). The 1-diet 92
group represented the traditional feed composition and feeding strategy in Denmark, where feed 93
allowance increases in early lactation and is kept high in wk 3 and 4. The 2-diet group received a 94
basal supplement (which covered maintenance requirement) and a lactation supplement (covering 95
requirement for milk production). Dietary formulations of the 1-diet, basal diet and lactation sup- 96
plement are shown in Table 1. Feed was provided automatically three times a d at 00.30 and 08.30 97
AM and 04.30 PM. Sows had free access to water. No straw was provided but sows were supplied 98
a rope for stimulation of nursing and rooting behavior. 99
100
Feed Regime Formulation
101 102
The control diet was formulated according to Danish standards and recommendations 103
(Jørgensen and Tybirk, 2010). Sows fed the 2-diet feeding regime received the energy required for 104
maintenance from the basal diet, and Lys and N content in the basal diet was kept low and formu- 105
lated to match the requirement for gestating sows (Theil et al., 2004; NRC, 2012). Lactation sup- 106
plement was formulated to cover the Lys requirement for milk production, and protein was included 107
to obtain the optimal Lys supply based on factorial calculations. And inclusion level of synthetic 108
Lys was the same as in the control diet. The CP content for basal diet and lactation supplement was 109
dictated by the Lys content. The energy content of the basal diet was comparable to that commonly 110
used for gestating sows, whereas the dietary energy in the lactation supplement was comparable to a 111
standard lactation diet. The energy content was elevated in the lactation supplement by addition of 112
soybean oil. The basal diet and lactation supplement was formulated to contain the same amount of 113
barley and wheat. The basal diet was, furthermore, formulated to contain more dietary fibers. 114
Feeding Level. The 1-diet regime sows were fed 3.3 kg from lactation d 1 to 3, from d 4 to
115
10 feed allowance increased by 0.5 kg per day to 6.6 kg. From lactation d 11 - 20 sows’ feed allow- 116
ance increased to 9 kg and it was kept constant until weaning. The feeding level for sows fed the 2- 117
diet feeding regime was based on the individual sow’s energy requirement. The requirement for 118
energy was calculated to ensure optimal supply of energy, and supply of basal diet and lactation 119
supplement together ensured optimal supply of energy and Lys for both the sow and the milk pro- 120
duction. Energy requirement for maintenance was calculated according to 482 kJ/kg0.75 by Theil et 121
al. (2004). Requirement for milk production was calculated based on a forecast of the MY, the pre- 122
dicted energy content of milk (Hansen et al., 2012b), energy associated with milk production (Theil 123
et al., 2004) and corrected for the energy available from uterus regression (Theil, 2015). The re- 124
quirement was initially covered with 70% of requirement on d 2, and it increased by 2% units daily 125
based on the results of Feyera and Theil (2014). 126
127
Experimental Procedure
128 129
Back Fat and BW. The sows were weighed on d 2, 7, 21 and 28 after parturition. Back fat
130
(BF) was measured on d 2, 14 and 28 d after parturition by ultrasound using a 7.5-MHz Linear In- 131
traoperative Probe Aloka (UST-556/7.5, Simonsen & Weel, Vallensbæk Strand, Denmark). The BF 132
was measured 3 times on the right and left side of the sow, 65 mm from the last (12th) backbone 133
(conventionally known as P2 measurement). Sows’ BF is represented as mean values from six 134
measurements. Piglets were weighed individually on d 2, 4, 7, 14, 21 and 28 for forecasting MY 135
during the next week and for determination of MY in the past week. 136
Feces Scoring. Feces were scored every d from farrowing until weaning. The feces were
137
given a score from one to five, score one being dry and pellet-shaped and five being very wet feces, 138
unformed and liquid (Oliviero et al., 2009). 139
Milk Samples. Milk samples from the sows were drawn on d 3, 10, 17 and 24 after farrow-
140
ing for further analyses. Piglets were removed from the sow during milk sampling and the sow was 141
injected 2 mL oxytocin intramuscular to induce milk let down. A total of 45-50 mL milk was drawn 142
from 2 to 3 teats and filtered before storing at -80ᵒC until analysis. 143
Blood Samples. Blood samples were drawn 4 h after morning feeding on d 3 and 17 after
144
parturition. Blood samples were collected (2 x 9 mL) by jugular vein puncture into 10 ml hepa- 145
rinized tubes (Greiner BioOne GmbH, Kremsmünster, Austria) and placed on ice. Blood samples 146
were centrifuged at 3,000 rpm at 4ᵒC for 20 min. Plasma was harvested immediately after centrifu-